A casting process for high-precision forming grinder bed castings

Abstract

The present application relates to the field of casting, and specifically discloses a high-precision molding grinder bed casting casting process. The high-precision molding grinder bed casting casting process comprises the following steps: by mass percentage, 80-85% pig iron, 5-10% steel, and 10% ductile iron are mixed and smelted, and then alloying elements are added to obtain molten iron; according to the structure of the casting, a cavity corresponding to the size of the casting is made in a sand box by molding sand, a runner is opened in the molding sand in the sand box, and the runner size is calculated by the casting structure, and the molten iron is poured into the cavity through the runner, and the pouring temperature is 1350-1380℃; after gradually cooling and molding, a casting blank is obtained, and the casting blank is annealed. The high-precision molding grinder bed casting casting process of the present application has the advantages of high rigidity and higher processing accuracy.

Description

Technical Field

[0001] The present application relates to the field of casting, and more specifically, to a casting process for a high-precision molding grinder bed casting. Background Art

[0002] A grinder is a high-precision processing equipment, usually used to process the surface of various metal parts. As the basic supporting part of the grinder, the main function of the bed is to support various parts and ensure that the entire grinder has sufficient rigidity and stability during operation.

[0003] The material selection of the grinding machine bed is crucial to its performance. Traditionally, gray cast iron is the most commonly used material. The graphite structure of gray cast iron has good shock absorption ability, which helps to reduce the vibration effect during processing. Cast iron materials are easy to cut and form, suitable for the design of various complex structures. Compared with steel, gray cast iron has a lower cost and is easy to cast on a large scale.

[0004] The material of the conventional grinding machine bed is HT300, and the hardness of the casting guide rail is required to be 180-200HB. After the bed casting is processed into parts, the flatness of the guide rail is 0.006mm / 1000mm, and the straightness is 0.006mm / 1000mm; the flatness within the full length of the guide rail is not greater than 0.03mm. The straightness is not greater than 0.03mm. Since the wall thickness of the guide rail is greater than 100mm, it is difficult to meet the hardness greater than 180HB, so the process uses graphite cold iron for quenching to make the guide rail dense and the hardness greater than 180HB. The pouring system is set to feed molten iron at both ends, and the deformation of the casting is 8-10mm.

[0005] Although HT300 cast iron has moderate strength, hardness and rigidity, it cannot meet the needs of workpieces that require higher rigidity. However, under heavy loads or vibration conditions, it is prone to slight deformation, which in turn affects processing accuracy and service life. The design of molten iron inlet at both ends can easily lead to uneven temperature fields, resulting in defects such as shrinkage cavities or shrinkage. Although graphite chillers can promote cooling, the uniform distribution design may cause local stress concentration and reduced fatigue strength. At the same time, the cooling efficiency of the chiller is limited, and it cannot completely suppress thermal cracks or coarse grain problems, resulting in greater internal stress in the casting and increasing the risk of deformation in subsequent processing. Summary of the invention

[0006] In order to solve the above problems, the present application provides a high-precision molding grinder bed casting casting process.

[0007] The present application provides a high-precision forming grinding machine bed casting casting process using the following technical solutions:

[0008] A high-precision molding grinding machine bed casting casting process comprises the following steps:

[0009] By mass percentage, 80-85% of pig iron, 5-10% of steel, and 10% of ductile iron are mixed and smelted, and alloying elements are added to obtain molten iron, which includes C: 3.4-3.6%, Si: 2.20-2.60%, Mn: 0.4-0.6%, P: <0.04%, S: <0.02%, Cu: 0.6-0.8%, Mo: 0.3-0.4% by mass percentage;

[0010] According to the structure of the casting, a cavity of the corresponding casting size is made in the sand box through the molding sand, a runner is opened in the sand in the sand box, and the runner size is calculated according to the structure of the casting. The molten iron is poured into the cavity through the runner at a pouring temperature of 1350-1380℃;

[0011] After gradually cooling and forming, a casting blank is obtained, and the casting blank is annealed.

