An ontology flange and its production method

Abstract

The present invention belongs to the technical field of flange production, and relates to a body flange and a production method thereof. The production method includes: alloy melting, refining and purification, spheroidizing inoculation, casting molding, quenching and tempering heat treatment, nitrocarburizing, sandblasting roughening, and coating cladding. The present invention optimizes the production process of ductile iron materials for body flanges by combining the melting and refining process of raw material mixtures, the ultrasonic-assisted in-package spheroidizing inoculation process, the isothermal heat treatment process, the ultrasonic-assisted casting process, the nitrocarburizing process, and the cladding wear-resistant coating process, developing and producing ductile iron materials with better performance. Using it to produce body flanges can greatly improve the service performance of body flanges at normal temperature, ensure good comprehensive mechanical properties of body flanges, and can well meet the requirements for the strength, toughness, and wear resistance of body flanges under the service environment of high-temperature and high-pressure pipelines.

Description

Technical Field

[0001] The present invention belongs to the technical field of flange production, and relates to a body flange and a production method thereof. Background Art

[0002] A body flange is a disc-shaped part mainly used for pipeline connection. It is fixed at one end of the pipeline. There are holes on the body flange, and bolts pass through the holes to butt and fasten the two flanges, so that the pipelines are connected to each other, and gaskets are used for sealing between the flanges.

[0003] The traditional production processes of body flanges include casting processes and machining. Currently, the body flanges produced by casting processes have the following defects in processing and use:

[0004] (1) The tensile strength of the cast iron material used in casting is lower than that of steel. The internal organizational structure of the cast iron alloy is loose and the airtightness is not high, and it is prone to fracture when the pressure or external force applied is too large; (2) There are defects such as sand holes and air holes inside the body flanges produced by casting processes, and they cannot be used under high-pressure conditions, otherwise there will be a risk of leakage.

[0005] Therefore, in order to solve the above technical problems, it is urgent to improve the existing production processes of body flanges. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a body flange and a production method thereof. The present invention has modified and optimized the production process of ductile iron materials for body flanges, and combined the raw material mixture melting and refining process, ultrasonic-assisted in-package spheroidizing inoculation process, isothermal heat treatment process, ultrasonic-assisted casting process, carbonitriding process, and cladding wear-resistant coating process to develop and produce ductile iron materials with better performance. Using them to produce body flanges can greatly improve the use performance of body flanges at normal temperature, ensure good comprehensive mechanical properties of body flanges, and can well meet the requirements for the strength, toughness, and wear resistance of body flanges in the high-temperature and high-pressure pipeline use environment.

[0007] To achieve this purpose, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a production method of a body flange, and the production method includes:

[0009] S1. Alloy melting: Put the raw material mixture into a melting furnace, melt the raw material mixture to obtain an alloy melt;

[0010] S2. Refining and Purifying: Adjust the temperature of the alloy melt to the refining temperature, then add a purifying agent to the alloy melt, hold at the refining temperature for a period of time, then continuously introduce nitrogen into the melting furnace, and remove the scum on the liquid surface to obtain a refined melt;

[0011] S3. Spheroidizing and Inoculating: Place the spheroidizing agent on one side of the bottom dam of the ladle, compact it after pressing to form a spheroidizing agent layer, evenly sprinkle an inoculant once on the surface of the spheroidizing agent layer, compact it after pressing to form a primary inoculant layer covering the surface of the spheroidizing agent layer, and sequentially stack a perlite layer and an iron plate on the surface of the primary inoculant layer; Pour the refined melt in the melting furnace into the ladle from the side of the bottom dam where the spheroidizing agent layer and the primary inoculant layer are not placed, and add a secondary inoculant during the pouring of the refined melt; After all the refined melt in the melting furnace is poured into the ladle, insert the ultrasonic probe from above the refined melt into the liquid surface of the refined melt, apply ultrasonic waves to the refined melt, and obtain a casting liquid after ultrasonic treatment;

[0012] S4. Casting and Forming: Preheat the mold in advance. When the temperature of the casting liquid reaches the casting temperature, pour the casting liquid in the ladle into the preheated mold, and add a tertiary inoculant during the pouring of the casting liquid; After all the casting liquid is poured into the mold, naturally cool it to the first cooling temperature, then adjust the cooling rate, perform ultrasonic vibration on the cast mold. When the mold cools to the second cooling temperature, stop ultrasonic vibration and hold for a period of time, then naturally cool it to room temperature, and demold to obtain a flange casting;

[0013] S5. Hardening and Tempering Heat Treatment: First, heat the flange casting after casting and forming to the annealing temperature and hold for a period of time, then quickly cool it to the first temperature and hold for a period of time, then slowly cool it to the second temperature, take it out of the furnace and air-cool it to room temperature to complete the annealing treatment; Then, heat the flange casting after annealing treatment to the normalizing temperature and hold for a period of time, then take it out of the furnace and air-cool it to room temperature to complete the normalizing treatment; Then, heat the flange casting after normalizing treatment to the quenching temperature and hold for a period of time. After the holding is completed, cool it in the furnace to the third temperature, then take out the flange casting and immediately bury it in the preheated molten salt. After a period of time, when the surface temperature of the flange casting drops to the fourth temperature, take it out of the molten salt and air-cool it to room temperature to complete the quenching treatment; Finally, heat the flange casting after quenching treatment to the tempering temperature and hold for a period of time, cool it in the furnace and air-cool it to room temperature to complete the tempering treatment to obtain a raw flange;

[0014] S6. Nitrocarburizing: Carbon dioxide is introduced into the reaction furnace, and the green blank of the flange is placed in the reaction furnace. The green blank of the flange is heated to the carburizing temperature and held for a period of time for carburizing treatment. A protective gas is introduced into the reaction furnace to cool down the green blank of the flange. After the green blank of the flange is cooled to the co-permeation temperature, a mixed gas composed of ammonia, nitrogen, and carbon dioxide is introduced into the reaction furnace and held for a period of time to complete the nitrocarburizing treatment, obtaining a rough flange product.

[0015] S7. Sandblasting and roughening: The rough flange product is sandblasted using sandblasting equipment, and then the sandblasted rough flange product is placed in a mixed solvent of anhydrous ethanol and acetone for ultrasonic cleaning. After the cleaning is completed, it is taken out and dried.

[0016] S8. Coating cladding: Anhydrous ethanol and a binder are mixed in proportion to prepare a binder solution, and a cladding material is mixed with the binder solution in proportion to prepare a paste-like cladding slurry. Among them, the cladding material includes nickel-based alloy powder, cerium dioxide, and tungsten carbide. The cladding slurry is evenly coated on the surface of the sandblasted and roughened rough flange product, and after drying, a cladding slurry layer is formed. The cladding slurry layer is subjected to laser cladding by a laser, and after cooling, a cladding layer is formed on the surface of the rough flange product, obtaining the main body flange.

[0017] The present invention optimizes and modifies the production process of ductile iron materials for the main body flange, combines the raw material mixture melting and refining process, ultrasonic-assisted in-package spheroidizing and inoculation process, isothermal heat treatment process, ultrasonic-assisted casting process, carbonitriding process, and cladding wear-resistant coating process, develops and produces ductile iron materials with excellent mechanical properties and wear resistance, and using it to produce the main body flange can greatly improve the service performance of the main body flange at room temperature, and can fully meet the requirements for the strength, toughness, and wear resistance of the main body flange in the high-temperature and high-pressure pipeline use environment.

[0018] The present invention applies ultrasonic treatment during both the spheroidizing and inoculation process and the casting and molding process. Among them, during the spheroidizing and inoculation process, ultrasonic treatment is directly applied to the refined melt by inserting an ultrasonic probe into the refined melt; during the casting and molding process, ultrasonic treatment is indirectly applied to the casting liquid by contacting the mold with an ultrasonic probe. By performing ultrasonic treatment during the spheroidizing and inoculation process, the number of graphite balls increases and the matrix structure is refined; by performing ultrasonic treatment during the casting and molding process, the growth morphology of the graphite balls is uniform, and the roundness rate of the graphite balls is improved. Through the synergistic effect of ultrasonic treatment at different production stages, the comprehensive mechanical properties such as the tensile strength and hardness of the flange casting can be greatly improved.

[0019] The present invention directly performs ultrasonic treatment on the refined molten liquid through an ultrasonic probe during the spheroidization inoculation process. The high ultrasonic energy generates a negative pressure zone in the local micro-region of the refined molten liquid during the propagation process. When the ultrasonic energy exceeds the surface tension of the refined molten liquid, the refined molten liquid is torn apart to generate a large number of small bubbles. As the ultrasonic time passes, the small bubbles gradually accumulate and grow to form large bubbles. When the pressure in the large bubbles reaches the critical point, they will instantly break and split into more small bubbles. The small bubbles after the splitting will continue to accumulate, grow, break and split repeatedly. When the large bubbles break rapidly, instantaneous high pressure will be generated in the large bubbles. At the same time, the refined molten liquid around the large bubbles will also instantly rush into the bubbles, causing the refined molten liquid near the bubbles to produce strong local vibrations. As the small bubbles continue to accumulate, grow, break and split repeatedly, a cyclic cavitation effect is formed. The impact force generated by each bubble break can strongly flush the dendrites, improve the nucleation rate, and is conducive to the formation of equiaxed crystals. At the same time, the spacing of the secondary dendrites is also reduced, so that the carbides are broken, so that the matrix structure of the flange casting can be refined. In addition, the thermal effect of ultrasound causes the temperature of the refined melt near the ultrasonic probe to increase while the cooling rate to decrease. The high-temperature refined melt is conducive to the growth of graphite nodules. Therefore, the present invention significantly increases the number of graphite nodules by ultrasonically treating the refined melt during the spheroidization inoculation process.

[0020] The invention adopts a specially formulated inoculant, and adopts different inoculants in the processes of ladle inoculation, flushing inoculation and casting inoculation to meet the inoculation requirements of different processing stages, so that the processed body flange has higher strength and better wear resistance; during the ladle inoculation, the first inoculant is laid in layers, and the inoculation effect can be improved after the refined solution is flushed into the molten iron ladle; during the inoculation process, ultrasonic vibration is applied to the refined solution, which is beneficial to increase the number of graphite cores and the roundness of graphite balls, thereby improving the strength of the body flange; casting inoculation is performed after the ladle inoculation, so that the inoculation effect can be prolonged.

[0021] The present invention indirectly performs ultrasonic treatment on the casting liquid through an ultrasonic probe during the casting process, and the cooling rate of the casting liquid in the mold is slowed down through the acoustic cavitation effect and thermal effect of the ultrasonic wave, so that the carbon-poor area and the carbon-rich area in the casting liquid can fully diffuse to achieve carbon balance, which is beneficial to reduce the area of ​​the carbon-poor area around the graphite ball. During the cooling and solidification process of the casting liquid, the graphite ball can grow freely in the casting liquid without being constrained and limited by the space of the carbon-poor area. Therefore, the graphite balls in the flange casting finally formed are uniform in size and have a high roundness, which is beneficial to further improve the comprehensive mechanical properties of the flange casting.

[0022] The present invention adopts two-stage cooling in the casting process, which improves the uniformity of the components of the flange casting and is conducive to further improving the comprehensive mechanical properties of the flange casting. When the casting liquid obtained after refining is naturally cooled from the casting temperature to the first cooling temperature, a solid phase begins to be generated in the casting liquid, and the preferential growth of grains begins inside the casting liquid. At this time, adjusting the cooling rate of the mold and performing ultrasonic vibration treatment at the same time can improve the uniformity of the components inside the casting liquid, promote grain refinement, and greatly enhance the fine grain strengthening effect inside the flange casting; when the mold is reduced to the second cooling temperature, the solute inside the flange casting can be fully diffused through long-term heat preservation, reducing the possibility of segregation inside the flange casting, and further enhancing the comprehensive mechanical properties of the flange casting.

[0023] Since the present invention adds nickel, molybdenum, vanadium and other whitening elements to the raw material mixture of the main flange, the whitening elements have the ability to bind carbon atoms during the casting process, which will slow down the diffusion rate of carbon atoms into the graphite balls; and the added nickel element has the function of stabilizing austenite, therefore, the edge of the flange casting obtained after casting has a whitening tendency, and there are a large number of large-sized primary cementites, which leads to the reduction of the comprehensive mechanical properties of the main flange. Therefore, in order to ensure that the main flange has sufficient tensile strength to improve the actual plasticity, obtain high strength and toughness, and at the same time cannot reduce its tensile strength, the present invention heat treats the flange casting to eliminate free cementite as much as possible, and homogenizes the metallographic structure and internal composition of the flange casting. In this way, the mechanical properties of the flange casting are improved.

[0024] The present invention adopts a high-temperature and low-temperature two-stage annealing process to decompose the pearlite in the matrix structure, and transforms the matrix structure composed of ferrite, pearlite, graphite nodules and tiny graphite particles into a matrix structure composed of ferrite, graphite nodules and tiny graphite particles. The two-stage annealing process can change the matrix structure, thereby improving the mechanical properties of the body flange.

[0025] The present invention adopts a gas carbonitriding process, a flange green body is placed in a reaction furnace, a gas medium containing carbon atoms and nitrogen atoms is introduced into the furnace, and during the high-temperature heating process, carbon atoms and nitrogen atoms diffuse on the surface of the flange green body and are absorbed by the surface of the flange green body into the interior, thereby forming a carbonitriding layer with a certain thickness, which can achieve both the carburizing depth and the nitriding hardness, so that many properties of the flange green body, such as toughness, hardness and wear resistance, are significantly improved.

[0026] The present invention forms a cladding layer on the surface of a rough flange after sandblasting and roughening through laser cladding technology. By setting a cladding layer on the surface of the rough flange, the strength and hardness of the surface of the main body flange can be significantly improved, and the wear resistance of the surface of the main body flange can be improved. The cladding layer includes nickel-based alloy powder, cerium dioxide, and tungsten carbide. Through laser cladding technology, the tungsten carbide particles in the cladding layer are dispersed in the nickel-based alloy powder without grain boundary segregation. Therefore, by adding the hard-phase tungsten carbide particles, the high-temperature wear resistance and hardness of the cladding layer can be significantly improved; in addition, due to the high-temperature stability of tungsten carbide, it has little effect on the microstructure and metallographic structure of the cladding layer. Adding cerium dioxide particles can accelerate the dissolution of cerium dioxide particles and promote the improvement of their shape. At the same time, the cerium dioxide particles are dispersed and filled in the nickel-based alloy powder, enabling the laser energy to be smoothly transmitted along the nickel-based alloy powder, thereby accelerating the melting rate of the nickel-based alloy powder, allowing the nickel-based alloy powder to quickly melt, solidify, and crystallize into shape, having a refinement effect on the metallographic structure of the cladding layer, effectively reducing defects such as cracks and pores in the cladding layer, being conducive to forming a cladding layer with a relatively dense metallographic structure morphology, and thus improving the comprehensive mechanical properties of the cladding layer.

[0027] As a preferred technical solution of the present invention, in step S1, based on the mass fraction of the raw material mixture being 100 wt%, it is composed of the following elements with the following mass fractions:

[0028] 3.5 - 3.7 wt% carbon, 2 - 2.5 wt% silicon, 0.3 - 0.6 wt% manganese, 0.1 - 0.2 wt% nickel, 0.3 - 0.4 wt% molybdenum, and 0.2 - 0.5 wt% vanadium, with the balance being iron; wherein, the mass fraction of carbon can be 3.5 wt%, 3.52 wt%, 3.54 wt%, 3.56 wt%, 3.58 wt%, 3.6 wt%, 3.62 wt%, 3.64 wt%, 3.66 wt%, 3.68 wt% or 3.7 wt%; the mass fraction of silicon can be 2.0 wt%, 2.05 wt%, 2.1 wt%, 2.15 wt%, 2.2 wt%, 2.25 wt%, 2.3 wt%, 2.35 wt%, 2.4 wt%, 2.45 wt% or 2.5 wt%; the mass fraction of manganese can be 0.3 wt%, 0.32 wt%, 0.34 wt%, 0.36 wt%, 0.38 wt%, 0.4 wt%, 0.42 wt%, 0.44 wt%, 0.46 wt%, 0.48 wt%, 0.5 wt%, 0.52 wt%, 0.54 wt%, 0.56 wt%, 0.58 wt% or 0.6 wt%; the mass fraction of nickel can be 0.1 wt%, 0.1 wt%, 0.11 wt%, 0.12 wt%, 0.13 wt%, 0.14 wt%, 0.15 wt%, 0.16 wt%, 0.17 wt%, 0.18 wt%, 0.19 wt% or 0.2 wt%; the mass fraction of molybdenum can be 0.3 wt%, 0.31 wt%, 0.32 wt%, 0.33 wt%, 0.34 wt%, 0.35 wt%, 0.36 wt%, 0.37 wt%, 0.38 wt%, 0.39 wt% or 0.4 wt%; the mass fraction of vanadium can be 0.2 wt%, 0.22 wt%, 0.24 wt%, 0.26 wt%, 0.28 wt%, 0.3 wt%, 0.32 wt%, 0.34 wt%, 0.36 wt%, 0.38 wt%, 0.4 wt%, 0.42 wt%, 0.44 wt%, 0.46 wt%, 0.48 wt% or 0.5 wt%, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0029] The present invention particularly limits the carbon content in the raw material mixture to 3.5 - 3.7 wt%. There are three forms of carbon element existing in the matrix structure. One is dissolved into the matrix structure to achieve the solution strengthening effect; the second is to form graphite balls. The higher the carbon content, the more graphite balls precipitate in the matrix structure, and the smaller the diameter size of the graphite balls, which improves the roundness of the graphite balls; the third is to form carbides to achieve the precipitation strengthening effect. Since the formation of graphite balls requires a higher carbon content, the carbon content in the raw material mixture cannot be lower than 3.5 wt%. As the carbon content increases, the number of free cementites decreases, and when the carbon content reaches 3.5 wt%, the cementite disappears. However, when the carbon content exceeds 3.7 wt%, it will cause the floating of graphite balls.

