Heat treatment process method of GCr15SiMn steel bearing part
Through the process of layered placement and isolation with heat-resistant steel mesh pads, combined with protective atmosphere roller hearth furnace quenching, salt bath cooling and high-temperature tempering, the problems of uneven heat conduction and excessive retained austenite content in GCr15SiMn steel bearing parts during heat treatment were solved, thereby improving the dimensional stability and wear resistance of the bearings.
Patent Information
- Application Number
- CN202511010123.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-22
- Publication Date
- 2025-09-23
AI Technical Summary
During the heat treatment process, GCr15SiMn steel bearing parts have problems such as uneven heat conduction, hardness deviation, uneven structure and excessive retained austenite content, which leads to reduced product precision and shortened service life.
The process of layered placement and isolation with heat-resistant steel mesh pads is adopted, combined with protective atmosphere roller hearth furnace quenching, salt bath cooling, cold treatment and high-temperature salt bath tempering to ensure the uniformity of heat treatment and control of retained austenite content.
The uniformity of heat treatment of bearing parts and the reduction of retained austenite content are achieved, which ensures the dimensional stability and wear resistance of the bearings and improves the service life and precision of the products.
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Figure CN120683343A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of bearing parts, in particular to a heat treatment process method for a GCr15SiMn steel bearing part. Background Art
[0002] Bearing components include inner and outer rings and rolling elements. Currently, approximately 90% of bearings on the market are made from GCr15 high-carbon chromium bearing steel. After heat treatment, GCr15 steel bearing components typically have a retained austenite content of less than 15%, while precision bearings typically have a retained austenite content of less than 5%. However, due to the limited hardenability of GCr15 steel, some thicker products fail to meet the relevant physical and chemical indicators after heat treatment, making them unsuitable for complex bearing applications. Therefore, GCr15SiMn steel, with its improved hardenability, is required.
[0003] GCr15SiMn steel, as a high-hardenability bearing steel, is widely used in the manufacture of large, heavy-loaded bearing parts. However, after conventional heat treatment, the retained austenite content in GCr15SiMn steel bearing parts generally exceeds 20%. Retained austenite is a metastable phase. A high retained austenite content will cause structural transformation during grinding and bearing use, resulting in changes in product dimensional accuracy, scrap during grinding, and reduced precision of finished bearings, resulting in a shortened bearing service life.
[0004] At present, the quenching and tempering treatment of such parts mostly adopts traditional box furnaces or ordinary roller hearth furnace production lines. In the traditional tooling, the rings are stacked tightly or without layered isolation, resulting in uneven heat conduction during heating. The cooling speed of the contact parts between the parts in the quenching and cooling stage varies greatly, which is prone to hardness deviation and uneven structure (local coarse martensite), affecting the consistency of bearing wear resistance.
[0005] In addition, GCr15 steel bearing parts with generally smaller size and thinner wall thickness adopt cold treatment process and low temperature tempering process after quenching to meet the requirements of hardness, microstructure and retained austenite content in accordance with the standards. However, it is difficult for GCr15SiMn steel bearing parts to meet the quality requirements using the above process.
[0006] Based on the above problems, a heat treatment process method for GCr15SiMn steel bearing parts is proposed. Summary of the Invention
[0007] The purpose of the present invention is to provide a heat treatment process method for GCr15SiMn steel bearing parts to solve the problems in the background technology.
[0008] To achieve the above object, the present invention provides a heat treatment process for a GCr15SiMn steel bearing part, comprising the following steps:
[0009] S1. Place the GCr15SiMn steel bearing parts after turning in a heat-resistant steel tooling. Specifically, place the rings in the heat-resistant steel tooling according to the process requirements, separate each layer of rings with a heat-resistant steel mesh pad, and place the rolling elements in a single layer upright in the heat-resistant steel tooling;
[0010] S2. The placed bearing parts enter the pre-cleaning station for cleaning, and then are moved into a protective atmosphere roller hearth furnace for quenching and heating under the protective atmosphere;
[0011] S3, transferring the heated bearing parts into a salt bath tank for salt bath cooling, followed by air cooling;
[0012] S4. After cooling, the bearing parts are cleaned and rust-proofed, and the finished bearing parts are transferred to a deep freezer for cold treatment;
[0013] S5. Finally, the cold-treated bearing parts are tempered in a high-temperature salt bath to complete the treatment.
[0014] Preferably, in S1, the number of layers of the rings is 1 to 3, the size of the heat-resistant steel mesh pad is 5 to 10 mm smaller than the size of the heat-resistant steel tooling, the heat-resistant steel mesh pad is made of heat-resistant steel wire with a diameter of 2.5 to 3.5 mm, and the mesh size is 25 to 35 mm.