[0012] By adopting the above technical scheme, this process adopts an improved material ratio, through the mixed smelting of pig iron, steel and ductile iron, further adding alloy elements to optimize the composition of molten iron, so that the rigidity of the casting is greatly improved. The carbon content (3.4-3.6%) in the molten iron ensures the hardness and wear resistance of the casting and avoids the formation of brittle phases; silicon (2.20-2.60%) improves the fluidity and toughness of cast iron and enhances its antioxidant capacity; manganese (0.4-0.6%) enhances hardness and wear resistance while inhibiting the harmful effects of sulfur. The content of phosphorus and sulfur is strictly controlled below 0.04% and 0.02% to maintain the toughness and machinability of the material. Copper (0.6-0.8%) improves corrosion resistance and high temperature hardness, and molybdenum (0.3-0.4%) enhances the high temperature strength and wear resistance of the casting, ensuring its stability and durability under high load and vibration conditions. The proportion of these alloy elements makes the casting have excellent mechanical properties and long-term working reliability.

[0013] Optionally, there are multiple groups of runners opened along the length direction of the casting, and the interval between two adjacent groups of runners is 1.2-1.5m. Each group of runners includes a straight runner, a cross runner and an ingrown runner. The straight runner is opened in the molding sand along the height direction of the casting, the cross runner is arranged parallel to the horizontal direction of the casting, and the ingrown runner is arranged perpendicular to the bottom of the casting. One end of the straight runner is opened on the upper surface of the sand box, and the other end is connected to the inside of the cross runner. One end of the ingrown runner is connected to the cross runner, and the other end is connected to the mold cavity in the sand box.

[0014] Optionally, the calculation method of the sprue is as follows: flow-blocking cross-sectional area: sprue pipe diameter = ingrowth diameter*1.4.

[0015] Optionally, the calculation method of the cross runner is: cross runner diameter = inner runner diameter * 1.2.

[0016] Optionally, the calculation method of the ingates is: ingates pipe diameter = flow-blocking cross-sectional area.

[0017] By adopting the above technical scheme, the design of molten iron at both ends in the prior art is prone to uneven temperature field, thereby producing defects such as shrinkage cavities or shrinkage. The runner design in this application adopts a plurality of runners along the length direction of the casting, and cooperates with the reasonable layout of the straight runner, the cross runner and the inner runner, so that the molten metal can evenly fill the cavity, avoiding local overheating or insufficient cooling, thereby reducing the shrinkage cavities and shrinkage problems. Although graphite cold iron helps cooling in the prior art, its uniform distribution design may cause local stress concentration, thereby affecting fatigue strength. This application makes the flow of molten metal smoother through precise runner design and flow resistance cross-sectional area matching (straight runner diameter = inner runner diameter 1.4, cross runner diameter = inner runner diameter 1.2, etc.), reduces the stress concentration caused by local excessive cooling, thereby improving the overall structural strength and fatigue life of the casting. In the prior art, the cooling efficiency of cold iron is limited, and it may not be possible to completely suppress thermal cracks or coarse grains. This application optimizes the flow and cooling path of the molten metal through a reasonable runner layout, reduces the dependence of the cold iron on the cooling process, makes the cooling process of the casting more uniform, avoids thermal cracks and coarse grain problems caused by uneven cooling, and improves the overall quality of the casting. Since the runner design in this application can effectively control the uniform distribution of the temperature field and reduce the internal stress formed in the casting during the cooling process, it significantly reduces the risk of deformation in subsequent processing and improves the dimensional stability of the casting and the accuracy of subsequent processing.

[0018] Optionally, the specific method of the annealing treatment is:

[0019] The casting blank is heated from room temperature to 250°C for 2h, kept at this temperature for 1h, then heated to 400°C at a rate of ≤30°C / h and kept at this temperature for 1h. After the end of the heat preservation, the casting blank is heated to 570-610°C at the same rate and kept at this temperature for 5h. After the heat preservation, the casting blank is cooled with the furnace to <200°C and taken out of the furnace, completing the first annealing;

[0020] The casting after the first annealing is subjected to rough machining. The casting after rough machining is heated to 200°C at a speed of ≤50°C / h at room temperature and kept for 1-2h, then heated to 400°C, kept for 1-2h, then heated to 570-610°C and kept for 5-7h. After the end of the heat preservation, the casting is cooled to 500°C and kept for 1h at a speed of ≤30°C / h, cooled to 410°C and kept for 1h, cooled to 350°C and kept for 1h, cooled to 350°C and kept for 1h, cooled to 230°C and kept for 1h, and taken out of the furnace when the temperature drops below 100 degrees Celsius, completing the second annealing;

[0021] The casting after the second annealing is semi-finished, and the semi-finished casting is heated to 240-260°C at a rate of ≤30°C / h at room temperature, and kept warm for 6 hours. After the insulation is completed, it is cooled to <60°C and taken out of the furnace, completing the third annealing.

