High-efficiency precise Marbainite complex-phase heat treatment method for high-carbon steel bearing

Abstract

The invention provides an efficient and accurate Marbainite complex-phase heat treatment method for a high-carbon steel bearing, and relates to the technical field of bearing manufacturing. The method comprises the following steps: controlling an austenitizing process by adopting target austenitizing process parameters to obtain target austenite; the method comprises the following steps: controlling the process of transforming a target austenite phase into a target bainite by adopting a graded isothermal quenching process, and determining primary isothermal quenching process parameters according to target bainite nucleation parameters in the primary isothermal quenching process; in the secondary isothermal quenching process, secondary isothermal quenching process parameters are determined according to the target bainite growth parameters; and in the third-stage isothermal quenching process, third-stage isothermal quenching process parameters are determined according to the target bainite volume fraction parameters. By means of the method, refined control over the phase proportion and morphology of the complex-phase structure can be achieved while the bainite of the rolled bearing steel is rapidly formed.

Description

Technical Field

[0001] The present invention relates to the field of bearing manufacturing technology, and in particular to a high-efficiency and precise Mapei complex phase heat treatment method for high-carbon steel bearings. Background Art

[0002] Bearings are core basic components of mechanical equipment, which directly affect the service performance and service life of high-end equipment represented by high-end CNC machine tools, civil aviation engines, high-speed motors, etc. Since high-carbon chromium bearing steel has good forming and processing properties, and has high hardness, good wear resistance and contact fatigue performance after quenching and tempering, it is often used as the base material of bearing rings. The complex phase heat treatment process is currently a commonly used heat treatment process for high-carbon chromium bearings, that is, the rings are directly austenitized and austempered in the lower bainite transformation temperature range, and then cooled to generate part of the high-carbon martensite after the formation of part of the lower bainite. By introducing lower bainite, the complex phase structure can improve the impact toughness of the matrix and improve the bearing ring's load-bearing capacity.

[0003] However, the traditional austempering process for achieving Mapei duplex heat treatment results in slow nucleation of bainite in the early stage and slow transformation rate in the later stage. In the actual production process, it takes a long time and high cost, which is not conducive to mass production. For example, to achieve a 50% bainite content, the austempering time requires at least 1 hour. If the austempering temperature is blindly increased in pursuit of a short incubation period and a high nucleation rate, it is very easy to cause the lath structure to coarsen and merge, thereby deteriorating the performance. In addition, rolling forming, as a pre-process for heat treatment, has a significant effect on the phase transformation kinetics of the subsequent heat treatment process. Therefore, in the process of formulating the heat treatment process, the effect of deformation on duplex heat treatment must also be fully considered.

[0004] In summary, there is an urgent need to provide a method for rapidly forming a martensite-bainite (MB) duplex structure for rolled bearing steel so as to achieve rapid formation of bainite in rolled bearing steel while achieving fine control of the phase ratio and morphology of the duplex structure. Summary of the invention

[0005] The purpose of the present invention is to provide an efficient and precise Mapei complex phase heat treatment method for high carbon steel bearings in view of the deficiencies in the above-mentioned prior art, so as to achieve fine control of the complex phase ratio and morphology while rapidly forming bainite in rolled bearing steel.

[0006] To achieve the above purpose, the technical solution adopted in the embodiment of the present application is as follows:

[0007] In the first aspect, the embodiments of the present application provide an efficient and precise Mapei complex phase heat treatment method for high carbon steel bearings, comprising: determining the target austenite grain size and the target austenite carbon mass fraction of the rolled bearing steel according to the Mapei complex phase heat treatment target; determining the target austenitizing process parameters for obtaining the target austenite grain size and the target austenite carbon mass fraction according to the target rolling deformation and the initial carbon mass fraction of the rolled bearing steel; using the target austenitizing process parameters to control the austenitizing process to obtain the target austenite; using a graded isothermal quenching process to transform the target austenite into the target The process of bainite is controlled. In the primary isothermal quenching process, the primary isothermal quenching process parameters are determined according to the target bainite nucleation parameters, and the primary isothermal quenching process is controlled by the primary isothermal quenching process parameters; in the secondary isothermal quenching process, the secondary isothermal quenching process parameters are determined according to the target bainite growth parameters, and the secondary isothermal quenching process is controlled by the secondary isothermal quenching process parameters; in the tertiary isothermal quenching process, the tertiary isothermal quenching process parameters are determined according to the target bainite volume fraction parameters, and the tertiary isothermal quenching process is controlled by the tertiary isothermal quenching process parameters.

