Housing and 3D printing casting process for housing

Abstract

A housing and a 3D printing casting process therefor. The housing comprises, excepting iron as a main component, the following chemical components in percentage by mass: 3.55-3.8% of carbon; 2.3-2.7% of silicon; ≤0.7% of manganese; ≤0.06% of phosphorus; ≤0.02% of sulfur; 0.2-1.0% of copper; and ≤0.06% of magnesium. The 3D printing casting process for the housing can improve various mechanical properties of cast housings, and can reduce casting defects.

Description

3D printing casting process for the cabinet and the housing

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefits of Chinese Patent Application No. 202410181731.4 filed with the State Intellectual Property Office of China on February 18, 2024, and the contents disclosed in said application are incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure relates to the field of casting technology, and more specifically, to a box body and a 3D printing casting process for the box body that can not only improve various mechanical properties but also reduce casting defects. Background Art

[0004] In the oil and gas extraction industry, gearboxes are typically large, complex, box-shaped castings. Due to the specific nature of their use, such as offshore operations, gearboxes must meet specific mechanical property requirements in terms of tensile strength, plastic elongation, elongation after fracture, and hardness. Improving these properties is also desirable to extend the life of the gearboxes, leading to a high demand for high-performance ductile iron. However, existing technologies typically only improve certain mechanical properties of ductile iron, such as tensile strength, making the gearboxes susceptible to damage, impacting their normal operation, thus hindering the extraction process and causing irreparable losses.

[0005] In addition, due to structural reasons such as its large size and thin wall thickness, the box body is prone to upward warping deformation at its left and right ends, as shown in Figure 1. The deformation may even reach about 9 mm, which may cause the cast box body to be completely unusable, seriously affecting production efficiency and wasting production costs. Furthermore, A and B in Figure 2 respectively show the right view and main view of the planetary carrier included in the box body. It can be seen from Figure A that there are three semi-circular arc positions on the planetary carrier, and these semi-circular arc positions are the designed positions of the pouring nozzles. During the casting process, due to improper arrangement of the chiller and other reasons, the shrinkage of the pouring nozzles will be insufficient, which will cause shrinkage defects in these positions of the planetary carrier to be prone to occur, and ultimately have an adverse effect on the strength of the planetary carrier.

[0006] At the same time, in the existing technology, the box body is usually manufactured using a traditional casting process, but the traditional casting process requires manual mold making and requires multiple molds to manufacture the box body. Therefore, the mold has the disadvantages of long processing cycle, inaccurate processing precision, and high processing cost, resulting in waste of time and cost, and is also prone to quality problems.

[0007] Therefore, most people now use 3D printing casting technology to make molds, thereby shortening the mold processing cycle, improving the mold processing accuracy and reducing the mold processing cost. At the same time, the 3D printing casting process can also effectively control the mold strength during the printing process, the "fire" defect during the pouring process, the deformation of the thin-walled box, and the loose defects of key parts such as the planetary carrier, thereby improving product quality, improving production efficiency and reducing production costs. Summary of the Invention Technical issues

[0008] In order to solve the above problems, the purpose of the present disclosure is to provide a box body and a 3D printing casting process for the box body that can not only improve various mechanical properties but also reduce casting defects.

[0009] Technical Solution

[0010] A first aspect of the present disclosure provides a casing that, in addition to iron as a main component, further contains the following chemical components in mass %: 3.55-3.8% carbon; 2.3-2.7% silicon; ≤0.7% manganese; ≤0.06% phosphorus; ≤0.02% sulfur; 0.2-1.0% copper; and ≤0.06% magnesium.

[0011] Furthermore, in the chemical composition, the manganese is ≤0.5%, the phosphorus is ≤0.04%, the copper is 0.2-0.5%, and the magnesium is 0.03-0.06%.

[0012] Furthermore, the box body also contains chromium in an amount of ≤0.07%.

[0013] Furthermore, in the chemical composition, the silicon is 2.3-2.6%, the manganese is 0.5-0.7%, and the copper is 0.5-1.0%, and the box also contains ≤0.06% tin.

[0014] Furthermore, the box body is subjected to aging stress relief treatment.

[0015] Furthermore, the box body is subjected to the aging stress relief treatment and gravity pressure simultaneously.

[0016] Furthermore, an anti-deformation device is provided on the box body.

[0017] Furthermore, the anti-deformation device includes: a support column, which is arranged in the outer portion of the box body; a breathable column, which is arranged on both sides of the support column; and an anti-deformation ring, which is arranged on the support column.

[0018] Furthermore, a rigid frame is provided on the outer surface of the mold for casting the box body.