[0030] The present invention particularly limits the silicon content in the raw material mixture to 2 - 2.5 wt%. Silicon can not only effectively reduce the tendency of white mouth, but also has the functions of refining eutectic cells and improving the roundness of graphite balls. However, the silicon element will cause the ductile-brittle transition temperature of the matrix to rise, resulting in a decrease in the tensile strength and hardness of the matrix; in addition, when the silicon content exceeds 2.5 wt%, it will damage the roundness of the graphite balls, resulting in graphite distortion and the generation of fragmented graphite. Therefore, in order to ensure the roundness of the graphite balls in the body flange and at the same time not affect the tensile strength and hardness of the body flange, the present invention particularly limits the silicon content in the raw material mixture to 2 - 2.5 wt%.

[0031] The present invention particularly limits the manganese content in the raw material mixture to 0.3 - 0.6 wt%. As the manganese content increases, the tensile strength of the prepared body flange gradually increases, but the elongation decreases significantly as the manganese content increases. This is because the manganese element can expand the austenite phase region, and manganese atoms can increase the phase transformation resistance to prevent the diffusion rate of iron atoms, so the decomposition rate of austenite is slowed down, and the critical supercooling degree of eutectoid transformation is increased. However, as the manganese content increases, manganese atoms are likely to displace iron atoms in the matrix and form a network of cementite with carbon, thereby reducing the toughness of the matrix and resulting in a decrease in the elongation of the body flange.

[0032] The present invention particularly limits the nickel content in the raw material mixture to 0.1 - 0.2 wt%. Nickel is a graphitizing element and has no effect on the graphite morphology. Therefore, nickel can reduce the tendency of white cast iron. In addition, nickel can dissolve infinitely in the casting liquid and does not form carbides with carbon, having a carbon expelling effect, which is beneficial to improving the toughness of the matrix. At the same time, nickel is also an austenite-forming element, which can reduce the transformation temperature of austenite to ferrite, shift the eutectoid point to the left, and improve the hardenability of the matrix. When the nickel content in the raw material mixture is within the range of 0.1 - 0.2 wt%, with the increase of the nickel content, the hardenability of the matrix increases, and austenite transforms into martensite, resulting in a significant increase in the hardness of the finally prepared body flange. At the same time, there is an appropriate amount of retained austenite, which is beneficial to improving the toughness of the body flange, making the body flange have both high hardness and high toughness. When the nickel content exceeds 0.2 wt%, due to the increase in the content of retained austenite in the cast iron structure, the hardness decreases instead.

[0033] The present invention particularly limits the molybdenum content in the raw material mixture to 0.3 - 0.4 wt% and the vanadium content to 0.2 - 0.5 wt%. Molybdenum and vanadium are white cast iron elements during the solidification process of the casting liquid, which is not conducive to the precipitation of carbon in the form of graphite. A part of molybdenum and vanadium in the casting liquid dissolves into the matrix structure, and a part forms carbides. Since the precipitation temperature and melting point of the carbides of molybdenum and vanadium are relatively high, it can improve the high-temperature stability of the body flange and ensure the high-temperature hardness of the body flange. In addition, molybdenum and vanadium elements can also refine the grain size of the structure, increase the number of graphite balls, reduce the critical cooling rate, improve its hardenability, and slow down the softening trend of the body flange at high temperatures, thereby improving the high-temperature creep resistance of the body flange. However, the contents of molybdenum and vanadium should not be too high. When exceeding the upper limit of the range defined in the present invention, it will cause a decrease in the number of graphite balls precipitated in the matrix structure.

[0034] In some alternative examples, the melting temperature is 1450 - 1460 °C, for example, it can be 1450 °C, 1451 °C, 1452 °C, 1453 °C, 1454 °C, 1455 °C, 1456 °C, 1457 °C, 1458 °C, 1459 °C or 1460 °C, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0035] In some alternative examples, the melting time is 1 - 2 h, for example, it can be 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h or 2.0 h, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0036] As a preferred technical solution of the present invention, in step S2, the refining temperature is 1520 - 1540 °C. For example, it can be 1520 °C, 1522 °C, 1524 °C, 1526 °C, 1528 °C, 1530 °C, 1532 °C, 1534 °C, 1536 °C, 1538 °C or 1400 °C. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0037] In some alternative examples, the mass ratio of the purifying agent to the alloy melt is (0.4 - 0.6):100. For example, it can be 0.4:100, 0.42:100, 0.44:100, 0.46:100, 0.48:100, 0.5:100, 0.52:100, 0.54:100, 0.56:100, 0.58:100 or 0.6:100. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0038] In some alternative examples, it is held at the refining temperature for 50 - 60 min. For example, it can be 50 min, 51 min, 52 min, 53 min, 54 min, 55 min, 56 min, 57 min, 58 min, 59 min or 60 min. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0039] In some alternative examples, the inlet pressure of the nitrogen is 1.5 - 1.8 MPa. For example, it can be 1.5 MPa, 1.52 MPa, 1.54 MPa, 1.56 MPa, 1.58 MPa, 1.6 MPa, 1.62 MPa, 1.64 MPa, 1.66 MPa, 1.68 MPa, 1.7 MPa, 1.72 MPa, 1.74 MPa, 1.76 MPa, 1.78 MPa or 1.8 MPa. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0040] In some alternative examples, the inlet amount of the nitrogen is 100 - 150 Nm 3 / h. For example, it can be 100 Nm 3 / h, 105 Nm 3 / h, 110 Nm 3 / h, 115 Nm 3 / h, 120 Nm 3 / h, 125 Nm 3 / h, 130 Nm 3 / h, 135 Nm 3 / h, 140 Nm 3 / h, 145 Nm 3 / h or 150 Nm 3 / h, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0041] In some alternative examples, the nitrogen introduction time is 10 - 20 min, for example, it can be 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min or 20 min, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0042] As a preferred technical solution of the present invention, in step S3, the mass ratio of the spheroidizing agent to the refining melt is (1.5 - 2.5):100, for example, it can be 1.5:100, 1.6:100, 1.7:100, 1.8:100, 1.9:100, 2.0:100, 2.1:100, 2.2:100, 2.3:100, 2.4:100 or 2.5:100, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0043] The present invention specifically defines that the mass ratio of the spheroidizing agent to the refining melt is (1.5 - 2.5):100. When the addition amount of the spheroidizing agent is lower than the lower limit of the range defined by the present invention, the graphite balls in the obtained cast iron structure will be non-round, with cracks around the periphery, showing a blooming or pointed - angle - like protrusion. The diameter of the graphite balls is relatively large and the number is small. This is because the addition amount of the spheroidizing agent is too small, resulting in insufficient spheroidizing elements, causing severe burning and oxidation of magnesium, resulting in poor spheroidization. When the addition amount of the spheroidizing agent is within the numerical range defined by the present invention, the spheroidizing effect of the prepared body flange is better, the shape of the graphite balls in the structure is more round, the diameter is smaller and the number is larger. This is because the absorption effect of the spheroidizing agent during the spheroidizing treatment is good, the residual amount of magnesium is moderate, and the fine spheroidizing agent particles inhibit the precipitation of cementite, enabling graphite to precipitate instantaneously in large quantities, thus obtaining a large number of graphite balls with small size and uniform distribution, significantly improving the mechanical properties of the body flange. When the addition amount of the spheroidizing agent exceeds the upper limit of the range defined by the present invention, clustered graphite will appear and the graphite distribution is uneven. This is because the addition amount of the spheroidizing agent is too high, resulting in a poor spheroidizing effect. Although adding spheroidizing elements to the refining melt is a basic condition for generating graphite balls, spheroidizing elements have surface activity. When the residual amount of spheroidizing elements is high, it will lead to an increase in the adsorption density of free atoms, blocking some growth steps, causing the graphite morphology to be distorted, resulting in a graphite morphology similar to that when the addition amount of the spheroidizing agent is too low.

[0044] In some alternative examples, based on the mass fraction of the spheroidizing agent being 100 wt%, it is composed of the following elements with the following mass fractions:

[0045] Silicon 40 - 45 wt%, magnesium 7 - 7.5 wt%, manganese 3 - 4 wt%, calcium 2 - 3 wt%, yttrium 1.2 - 1.5 wt%, cerium 0.4 - 0.5 wt%, lanthanum 0.4 - 0.5 wt%, neodymium 0.4 - 0.5 wt%, aluminum 0.1 - 0.5 wt%, and titanium 0.1 - 0.5 wt%, with the balance being iron; among them, the mass fraction of silicon can be 40 wt%, 40.5 wt%, 41 wt%, 41.5 wt%, 42 wt%, 42.5 wt%, 43 wt%, 43.5 wt%, 44 wt%, 44.5 wt% or 45 wt%; the mass fraction of magnesium can be 7.0 wt%, 7.05 wt%, 7.1 wt%, 7.15 wt%, 7.2 wt%, 7.25 wt%, 7.3 wt%, 7.35 wt%, 7.4 wt%, 7.45 wt% or 7.5 wt%; the mass fraction of manganese can be 3.0 wt%, 3.1 wt%, 3.2 wt%, 3.3 wt%, 3.4 wt%, 3.5 wt%, 3.6 wt%, 3.7 wt%, 3.8 wt%, 3.9 wt% or 4.0 wt%; the mass fraction of calcium can be 2.0 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt% or 3.0 wt%; the mass fraction of yttrium can be 1.2 wt%, 1.22 wt%, 1.24 wt%, 1.26 wt%, 1.28 wt%, 1.3 wt%, 1.32 wt%, 1.34 wt%, 1.36 wt%, 1.38 wt%, 1.4 wt%, 1.42 wt%, 1.44 wt%, 1.46 wt%, 1.48 wt% or 1.5 wt%; the mass fraction of cerium can be 0.4 wt%, 0.41 wt%, 0.42 wt%, 0.43 wt%, 0.44 wt%, 0.45 wt%, 0.46 wt%, 0.47 wt%, 0.48 wt%, 0.49 wt% or 0.5 wt%; the mass fraction of lanthanum can be 0.4 wt%, 0.41 wt%, 0.42 wt%, 0.43 wt%, 0.44 wt%, 0.45 wt%, 0.46 wt%, 0.47 wt%, 0.48 wt%, 0.49 wt% or 0.5 wt%; the mass fraction of neodymium can be 0.4 wt%, 0.41 wt%, 0.42 wt%, 0.43 wt%, 0.44 wt%, 0.45 wt%, 0.46 wt%, 0.47 wt%, 0.48 wt%, 0.49 wt% or 0.5 wt%; the mass fraction of aluminum can be 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt% or 0.5 wt%; the mass fraction of titanium can be 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt% or 0.5 wt%, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0046] Magnesium is the main component in the spheroidizing agent. It can spheroidize graphite in the refined solutions with hypoeutectic, eutectic and hypereutectic compositions and has good desulfurization and oxygen absorption capabilities. Rare earth elements such as yttrium, cerium, lanthanum, and neodymium have strong affinity with oxygen, molybdenum, vanadium and other elements that interfere with spheroidization in the refined solution. They can not only purify the refined solution, but also provide certain heterogeneous nuclei, which is beneficial to reducing casting defects such as inclusions and subcutaneous pores. At the same time, the spheroidizing effect of magnesium can be fully exerted, playing a role of spheroidization or indirect spheroidization. However, an excessive residual amount of rare earth elements in the refined solution will lead to the deterioration of graphite morphology and cause graphite distortion. Therefore, the present invention specifically limits the contents of rare earth elements such as yttrium, cerium, lanthanum, and neodymium, and at the same time adds manganese element, calcium element, aluminum element and titanium element. The four elements can play a synergistic role, delay the decomposition of magnesium, control the absorption and reaction rate of the spheroidizing agent, prevent graphite distortion, increase the number of graphite nuclei, extend the spheroidization decay time, promote nucleation, refine the structure, and significantly improve the mechanical properties of the finally prepared body flange.

[0047] In some alternative examples, the particle size D90 of the spheroidizing agent is 10 - 15 mm. For example, it can be 10 mm, 10.5 mm, 11 mm, 11.5 mm, 12 mm, 12.5 mm, 13 mm, 13.5 mm, 14 mm, 14.5 mm or 15 mm, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0048] The present invention uses an improved impouring method for spheroidizing treatment. Since the density of the spheroidizing agent is small, after making it into a powdery spheroidizing agent with a particle size D90 of 10 - 15 mm, it is easy to float during the reaction process. Considering that the powdery spheroidizing agent will burn violently in the refined solution and is easy to be burned out. For this reason, during the spheroidizing process of the present invention, the primary inoculant is covered on the spheroidizing agent, and then perlite and iron plates are laid on the primary inoculant, and then the refined molten liquid is poured into the ladle for spheroidizing treatment. In this way, it can be ensured that when the refined molten liquid is poured in, the powdery spheroidizing agent will not immediately come into contact with the refined solution and react violently, but start to react after a certain amount of the refined solution is poured in, thereby delaying the starting reaction time of the spheroidizing agent and the refined solution and slowing down the reaction rate. At the same time, when the liquid level of the refined solution during the reaction between the refined solution and the spheroidizing agent is relatively high, it also extends the floating time of the spheroidizing agent, enabling the spheroidizing agent to be uniformly and slowly absorbed in the refined solution without quickly floating to the liquid surface of the refined solution and being oxidized and burned out.

[0049] The present invention defines that the particle size D90 of the spheroidizing agent is 10 - 15 mm. The gaps between the powdery spheroidizing agent particles are small, and it is not easy for the refining solution to penetrate between the spheroidizing agent particles. Only when the amount of the refining solution in the ladle is high, the perlite and the iron plate will melt layer by layer, thereby prolonging the initiation time of the spheroidizing agent. In addition, when the amount of the refining solution in the ladle is high, the spheroidizing reaction starts, which prolongs the floating and melting time of the spheroidizing agent in the refining solution, reduces the probability of magnesium escape, and increases the utilization rate of magnesium. Moreover, as the particle size of the spheroidizing agent decreases, the specific surface area of the spheroidizing agent particles increases and the activity enhances. When the spheroidizing agent contacts the refining solution, it will quickly react with the anti-spheroidizing elements such as sulfur and oxygen in the refining solution, shortening the free growth time of graphite balls in the liquid state, causing the spheroidizing elements to be completely consumed during the floating process, and avoiding the phenomenon of the spheroidizing agent floating to the surface of the refining solution and burning out. When the particle size D90 of the spheroidizing agent exceeds 15 mm, the gaps between the spheroidizing agents are large, and the refining solution is easy to penetrate into the gaps between the spheroidizing agents. At this time, once the refining solution is poured into the ladle, the initiation reaction of the spheroidizing agent will occur. At the same time, since the refining solution can quickly enter the gaps between the spheroidizing agents, it is easy to cause some spheroidizing agents to float to the surface of the refining solution and undergo oxidation reaction, resulting in the escape of magnesium and reducing the utilization rate of magnesium.

