High-hardness machine tool casting and preparation method thereof

Abstract

The invention belongs to the technical field of metal casting, and particularly relates to a high-hardness machine tool casting and a preparation method thereof. The preparation method of the machine tool casting comprises the following steps: S1, weighing the following raw materials in parts by weight: 180-240 parts of pig iron, 60-120 parts of scrap iron, 100-150 parts of foundry returns, 50-90 parts of modified steel slag, 1-5 parts of a copper-beryllium intermediate alloy, 3-8 parts of silicon iron, 10-15 parts of a carburant and 1-5 parts of a nucleating agent for later use; heating scrap iron, adding modified steel slag, foundry returns, pig iron and a carburant, continuously heating, adding a copper-beryllium intermediate alloy and silicon iron, and discharging to obtain molten iron; and S2, the molten iron in the step S1 is added into an inoculant for inoculation treatment, and casting forming is carried out. The machine tool casting prepared by adopting the preparation method has relatively high hardness.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal casting, and particularly relates to a high-hardness machine tool casting and a preparation method thereof. Background Art

[0002] Machine tool castings refer to various metal castings used in machine tool manufacturing, such as components like machine tool beds, worktables, columns, crossbeams, and gantry top connecting beams. These castings play a crucial role in the structure of machine tools, not only affecting the stability and durability of the machine tools but also directly related to machining accuracy and efficiency. In response to the process of industrial development, new requirements are put forward for the performance of machine tools. Currently, modern machine tools are developing towards high load, high efficiency, and high precision, which undoubtedly also poses higher performance requirements for castings, such as being required to have high strength, high stiffness, low stress, and good hardness uniformity.

[0003] Through visiting factories, it is found that machine tool castings have the problem of poor hardness, which greatly increases costs and reduces the efficiency of actual production. To solve the above problems, the present invention provides a preparation method that can significantly improve the hardness of castings while maintaining high strength and high elastic modulus, with the expectation of extending the service life of castings. Summary of the Invention

[0004] The first object of the present invention is to provide a preparation method for high-hardness machine tool castings, which is simple to prepare and easy for large-scale production.

[0005] The second object of the present invention is to provide a high-hardness machine tool casting with excellent hardness.

[0006] To achieve the above objects, the technical solution adopted by the present invention is as follows:

[0007] A preparation method for high-hardness machine tool castings includes the following steps:

[0008] S1. By weight, weigh the following raw materials: 180 - 240 parts of pig iron, 60 - 120 parts of iron filings, 100 - 150 parts of return materials, 50 - 90 parts of modified steel slag, 1 - 5 parts of copper-beryllium master alloy, 3 - 8 parts of ferrosilicon, 10 - 15 parts of carburizer, and 1 - 5 parts of inoculant, and set aside; after heating the iron filings, add the modified steel slag, return materials, pig iron, and carburizer, continue to heat and then add the copper-beryllium master alloy and ferrosilicon, and obtain molten iron after tapping.

[0009] S2. Add the molten iron obtained in step S1 to the inoculant for inoculation treatment, and then carry out casting and molding.

[0010] Preferably, the preparation process of the modified steel slag is as follows:

[0011] (1) Mix the steel slag, diatomite, and clay evenly, grind them to obtain a mixed powder; add fly ash, silicon carbide, manganese dioxide, calcium stearate, and water to the mixed powder, mix evenly and granulate, and obtain the product after drying;

[0012] (2) Preheat the product of step (1), and then raise the temperature for calcination treatment to obtain the modified steel slag.

[0013] Preferably, the mass ratio of the steel slag, diatomite, clay, fly ash, silicon carbide, manganese dioxide, calcium stearate, and water in step (1) is (2-3):(1-2):(3-6):(2-3):(0.2-1):(0.1-0.5):(10-15).

[0014] Preferably, the temperature of the preheating treatment in step (2) is 300-400 °C, and the time of the preheating treatment is 30-40 min; the temperature of the calcination treatment is 1000-1100 °C, and the time of the calcination treatment is 15-25 min.

