A method for collaborative manufacturing of super-refined matrix structure of thin-wall bearings through shape and phase transformation

Abstract

The present invention discloses a shape and phase transformation collaborative manufacturing method for ultra-refinement of the matrix structure of a thin-wall bearing, which comprises the following steps: S1, near-net rolling deformation control; the deformation of the bearing matrix is controlled by adopting a near-net rolling forming process, and the optimal deformation structure state is obtained by reasonably controlling the deformation amount and the deformation speed; S2, rapid austenitization; S3, phase transformation sequence control. The present invention changes the original austenite grain size, carbide size, martensite, bainite and retained austenite morphology, size and content in the bearing matrix structure, so as to achieve the purpose of ultra-refining the bearing matrix structure through shape and phase transformation collaborative control.

Description

Technical Field

[0001] The present invention belongs to the technical field of bearing ring manufacturing, and particularly relates to a method for collaborative manufacturing of shape and phase transformation for ultra-refinement of the matrix structure of thin-walled bearings. Background Art

[0002] Thin-walled bearings are the core components of high-precision RV reducers, and their matrix performance directly determines the load-bearing capacity, rotational accuracy, reliability, and service life of RV reducers. The bearing matrix mainly refers to the bearing ring, and its accuracy retention, reliability, and service life during the service of the bearing are closely related to the matrix tissue state.

[0003] The tissue state of the bearing ring matrix under service conditions mainly depends on the matrix forming and heat treatment phase transformation processes. However, the original austenite grain size, carbide size, martensite and retained austenite morphology, size, and content in the matrix structure of thin-walled bearings manufactured by existing manufacturing process methods cannot be precisely controlled, resulting in poor strength and toughness and tissue stability of the bearing matrix, and it is difficult to meet the service condition requirements of high load-bearing, high precision, and long service life of RV reducers.

[0004] Therefore, we urgently need a new manufacturing process method to change the original austenite grain size, carbide size, martensite and retained austenite morphology, size, and content in the bearing matrix structure. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for collaborative manufacturing of shape and phase transformation for ultra-refinement of the matrix structure of thin-walled bearings. Based on the near-net rolling deformation and heat treatment phase transformation of the bearing matrix, through the optimized matching of deformation and phase transformation process parameters, the original austenite grain size, carbide size, martensite and retained austenite morphology, size, and content in the bearing matrix structure are changed, so as to achieve the purpose of collaborative control of shape and phase transformation for ultra-refinement of the bearing matrix structure.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A method for collaborative manufacturing of shape and phase transformation for ultra-refinement of the matrix structure of thin-walled bearings, which includes the following steps:

[0008] S1. Near-net rolling deformation control;

[0009] Adopt the near-net rolling forming process to control the deformation of the bearing matrix, and obtain the optimal deformation tissue state by reasonably controlling the deformation amount and deformation speed;

[0010] S2. Rapid austenitization to achieve control of the original austenite grain size, carbide size, and alloy composition uniformity in the bearing matrix structure;

[0011] S3. Phase transformation sequence control.

[0012] A further solution is that the method for controlling near-net rolling deformation in S1 is as follows:

[0013] During the forming process, control the amount of deformation through the rolling deformation amount and control the deformation speed through the deformation rate.