[0019] A second aspect of the present disclosure provides a 3D printing casting process for a box, comprising the following steps: a 3D printing step, namely, printing a mold for the box based on a mold design obtained through computer simulation analysis, wherein the 3D printing step can be replaced by other mold opening steps; a smelting step, namely, melting a batch containing at least a certain proportion of ductile iron pig iron, ductile iron machining scrap, steel scrap, a carburizer, and ferrosilicon; and a spheroidizing and inoculating step, namely, performing spheroidizing and inoculating treatments on the molten iron obtained in the smelting step; a furnace inspection step, namely, making a triangular sample after the spheroidizing and inoculating treatments are completed; and a pouring step, namely, pouring the molten iron after the spheroidizing and inoculating step through the mold, and performing in-stream inoculation during the pouring process, wherein after the pouring is completed, the molten iron contains, in mass %, the following: iron as the main component; 3.55-3.8% carbon; 2.3-2.7% silicon; ≤0.7% manganese; ≤0.06% phosphorus; ≤0.02% sulfur; 0.2-1.0% copper; and ≤0.06% magnesium.

[0020] Furthermore, after the pouring is completed, the manganese is ≤0.5%, the phosphorus is ≤0.04%, the copper is 0.2-0.5%, and the magnesium is 0.03-0.06%.

[0021] Furthermore, after the casting is completed, the molten iron further contains ≤0.07% chromium in mass%.

[0022] Furthermore, after the pouring is completed, the silicon content is 2.3-2.6%, the manganese content is 0.5-0.7%, and the copper content is 0.5-1.0%, and the molten iron further contains tin in an amount of ≤0.06% by mass.

[0023] Furthermore, before the 3D printing step, computer software is used to conduct a comprehensive simulation analysis of shrinkage, temperature field, solidification process, and filling process, thereby determining the design of the mold's runner, the position, size, and number of the pouring gates, and the position, size, and number of the chillers in the mold design.

[0024] Furthermore, in the 3D printing step, a resin adhesive is used and / or a coating is applied on the surface of the molding sand used in the mold and the surface is dried.

[0025] Furthermore, in the smelting step, the melting temperature is controlled at 1380°C and / or the sampling temperature is controlled at 1440°C-1460°C and / or the supercooling temperature is controlled at 1470-1490°C and / or the superheating temperature is controlled at 1500-1540°C.

[0026] Furthermore, in the spheroidization inoculation step, the spheroidization inoculation temperature is controlled at 1400-1440°C.

[0027] Furthermore, in the spheroidization and inoculation step, the spheroidization treatment and the inoculation treatment are performed simultaneously.

[0028] Furthermore, in the pouring step, the pouring temperature is controlled at 1300-1400°C.

[0029] Furthermore, in the pouring step, the in-stream inoculation is performed at the later stage of pouring.

[0030] Furthermore, after the spheroidization inoculation step is completed, the pouring of all the molten iron is completed within 10 minutes.

[0031] Furthermore, the 3D printing casting process of the box body also includes a box pressing and cooling step, that is, after the pouring step is completed, the obtained box body is naturally cooled to 200-400° C. in the mold, and then the box body is cleaned out of the mold.

[0032] Furthermore, the 3D printing casting process of the box also includes an aging stress relief step, namely: heating the box to 590-610°C at a heating rate of less than 50°C / h, keeping it warm for more than 6 hours, then cooling it to 200°C at a cooling rate of less than 50°C / h, and finally taking it out of the furnace and air cooling.

[0033] Furthermore, while the heat treatment in the aging stress relief step is being performed, gravity pressure is applied to the box.

[0034] Furthermore, in the 3D printing step, a structure corresponding to the anti-deformation device of the box body is provided on the mold.

[0035] Furthermore, the anti-deformation device includes: a support column, which is arranged in the outer portion of the box body; a breathable column, which is arranged on both sides of the support column; and an anti-deformation ring, which is arranged on the support column.

[0036] Furthermore, after the mold is printed in the 3D printing step, a rigid frame is provided on the outer surface of the mold. Beneficial effects

[0037] According to the first aspect of the present disclosure, not only can the various mechanical properties of the box be improved, but also the casting defects of the box such as warping deformation caused by structural reasons such as its large size and thin box wall thickness can be reduced, thereby improving production efficiency and reducing production costs.

[0038] According to the second aspect of the present disclosure, not only can a box body with improved various mechanical properties be manufactured, but also casting defects such as shrinkage cavities, cold shuts, slag inclusions, and warping deformation of the box body can be reduced by controlling various process parameters and setting corresponding structural features.