[0008] In one embodiment, the target austenite grain size and the target austenite carbon mass fraction of the rolled bearing steel are determined according to the Mapei duplex heat treatment target, comprising: determining the target austenite grain size and the target austenite carbon mass fraction of the rolled bearing steel according to the target bainite nucleation parameters and the target bainite growth parameters of the target bainite during the Mapei duplex heat treatment process; the Mapei duplex heat treatment target includes the target bainite nucleation parameters and the target bainite growth parameters.

[0009] In one embodiment, the target austenitizing process parameters for obtaining the target austenite grain size and the target austenite carbon mass fraction are determined based on the target rolling deformation and the initial carbon mass fraction of the rolled bearing steel, including: determining the austenite grain size obtained by the rolled bearing steel at different temperatures under the target rolling deformation based on the relationship between the rolling deformation, the austenite grain size and the austenitizing temperature to determine the temperature for obtaining the target austenite grain size; determining the time for obtaining the target austenite carbon mass fraction based on the relationship between the initial carbon mass fraction of the rolled bearing steel, the austenite carbon mass fraction and the austenitizing time; the target austenitizing process parameters include the temperature for obtaining the target austenite grain size and the time for obtaining the target austenite carbon mass fraction.

[0010] In one embodiment, the method of determining the primary isothermal quenching process parameters according to the target bainite nucleation parameters includes: determining the primary isothermal quenching temperature at the target bainite nucleation rate according to the relationship between the initial temperature of martensite transformation, the bainite nucleation rate and the isothermal quenching temperature; determining the primary isothermal quenching time at the first target bainite volume fraction according to the relationship between the rolling deformation, the bainite volume fraction and the isothermal quenching time; the target bainite nucleation parameters include the target bainite nucleation rate and the first target bainite volume fraction.

[0011] In one embodiment, the target bainite nucleation rate is >10 16 m -2 , the first target bainite volume fraction includes 10%.

[0012] In one embodiment, determining the secondary austempering process parameters according to the target bainite growth parameters includes: determining the secondary austempering temperature at the target bainite growth rate according to the relationship between the rolling deformation, the bainite growth rate and the austempering temperature; determining the secondary austempering time at the target bainite beam length according to the relationship between the bainite beam length, the bainite growth rate and the austempering time; the target bainite growth parameters include the target bainite growth rate and the target bainite beam length.

[0013] In one embodiment, the target bainite growth rate is >0.02 μm / s, and the target bainite bundle length is >5 μm.

[0014] In one embodiment, the determining of the three-stage isothermal quenching process parameters according to the target bainite volume fraction parameters includes: determining the three-stage isothermal quenching temperature at the target bainite volume fraction growth rate according to the relationship between the rolling deformation, the bainite volume fraction growth rate and the isothermal quenching temperature; determining the three-stage isothermal quenching time at the second target bainite volume fraction according to the relationship between the rolling deformation, the difference in bainite volume fraction between the three-stage isothermal quenching process and the first isothermal quenching process, and the isothermal quenching time; the target bainite volume fraction parameters include the target bainite volume fraction growth rate and the second target bainite volume fraction.

[0015] In one embodiment, the target bainite volume fraction growth rate> 10 -4 s -1 The second target bainite volume fraction is the ultimate target bainite volume fraction.

[0016] In one embodiment, the target austenite grain size is ≤10 μm, and the target austenite carbon mass fraction is ≤0.8%.