[0022] By adopting the above technical scheme, high temperature and long-term heat preservation (570-610℃) during multiple annealing processes can help to homogenize the grain size of the casting and eliminate the coarse grain structure, thereby improving the toughness and impact resistance of the casting. Through multiple temperature-controlled annealing, the internal structure of the casting is gradually refined, and the grain boundaries are strengthened, so that the tensile strength and fatigue resistance of the material are significantly improved. The heat treatment method of gradual heating and slow cooling avoids drastic temperature changes, reduces the tendency of thermal cracks caused by thermal stress concentration, and ensures that the surface and internal defects of the casting are effectively controlled. After multiple annealing, the residual stress of the casting is significantly reduced and the internal structure is more stable, which means that in the subsequent mechanical processing process, the casting is not easy to deform, which helps to improve processing accuracy and dimensional stability.

[0023] Optionally, an anti-deformation amount of 8-12 mm is reserved in the cavity.

[0024] By adopting the above technical solution, the casting will undergo dimensional changes during the cooling process due to thermal expansion and contraction effects, usually accompanied by slight deformation. By reserving 8-12mm of reverse deformation in the cavity, the shrinkage during cooling can be effectively compensated, so that the casting can be closer to the design size after cooling, so that less machining allowance is required during subsequent processing, reducing material cutting waste, improving production efficiency, and reducing material costs. By reserving reverse deformation, the casting obtains a certain shape compensation during the cooling process, which makes its internal stress more evenly distributed during subsequent mechanical processing, reduces deformation caused by stress release during processing, further improves processing accuracy, and avoids stress concentration or uneven stress distribution caused by excessive dimensional deviation. This can improve the durability and mechanical properties of castings, such as fatigue strength and deformation resistance, in actual use.

[0025] Optionally, the molding sand in the sand box is composite resin molding sand, and the preparation method of the composite resin molding sand is:

[0026] By weight, 1000-3000 parts of quartz sand are placed in a drum for pretreatment, and 10-20 parts of a surfactant are added for treatment for 30-50 minutes;

[0027] Add 80-100 parts of phenolic resin and 10-30 parts of modified epoxy resin into a stirring container, mix them by ultrasonic for 20-30 minutes, and slowly add 1-3 parts of nano silicon dioxide and 1-2 parts of nano aluminum oxide during the stirring process to obtain a composite resin;

[0028] Put the pretreated quartz sand into a mixing device, add the composite resin and stir at a speed of 200-300r / min for 10-30min to obtain composite resin molding sand.

[0029] By adopting the above technical scheme, the molding sand obtains a higher bonding strength by adding a mixture of phenolic resin and modified epoxy resin. Phenolic resin provides good thermal stability, while modified epoxy resin enhances its mechanical strength, ensuring that the molding sand can withstand high temperature and mechanical shock during the casting process and reducing the possibility of cavity damage. The addition of nano-silicon dioxide and nano-alumina not only improves the strength of the molding sand, but also optimizes its fluidity and filling capacity. These nanomaterials can effectively fill the tiny gaps between quartz sand particles, making the surface of the molding sand smoother, thereby reducing the surface roughness and defects of the casting and improving the finish and precision of the casting surface. Phenolic resin and modified epoxy resin show good thermal stability under high temperature conditions, while the introduction of nano-silicon dioxide and nano-alumina further improves the heat resistance of the molding sand. This makes the molding sand less prone to thermal cracking during high-temperature casting, ensuring the overall quality of the casting.

[0030] In summary, this application has the following beneficial effects:

[0031] 1. This application improves the mechanical properties and durability of castings by optimizing the material ratio and smelting process. 80-85% pig iron, 5-10% steel, and 10% ductile iron are mixed and smelted, and alloy elements are added to balance the composition of molten iron. Carbon (3.4-3.6%) ensures hardness and wear resistance, silicon (2.20-2.60%) improves fluidity and toughness, and manganese (0.4-0.6%) enhances hardness and inhibits the harmful effects of sulfur. At the same time, the phosphorus (<0.04%) and sulfur (<0.02%) contents are strictly controlled to maintain toughness. Copper (0.6-0.8%) improves corrosion resistance and high temperature hardness, and molybdenum (0.3-0.4%) enhances high temperature strength and wear resistance, ensuring the stability and reliability of castings under high load and vibration conditions.