[0039] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG1 is a schematic diagram showing a box deformation in the prior art;

[0041] FIG2 is a schematic diagram illustrating a porosity defect of a planet carrier in the prior art, wherein A is a right side view of the planet carrier and B is a front view of the planet carrier;

[0042] FIG3 is a schematic flow chart showing a 3D printing casting process for a box body according to the first embodiment of the present disclosure;

[0043] FIG4 is a schematic diagram showing a triangular sample produced in a furnace inspection step in a 3D printing casting process for a box according to the first embodiment of the present disclosure;

[0044] FIG5 shows a metallographic photograph of Example 1 of ductile iron material QT500-7 included in the housing according to the second embodiment of the present disclosure;

[0045] FIG6 shows a metallographic photograph of Example 2 of ductile iron material QT500-7 included in the housing according to the second embodiment of the present disclosure;

[0046] FIG7 shows a metallographic photograph of Example 3 of the ductile iron material QT500-7 included in the housing according to the second embodiment of the present disclosure;

[0047] FIG8 shows a metallographic photograph of Example 1 of ductile iron material QT700-2 included in the housing according to the second embodiment of the present disclosure;

[0048] 9 is a detailed diagram showing a heat treatment process in an aging stress relief step according to Modification 3 of the present disclosure;

[0049] 10 is a schematic diagram showing gravity pressure applied to a box according to a fourth modification of the present disclosure, wherein A is an overall schematic diagram showing gravity pressure, B is a schematic diagram showing the positions of support points in gravity pressure, and C is a schematic diagram showing the positions of pressure points in gravity pressure; and

[0050] FIG. 11 is a schematic diagram illustrating a deformation prevention device provided on a box according to a fifth modification of the present disclosure. DETAILED DESCRIPTION

[0051] The technical solutions of various embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a portion of the embodiments of the present disclosure, and not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present disclosure without inventive effort are also within the scope of protection of the present disclosure.

[0052] It should be noted that in the following detailed description and claims, the use of expressions such as "approximately" and "approximately" is intended to take into account factors such as manufacturing tolerances and processing accuracy that are understood by those skilled in the art, and will not lead to ambiguity in the description or unclear scope of protection. In addition, the directions such as "upper", "lower", "left", "right", "front", and "back" that appear in this document are merely directions defined in conjunction with the accompanying drawings for ease of description. After reading this document, those skilled in the art will be able to easily identify the directions corresponding to the directions described in this document when the device is flipped or moved and presents an orientation inconsistent with that described in this document.

[0053] In this specification, “%” indicating the content of various materials and their chemical components means “mass %” unless otherwise specified. In addition, a numerical range indicated by “-” means that the numerical values ​​before and after “-” are included as the lower limit and the upper limit.

[0054] It should be noted that the same structures, elements or components in the drawings are denoted by the same reference numerals.

[0055] 1. First embodiment

[0056] FIG3 is a schematic flow chart showing a 3D printing casting process for a box body according to the first embodiment of the present disclosure. Detailed descriptions of the various steps in FIG3 are provided below.

[0057] 1.1 3D Printing

[0058] Based on the required mold obtained from computer simulation analysis, 200-mesh quartz sand was used as the molding sand, and furan resin glue was used as the adhesive. 3D printing was performed according to the following steps:

[0059] ①Spray molding sand onto the bottom surface of the mold carrier plate, and then spray adhesive onto the upper surface of the molding sand layer;

[0060] ② After the adhesive is cured, turn over the mold carrier and use monitoring equipment to check whether the molding sand layer on the mold carrier is loose;

[0061] ③ Adsorb the loosened molding sand layer, then spray molding sand appropriately at the loosened area, spray adhesive again after the sand blasting is completed, or if the molding sand layer does not loosen, continue to spray molding sand on the bonded molding sand layer, and then spray adhesive again;

[0062] ④ Repeat steps ② and ③ until the desired mold is formed.

[0063] It's important to note that during this 3D printing process, a high-strength resin adhesive, such as the furan resin glue described above, is used as an adhesive to enhance mold strength. Furthermore, to enhance the surface strength of the molding sand, a coating is applied to the sand surface and then dried, further enhancing the mold's strength and preventing deformation and cracking due to the high temperature of the molten iron during the casting process. The coating used is not particularly limited, as long as it enhances the surface strength of the molding sand.

[0064] Furthermore, it is important to note that other mold-forming methods can be used in place of 3D printing as a mold-forming method. Here, mold-forming refers to the design and fabrication of a mold or mold assembly. These other mold-forming methods include, but are not limited to, injection molding, blow molding, extrusion, die-casting, forging, and stamping, enabling the mass production of molds and castings.

[0065] 1.2 Melting

[0066] First, the ingredients are prepared according to the following ratio: 20% Q10 ductile iron pig iron, 20% Q12 ductile iron pig iron, 50% ductile iron machining scrap, 10% Class D steel scrap (manganese content <0.8%), 0.5% recarburizer, and 0.2% ferrosilicon. Then, a medium-frequency induction furnace is used to smelt the steel scrap, followed by machining scrap, and then pig iron, at a controlled melting temperature of approximately 1380°C. The use of a larger proportion of machining scrap and steel scrap is for environmental reasons and to significantly reduce production costs.