[0017] The beneficial effects of this application are: by optimizing the austenitization process parameters, the austenite grain size and the mass fraction of austenite carbon in rolled bearing steel are regulated to prepare for the subsequent efficient Mapei complex phase heat treatment; by the graded isothermal quenching process, the bainite in rolled bearing steel is rapidly nucleated, orderly elongated, precisely quantitatively controlled and efficiently transformed, avoiding the problem of slow nucleation of bainite in the early stage and easy coarsening in the later stage. The rolling deformation of bearing steel will have a genetic effect on the subsequent heat treatment organizational state. In order to achieve rapid nucleation and size control of bainite in rolled bearing steel, the austenite organizational state is finely controlled to provide sufficient position for bainite nucleation and effective power for bainite elongation; the multi-stage isothermal quenching temperature and time are determined by calculating the bainite nucleation growth kinetics; the incubation period is shortened by the first stage isothermal quenching, and the nucleation is rapidly formed to prepare for the subsequent heat treatment; the bainite morphology is made to meet the requirements by the second stage isothermal quenching; the target volume fraction is quickly reached by the third stage isothermal quenching. This process method effectively solves the problem of inhibited bainite growth in the subsequent heat treatment process of rolled bearing steel, thereby ensuring the acquisition of high-strength and tough Mapei duplex structure while significantly reducing the duplex heat treatment time, reducing heat treatment costs and improving heat treatment efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 A schematic diagram of a process flow of a high-efficiency and precise Mapei multiphase heat treatment method for high-carbon steel bearings provided in an embodiment of the present application;

[0020] Figure 2 A schematic diagram of a process flow of a high-efficiency and precise Mapei multiphase heat treatment method for high-carbon steel bearings provided in an embodiment of the present application;

[0021] Figure 3 Schematic diagram of a process for efficient and precise Mapei multiphase heat treatment of high carbon steel bearings provided in an embodiment of the present application

[0022] Figure 4 A schematic diagram of a process flow of a high-efficiency and precise Mapei multiphase heat treatment method for high-carbon steel bearings provided in an embodiment of the present application;

[0023] Figure 5 A schematic flow chart of an efficient and precise Mapei complex phase heat treatment method for high carbon steel bearings provided in an embodiment of the present application. DETAILED DESCRIPTION

[0024] 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.

[0025] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0026] In the description of the present application, it should be noted that if the terms "upper", "lower", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, or is the orientation or position relationship in which the product of the application is usually placed when used. It is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0027] In addition, the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0028] It should be noted that, in the absence of conflict, the features in the embodiments of the present application may be combined with each other.

[0029] Figure 1 A schematic diagram of a process for an efficient and precise Mapei multiphase heat treatment method for high carbon steel bearings provided in an embodiment of the present application; Figure 1 As shown, the method includes:

[0030] Step 110: Determine the target austenite grain size and target austenite carbon mass fraction of the rolled bearing steel according to the Mapei duplex heat treatment target.

[0031] Among them, Mapei duplex heat treatment is a heat treatment process that combines martensite and bainite, aiming to optimize the microstructure and mechanical properties of the material through different heat treatment stages.

[0032] Martensite is a supersaturated solid solution of carbon in α-Fe, with high strength and hardness. Martensite is initially obtained in steel through the quenching process, that is, the steel is heated to a certain temperature and then rapidly cooled. The three-dimensional structure of martensite is usually flaky or lath-like, but it often appears as a needle in metallographic observation. Martensite is an important means of strengthening steel parts, but it is also a hard and brittle structure, especially high-carbon lamellar martensite.

[0033] Austenite is a lamellar microstructure of steel, which is a solid solution of carbon and alloy elements dissolved in γ-Fe, also known as austenite or γ-Fe. Austenite has good plasticity, low strength, certain toughness, and is not ferromagnetic. Since austenite is a face-centered cubic structure, its octahedral gap is large, so it can accommodate more carbon. In the steel processing process, ingots, billets, and steel are usually heated to above 1100℃ to form austenite, followed by plastic processing such as forging and rolling. Austenite has poor thermal conductivity and a large linear expansion coefficient. These characteristics make austenitic steel suitable for manufacturing instrument components that are sensitive to thermal expansion.

[0034] Bainite is a transformation product formed when austenite is supercooled to a specific temperature range. It is a mixed structure of ferrite and carbide. Bainite has attracted much attention due to its unique transformation mechanism and properties. Its transformation temperature range is between the pearlite transformation temperature and the martensite transformation temperature. According to the different transformation temperatures, bainite can be divided into upper bainite and lower bainite. The final heat treatment state of bainitic steel is usually furnace cooling, air cooling or mold cooling. Its structure is mainly lower bainite, but lath martensite and carbon-free bainite may also appear.