[0014] The rolling deformation amount of the bearing race The deformation speed V1 of the bearing race = λ1ε1·V0, where δ1 is the elongation of the bearing material in the tensile test at room temperature, r0 is the curvature radius of the bearing raceway, R1 and R2 are the inner diameter and outer diameter of the bearing race respectively, k1 is the characteristic coefficient of the cold rolling ring deformation amount, the value range of k1 is 2 - 3, λ1 is the characteristic coefficient of the cold rolling deformation speed, the value range of λ1 is 1 - 3, and V0 takes the standard deformation speed of 1 mm / s. The key to obtaining the best rolling deformation structure lies in controlling the rolling deformation amount. During the near-net rolling forming process, if the deformation amount is too large, it will cause damage to the bearing matrix during the deformation process and form defective products; if the deformation amount is small, the best deformation structure cannot be obtained. Therefore, considering that different materials have different elongation rates and deformation characteristics, it is necessary to select the best deformation amount and deformation speed for materials with different mechanical property characteristics (that is, the deformation amount is no longer a fixed value. If it is a fixed value, when the elongation rate of the material is low, cracks will occur and the high strength and toughness requirements cannot be met; when the elongation rate of the material is high, the effect of the deformation structure state is not ideal). By reasonable near-net rolling deformation amount and deformation speed, controlling the rolling deformation amount within a certain range can obtain the best deformation structure state;

[0015] A further solution is that the method for rapid austenitization in S2 is as follows: Heat the bearing matrix to 900°C - 950°C at a heating rate of 300°C / s - 500°C / s, and hold at the austenitization temperature to control the uniformity of the original austenite grain size, carbide size and alloy composition in the bearing matrix structure.

[0016] A further solution is to hold at the austenitization temperature for 10 s - 15 s.

[0017] A further solution is to heat the near-net rolled formed bearing matrix using an induction heating device under an argon protection atmosphere, which is convenient for the recrystallization of the bearing matrix deformation structure and the precise control of the carbide dissolution process.

[0018] A further solution is that the phase transformation sequence control in S3 includes:

[0019] 1) Conduct martensite pre-quenching phase transformation treatment to precisely control the morphology and volume fraction of pre-quenched martensite;

[0020] 2) Immediately conduct bainite isothermal quenching treatment (bainite phase transformation), and precisely control the bainite size and volume fraction through the cooperation of the isothermal temperature and time;

[0021] 3) Quench rapidly in oil to room temperature to further refine the retained austenite size by martensitic transformation; or, quench rapidly into an alcohol-dry ice mixture for cryogenic treatment to further refine the retained austenite size by martensitic transformation.

[0022] A further solution is that step 1) includes: performing martensitic pre-quenching treatment on the bearing matrix after rapid austenitization, controlling the pre-quenching temperature between 10°C and 30°C below Ms, and controlling the time within 15 s to 2 min. By using the influence of the uneven distribution of alloying elements on the Ms temperature, control the morphology and volume fraction of pre-quenched martensite.

[0023] A further solution is that step 2) includes: performing bainite isothermal quenching treatment between 20°C and 50°C above the Ms temperature for 5 min - 10 min, and controlling the bainite size and volume fraction through the cooperation of isothermal temperature and time.

[0024] A further solution is that step 3) includes: rapidly quenching into an alcohol-dry ice mixture at -30°C to -50°C and holding for 10 min to 30 min for cryogenic treatment to further refine the retained austenite size by martensitic transformation and achieve control of the retained austenite size and content.

[0025] The beneficial effects of the present invention are as follows:

[0026] Through the room-temperature near-net rolling forming process, deformation control is carried out on the bearing matrix to form a rolling deformation structure, change the ferrite and carbide tissue states, and obtain a metal streamline along the geometric contour of the bearing matrix;

[0027] Adopt the rapid austenitization technology to precisely control the austenitization process of the deformation structure of the near-net rolled bearing matrix, obtain refined prior austenite grains and carbide sizes, and reasonably regulate the alloy composition uniformity;

[0028] Through the control of the phase transformation sequence, ultra-refinement of martensite, bainite and retained austenite in the bearing matrix structure is achieved;

[0029] The heating rate and temperature in rapid austenitization can make the austenitization process obtain the maximum alloy composition inhomogeneity of austenite;

[0030] The present invention realizes the purpose of ultra-refinement control of prior austenite grains, carbides, martensite, bainite and retained austenite in the bearing matrix through the coordinated control of shape and phase transformation of near-net rolling deformation and heat treatment phase transformation;

