A multi-gradient structure heat treatment process method for realizing wear-resistant and toughened bearing

Abstract

This application discloses a multi-gradient microstructure heat treatment process for achieving wear resistance and toughness enhancement in bearings, belonging to the field of bearing manufacturing. The steps are as follows: 1) Carbonitriding is performed on the bearing workpiece to form a continuous and gentle C and N composition gradient from the surface to the core. After carbonitriding, the workpiece is air-cooled; 2) Then, under a nitrogen protective atmosphere, the workpiece is austenitized through a three-stage heating process using a stepped heating method; 3) A gradient multiphase microstructure of martensite and bainite is constructed through isothermal quenching; wherein, the isothermal quenching time is based on the carbonitriding time and is precisely controlled according to the target bainite content, ultimately obtaining a bainite content of 10-20% on the surface and ≥60% in the core; 4) Finally, the workpiece is subjected to low-temperature tempering treatment to obtain a wear-resistant and toughened bearing. This invention achieves precise control of the multi-gradient heterogeneous microstructure, achieving wear resistance and toughness enhancement through the construction of a microstructure ratio gradient, meeting the synergistic performance requirements of high wear resistance on the bearing surface and impact resistance in the core.

Description

Technical Field

[0001] This invention belongs to the field of bearing manufacturing, and in particular relates to a multi-gradient heat treatment process for achieving wear resistance and toughening of bearings. Background Technology

[0002] Developing high-performance key components for high-end equipment is an important direction for adapting to the trend of green and low-carbon development and breaking through the industry's technological bottlenecks. Bearings, as the core basic component of power transmission systems, play a crucial role in rotational support, load bearing, and torque transmission. Their comprehensive performance and service life directly affect the operational stability and service reliability of equipment. Complex and harsh alternating loads and high-speed operating environments place stringent requirements on the surface wear resistance and core impact toughness of bearing materials. Furthermore, the various mechanical properties of bearings are closely related to their microstructure. Currently, surface strengthening methods such as carburizing / nitriding and ultrasonic shot peening are often used to improve bearing wear resistance, but the core remains martensite, resulting in low toughness. Isothermal quenching heat treatment is often used to introduce bainite to improve bearing toughness, but this sacrifices surface hardness and a certain degree of wear resistance.

[0003] Therefore, in the face of increasingly stringent service conditions, there is an urgent need to develop a heat treatment process to simultaneously improve the wear resistance of the bearing surface and the impact resistance of the bearing core. Summary of the Invention

[0004] In response to the above situation, this invention proposes a multi-gradient microstructure heat treatment process to achieve wear resistance and toughness enhancement of bearings. Through the synergistic effect of multiple processes such as composition gradient construction, grain gradient construction, gradient multiphase microstructure construction, and stable tempering, the multi-gradient heterogeneous microstructure can be precisely controlled. Wear resistance and toughness enhancement are achieved by constructing microstructure ratio gradients, thus meeting the synergistic performance requirements of high wear resistance on the bearing surface and impact resistance in the core.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A multi-gradient microstructure heat treatment process for achieving wear resistance and toughening of bearings is provided, comprising the following steps: 1) Carbonitriding is performed on the bearing workpiece to form a continuous and gentle gradient of C and N composition from the surface to the core. After carbonitriding, the workpiece is air-cooled. 2) Then, under a nitrogen protective atmosphere, the workpiece is heated in three stages using a stepped heating method to achieve austenitization; 3) Utilizing the influence of the compositional gradient constructed by carbonitriding on the kinetics of bainitic phase transformation, a gradient multiphase structure of martensite and bainite is constructed through isothermal quenching; wherein: the isothermal quenching time is based on the carbonitriding time and is controlled according to the target bainite content, ultimately obtaining a bainite content of 10~20% in the surface layer and ≥60% in the core; where the surface layer refers to the workpiece surface and the core refers to the part less than 2mm from the surface; 4) Finally, the workpiece is subjected to low-temperature tempering treatment to obtain wear-resistant and toughened bearings.