[0067] In addition, the following temperatures also need to be controlled during the smelting process: In order to determine the carbon content in the molten iron, sampling is required at a specific temperature, so the sampling temperature is controlled at 1440℃-1460℃; the higher the supercooling temperature, the worse the fluidity of the molten iron, which will reduce the quality of the casting and may even cause the casting to break, so the supercooling temperature is controlled at 1470-1490℃; if the temperature of the molten iron is too high, it may cause the crystallization core of the molten iron to decrease, making the casting prone to white spots and difficult to process, so the overheating temperature is controlled at 1500-1540℃.

[0068] 1.3 Spheroidization inoculation

[0069] After smelting, a wire feeding method is used for spheroidizing to effectively add alloying elements to the molten iron, accurately adjust the molten iron composition, and achieve microalloying. The purpose of spheroidizing is to promote the formation of crystallized cores to improve the metal structure and enhance the physical and mechanical properties of the castings. The spheroidizing agent is φ13mm rare earth silicon iron magnesium alloy spheroidizing wire.

[0070] At the same time as spheroidizing, a φ13mm inoculant wire containing ferrosilicon and Ba (barium) is fed as an inoculant using the wire feeding method for inoculation. It should be noted that compared with inoculation after spheroidizing, the purpose of performing spheroidizing and inoculation simultaneously is to further improve the metal structure and enhance the physical and mechanical properties of the casting. In addition, it has been verified that excessively high spheroidizing temperatures will lead to magnesium overflow and severe magnesium burnout in the spheroidizing agent, while excessively low spheroidizing temperatures will prevent a large amount of spheroidizing agent from being completely melted, resulting in spheroidizing failure. Therefore, the spheroidizing inoculation temperature is controlled at 1400-1440°C. In this temperature range, the solubility of magnesium can reach 0.74-0.55% at 6atm (atmospheric pressure).

[0071] 1.4 Furnace inspection

[0072] After the spheroidization inoculation treatment is completed, the molten iron is scooped with an iron spoon at a depth of about 100 mm from the surface of the molten iron. A triangular sample is immediately poured out as shown in Figure 4. The sample is then cooled to a dark red color and then immersed in water for quenching. The fracture surface is struck with a hammer and analyzed to determine whether the spheroidization treatment is successful. In addition, the judgment criteria for the triangular sample are listed in Table 1 below.

[0073] Table 1: Judgment criteria for triangular specimens

[0074] By observing the triangular specimens produced, it is found that the edges of the specimens have large rounded corners, the upper surface and sides at the pouring position are obviously shrunk, the fracture is fine and dense like velvet or silver-white fine fracture, there is shrinkage in the center of the fracture, the white corners of the fracture are clear, there is a crisp metallic sound when knocked, the audio frequency is high, and there is a smell similar to H2S when it comes into contact with water. Therefore, it can be concluded that the spheroidization effect of the molten iron is good and can be poured.

[0075] 1.5 Pouring

[0076] After the furnace inspection is complete, molten iron is poured. It's important to note that higher pouring temperatures can easily lead to shrinkage cavities in the casting, while lower pouring temperatures can easily cause cold shuts and slag inclusions. Therefore, the pouring temperature is controlled between 1300-1400°C. Furthermore, to prevent inoculation decay, the entire ladle pouring process must be completed within 10 minutes of the spheroidizing inoculation process.

[0077] At the same time, in order to enhance the inoculation effect and prevent inoculation decay, in-stream inoculation is performed in the later stages of pouring to promote the formation of crystallization cores, thereby improving the metal structure and enhancing the physical and mechanical properties of the casting. In addition, the reason for choosing in-stream inoculation in the later stages of pouring is that the temperature of the molten iron is difficult to control in the early stages of pouring. If in-stream inoculation is performed at this time, the inoculant will melt prematurely, making the molten iron poured later unable to be inoculated. At the same time, in the early stages of pouring, the inoculant used in the spheroidizing inoculation treatment still remains in the molten iron, so in-stream inoculation is not necessary.

[0078] In addition, during the flow inoculation process, an alloy inoculant containing the following chemical composition is used as an inoculant: Si (silicon): 72%-75%; Al (aluminum): 1.2%-1.5%; Ca (calcium): 1%-1.5%; Mn (manganese): 4%-4.5%; and the remainder is Fe (iron). The alloy inoculant is crushed into fine particles of 0.2-0.8 mm, and then these fine particles are pressed into a steel pipe. When the molten iron is poured, the steel pipe contacts the molten iron, thereby achieving an instantaneous inoculation effect. The alloy inoculant used accounts for 0.1% of the total mass of the molten iron.