[0035] The target of Mapei complex phase heat treatment, that is, the purpose to be achieved by the efficient and precise Mapei complex phase heat treatment method for high carbon steel bearings provided in the embodiments of the present application, is to provide a method for rapid formation of martensite-bainite (Mapei) complex phase structure for rolled bearing steel so as to achieve rapid formation of bainite in rolled bearing steel while achieving fine control of the phase ratio and morphology of the complex phase structure; specifically, it refers to target bainite nucleation parameters and target bainite growth parameters, which indicate rapid nucleation and growth of target bainite.

[0036] In the embodiment of the present application, in order to ensure the Mapei duplex heat treatment target in the subsequent heat treatment process (for example: the target bainite rapidly nucleates and grows), the austenite needs to satisfy the two conditions of fine grains and controllable carbon mass fraction; therefore, this step needs to determine the target austenite grain size and the target austenite carbon mass fraction.

[0037] Specifically, the above step 110 may further include the following steps:

[0038] The target austenite grain size and target austenite carbon mass fraction of the rolled bearing steel are determined based on the target bainite nucleation parameters and target bainite growth parameters of the target bainite during Mapei duplex heat treatment.

[0039] Among them, the Mapei multiphase heat treatment targets include target bainite nucleation parameters and target bainite growth parameters.

[0040] In the embodiment of the present application, the target austenite grain size determined according to the Mapei duplex heat treatment target is ≤10μm, and the target austenite carbon mass fraction is ≤0.8%; in this way, the Mapei duplex heat treatment target in the subsequent heat treatment process can be guaranteed (for example: the target bainite rapidly nucleates and grows).

[0041] Step 120: Determine target austenitizing process parameters for obtaining a target austenite grain size and a target austenite carbon mass fraction according to the target rolling deformation and the initial carbon mass fraction of the rolled bearing steel.

[0042] Among them, since rolling deformation has an impact on rolled bearing steel, such as: promoting carbide dissolution and inhibiting grain growth; therefore, it is necessary to consider the impact of rolling deformation on rolled bearing steel.

[0043] The target austenitizing process parameters can be determined based on the relationship between the rolling deformation, the initial carbon mass fraction of the rolled bearing steel and the austenitizing process parameters; specifically, Figure 2 This is a schematic diagram of the process of the high-efficiency and precise Mapei multiphase heat treatment method for high-carbon steel bearings provided in the embodiment of the present application. Figure 2 As shown, the above step 120 may further include the following steps 210 and 220:

[0044] Step 210: Determine the austenite grain size obtained by rolling the bearing steel at different temperatures under the target rolling deformation according to the relationship between the rolling deformation, the austenite grain size and the austenitizing temperature, so as to determine the temperature for obtaining the target austenite grain size.

[0045] The relationship between rolling deformation, austenite grain size and austenitizing temperature is shown in the following formula (1):

[0046]

[0047] Where D is the austenite grain size; t A is the austenitizing time; T Ais the austenitizing temperature; A is a constant, which can be 2.248×10 16 ;Q A is the activation free energy of austenite transformation; n is the correction coefficient of rolling deformation ε, n = 3.21 × (1 + ε); R is the ideal gas constant, which is 8.314 J / mol·K.

[0048] In actual operation, the austenite grain size obtained at different temperatures (keeping the quenching time equal and the temperature different) is calculated according to the above formula (1), and then the temperature T of the target austenite grain size is obtained. A .

[0049] Step 220: Determine the time for obtaining the target austenite carbon mass fraction according to the relationship between the initial carbon mass fraction of the rolled bearing steel, the austenite carbon mass fraction and the austenitizing time.

[0050] The target austenitizing process parameters include the temperature for obtaining the target austenite grain size and the time for obtaining the target austenite carbon mass fraction.

[0051] The relationship between the initial carbon mass fraction, austenite carbon mass fraction and austenitizing time of rolled bearing steel is shown in the following formula (2):

[0052] W C,γ =0.067×(0.15-X θ ) / X γ (2)

[0053] Among them, the carbon diffusion equilibrium law (the average carbon content C0 of GCr15 steel is 1.02%), W C,γ is the mass fraction of carbon in austenite; X θ is the final carbon volume fraction of the rolled bearing steel, X0 is the initial carbon volume fraction of the rolled bearing steel, t A is the austenitizing time, β is the kinetic constant, c and m are both constants, ε is the rolling deformation, Q A is the activation free energy of austenite transformation, T A is the austenitizing temperature, R is the ideal gas constant, which is 8.314 J / mol·K; X γ is the volume fraction of austenite.