[0006] According to the above scheme, in step 1), the workpiece to be processed is cleaned to remove oil, rust and oxidation impurities attached to the surface of the workpiece, so as to ensure the surface cleanliness and provide a clean reaction interface for subsequent carbonitriding; the cleaned workpiece is loaded into the furnace, and then a vacuum is created and a protective gas is introduced to prevent the workpiece from oxidizing and decarburizing during high-temperature heating.

[0007] According to the above scheme, in step 1), carbonitriding includes a strong infiltration stage and a diffusion stage, wherein: During the strong infiltration stage, the carbon potential in the carbonitriding furnace is maintained at 1.10%~1.20%, and the ammonia flow rate is stabilized at 2.0~2.5 NL / min. The carbonitriding temperature is determined based on the material properties of the workpiece (the chemical composition C, Ni, Si, V, Mo and W), and the carbonitriding time is determined based on the required infiltration layer depth.

[0008] Preferably, the carbonitriding temperature T CN for:

[0009]

[0010] in, A c1 The critical temperature at which pearlite begins to transform into austenite upon heating, expressed in °C. T CN The carbonitriding temperature is expressed in °C; C, Ni, Si, V, Mo, and W represent the percentage of elements in the workpiece. The values ​​preceding the percentage are used in the formula for calculation. For example, if the C content is 0.9%, then the value of C in the formula is 0.9.

[0011] Preferably, the strong infiltration time t 1 is:

[0012] in, t 1 represents the strong infiltration time, in hours (h). T CN This is the carbonitriding temperature, expressed in °C. d The depth of the infiltration layer is expressed in μm. k 1 is a correction factor, which is taken as 0.9~1.2 depending on the initial carbon content of the workpiece.

[0013] Preferably, the infiltration layer depth is 500~800μm.

[0014] During the diffusion stage, after the carbon and nitrogen elements on the surface reach the expected enrichment concentration, the furnace temperature is kept basically unchanged, the carbon potential of the furnace gas is reduced to 0.9~1.0%, and the ammonia supply flow rate is reduced to 1.7~2.0 NL / min, which promotes the diffusion of excessively high concentrations of carbon and nitrogen atoms on the surface to the core of the ring, thereby forming a continuous and gentle composition gradient from the surface to the core.

[0015] Preferably, diffusion time t 2 is:

[0016] in, t 2 represents the diffusion time, in hours (h). t 1 represents the strong infiltration time, in hours (h). k 2 is a correction factor, which is taken as 0.8~1.5 according to the initial carbon content of the workpiece.

[0017] According to the above scheme, in step 2), the three-stage heating of the workpiece using a stepped heating method is specifically as follows: The first stage involves heating the workpiece to... T 1. Hold at the temperature for 20-30 minutes to reduce the temperature difference between the surface and core of the workpiece and decrease thermal stress; 2. Heat the workpiece to... T 2. Hold at this temperature for 30-40 minutes to increase the austenite nucleation rate on the surface of the workpiece with higher carbon content, forming a large number of dispersed fine austenite nuclei; 3. Heat the workpiece to... T 3. Hold at this temperature for 50-60 minutes to fully austenitize the workpiece; wherein:

[0018]

[0019]

[0020] in, T 1 represents the first stage heating temperature, in °C; T 2 represents the second stage heating temperature, in °C. T 3 represents the heating temperature of the third stage, in °C.

[0021] According to the above scheme, in step 3), the austenitized workpiece is quickly taken out and transferred to a constant temperature salt bath furnace, and stirred until the workpiece temperature is stable, and then isothermal quenching is performed.

[0022] According to the above scheme, in step 3), the isothermal quenching temperature is determined based on the material composition C, Cr, Mn and Mo; Preferably, the isothermal quenching temperature T B for:

[0023] in, T B The isothermal quenching temperature is expressed in °C; C, Cr, Mn, and Mo are the percentages of elements in the workpiece. The values ​​before the percentage are used in the formula for calculation. For example, if the C content is 0.9%, then the value of C in the formula is 0.9.

