A 20CrMnMo smelting vacuum casting process

Abstract

The present invention relates to the field of steel processing, and discloses a vacuum casting process for 20CrMnMo smelting, which includes the following steps: (1) adding steel raw materials into a vacuum induction furnace, and keeping warm after the steel raw materials turn red; (2) melting the steel raw materials into molten steel; (3) adding aluminum ingots; (4) refining treatment; (5) obtaining solid materials; (6) adjusting the components in the molten steel; (7) pouring the obtained finished molten steel into a mold, and waiting for cooling and shaping, then it is done. The performance of the 20CrMnMo steel obtained by the smelting and casting process of the present invention has been greatly improved, the microstructure and properties of the 20CrMnMo steel have been significantly improved, there are fewer inclusions inside the 20CrMnMo steel, effectively reducing the influence of inclusions on the performance of the 20CrMnMo steel. At the same time, through significant improvement, the performance of the 20CrMnMo steel in many aspects has been improved, broadening its application fields.

Description

Technical Field

[0001] The present invention relates to the field of steel processing, and specifically to a vacuum casting process for smelting 20CrMnMo steel. Background Art

[0002] In recent years, with the continuous development of the industry, especially the rapid development of industries such as automobiles, wind power, high-speed railways, and public infrastructure, the steel industry has also developed rapidly. However, due to many defects in product design, process development, etc., the subsequent development of the steel industry has been relatively slow, and the products produced by existing processes can no longer meet the needs of multiple fields in the market. Therefore, it is necessary to further improve the existing processes.

[0003] In the prior art, 20CrMnMo steel is a carburizing and quenching gear steel widely used in the domestic manufacturing industry. How to improve the melting process of 20CrMnMo steel in order to further improve the quality of its products is a technical problem that needs to be solved currently.

[0004] Based on this, we have proposed a vacuum casting process for smelting 20CrMnMo steel, hoping to solve the deficiencies in the prior art. Summary of the Invention

[0005] (1) Technical Problems to be Solved

[0006] In view of the deficiencies of the prior art, the present invention provides a vacuum casting process for smelting 20CrMnMo steel.

[0007] (2) Technical Solutions

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A vacuum casting process for smelting 20CrMnMo steel includes the following steps:

[0010] (1) Add steel raw materials to a vacuum induction furnace, evacuate the air, then supply power to increase the temperature. After the steel raw materials turn red, keep them at a constant temperature for 10 - 20 minutes;

[0011] (2) After keeping the temperature constant, continue to increase the power supply until the steel raw materials melt into molten steel;

[0012] (3) Add aluminum ingots to the molten steel after melting, and stir for 30 - 40 minutes;

[0013] (4) Adjust the vacuum degree in the vacuum induction furnace again, adjust the temperature in the vacuum induction furnace to 1580 - 1610 °C, carry out refining treatment, and perform electromagnetic stirring treatment for 22 - 25 minutes;

[0014] (5) Cut off the power supply of the vacuum induction furnace, and wait for the molten steel to cool and solidify to obtain solid materials;

[0015] (6) First, adjust the vacuum degree inside the vacuum induction furnace, then apply electricity and adjust the temperature to 1590 - 1640 °C. Reheat the solid materials until they melt, adjust the composition of the molten steel, add ferrosilicon chromium, ferromolybdenum, and calcium silicide, and then continue stirring for 1 - 2 hours to obtain the finished molten steel;

[0016] (7) Pour the obtained finished molten steel into a mold and wait for it to cool and solidify.

[0017] As a further technical solution, in step (1), when applying electricity and raising the temperature to reach 600 - 610 °C, the iron and steel raw materials show a dark red color.

[0018] As a further technical solution, in step (1), the vacuum is pumped to a vacuum degree of 3 - 5 Pa.

[0019] As a further technical solution: In step (2), increase the power supply to raise the temperature inside the vacuum induction furnace to 1530 - 1550 °C.

[0020] As a further technical solution: In step (4), adjust the vacuum degree inside the vacuum induction furnace to 1 - 1.8 Pa again.

[0021] As a further technical solution, the refining treatment is to add a refining agent to the molten steel inside the vacuum induction furnace;

[0022] The refining agent includes calcium oxide and alumina.

[0023] As a further technical solution, the mass ratio of calcium oxide to alumina is 1:3.

[0024] As a further technical solution: In step (6), adjust the vacuum degree inside the vacuum induction furnace to 0.1 - 0.4 Pa.