[0054] In actual operation, the time t required to obtain the target austenite carbon mass fraction can be calculated according to the above formula (2): A .

[0055] Step 130: Control the austenitizing process using target austenitizing process parameters to obtain target austenite.

[0056] In this step, the temperature T of the target austenite grain size calculated in step 210 is used. A and the time t for obtaining the target austenite carbon mass fraction calculated in step 220 A The austenitizing process of the rolled bearing steel is controlled; in this way, the austenite grain size and the mass fraction of the austenite carbon element can be controlled; specifically, step 210 can control the austenite grain size, and step 220 can control the mass fraction of the austenite carbon element.

[0057] Step 140, using a graded isothermal quenching process to control the process of target austenite phase transformation into target bainite. In the primary isothermal quenching process, the primary isothermal quenching process parameters are determined according to the target bainite nucleation parameters, and the primary isothermal quenching process is controlled by the primary isothermal quenching process parameters; in the secondary isothermal quenching process, the secondary isothermal quenching process parameters are determined according to the target bainite growth parameters, and the secondary isothermal quenching process is controlled by the secondary isothermal quenching process parameters; in the tertiary isothermal quenching process, the tertiary isothermal quenching process parameters are determined according to the target bainite volume fraction parameters, and the tertiary isothermal quenching process is controlled by the tertiary isothermal quenching process parameters.

[0058] Among them, the graded isothermal quenching process is primary isothermal quenching, secondary isothermal quenching and tertiary isothermal quenching. During the primary isothermal quenching process, bainite rapidly nucleates; during the secondary isothermal quenching process, bainite grows; during the tertiary isothermal quenching process, bainite rapidly reaches the ultimate target bainite volume fraction. Specifically, Figure 3 This is a schematic diagram of the process of the high-efficiency and precise Mapei multiphase heat treatment method for high-carbon steel bearings provided in the embodiment of the present application. Figure 3 As shown, the above step 140 may further include the following steps 310 and 320:

[0059] Step 310: Determine the primary isothermal quenching temperature at the target bainite nucleation rate according to the relationship between the martensitic transformation initial temperature, the bainite nucleation rate and the isothermal quenching temperature.

[0060] Among them, the relationship between the initial temperature of martensite transformation, the nucleation rate of bainite and the austempering temperature is shown in the following formula (3):

[0061] N m =V m (T1-M s ) (3)

[0062] Among them, N mis the nucleation rate, and the third preset formula is also the nucleation rate model; V0 is the trial frequency; T1 is the austempering temperature; M s is the martensitic transformation starting temperature.

[0063] In actual operation, the target bainite nucleation rate is substituted into the above formula (3) to obtain the primary isothermal quenching temperature under the target bainite nucleation rate.

[0064] Step 320: Determine the primary isothermal quenching time at the first target bainite volume fraction according to the relationship between the rolling deformation, the bainite volume fraction and the isothermal quenching time.

[0065] The target bainite nucleation parameters include a target bainite nucleation rate and a first target bainite volume fraction.

[0066] The relationship between rolling deformation, bainite volume fraction and austempering time is shown in the following formula (4):

[0067]

[0068] Among them, t1 is the isothermal quenching time; Q * G is the activation free energy, C1 and C2 are constants; f is the volume fraction of bainite.

[0069] In actual operation, the first target bainite volume fraction is substituted into the above formula (4) to obtain the primary austempering time at the first target bainite volume fraction.

[0070] Because the bainite transformation rate is fast under this condition, the bainite bundles coarsen and merge rapidly in the later stage; therefore, the isothermal time needs to be strictly controlled to control the bainite volume fraction to about 10% (the first target bainite volume fraction). The process is determined by the bainite phase transformation kinetic model. Under the premise of determining the bainite volume fraction f, the formula for the isothermal quenching time t1 required for the above bainite volume fraction is obtained.