[0024] According to the above scheme, in step 3), the isothermal quenching time t B Calculated using the following formula:

[0025] in, f B The target surface bainite content; K This is a temperature-dependent constant, taken as 0.2~0.5; t B This refers to the isothermal quenching time, expressed in hours (h). n The transformation index is set at 1.1 to 1.3. η CN The time correction factor is calculated according to the following formula:

[0026] in, η CN This is a time correction factor; t 1 represents the strong infiltration time, in hours (h). t 2 represents diffusion time, in hours (h).

[0027] According to the above scheme, in step 4), the low-temperature tempering process is as follows: the tempering temperature is 150~170℃, the tempering time is 90~120min, and the workpiece is placed in the air to cool after tempering.

[0028] A wear-resistant and toughened bearing prepared using the above-mentioned heat treatment process is provided.

[0029] According to the above scheme, the surface wear rate of the bearing is 3×10⁻⁶. -6 mm 3 N -1 m -1 Below, the cardiac impact toughness is 8J / cm. 2 The above; preferably, the surface wear rate is 2×10. -6 ~3×10 -6 mm 3 N -1 m -1 The impact toughness of the heart is 8~9 J / cm. 2 .

[0030] This invention addresses the increasingly demanding service environments and extreme performance requirements of bearings by providing a multi-gradient heat treatment process for achieving wear resistance and toughness enhancement. First, a carbonitriding process establishes a continuous and gentle compositional gradient from the workpiece surface to its core, laying the foundation for subsequent grain and phase transformation gradients. Then, a multi-stage, step-by-step austenitization process utilizes the compositional difference between the workpiece surface and core to increase the austenite nucleation rate in the carbon-rich surface layer, forming numerous dispersed fine austenite nuclei. This refines the surface grains, creating a grain gradient that enhances surface wear resistance while simultaneously improving core toughness. Next, isothermal quenching introduces the toughening phase bainite. By adjusting the isothermal quenching process parameters based on the co-diffusion layer depth, precise control of the bainite content in the workpiece surface layer is achieved, constructing a wear-resistant surface layer with low bainite content (10-20%) and a high-bainite content (≥60%) high-toughness core. Finally, low-temperature tempering yields the wear-resistant and toughened bearing.

[0031] The beneficial effects of this invention are: This invention provides a multi-gradient microstructure heat treatment process for achieving wear resistance and toughening of bearings. It constructs a compositional gradient through carbonitriding, a grain gradient through step-by-step austenitization, and finally achieves a martensitic and bainitic gradient multiphase microstructure through isothermal quenching parameter adjustment. This precisely controls the martensite / bainite ratio in the workpiece surface and core, achieving a synergistic improvement in surface wear resistance and core impact resistance. This invention overcomes the performance bottleneck of traditional single wear resistance or toughening methods, achieving precise control of multi-gradient heterogeneous microstructures. By constructing a gradient in microstructure ratios, it achieves wear resistance and toughening, meeting the synergistic performance requirements of high wear resistance on the bearing surface and impact resistance in the core, and has significant application prospects. Attached Figure Description

[0032] Figure 1 The distribution of C and N elements with depth from the surface to the core of the workpiece in Example 1; Figure 2 The microstructure morphology of the surface and core of the workpiece in Example 1; Figure 3 This is a comparison of the surface grain size between Example 1 and Comparative Example 1. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0034] This invention provides a multi-gradient microstructure heat treatment process for achieving wear resistance and toughening of bearings, comprising the following steps: (1) Construction of composition gradient 1) Preparation stage: The workpiece to be processed is cleaned to remove oil, rust, and oxide impurities adhering to the surface, ensuring surface cleanliness and providing a clean reaction interface for subsequent carbonitriding. The cleaned workpiece is then placed into the furnace, and a vacuum is created by introducing a protective gas to prevent oxidation and decarburization of the workpiece during high-temperature heating.