[0032] 2. In this application, it is preferred to design multiple groups of runners to be evenly distributed along the length of the casting, and to coordinate the calculation of the flow-blocking cross-sectional area matching to ensure the stable flow of the molten metal, evenly fill the cavity, and reduce casting defects such as shrinkage cavities and shrinkage. This layout avoids the problems of local overheating or insufficient cooling in the prior art, while reducing local stress concentration and improving the structural strength and fatigue life of the casting. In addition, precise temperature field control reduces internal stress during the cooling process, improves dimensional stability and the accuracy of subsequent processing.

[0033] 3. The present application preferably uses three temperature-controlled annealings to gradually refine the internal structure of the casting, eliminate coarse grains, and improve toughness, impact resistance, and tensile strength. Long-term heat preservation at high temperature helps to strengthen grain boundaries and enhance fatigue resistance, while slow heating and cooling reduce thermal stress concentration and avoid thermal cracks. By reserving 8-12mm of reverse deformation, the dimensional changes during the cooling process are compensated, the processing accuracy is improved, and material waste is reduced. The use of composite resin molding sand enhances the mechanical strength and thermal stability of the molding sand, and the addition of nanomaterials further enhances the fluidity and heat resistance of the molding sand, and improves the surface finish and overall quality of the casting. DETAILED DESCRIPTION

[0034] The present application is further described in detail below in conjunction with the examples. It is particularly noted that if no specific conditions are specified in the following examples, the experiments are carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following examples can be obtained from common commercial sources.

[0035] Preparation Example 1

[0036] A method for preparing composite resin molding sand:

[0037] High-quality quartz sand with uniform particle size and few impurities is selected as the main raw material.

[0038] 2000kg of quartz sand is fed into a special drum pre-treatment device. The drum should be cleaned in advance to ensure that no impurities remain.

[0039] 15 kg of long-chain fatty alcohol polyoxyethylene ether surfactant (purchased from Zhejiang Sandu Chemical AEO-9) was evenly sprinkled on the quartz sand in the drum and mixed for 40 minutes to allow the quartz sand and the surfactant to be fully mixed and act.

[0040] Prepare 90kg of phenolic resin (purchased from McLean Reagent P875865) and 20kg of modified epoxy resin (Shenzhen Borui Technology BH-MEP-31001), pour the two resins into a clean container. Start the ultrasonic mixing equipment, place the resin mixture in the ultrasonic field, and perform ultrasonic mixing for 25 minutes. During the ultrasonic mixing process, add 2kg of nano-silicon dioxide with a purity of >99% and 1.5kg of nano-alumina with a purity of >98% to obtain a composite resin.

[0041] Use a mixer, pour the pre-treated quartz sand into the mixing equipment, slowly add the composite resin into the quartz sand, and stir at a speed of 250r / min for 20 minutes to form a uniform composite resin molding sand.

[0042] Preparation Example 2

[0043] A method for preparing composite resin molding sand: The difference from Preparation Example 1 is that 2000kg quartz sand, 15kg surfactant, 80kg phenolic resin, 10kg modified epoxy resin, 1kg nano-silicon dioxide, and 1kg nano-alumina are selected.

[0044] Preparation Example 3

[0045] A method for preparing composite resin molding sand: The difference from Preparation Example 1 is that 2000kg quartz sand, 15kg surfactant, 100kg phenolic resin, 30kg modified epoxy resin, 3kg nano-silicon dioxide, and 2kg nano-alumina are selected.