[0079] It should be noted that the 3D printing casting process for the box body disclosed herein is not limited to the above steps and may also include, but is not limited to, product drawing analysis, FEMA (Failure Mode and Effects Analysis) analysis, solution planning and process evaluation, simulation analysis, mold sand cleaning, mold solidification, dip coating, drying, core assembly, box pressing and cooling, sand removal, polishing, removal of pouring heads, UT (Ultrasonic Testing) inspection, aging stress relief, line dimension inspection, primer spraying, and packaging and storage. Because those skilled in the art can obtain these steps based on existing technology, they will not be repeated here.

[0080] 2. Second embodiment

[0081] Next, a case according to a second embodiment of the present disclosure will be described.

[0082] 2.1 Chemical composition

[0083] First, we will describe two examples of ductile iron materials, QT500-7 and QT700-2, used in a tank body manufactured using the 3D printing casting process described in the first embodiment. Tables 2 and 3 show the chemical composition requirements for the two ductile iron materials and provide specific examples. The rationale for selecting the ranges for each chemical composition will then be explained.

[0084] Table 2: Chemical composition of QT500-7 (%)

[0085] Table 3: Chemical composition of QT700-2 (%)

[0086] Carbon can not only promote graphitization, improve spheroidization, increase the number of graphite nodules, and reduce the tendency of white cast iron, but also improve the fluidity of molten iron and reduce shrinkage defects in castings. However, too high carbon and carbon equivalent can easily cause graphite floating, which prolongs the solidification time of large castings. Therefore, the carbon content of both QT500-7 and QT700-2 is controlled at 3.55-3.8%.

[0087] In ductile iron, silicon serves as the primary inoculant, increasing its tensile strength, yield strength, and hardness while also reducing its plasticity. Furthermore, silicon shifts the material's ductile-brittle transition temperature toward higher temperatures, reducing its low-temperature impact toughness. For every 0.1% increase in Si content, the ductile-brittle transition temperature increases by 5.5-6°C. Therefore, the silicon content of QT500-7 is controlled at 2.3-2.7%, and that of QT700-2 is controlled at 2.3-2.6%.

[0088] For ductile iron, a manganese content starting at 0.6-0.8% significantly improves strength, attributed to its solid-solution strengthening of ferrite. Manganese also promotes the formation and refinement of pearlite, but it tends to accumulate at grain boundaries, forming carbides, which weaken mechanical properties. For example, elongation after fracture decreases significantly with increasing manganese content. Therefore, based on mechanical performance requirements, the manganese content of QT500-7 is controlled at ≤0.5%, and the manganese content of QT700-2 is controlled at 0.5-0.7%.

[0089] Phosphorus enters ductile iron with metal charge materials (such as pig iron, scrap steel, recycled materials, and ferroalloys). Phosphorus eutectic deteriorates mechanical properties and increases brittleness and porosity. Therefore, the phosphorus content of QT500-7 is controlled to ≤0.04%, and the phosphorus content of QT700-2 is controlled to ≤0.06%.

[0090] Sulfur enters ductile iron with the metal charge and fuel. Excessive sulfur content can lead to poor spheroidization. Reducing the sulfur content in the base iron is a prerequisite for successful spheroidization and the foundation for high-quality castings. Therefore, the sulfur content of both QT500-7 and QT700-2 is controlled at ≤0.02%.

[0091] Increasing copper content increases both strength and hardness in both ferrite and pearlite matrices. However, for ductile iron with a ferrite matrix, elongation and impact toughness (ak) decrease significantly with increasing copper content. Therefore, the copper content of QT500-7 is controlled at 0.2-0.5%. Meanwhile, for ductile iron with a pearlite matrix, copper has little effect on tensile strength and elongation. However, its effects on eliminating free cementite, inhibiting ferrite formation, and improving microstructure and performance uniformity must be considered. Therefore, the copper content of QT700-2 is controlled at 0.5-1.0%.

[0092] In ductile iron, magnesium is used as the primary component of the nodulizer, producing perfectly rounded graphite spheres. However, magnesium has poor resistance to interfering elements and is more prone to forming defects such as slag inclusions, shrinkage, and subcutaneous pores. Therefore, the magnesium content of QT500-7 is controlled at 0.03-0.06%, and that of QT700-2 is controlled at ≤0.06%.

[0093] Tin can increase the amount of pearlite and improve impact toughness, so the tin content of QT700-2 is controlled at ≤0.06%.

[0094] In addition, preferably, Cr (chromium) can be added to QT500-7. Although chromium reduces hardness, it can improve elongation and impact toughness. Therefore, the chromium content of QT500-7 is controlled to ≤0.07%.