[0015] Preferably, in step S1, the temperature is raised to 1100-1200 °C, and then continued to be raised to 1500-1600 °C; the temperature of the furnace outlet is 1450-1500 °C.

[0016] Preferably, the temperature of the casting in step S2 is 1350-1400 °C.

[0017] Preferably, the carburizing agent is a graphite carburizing agent, and the inoculant is composed of a silicon-barium inoculant and a 75 ferrosilicon inoculant with a mass ratio of (2-3):1.

[0018] Preferably, the particle size of the copper-beryllium master alloy is 300-400 mesh.

[0019] A high-hardness machine tool casting is prepared by using the preparation method of the above high-hardness machine tool casting.

[0020] Compared with the prior art, the beneficial effects of the present invention mainly lie in:

[0021] 1. In the high-hardness machine tool casting of the present invention, components such as modified steel slag and copper-beryllium master alloy are added. Through the inspection of the properties of the obtained castings, it is found that the combined use of modified steel slag and copper-beryllium master alloy can significantly improve the hardness of the castings. Further analysis reveals that components such as fly ash and diatomite added during the preparation process of modified steel slag can generate gases during the calcination process, and the carbonates in the steel slag can also generate gases such as carbon dioxide at high temperatures, thereby forming a rich porous structure on its surface and inside, which can regulate the fluidity of molten iron, prevent its coagulation, reduce shrinkage porosity defects, and then enable the obtained machine tool casting to have a stable organizational structure, thus improving the hardness of the casting. The addition of copper-beryllium master alloy can further refine the internal organizational structure, such as forming intermetallic compounds such as Be 2 Fe, which has good precipitation strengthening effect and can effectively improve the hardness of machine tool castings. At the same time, the refined organizational structure also helps to reduce shrinkage porosity defects in the castings and improve the overall performance of the castings.

[0022] 2. The preparation method of the high-hardness machine tool casting of the present invention is simple and easy to realize large-scale production. Specific Embodiments

[0023] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below, and preferred embodiments of the present invention are given. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0024] In the embodiment of the present invention, the particle size of the beryllium master alloy involved is 300 - 400 mesh.

[0025] 1. Preparation Examples

[0026] Preparation Example 1

[0027] This preparation example provides a modified steel slag, and the specific preparation process is as follows:

[0028] (1) Weigh each raw material according to the mass ratio of steel slag, diatomite, clay, fly ash, silicon carbide, manganese dioxide, calcium stearate and water of 2.5:1.5:4:2.5:0.5:0.2:12; mix the steel slag, diatomite and clay evenly, and grind to obtain a mixed powder; add fly ash, silicon carbide, manganese dioxide, calcium stearate and water to the mixed powder, mix evenly and granulate, and dry at 70°C for 18h to obtain a product;

[0029] (2) Preheat the product of step (1) at 350°C for 35 min, and then raise the temperature to 1050°C for calcination treatment for 20 min to obtain modified steel slag.

[0030] Preparation Example 2

[0031] This preparation example provides a modified steel slag, and the specific preparation process is as follows:

[0032] (1) Weigh each raw material according to the mass ratio of steel slag, diatomite, clay, fly ash, silicon carbide, manganese dioxide, calcium stearate and water of 2:(1 - 2):3:2:0.2:0.1:10; mix the steel slag, diatomite and clay evenly, and obtain a mixed powder after grinding; add fly ash, silicon carbide, manganese dioxide, calcium stearate and water to the mixed powder, mix evenly and then granulate, and obtain the product after drying at 70°C for 18 h;

[0033] (2) Preheat the product obtained in step (1) at 300°C for 30 min, and then raise the temperature to 1000°C for calcination treatment for 25 min to obtain the modified steel slag.