[0050] In some alternative examples, the primary inoculant is composed of calcium-silicon-barium alloy and silicon carbide. Among them, the mass ratio of the calcium-silicon-barium alloy to the refining melt is (0.2 - 0.3):100, for example, it can be 0.2:100, 0.21:100, 0.22:100, 0.23:100, 0.24:100, 0.25:100, 0.26:100, 0.27:100, 0.28:100, 0.29:100 or 0.3:100; the mass ratio of the silicon carbide to the refining melt is (0.1 - 0.2):100, for example, it can be 0.1:100, 0.11:100, 0.12:100, 0.13:100, 0.14:100, 0.15:100, 0.16:100, 0.17:100, 0.18:100, 0.19:100 or 0.2:100, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0051] In some alternative examples, taking the mass fraction of the calcium-silicon-barium alloy as 100 wt%, it is composed of the following elements with the following mass fractions:

[0052] 40 - 45 wt% silicon, 12 - 15 wt% calcium, 10 - 12 wt% barium, 0.3 - 0.6 wt% zirconium, and 0.15 - 0.3 wt% antimony, with the balance being iron; wherein, the mass fraction of silicon can be 40 wt%, 40.5 wt%, 41 wt%, 41.5 wt%, 42 wt%, 42.5 wt%, 43 wt%, 43.5 wt%, 44 wt%, 44.5 wt% or 45 wt%; the mass fraction of calcium can be 12 wt%, 12.2 wt%, 12.4 wt%, 12.6 wt%, 12.8 wt%, 13 wt%, 13.2 wt%, 13.4 wt%, 13.6 wt%, 13.8 wt%, 14 wt%, 14.2 wt%, 14.4 wt%, 14.6 wt%, 14.8 wt% or 15 wt%; the mass fraction of barium can be 10 wt%, 10.2 wt%, 10.4 wt%, 10.6 wt%, 10.8 wt%, 11 wt%, 11.2 wt%, 11.4 wt%, 11.6 wt%, 11.8 wt% or 12 wt%; the mass fraction of zirconium can be 0.3 wt%, 0.32 wt%, 0.34 wt%, 0.36 wt%, 0.38 wt%, 0.4 wt%, 0.42 wt%, 0.44 wt%, 0.46 wt%, 0.48 wt%, 0.5 wt%, 0.52 wt%, 0.54 wt%, 0.56 wt%, 0.58 wt% or 0.6 wt%; the mass fraction of antimony can be 0.15 wt%, 0.16 wt%, 0.17 wt%, 0.18 wt%, 0.19 wt%, 0.2 wt%, 0.21 wt%, 0.22 wt%, 0.23 wt%, 0.24 wt%, 0.25 wt%, 0.26 wt%, 0.27 wt%, 0.28 wt%, 0.29 wt% or 0.3 wt%, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0053] In some alternative examples, the particle size D90 of the primary inoculant is 8 - 10 mm, for example, it can be 8.0 mm, 8.2 mm, 8.4 mm, 8.6 mm, 8.8 mm, 9.0 mm, 9.2 mm, 9.4 mm, 9.6 mm, 9.8 mm or 10.0 mm, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0054] In some alternative examples, the mass ratio of the secondary inoculant to the refined melt is (0.03 - 0.05):100. For example, it can be 0.03:100, 0.032:100, 0.034:100, 0.036:100, 0.038:100, 0.04:100, 0.042:100, 0.044:100, 0.046:100, 0.048:100 or 0.05:100. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0055] In some alternative examples, based on the mass fraction of the secondary inoculant being 100 wt%, it consists of the following elements with the following mass fractions:

[0056] Silicon 50 - 60 wt%, barium 8 - 15 wt%, calcium 10 - 20 wt%, aluminum 2 - 3 wt%, cerium 6 - 10 wt% and strontium 5 - 9 wt%, with the balance being iron. Among them, the mass fraction of silicon can be 50 wt%, 51 wt%, 52 wt%, 53 wt%, 54 wt%, 55 wt%, 56 wt%, 57 wt%, 58 wt%, 59 wt% or 60 wt%; the mass fraction of barium can be 8.0 wt%, 8.5 wt%, 9.0 wt%, 9.5 wt%, 10.0 wt%, 10.5 wt%, 11.0 wt%, 11.5 wt%, 12.0 wt%, 12.5 wt%, 13.0 wt%, 13.5 wt%, 14.0 wt%, 14.5 wt% or 15.0 wt%; the mass fraction of calcium can be 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt% or 20 wt%; the mass fraction of aluminum can be 2.0 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt% or 3.0 wt%; the mass fraction of cerium can be 6.0 wt%, 6.5 wt%, 7.0 wt%, 7.5 wt%, 8.0 wt%, 8.5 wt%, 9.0 wt%, 9.5 wt% or 10.0 wt%; the mass fraction of strontium can be 5.0 wt%, 5.5 wt%, 6.0 wt%, 6.5 wt%, 7.0 wt%, 7.5 wt%, 8.0 wt%, 8.5 wt% or 9.0 wt%. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0057] In the present invention, elements such as silicon, barium, calcium, aluminum, cerium, and strontium are added to the secondary inoculant. Among them, silicon, calcium, and aluminum will react with oxygen, nitrogen, etc. in the refining solution to form high-melting-point compounds, which become the core of graphite crystallization and can effectively promote the graphitization of carbon. In addition, after adding silicon, calcium, and aluminum, local silicon-rich microregions, calcium-rich microregions, and aluminum-rich microregions will be formed in the refining solution, which is beneficial to the precipitation of graphite. The addition of barium can effectively inhibit the decline of inoculation and ensure the inoculation effect. The addition of rare earth elements such as cerium and strontium can improve the tensile strength of flange castings and inhibit the white-mouthization of flange castings. In addition, the addition of strontium can assist silicon, calcium, and aluminum in the graphitization of the refining solution, inhibit the white-mouthization of flange castings, and has strong graphitization ability.

[0058] In some alternative examples, the particle size D90 of the secondary inoculant is 1 to 3 mm. For example, it can be 1 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm, 2.0 mm, 2.2 mm, 2.4 mm, 2.6 mm, 2.8 mm, or 3.0 mm. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0059] In some alternative examples, the tapping temperature of the refining melt in the melting furnace before it is poured into the ladle is controlled at 1500 to 1520 °C. For example, it can be 1500 °C, 1502 °C, 1504 °C, 1506 °C, 1508 °C, 1510 °C, 1512 °C, 1514 °C, 1516 °C, 1518 °C, or 1520 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0060] In some alternative examples, the ultrasonic probe extends 80 to 100 mm below the liquid level of the refining melt. For example, it can be 80 mm, 82 mm, 84 mm, 86 mm, 88 mm, 90 mm, 92 mm, 94 mm, 96 mm, 98 mm, or 100 mm. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0061] In some alternative examples, the transmission power of the ultrasonic probe is 1000 to 1200 W. For example, it can be 1000 W, 1020 W, 1040 W, 1060 W, 1080 W, 1100 W, 1120 W, 1140 W, 1160 W, 1180 W, or 1200 W. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0062] In some optional instances, the ultrasonic frequency emitted by the ultrasonic probe is 20~30kHz, for example, it can be 20kHz, 21kHz, 22kHz, 23kHz, 24kHz, 25kHz, 26kHz, 27kHz, 28kHz, 29kHz or 30kHz, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0063] In some optional examples, the ultrasonic treatment time is 1 to 3 minutes, for example, it can be 1.0 min, 1.2 min, 1.4 min, 1.6 min, 1.8 min, 2.0 min, 2.2 min, 2.4 min, 2.6 min, 2.8 min or 3.0 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0064] As a preferred technical solution of the present invention, in step S4, the mold is preheated to 500-600°C, for example, it can be 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C or 600°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0065] In some optional instances, the casting temperature is 1380~1400℃, for example, it can be 1380℃, 1382℃, 1384℃, 1386℃, 1388℃, 1390℃, 1392℃, 1394℃, 1396℃, 1398℃ or 1400℃, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0066] In some optional examples, the mass ratio of the tertiary inoculant to the refined melt is (0.1~0.15):100, for example, it can be 0.1:100, 0.105:100, 0.11:100, 0.115:100, 0.12:100, 0.125:100, 0.13:100, 0.135:100, 0.14:100, 0.145:100 or 0.15:100, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0067] In some optional examples, based on the mass fraction of the tertiary inoculant being 100wt%, it is composed of the following elements in mass fraction:

[0068] Silicon 65 - 75 wt%, calcium 10 - 20 wt%, aluminum 2 - 3 wt%, and bismuth 0.01 - 0.015 wt%, with the balance being iron; among them, the mass fraction of silicon can be 65 wt%, 66 wt%, 67 wt%, 68 wt%, 69 wt%, 70 wt%, 71 wt%, 72 wt%, 73 wt%, 74 wt% or 75 wt%; the mass fraction of calcium can be 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt% or 20 wt%; the mass fraction of aluminum can be 2.0 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt% or 3.0 wt%; the mass fraction of bismuth can be 0.01 wt%, 0.0105 wt%, 0.011 wt%, 0.0115 wt%, 0.012 wt%, 0.0125 wt%, 0.013 wt%, 0.0135 wt%, 0.014 wt%, 0.0145 wt% or 0.015 wt%, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0069] In the present invention, bismuth element is added to the three - time inoculant, which is beneficial to improving the roundness of graphite balls, can reduce the diameter of graphite balls, increase the number of graphite balls, and make the distribution of graphite balls more uniform. This is because, on the one hand, during the solidification and crystallization process of the casting liquid, bismuth can adsorb on each crystal plane of the graphite crystal to form interfacial adsorption, reduce the surface free energy of the graphite crystal, inhibit the single growth of the graphite crystal, and make the growth rates of each crystal plane of the graphite crystal tend to be consistent, thus being conducive to the formation of a more round spherical structure. At the same time, since a surrounding layer is formed by bismuth around the graphite crystal, the diffusion of carbon atoms is slowed down, so the diameter of the graphite balls can be reduced. On the other hand, bismuth can play a certain inoculation role, hinder the diffusion of silicon, thereby strengthening the long - term existence of the carbon - rich area, enhancing the concentration fluctuations and energy fluctuations of carbon and silicon in the casting liquid, enabling the graphite crystals in the casting liquid to be maintained, thus increasing the tendency of homogeneous and heterogeneous core formation of graphite, promoting the formation of heterogeneous nucleation of graphite, and reducing the possibility of massive graphite formation. However, excessive bismuth will also hinder graphitization. Therefore, the present invention specifically limits the mass fraction of bismuth to 0.01 - 0.015 wt%.

[0070] In some alternative examples, the particle size D90 of the three - time inoculant is 0.2 - 0.6 mm, for example, it can be 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm or 0.6 mm, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0071] In some alternative examples, the first cooling temperature is 1100 - 1200 °C. For example, it can be 1100 °C, 1110 °C, 1120 °C, 1130 °C, 1140 °C, 1150 °C, 1160 °C, 1170 °C, 1180 °C, 1190 °C or 1200 °C. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0072] In some alternative examples, after natural cooling to the first cooling temperature, the cooling rate is adjusted to 1 - 2 °C / min. For example, it can be 1.0 °C / min, 1.1 °C / min, 1.2 °C / min, 1.3 °C / min, 1.4 °C / min, 1.5 °C / min, 1.6 °C / min, 1.7 °C / min, 1.8 °C / min, 1.9 °C / min or 2.0 °C / min. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0073] In some alternative examples, the ultrasonic power of the ultrasonic vibration is 700 - 800 W. For example, it can be 700 W, 710 W, 720 W, 730 W, 740 W, 750 W, 760 W, 770 W, 780 W, 790 W or 800 W. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0074] In some alternative examples, the ultrasonic frequency of the ultrasonic vibration is 10 - 20 kHz. For example, it can be 10 kHz, 11 kHz, 12 kHz, 13 kHz, 14 kHz, 15 kHz, 16 kHz, 17 kHz, 18 kHz, 19 kHz or 20 kHz. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0075] In some alternative examples, the second cooling temperature is 950 - 1050 °C. For example, it can be 950 °C, 960 °C, 970 °C, 980 °C, 990 °C, 1000 °C, 1010 °C, 1020 °C, 1030 °C, 1040 °C or 1050 °C. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0076] In some alternative examples, it is insulated at the second cooling temperature for 8 - 12 h. For example, it can be 8 h, 8.5 h, 9 h, 9.5 h, 10 h, 10.5 h, 11 h, 11.5 h or 12 h. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0077] As a preferred technical solution of the present invention, in step S5, the flange casting is heated to the annealing temperature at a heating rate of 20~30°C / min. For example, it can be 20°C / min, 21°C / min, 22°C / min, 23°C / min, 24°C / min, 25°C / min, 26°C / min, 27°C / min, 28°C / min, 29°C / min or 30°C / min. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0078] In some alternative examples, the annealing temperature is 1000~1050°C. For example, it can be 1000°C, 1005°C, 1010°C, 1015°C, 1020°C, 1025°C, 1030°C, 1035°C, 1040°C, 1045°C or 1050°C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0079] In some alternative examples, it is held at the annealing temperature for 1.5~2.5 h. For example, it can be 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, 2.0 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h or 2.5 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0080] In some alternative examples, it is cooled from the annealing temperature to the first temperature at a cooling rate of 30~40°C / min. For example, it can be 30°C / min, 31°C / min, 32°C / min, 33°C / min, 34°C / min, 35°C / min, 36°C / min, 37°C / min, 38°C / min, 39°C / min or 40°C / min. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0081] In some alternative examples, the first temperature is 700~750°C. For example, it can be 700°C, 705°C, 710°C, 715°C, 720°C, 725°C, 730°C, 735°C, 740°C, 745°C or 750°C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0082] In some alternative examples, it is held at the first temperature for 30~40 min. For example, it can be 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, 36 min, 37 min, 38 min, 39 min or 40 min. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0083] In some alternative examples, the temperature is decreased from the first temperature to the second temperature at a rate of 10 to 20 °C / min. For example, it can be 10 °C / min, 11 °C / min, 12 °C / min, 13 °C / min, 14 °C / min, 15 °C / min, 16 °C / min, 17 °C / min, 18 °C / min, 19 °C / min or 20 °C / min. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0084] In some alternative examples, the second temperature is 500 to 600 °C. For example, it can be 500 °C, 510 °C, 520 °C, 530 °C, 540 °C, 550 °C, 560 °C, 570 °C, 580 °C, 590 °C or 600 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0085] In some alternative examples, the annealed flange casting is heated to the normalizing temperature at a rate of 8 to 12 °C / min. For example, it can be 8.0 °C / min, 8.5 °C / min, 9.0 °C / min, 9.5 °C / min, 10.0 °C / min, 10.5 °C / min, 11.0 °C / min, 11.5 °C / min or 12.0 °C / min. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0086] In some alternative examples, the normalizing temperature is 880 to 900 °C. For example, it can be 880 °C, 882 °C, 884 °C, 886 °C, 888 °C, 890 °C, 892 °C, 894 °C, 896 °C, 898 °C or 900 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0087] The present invention specifically limits the normalizing temperature to 880 to 900 °C. As the normalizing temperature increases, the spheroidization rate of graphite balls in the body flange decreases and flocculent graphite appears, resulting in non-round graphite morphology. This is because during the cooling process, the saturation of carbon in austenite decreases, leading to the enrichment of carbon atoms in austenite on the surface of graphite balls. However, due to the short cooling time during the normalizing process, the carbon atoms cannot be fully enriched on the surface of graphite balls, thus resulting in the appearance of flocculent graphite morphology. In addition, the pearlite content in the matrix structure increases with the increase of the normalizing temperature. This is because during the heating process, as the normalizing temperature increases, the austenitization degree of the matrix structure rises, and during the cooling process, austenite undergoes eutectoid transformation and decomposes into pearlite structure, thus increasing the pearlite content in the matrix structure. In addition, with the increase of the normalizing temperature, the pearlite lamellar spacing in the matrix structure decreases, which is beneficial to improving the tensile strength of the matrix structure.

[0088] In some optional examples, it is held at the normalizing temperature for 1 to 2 h. For example, it can be 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h or 2.0 h, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0089] In some optional examples, the flange casting after normalizing treatment is heated to the quenching temperature at a heating rate of 5 to 10 °C / min. For example, it can be 5 °C / min, 5.5 °C / min, 6 °C / min, 6.5 °C / min, 7 °C / min, 7.5 °C / min, 8 °C / min, 8.5 °C / min, 9 °C / min, 9.5 °C / min or 10 °C / min, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0090] In some optional examples, the quenching temperature is 840 to 860 °C. For example, it can be 840 °C, 842 °C, 844 °C, 846 °C, 848 °C, 850 °C, 852 °C, 854 °C, 856 °C, 858 °C or 860 °C, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0091] In some optional examples, it is held at the quenching temperature for 20 to 30 min. For example, it can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0092] In some optional examples, the third temperature is 580 to 600 °C. For example, it can be 580 °C, 582 °C, 584 °C, 586 °C, 588 °C, 590 °C, 592 °C, 594 °C, 596 °C, 598 °C or 600 °C, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0093] In some optional examples, the preheating temperature of the molten salt is 280 to 320 °C. For example, it can be 282 °C, 285 °C, 290 °C, 295 °C, 300 °C, 305 °C, 310 °C, 315 °C or 320 °C, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0094] In some alternative examples, the time for the flange casting to be buried in the molten salt is 1 to 2 hours. For example, it can be 1.0 h, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0095] In some alternative examples, the fourth temperature is 260 to 300 °C. For example, it can be 260 °C, 265 °C, 270 °C, 275 °C, 280 °C, 285 °C, 290 °C, 295 °C, or 300 °C, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0096] In some alternative examples, the flange casting after quenching treatment is heated to the tempering temperature at a heating rate of 3 to 5 °C / min. For example, it can be 3.0 °C / min, 3.2 °C / min, 3.4 °C / min, 3.6 °C / min, 3.8 °C / min, 4.0 °C / min, 4.2 °C / min, 4.4 °C / min, 4.6 °C / min, 4.8 °C / min, or 5.0 °C / min, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0097] In some alternative examples, the tempering temperature is 530 to 550 °C. For example, it can be 530 °C, 532 °C, 534 °C, 536 °C, 538 °C, 540 °C, 542 °C, 544 °C, 546 °C, 548 °C, or 550 °C, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0098] In some alternative examples, it is held at the tempering temperature for 3 to 4 hours. For example, it can be 3.0 h, 3.1 h, 3.2 h, 3.3 h, 3.4 h, 3.5 h, 3.6 h, 3.7 h, 3.8 h, 3.9 h, or 4.0 h, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0099] As a preferred technical solution of the present invention, in step S6, the carburizing temperature is 800 to 900 °C. For example, it can be 800 °C, 810 °C, 820 °C, 830 °C, 840 °C, 850 °C, 860 °C, 870 °C, 880 °C, 890 °C, or 900 °C, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0100] In some alternative examples, keep the temperature for carburizing at 0.5 - 1.5 h, for example, it can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h or 1.5 h, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0101] In some alternative examples, the co-cementation temperature is 500 - 600 °C, for example, it can be 500 °C, 510 °C, 520 °C, 530 °C, 540 °C, 550 °C, 560 °C, 570 °C, 580 °C, 590 °C or 600 °C, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0102] In some alternative examples, the mixed gas is composed of ammonia, nitrogen and carbon dioxide.