[0025] As a further technical solution: In the finished molten steel in step (6), by weight percentage, it includes: silicon 0.20 - 0.22%, phosphorus 0.015 - 0.017%, sulfur 0.020 - 0.022%, aluminum 0.025 - 0.028%, chromium 1.21 - 1.24%, carbon 0.20 - 0.23%, manganese 0.92 - 1.14%, molybdenum 0.23 - 0.25%, and the rest is iron.

[0026] As a further technical solution, during the pouring in step (7), control the temperature at 1410 - 1440 °C.

[0027] Through multiple adjustments of the vacuum degree during the smelting process, the present invention can effectively promote the formation of a continuous solid solution between chromium and iron, thereby narrowing the austenite phase region. Moreover, it can also promote the formation of various carbides between chromium and carbon, further enhancing the affinity with carbon.

[0028] Through the smelting treatment in the present invention, the decomposition rate of austenite can be effectively slowed down, and the hardenability of 20CrMnMo steel can be further improved. However, it also increases the tendency of temper brittleness of 20CrMnMo steel, facilitating the subsequent heat treatment of 20CrMnMo steel.

[0029] The strength and hardness of the 20CrMnMo steel obtained after smelting and casting according to the present invention are significantly improved.

[0030] During the smelting process, by continuously lowering the vacuum degree in the vacuum induction furnace at different stages, the present invention can effectively improve the ductile-brittle transition temperature of 20CrMnMo steel.

[0031] Through the smelting treatment of the present invention, the hardenability of 20CrMnMo steel can be improved, and various chromium-containing carbides can be formed, thus significantly improving the wear resistance of 20CrMnMo steel.

[0032] (III) Beneficial effects

[0033] Compared with the prior art, the present invention provides a 20CrMnMo smelting vacuum casting process, which has the following beneficial effects:

[0034] The performance of the 20CrMnMo steel obtained by the smelting and casting process of the present invention is greatly improved, the microstructure and properties of 20CrMnMo steel are significantly improved, there are fewer inclusions inside 20CrMnMo steel, effectively reducing the influence of inclusions on the performance of 20CrMnMo steel. At the same time, through significant improvement, the performance of 20CrMnMo steel in many aspects is improved, broadening its application fields. Specific embodiments

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention. Embodiment 1

[0036] A 20CrMnMo smelting vacuum casting process includes the following steps:

[0037] (1) Add steel raw materials to a vacuum induction furnace, evacuate to a vacuum degree of 3 Pa, then supply power to increase the temperature by 600 °C. The steel raw materials turn dark red, and keep warm for 10 min;

[0038] (2) After keeping warm, continue to increase the power supply to raise the temperature in the vacuum induction furnace to 1530 °C until the steel raw materials melt into molten steel;

[0039] (3) Add aluminum ingots to the molten steel after melting, and stir for 30 min;

[0040] (4) Adjust the vacuum degree in the vacuum induction furnace to 1 Pa again, adjust the temperature in the vacuum induction furnace to 1580 °C, carry out refining treatment, and perform electromagnetic stirring treatment for 22 min; The refining treatment is to add a refining agent to the molten steel in the vacuum induction furnace;

[0041] The refining agent includes calcium oxide and aluminum oxide; The mass ratio of calcium oxide to aluminum oxide is 1:3;

[0042] (5) Cut off the power supply of the vacuum induction furnace, wait for the molten steel to cool and solidify to obtain solid materials;

[0043] (6) First, adjust the vacuum degree in the vacuum induction furnace to 0.1 Pa, then supply power, adjust the temperature to 1590 °C, reheat the solid materials to melt, adjust the components in the molten steel, add ferrochromium, ferromolybdenum, and calcium silicate, and then continue to stir for 1 hour to obtain finished molten steel; The finished molten steel includes by weight percentage: silicon 0.20%, phosphorus 0.015%, sulfur 0.020%, aluminum 0.025%, chromium 1.21%, carbon 0.20%, manganese 0.92, molybdenum 0.23%, and the rest is iron.

[0044] (7) Pour the obtained finished molten steel into a mold, and the pouring temperature is 1410 °C. Wait for it to cool and solidify, and that's it. Example 2

[0045] A 20CrMnMo smelting vacuum casting process, including the following steps:

[0046] (1) Add steel raw materials to a vacuum induction furnace, evacuate to a vacuum degree of 3.5 Pa, then supply power to increase the temperature by 605 °C. The steel raw materials turn dark red, and keep warm for 12 min;

[0047] (2) After keeping warm, continue to increase the power supply to raise the temperature in the vacuum induction furnace to 1535 °C until the steel raw materials melt into molten steel;

[0048] (3) Add aluminum ingots to the molten steel after melting, and stir for 32 min;