[0035] 2) Strong Carburizing Stage: During carbonitriding, the carbon potential in the furnace is maintained at 1.10%~1.20%, the ammonia flow rate is stable at 2.0~2.5 NL / min, and the carbonitriding temperature is determined by the material properties (chemical composition C, Ni, Si, V, Mo, and W). (Formula 1) (Formula 2) in, A c1 It is the critical temperature (°C) at which pearlite begins to transform into austenite upon heating. T CN The carbonitriding temperature is ℃; C, Ni, Si, V, Mo and W are the percentages of elements in the workpiece. The values ​​before the percentage are used in the formula for calculation. For example, if the C content is 0.9%, then the value of C in the formula is 0.9.

[0036] The carbonitriding time is determined by the required infiltration depth, with a preferred infiltration depth of 500~800μm. (Formula 3) in, t 1 represents the strong infiltration time (h). T CN The carbonitriding temperature is ℃. d The depth of the infiltration layer (μm). k 1 is a correction factor, which is taken as 0.9~1.2 depending on the initial carbon content of the workpiece.

[0037] 3) Diffusion Stage: After the surface carbon and nitrogen elements reach the expected enrichment concentration, the furnace temperature is kept basically constant, and the furnace gas carbon potential is reduced to 0.9%~1.0%, while the ammonia supply flow rate is reduced to 1.7-2.0 NL / min. This promotes the diffusion of excessively high concentrations of carbon and nitrogen atoms from the surface to the core of the ring, thus forming a continuous and gentle composition gradient from the surface to the core. The diffusion time is: (Formula 4) in, t 2 represents the diffusion time (h). t 1 represents the strong infiltration time (h). k 2 is a correction factor, ranging from 0.8 to 1.5 depending on the initial carbon content of the workpiece. The workpiece undergoes air cooling after carbonitriding.

[0038] (2) Grain gradient construction Step-by-step austenitizing is performed under a nitrogen protective atmosphere, using a stepped heating method to heat the workpiece in stages. The first stage heats the workpiece to [temperature value missing]. T 1. Hold at room temperature for 20 minutes to reduce the temperature difference between the surface and core of the workpiece and decrease thermal stress; 2. Heat the workpiece to... T 2. Hold at high temperature for 30 minutes to increase the austenite nucleation rate on the surface of the workpiece with higher carbon content, forming a large number of dispersed fine austenite nuclei; the third stage involves heating the workpiece to... T 3. Hold at the temperature for 50 minutes to allow the workpiece to be fully austenitized.

[0039] (Formula 5) (Formula 6) (Formula 7) in, T 1 represents the heating temperature (°C) of the first stage. T 2 represents the second stage heating temperature (°C). T 3 represents the heating temperature (°C) for the third stage.

[0040] (3) Construction of gradient multiphase organization After austenitization, the workpiece is quickly removed and transferred to a constant-temperature salt bath furnace, where it is stirred until the workpiece temperature stabilizes. The influence of the compositional gradient established by carbonitriding on the bainitic phase transformation kinetics is utilized to construct a gradient multiphase microstructure. The isothermal quenching temperature is determined based on the material's C, Cr, Mn, and Mo content. (Formula 8) in, T B The isothermal quenching temperature is denoted as C; C, Cr, Mn, and Mo are the percentages of elements in the workpiece. The values ​​before the percentage in the formula are used for calculation. For example, if the C content is 0.9%, then the value of C in the formula is 0.9.

[0041] Since the bainitic phase transformation kinetics are related to carbon content, the isothermal quenching time can be precisely controlled based on the carbonitriding time and the target bainite content, in order to obtain a bainite content of 10-20% on the surface and ≥60% in the core (where the surface refers to the workpiece surface and the core refers to the part less than 2mm from the surface). (Formula 9) in, f B The target surface bainite content, K This is a temperature-dependent constant, ranging from 0.2 to 0.5. t B This refers to the isothermal quenching time.n The transformation index is set at 1.1 to 1.3. η CN The time correction factor is calculated according to the following formula: (Formula 10) in, η CN This is a time correction factor. t 1 represents the strong infiltration time (h). t 2 represents the diffusion time (h).