[0015] Preferably, in S2, the cleaning process is cleaning with a detergent and cleaning with clean water, the cleaning temperature is 50-80°C, and the two cleaning times are 8-10 minutes. After cleaning, drying is performed, the drying temperature is 100-150°C, and the drying time is 8-10 minutes.
[0016] Preferably, in S2, the protective atmosphere is a mixed atmosphere of nitrogen, methanol dripping and propane, the mass ratio of nitrogen, methanol and propane is 48:2:1, the furnace pressure is 150-220 MPa, and the carbon potential in the furnace is 0.65-0.9.
[0017] Preferably, in S2, the quenching temperature is 820-840° C., and the heating time is 60-80 min.
[0018] Preferably, in S3, the salt bath temperature is 160-190° C., the water content in the salt bath is 0.6-1.2%, and the time is 8-10 minutes.
[0019] Preferably, in said S4, the steps of cleaning and rust prevention treatment are:
[0020] 1) Ultrasonic cleaning: ultrasonic frequency is 28-39KHZ, water temperature is 40-60℃, and time is 8-10min;
[0021] 2) Foaming cleaning: water temperature is 40-60℃, time is 8-10 minutes;
[0022] 3) Anti-rust treatment: at room temperature, use an aqueous solution containing 0.5-0.8% sodium nitrite.
[0023] Preferably, in S4, the temperature in the cryogenic box is (-70) to (-196)°C for 100 to 120 minutes; after the cold treatment, the temperature in the cryogenic box is slowly raised to room temperature. Preferably, in S5, the tempering temperature is 200 to 230°C for 210 to 270 minutes.
[0024] Preferably, in said S5, the retained austenite content of the bearing part after the treatment is less than 5%, which can ensure that the bearing has higher dimensional stability during later use.
[0025] Therefore, the heat treatment process of a GCr15SiMn steel bearing part of the present invention has the following beneficial effects:
[0026] (1) In the present invention, the gaps between each layer of rings are uniform and contactless by adopting layered placement and isolation by heat-resistant steel mesh pads of specific specifications, thereby ensuring that the heat flow distribution during heating is consistent and the salt bath can fully wrap the surface of the part during the quenching stage; and the cutting fluid, dust, oil and other impurities remaining on the surface of the rings are removed by double-station pre-heating cleaning to ensure the consistent appearance color of the rings after quenching and tempering; the carbon potential and furnace pressure in the furnace are precisely controlled under the protective atmosphere of "nitrogen, methanol dripping, and propane", and a stable carburized equilibrium layer is formed on the surface of the part during high-temperature heating, which effectively prevents surface oxidation and decarburization, suppresses surface defects, and provides a good foundation for subsequent processes.
[0027] (2) The present invention adds a cold treatment process between cleaning and rust prevention and tempering, which can reduce the residual austenite content in the GCr15SiMn steel bearing parts after quenching through the cold treatment process; after the cold treatment is completed, a high-temperature tempering process is used instead of a low-temperature tempering process to further reduce the residual austenite content in the GCr15SiMn steel bearing parts after quenching, and the residual austenite content is reduced to within 5%, meeting the technical requirements of precision products, and ensuring that the bearings have higher dimensional stability during later use.
[0028] (3) After the cold treatment process and high-temperature tempering process are adopted in the present invention, the surface hardness of the GCr15SiMn steel bearing parts is similar to that of the conventional process, which ensures the wear resistance of the bearing products. At the same time, according to the actual use conditions of the bearing products, such as impact resistance conditions, the hardness of the bearing parts can be reduced by increasing the tempering temperature, thereby making the bearing parts more tough. In addition, the salt bath high-temperature tempering is used instead of the air tempering furnace. The salt bath has a large heat capacity and can provide a higher heating speed. The salt bath has a uniform temperature distribution and uniform heating, which can make the bearing parts more fully tempered.
[0029] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 This is the microstructure diagram of the inner ring of 22328CA after treatment in an embodiment of the present invention. DETAILED DESCRIPTION
[0031] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.
[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.
[0033] Example
[0034] In this embodiment, the inner ring of the GCr15SiMn steel spherical roller bearing 22328CA is processed using a 750 roller hearth furnace salt bath martensite quenching production line with a protective atmosphere produced by Tangshan Yajie, specifically including the following steps:
[0035] S1. Place the GCr15SiMn steel bearing parts after turning in a heat-resistant steel tooling. Specifically, place the 22328CA rings in the heat-resistant steel tooling according to the process requirements. The number of layers is 2, with 9 rings placed on the bottom layer and 6 rings placed on the top layer. There is a gap between the rings on each layer so that they cannot touch each other. A heat-resistant steel mesh pad is used to separate the two layers of rings. The mesh pad size (length and width) is 700mm × 700mm. The mesh pad is made of heat-resistant steel wire with a diameter of 3.0mm and a small mesh size of 30mm. The rolling elements are placed in a single layer upright in the heat-resistant steel tooling.