[0046] Example 1

[0047] A casting process for high-precision forming grinder bed castings:

[0048] 820kg of Shanxi Jianbang Q10 ductile iron, 80kg of Q235 recycled scrap steel, and 100kg of QT600-3 ductile iron recycled materials were mixed, smelted in a one-to-two medium frequency electric furnace, and alloying elements were added to obtain molten iron, which includes C: 3.4-3.6%, Si: 2.20-2.60%, Mn: 0.4-0.6%, P: <0.04%, S: <0.02%, Cu: 0.6-0.8%, Mo: 0.3-0.4% by mass percentage;

[0049] According to the structure of the casting, a cavity of a corresponding casting size is prepared in a sand box by composite resin molding sand, and a 10mm anti-deformation amount is reserved in the cavity. The composite resin molding sand is prepared by Preparation Example 1. A runner is opened in the molding sand in the sand box, and multiple groups of runners are opened along the length direction of the casting. Each group of runners includes a straight runner, a cross runner and an ingrown runner. The straight runner is opened in the molding sand along the height direction of the casting, and the cross runner is arranged in parallel along the horizontal direction of the casting. The ingrown runner is arranged vertically to the bottom of the casting, one end of the straight runner is opened on the upper surface of the sand box, and the other end is connected to the inside of the cross runner. One end of the ingrown runner is connected to the cross runner, and the other end is connected to the cavity in the sand box. The runner position avoids the hot node, and the distance between two adjacent groups is 1.4 meters. The diameter of the ingrown runner = the flow blocking cross-sectional area, the diameter of the straight runner = the diameter of the ingrown runner * 1.4, and the diameter of the cross runner = the diameter of the ingrown runner * 1.2. The molten iron is poured into the cavity through the runner, and the pouring temperature is 1360°C;

[0050] After gradually cooling and forming, a casting blank is obtained, and the casting blank is roughly processed in a gantry milling machine, with a 5mm margin reserved for the processing surface. The casting blank is heated from room temperature to 250°C for 2h, kept warm for 1h, and then heated to 400°C at a rate of ≤30°C / h and kept warm for 1h. After the insulation is completed, the casting blank is heated to 570-610°C at the same rate and kept warm for 5h. After the insulation is completed, the casting blank is cooled with the furnace to <200°C and taken out of the furnace, completing the first annealing;

[0051] The casting after the first annealing is semi-finished in a CNC machining center. Except for the guide surface and the shaft hole, which reserve 2mm margin, the other machining surfaces are machined to the drawing size. After machining, the casting is heated to 200℃ at room temperature at a speed of ≤50℃ / h and kept warm for 1-2h, then heated to 400℃, kept warm for 1-2h, and then heated to 570-610℃ and kept warm for 5-7h. After the insulation is completed, the casting is cooled to 500℃ at a speed of ≤30℃ / h and kept warm for 1h, cooled to 410℃ and kept warm for 1h, cooled to 350℃ and kept warm for 1h, cooled to 350℃ and kept warm for 1h, cooled to 230℃ and kept warm for 1h. When the temperature drops below 100 degrees Celsius, it is taken out of the furnace to complete the second annealing;

[0052] The casting blank after the second annealing is heated to 240-260°C at a rate of ≤30°C / h at room temperature and kept warm for 6 hours. After the insulation is completed, it is taken out of the furnace when it is cooled to <60°C, completing the third annealing.

[0053] Example 2

[0054] A casting process for a high-precision molding grinder bed casting: The difference from Example 1 is that 800kg of Shanxi Jianbang Q10 ductile iron, 100kg of Q235 recycled scrap steel, and 100kg of QT600-3 ductile iron recycled material are mixed and smelted in a one-to-two medium frequency electric furnace.

[0055] Example 3

[0056] A casting process for a high-precision forming grinder bed casting: The difference from Example 1 is that 850kg of Shanxi Jianbang Q10 ductile iron, 50kg of Q235 recycled scrap steel, and 100kg of QT600-3 ductile iron recycled material are mixed and smelted in a one-to-two medium frequency electric furnace.

[0057] Example 4

[0058] A casting process for a high-precision molding grinder bed casting: The difference from Example 1 is that the annealing treatment is only performed for the first time.

[0059] Example 5

[0060] A casting process for a high-precision molding grinding machine bed casting: The difference from Example 1 is that the composite resin molding sand is prepared by Preparation Example 2.

[0061] Example 6

[0062] A casting process for a high-precision molding grinder bed casting: The difference from Example 1 is that the composite resin molding sand is prepared by Preparation Example 3.

[0063] Example 7

[0064] A casting process for a high-precision molding grinding machine bed casting: The difference from Example 1 is that quartz sand is used as the molding sand.