[0103] In some alternative examples, based on the total volume fraction of the mixed gas being 100%, among which, the volume fraction of ammonia is 30 - 40%, for example, it can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39% or 40%; the volume fraction of carbon dioxide is 5 - 8%, and the balance is nitrogen, for example, it can be 5.0%, 5.2%, 5.4%, 5.6%, 5.8%, 6.0%, 6.2%, 6.4%, 6.6%, 6.8%, 7.0%, 7.2%, 7.4%, 7.6%, 7.8% or 8.0%, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0104] In some alternative examples, the flow rate of the mixed gas is 1000 - 1500 L / h, for example, it can be 1000 L / h, 1050 L / h, 1100 L / h, 1150 L / h, 1200 L / h, 1250 L / h, 1300 L / h, 1350 L / h, 1400 L / h, 1450 L / h or 1500 L / h, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0105] In some alternative examples, keep the temperature at the co-cementation temperature for 5 - 8 h, for example, it can be 5.0 h, 5.2 h, 5.4 h, 5.6 h, 5.8 h, 6.0 h, 6.2 h, 6.4 h, 6.6 h, 6.8 h, 7.0 h, 7.2 h, 7.4 h, 7.6 h, 7.8 h or 8.0 h, but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0106] In some alternative examples, the depth of the nitrocarburizing is 10 - 20 μm. For example, it can be 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm or 20 μm. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0107] As a preferred technical solution of the present invention, in step S7, the abrasive blasting medium used for the abrasive blasting treatment is brown fused alumina sand.

[0108] In some alternative examples, the particle size D90 of the abrasive blasting medium is 400 - 500 μm. For example, it can be 400 μm, 410 μm, 420 μm, 430 μm, 440 μm, 450 μm, 460 μm, 470 μm, 480 μm, 490 μm or 500 μm. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0109] In some alternative examples, the abrasive blasting pressure of the abrasive blasting treatment is 0.6 - 0.8 MPa. For example, it can be 0.6 MPa, 0.62 MPa, 0.64 MPa, 0.68 MPa, 0.7 MPa, 0.72 MPa, 0.74 MPa, 0.76 MPa, 0.78 MPa or 0.8 MPa. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0110] In some alternative examples, the vertical distance between the nozzle and the surface of the rough flange during the abrasive blasting treatment is 150 - 250 mm. For example, it can be 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, 200 mm, 210 mm, 220 mm, 230 mm, 240 mm or 250 mm. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0111] In some alternative examples, the angle between the axis of the nozzle and the surface of the rough flange during the abrasive blasting treatment is 20 - 30°. For example, it can be 20°, 21°, 22°, 23°, 24°, 25°, 26°, 27°, 28°, 29° or 30°. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0112] In some alternative examples, the surface roughness of the rough flange formed after sandblasting is 50 - 60 μm. For example, it can be 50 μm, 51 μm, 52 μm, 53 μm, 54 μm, 55 μm, 56 μm, 57 μm, 58 μm, 59 μm or 60 μm. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0113] As a preferred technical solution of the present invention, in step S8, the mass ratio of the absolute ethanol to the binder is (10 - 20):1. For example, it can be 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1 or 20:1. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0114] In some alternative examples, the ratio of the cladding material to the binder solution is 1 g:(0.2 - 0.3) mL. For example, it can be 1 g:0.2 mL, 1 g:0.21 mL, 1 g:0.22 mL, 1 g:0.23 mL, 1 g:0.24 mL, 1 g:0.25 mL, 1 g:0.26 mL, 1 g:0.27 mL, 1 g:0.28 mL, 1 g:0.29 mL or 1 g:0.3 mL. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0115] In some alternative examples, based on the mass fraction of the cladding material being 100 wt%, it is composed of the following components with the following mass fractions:

[0116] Cerium dioxide 0.5 - 1 wt%;

[0117] Tungsten carbide 30 - 40 wt%;

[0118] The balance is nickel-based alloy powder.

[0119] Among them, the mass fraction of cerium dioxide can be 0.5 wt%, 0.55 wt%, 0.6 wt%, 0.65 wt%, 0.7 wt%, 0.75 wt%, 0.8 wt%, 0.85 wt%, 0.9 wt%, 0.95 wt% or 1 wt%, and the mass fraction of tungsten carbide can be 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt% or 40 wt%. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0120] The present invention specifically limits the addition amount of cerium dioxide to 0.5 - 1 wt%. As the addition amount of cerium dioxide increases, the number of tungsten carbide particles in the cladding layer decreases, and the number of tungsten carbide particles at the edge of the cladding layer also decreases. The tungsten carbide particles are mainly concentrated in the middle of the cladding layer and in the area close to the rough flange. When the addition amount of cerium dioxide is less than 0.5 wt%, the tungsten carbide particles in the cladding layer are in a dispersed distribution state. Since the thickness of the edge where the cladding layer meets the rough flange is relatively thin and the heat dissipation is fast, the tungsten carbide particles aggregate at the edge of the cladding layer. When the addition amount of cerium dioxide reaches 0.5 wt%, the overall number of tungsten carbide particles decreases, and the number of tungsten carbide particles at the edge of the cladding layer also decreases. In addition, as the addition amount of cerium dioxide increases, the size of the tungsten carbide particles in the cladding layer also significantly decreases. This is because cerium dioxide is prone to segregate at grain boundaries or phase boundaries, reducing the melting point of the alloy system. Thus, the cerium dioxide segregated on the interface of the tungsten carbide particles accelerates the melting of the tungsten carbide particles, accelerating the refinement of the cladding layer structure, forming fine granular and fine rod-shaped dendrites, and the dendrites are evenly distributed in the cladding layer, making the organizational structure of the cladding layer more dense. In addition, after adding cerium dioxide, the number of pores in the cladding layer significantly decreases, and the occurrence of cracks is also improved.

[0121] In some alternative examples, based on the mass fraction of the nickel-based alloy powder being 100 wt%, it is composed of the following elements with the following mass fractions:

[0122] Chromium 15 - 20 wt%, iron 4 - 6 wt%, silicon 3 - 5 wt%, boron 3 - 4 wt%, and carbon 0.5 - 1 wt%, with the balance being nickel;

[0123] Among them, the mass fraction of chromium can be 15wt%, 15.5wt%, 16wt%, 16.5wt%, 17wt%, 17.5wt%, 18wt%, 18.5wt%, 19wt%, 19.5wt% or 20wt%; the mass fraction of iron can be 4.0wt%, 4.2wt%, 4.4wt%, 4.6wt%, 4.8wt%, 5.0wt%, 5.2wt%, 5.4wt%, 5.6wt%, 5.8wt% or 6.0wt%; the mass fraction of silicon can be 3.0wt%, 3.2wt%, 3.4wt%, 3.6wt%, 3.8wt%, 4.0wt%, 4.2wt%, 4.4wt%, 4.6wt%, 4.8wt% or 5.0wt%; the mass fraction of boron can be 3.0wt%, 3.1wt%, 3.2wt%, 3.3wt%, 3.4wt%, 3.5wt%, 3.6wt%, 3.7wt%, 3.8wt%, 3.9wt% or 4.0wt%; the mass fraction of carbon can be 0.5wt%, 0.55wt%, 0.6wt%, 0.65wt%, 0.7wt%, 0.75wt%, 0.8wt%, 0.85wt%, 0.9wt%, 0.95wt% or 1wt%, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0124] In some alternative examples, the laser spot diameter used in the laser cladding process is 3 - 4mm, for example, it can be 3.0mm, 3.1mm, 3.2mm, 3.3mm, 3.4mm, 3.5mm, 3.6mm, 3.7mm, 3.8mm, 3.9mm or 4.0mm, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0125] In some alternative examples, the laser power used in the laser cladding process is 1000 - 1200W, for example, it can be 1000W, 1020W, 1040W, 1060W, 1080W, 1100W, 1120W, 1140W, 1160W, 1180W or 1200W, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0126] The present invention specifically limits the laser power used in the laser cladding process to 1000 - 1200W. The structure of the cladding layer shows a gradually coarser trend with the increase of the laser power. When the laser power exceeds 1200W, the energy obtained by the molten pool is too high, and the cooling rate of the molten pool is too low, resulting in a decrease in the supercooling degree of the molten pool and the nucleation rate in the molten pool during crystallization, and the dendritic structure will become coarser, thus affecting the mechanical properties and wear resistance of the cladding layer.

[0127] In some alternative examples, the laser scanning speed used in the laser cladding process is 2 to 4 mm / s. For example, it can be 2.0 mm / s, 2.2 mm / s, 2.4 mm / s, 2.6 mm / s, 2.8 mm / s, 3.0 mm / s, 3.2 mm / s, 3.4 mm / s, 3.6 mm / s, 3.8 mm / s, or 4.0 mm / s. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0128] The present invention specifically defines the laser scanning speed used in the laser cladding process as 2 to 4 mm / s. As the scanning speed increases, the energy obtained by the cladding slurry layer during laser cladding decreases, the cooling rate of the molten pool increases, the supercooling degree during crystallization increases, the nucleation rate rises, the number of crystal nuclei in the molten pool increases, making the dendrites tend to be fine, and the structure of the cladding layer is refined. In addition, as the scanning speed increases, the average wear volume of the cladding layer gradually decreases, and the average wear rate of the cladding layer gradually decreases, which helps to improve the wear resistance of the cladding layer.

[0129] In some alternative examples, the thickness of the cladding layer is 0.5 to 1.5 mm. For example, it can be 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, or 1.5 mm. However, it is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0130] In a second aspect, the present invention provides a body flange prepared by the production method according to the first aspect.

[0131] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0132] The present invention optimizes and modifies the production process of ductile iron materials for body flanges, combines the raw material mixture melting and refining process, ultrasonic-assisted in-package spheroidization and inoculation process, isothermal heat treatment process, ultrasonic-assisted casting process, carbonitriding process, and cladding wear-resistant coating process, develops and produces ductile iron materials with excellent mechanical properties and wear resistance, and using it to produce body flanges can greatly improve the service performance of body flanges at room temperature, and can fully meet the requirements for the strength, toughness, and wear performance of body flanges in high-temperature and high-pressure pipeline use environments.

[0133] In the present invention, ultrasonic treatment is applied during both the spheroidizing inoculation and casting forming processes. Specifically, during the spheroidizing inoculation process, the ultrasonic probe is inserted into the refining melt to directly perform ultrasonic treatment on the refining melt. During the casting forming process, the ultrasonic probe contacts the mold to indirectly perform ultrasonic treatment on the casting liquid. By performing ultrasonic treatment during the spheroidizing inoculation process, the number of graphite balls increases and the matrix structure is refined. By performing ultrasonic treatment during the casting forming process, the growth morphology of the graphite balls becomes uniform, and the roundness rate of the graphite balls is improved. Through the synergistic effect of ultrasonic treatment at different production stages, the comprehensive mechanical properties such as the tensile strength and hardness of the flange casting can be greatly improved.

[0134] In the present invention, during the spheroidizing inoculation process, the ultrasonic probe directly performs ultrasonic treatment on the refining melt. The high ultrasonic energy generates a negative pressure zone in a local micro-region of the refining melt during propagation. When the ultrasonic energy exceeds the surface tension of the refining melt, the refining melt is torn apart to generate a large number of small bubbles. As the ultrasonic time progresses, the small bubbles gradually accumulate and grow into large bubbles. When the pressure inside the large bubble reaches the critical point, it will instantaneously break and split into more small bubbles, and the split small bubbles continuously repeat the processes of accumulation growth and fragmentation. When the large bubble rapidly breaks, an instantaneous high pressure is generated inside the large bubble. At the same time, the refining melt around the large bubble will instantaneously rush into the bubble interior, causing strong local vibration of the refining melt near the bubble. With the continuous repetition of the processes of accumulation growth and fragmentation of the small bubbles, a cyclic cavitation effect is formed. The impact force generated by each bubble break can strongly scour the dendrites, increasing the nucleation rate, facilitating the formation of equiaxed crystals, and at the same time reducing the secondary dendrite arm spacing, causing the carbides to break, so it can refine the matrix structure of the flange casting. In addition, the thermal effect of ultrasound causes the temperature of the refining melt near the ultrasonic probe to increase while the cooling rate decreases. The high-temperature refining melt is beneficial to the growth of graphite balls. Therefore, by performing ultrasonic treatment on the refining melt during the spheroidizing inoculation process, the present invention significantly increases the number of graphite balls.

[0135] The present invention uses a specially formulated inoculant and different inoculants are used during in-package inoculation, in-stream inoculation, and casting inoculation processes to meet the inoculation requirements at different treatment stages, resulting in a higher-strength and better-wear-resistant body flange. During in-package inoculation, the first inoculant is laid in layers, which can improve the inoculation effect after the refining solution is poured into the ladle. During the inoculation process, ultrasonic vibration is applied to the refining solution, which is beneficial to increasing the number of graphite nuclei and improving the roundness of graphite balls, thereby enhancing the strength of the body flange. After in-package inoculation, casting inoculation is carried out, which can extend the inoculation effect.

[0136] The present invention indirectly performs ultrasonic treatment on the casting liquid through an ultrasonic probe during the casting process, and the cooling rate of the casting liquid in the mold is slowed down through the acoustic cavitation effect and thermal effect of the ultrasonic wave, so that the carbon-poor area and the carbon-rich area in the casting liquid can fully diffuse to achieve carbon balance, which is beneficial to reduce the area of ​​the carbon-poor area around the graphite ball. During the cooling and solidification process of the casting liquid, the graphite ball can grow freely in the casting liquid without being constrained and limited by the space of the carbon-poor area. Therefore, the graphite balls in the flange casting finally formed are uniform in size and have a high roundness, which is beneficial to further improve the comprehensive mechanical properties of the flange casting.

[0137] The present invention adopts two-stage cooling in the casting process, which improves the uniformity of the components of the flange casting and is conducive to further improving the comprehensive mechanical properties of the flange casting. When the casting liquid obtained after refining is naturally cooled from the casting temperature to the first cooling temperature, a solid phase begins to be generated in the casting liquid, and the preferential growth of grains begins inside the casting liquid. At this time, adjusting the cooling rate of the mold and performing ultrasonic vibration treatment at the same time can improve the uniformity of the components inside the casting liquid, promote grain refinement, and greatly enhance the fine grain strengthening effect inside the flange casting; when the mold is reduced to the second cooling temperature, the solute inside the flange casting can be fully diffused through long-term heat preservation, reducing the possibility of segregation inside the flange casting, and further enhancing the comprehensive mechanical properties of the flange casting.

[0138] Since the present invention adds nickel, molybdenum, vanadium and other whitening elements to the raw material mixture of the main flange, the whitening elements have the ability to bind carbon atoms during the casting process, which will slow down the diffusion rate of carbon atoms into the graphite balls; and the added nickel element has the function of stabilizing austenite, therefore, the edge of the flange casting obtained after casting has a whitening tendency, and there are a large number of large-sized primary cementites, which leads to the reduction of the comprehensive mechanical properties of the main flange. Therefore, in order to ensure that the main flange has sufficient tensile strength to improve the actual plasticity, obtain high strength and toughness, and at the same time cannot reduce its tensile strength, the present invention heat treats the flange casting to eliminate free cementite as much as possible, and homogenizes the metallographic structure and internal composition of the flange casting. In this way, the mechanical properties of the flange casting are improved.

[0139] The present invention adopts a high-temperature and low-temperature two-stage annealing process to decompose the pearlite in the matrix structure, and transforms the matrix structure composed of ferrite, pearlite, graphite nodules and tiny graphite particles into a matrix structure composed of ferrite, graphite nodules and tiny graphite particles. The two-stage annealing process can change the matrix structure, thereby improving the mechanical properties of the body flange.