[0036] S2. The placed bearing parts enter the front cleaning station for cleaning. First, they are cleaned with detergent for 10 minutes at 60°C, then rinsed with clean water for 10 minutes at 60°C. After cleaning, they are dried at 130°C for 10 minutes to remove impurities such as cutting fluid, dust, and oil on the surface of the rings, ensuring that the appearance and color of the rings are consistent after quenching and tempering.
[0037] The product was then transferred to a protective atmosphere roller hearth furnace and placed in a mixed protective atmosphere of nitrogen, methanol dripping, and propane. The mass ratio of nitrogen, methanol dripping, and propane was controlled to be 48:2:1, and the furnace pressure was controlled to be 200 MPa. The carbon potential CP% in the furnace was set to 0.7. The product was then quenched and heated at 830°C for 70 minutes.
[0038] S3. After heating, the bearing parts are transferred into the salt bath for salt bath cooling. The moving table is started to move up and down, and the stirring motor of the salt bath is controlled to start to enhance the fluidity of the salt bath and improve the salt cooling performance. During this process, the salt temperature is controlled at 180°C, the water content in the salt bath is 1.0%, and the cooling time is 10 minutes.
[0039] Then, air cooling is carried out. There are three air cooling stations in total. The air cooling time at each station is 10 minutes. Ensure that the surface temperature of the ring is ≤50℃ after air cooling.
[0040] S4. After cooling, the bearing parts are cleaned and treated for rust prevention. The entire process adopts immersion cleaning. First, ultrasonic cleaning is performed at a controlled frequency of 28KHZ and a water temperature of 50°C. Then, foaming cleaning is performed at a water temperature of 50°C. Finally, at room temperature, an aqueous solution containing 0.8% sodium nitrite is used for rust prevention.
[0041] The treated bearing parts are transferred to a cryogenic box for cold treatment at a temperature of -80°C for 120 minutes. After the cold treatment, the liquid nitrogen is turned off and the temperature of the cryogenic box is controlled to slowly rise to room temperature, so that the core surface temperature of the bearing parts returns to room temperature.
[0042] S5. Finally, use Tangshan Yajie 850 isothermal salt bath to perform salt bath high temperature tempering at a tempering temperature of 220°C for 240 minutes to obtain heat-treated bearing parts.
[0043] The final bearing parts were inspected, and their microstructure diagrams are shown as follows: Figure 1 As shown, the martensite structure is level 3 and the troostite structure is less than level 1.
[0044] Comparative Example
[0045] This comparative example is based on the processing of the inner ring of the spherical roller bearing 22328CA made of GCr15SiMn steel, as follows:
[0046] S1. Place the GCr15SiMn steel bearing parts after turning in a heat-resistant steel fixture. Specifically, place the 22328CA rings in the heat-resistant steel fixture according to the process requirements. Place the rings in two layers, with 9 rings on the bottom layer and 6 rings on the top layer. Leave gaps between the rings on each layer to prevent them from touching each other. Place the rolling elements in a single layer upright in the heat-resistant steel fixture.
[0047] S2. The bearing parts are placed in the front cleaning station for cleaning. First, they are cleaned with detergent for 10 minutes at a temperature of 60°C, then rinsed with clean water for 10 minutes at a temperature of 60°C. After cleaning, they are dried at a temperature of 130°C for 10 minutes.
[0048] The product was then transferred to a protective atmosphere roller hearth furnace and placed in a mixed protective atmosphere of nitrogen, methanol dripping, and propane. The mass ratio of nitrogen, methanol dripping, and propane was controlled to be 48:2:1, and the furnace pressure was controlled to be 200 MPa. The carbon potential CP% in the furnace was set to 0.7. The product was then quenched and heated at 830°C for 70 minutes.
[0049] S3. After heating, the bearing parts are transferred into the salt bath for salt bath cooling. The moving table is started to move up and down, and the stirring motor of the salt bath is controlled to start to enhance the fluidity of the salt bath and improve the salt cooling performance. During this process, the salt temperature is controlled at 180°C, the water content in the salt bath is 1.0%, and the cooling time is 10 minutes.
[0050] Then, air cooling is carried out. There are three air cooling stations in total. The air cooling time at each station is 10 minutes. Ensure that the surface temperature of the ring is ≤50℃ after air cooling.
[0051] S4. After cooling, the bearing parts are cleaned and treated for rust prevention. The whole process adopts immersion cleaning. First, ultrasonic cleaning is performed at a controlled frequency of 28KHZ and a water temperature of 50°C. Then, foaming cleaning is performed at a water temperature of 50°C. Finally, at room temperature, an aqueous solution containing 0.8% sodium nitrite is used for rust prevention.