[0071] The target bainite nucleation rate and the first target bainite volume fraction are determined according to the Mapei duplex heat treatment target of the rolled bearing steel according to the high-carbon steel bearing efficient and precise Mapei duplex heat treatment method provided in the embodiment of the present application; specifically, the target bainite nucleation rate>10 16 m -2 , the first target bainite volume fraction includes 10%; in this way, bainite can be rapidly nucleated during the primary austempering process.

[0072] The following is an example to explain the process of determining the secondary austempering process parameters according to the target bainite growth parameters in the above embodiment. Specifically, Figure 4This is a schematic diagram of the process of the high-efficiency and precise Mapei multiphase heat treatment method for high-carbon steel bearings provided in the embodiment of the present application. Figure 4 As shown, the above step 140 may further include the following steps 410 and 420:

[0073] Step 410: Determine the secondary austempering temperature at the target bainite growth rate according to the relationship between the rolling deformation, the bainite growth rate and the austempering temperature.

[0074] Among them, the relationship between rolling deformation, bainite growth rate and austempering temperature is shown in the following formula (5):

[0075]

[0076] Among them, V i is the bainite growth rate; V0 is the pre-exponential factor, which is 30 m / s; ε is the rolling deformation; Q * G is the activation free energy; k is the Boltzmann constant, which is 1.380649×10 -23 J / K; T2 is the isothermal quenching temperature.

[0077] In actual operation, the target bainite growth rate is substituted into the above formula (5) to obtain the secondary austempering temperature at the target bainite growth rate.

[0078] Step 420: Determine the secondary isothermal quenching time at the target bainite beam length according to the relationship between the bainite beam length, the bainite growth rate and the isothermal quenching time.

[0079] The target bainite growth parameters include a target bainite growth rate and a target bainite bundle length.

[0080] The relationship between bainite bundle length, bainite growth rate and austempering time is shown in the following formula (6):

[0081] l=R0+V i t2 (6)

[0082] Among them, l is the length of bainite bundle; R0 is the nucleation radius; t2 is the isothermal quenching time.

[0083] In actual operation, the target bainite bundle length is substituted into the above formula (6) to obtain the secondary austempering time under the target bainite bundle length.

[0084] The target bainite growth rate and the target bainite bundle length are determined by the Mapei duplex heat treatment target of the rolled bearing steel according to the efficient and precise Mapei duplex heat treatment method for high carbon steel bearings provided in the embodiment of the present application; specifically, the target bainite growth rate >0.02μm / s, and the target bainite bundle length >5μm; in this way, bainite can grow rapidly during the secondary isothermal quenching process.

[0085] The following is an example to explain the process of determining the three-stage isothermal quenching process parameters according to the target bainite volume fraction parameters in the above embodiment. Specifically, Figure 5 This is a schematic diagram of the process of the high-efficiency and precise Mapei multiphase heat treatment method for high-carbon steel bearings provided in the embodiment of the present application. Figure 5 As shown, the above step 140 may further include the following steps 510 and 520:

[0086] Step 510: Determine the three-stage austempering temperature at the target bainite volume fraction growth rate according to the relationship between the rolling deformation, the bainite volume fraction growth rate and the austempering temperature.

[0087] Among them, the relationship between rolling deformation, bainite volume fraction growth rate and austempering temperature is shown in the following formula (7):

[0088]

[0089] in, is the bainite volume fraction growth rate (the second target bainite volume fraction growth rate); C1 and C2 are constants; ε is the rolling deformation; Q * G is the activation free energy; R is the ideal gas constant, which is 8.314 J / mol·K; T3 is the isothermal quenching temperature (three-stage isothermal quenching temperature).

[0090] In actual operation, the target bainite volume fraction growth rate is substituted into the above formula (7) to obtain the three-stage austempering temperature under the target bainite volume fraction growth rate.

[0091] Step 520: Determine the three-stage isothermal quenching time at the second target bainite volume fraction according to the relationship between the rolling deformation, the difference in bainite volume fraction between the three-stage isothermal quenching process and the one-stage isothermal quenching process, and the isothermal quenching time.

[0092] The target bainite volume fraction parameters include a target bainite volume fraction growth rate and a second target bainite volume fraction.