[0140] The present invention adopts a gas carbonitriding process. The green blank of the flange is put into a reaction furnace, and a gas medium containing carbon atoms and nitrogen atoms is introduced into the furnace. During the high-temperature heating process, the carbon atoms and nitrogen atoms diffuse on the surface of the green blank of the flange and are absorbed by the surface of the green blank of the flange and enter the interior, thereby forming a carbonitriding layer with a certain thickness, which can not only achieve the depth of carburization but also reach the hardness of nitriding, so that many properties such as the toughness, hardness, and wear resistance of the green blank of the flange are significantly improved.

[0141] The present invention forms a cladding layer on the surface of the rough flange after sandblasting and roughening through laser cladding technology. By setting a cladding layer on the surface of the rough flange, the strength and hardness of the surface of the main body flange can be significantly improved, and the wear resistance of the surface of the main body flange can be improved. The cladding layer includes nickel-based alloy powder, cerium dioxide, and tungsten carbide. Through laser cladding technology, the tungsten carbide particles in the cladding layer are dispersed in the nickel-based alloy powder and there will be no grain boundary segregation phenomenon. Therefore, by adding the hard phase of tungsten carbide particles, the high-temperature wear resistance and hardness of the cladding layer can be significantly improved; in addition, due to the high-temperature stability of tungsten carbide, it has little influence on the microstructure and metallographic structure of the cladding layer. Adding cerium dioxide particles can accelerate the dissolution of cerium dioxide particles and promote the improvement of their shape. At the same time, the cerium dioxide particles are dispersed and filled in the nickel-based alloy powder, so that the laser energy can be smoothly transmitted along the nickel-based alloy powder, thereby accelerating the melting rate of the nickel-based alloy powder, enabling the nickel-based alloy powder to be quickly melted, solidified, and crystallized into shape, producing a refinement effect on the metallographic structure of the cladding layer, effectively reducing defects such as cracks and pores in the cladding layer, facilitating the formation of a cladding layer with a relatively dense metallographic structure morphology, and thus improving the comprehensive mechanical properties of the cladding layer. Brief Description of the Drawings

[0142] Figure 1 It is the production process flow chart of the main body flange provided in Embodiment 11 of the present invention;

[0143] Figure 2 It is the matrix metallographic micrograph of the green blank of the flange prepared in Embodiment 1 of the present invention;

[0144] Figure 3 It is the graphite metallographic micrograph of the green blank of the flange prepared in Embodiment 1 of the present invention;

[0145] Figure 4 It is the matrix metallographic micrograph of the green blank of the flange prepared in Comparative Example 1 of the present invention;

[0146] Figure 5 It is the graphite metallographic micrograph of the green blank of the flange prepared in Comparative Example 1 of the present invention;

[0147] Figure 6 It is the matrix metallographic micrograph of the green blank of the flange prepared in Comparative Example 2 of the present invention;

[0148] Figure 7 It is the graphite metallographic micrograph of the blank flange prepared in Comparative Example 2 of the present invention;

[0149] Figure 8 It is the matrix metallographic micrograph of the blank flange prepared in Comparative Example 3 of the present invention;

[0150] Figure 9 It is the graphite metallographic micrograph of the blank flange prepared in Comparative Example 3 of the present invention;

[0151] Figure 10 It is the optical micrograph of the cladding layer on the surface of the main body flange prepared in Example 1 of the present invention;

[0152] Figure 11 It is the optical micrograph of the cladding layer on the surface of the main body flange prepared in Comparative Example 4 of the present invention. Specific Embodiments

[0153] The technical solution of the present invention will be described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments described herein are specific specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are all explanatory and exemplary and should not be construed as limiting the embodiments of the present invention and the protection scope of the present invention. Except for the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims of this application and its specification, and these technical solutions include technical solutions that make any obvious substitutions and modifications to the embodiments described herein.

[0154] Example 1

[0155] This example provides a production method for a main body flange, as Figure 1 shown, the production method specifically includes the following steps:

[0156] S1. Alloy melting: Put the raw material mixture into a melting furnace, heat the raw material mixture to 1450 °C and keep it warm for 2 h to obtain an alloy melt;

[0157] Calculated based on the mass fraction of the raw material mixture being 100 wt%, it is composed of the following elements with the following mass fractions: carbon 3.5 wt%, silicon 2.5 wt%, manganese 0.3 wt%, nickel 0.2 wt%, molybdenum 0.3 wt%, and vanadium 0.5 wt%, and the balance is iron;

[0158] S2. Refining and Purifying: Adjust the temperature of the alloy melt to 1520 °C, add a purifying agent to the alloy melt. The purifying agent is composed of calcium oxide and aluminum oxide with a mass ratio of 1:1, and the mass ratio of the purifying agent to the alloy melt is 0.4:100. Keep it warm for 60 min to complete refining and purifying; then continuously introduce nitrogen at 1.5 MPa into the smelting furnace. The input amount of nitrogen is 100 Nm 3 / h, and the input time is 20 min. After removing the scum on the liquid surface, the refined melt is obtained;

[0159] S3. Spheroidizing and Inoculating: Place the spheroidizing agent with a D90 particle size of 10 mm on one side of the bottom dam of the ladle, and compact it to form a spheroidizing agent layer after tamping; among them, the mass ratio of the spheroidizing agent to the refined melt is 1.5:100; calculated with the mass fraction of the spheroidizing agent being 100 wt%, it consists of the following elements with the following mass fractions: silicon 40 wt%, magnesium 7.5 wt%, manganese 4 wt%, calcium 2 wt%, yttrium 1.2 wt%, cerium 0.4 wt%, lanthanum 0.5 wt%, neodymium 0.4 wt%, aluminum 0.1 wt%, and titanium 0.5 wt%, and the balance is iron;

[0160] Uniformly sprinkle a primary inoculant composed of calcium-silicon-barium alloy and silicon carbide on the surface of the spheroidizing agent layer, and compact it to form a primary inoculant layer covering the surface of the spheroidizing agent layer; among them, the D90 particle sizes of both the calcium-silicon-barium alloy and silicon carbide are 8 mm, the mass ratio of the calcium-silicon-barium alloy to the refined melt is 0.2:100, and the mass ratio of silicon carbide to the refined melt is 0.2:100; calculated with the mass fraction of the calcium-silicon-barium alloy being 100 wt%, it consists of the following elements with the following mass fractions: silicon 40 wt%, calcium 15 wt%, barium 12 wt%, zirconium 0.3 wt%, and antimony 0.3 wt%, and the balance is iron;

[0161] Stack perlite and iron plates on the surface of the primary inoculant layer in sequence. Control the tapping temperature of the refined melt in the smelting furnace at 1500 °C, and then pour the refined melt into the ladle from the side of the bottom dam where the spheroidizing agent layer and the primary inoculant layer are not placed; during the process of pouring the refined melt, add a secondary inoculant with a D90 particle size of 1 mm with the flow. The mass ratio of the secondary inoculant to the refined melt is 0.03:100; calculated with the mass fraction of the secondary inoculant being 100 wt%, it consists of the following elements with the following mass fractions: silicon 50 wt%, barium 15 wt%, calcium 10 wt%, aluminum 2 wt%, cerium 10 wt%, and strontium 5 wt%, and the balance is iron;

[0162] After all the refined melt in the smelting furnace is poured into the ladle, insert the ultrasonic probe from above the refined melt to 80 mm below the liquid surface of the refined melt, apply 1000 W of ultrasonic waves to the refined melt, the ultrasonic frequency is 20 kHz, and the ultrasonic treatment time is 3 min. After ultrasonic treatment, the casting liquid is obtained;

[0163] S4. Casting and Molding: Preheat the mold to 500 °C in advance. When the temperature of the casting liquid reaches 1380 °C, pour the casting liquid in the ladle into the preheated mold. During the pouring process of the casting liquid, add the third inoculant with a particle size D90 of 0.2 mm along with the flow. The mass ratio of the third inoculant to the refined melt is 0.1:100;

[0164] Taking the mass fraction of the third inoculant as 100 wt%, it consists of the following elements with the following mass fractions: silicon 65 wt%, calcium 20 wt%, aluminum 2 wt%, and bismuth 0.01 wt%, and the balance is iron;

[0165] After all the casting liquid is poured into the mold, let it cool naturally to 1100 °C, then adjust the cooling rate to 1 °C / min, and perform ultrasonic vibration on the cast mold. The ultrasonic power used is 700 W, and the ultrasonic frequency is 10 kHz; When the mold cools to 950 °C, stop the ultrasonic vibration and keep it warm for 12 h, then let it cool naturally to room temperature, and demold to obtain the flange casting;

[0166] S5. Quenching and Tempering Heat Treatment: Perform annealing treatment, normalizing treatment, quenching treatment, and tempering treatment on the flange casting after casting and molding in sequence;

[0167] First, heat the flange casting after casting and molding to 1000 °C at a heating rate of 20 °C / min and keep it warm for 2.5 h, then quickly cool it to 700 °C at a cooling rate of 30 °C / min and keep it warm for 40 min, and then slowly cool it to 500 °C at a cooling rate of 10 °C / min, take it out of the furnace and air-cool it to room temperature to complete the annealing treatment;

[0168] Then, heat the flange casting after annealing treatment to 880 °C at a heating rate of 8 °C / min and keep it warm for 2 h, then take it out of the furnace and air-cool it to room temperature to complete the normalizing treatment;

[0169] Then, heat the flange casting after normalizing treatment to 840 °C at a heating rate of 5 °C / min and keep it warm for 30 min. After the heat preservation ends, cool it in the furnace to 580 °C, then take out the flange casting and immediately bury it in the molten salt at 280 °C, keep it warm in the molten salt for 2 h, and when the surface temperature of the flange casting drops to 260 °C, take out the flange casting from the molten salt and air-cool it to room temperature to complete the quenching treatment;

[0170] Finally, heat the flange casting after quenching treatment to 530 °C at a heating rate of 3 °C / min and keep it warm for 4 h, and air-cool it in the furnace to room temperature to complete the tempering treatment to obtain the flange green blank;

[0171] S6, Nitrocarburizing: Carbon dioxide is introduced into the reaction furnace, and the green blank of the flange is placed in the reaction furnace. The green blank of the flange is heated to 800 °C and held for 1.5 h for carburizing treatment. Argon is introduced into the reaction furnace to cool down the green blank of the flange. After the green blank of the flange cools down to 500 °C, a mixed gas composed of ammonia, nitrogen, and carbon dioxide is introduced into the reaction furnace, and the flow rate of the mixed gas is 1000 L / h. Taking the total volume fraction of the mixed gas as 100%, among which, the volume fraction of ammonia is 30%, the volume fraction of carbon dioxide is 5%, and the balance is nitrogen. After holding for 5 h, the nitrocarburizing treatment is completed, and the depth of nitrocarburizing is 10 μm, obtaining a rough flange product.

[0172] S7, Sandblasting roughening: The rough flange product is sandblasted with brown fused alumina sand with a D90 particle size of 400 μm. The sandblasting pressure is 0.6 MPa, the vertical distance between the nozzle and the surface of the rough flange product is 150 mm, and the angle between the axis of the nozzle and the surface of the rough flange product is 20°. The surface roughness of the rough flange product formed after sandblasting is 50 μm. Subsequently, the sandblasted rough flange product is placed in a mixed solvent of absolute ethanol and acetone for ultrasonic cleaning, and then taken out and dried after cleaning.

[0173] S8, Coating cladding: Absolute ethanol and a binder are mixed in a mass ratio of 10:1 to prepare a binder solution, and the cladding material and the binder solution are mixed in a ratio of 1 g:0.2 mL to prepare a paste-like cladding slurry.

[0174] Taking the mass fraction of the cladding material as 100 wt%, it is composed of the following components with the following mass fractions: cerium dioxide 0.5 wt%, tungsten carbide 30 wt%, and the balance is nickel-based alloy powder.

[0175] Taking the mass fraction of the nickel-based alloy powder as 100 wt%, it is composed of the following elements with the following mass fractions: chromium 15 wt%, iron 6 wt%, silicon 3 wt%, boron 4 wt%, and carbon 0.5 wt%, and the balance is nickel.

[0176] The cladding slurry is evenly coated on the surface of the sandblasted rough flange product, and after drying, a cladding slurry layer is formed. The cladding slurry layer is subjected to laser cladding by a laser. The process parameters of laser cladding are: the laser spot diameter is 3 mm, the laser power is 1000 W, the laser scanning speed is 2 mm / s. After cooling, a cladding layer with a thickness of 0.5 mm is formed on the surface of the rough flange product, obtaining the said body flange.

[0177] The graphite metallographic structure and the matrix metallographic structure of the green blank of the flange prepared in this example are observed by a metallographic microscope, and the metallographic micrographs as shown in Figure 1 and Figure 2 are obtained. It can be seen from the figure that the number of graphite balls in the green blank of the flange is large and the size is small.

[0178] The cladding layer on the surface of the body flange prepared in this embodiment was observed using an optical microscope, and the optical micrograph shown in Figure 10 was obtained. It can be seen from the figure that there are almost no defects such as cracks and pores in the cladding layer.

[0179] Example 2

[0180] This embodiment provides a production method for a body flange. As Figure 1 shown, the production method specifically includes the following steps:

[0181] S1. Alloy melting: The raw material mixture is put into a melting furnace, heated to 1452 °C and kept warm for 1.8 h to obtain an alloy melt;

[0182] Based on the mass fraction of the raw material mixture being 100 wt%, it consists of the following elements with the following mass fractions: carbon 3.55 wt%, silicon 2.3 wt%, manganese 0.4 wt%, nickel 0.18 wt%, molybdenum 0.32 wt%, and vanadium 0.4 wt%, and the balance is iron;

[0183] S2. Refining and purification: The temperature of the alloy melt is adjusted to 1525 °C, and a purifying agent is added to the alloy melt. The purifying agent consists of calcium oxide and aluminum oxide with a mass ratio of 1:1, and the mass ratio of the purifying agent to the alloy melt is 0.45:100. Keep warm for 58 min to complete refining and purification; then continuously introduce nitrogen at 1.6 MPa into the melting furnace. The input amount of nitrogen is 110 Nm 3 / h, and the introduction time is 18 min. After removing the scum on the liquid surface, a refined melt is obtained;

[0184] S3. Spheroidizing inoculation: Place a spheroidizing agent with a D90 particle size of 11 mm on one side of the bottom dam of the ladle, and compact it to form a spheroidizing agent layer after tamping; among them, the mass ratio of the spheroidizing agent to the refined melt is 1.8:100; based on the mass fraction of the spheroidizing agent being 100 wt%, it consists of the following elements with the following mass fractions: silicon 41 wt%, magnesium 7.4 wt%, manganese 3.8 wt%, calcium 2.2 wt%, yttrium 1.3 wt%, cerium 0.42 wt%, lanthanum 0.48 wt%, neodymium 0.42 wt%, aluminum 0.2 wt%, and titanium 0.4 wt%, and the balance is iron;

[0185] Evenly sprinkle a primary inoculant composed of calcium-silicon-barium alloy and silicon carbide on the surface of the spheroidizing agent layer. After compacting and ramming, a primary inoculant layer covering the surface of the spheroidizing agent layer is formed. Among them, the particle size D90 of both the calcium-silicon-barium alloy and silicon carbide is 8.5 mm. The mass ratio of the calcium-silicon-barium alloy to the refined melt is 0.22:100, and the mass ratio of silicon carbide to the refined melt is 0.18:100. Calculated with the mass fraction of the calcium-silicon-barium alloy being 100 wt%, it consists of the following elements with the following mass fractions: silicon 41 wt%, calcium 14 wt%, barium 11.2 wt%, zirconium 0.4 wt%, and antimony 0.25 wt%, and the balance is iron;

[0186] Sequentially stack perlite and iron plates on the surface of the primary inoculant layer. Control the tapping temperature of the refined melt in the melting furnace at 1505 °C, and then pour the refined melt into the ladle from one side of the bottom dam where the spheroidizing agent layer and the primary inoculant layer are not placed. During the process of pouring the refined melt, add a secondary inoculant with a particle size D90 of 1.5 mm with the flow. The mass ratio of the secondary inoculant to the refined melt is 0.035:100. Calculated with the mass fraction of the secondary inoculant being 100 wt%, it consists of the following elements with the following mass fractions: silicon 52 wt%, barium 14 wt%, calcium 12 wt%, aluminum 2.2 wt%, cerium 9 wt%, and strontium 6 wt%, and the balance is iron;

[0187] After all the refined melt in the melting furnace is poured into the ladle, insert the ultrasonic probe from above the refined melt to 85 mm below the liquid level of the refined melt, apply 1050 W of ultrasonic waves to the refined melt, the ultrasonic frequency is 22 kHz, and the ultrasonic treatment time is 2.5 min. After ultrasonic treatment, a casting liquid is obtained;