[0052] S5. Finally, an air tempering furnace is used for tempering at a tempering temperature of 160° C. for 240 min to obtain a heat-treated bearing part.
[0053] The bearing parts obtained in the examples and comparative examples were tested for their performance, and the results are shown in Table 1 below.
[0054] Table 1 Performance test results
[0055]
[0056] Compared with the process of the comparative example, by adopting the heat treatment process method of this embodiment, the content of retained austenite in the bearing parts after heat treatment is less than 5%, which can ensure higher dimensional stability of the bearings during later use.
[0057] Therefore, the present invention provides a heat treatment process method for GCr15SiMn steel bearing parts, which uses a heat-resistant steel mesh pad to separate each layer of rings to improve the uniformity of heating and cooling of the parts, uses a protective atmosphere and accurately controls the carbon potential and furnace pressure in the furnace to effectively prevent surface oxidation and decarburization; the double-station heating cleaning for pre-cleaning and the subsequent immersion cleaning and rust prevention improve the cleaning cleanliness and rust prevention effect, salt bath cooling and deep cryogenic treatment are combined with high-temperature salt bath tempering to enhance dimensional stability, and the retained austenite content is reduced to less than 5%, meeting the technical requirements of precision products.
[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. A heat treatment process for GCr15SiMn steel bearing parts, characterized in that: The following steps are involved: S1. Place the GCr15SiMn steel bearing parts after turning in a heat-resistant steel tooling. Specifically, place the rings in the heat-resistant steel tooling according to the process requirements, separate each layer of rings with a heat-resistant steel mesh pad, and place the rolling elements in a single layer upright in the heat-resistant steel tooling; S2. The placed bearing parts enter the pre-cleaning station for cleaning, and then are moved into a protective atmosphere roller hearth furnace for quenching and heating under the protective atmosphere; S3, transferring the heated bearing parts into a salt bath tank for salt bath cooling, followed by air cooling; S4. After cooling, the bearing parts are cleaned and rust-proofed, and the finished bearing parts are transferred to a deep freezer for cold treatment; S5. Finally, the cold-treated bearing parts are tempered in a high-temperature salt bath to complete the treatment.
2. The heat treatment process for a GCr15SiMn steel bearing part according to claim 1, characterized in that: In S1, the number of layers of the rings is 1 to 3, the size of the heat-resistant steel mesh pad is 5 to 10 mm smaller than the size of the heat-resistant steel tooling, the heat-resistant steel mesh pad is made of heat-resistant steel wire with a diameter of 2.5 to 3.5 mm, and the mesh size is 25 to 35 mm.
3. The heat treatment process for a GCr15SiMn steel bearing component according to claim 1, characterized in that: In S2, the cleaning process includes cleaning with a detergent and cleaning with clean water, the cleaning temperature is 50-80°C, and the two cleaning times are 8-10 minutes. After cleaning, drying is performed, the drying temperature is 100-150°C, and the drying time is 8-10 minutes.
4. The heat treatment process for a GCr15SiMn steel bearing component according to claim 1, characterized in that: In the S2, the protective atmosphere is a mixed atmosphere of nitrogen, methanol and propane, the mass ratio of nitrogen, methanol and propane is 48:2:1, the furnace pressure is 150-220 MPa, and the carbon potential in the furnace is 0.65-0.
9.
5. The heat treatment process for a GCr15SiMn steel bearing component according to claim 1, characterized in that: In the step S2, the quenching temperature is 820-840° C., and the heating time is 60-80 min.
6. The heat treatment process for a GCr15SiMn steel bearing component according to claim 1, characterized in that: In the step S3, the salt bath temperature is 160-190° C., the water content in the salt bath is 0.6-1.2%, and the time is 8-10 minutes.
7. The heat treatment process for a GCr15SiMn steel bearing component according to claim 1, characterized in that: In said S4, the steps of cleaning and rust prevention are: 1) Ultrasonic cleaning: ultrasonic frequency is 28-39KHZ, water temperature is 40-60℃, and time is 8-10min; 2) Foaming cleaning: water temperature is 40-60℃, time is 8-10 minutes; 3) Anti-rust treatment: at room temperature, use an aqueous solution containing 0.5-0.8% sodium nitrite.
8. The heat treatment process for a GCr15SiMn steel bearing component according to claim 1, characterized in that: In the above-mentioned S4, the temperature in the deep freezer is (-70) to (-196)°C for 100 to 120 minutes. After the cold treatment is completed, the temperature of the deep freezer is slowly raised to room temperature.
9. The heat treatment process for a GCr15SiMn steel bearing component according to claim 1, characterized in that: In the step S5, the tempering temperature is 200-230° C., and the tempering time is 210-270 min.