[0093] The relationship between the rolling deformation, the difference in bainite volume fraction between the three-stage isothermal quenching process and the one-stage isothermal quenching process, and the isothermal quenching time is shown in the following formula (8):

[0094]

[0095] Among them, t3 is the three-stage austempering time; Δf is the difference in bainite volume fraction between the three-stage austempering process and the one-stage austempering process.

[0096] In actual operation, the difference between the second target bainite volume fraction and the first target bainite volume fraction is substituted into the above formula (8) to obtain the three-stage austempering time at the second target bainite volume fraction.

[0097] The second target bainite volume fraction is the above-mentioned ultimate target bainite volume fraction.

[0098] The target bainite volume fraction growth rate and the second target bainite volume fraction are determined according to the Mapei duplex heat treatment target of the rolled bearing steel according to the high-efficiency and precise Mapei duplex heat treatment method for high-carbon steel bearings provided in the embodiment of the present application; the target bainite volume fraction growth rate>10 -4 s -1 The second target bainite volume fraction can be determined according to the actual purpose; in this way, the bainite can quickly reach the ultimate target bainite volume fraction (the second target bainite volume fraction) during the three-stage isothermal quenching process.

[0099] The embodiment of the present application provides an efficient and precise Mapei complex phase heat treatment method for high carbon steel bearings. First, according to the Mapei complex phase heat treatment target, the target austenite grain size and the target austenite carbon mass fraction of the rolled bearing steel are determined; secondly, according to the target rolling deformation and the initial carbon mass fraction of the rolled bearing steel, the target austenitizing process parameters for obtaining the target austenite grain size and the target austenite carbon mass fraction are determined; thirdly, the target austenitizing process parameters are used to control the austenitizing process to obtain the target austenite; finally, a graded isothermal quenching process is used to transform the target austenite into The process of the target bainite is controlled. In the primary isothermal quenching process, the primary isothermal quenching process parameters are determined according to the target bainite nucleation parameters, and the primary isothermal quenching process is controlled by the primary isothermal quenching process parameters; in the secondary isothermal quenching process, the secondary isothermal quenching process parameters are determined according to the target bainite growth parameters, and the secondary isothermal quenching process is controlled by the secondary isothermal quenching process parameters; in the tertiary isothermal quenching process, the tertiary isothermal quenching process parameters are determined according to the target bainite volume fraction parameters, and the tertiary isothermal quenching process is controlled by the tertiary isothermal quenching process parameters. In this way, the austenite grain size and the mass fraction of austenite carbon in the rolled bearing steel are optimized and regulated by the austenitizing process parameters, so as to prepare for the subsequent efficient Mapei duplex heat treatment; the rapid nucleation of bainite in the rolled bearing steel is achieved through the graded isothermal quenching process, orderly elongation, precise quantitative control and efficient bainite phase transformation, avoiding the problem of slow nucleation of bainite in the early stage and easy coarsening in the later stage. Rolling deformation of bearing steel will have a genetic effect on the state of the subsequent heat treatment organization. In order to achieve rapid nucleation and size control of bainite in rolled bearing steel, the austenite organization state is finely controlled to provide sufficient position for bainite nucleation and effective power for bainite elongation; the multi-stage isothermal quenching temperature and time are determined through the calculation of bainite nucleation and growth kinetics; the incubation period is shortened by the first-stage isothermal quenching, and the nucleation is rapid to prepare for the subsequent heat treatment; the bainite morphology is made to meet the requirements by the second-stage isothermal quenching; and the target volume fraction is quickly reached by the third-stage isothermal quenching. This process method effectively solves the problem of the inhibition of bainite growth in the subsequent heat treatment process of rolled bearing steel, thereby greatly reducing the time of complex phase heat treatment while ensuring the acquisition of high-strength and tough Mapei multiphase organization, reducing the heat treatment cost and improving the heat treatment efficiency.