[0065] Example 8

[0066] A casting process for a high-precision molding grinder bed casting: The difference from Example 1 is that an 8mm reverse deformation amount is reserved in the mold cavity.

[0067] Example 9

[0068] A casting process for a high-precision molding grinder bed casting: The difference from Example 1 is that a 12 mm reverse deformation amount is reserved in the mold cavity.

[0069] Comparative Example 1

[0070] A casting process for a high-precision molding grinder bed casting: The difference from Example 1 is that 700kg of Shanxi Jianbang Q10 ductile iron, 150kg of Q235 recycled scrap steel, and 150kg of QT600-3 ductile iron recycled material are mixed and smelted in a one-to-two medium frequency electric furnace.

[0071] Comparative Example 2

[0072] A casting process for a high-precision molding grinding machine bed casting: The difference from Example 1 is that the molten iron includes C: 4%, Si: 3%, Mn: 0.8%, P: 0.04%, S: 0.02%, Cu1%, and Mo0.6% by mass percentage.

[0073] Comparative Example 3

[0074] A casting process for a high-precision molding grinding machine bed casting: The difference from Example 1 is that a 6mm reverse deformation amount is reserved in the mold cavity.

[0075] Comparative Example 4

[0076] A casting process for a high-precision molding grinding machine bed casting: The difference from Example 1 is that a 14 mm reverse deformation amount is reserved in the mold cavity.

[0077] Comparative Example 5

[0078] A casting process for a high-precision molding grinder bed casting: The difference from Example 1 is that the diameters of the sprue, the cross runner and the inner runner are all the same as the flow-blocking cross-sectional area.

[0079] Use a hardness tester to test the hardness of the casting surface in accordance with the requirements of the "GB / T 231.1-2018 Brinell Hardness Test for Metal Materials" standard.

[0080] After the casting is processed into parts, the flatness and straightness of the guide rails are measured.

[0081] Table 1 Test results statistics

[0082]

[0083] Combining Example 1 and Comparative Examples 1-2 and Table 1, it can be seen that the process adopts an improved material ratio, and through the mixed smelting of pig iron, steel and ductile iron, alloy elements are further added to optimize the composition of molten iron, so that the rigidity of the casting is greatly improved. The alloy composition in the present application can achieve a higher hardness than that of Comparative Examples 1-2.

[0084] It can be seen from Example 1 and Comparative Examples 3-4 and Table 1 that by reserving an amount of reverse deformation of 8-12 mm in the cavity, the shrinkage during cooling can be effectively compensated, and the casting obtains a certain shape compensation during the cooling process, which makes the internal stress more evenly distributed during subsequent mechanical processing, reduces the deformation caused by stress release during the processing, further improves the processing accuracy, and avoids the problem of stress concentration or uneven stress distribution caused by excessive dimensional deviation.

[0085] It can be seen from Example 1 and Comparative Example 5 and Table 1 that the present application makes the flow of molten metal smoother and reduces the stress concentration caused by excessive local cooling, thereby improving the overall structural strength of the casting and the overall quality of the casting through precise runner design and flow resistance cross-sectional area matching (straight runner diameter = ingrowth runner diameter 1.4, cross runner diameter = ingrowth runner diameter 1.2, etc.).

[0086] It can be seen from the combination of Examples 1-9 and Table 1 that 80-85% pig iron, 5-10% steel, and 10% ductile iron are mixed and smelted, and alloying elements are added to balance the composition of molten iron, thereby improving the mechanical properties and processing accuracy of the casting. Through the design of multiple groups of runners, the casting is evenly distributed along the length direction of the casting, and the flow-blocking cross-sectional area matching calculation is coordinated to ensure the stable flow of molten metal, uniformly fill the mold cavity, and reduce casting defects such as shrinkage holes and shrinkage. This layout avoids the problem of local overheating or insufficient cooling in the prior art, while reducing local stress concentration and improving the structural strength and fatigue life of the casting. Through multiple temperature-controlled annealing, the internal structure of the casting is gradually refined, coarse grains are eliminated, and toughness, impact resistance and tensile strength are improved. High temperature and long-term heat preservation help to strengthen grain boundaries and enhance fatigue resistance, and slow heating and cooling reduce thermal stress concentration and avoid thermal cracking. By reserving 8-12mm reverse deformation, the dimensional change during the cooling process is compensated, the processing accuracy is improved and material waste is reduced. The use of composite resin molding sand enhances the mechanical strength and thermal stability of the molding sand. The addition of nanomaterials further improves the fluidity and heat resistance of the molding sand, and improves the surface finish and overall quality of the casting.