[0042] (4) Stable tempering: Finally, the workpiece is subjected to low-temperature tempering treatment at a temperature of 150~170℃ for 90~120 minutes. After tempering, the workpiece is placed in air to cool.

[0043] The following are specific implementation examples: Example 1 For a new energy vehicle bearing (8mm wall thickness) made of GGr15 steel, the bearing composition by mass percentage is: C: 0.95%; Si: 0.15%; Mn: 0.25%; Cr: 1.4%; Ni: 0.3%; Mo: 0.1%; V: 0%; W: 0%, with the balance being Fe and unavoidable impurities.

[0044] Its multi-gradient tissue heat treatment method includes the following steps: (1) Carbon-nitrogen co-infiltration-composition gradient construction The workpieces to be treated are cleaned to remove oil, rust, and oxide impurities from their surfaces, ensuring surface cleanliness. The cleaned workpieces are then placed in a furnace, followed by vacuuming and introducing a protective gas. Subsequently, a two-stage carbonitriding treatment, consisting of strong infiltration and diffusion, is performed sequentially. During the strong infiltration stage, the carbon potential inside the furnace was maintained at 1.1%, the ammonia flow rate was stabilized at 2.1 NL / min, and the infiltration depth was set to 800 μm. Based on formulas 1 and 2, the carbonitriding temperature was calculated to be 850℃; the infiltration depth d was 800 μm, and a correction factor was applied. k Taking 1 as an example, the strong infiltration time is calculated to be 6 hours according to Formula 3. Therefore, the furnace temperature is stably controlled at 850℃ and the heat preservation time is 6 hours.

[0045] During the diffusion stage, the furnace temperature remained constant, the carbon potential decreased to 0.9%, and the ammonia flow rate was adjusted to 2.0 NL / min; correction factor k 2 is taken as 1.3, and the diffusion time is calculated to be 1.5h according to Formula 4; therefore, the diffusion insulation time is set to 1.5h. After co-infiltration is completed, the workpiece is air-cooled.

[0046] (2) Multi-level step-type hierarchical austenitization—grain gradient construction Multi-stage stepwise austenitization was carried out under a nitrogen protective atmosphere. The temperatures for different stages were calculated according to formula 5-7 as follows: T1 was 500℃, T2 was 720℃, and T3 was 850℃. In the first stage, the workpiece was heated to 500℃ and held for 20 minutes. In the second stage, the workpiece was heated to 720℃ and held for 30 minutes. In the third stage, the workpiece was held at 850℃ for 50 minutes to achieve complete austenitization.

[0047] (3) Isothermal quenching-multiphase gradient construction After austenitization, the workpiece is quickly placed in a constant-temperature salt bath furnace and stirred until the workpiece temperature stabilizes. The isothermal quenching temperature is calculated according to Formula 8. f B =18%, temperature correlation constant is taken as 0.3, transformation index n is taken as 1.3, and isothermal quenching time is calculated according to formulas 9 and 10; the isothermal quenching temperature is found to be 240℃ and the isothermal quenching time is 42min. The bainite content is obtained as 18% on the surface and 60% in the core.

[0048] (4) Stable tempering The quenched workpiece is subjected to low-temperature tempering at 160℃ for 120 minutes. After the tempering is completed, the workpiece is placed in air to cool.

[0049] Microstructural observation of the workpieces obtained in the above examples revealed that the workpieces formed multiple heterogeneous structures, with carbon and nitrogen concentrations decreasing with increasing depth, forming a gradient compositional distribution. Figure 1 The volume fraction of bainite increases with depth, with 18% bainite content in the surface layer and 60% in the core layer. Figure 2 ).