[0100] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A high-efficiency and accurate Mapei multiphase heat treatment method for high-carbon steel bearings, characterized in that: include: According to the Mapei duplex heat treatment target, the target austenite grain size and target austenite carbon mass fraction of the rolled bearing steel are determined; Determining target austenitizing process parameters for obtaining the target austenite grain size and the target austenite carbon mass fraction according to the target rolling deformation and the initial carbon mass fraction of the rolled bearing steel; The target austenitizing process parameters are used to control the austenitizing process to obtain target austenite; A stepwise isothermal quenching process is used to control the process of the target austenite phase transformation into the target bainite. In the first-stage isothermal quenching process, the first-stage isothermal quenching process parameters are determined according to the target bainite nucleation parameters, and the first-stage isothermal quenching process is controlled by using the first-stage isothermal quenching process parameters; In the secondary isothermal quenching process, the secondary isothermal quenching process parameters are determined according to the target bainite growth parameters, and the secondary isothermal quenching process is controlled by the secondary isothermal quenching process parameters; in the tertiary isothermal quenching process, the tertiary isothermal quenching process parameters are determined according to the target bainite volume fraction parameters, and the tertiary isothermal quenching process is controlled by the tertiary isothermal quenching process parameters.

2. The method according to claim 1, characterized in that The target austenite grain size and target austenite carbon mass fraction of the rolled bearing steel are determined according to the Mapei duplex heat treatment target, including: The target austenite grain size and the target austenite carbon element mass fraction of the rolled bearing steel are determined according to the target bainite nucleation parameters and the target bainite growth parameters of the target bainite during the Mapei duplex heat treatment process; the Mapei duplex heat treatment target includes the target bainite nucleation parameters and the target bainite growth parameters.

3. The method according to claim 1, characterized in that The target austenitizing process parameters for obtaining the target austenite grain size and the target austenite carbon mass fraction are determined according to the target rolling deformation and the initial carbon mass fraction of the rolled bearing steel, including: Determine the austenite grain size obtained by the rolled bearing steel at different temperatures under the target rolling deformation according to the relationship between the rolling deformation, the austenite grain size and the austenitizing temperature, so as to determine the temperature for obtaining the target austenite grain size; According to the relationship between the initial carbon mass fraction, the austenite carbon mass fraction and the austenitizing time of the rolled bearing steel, the time for obtaining the target austenite carbon mass fraction is determined; the target austenitizing process parameters include the temperature for obtaining the target austenite grain size and the time for obtaining the target austenite carbon mass fraction.

4. The method according to claim 1, characterized in that: The step of determining the primary isothermal quenching process parameters according to the target bainite nucleation parameters comprises: According to the relationship between the initial temperature of martensite transformation, the nucleation rate of bainite and the austempering temperature, the primary austempering temperature under the target bainite nucleation rate is determined; According to the relationship between the rolling deformation, the bainite volume fraction and the austempering time, the primary austempering time at the first target bainite volume fraction is determined; the target bainite nucleation parameters include the target bainite nucleation rate and the first target bainite volume fraction.

5. The method according to claim 4, characterized in that The target bainite nucleation rate>10 16 m -2 , the first target bainite volume fraction includes 10%.

6. The method according to claim 1, characterized in that Determining the secondary austempering process parameters according to the target bainite growth parameters includes: According to the relationship between rolling deformation, bainite growth rate and austempering temperature, the secondary austempering temperature at the target bainite growth rate is determined; According to the relationship between bainite beam length, bainite growth rate and austempering time, the secondary austempering time at the target bainite beam length is determined; the target bainite growth parameter includes the target bainite growth rate and the target bainite beam length.

7. The method according to claim 6, characterized in that The target bainite growth rate is >0.02 μm / s, and the target bainite bundle length is >5 μm.

8. The method according to claim 1, characterized in that Determining the three-stage austempering process parameters according to the target bainite volume fraction parameters includes: According to the relationship between rolling deformation, bainite volume fraction growth rate and austempering temperature, the three-stage austempering temperature under the target bainite volume fraction growth rate is determined; The three-stage isothermal quenching time at the second target bainite volume fraction is determined according to the relationship between the rolling deformation, the difference in bainite volume fraction between the three-stage isothermal quenching process and the one-stage isothermal quenching process, and the isothermal quenching time; the target bainite volume fraction parameters include the target bainite volume fraction growth rate and the second target bainite volume fraction.

9. The method according to claim 8, characterized in that The target bainite volume fraction growth rate>10 -4 s -1 .

10. The method according to claim 1, characterized in that The target austenite grain size is ≤10 μm, and the target austenite carbon mass fraction is ≤0.8%.

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