[0095] The basic chemical components of the two ductile iron materials disclosed herein are described above. In addition to the above chemical components, the materials also contain Fe as a main component and other chemical components with negligible contents, such as Ba and Ca.

[0096] 2.2 Mechanical properties

[0097] Next, Tables 4 and 5 show the mechanical property test data for each example of the two ductile iron materials, QT500-7 and QT700-2, listed in Tables 2 and 3. As can be seen from Tables 4 and 5, compared with conventional ductile iron materials, the mechanical properties of these two materials not only meet the mechanical performance requirements but are significantly improved, with some even achieving very significant improvements. For example, the tensile strength, plastic extension strength, and elongation after fracture of QT500-7 Example 1 were 678, 429, and 11.5, respectively, far exceeding the requirements.

[0098] Table 4: Mechanical properties of QT500-7

[0099] Table 5: Mechanical properties of QT700-2

[0100] Furthermore, Figures 5 to 7 respectively show metallographic photographs of Example 1, Example 2 and Example 3 of the ductile iron material QT500-7 contained in the box body according to the second embodiment of the present disclosure. Figure 8 shows a metallographic photograph of Example 1 of the ductile iron material QT700-2 contained in the box body according to the second embodiment of the present disclosure. In these figures, the left figure is a metallographic photograph before corrosion, and the right figure is a metallographic photograph after corrosion. Here, the corrosion method used is a method well known in the art. It can be seen from these metallographic photographs that the matrix structure of QT500-7 is a ferrite + pearlite two-phase mixed matrix structure, the matrix structure of QT700-2 is pearlite, and the graphite spheroidization effect of both is good.

[0101] 3. Modifications

[0102] Next, various modifications according to the embodiment of the present disclosure will be described.

[0103] 3.1 Modification 1

[0104] This variation involves simulation analysis of the 3D printing casting process for the box body according to the first embodiment of the present disclosure. To control casting deformation and porosity defects, MAGMAsoft software was used to simulate and analyze shrinkage, temperature field, solidification process, and filling process in the early stages of casting. Optimization was also performed in the following aspects:

[0105] Optimize the gating system design to improve the finish and surface quality of castings;

[0106] Optimize the location, size and number of gating and risers to eliminate shrinkage and cavitation;

[0107] Optimize the location, size and quantity of chillers to eliminate deformation and looseness;

[0108] Optimizing the chemical composition of ductile iron, smelting and inoculation of the metal to prevent the formation of critical phases during solidification and subsequent cooling of the metal;

[0109] Establish a stable process to ensure the required mechanical properties;

[0110] Minimize problems such as cold cracking and dimensional errors in casting design;

[0111] Under the condition of ensuring the required metallographic structure and mechanical properties, the heat treatment process should be reasonably designed.

[0112] 3.2 Modification 2

[0113] This variation relates to press cooling during the 3D printing casting process for the box body according to the first embodiment of the present disclosure. Specifically, after pouring, to prevent defects such as deformation and shrinkage, the cooling rate is controlled, allowing the box body to slowly and naturally cool to a temperature of 200-400°C in the mold before being removed from the mold.

[0114] 3.3 Modification 3

[0115] This variation relates to stress relief during aging during the 3D printing casting process for the housing according to the first embodiment of the present disclosure. To eliminate stress within the housing, the housing can be heat treated as shown in Figure 9: heating the housing to 590-610°C at a heating rate of less than 50°C / h, holding the temperature for at least 6 hours, then cooling the housing to 200°C at a cooling rate of less than 50°C / h, and finally removing the housing from the furnace and air-cooling.

[0116] 3.4 Modification 4

[0117] In order to better correct the deformation of the box, as shown in A in Figure 10, the box that is warped upward is turned upside down, and then supported at the lower end with tooling. According to the amount of deformation, weights of appropriate size, weight and number are selected, and the weights are placed on top of the box to apply gravity pressure. Subsequently, the weights and the box are subjected to the above-mentioned heat treatment in Deformation Example 3.

[0118] In this modified example, as shown in FIG10A , the triangles schematically indicate the positions of the support points of the tooling, and the arrows schematically indicate the positions of the pressure points where gravity is applied. Furthermore, as shown in FIG10B , the triangles schematically indicate the positions of the support points of the tooling, and as shown in FIG10C , the triangles schematically indicate the positions of the pressure points where gravity is applied. As can be seen from these figures, this modified example uses four toolings to support the box body, and uses eight weights to apply gravity pressure to the box body.

[0119] It should be noted that the aforementioned fixture can be not only a supporting device that simply supports, but also a clamping device that performs both clamping and supporting functions. Furthermore, the aforementioned support and pressure point locations are merely illustrative and non-restrictive; as long as the selected locations can correct the warping deformation, they will suffice. Those skilled in the art should recognize that the method for correcting box deformation is not limited to gravity pressure as described above; any method known in the art capable of correcting such deformation can also be used.