[0188] S4. Casting and forming: Preheat the mold to 520 °C in advance. When the temperature of the casting liquid reaches 1385 °C, pour the casting liquid in the ladle into the preheated mold. During the pouring process of the casting liquid, add a tertiary inoculant with a particle size D90 of 0.3 mm with the flow. The mass ratio of the tertiary inoculant to the refined melt is 0.11:100;

[0189] Calculated with the mass fraction of the tertiary inoculant being 100 wt%, it consists of the following elements with the following mass fractions: silicon 68 wt%, calcium 18 wt%, aluminum 2.2 wt%, and bismuth 0.011 wt%, and the balance is iron;

[0190] After all the casting liquid is poured into the mold, naturally cool it to 1102 °C, then adjust the cooling rate to 1.2 °C / min, and perform ultrasonic vibration on the cast mold. The ultrasonic power used is 720 W, and the ultrasonic frequency is 12 kHz; when the mold cools down to 980 °C, stop ultrasonic vibration and keep it warm for 11 h, and then naturally cool it to room temperature. After demolding, a flange casting is obtained;

[0191] S5. Quenching and tempering heat treatment: The cast flange after casting is annealed, normalized, quenched, and tempered in sequence;

[0192] First, the cast flange after casting is heated to 1010 °C at a heating rate of 22 °C / min and held for 2.2 h, then rapidly cooled to 710 °C at a cooling rate of 32 °C / min and held for 38 min, and then slowly cooled to 520 °C at a cooling rate of 12 °C / min, and taken out of the furnace and air-cooled to room temperature to complete the annealing treatment;

[0193] Then, the annealed flange is heated to 882 °C at a heating rate of 9 °C / min and held for 1.8 h, and then taken out of the furnace and air-cooled to room temperature to complete the normalizing treatment;

[0194] Then, the normalized flange is heated to 845 °C at a heating rate of 6 °C / min and held for 28 min. After the holding is completed, it is cooled in the furnace to 585 °C. Then, the flange is taken out and immediately buried in the molten salt at 290 °C, held in the molten salt for 1.8 h. When the surface temperature of the flange drops to 270 °C, the flange is taken out of the molten salt and air-cooled to room temperature to complete the quenching treatment;

[0195] Finally, the quenched flange is heated to 535 °C at a heating rate of 3.5 °C / min and held for 3.8 h, and air-cooled in the furnace to room temperature to complete the tempering treatment, obtaining the green blank of the flange;

[0196] S6. Nitrocarburizing: Carbon dioxide is introduced into the reaction furnace, the green blank of the flange is placed in the reaction furnace, the green blank of the flange is heated to 820 °C and held for 1.2 h for carburizing treatment; argon is introduced into the reaction furnace to cool down the green blank of the flange. After the green blank of the flange is cooled to 520 °C, a mixed gas composed of ammonia, nitrogen, and carbon dioxide is introduced into the reaction furnace, and the feeding amount of the mixed gas is 1100 L / h; based on the total volume fraction of the mixed gas being 100%, among them, the volume fraction of ammonia is 32%, the volume fraction of carbon dioxide is 6%, and the balance is nitrogen; after holding for 6 h, the nitrocarburizing treatment is completed, and the depth of nitrocarburizing is 12 μm, obtaining the rough product of the flange;

[0197] S7. Sandblasting roughening: The rough product of the flange is sandblasted with brown fused alumina sand with a particle size D90 of 420 μm, the sandblasting pressure is 0.65 MPa, the vertical distance between the nozzle and the surface of the rough product of the flange is 180 mm, the angle between the axis of the nozzle and the surface of the rough product of the flange is 22 °, and the surface roughness of the rough product of the flange formed after sandblasting is 52 μm; then the sandblasted rough product of the flange is placed in a mixed solvent of absolute ethanol and acetone for ultrasonic cleaning, and taken out and dried after the cleaning is completed;

[0198] S8. Coating Cladding: Mix absolute ethanol and binder in a mass ratio of 12:1 to prepare a binder solution, and mix the cladding material and the binder solution in a ratio of 1 g:0.22 mL to prepare a paste-like cladding slurry;

[0199] Based on the mass fraction of the cladding material being 100 wt%, it consists of the following components in mass fractions: cerium dioxide 0.6 wt%, tungsten carbide 32 wt%, and the balance being nickel-based alloy powder;

[0200] Based on the mass fraction of the nickel-based alloy powder being 100 wt%, it consists of the following elements in mass fractions: chromium 16 wt%, iron 5.5 wt%, silicon 3.5 wt%, boron 3.8 wt%, and carbon 0.6 wt%, with the balance being nickel;

[0201] Uniformly coat the cladding slurry on the surface of the rough flange after sandblasting and drying to form a cladding slurry layer; perform laser cladding on the cladding slurry layer through a laser. The process parameters of the laser cladding are: laser spot diameter is 3.2 mm, laser power is 1050 W, laser scanning speed is 2.5 mm / s. After cooling, a cladding layer with a thickness of 0.8 mm is formed on the surface of the rough flange to obtain the body flange.

[0202] Example 3

[0203] This example provides a production method of a body flange, as Figure 1 shown. The specific production method includes the following steps:

[0204] S1. Alloy Melting: Put the raw material mixture into a melting furnace, heat the raw material mixture to 1455 °C and hold for 1.5 h to obtain an alloy melt;

[0205] Based on the mass fraction of the raw material mixture being 100 wt%, it consists of the following elements in mass fractions: carbon 3.6 wt%, silicon 2.2 wt%, manganese 0.45 wt%, nickel 0.15 wt%, molybdenum 0.35 wt%, and vanadium 0.3 wt%, with the balance being iron;

[0206] S2. Refining and Purifying: Adjust the temperature of the alloy melt to 1530 °C, add a purifying agent to the alloy melt. The purifying agent consists of calcium oxide and aluminum oxide with a mass ratio of 1:1. The mass ratio of the purifying agent to the alloy melt is 0.5:100, hold for 55 min to complete refining and purifying; then continuously introduce nitrogen at 1.6 MPa into the melting furnace. The input amount of nitrogen is 120 Nm 3 / h, and the input time is 15 min. After removing the floating slag on the liquid surface, a refined melt is obtained;

[0207] S3. Spheroidizing and inoculating: Place the spheroidizing agent with a D90 particle size of 12 mm on one side of the dam at the bottom of the ladle, and compact it to form a spheroidizing agent layer after tamping; among them, the mass ratio of the spheroidizing agent to the refined melt is 2:100; calculated with the mass fraction of the spheroidizing agent being 100 wt%, it consists of the following elements with the following mass fractions: silicon 42 wt%, magnesium 7.3 wt%, manganese 3.5 wt%, calcium 2.5 wt%, yttrium 1.3 wt%, cerium 0.45 wt%, lanthanum 0.45 wt%, neodymium 0.45 wt%, aluminum 0.3 wt%, and titanium 0.3 wt%, and the balance is iron;

[0208] Evenly sprinkle the primary inoculant composed of calcium-silicon-barium alloy and silicon carbide on the surface of the spheroidizing agent layer, and compact it to form a primary inoculant layer covering the surface of the spheroidizing agent layer after tamping; among them, the D90 particle sizes of both the calcium-silicon-barium alloy and silicon carbide are 9 mm, the mass ratio of the calcium-silicon-barium alloy to the refined melt is 0.25:100, and the mass ratio of silicon carbide to the refined melt is 0.15:100; calculated with the mass fraction of the calcium-silicon-barium alloy being 100 wt%, it consists of the following elements with the following mass fractions: silicon 42 wt%, calcium 13 wt%, barium 11 wt%, zirconium 0.4 wt%, and antimony 0.2 wt%, and the balance is iron;

[0209] Stack perlite and iron plates on the surface of the primary inoculant layer in sequence, control the tapping temperature of the refined melt in the melting furnace at 1510 °C, and then pour the refined melt into the ladle from the side of the dam at the bottom of the ladle where the spheroidizing agent layer and the primary inoculant layer are not placed; during the process of pouring the refined melt, add the secondary inoculant with a D90 particle size of 2 mm along with the flow, and the mass ratio of the secondary inoculant to the refined melt is 0.04:100; calculated with the mass fraction of the secondary inoculant being 100 wt%, it consists of the following elements with the following mass fractions: silicon 55 wt%, barium 12 wt%, calcium 15 wt%, aluminum 2.5 wt%, cerium 8 wt%, and strontium 7 wt%, and the balance is iron;

[0210] After all the refined melt in the melting furnace is poured into the ladle, insert the ultrasonic probe from above the refined melt to 90 mm below the liquid level of the refined melt, apply 1100 W of ultrasonic waves to the refined melt, the ultrasonic frequency is 25 kHz, and the ultrasonic treatment time is 2 min to obtain the casting liquid after ultrasonic treatment;

[0211] S4. Casting and molding: Preheat the mold to 550 °C in advance. When the temperature of the casting liquid reaches 1390 °C, pour the casting liquid in the ladle into the preheated mold, and add the tertiary inoculant with a D90 particle size of 0.4 mm along with the flow during the pouring process of the casting liquid, and the mass ratio of the tertiary inoculant to the refined melt is 0.12:100;

[0212] Taking the mass fraction of the three inoculants as 100 wt%, it is composed of the following elements by mass fraction: silicon 70 wt%, calcium 15 wt%, aluminum 2.5 wt%, and bismuth 0.012 wt%, with the balance being iron;

[0213] After all the casting liquid is injected into the mold, it is naturally cooled to 1105 °C, and then the cooling rate is adjusted to 1.5 °C / min. Ultrasonic vibration is carried out on the cast mold, with the ultrasonic power of 750 W and the ultrasonic frequency of 15 kHz; when the mold is cooled to 1000 °C, the ultrasonic vibration is stopped and it is kept warm for 10 h, and then it is naturally cooled to room temperature. After demolding, a flange casting is obtained;

[0214] S5. Quenching and tempering heat treatment: The flange casting after casting and forming is subjected to annealing treatment, normalizing treatment, quenching treatment, and tempering treatment in sequence;

[0215] First, the flange casting after casting and forming is heated to 1020 °C at a heating rate of 25 °C / min and kept warm for 2 h, then it is rapidly cooled to 720 °C at a cooling rate of 35 °C / min and kept warm for 35 min, and then it is slowly cooled to 550 °C at a cooling rate of 15 °C / min, and then taken out of the furnace and air-cooled to room temperature to complete the annealing treatment;

[0216] Then, the flange casting after annealing treatment is heated to 885 °C at a heating rate of 10 °C / min and kept warm for 1.5 h, and then taken out of the furnace and air-cooled to room temperature to complete the normalizing treatment;

[0217] Then, the flange casting after normalizing treatment is heated to 850 °C at a heating rate of 7 °C / min and kept warm for 25 min. After the heat preservation is completed, it is cooled in the furnace to 590 °C, and then the flange casting is taken out and immediately buried in the molten salt at 300 °C, kept warm in the molten salt for 1.5 h. When the surface temperature of the flange casting drops to 280 °C, the flange casting is taken out of the molten salt and air-cooled to room temperature to complete the quenching treatment;

[0218] Finally, the flange casting after quenching treatment is heated to 540 °C at a heating rate of 4 °C / min and kept warm for 3.5 h, and then air-cooled in the furnace to room temperature to complete the tempering treatment, and a flange green blank is obtained;

[0219] S6. Nitrocarburizing: Carbon dioxide is introduced into the reaction furnace, and the green blank of the flange is placed in the reaction furnace. The green blank of the flange is heated to 850 °C and held for 1 h for carburizing treatment; argon is introduced into the reaction furnace to cool down the green blank of the flange. After the green blank of the flange is cooled down to 550 °C, a mixed gas composed of ammonia, nitrogen, and carbon dioxide is introduced into the reaction furnace, and the introduction amount of the mixed gas is 1200 L / h; based on the total volume fraction of the mixed gas being 100%, among them, the volume fraction of ammonia is 35%, the volume fraction of carbon dioxide is 7%, and the balance is nitrogen; after holding for 7 h, the nitrocarburizing treatment is completed, and the depth of nitrocarburizing is 15 μm, obtaining the rough flange;

[0220] S7. Sandblasting and roughening: The rough flange is sandblasted with brown fused alumina sand with a D90 particle size of 450 μm. The sandblasting pressure is 0.7 MPa, the vertical distance between the nozzle and the surface of the rough flange is 200 mm, and the angle between the axis of the nozzle and the surface of the rough flange is 25°. The surface roughness of the rough flange formed after sandblasting is 55 μm; subsequently, the sandblasted rough flange is placed in a mixed solvent of absolute ethanol and acetone for ultrasonic cleaning, and after the cleaning is completed, it is taken out and dried;

[0221] S8. Coating cladding: Absolute ethanol and a binder are mixed in a mass ratio of 15:1 to prepare a binder solution, and a cladding material and the binder solution are mixed in a ratio of 1 g:0.25 mL to prepare a paste-like cladding slurry;

[0222] Based on the mass fraction of the cladding material being 100 wt%, it is composed of the following components in mass fractions: cerium dioxide 0.7 wt%, tungsten carbide 35 wt%, and the balance is nickel-based alloy powder;

[0223] Based on the mass fraction of the nickel-based alloy powder being 100 wt%, it is composed of the following elements in mass fractions: chromium 17 wt%, iron 5 wt%, silicon 4 wt%, boron 3.5 wt%, and carbon 0.7 wt%, and the balance is nickel;

[0224] The cladding slurry is evenly coated on the surface of the sandblasted and roughened rough flange, and after drying, a cladding slurry layer is formed; the cladding slurry layer is subjected to laser cladding by a laser. The process parameters of laser cladding are: the laser spot diameter is 3.5 mm, the laser power is 1100 W, the laser scanning speed is 3 mm / s, and after cooling, a cladding layer with a thickness of 1 mm is formed on the surface of the rough flange, obtaining the body flange.

[0225] Example 4

[0226] This example provides a production method of a body flange, as Figure 1 shown, the production method specifically includes the following steps:

[0227] S1. Alloy Melting: Put the raw material mixture into a melting furnace, heat the raw material mixture to 1458 °C and keep it warm for 1.1 h to obtain an alloy melt;

[0228] Based on the mass fraction of the raw material mixture being 100 wt%, it consists of the following elements with the following mass fractions: carbon 3.65 wt%, silicon 2.2 wt%, manganese 0.5 wt%, nickel 0.12 wt%, molybdenum 0.38 wt%, and vanadium 0.3 wt%, and the balance is iron;

[0229] S2. Refining and Purifying: Adjust the temperature of the alloy melt to 1535 °C, add a purifying agent to the alloy melt. The purifying agent consists of calcium oxide and aluminum oxide with a mass ratio of 1:1. The mass ratio of the purifying agent to the alloy melt is 0.55:100. Keep it warm for 52 min to complete refining and purifying; then continuously introduce nitrogen at 1.7 MPa into the melting furnace. The input amount of nitrogen is 130 Nm 3 / h, and the input time is 12 min. After removing the scum on the liquid surface, a refined melt is obtained;

[0230] S3. Spheroidizing and Inoculating: Place a spheroidizing agent with a D90 particle size of 13 mm on one side of the bottom dam of the ladle, and compact it to form a spheroidizing agent layer after tamping; among them, the mass ratio of the spheroidizing agent to the refined melt is 2.3:100; based on the mass fraction of the spheroidizing agent being 100 wt%, it consists of the following elements with the following mass fractions: silicon 44 wt%, magnesium 7.2 wt%, manganese 3.2 wt%, calcium 2.8 wt%, yttrium 1.4 wt%, cerium 0.48 wt%, lanthanum 0.42 wt%, neodymium 0.48 wt%, aluminum 0.4 wt%, and titanium 0.2 wt%, and the balance is iron;

[0231] Uniformly sprinkle a primary inoculant composed of silicon-calcium-barium alloy and silicon carbide on the surface of the spheroidizing agent layer, and compact it to form a primary inoculant layer covering the surface of the spheroidizing agent layer; among them, the D90 particle sizes of both the silicon-calcium-barium alloy and silicon carbide are 9.5 mm. The mass ratio of the silicon-calcium-barium alloy to the refined melt is 0.28:100, and the mass ratio of silicon carbide to the refined melt is 0.12:100; based on the mass fraction of the silicon-calcium-barium alloy being 100 wt%, it consists of the following elements with the following mass fractions: silicon 43 wt%, calcium 13 wt%, barium 10.5 wt%, zirconium 0.5 wt%, and antimony 0.18 wt%, and the balance is iron;

[0232] Perlite and an iron plate are sequentially stacked on the surface of the inoculant layer. The tapping temperature of the refined molten liquid in the melting furnace is controlled at 1515 °C. Subsequently, the refined molten liquid is poured into the ladle from one side of the bottom dam where the spheroidizing agent layer and the primary inoculant layer are not placed. During the pouring of the refined molten liquid, a secondary inoculant with a D90 particle size of 2.5 mm is added with the flow. The mass ratio of the secondary inoculant to the refined molten liquid is 0.045:100. Calculated with the mass fraction of the secondary inoculant being 100 wt%, it consists of the following elements by mass fraction: silicon 58 wt%, barium 10 wt%, calcium 18 wt%, aluminum 2.8 wt%, cerium 7 wt%, and strontium 8 wt%, with the balance being iron.