[0087] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A casting process for a high-precision molding grinder bed casting, characterized in that: The following steps are involved: By mass percentage, 80-85% pig iron, 5-10% steel, and 10% ductile iron are mixed and smelted, and alloying elements are added to obtain molten iron, which includes C: 3.4-3.6%, Si: 2.20-2.60%, Mn: 0.4-0.6%, P: <0.04%, S: <0.02%, Cu: 0.6-0.8%, and Mo: 0.3-0.4% by mass percentage; According to the structure of the casting, a cavity of the corresponding casting size is made in the sand box through the molding sand, a runner is opened in the sand in the sand box, and the runner size is calculated according to the structure of the casting. The molten iron is poured into the cavity through the runner, and the pouring temperature is 1350-1380℃; After gradually cooling and forming, a casting blank is obtained, and the casting blank is annealed; The runners are provided in multiple groups along the length direction of the casting, and each group of the runners includes a straight runner, a cross runner and an ingrow. The straight runner is provided in the molding sand along the height direction of the casting, the cross runner is provided in parallel with the horizontal direction of the casting, the ingrow is provided perpendicularly to the bottom of the casting, one end of the straight runner is opened on the upper surface of the sand box, and the other end is connected to the inside of the cross runner, and one end of the ingrow is connected to the cross runner, and the other end is connected to the mold cavity in the sand box; The specific method of the annealing treatment is: The casting blank is heated from room temperature to 250°C for 2h, kept at this temperature for 1h, then heated to 400°C at a rate of ≤30°C / h and kept at this temperature for 1h. After the end of the heat preservation, the casting blank is heated to 570-610°C at the same rate and kept at this temperature for 5h. After the heat preservation, the casting blank is cooled with the furnace to <200°C and taken out of the furnace, completing the first annealing; The casting after the first annealing is subjected to rough machining. The casting after rough machining is heated to 200°C at a speed of ≤50°C / h at room temperature and kept for 1-2h, then heated to 400°C, kept for 1-2h, then heated to 570-610°C and kept for 5-7h. After the end of the heat preservation, the casting is cooled to 500°C and kept for 1h at a speed of ≤30°C / h, cooled to 410°C and kept for 1h, cooled to 350°C and kept for 1h, cooled to 350°C and kept for 1h, cooled to 230°C and kept for 1h, and taken out of the furnace when the temperature drops below 100 degrees Celsius, completing the second annealing; The casting after the second annealing is semi-finished, and the semi-finished casting is heated to 240-260°C at a rate of ≤30°C / h at room temperature, and kept warm for 6 hours. After the insulation is completed, it is taken out of the furnace when it is cooled to <60°C, completing the third annealing; The molding sand in the sand box adopts composite resin molding sand, and the preparation method of the composite resin molding sand is as follows: By weight, 1000-3000 parts of quartz sand are placed in a drum for pretreatment, and 10-20 parts of a surfactant are added for treatment for 30-50 minutes; Add 80-100 parts of phenolic resin and 10-30 parts of modified epoxy resin into a stirring container, mix them by ultrasonic for 20-30 minutes, and slowly add 1-3 parts of nano silicon dioxide and 1-2 parts of nano aluminum oxide during the stirring process to obtain a composite resin; Put the pretreated quartz sand into a mixing device, add the composite resin and stir at a speed of 200-300r / min for 10-30min to obtain composite resin molding sand.

2. The casting process of the high-precision forming grinding machine bed casting according to claim 1 is characterized in that: The calculation method of the ingates is: ingates diameter = flow blocking cross-sectional area.

3. The casting process of the high-precision forming grinding machine bed casting according to claim 1 is characterized in that: The calculation method of the straight runner is: straight runner diameter = inner runner diameter * 1.

4.

4. The casting process of the high-precision forming grinding machine bed casting according to claim 1 is characterized in that: The calculation method of the cross runner is: cross runner diameter = inner runner diameter * 1.

2.

5. The casting process of the high-precision forming grinding machine bed casting according to claim 1 is characterized in that: An 8-12 mm anti-deformation amount is reserved in the mold cavity.

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