Preparation Process of Backing Bearing Ring Material

Abstract

The present invention discloses a preparation process for a backing bearing ring material, comprising the following steps: S1, melting, casting and forging raw materials with specific components to obtain a forging; S2, spheroidizing annealing the forging; S3, turning and quenching the annealed part; S4, performing quenching treatment again based on step S3; S5, tempering the quenched part. The present invention solves the problems of shallow carburized layer, long heat treatment cycle, high cost and insufficient wear resistance in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of bearing processing methods, and specifically to a preparation process for the material of a backing bearing race. Background Art

[0002] The backing bearing is a key component for load bearing and transmission in a rolling mill, and often works under conditions of high speed, heavy load, pollution, and impact. Therefore, the backing bearing needs to have high toughness, and at the same time, it requires high surface hardness and low core hardness. The traditional design of the backing bearing usually uses carburizing steel (such as 20CrMnTi) through carburizing and quenching treatment to make the surface hardness of the bearing race reach 59 - 64 HRC to meet the wear resistance requirements, while the core maintains a toughness of 35 - 48 HRC. However, this solution has significant defects such as insufficient carburized layer depth, high process cost, uneven carbide distribution, and difficulty in matching hardenability. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention provides a preparation process for the material of a backing bearing race to solve the problems of shallow carburized layer, long heat treatment cycle, high cost, and insufficient wear resistance in the prior art.

[0004] To achieve the above object, the present invention provides a preparation process for the material of a backing bearing race, including the following steps:

[0005] S1. Melting, casting, and forging the raw materials to obtain a forging. The raw material components include:

[0006] C: 1.00 - 1.20%;

[0007] Si: 0.40 - 0.60%;

[0008] Mn: 0.35 - 0.65%;

[0009] Cr: 1.20 - 1.45%;

[0010] V: 0.45 - 0.65%;

[0011] Mo: ≤0.10%;

[0012] P: ≤0.020%;

[0013] S: ≤0.020%;

[0014] Ni: ≤0.25%;

[0015] Cu: ≤0.25%;

[0016] Al: ≤0.050%;

[0017] Ca: ≤0.0010%;

[0018] The balance is iron;

[0019] S2. Perform spheroidizing annealing on the forging. The spheroidizing annealing process is to heat the blank at a heating rate of 10 - 30°C / h to 780 - 820°C, hold for 8 - 12 h, slowly cool to 700 - 750°C at a rate of 10 - 30°C / h, hold for 4 - 8 h, and then cool in the furnace to below 550°C and take out of the furnace and air-cool to room temperature;

[0020] S3. Perform turning and quenching on the annealed blank. The quenching process includes heating in a vacuum furnace at a heating rate of 10~30°C / h to 840~880°C, holding for 30~50 min, then heating at a heating rate of 10~30°C / h to 1100~1200°C, holding for 5~10 min, then cooling with helium, the inflation pressure is 2~5 bar, the inflation time is 1000~1400 s, and finally air-cool to room temperature after gas quenching and take out of the furnace, and then heat in a vacuum tempering furnace at a heating rate of 10~30°C / h to 550°C, hold for 3~5 h, and take out of the furnace and air-cool;

[0021] S4. Based on step S3, use a roller hearth furnace to heat at a heating rate of 10 - 30°C / h to 840 - 880°C, hold for 50 - 80 min, and perform salt bath quenching at a temperature of 150 - 200°C, with a stirring rate of 500 - 1000 r / min;

[0022] S5. Based on step S4, perform tempering on the quenched parts. The tempering process is to heat the blank after quenching treatment at a heating rate of 100 - 150°C / h, hold at 180°C for 3 - 5 h, and take out of the furnace and air-cool to room temperature.