[0031] In the near-net rolling forming of the bearing matrix, the deformation effect is utilized to obtain the macroscopic geometric shape and deformed structure. Heat treatment uses the phase transformation effect to precisely control the matrix tissue state, achieving ultra-fine grain refinement of the bearing matrix, thereby improving the strength, toughness and tissue stability of the matrix, and enhancing the service performance of the thin-walled bearing. Detailed implementation mode

[0032] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] Taking a certain type of thin-walled bearing outer ring made of GCr15 bearing steel as an example, its parameters are as follows: R1 = 201.5 mm, R2 = 214 mm, r0 = 5.4 mm, δ1 = 33.5%.

[0034] The phase transformation and deformation collaborative manufacturing method for ultra-fine grain refinement of the thin-walled bearing ring matrix is used to carry out phase transformation and deformation collaborative regulation and ultra-fine grain refinement treatment on the matrix of the bearing outer ring, including the following steps:

[0035] S1. Near-net rolling deformation control: Adopt the near-net rolling forming process, reasonably control the deformation amount and deformation speed, and obtain the best deformed tissue state; specifically:

[0036] According to the formula Calculate that the reasonable deformation amount of cold rolling ring is 29.0% - 43.6%. In this example, the cold rolling deformation amount is selected as 40%; according to the formula V1 = λ1ε·V0, calculate that the reasonable deformation speed of cold rolling ring is 0.38 - 1.14 mm / s. In this example, the deformation speed is selected as 0.8 mm / s for near-net rolling forming;

[0037] S2. Rapid austenitization control: Set the austenitization heating parameters according to the deformed structure of the bearing matrix and the austenitization conditions, and control the grain size, carbide size and alloy composition uniformity of the bearing ring matrix;

[0038] Heat the near-net rolled bearing matrix to 900°C - 950°C at a heating rate of 300°C / s - 500°C / s under an argon protection atmosphere by induction heating, and hold for 10 s - 15 s to achieve control of the original austenite grain size, carbide size and alloy composition uniformity in the bearing matrix tissue;

[0039] In this example, heat to 920°C at a heating rate of 350°C / s and hold for 12 s. By precisely controlling the recrystallization and carbide dissolution processes of the bearing matrix deformed structure, control of the original austenite grain and carbide sizes and alloy composition uniformity is achieved;

[0040] S3. Variable sequence control: After rapid austenitization, the bearing matrix is first subjected to martensite pre-quenching treatment, with the temperature controlled to be maintained between 10°C and 30°C below Ms for within 15 s to 2 min. Utilizing the influence of the uneven distribution of alloying elements on the Ms temperature, the morphology and volume fraction of pre-quenched martensite are controlled to achieve precise control of the morphology and volume fraction of pre-quenched martensite. Then, bainite austempering treatment is carried out (bainite austempering treatment is carried out between 20°C and 50°C above Ms, and the time is 5 min - 10 min). The precise control of the bainite size and volume fraction is achieved through the coordination of the austempering temperature and time. Finally, it is rapidly quenched into an alcohol-dry ice mixture and kept at -30°C to -50°C for 10 min to 30 min for cryogenic treatment to further refine the size of retained austenite.

[0041] In this example, the bearing ring after rapid austenitization is quickly placed in a 200°C salt bath and kept for 1 min for martensite bath quenching. Then, the bearing ring is placed in a 240°C salt bath and kept for 15 min for bainite austempering. Finally, it is rapidly quenched into an alcohol-dry ice mixture at -45°C and kept for 20 min for cryogenic treatment.

[0042] Through experimental analysis, the average size of prior austenite grains, the average size of carbides, the laths of pre-quenched martensite, the width size of bainite, and the size of retained austenite in the bearing matrix obtained in Example 1 are 5.6 μm, 350 nm, 50 nm, 360 nm, and 35 nm respectively. The results confirm that the present invention can achieve the purpose of ultra-refinement of the bearing matrix structure.