[0049] (4) Adjust the vacuum degree in the vacuum induction furnace to 1.2 Pa again, adjust the temperature in the vacuum induction furnace to 1590 °C, carry out refining treatment, and perform electromagnetic stirring treatment for 24 min; the refining treatment is to add a refining agent to the molten steel in the vacuum induction furnace;

[0050] The refining agent includes calcium oxide and alumina; the mass ratio of calcium oxide to alumina is 1:3;

[0051] (5) Cut off the power supply of the vacuum induction furnace, wait for the molten steel to cool and solidify to obtain a solid material;

[0052] (6) First, adjust the vacuum degree in the vacuum induction furnace to 0.2 Pa, then energize, adjust the temperature to 1610 °C, reheat the solid material to melting, adjust the components in the molten steel, add ferrosilicon chromium, ferromolybdenum, and calcium silicide, and then continue stirring for 1.5 hours to obtain finished molten steel; the finished molten steel includes by weight percentage: silicon 0.21%, phosphorus 0.017%, sulfur 0.021%, aluminum 0.026%, chromium 1.24%, carbon 0.20%, manganese 0.98, molybdenum 0.24%, and the rest is iron.

[0053] (7) Pour the above-mentioned obtained finished molten steel into a mold, the pouring temperature is 1420 °C, and wait for it to cool and solidify. Example 3

[0054] A 20CrMnMo smelting vacuum casting process includes the following steps:

[0055] (1) Add iron and steel raw materials to the vacuum induction furnace, evacuate to a vacuum degree of 4 Pa, then energize and raise the temperature by 608 °C. The iron and steel raw materials turn dark red and are kept warm for 15 min;

[0056] (2) After heat preservation, continue to increase the power supply to make the temperature in the vacuum induction furnace reach 1545 °C until the iron and steel raw materials melt into molten steel;

[0057] (3) Add aluminum ingots to the molten steel after melting and stir for 35 min;

[0058] (4) Adjust the vacuum degree in the vacuum induction furnace to 1.2 Pa again, adjust the temperature in the vacuum induction furnace to 1590 °C, carry out refining treatment, and perform electromagnetic stirring treatment for 24 min; the refining treatment is to add a refining agent to the molten steel in the vacuum induction furnace;

[0059] The refining agent includes calcium oxide and alumina; the mass ratio of calcium oxide to alumina is 1:3;

[0060] (5) Cut off the power supply of the vacuum induction furnace, wait for the molten steel to cool and solidify to obtain a solid material;

[0061] (6) First, adjust the vacuum degree in the vacuum induction furnace to 0.2 Pa, then energize, adjust the temperature to 1620 °C, reheat the solid material to melting, adjust the composition in the molten steel, add ferrochrome, ferromolybdenum, and calcium silicate, and then continue stirring for 1.5 hours to obtain the finished molten steel; the finished molten steel includes, by weight percentage: silicon 0.21%, phosphorus 0.016%, sulfur 0.020%, aluminum 0.026%, chromium 1.22%, carbon 0.23%, manganese 0.95, molybdenum 0.24%, and the rest is iron.

[0062] (7) Pour the above-obtained finished molten steel into a mold, and the pouring temperature is 1430 °C. Wait for it to cool and solidify, then it's done. Example 4

[0063] A 20CrMnMo smelting vacuum casting process includes the following steps:

[0064] (1) Add iron and steel raw materials to the vacuum induction furnace, evacuate to a vacuum degree of 5 Pa, then energize and raise the temperature by 610 °C. The iron and steel raw materials turn dark red and are kept warm for 20 min;

[0065] (2) After heat preservation, continue to increase the power supply to make the temperature in the vacuum induction furnace reach 1550 °C until the iron and steel raw materials melt into molten steel;

[0066] (3) Add aluminum ingots to the molten steel after melting and stir for 40 min;

[0067] (4) Adjust the vacuum degree in the vacuum induction furnace to 1.8 Pa again, adjust the temperature in the vacuum induction furnace to 1610 °C, carry out refining treatment, and perform electromagnetic stirring treatment for 25 min; the refining treatment is to add a refining agent to the molten steel in the vacuum induction furnace;

[0068] The refining agent includes calcium oxide and aluminum oxide; the mass ratio of calcium oxide to aluminum oxide is 1:3;

[0069] (5) Cut off the power supply of the vacuum induction furnace and wait for the molten steel to cool and solidify to obtain solid materials;

[0070] (6) First, adjust the vacuum degree in the vacuum induction furnace to 0.4 Pa, then energize, adjust the temperature to 1640 °C, reheat the solid material to melting, adjust the composition in the molten steel, add ferrochrome, ferromolybdenum, and calcium silicate, and then continue stirring for 2 hours to obtain the finished molten steel; the finished molten steel includes, by weight percentage: silicon 0.22%, phosphorus 0.017%, sulfur 0.022%, aluminum 0.028%, chromium 1.24%, carbon 0.23%, manganese 1.14%, molybdenum 0.25%, and the rest is iron.