[0034] Preparation Example 3

[0035] This preparation example provides a modified steel slag, and the specific preparation process is as follows:

[0036] (1) Weigh each raw material according to the mass ratio of steel slag, diatomite, clay, fly ash, silicon carbide, manganese dioxide, calcium stearate and water of 3:(1 - 2):6:3:1:0.5:15; mix the steel slag, diatomite and clay evenly, and obtain a mixed powder after grinding; add fly ash, silicon carbide, manganese dioxide, calcium stearate and water to the mixed powder, mix evenly and then granulate, and obtain the product after drying at 70°C for 18 h;

[0037] (2) Preheat the product obtained in step (1) at 400°C for 30 min, and then raise the temperature to 1100°C for calcination treatment for 15 min to obtain the modified steel slag.

[0038] Preparation Example 4

[0039] This preparation example provides a modified steel slag, which is different from Preparation Example 1 in that diatomite and clay are not added, and the other raw materials and their dosages, as well as the preparation process conditions, are the same as those in Preparation Example 1.

[0040] 2. Examples

[0041] Example 1

[0042] This example provides a preparation method for high-hardness machine tool castings, which is as follows:

[0043] S1. Weigh 200 parts of pig iron, 91 parts of iron filings, 118 parts of return scrap, 67 parts of the modified steel slag of Preparation Example 1, 3 parts of copper-beryllium master alloy (CuBe4), 6 parts of ferrosilicon, 12 parts of graphite carburizer, and 4 parts of inoculant, and set aside; among them, the inoculant consists of a silicon-barium inoculant (Si: 69-72%, Ca: 2.1-2.8%, Ba: 1.3-2.5%, the balance is Fe) and a 75% ferrosilicon inoculant (Si: 73-75%, Al≤0.3%, the balance is Fe) with a mass ratio of 2.5:1; add the iron filings to the electric furnace, heat up to 1150 °C, then add the modified steel slag, return scrap, pig iron, and graphite carburizer, continue to heat up to 1550 °C, then add the copper-beryllium master alloy and ferrosilicon, and tap the molten iron at 1460 °C to obtain molten iron;

[0044] S2. Heat the molten iron pouring ladle to 700 °C and dry it, then add the inoculant to the bottom of the molten iron pouring ladle. The bottom of the ladle is flat. Quickly pour the molten iron from step S1 into the molten iron pouring ladle, stir the molten iron to melt the inoculant, and obtain the inoculated molten iron after slag removal; pour the inoculated molten iron into the mold and cast it at 1360 °C. After molding, it is ready.

[0045] This embodiment also provides a high-hardness machine tool casting prepared by the above preparation method.

[0046] Example 2

[0047] This embodiment provides a preparation method for a high-hardness machine tool casting, which is as follows:

[0048] S1. Weigh 180 parts of pig iron, 60 parts of iron filings, 100 parts of return scrap, 50 parts of the modified steel slag of Preparation Example 2, 1 part of copper-beryllium master alloy, 3 parts of ferrosilicon, 10 parts of graphite carburizer, and 1 part of inoculant, and set aside; among them, the inoculant consists of a silicon-barium inoculant (Si: 69-72%, Ca: 2.1-2.8%, Ba: 1.3-2.5%, the balance is Fe) and a 75% ferrosilicon inoculant (Si: 73-75%, Al≤0.3%, the balance is Fe) with a mass ratio of 2:1; add the iron filings to the electric furnace, heat up to 1100 °C, then add the modified steel slag, return scrap, pig iron, and graphite carburizer, continue to heat up to 1500 °C, then add the copper-beryllium master alloy and ferrosilicon, and tap the molten iron at 1450 °C to obtain molten iron;

[0049] S2. Heat the molten iron pouring ladle to 700 °C and dry it, then add the inoculant to the bottom of the molten iron pouring ladle. The bottom of the ladle is flat. Quickly pour the molten iron from step S1 into the molten iron pouring ladle, stir the molten iron to melt the inoculant, and obtain the inoculated molten iron after slag removal; pour the inoculated molten iron into the mold and cast it at 1350 °C. After molding, it is ready.

[0050] This embodiment also provides a high-hardness machine tool casting, which is prepared by the above preparation method.