[0050] Mechanical property tests were performed on the workpiece, and the surface wear rate was 2.3 × 10⁻⁶. -6 mm 3 N -1 m -1 Core impact toughness (U-notch): 8.4 J / cm 2 The surface wear rate of the workpiece obtained in the above examples is 68.5% lower than that of traditional heat treatment (i.e., austenitization of the billet at 850℃ followed by martensitic quenching), and the core impact toughness is 30% higher than that of traditional heat treatment. This demonstrates that the gradient multiphase microstructure precisely controlled heat treatment process of this invention achieves multi-gradient microstructure construction from the bearing surface to the core, thereby meeting the stringent service requirements of high wear-resistant and impact-resistant bearings.

[0051] Comparative Example 1 (1) Carbonitriding The workpieces to be treated are cleaned to remove oil, rust, and oxide impurities from their surfaces, ensuring surface cleanliness. The cleaned workpieces are then placed in a furnace, followed by vacuuming and introducing a protective gas. Subsequently, a two-stage carbonitriding treatment, consisting of strong infiltration and diffusion, is performed sequentially. During the strong infiltration stage, the carbon potential in the furnace is maintained at 1.1%, the ammonia flow rate is stabilized at 2.1 NL / min, the infiltration layer depth is set at 800 μm, the carbonitriding temperature is calculated to be 850℃ and the infiltration layer depth d is 800 μm according to Formula 1 and Formula 2, the correction coefficient k1 is 1, the strong infiltration time is calculated to be 6h according to Formula 3, therefore the furnace temperature is stabilized at 850℃ and the holding time is 6h.

[0052] During the diffusion stage, the furnace temperature remained constant, the carbon potential decreased to 0.9%, the ammonia flow rate was adjusted to 2.0 NL / min, and the correction coefficient k2 was 1.3. Based on formula 4, the diffusion time was calculated to be 1.5 h, therefore the diffusion holding time was set to 1.5 h. After co-diffusion was completed, the workpiece was air-cooled.

[0053] (2) Austenitization Austenitization is carried out under a nitrogen protective atmosphere by holding the workpiece at 850℃ for 50 minutes to achieve complete austenitization.

[0054] (3) Isothermal quenching After austenitization, the workpiece is quickly placed in a constant-temperature salt bath furnace and stirred until the workpiece temperature stabilizes. The isothermal quenching temperature is calculated according to Formula 8. f B =18%, the temperature correlation constant is taken as 0.3, the transformation index n is taken as 1.3, and the isothermal quenching time is calculated according to formulas 9 and 10. The isothermal quenching temperature is 240℃ and the isothermal quenching time is 42min.

[0055] (4) Stable tempering The quenched workpiece is subjected to low-temperature tempering at 160℃ for 120 minutes. After the tempering is completed, the workpiece is placed in air to cool.

[0056] Figure 3 For the comparison of surface grain size between Example 1 and Comparative Example 1, microscopic observation of the workpiece obtained in Comparative Example 1 revealed that it formed a multi-heterogeneous structure with a surface grain size of approximately 22.3 μm; while the surface grain size of the workpiece in Example 1 was approximately 12.1 μm. The refinement of the surface grains increases the number of grain boundaries, achieving grain boundary strengthening and thus enhancing the surface wear resistance of the workpiece. Mechanical property testing of the workpiece showed that the surface wear rate of the workpiece in Comparative Example 1 was 6.5 × 10⁻⁶. - 6 mm 3 N -1 m -1Surface wear rate of the workpiece in Example 1: 2.3 × 10⁻⁶ -6 mm 3 N -1 m -1 In Example 1, the wear resistance of the workpiece was significantly improved.

[0057] It should be understood that those skilled in the art can make improvements and modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A multi-gradient microstructure heat treatment process for achieving wear resistance and toughening of bearings, characterized in that, Includes the following steps: 1) Carbonitriding is performed on the bearing workpiece to form a continuous and gentle gradient of C and N composition from the surface to the core. After carbonitriding, the workpiece is air-cooled. 2) Then, under a nitrogen protective atmosphere, the workpiece is heated in three stages using a stepped heating method to achieve austenitization; 3) Subsequently, a gradient multiphase structure of martensite and bainite is constructed by isothermal quenching; wherein: the isothermal quenching time is based on the carbonitriding time and is controlled according to the target bainite content, and finally a bainite content of 10~20% in the surface layer and ≥60% in the core is obtained. 4) Finally, the workpiece is subjected to low-temperature tempering treatment to obtain wear-resistant and toughened bearings.