[0233] After all the refined molten liquid in the melting furnace is poured into the ladle, an ultrasonic probe is inserted from above the refined molten liquid to 95 mm below the liquid level of the refined molten liquid, and ultrasonic waves of 1150 W are applied to the refined molten liquid. The ultrasonic frequency is 28 kHz, and the ultrasonic treatment time is 1.5 min. After ultrasonic treatment, a casting liquid is obtained.

[0234] S4. Casting and forming: The mold is preheated to 580 °C in advance. When the temperature of the casting liquid reaches 1395 °C, the casting liquid in the ladle is poured into the preheated mold. During the pouring of the casting liquid, a tertiary inoculant with a D90 particle size of 0.5 mm is added with the flow. The mass ratio of the tertiary inoculant to the refined molten liquid is 0.13:100.

[0235] Calculated with the mass fraction of the tertiary inoculant being 100 wt%, it consists of the following elements by mass fraction: silicon 72 wt%, calcium 12 wt%, aluminum 2.8 wt%, and bismuth 0.013 wt%, with the balance being iron.

[0236] After all the casting liquid is poured into the mold, it is naturally cooled to 1108 °C. Subsequently, the cooling rate is adjusted to 1.8 °C / min, and ultrasonic vibration is applied to the cast mold. The ultrasonic power used is 780 W, and the ultrasonic frequency is 18 kHz. When the mold cools to 1020 °C, ultrasonic vibration is stopped and it is kept warm for 9 h, and then it is naturally cooled to room temperature. After demolding, a flange casting is obtained.

[0237] S5. Tempering heat treatment: The flange casting after casting and forming is subjected to annealing treatment, normalizing treatment, quenching treatment, and tempering treatment in sequence.

[0238] First, the flange casting after casting and forming is heated to 1030 °C at a heating rate of 28 °C / min and kept warm for 1.8 h. Subsequently, it is rapidly cooled to 730 °C at a cooling rate of 38 °C / min and kept warm for 32 min. Then, it is slowly cooled to 580 °C at a cooling rate of 18 °C / min and taken out of the furnace and air-cooled to room temperature to complete the annealing treatment.

[0239] Then, heat the annealed flange casting to 888°C at a heating rate of 11°C / min and hold for 1.2 h, then take it out of the furnace and air-cool it to room temperature to complete the normalizing treatment;

[0240] Then, heat the normalized flange casting to 855°C at a heating rate of 8°C / min and hold for 22 min. After holding, cool it in the furnace to 595°C, then take out the flange casting and immediately bury it in molten salt at 310°C, hold for 1.2 h in the molten salt. When the surface temperature of the flange casting drops to 290°C, take out the flange casting from the molten salt and air-cool it to room temperature to complete the quenching treatment;

[0241] Finally, heat the quenched flange casting to 545°C at a heating rate of 4.5°C / min and hold for 3.2 h, then air-cool it in the furnace to room temperature to complete the tempering treatment, obtaining a raw flange blank;

[0242] S6. Nitrocarburizing: Introduce carbon dioxide into the reaction furnace, place the raw flange blank in the reaction furnace, heat the raw flange blank to 880°C and hold for 0.8 h for carburizing treatment; introduce argon into the reaction furnace to cool down the raw flange blank. After the raw flange blank cools down to 580°C, introduce a mixed gas composed of ammonia, nitrogen and carbon dioxide into the reaction furnace, and the input volume of the mixed gas is 1300 L / h; based on the total volume fraction of the mixed gas being 100%, among which, the volume fraction of ammonia is 38%, the volume fraction of carbon dioxide is 7%, and the balance is nitrogen; after holding for 7 h, complete the nitrocarburizing treatment, and the depth of nitrocarburizing is 18 μm, obtaining a rough flange product;

[0243] S7. Sandblasting roughening: Use brown fused alumina sand with a particle size D90 of 480 μm to perform sandblasting on the rough flange product, the sandblasting pressure is 0.75 MPa, the vertical distance between the nozzle and the surface of the rough flange product is 220 mm, the angle between the axis of the nozzle and the surface of the rough flange product is 28°, and the surface roughness of the rough flange product formed after sandblasting is 58 μm; then place the sandblasted rough flange product in a mixed solvent of absolute ethanol and acetone for ultrasonic cleaning, and take it out and dry it after cleaning;

[0244] S8. Coating cladding: Mix absolute ethanol and binder in a mass ratio of 18:1 to prepare a binder solution, and mix the cladding material and the binder solution in a ratio of 1 g:0.28 mL to prepare a paste-like cladding slurry;

[0245] Based on the mass fraction of the cladding material being 100 wt%, it consists of the following components with the following mass fractions: cerium dioxide 0.8 wt%, tungsten carbide 38 wt%, and the balance is nickel-based alloy powder;

[0246] Taking the mass fraction of the nickel-based alloy powder as 100 wt%, it is composed of the following elements with the following mass fractions: chromium 18 wt%, iron 4.5 wt%, silicon 4.5 wt%, boron 3.2 wt%, and carbon 0.8 wt%, and the balance is nickel;

[0247] The cladding slurry is evenly coated on the surface of the rough flange after sandblasting and roughening, and dried to form a cladding slurry layer; the cladding slurry layer is subjected to laser cladding by a laser, and the process parameters of the laser cladding are: the laser spot diameter is 3.8 mm, the laser power is 1150 W, the laser scanning speed is 3.5 mm / s, and after cooling, a cladding layer with a thickness of 1.2 mm is formed on the surface of the rough flange to obtain the main body flange.

[0248] Example 5

[0249] This example provides a production method of a main body flange, as Figure 1 shown, the production method specifically includes the following steps:

[0250] S1. Alloy melting: Put the raw material mixture into a melting furnace, heat the raw material mixture to 1460 °C and keep it warm for 1 h to obtain an alloy melt;

[0251] Taking the mass fraction of the raw material mixture as 100 wt%, it is composed of the following elements with the following mass fractions: carbon 3.7 wt%, silicon 2 wt%, manganese 0.6 wt%, nickel 0.1 wt%, molybdenum 0.4 wt%, and vanadium 0.2 wt%, and the balance is iron;

[0252] S2. Refining and purification: Adjust the temperature of the alloy melt to 1540 °C, add a purifying agent to the alloy melt, the purifying agent is composed of calcium oxide and aluminum oxide with a mass ratio of 1:1, the mass ratio of the purifying agent to the alloy melt is 0.6:100, keep it warm for 50 min to complete refining and purification; then continuously introduce nitrogen with a pressure of 1.8 MPa into the melting furnace, the input amount of nitrogen is 150 Nm 3 / h, and the input time is 10 min. After removing the scum on the liquid surface, a refined melt is obtained;

[0253] S3. Spheroidizing inoculation: Place the spheroidizing agent with a D90 particle size of 15 mm on one side of the bottom dam of the ladle, and compact it to form a spheroidizing agent layer after tamping; among them, the mass ratio of the spheroidizing agent to the refined melt is 2.5:100; taking the mass fraction of the spheroidizing agent as 100 wt%, it is composed of the following elements with the following mass fractions: silicon 45 wt%, magnesium 7 wt%, manganese 3 wt%, calcium 3 wt%, yttrium 1.5 wt%, cerium 0.5 wt%, lanthanum 0.4 wt%, neodymium 0.5 wt%, aluminum 0.5 wt%, and titanium 0.1 wt%, and the balance is iron;

[0254] Evenly sprinkle the primary inoculant composed of calcium-silicon-barium alloy and silicon carbide on the surface of the spheroidizing agent layer. After compacting and ramming, a primary inoculant layer covering the surface of the spheroidizing agent layer is formed. Among them, the particle size D90 of both the calcium-silicon-barium alloy and silicon carbide is 10 mm. The mass ratio of the calcium-silicon-barium alloy to the refined melt is 0.3:100, and the mass ratio of silicon carbide to the refined melt is 0.1:100. Calculated with the mass fraction of the calcium-silicon-barium alloy as 100 wt%, it is composed of the following elements with the following mass fractions: silicon 45 wt%, calcium 12 wt%, barium 10 wt%, zirconium 0.6 wt%, and antimony 0.15 wt%, and the balance is iron;

[0255] Layer by layer lay perlite and iron plates on the surface of the primary inoculant layer. Control the tapping temperature of the refined melt in the melting furnace at 1520 °C, and then pour the refined melt into the ladle from one side of the bottom dam where the spheroidizing agent layer and the primary inoculant layer are not placed. During the process of pouring the refined melt, add the secondary inoculant with a particle size D90 of 3 mm along with the flow. The mass ratio of the secondary inoculant to the refined melt is 0.05:100. Calculated with the mass fraction of the secondary inoculant as 100 wt%, it is composed of the following elements with the following mass fractions: silicon 60 wt%, barium 8 wt%, calcium 20 wt%, aluminum 3 wt%, cerium 6 wt%, and strontium 9 wt%, and the balance is iron;

[0256] After all the refined melt in the melting furnace is poured into the ladle, insert the ultrasonic probe from above the refined melt to 100 mm below the liquid level of the refined melt, apply ultrasonic waves of 1200 W to the refined melt, the ultrasonic frequency is 30 kHz, and the ultrasonic treatment time is 1 min. After ultrasonic treatment, the casting liquid is obtained;

[0257] S4. Casting and forming: Preheat the mold to 600 °C in advance. When the temperature of the casting liquid reaches 1400 °C, pour the casting liquid in the ladle into the preheated mold. During the pouring process of the casting liquid, add the tertiary inoculant with a particle size D90 of 0.6 mm along with the flow. The mass ratio of the tertiary inoculant to the refined melt is 0.15:100;

[0258] Calculated with the mass fraction of the tertiary inoculant as 100 wt%, it is composed of the following elements with the following mass fractions: silicon 75 wt%, calcium 10 wt%, aluminum 3 wt%, and bismuth 0.015 wt%, and the balance is iron;

[0259] After all the casting liquid is poured into the mold, naturally cool it to 1200 °C, then adjust the cooling rate to 2 °C / min, perform ultrasonic vibration on the cast mold, and the ultrasonic power used is 800 W, and the ultrasonic frequency is 20 kHz; when the mold cools down to 1050 °C, stop ultrasonic vibration and keep it warm for 8 h, and then naturally cool it to room temperature. After demolding, a flange casting is obtained;

[0260] S5. Quenching and tempering heat treatment: The cast flange after casting is successively annealed, normalized, quenched and tempered;

[0261] First, the cast flange after casting is heated to 1050 °C at a heating rate of 30 °C / min and held for 1.5 h, then rapidly cooled to 750 °C at a cooling rate of 40 °C / min and held for 30 min, and then slowly cooled to 600 °C at a cooling rate of 20 °C / min, and then taken out of the furnace and air-cooled to room temperature to complete the annealing treatment;

[0262] Then, the annealed flange is heated to 900 °C at a heating rate of 12 °C / min and held for 1 h, and then taken out of the furnace and air-cooled to room temperature to complete the normalizing treatment;

[0263] Then, the normalized flange is heated to 860 °C at a heating rate of 10 °C / min and held for 20 min. After the holding is completed, it is cooled in the furnace to 600 °C. Then, the flange is taken out and immediately buried in the molten salt at 320 °C and held in the molten salt for 1 h. When the surface temperature of the flange drops to 300 °C, the flange is taken out of the molten salt and air-cooled to room temperature to complete the quenching treatment;

[0264] Finally, the quenched flange is heated to 550 °C at a heating rate of 5 °C / min and held for 3 h, and then air-cooled in the furnace to room temperature to complete the tempering treatment to obtain the raw flange blank;

[0265] S6. Nitrocarburizing: Carbon dioxide is introduced into the reaction furnace, the raw flange blank is placed in the reaction furnace, the raw flange blank is heated to 900 °C and held for 0.5 h for carburizing treatment; argon is introduced into the reaction furnace to cool down the raw flange blank. After the raw flange blank is cooled to 600 °C, a mixed gas composed of ammonia, nitrogen and carbon dioxide is introduced into the reaction furnace, and the flow rate of the mixed gas is 1500 L / h; based on the total volume fraction of the mixed gas being 100%, among them, the volume fraction of ammonia is 40%, the volume fraction of carbon dioxide is 8%, and the balance is nitrogen; after holding for 8 h, the nitrocarburizing treatment is completed, and the depth of nitrocarburizing is 20 μm to obtain the rough flange;

[0266] S7. Sandblasting and roughening: The rough flange is sandblasted with brown fused alumina sand with a particle size D90 of 500 μm, the sandblasting pressure is 0.8 MPa, the vertical distance between the nozzle and the surface of the rough flange is 250 mm, and the angle between the axis of the nozzle and the surface of the rough flange is 30°. The surface roughness of the rough flange formed after sandblasting is 60 μm; then the sandblasted rough flange is placed in a mixed solvent of absolute ethanol and acetone for ultrasonic cleaning, and after the cleaning is completed, it is taken out and dried;

[0267] S8. Coating cladding: Mix absolute ethanol and binder in a mass ratio of 20:1 to prepare a binder solution, and mix the cladding material and the binder solution in a ratio of 1 g:0.3 mL to prepare a paste-like cladding slurry;

[0268] Based on the mass fraction of the cladding material being 100 wt%, it consists of the following components in mass fractions: cerium dioxide 1 wt%, tungsten carbide 40 wt%, and the balance being nickel-based alloy powder;

[0269] Based on the mass fraction of the nickel-based alloy powder being 100 wt%, it consists of the following elements in mass fractions: chromium 20 wt%, iron 4 wt%, silicon 5 wt%, boron 3 wt%, and carbon 1 wt%, with the balance being nickel;

[0270] Evenly coat the cladding slurry on the surface of the rough flange after sandblasting, and dry it to form a cladding slurry layer; perform laser cladding on the cladding slurry layer through a laser. The process parameters of the laser cladding are: the laser spot diameter is 4 mm, the laser power is 1200 W, the laser scanning speed is 4 mm / s. After cooling, a cladding layer with a thickness of 1.5 mm is formed on the surface of the rough flange to obtain the said body flange.

[0271] Example 6

[0272] This example provides a production method of a body flange. The difference from Example 1 is that in step S3, the mass ratio of the spheroidizing agent to the refining melt is adjusted to 1:100, and other process parameters and operating conditions are exactly the same as those in Example 1.

[0273] Example 7

[0274] This example provides a production method of a body flange. The difference from Example 1 is that in step S3, the mass ratio of the spheroidizing agent to the refining melt is adjusted to 3:100, and other process parameters and operating conditions are exactly the same as those in Example 1.

[0275] Example 8

[0276] This example provides a production method of a body flange. The difference from Example 1 is that in step S3, the D90 particle size of the spheroidizing agent is adjusted to 5 mm, and other process parameters and operating conditions are exactly the same as those in Example 1.

[0277] Example 9

[0278] This example provides a production method of a body flange. The difference from Example 1 is that in step S3, the D90 particle size of the spheroidizing agent is adjusted to 20 mm, and other process parameters and operating conditions are exactly the same as those in Example 1.

[0279] Example 10

[0280] This embodiment provides a production method of a body flange. The difference from Embodiment 1 is that in step S8, the mass fraction of cerium dioxide in the cladding material is adjusted to 0.1 wt%, the mass fraction of tungsten carbide remains unchanged, and the balance is nickel-based alloy powder. Other process parameters and operating conditions are exactly the same as those in Embodiment 1.

[0281] Embodiment 11

[0282] This embodiment provides a production method of a body flange. The difference from Embodiment 1 is that in step S8, the mass fraction of cerium dioxide in the cladding material is adjusted to 1.5 wt%, the mass fraction of tungsten carbide remains unchanged, and the balance is nickel-based alloy powder. Other process parameters and operating conditions are exactly the same as those in Embodiment 1.

[0283] Comparative Example 1

[0284] This comparative example provides a production method of a body flange. The difference from Embodiment 1 is that in step S3, applying ultrasonic waves to the refining solution is omitted. Other process parameters and operating conditions are exactly the same as those in Embodiment 1.

[0285] The graphite metallographic structure and the matrix metallographic structure of the green flange prepared in this comparative example were observed using a metallographic microscope, and the metallographic micrographs shown in Figure 4 and Figure 5 were obtained. Compared with the Figure 2 and Figure 3 shown in Embodiment 1, Figure 4 and Figure 5 the number of graphite balls in the metallographic micrographs shown is less and the size is larger.

[0286] Comparative Example 2

[0287] This comparative example provides a production method of a body flange. The difference from Embodiment 1 is that in step S4, ultrasonic vibration of the mold is omitted. Other process parameters and operating conditions are exactly the same as those in Embodiment 1.