[0051] Example 3

[0052] This embodiment provides a preparation method for a high-hardness machine tool casting, which is as follows:

[0053] S1. By weight, weigh 240 parts of pig iron, 120 parts of iron filings, 150 parts of return material, 90 parts of the modified steel slag of Preparation Example 3, 5 parts of copper-beryllium master alloy, 8 parts of ferrosilicon, 15 parts of graphite carburizer, and 5 parts of inoculant, and set aside; among them, the inoculant is composed of a silicon-barium inoculant (Si: 69-72%, Ca: 2.1-2.8%, Ba: 1.3-2.5%, the balance is Fe) and a 75 ferrosilicon inoculant (Si: 73-75%, Al≤0.3%, the balance is Fe) with a mass ratio of 3:1; add the iron filings to an electric furnace, heat up to 1200°C, then add the modified steel slag, return material, pig iron, and graphite carburizer, continue to heat up to 1600°C, then add the copper-beryllium master alloy and ferrosilicon, and tap the molten iron at 1500°C to obtain molten iron;

[0054] S2. Heat the molten iron pouring ladle to 700°C and dry it, then add the inoculant to the bottom of the molten iron pouring ladle. The bottom of the ladle is flat. Quickly pour the molten iron in step S1 into the molten iron pouring ladle, stir the molten iron to melt the inoculant, and obtain the inoculated molten iron after slag removal; pour the inoculated molten iron into a mold and cast it at 1400°C. After molding, it is ready.

[0055] This embodiment also provides a high-hardness machine tool casting, which is prepared by the above preparation method.

[0056] 3. Comparative Examples

[0057] Comparative Example 1

[0058] This comparative example provides a preparation method for a machine tool casting, which is different from that of Example 1 in that: the modified steel slag of Preparation Example 4 is used instead of the modified steel slag of Preparation Example 1, and the rest are the same as those of Example 1.

[0059] This comparative example also provides a machine tool casting, which is prepared by the above preparation method.

[0060] Comparative Example 2

[0061] This comparative example provides a preparation method for a machine tool casting, which is different from that of Example 1 in that: steel slag is used instead of the modified steel slag of Preparation Example 1, and the rest are the same as those of Example 1.

[0062] This comparative example also provides a machine tool casting, which is prepared by the above preparation method.

[0063] Comparative Example 3

[0064] This comparative example provides a method for preparing a machine tool casting, which is different from Example 1 in that: steel slag and silicon carbide are used instead of the modified steel slag in Preparation Example 1, and the amounts of steel slag and silicon carbide are the same as those in Example 1, and the remaining preparation process conditions are also the same as those in Example 1.

[0065] This comparative example also provides a machine tool casting prepared by the above preparation method.

[0066] Comparative Example 4

[0067] This comparative example provides a method for preparing a machine tool casting, which is different from Example 1 in that: the copper-beryllium master alloy is omitted, and the rest are the same as those in Example 1.

[0068] This comparative example also provides a machine tool casting prepared by the above preparation method.

[0069] 4. Test Examples

[0070] The properties of the machine tool castings prepared in Examples 1-3 and Comparative Examples 1-4 were detected, and the detection methods and detection indexes are as follows:

[0071] Brinell hardness: Tested with reference to GB / T231.2-2022, and the results are shown in Table 1;

[0072] Tensile strength: Tested with reference to GB / T228.1-2021, and the results are shown in Table 1;

[0073] Elastic modulus: Tested with reference to GB / T22315-2008, and the results are shown in Table 1.

[0074] Table 1

[0075] Sample Brinell hardness / HBC Tensile strength / MPa Elastic modulus / GPa Example 1 235 384 149 Example 2 231 380 146 Example 3 234 382 147 Comparative example 1 216 371 140 Comparative example 2 204 362 135 Comparative example 3 210 366 137 Comparative example 4 212 368 138