[0023] The advantages of adopting the above technical solutions are as follows: Through the collaborative design of composition optimization and heat treatment process in the above technology, the problems of wear resistance, toughness and economy of the back-up bearing under high-speed and heavy-load working conditions are successfully solved. The specific beneficial effects are as follows:

[0024] 1. Precise control of hardenability: Through the composition combination of C (1.00 - 1.20%), Cr (1.20 - 1.45%), and V (0.45 - 0.65%), the hardenability of the material is between GCr15 and GCr15SiMn, realizing full hardenability design. Compared with traditional carburized steels (the core hardness < 35 HRC due to insufficient hardenability), the present invention can ensure that the core hardness is 35~48 HRC, and at the same time the surface hardness ≥ 60 HRC, forming an ideal gradient distribution.

[0025] 2. Deep Hardening Layer and Enhanced Wear Resistance: High-temperature austenitization at 1100 - 1200°C combined with rapid helium cooling during vacuum furnace quenching significantly improves the anti-spalling ability. Cr and V carbides are dispersed on the surface, enhancing wear resistance compared to carburized steel.

[0026] 3. Process Cycle Shortening and Cost Reduction: Fully hardened materials replace the carburizing process, shortening the heat treatment cycle from 10 - 20 hours to 8 - 12 hours, reducing energy consumption. Meanwhile, the roller hearth furnace quenching process (salt bath temperature 150 - 200°C + 800 rpm stirring) enables batch production, reducing costs compared to the vacuum furnace process and avoiding high investment in carburizing equipment.

[0027] 4. Microstructure and Property Optimization: Spheroidizing annealing (holding at 780 - 820°C + slow cooling to 700 - 750°C) forms uniform spherical pearlite, improving machining efficiency. Low-temperature tempering (holding at 180°C for 3 - 5 h) eliminates 90% of the quenching stress, enhancing impact toughness and extending fatigue life compared to carburized steel.

[0028] 5. Compared with GCr15, the present invention solves the problem of insufficient core hardness through composition adjustment and gradient quenching; compared with carburized steel, it has a deeper hardening layer, lower cost, and more uniform carbide distribution. The comprehensive performance meets the long-life requirements of roll mill backup bearings under high-speed, heavy-load, and contaminated working conditions, with significant economic and technical advantages.

[0029] The present invention further sets: The content of each component in the S1 step is as follows:

[0030] C: 1.05 - 1.15%;

[0031] Si: 0.45 - 0.55%;

[0032] Mn: 0.40 - 0.60%;

[0033] Cr: 1.25 - 1.40%;

[0034] V: 0.50 - 0.60%.

[0035] The benefits of adopting the above technical solution are: in the above technology, the contents of C, Si, Mn, Cr and V are further limited to a more optimal range, so as to achieve precise hardenability control, a C content of 1.05-1.15% balances the martensitic transformation efficiency and the amount of retained austenite, a Cr content of 1.25-1.40% enhances hardenability and forms carbides, and a V content of 0.50-0.60% refines the grains, so that the hardenability is strictly between GCr15 and GCr15SiMn, ensuring that the core hardness meets the standard and the toughness is excellent; at the same time, the wear resistance is improved: higher Cr and V contents promote the formation of surface carbides. Compared with the uneven distribution of carbides in the carburized layer of traditional carburized steel, the wear resistance is further improved by adopting the above components.

[0036] The present invention further provides that: the spheroidizing annealing process in the step S2 is to heat the blank to 800°C at a heating rate of 20°C / h, keep it warm for 10 hours, slowly cool it to 720°C at a rate of 20°C / h, keep it warm for 6 hours, cool it to below 550°C with the furnace, and air cool it to room temperature before taking it out of the furnace.

[0037] The benefits of adopting the above technical solution are: in the above technology, the spheroidizing annealing parameters are fixed, and the optimized annealing process makes the carbides distributed in fine spherical shapes, improving the turning performance, while providing a uniform original structure for subsequent quenching and reducing the risk of quenching deformation. At the same time, compared with traditional annealing processes (such as GCr15 requiring multiple annealings), this process shortens the total processing time and reduces energy consumption through precise temperature control.