[0288] The graphite metallographic structure and the matrix metallographic structure of the green flange prepared in this comparative example were observed using a metallographic microscope, and the metallographic micrographs shown in Figure 6 and Figure 7 were obtained. Compared with the Figure 2 and Figure 3 shown in Embodiment 1, Figure 6 and Figure 7 the number of graphite balls in the metallographic micrographs shown is less and the size is larger.

[0289] Comparative Example 3

[0290] This comparative example provides a production method for an integral flange. The difference from Example 1 is that during the pouring process of the casting liquid in step S4, the three inoculants were not added along with the flow, and other process parameters and operating conditions are exactly the same as those in Example 1.

[0291] The graphite metallographic structure and matrix metallographic structure of the green flange prepared in this comparative example were observed using a metallographic microscope, and the metallographic micrographs shown in Figure 8 and Figure 9 were obtained. Compared with the Figure 2 and Figure 3 shown in Example 1, Figure 8 and Figure 9 the number of graphite balls in the metallographic micrographs shown is less and the size is larger.

[0292] Comparative Example 4

[0293] This comparative example provides a production method for an integral flange. The difference from Example 1 is that cerium dioxide was not added to the cladding material in step S8, the mass fraction of tungsten carbide is the same as that in Example 1, and the balance is nickel-based alloy powder. Other process parameters and operating conditions are exactly the same as those in Example 1.

[0294] An optical microscope was used to observe the cladding layer on the surface of the integral flange prepared in this comparative example, and the optical micrograph shown in Figure 11 was obtained. Compared with the Figure 10 shown in Example 1, Figure 11 obvious cracks, pores and other defects exist in the cladding layer in the optical micrograph shown.

[0295] The tensile strength, elongation and surface hardness of the rough flanges prepared in Examples 1 - 11 and Comparative Examples 1 - 4 were tested. The specific test steps are as follows:

[0296] (1) An electronic universal material testing machine was used to test the tensile strength and elongation of the rough flanges. The flange specimens used for the test were GB1348 - 2009 standard tensile specimens for ductile iron. There were three specimens in each group, and the average value was taken as the test result; the test parameters were set as follows: the gauge length of the specimen was 30 mm, the inner diameter within the gauge length of the specimen was 6 mm, and the tensile rate was 2 mm / min.

[0297] (2) A hardness tester was used to test the surface hardness of the rough flanges. The test parameters were set as follows: the loading force was 750 kg, the indenter diameter was 5 mm, and the holding time of the test force was 15 s; during the test, 5 measurement points were selected on each specimen, and the average value was taken as the test result of the measured specimen.

[0298] The wear rate of the surface cladding layer of the integral flanges prepared in Examples 1 - 11 and Comparative Examples 1 - 4 was tested. The specific test steps are as follows:

[0299] The wear resistance of the cladding layer on the surface of the body flange was tested using a disc-type friction and wear testing machine. The testing method was reciprocating sliding friction. Alumina corundum balls were used as the sliding friction pair. The sliding speed was set at 20 cm / s, and the testing time for a single specimen was 20 s. The wear rate was calculated using the following formula:

[0300] ;

[0301] In the formula, W r is the wear rate (mm 3 ·N -1 ·m -1 ), V is the wear volume (mm 3 ), F is the vertical load (N), and L is the wear distance (m). Among them, the wear volume V was calculated using the following formula:

[0302] ;

[0303] In the formula, r is the wear scar radius (mm), and S is the cross-sectional area of the wear scar (mm 2 ).

[0304] The test results are shown in Table 1.

[0305] Table 1 Test Results

[0306]

[0307] It can be seen from the test data of Examples 1-11 and Comparative Examples 1-4 that the tensile strength and hardness of the rough flange products prepared in Examples 1-5 are higher than those in Examples 6-9 and Comparative Examples 1-3, and the wear rate of the cladding layer prepared in Examples 1-5 is higher than that in Examples 10-11 and Comparative Example 4. This indicates that the body flange prepared by the production method provided by the present invention has excellent mechanical properties and wear resistance.

[0308] It can be seen from the test data of Example 1, Example 6, and Example 7 that the tensile strength and hardness of the rough flange products prepared in Example 6 and Example 7 are lower than those in Example 1. This is because the dosage of the spheroidizing agent in Example 6 is too low, and the dosage of the spheroidizing agent in Example 7 is too high, which affects the number and roundness of graphite balls, and ultimately leads to a decrease in the comprehensive mechanical properties of the rough flange products.

[0309] It can be seen from the test data of Example 1, Example 8, and Example 9 that the tensile strength and hardness of the rough flange products prepared in Example 8 and Example 9 are lower than those in Example 1. This is because the particle size D90 of the spheroidizing agent in Example 8 is too small, and the particle size D90 of the spheroidizing agent in Example 9 is too large, which affects the number and roundness of graphite balls, and ultimately leads to a decrease in the comprehensive mechanical properties of the rough flange products.

[0310] From the test data of Example 1, Example 10, and Example 11, it can be seen that the wear rates of the surface cladding layers of the body flanges prepared in Example 10 and Example 11 are lower than that of Example 1. This is because the addition amount of cerium dioxide in Example 10 is too low, and the addition amount of cerium dioxide in Example 11 is too high, which affects the morphology and microstructure of the cladding layer, and ultimately leads to a decrease in the wear resistance of the cladding layer.

[0311] From the test data of Example 1, Comparative Example 1, and Comparative Example 2, it can be seen that the tensile strength and hardness of the rough flange products prepared in Comparative Example 1 and Comparative Example 2 are lower than those of Example 1. This indicates that applying ultrasound during the spheroidizing inoculation process and the casting molding process is beneficial to increasing the number and roundness rate of graphite balls, resulting in a significant improvement in the comprehensive mechanical properties of the finally prepared rough flange products.

[0312] From the test data of Example 1 and Comparative Example 3, it can be seen that the tensile strength and hardness of the rough flange products prepared in Comparative Example 3 are lower than those of Example 1. This indicates that adding a bismuth-containing tertiary inoculant during the casting process is beneficial to increasing the number and roundness rate of graphite balls, resulting in a significant improvement in the comprehensive mechanical properties of the finally prepared rough flange products.

[0313] From the test data of Example 1 and Comparative Example 4, it can be seen that the wear rates of the surface cladding layers of the body flanges prepared in Comparative Example 4 are lower than those of Example 1. This indicates that adding cerium dioxide to the cladding material can significantly improve the structural compactness of the cladding layer, reduce defects such as sand holes and pores in the cladding layer, and result in a significant improvement in the wear resistance of the finally prepared body flanges.

[0314] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the technical field within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A production method of an ontology flange, characterized in that Including: S1. Input raw materials into a smelting furnace for smelting to obtain an alloy melt; S2. Adjust the alloy melt to the refining temperature, add a purifying agent, keep warm, continuously introduce nitrogen gas, remove the floating slag to obtain a refined melt; S3. Place the spheroidizing agent on one side of the bottom dam of the ladle, compact it after pressing to obtain a spheroidizing agent layer, evenly spread a primary inoculant on the surface to obtain a primary inoculant layer, and sequentially stack and lay a perlite layer and an iron plate; Pour the refined melt into the ladle from the side of the bottom dam where the spheroidizing agent layer and the primary inoculant layer are not placed. During this process, add a secondary inoculant along with the flow. After all the refined melt is poured in, extend the ultrasonic probe from above to below the liquid surface to apply ultrasonic treatment to obtain a casting liquid. The composition of the spheroidizing agent: silicon 40 - 45wt%, magnesium 7 - 7.5wt%, manganese 3 - 4wt%, calcium 2 - 3wt%, yttrium 1.2 - 1.5wt%, cerium 0.4 - 0.5wt%, lanthanum 0.4 - 0.5wt%, neodymium 0.4 - 0.5wt%, aluminum 0.1 - 0.5wt%, and titanium 0.1 - 0.5wt%, with the balance being iron; The primary inoculant layer is composed of a calcium-silicon-barium alloy and silicon carbide; The composition of the secondary inoculant: silicon 50 - 60wt%, barium 8 - 15wt%, calcium 10 - 20wt%, aluminum 2 - 3wt%, cerium 6 - 10wt%, and strontium 5 - 9wt%, with the balance being iron; S4. Preheat the mold in advance. When the casting liquid reaches the casting temperature, inject it into the preheated mold. Add a tertiary inoculant along with the flow during injection; After all is injected, naturally cool to the first cooling temperature, adjust the cooling rate, perform ultrasonic vibration on the mold after casting, stop ultrasonic vibration and keep warm after cooling to the second cooling temperature, and naturally cool to room temperature and demold to obtain a flange casting; The composition of the tertiary inoculant: silicon 65 - 75wt%, calcium 10 - 20wt%, aluminum 2 - 3wt%, and bismuth 0.01 - 0.015wt%, with the balance being iron; S5. Heat the flange casting to the annealing temperature and keep warm, quickly cool to the first temperature and keep warm, slowly cool to the second temperature, take it out of the furnace and air-cool to room temperature to complete annealing; Heat the annealed casting to the normalizing temperature and keep warm, take it out of the furnace and air-cool to room temperature to complete normalizing; Heat the normalized casting to the quenching temperature and keep warm. After the heat preservation ends, cool it in the furnace to the third temperature, take out the casting and immediately bury it in the preheated molten salt. Wait until the surface temperature of the casting drops to the fourth temperature and then take it out and air-cool to room temperature to complete quenching; Heat the quenched casting to the tempering temperature and keep warm, cool it in the furnace and air-cool to room temperature to complete tempering to obtain a flange green blank; S6. Introduce carbon dioxide into the reaction furnace and add the green blank. Heat the green blank to the carburizing temperature and keep warm; After introducing a protective gas to cool the green blank to the co-permeation temperature, introduce a mixed gas composed of ammonia, nitrogen, and carbon dioxide to keep warm to complete nitrocarburizing to obtain a rough flange; S7. Use a sandblasting device to sandblast the rough flange. Place the sandblasted rough product in a mixed solvent of absolute ethanol and acetone for ultrasonic cleaning and then dry it; S8. Ethanol absolute and binder are formulated into a binder solution, and the cladding material and the binder solution are formulated into a paste-like cladding slurry; the cladding slurry is uniformly coated on the surface of the rough product after sandblasting and roughening, and dried to obtain a cladding slurry layer; the cladding slurry layer is laser-clad with a laser, and after cooling, a cladding layer is formed on the surface of the rough product to obtain the body flange, and the flange is made of ductile iron material; the composition of the cladding material: cerium dioxide 0.5 - 1wt%, tungsten carbide 30 - 40wt%, and the balance is nickel-based alloy powder.

2. The production method of the body flange according to claim 1, characterized in that, In step S1, based on the mass fraction of the raw material mixture being 100wt%, it is composed of the following elements with the following mass fractions: Carbon 3.5 - 3.7wt%, silicon 2 - 2.5wt%, manganese 0.3 - 0.6wt%, nickel 0.1 - 0.2wt%, molybdenum 0.3 - 0.4wt%, and vanadium 0.2 - 0.5wt%, and the balance is iron; The temperature of the smelting is 1450 - 1460 °C; The time of the smelting is 1 - 2 h.

3. The production method of the body flange according to claim 1, characterized in that, In step S2, the refining temperature is 1520 - 1540 °C; The mass ratio of the purifying agent to the alloy melt is (0.4 - 0.6):100; Keep warm for 50 - 60 min at the refining temperature; The inlet pressure of the nitrogen gas is 1.5 - 1.8 MPa; The nitrogen input amount is 100~150 Nm 3 / h; The inlet time of the nitrogen gas is 10 - 20 min.

4. The production method of the body flange according to claim 1, characterized in that, In step S3, the mass ratio of the nodulizer to the refined melt is (1.5 - 2.5):100; The particle size D90 of the nodulizer is 10 - 15 mm; The primary inoculant layer is composed of calcium-silicon-barium alloy and silicon carbide. Among them, the mass ratio of the calcium-silicon-barium alloy to the refined melt is (0.2 - 0.3):100, and the mass ratio of the silicon carbide to the refined melt is (0.1 - 0.2):100; Based on the mass fraction of the calcium-silicon-barium alloy being 100wt%, it is composed of the following elements with the following mass fractions: Silicon 40 - 45wt%, calcium 12 - 15wt%, barium 10 - 12wt%, zirconium 0.3 - 0.6wt%, and antimony 0.15 - 0.3wt%, and the balance is iron; The particle size D90 of the primary inoculant is 8 - 10 mm; The mass ratio of the secondary inoculant to the refined melt is (0.03 - 0.05):100; The particle size D90 of the secondary inoculant is 1 - 3 mm; The tapping temperature of the refined melt in the smelting furnace before being poured into the ladle is controlled at 1500 - 1520 °C; The ultrasonic probe extends 80 - 100 mm below the liquid level of the refined melt; The transmitting power of the ultrasonic probe is 1000 - 1200 W; The ultrasonic frequency emitted by the ultrasonic probe is 20 - 30 kHz; The time of the ultrasonic treatment is 1 - 3 min.

5. The production method of the body flange according to claim 1, characterized in that, In step S4, the mold is preheated to 500 - 600 °C; The casting temperature is 1380 - 1400 °C; The mass ratio of the tertiary inoculant to the refined melt is (0.1 - 0.15):100; The particle size D90 of the tertiary inoculant is 0.2 - 0.6 mm; The first cooling temperature is 1100 - 1200 °C; After natural cooling to the first cooling temperature, adjust the cooling rate to 1 - 2 °C / min; The ultrasonic power of the ultrasonic vibration is 700 - 800 W; The ultrasonic frequency of the ultrasonic vibration is 10 - 20 kHz; The second cooling temperature is 950 - 1050 °C; Insulate for 8 - 12 h at the second cooling temperature.

6. The production method of the body flange according to claim 1, characterized in that, In step S5, heat the flange casting to the annealing temperature at a heating rate of 20 - 30 °C / min; The annealing temperature is 1000 - 1050 °C; Insulate for 1.5 - 2.5 h at the annealing temperature; Cool from the annealing temperature to the first temperature at a cooling rate of 30 - 40 °C / min; The first temperature is 700 - 750 °C; Insulate for 30 - 40 min at the first temperature; Cool from the first temperature to the second temperature at a cooling rate of 10 - 20 °C / min; The second temperature is 500 - 600 °C; Heat the annealed flange casting to the normalizing temperature at a heating rate of 8 - 12 °C / min; The normalizing temperature is 880 - 900 °C; Insulate for 1 - 2 h at the normalizing temperature; Heat the normalized flange casting to the quenching temperature at a heating rate of 5 - 10 °C / min; The quenching temperature is 840 - 860 °C; Insulate for 20 - 30 min at the quenching temperature; The third temperature is 580 - 600 °C; The preheating temperature of the molten salt is 280 - 320 °C; The time for the flange casting to be buried in the molten salt is 1 - 2 h; The fourth temperature is 260 - 300 °C; Heat the quenched flange casting to the tempering temperature at a heating rate of 3 - 5 °C / min; The tempering temperature is 530 - 550 °C; Insulate for 3 - 4 h at the tempering temperature.

7. The production method of the body flange according to claim 1, characterized in that, In step S6, the carburizing temperature is 800 - 900 °C; Insulate for 0.5 - 1.5 h at the carburizing temperature; The co - carburizing temperature is 500 - 600 °C; Based on the total volume fraction of the mixed gas being 100%, among which, the volume fraction of ammonia is 30 - 40%, the volume fraction of carbon dioxide is 5 - 8%, and the balance is nitrogen; The feeding rate of the mixed gas is 1000 - 1500 L / h; Insulate for 5 - 8 h at the co - carburizing temperature; The depth of nitrocarburizing is 10 - 20 μm.

8. The production method of the body flange according to claim 1, characterized in that, In step S7, the abrasive medium used for the sand - blasting treatment is brown fused alumina sand; The particle size D90 of the abrasive medium is 400 - 500 μm; The sand - blasting pressure of the sand - blasting treatment is 0.6 - 0.8 MPa; The perpendicular distance between the nozzle and the surface of the rough flange during the sand - blasting treatment is 150 - 250 mm; The angle between the axis of the nozzle and the surface of the rough flange during the sand - blasting treatment is 20 - 30°; The surface roughness of the rough flange formed after the sand - blasting treatment is 50 - 60 μm.

9. The production method of the body flange according to claim 1, characterized in that, In step S8, the mass ratio of absolute ethanol to the binder is (10 - 20):1; The ratio of the cladding material to the binder solution is 1 g:(0.2 - 0.3) mL; Based on the mass fraction of the nickel-based alloy powder being 100 wt%, it consists of the following elements by mass fraction Composition: Chromium 15 - 20 wt%, iron 4 - 6 wt%, silicon 3 - 5 wt%, boron 3 - 4 wt%, and carbon 0.5 - 1 wt%, with the balance being nickel; The laser spot diameter used in the laser cladding process is 3 - 4 mm; The laser power used in the laser cladding process is 1000 - 1200 W; The laser scanning speed used in the laser cladding process is 2 - 4 mm / s; The thickness of the cladding layer is 0.5 - 1.5 mm.

10. A body flange obtained by the production method according to any one of claims 1 to 9.

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