[0120] 3.5 Modification 5

[0121] In this variation, corresponding structural features can be added during the 3D printing step of the box mold to form an anti-deformation device 2 on the box body 1. As shown in Figure 11, the anti-deformation device 2 consists of a plurality of support columns 21-1 to 21-6, a plurality of vent columns 22-1 to 22-6, and an anti-deformation ring 23. It should be noted that in the following text, when no special distinction is required, the support columns 21-1 to 21-6 and the vent columns 22-1 to 22-6 are collectively referred to as support columns 21 and vent columns 22, respectively.

[0122] In Figure 11, the support columns 21 are mainly arranged at both ends of the outer portion of the box body 1, that is, the areas with larger deformation, and are also arranged in the central area of ​​the outer portion. The breathable columns 22 are hollow and are arranged on both sides of the support columns 21, and play a supporting function and a breathable and shrinkage-compensating function at the same time. The breathable and shrinkage-compensating function of the breathable columns 22 effectively prevents the box body 1 located below from having loose shrinkage defects. The anti-deformation ring 23 is arranged on the support column 21 and is formed into an annular shape with an outer contour roughly the same as the outer contour of the box body 1. Because the support columns 21, the breathable columns 22 and the anti-deformation ring 23 make the structure of the box body 1 thicker, it is possible to prevent the box body 1 from having the defect of upward warping deformation. In addition, in the polishing step of the casting, the anti-deformation device 2 on the box body 1 can be cut off.

[0123] Those skilled in the art will recognize that the above-described structure of the anti-deformation device 2 is merely exemplary, and that, for example, the anti-deformation device 2 may comprise only a single anti-deformation ring 23, which may be disposed directly on the outer periphery of the housing 1 and formed into an annular shape having an outer contour substantially identical to that of the housing 1. Thus, by thickening the housing 1, upward warping of the housing 1 can be prevented. Of course, the support columns, vent columns, anti-deformation ring, and any other technical features known in the art for thickening the housing 1 may be applied to the housing 1 individually or in combination.

[0124] 3.6 Variation 6

[0125] In this variation, the effect of preventing the box from warping and deforming upward is achieved by changing the sand core fastening method. In the prior art, the traditional process solution for the sand core fastening method is: a long screw is passed through the entire mold, and then the two ends of the long screw are tightened with nuts to fasten the mold, thereby further fastening the sand core. In this article, the process solution for the optimized sand core fastening method is: on the six sides of the outside of the mold, front, back, left, right, top and bottom, a rigid frame is formed by using channel steel to fasten the mold, thereby effectively preventing the mold deformation caused by high-temperature molten iron, and ultimately achieving the effect of preventing the box from deforming.

[0126] It should be pointed out that by combining Variations 3 to 6, the amount of deformation of the box body due to warping is reduced from 9mm to 4mm, which greatly reduces the risk of the box body being scrapped, improves production efficiency, and reduces production costs.

[0127] Although preferred embodiments of the present disclosure have been described above with reference to the accompanying drawings, the present disclosure is not limited to the above-described embodiments. Those skilled in the art will appreciate that various changes, combinations, sub-combinations, and modifications may be made without departing from the spirit or scope of the present disclosure as defined in the appended claims. Furthermore, the beneficial effects of the present disclosure are not limited to those described above, but may include other effects that may be conceived upon reading the present disclosure.

Claims

1. A tank comprising, in addition to iron as a main component, the following chemical components in mass %: 3.55-3.8% carbon; 2.3-2.7% silicon; ≤0.7% manganese; ≤0.06% phosphorus; ≤0.02% sulfur; 0.2-1.0% copper; and ≤0.06% magnesium.

2. The box according to claim 1, wherein In the chemical composition, the manganese is ≤0.5%, the phosphorus is ≤0.04%, the copper is 0.2-0.5%, and the magnesium is 0.03-0.06%.

3. The box according to claim 2, wherein The housing also contains ≤ 0.07% chromium.

4. The housing according to claim 1, wherein In the chemical composition, the silicon is 2.3-2.6%, the manganese is 0.5-0.7%, and the copper is 0.5-1.0%, and the box also contains ≤0.06% tin.

5. The box according to any one of claims 1 to 4, wherein The box body is subjected to aging stress relief treatment.

6. The housing according to claim 5, wherein The box body is subjected to the aging stress relief treatment and gravity pressure simultaneously.

7. The box according to any one of claims 1 to 4, wherein An anti-deformation device is provided on the box body.

8. The housing according to claim 7, wherein The anti-deformation device comprises: a support column disposed in a peripheral portion of the box; Breathable columns, which are arranged on both sides of the support column; as well as An anti-deformation ring is arranged on the support column.