[0076] As can be seen from Table 1, compared with Comparative Examples 1-4, the machine tool castings prepared in Examples 1-3 can significantly improve the hardness of the castings while maintaining high strength and high elastic modulus. In Comparative Example 1, the preparation process of the modified steel slag was adjusted. In Comparative Example 2, the modified steel slag was replaced with steel slag. In Comparative Example 3, the modified steel slag was replaced with steel slag and silicon carbide. In Comparative Example 4, the copper-beryllium master alloy was omitted. The above results show that the combination of the modified steel slag and the copper-beryllium master alloy can improve the hardness of the castings. Further analysis reveals that components such as fly ash and diatomaceous earth added during the preparation process of the modified steel slag of the present invention can generate gases during the calcination process, and the carbonates in the steel slag can also generate gases such as carbon dioxide at high temperatures, thereby forming a rich porous structure on its surface and inside, which can regulate the fluidity of the molten iron, prevent its condensation, reduce shrinkage porosity defects, and thus enable the obtained machine tool castings to have a stable organizational structure, and further improve the hardness of the castings. The addition of the copper-beryllium master alloy can further refine the internal organizational structure, such as forming intermetallic compounds such as Be 2 Fe, etc., which have good precipitation strengthening effects and can effectively improve the hardness of the machine tool castings. At the same time, the refined organizational structure also helps to reduce shrinkage porosity defects in the castings and improve the overall performance of the castings.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. The basic principles and main features of the present invention have been described with specific implementation schemes above. Based on the present invention, some modifications or replacements can be made, but these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of protection required by the present invention.

Claims

1. A method for preparing a high-hardness machine tool casting, characterized in that: The steps include: S1. Weigh the following raw materials in parts by weight: 180-240 parts of pig iron, 60-120 parts of iron filings, 100-150 parts of recycled materials, 50-90 parts of modified steel slag, 1-5 parts of copper-beryllium master alloy, 3-8 parts of ferrosilicon, 10-15 parts of carburizer, and 1-5 parts of inoculant for standby use; after heating the iron filings, add the modified steel slag, recycled materials, pig iron, and carburizer, continue to heat up, add the copper-beryllium master alloy and ferrosilicon, and obtain molten iron after the furnace; S2. Add the molten iron in step S1 to the inoculant for inoculation treatment, and then cast it into shape.

2. The method for preparing a high-hardness machine tool casting according to claim 1, characterized in that: The preparation process of the modified steel slag is as follows: (1) steel slag, diatomaceous earth and clay are mixed uniformly, and the mixed powder is obtained after grinding; fly ash, silicon carbide, manganese dioxide, calcium stearate and water are added to the mixed powder, the mixture is mixed uniformly, granulated and dried to obtain a product; (2) The product of step (1) is preheated and then heated to be calcined to obtain modified steel slag.

3. The method for preparing a high-hardness machine tool casting according to claim 2, characterized in that: The mass ratio of steel slag, diatomaceous earth, clay, fly ash, silicon carbide, manganese dioxide, calcium stearate and water in step (1) is (2-3): (1-2): (3-6): (2-3): (0.2-1): (0.1-0.5): (10-15).

4. The method for preparing a high-hardness machine tool casting according to claim 2, characterized in that: The temperature of the preheating treatment in step (2) is 300-400° C., and the time of the preheating treatment is 30-40 minutes; the temperature of the calcining treatment is 1000-1100° C., and the time of the calcining treatment is 15-25 minutes.

5. The method for preparing a high-hardness machine tool casting according to claim 1, characterized in that: In step S1, the temperature is raised to 1100-1200°C, and then continued to be raised to 1500-1600°C; the temperature out of the furnace is 1450-1500°C.

6. The method for preparing a high-hardness machine tool casting according to claim 1, characterized in that: The casting temperature in step S2 is 1350-1400°C.

7. The method for preparing a high-hardness machine tool casting according to claim 1, characterized in that: The recarburizer is a graphite recarburizer, and the inoculant is composed of a silicon-barium inoculant and a 75% silicon-iron inoculant in a mass ratio of (2-3):

1.

8. The method for preparing a high-hardness machine tool casting according to claim 1, characterized in that: The particle size of the copper-beryllium master alloy is 300-400 meshes.

9. A high hardness machine tool casting, characterized in that: The high-hardness machine tool casting is prepared by the preparation method of any one of claims 1 to 8.