[0071] (7) Pour the above-obtained finished molten steel into a mold, and the pouring temperature is 1440 °C. Wait for it to cool and solidify, then it's done.

[0072] Comparative Example 1

[0073] Based on Example 1, in step (4), the degree of vacuum is not adjusted, and the remaining technical solutions are the same as those of Example 1.

[0074] Comparative Example 2

[0075] Based on Example 1, in step (6), the degree of vacuum is not adjusted, and the remaining technical solutions are the same as those of Example 1.

[0076] Test

[0077] The samples of the examples and comparative examples were detected and compared to see if the metallographic structure conforms to the second group rating in GB / T 13320-2007:

[0078] Table 1

[0079]

[0080] As can be seen from Table 1, the 20CrMnMo obtained by the present invention conforms to the second group rating in GB / T 13320-2007. During the smelting process of the present invention, the regulation of the degree of vacuum can significantly improve the metallographic structure of 20CrMnMo steel.

[0081] The hardness of the samples of the examples and comparative examples was detected and compared:

[0082] Table 2

[0083]

[0084] As can be seen from Table 2, the 20CrMnMo steel obtained by the process of the present invention has a higher hardness, and its wear resistance is further improved by the increase in hardness.

[0085] The tensile properties of the samples of the examples and comparative examples were detected with reference to GB / T228.1-2010 Metallic materials - Tensile testing:

[0086] Table 3

[0087]

[0088] As can be seen from Table 3, the tensile properties of the 20CrMnMo steel cast by the process of the present invention have been improved to a certain extent.

[0089] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A vacuum casting process for 20CrMnMo smelting, characterized in that, It includes the following steps: (1) Add steel raw materials into a vacuum induction furnace, evacuate to a vacuum degree of 3 - 5 Pa, then supply power to increase the temperature. After the steel raw materials turn red, keep warm for 10 - 20 min; (2) After keeping warm, continue to increase the power supply until the steel raw materials melt into molten steel; (3) Add aluminum ingots into the molten steel after melting, and stir for 30 - 40 min; (4) Adjust the vacuum degree in the vacuum induction furnace to 1 - 1.8 Pa again, adjust the temperature in the vacuum induction furnace to 1580 - 1610 °C, conduct refining treatment, and perform electromagnetic stirring treatment for 22 - 25 min; (5) Cut off the power supply of the vacuum induction furnace, wait for the molten steel to cool and solidify to obtain solid materials; (6) First, adjust the vacuum degree in the vacuum induction furnace to 0.1 - 0.4 Pa, then supply power, adjust the temperature to 1590 - 1640 °C, reheat the solid materials to melt, adjust the components in the molten steel, add ferrochrome, ferromolybdenum, calcium silicate, and then continue to stir for 1 - 2 hours to obtain finished molten steel; (7) Pour the above - obtained finished molten steel into a mold, and wait for it to cool and solidify, then it's done.

2. The 20CrMnMo smelting vacuum casting process according to claim 1, wherein In step (1), the temperature is increased by supplying power until it reaches 600 - 610 °C, and the steel raw materials are dark red.

3. A 20CrMnMo smelting vacuum casting process according to claim 1, characterized in that: In step (2), the power supply is increased until the temperature in the vacuum induction furnace reaches 1530 - 1550 °C.

4. A 20CrMnMo smelting vacuum casting process according to claim 1, characterized in that, The refining treatment is to add a refining agent into the molten steel in the vacuum induction furnace; The refining agent includes calcium oxide and aluminum oxide.

5. A 20CrMnMo smelting vacuum casting process according to claim 4, characterized in that, The mass ratio of calcium oxide to aluminum oxide is 1:

3.

6. A 20CrMnMo smelting vacuum casting process according to claim 1, characterized in that: In step (6), the finished molten steel includes by weight percentage: silicon 0.20 - 0.22%, phosphorus 0.015 - 0.017%, sulfur 0.020 - 0.022%, aluminum 0.025 - 0.028%, chromium 1.21 - 1.24%, carbon 0.20 - 0.23%, manganese 0.92 - 1.14%, molybdenum 0.23 - 0.25%, and the rest is iron.

7. A 20CrMnMo smelting vacuum casting process according to claim 1, characterized in that During pouring in step (7), the temperature is controlled at 1410 - 1440 °C.

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