9. The box according to any one of claims 1 to 4, wherein A rigid frame is provided on the outer surface of the mold for casting the box.

10. A 3D printing casting process for a box, comprising the following steps: A 3D printing step, namely, printing a mold for the box body based on a mold design obtained through computer simulation analysis, wherein the 3D printing step can be replaced by other mold opening steps; a smelting step, namely, melting a batch comprising at least a certain proportion of ductile iron pig iron, ductile iron machining scrap, steel scrap, a carburizer, and ferrosilicon; a spheroidizing and inoculating step, namely, performing spheroidizing and inoculating treatments on the molten iron obtained in the smelting step; A furnace inspection step, namely, making a triangular sample after the spheroidizing treatment and the inoculation treatment are completed; and a pouring step, namely, pouring the molten iron after the spheroidization inoculation step through the mold, and performing inoculation during the pouring process, wherein after the pouring is completed, the molten iron contains, in mass %, iron as a main component; 3.55-3.8% carbon; 2.3-2.7% silicon; ≤0.7% manganese; ≤0.06% phosphorus; ≤0.02% sulfur; 0.2-1.0% copper; and ≤0.06% magnesium.

11. The 3D printing casting process for a box according to claim 10, wherein After the pouring is completed, the manganese is ≤0.5%, the phosphorus is ≤0.04%, the copper is 0.2-0.5%, and the magnesium is 0.03-0.06%.

12. The 3D printing casting process for a box according to claim 11, wherein After the casting is completed, the molten iron still contains ≤0.07% of chromium in terms of mass %.

13. The 3D printing casting process for a box according to claim 10, wherein After the pouring is completed, the silicon content is 2.3-2.6%, the manganese content is 0.5-0.7%, and the copper content is 0.5-1.0%. The molten iron further contains tin content of ≤0.06% by mass.

14. The 3D printing casting process for a box according to claim 10, wherein Before the 3D printing step, computer software is used to conduct a comprehensive simulation analysis of shrinkage, temperature field, solidification process, and filling process, thereby determining the design of the mold's runners, the position, size, and number of pouring and riser gates, and the position, size, and number of chillers in the mold design.

15. The 3D printing casting process for a box according to claim 10, wherein In the 3D printing step, a resin adhesive and / or a coating is applied to the surface of the molding sand used in the mold and the surface is dried.

16. The 3D printing casting process for a box according to claim 10, wherein In the smelting step, the melting temperature is controlled at 1380°C and / or the sampling temperature is controlled at 1440°C-1460°C and / or the supercooling temperature is controlled at 1470-1490°C and / or the superheating temperature is controlled at 1500-1540°C.

17. The 3D printing casting process for a box according to claim 10, wherein In the spheroidization inoculation step, the spheroidization inoculation temperature is controlled at 1400-1440°C.

18. The 3D printing casting process for a box according to claim 10, wherein In the spheroidization and inoculation step, the spheroidization treatment and the inoculation treatment are performed simultaneously.

19. The 3D printing casting process for a box according to claim 10, wherein In the pouring step, the pouring temperature is controlled at 1300-1400°C.

20. The 3D printing casting process for a box according to claim 10, wherein In the pouring step, the in-stream inoculation is performed at the later stage of pouring.

21. The 3D printing casting process for a box according to claim 10, wherein After the spheroidization inoculation step is completed, the pouring of all the molten iron is completed within 10 minutes.

22. The 3D printing casting process for a box according to claim 10, further comprising: The box pressing and cooling step is: after the pouring step is completed, the obtained box body is naturally cooled to 200-400° C. in the mold, and then the box body is cleaned out from the mold.

23. The 3D printing casting process for a box according to any one of claims 10 to 22, further comprising: The aging stress relief step is as follows: heating the box to 590-610°C at a heating rate of less than 50°C / h, keeping the temperature for more than 6 hours, then cooling to 200°C at a cooling rate of less than 50°C / h, and finally taking the box out of the furnace and air cooling.

24. The 3D printing casting process for a box according to claim 23, wherein While the heat treatment in the aging stress relief step is being performed, gravity pressure is applied to the box.

25. The 3D printing casting process for a box according to any one of claims 10-22, wherein In the 3D printing step, a structure corresponding to the anti-deformation device of the box body is provided on the mold.

26. The 3D printing casting process for a box according to claim 25, wherein The anti-deformation device comprises: a support column disposed in a peripheral portion of the box; Breathable columns, which are arranged on both sides of the support column; as well as An anti-deformation ring is arranged on the support column.

27. The 3D printing casting process for a box according to any one of claims 10-22, wherein After the mold is printed in the 3D printing step, a rigid frame is set on the outer surface of the mold.

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