2. The heat treatment process according to claim 1, characterized in that, In step 1), carbonitriding includes a strong infiltration stage and a diffusion stage, wherein: During the strong infiltration stage, the carbon potential in the carbonitriding furnace is maintained at 1.10~1.20%, and the ammonia flow rate is stabilized at 2.0~2.5NL / min. The carbonitriding temperature is determined based on the C, Ni, Si, V, Mo and W in the workpiece, and the carbonitriding time is determined based on the required infiltration layer depth. During the diffusion stage, after the surface carbon and nitrogen elements reach the expected enrichment concentration, the furnace temperature is kept basically unchanged, the furnace gas carbon potential is reduced to 0.9~1.0%, and the ammonia supply flow rate is reduced to 1.7~2.0 NL / min.

3. The heat treatment process according to claim 2, characterized in that, During the strong infiltration stage: Carbonitriding temperature T CN for: Strong infiltration time t 1 is: in, A c1 The critical temperature at which pearlite begins to transform into austenite upon heating, expressed in °C. T CN The value is the carbonitriding temperature, in °C; C, Ni, Si, V, Mo, and W are the percentages of elements in the workpiece. t 1 represents the strong infiltration time, in hours (h). d The depth of the infiltration layer is expressed in μm. k 1 is a correction factor, which is taken as 0.9~1.2 depending on the initial carbon content of the workpiece; During the diffusion phase, the diffusion time t 2 is: in, t 2 represents the diffusion time, in hours (h). t 1 represents the strong infiltration time, in hours (h). k 2 is a correction factor, which is taken as 0.8~1.5 according to the initial carbon content of the workpiece.

4. The heat treatment process according to claim 2 or 3, characterized in that, The infiltration depth is 500~800μm.

5. The heat treatment process according to claim 1, characterized in that, In step 2), the three-stage heating of the workpiece using a stepped heating method is specifically as follows: The first stage involves heating the workpiece to... T 1. Hold at the temperature for 20-30 minutes; 2. Heat the workpiece to the specified temperature in the second stage. T 2. Hold at this temperature for 30-40 minutes; 3. Heat the workpiece to [temperature missing] in the third stage. T 3. Keep warm for 50-60 minutes; where: in, T 1 represents the first stage heating temperature, in °C; T 2 represents the second stage heating temperature, in °C. T 3 represents the heating temperature of the third stage, in °C.

6. The heat treatment process according to claim 1, characterized in that, In step 3), the isothermal quenching temperature is determined based on the material composition C, Cr, Mn and Mo.

7. The heat treatment process according to claim 1 or 6, characterized in that, Isothermal quenching temperature T B for: in, T B The isothermal quenching temperature is expressed in °C; C, Cr, Mn, and Mo represent the percentage of elements present in the workpiece.

8. The heat treatment process according to claim 1, characterized in that, In step 3), the isothermal quenching time t B Calculated using the following formula: in, f B The target surface bainite content; K This is a temperature-dependent constant, taken as 0.2~0.5; t B This refers to the isothermal quenching time, expressed in hours (h). n The transformation index is set at 1.1 to 1.

3. η CN The time correction factor is calculated according to the following formula: in, η CN This is a time correction factor; t 1 represents the strong infiltration time, in hours (h). t 2 represents diffusion time, in hours (h).

9. The heat treatment process according to claim 1, characterized in that, In step 4), the low-temperature tempering process is as follows: the tempering temperature is 150~170℃, the tempering time is 90~120min, and the workpiece is placed in the air to cool after tempering.

10. A wear-resistant and toughened bearing prepared by the heat treatment process described in any one of claims 1-9.

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