[0038] The present invention is further arranged that: the vacuum furnace quenching process in the S3 step is to lathe the annealed blank to the size required by the drawing, use a vacuum furnace to heat to 860°C at a heating rate of 20°C / h, keep warm for 40 minutes, then heat to 1150°C at a heating rate of 20°C / h, keep warm for 8 minutes, then cool with helium, the inflation pressure is 3 bar, the inflation time is 1200s, finally gas quenching and air cooling to room temperature before taking out of the furnace, then heating to 550°C at a heating rate of 20°C / h in a vacuum tempering furnace, keeping warm for 4 hours, and air cooling before taking out of the furnace.

[0039] The advantages of adopting the above technical solution are as follows: in the above technology, fixed vacuum quenching parameters are used, wherein high temperature austenitization at 1150°C allows carbides to be fully dissolved, combined with rapid cooling with helium (2-5 bar) to form a deep martensitic structure (hardened layer depth > carburizing steel), while pretreatment at 860°C inhibits grain coarsening, achieving a surface hardness ≥ 60HRC and a core hardness of 35-48HRC, reducing oxidation and decarburization through vacuum environment + helium cooling, and providing low quenching stress, thereby avoiding the problem of easy cracking of carburizing steel, and achieving significantly better material toughness than carburizing steel.

[0040] The present invention further provides: In the step S4, the quenching process of the roller hearth furnace is to heat to 860°C at a heating rate of 20°C / h using the roller hearth furnace, hold for 60 min, with the salt bath temperature at 180°C and the stirring rate at 800 r / min.

[0041] The advantages of adopting the above technical solution are as follows: In the above technology, the parameters of the roller hearth furnace are fixed, and salt bath quenching + high-speed stirring (800 r / min) realizes uniform cooling, which is suitable for batch production of complex-shaped rings. By controlling the cooling rate, a composite structure of "surface martensite + subsurface bainite" is formed, further improving the impact resistance.

[0042] The present invention further provides: In the step S5, the tempering process is to heat the blank after quenching treatment at a heating rate of 120°C / h, hold at 180°C for 4 h, and then air-cool to room temperature after leaving the furnace.

[0043] The advantages of adopting the above technical solution are as follows: In the above technology, the tempering parameters are fixed. The 80°C low-temperature tempering selectively decomposes the twin structure in the quenched martensite, retains a high dislocation density to maintain hardness, and at the same time eliminates part of the quenching stress, avoiding the problem of temper brittleness of carburized steel. During the tempering process, Cr and V carbides precipitate along the grain boundaries, forming a dispersion strengthening effect and improving the surface wear resistance. Description of the Drawings

[0044] Figure 1 It is a macrostructure diagram of the bearing cross-section implemented by the present invention;

[0045] Figure 2 It is a comparison diagram of the surface structure and the core structure implemented by the present invention, where the two lower diagrams correspond to the 1000X views after heavy corrosion directly above them;

[0046] Figure 3 It is a comparison curve graph of the hardness distribution implemented by the present invention and the hardness distribution of conventional carburization. Detailed Embodiments

[0047] The present invention provides a preparation process for a backing bearing ring material, including the following steps:

[0048] S1. Melting, casting, and forging the raw materials to obtain forgings. The raw material components include:

[0049] C: 1.00 - 1.20%;

[0050] Si: 0.40 - 0.60%;

[0051] Mn: 0.35 - 0.65%;

[0052] Cr: 1.20 - 1.45%;

[0053] V: 0.45 - 0.65%;

[0054] Mo: ≤0.10%;

[0055] P: ≤0.020%;

[0056] S: ≤0.020%;

[0057] Ni: ≤0.25%;

[0058] Cu: ≤0.25%;

[0059] Al: ≤0.050%;

[0060] Ca: ≤0.0010%;

[0061] The balance is iron;