[0043] The present invention takes into account the genetic influence of the near-net-rolled deformed structure on the heat treatment phase transformation process. First, through the rapid austenitization process, precise control of the recrystallization of the deformed structure and the dissolution process of carbides is achieved, reaching the effects of refining the prior austenite grains and carbide size in the matrix structure and uneven distribution of alloying components. Then, by setting a reasonable phase transformation sequence, the morphology and volume fraction of pre-quenched martensite are controlled to obtain lath martensite with good toughness and divide the prior austenite grains. Subsequently, reasonable bainite austempering temperature and time are set to control the bainite morphology and volume fraction. Finally, it is rapidly quenched into an alcohol-dry ice mixture to realize the further decomposition of the retained austenite that has not transformed after bainite transformation, and to control the size, morphology, and content of retained austenite. The present invention realizes the ultra-refinement of prior austenite grains, carbides, martensite, bainite, and retained austenite structures in the bearing matrix through the optimized matching of reasonable control of the near-net-rolled deformation, austenitization, and heat treatment phase transformation process parameters of the bearing matrix.

[0044] It should be understood that for those of ordinary skill in the art, improvements or transformations can be made according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A method for collaborative manufacturing of super-refined matrix structure of thin-wall bearings by form and phase transformation, characterized in that It includes the following steps: S1. Near-net rolling deformation control; Adopt the near-net rolling forming process to control the deformation of the bearing matrix, and obtain the best deformed tissue state by reasonably controlling the deformation amount and deformation speed; S2. Rapid austenitization; The method of rapid austenitization in S2 is: heat the bearing matrix to the austenitization temperature of 900°C - 950°C at a heating rate of 300°C / s - 500°C / s and hold for a certain time to realize the control of the original austenite grain size, carbide size and alloy composition uniformity in the bearing matrix structure; S3. Phase transformation sequence control; including: 1) Conduct martensite pre-quenching phase transformation treatment to control the morphology and volume fraction of pre-quenched martensite; including: Conduct martensite pre-quenching treatment on the bearing matrix after rapid austenitization, control the pre-quenching temperature 10°C - 30°C below Ms, and control the time within 15s - 2min; 2) Immediately conduct bainite isothermal quenching treatment to control the bainite size and volume fraction through the cooperation of isothermal temperature and time; including: Conduct bainite isothermal quenching treatment between 20°C - 50°C above the Ms temperature for 5min - 10min; 3) Quench rapidly into an alcohol-dry ice mixture for cryogenic treatment to further refine the retained austenite size by martensite transformation; including: Quench rapidly into an alcohol-dry ice mixture at -30°C - -50°C and hold for 10min - 30min for cryogenic treatment.

2. The method for collaborative manufacturing of super-refined matrix structure of thin-wall bearings according to claim 1, characterized in that : The method of near-net rolling deformation control in S1 is: During the forming process, control the deformation amount by the rolling deformation amount and control the deformation speed by the deformation speed; The rolling deformation amount of the bearing ring The deformation speed V1 of the bearing ring = λ1ε1·V0, where δ1 is the elongation rate in the tensile test of the bearing material at room temperature, r0 is the curvature radius of the raceway of the bearing ring, R1 and R2 are the inner diameter and outer diameter of the bearing ring respectively, k1 is the characteristic coefficient of the cold ring rolling deformation amount, and the value range of k1 is 2 - 3; λ1 is the characteristic coefficient of the cold rolling deformation speed, the value range of λ1 is 1 - 3, and V0 takes the standard deformation speed of 1 mm / s.

3. The method for collaborative manufacturing of super-refined matrix structure of thin-wall bearings according to claim 1, characterized in that: Hold at the austenitization temperature for 10s - 15s.

4. The method for collaborative manufacturing of super-refined matrix structure of thin-wall bearings according to claim 1 or 3, characterized in that: The rapid austenitization in S2 is heated by an induction heating device under an argon protection atmosphere.

Images