[0062] S2. Spheroidizing annealing is carried out on the forging. The spheroidizing annealing process is to heat the blank at a heating rate of 10 - 30°C / h to 780 - 820°C, hold for 8 - 12 h, slowly cool at a rate of 10 - 30°C / h to 700 - 750°C, hold for 4 - 8 h, and then cool in the furnace to below 550°C and take out and air-cool to room temperature;

[0063] S3. Turning and quenching treatments are carried out on the annealed blank. The quenching process includes heating in a vacuum furnace at a heating rate of 10~30°C / h to 840~880°C, holding for 30~50 min, then heating at a heating rate of 10~30°C / h to 1100~1200°C, holding for 5~10 min, then cooling with helium, the inflation pressure is 2~5 bar, the inflation time is 1000~1400 s, and finally air-cool to room temperature after gas quenching and take out, and then heat in a vacuum tempering furnace at a heating rate of 10~30°C / h to 550°C, hold for 3~5 h, and take out and air-cool;

[0064] S4. Based on step S3, further heat in a roller hearth furnace at a heating rate of 10 - 30°C / h to 840 - 880°C, hold for 50 - 80 min, and perform salt bath quenching at a temperature of 150 - 200°C, and the stirring rate is 500 - 1000 r / min;

[0065] S5. Based on step S4, temper the quenched part. The tempering process is to heat the blank after quenching treatment at a heating rate of 100 - 150°C / h, hold at 180°C for 3 - 5 h, and take out and air-cool to room temperature.

[0066] Furthermore: The content of each component in step S1 is:

[0067] C: 1.05 - 1.15%;

[0068] Si: 0.45 - 0.55%;

[0069] Mn: 0.40 - 0.60%;

[0070] Cr: 1.25 - 1.40%;

[0071] V: 0.50 - 0.60%.

[0072] Furthermore: In the spheroidizing annealing process of the S2 step, the blank is heated to 800°C at a heating rate of 20°C / h, held for 10 h, slowly cooled to 720°C at a rate of 20°C / h, held for 6 h, and then cooled in the furnace to below 550°C and taken out of the furnace and air-cooled to room temperature.

[0073] Furthermore: In the vacuum furnace quenching process of the S3 step, the annealed blank is machined by turning to the dimensions required by the drawing, and then heated to 860°C at a heating rate of 20°C / h in a vacuum furnace, held for 40 min, then heated to 1150°C at a heating rate of 20°C / h, held for 8 min, and then cooled by helium, with an inflation pressure of 3 bar and an inflation time of 1200 s. Finally, after air quenching, it is taken out of the furnace and air-cooled to room temperature, and then heated to 550°C at a heating rate of 20°C / h in a vacuum tempering furnace, held for 4 h, and taken out of the furnace and air-cooled.

[0074] Furthermore: In the roller hearth furnace quenching process of the S4 step, the roller hearth furnace is used to heat to 860°C at a heating rate of 20°C / h, held for 60 min, with a salt bath temperature of 180°C and a stirring rate of 800 revolutions per minute.

[0075] Furthermore: In the tempering process of the S5 step, the blank after quenching treatment is heated at a heating rate of 120°C / h, held at 180°C for 4 h, and taken out of the furnace and air-cooled to room temperature.

[0076] In the above technology, it can be clearly seen from the attached drawings of the specification Figure 1 the distribution of the hardened layer; from the attached drawings of the specification Figure 2 the surface structure is lath martensite and a large number of uniformly distributed carbides, with a small amount of retained austenite, while the core structure is troostite and pearlite; from the attached drawings of the specification, it can be obtained by comparison that the hardened layer depth of the present invention is about 6 mm, which is more than 3 times the conventional carburized layer depth, the surface hardness is 60 - 61 HRC, the core hardness is between 35 - 45, and the hardness slowly decreases from the surface to the core.

[0077] In the above technology, C; Si; Mn; Cr; V; Mo; P; S; Ni; Cu; Al; Ca; in the order of arrangement are carbon, silicon, manganese, chromium, vanadium, molybdenum, phosphorus, sulfur, nickel, copper, aluminum, calcium.

[0078] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification is only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A preparation process of a backing bearing ring material, characterized in that: It includes the following steps: S1. Melting, casting and forging the raw materials to obtain forgings. The raw material composition includes: C: 1.00 - 1.20%； Si: 0.40 - 0.60%; Mn: 0.35 - 0.65%; Cr: 1.20 - 1.45%； V: 0.45 - 0.65%； Mo: ≤0.10%; P: ≤0.020%； S: ≤0.020%； Ni: ≤0.25%; Cu: ≤0.25%; Al: ≤0.050%； Ca: ≤0.0010%; The balance is iron; S2. Spheroidizing annealing the forgings. The spheroidizing annealing process is to heat the blank at a heating rate of 10 - 30°C / h to 780 - 820°C, hold for 8 - 12 h, slowly cool at a rate of 10 - 30°C / h to 700 - 750°C, hold for 4 - 8 h, and then cool with the furnace to below 550°C and take out and air-cool to room temperature; S3. Turning and quenching the annealed blank. The quenching process includes using a vacuum furnace to heat at a heating rate of 10~30°C / h to 840~880°C, hold for 30~50 min, then heat at a heating rate of 10~30°C / h to 1100~1200°C, hold for 5~10 min, then cool with helium, the inflation pressure is 2~5 bar, the inflation time is 1000~1400 s, and finally air-cool to room temperature after gas quenching and take out of the furnace, and then heat in a vacuum tempering furnace at a heating rate of 10~30°C / h to 550°C, hold for 3~5 h, and take out and air-cool; S4. Based on step S3, use a roller hearth furnace to heat at a heating rate of 10 - 30°C / h to 840 - 880°C, hold for 50 - 80 min, and perform salt bath quenching at a temperature of 150 - 200°C, and the stirring rate is 500 - 1000 r / min; S5. Based on step S4, perform tempering treatment on the quenched parts. The tempering process is to heat the blank after quenching treatment at a heating rate of 100 - 150°C / h, hold at 180°C for 3 - 5 h, and take out and air-cool to room temperature.

2. The preparation process of a backing bearing race material according to claim 1, characterized in that: The content of each component in step S1 is: C: 1.05 - 1.15%； Si: 0.45 - 0.55%; Mn: 0.40 - 0.60%; Cr: 1.25 - 1.40%； V: 0.50 - 0.60%。 3. The preparation process of a backing bearing ring material according to claim 1, characterized in that: The spheroidizing annealing process in step S2 is to heat the blank at a heating rate of 20°C / h to 800°C, hold for 10 h, slowly cool at a rate of 20°C / h to 720°C, hold for 6 h, and then cool with the furnace to below 550°C and take out and air-cool to room temperature.

4. The preparation process of a backing bearing race material according to claim 1, characterized in that: The vacuum furnace quenching process in step S3 is to machine the annealed blank to the dimensions required by the drawing, use a vacuum furnace to heat at a heating rate of 20°C / h to 860°C, hold for 40 min, then heat at a heating rate of 20°C / h to 1150°C, hold for 8 min, then cool with helium, the inflation pressure is 3 bar, the inflation time is 1200 s, and finally air-cool to room temperature after gas quenching and take out of the furnace, and then heat in a vacuum tempering furnace at a heating rate of 20°C / h to 550°C, hold for 4 h, and take out and air-cool.

5. The preparation process of a backing bearing ring material according to claim 1, characterized in that: In the S4 step, the quenching process of the roller hearth furnace is to heat to 860°C at a heating rate of 20°C / h using the roller hearth furnace, hold for 60 min, with a salt bath temperature of 180°C and a stirring rate of 800 revolutions / min.

6. The preparation process of a backing bearing ring material according to claim 1, characterized in that: In the S5 step, the tempering process is to heat the blank after quenching treatment at a heating rate of 120°C / h, hold at a temperature of 180°C for 4 h, and then air-cool to room temperature after discharging from the furnace.

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