Back lining bearing ring material and heat treatment method thereof

Abstract

The invention discloses a backing bearing ring material and a heat treatment method thereof. The heat treatment method comprises the following steps that S1, raw materials are smelted according to specific components, blank casting and forging are conducted, and a forge piece is obtained; s2, spheroidizing annealing is conducted on the forge piece; s3, turning and quenching the annealed part; s4, carrying out quenching treatment based on the step S3; and S5, the quenched part is subjected to tempering treatment. The problems that in the prior art, a carburizing layer of carburizing steel is shallow, the heat treatment period is long, cost is high, and abrasion resistance is insufficient are solved.

Description

Technical Field

[0001] The invention relates to the technical field of bearing processing methods, in particular to a backing bearing ring material and a heat treatment method thereof. Background Art

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

[0003] In view of the shortcomings of the prior art, the present invention provides a backing bearing ring material and a heat treatment method thereof, in order to solve the problems in the prior art of carburized steel having a shallow carburized layer, a long heat treatment cycle, high cost and insufficient wear resistance.

[0004] To achieve the above object, the present invention provides a backing bearing ring material and a heat treatment method thereof, comprising the following steps: S1. The raw materials are melted, cast and forged to obtain forgings. The raw material components include: 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%; S2. Perform spheroidizing annealing on the forging, wherein the spheroidizing annealing process is to heat the blank to 780-820°C at a heating rate of 10-30°C / h, keep it at that temperature for 8-12h, slowly cool it to 700-750°C at a rate of 10-30°C / h, keep it at that temperature for 4-8h, cool it with the furnace to below 550°C, and then air cool it to room temperature after it is taken out of the furnace; S3, lathe the annealed blank and perform quenching treatment, the quenching process includes using a vacuum furnace to heat to 840-880°C at a heating rate of 10-30°C / h, keeping for 30-50min, then heating to 1100-1200°C at a heating rate of 10-30°C / h, keeping for 5-10min, then cooling with helium, the inflation pressure is 2-5bar, the inflation time is 1000-1400s, finally air quenching and air cooling to room temperature before taking out of the furnace, then heating to 550°C at a heating rate of 10-30°C / h in a vacuum tempering furnace, keeping for 3-5h, and air cooling after taking out of the furnace; S4. Based on step S3, use a roller furnace to heat to 840-880°C at a heating rate of 10-30°C / h, keep warm for 50-80min, salt bath temperature of 150-200°C, stirring rate of 500-1000 rpm; S5. Based on step S4, the quenched part is tempered. The tempering process is to heat the quenched blank at a heating rate of 100-150°C / h, keep it at 180°C for 3-5h, and then air-cool it to room temperature after being taken out of the furnace.

[0005] The above technical solution is beneficial in that: the above technology successfully solves the problems of wear resistance, toughness and economy of the backing bearing under high-speed and heavy-load conditions through the coordinated design of component optimization and heat treatment process. The specific beneficial effects are as follows: 1. Precise control of hardenability: Through the 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 a full hardenability design. Compared with traditional carburizing steel (insufficient hardenability leads to core hardness <35HRC), the present invention can ensure a core hardness of 35~48HRC, while the surface hardness is ≥60HRC, forming an ideal gradient distribution.

[0006] 2. Deep hardened layer and improved wear resistance: High temperature austenitization at 1100~1200℃ in vacuum furnace quenching combined with rapid cooling in helium significantly improves the ability to resist spalling. Cr and V carbides are dispersed on the surface, and the wear resistance is improved compared with carburized steel.

[0007] 3. Shortened process cycle and reduced cost: Fully hardened materials replace carburizing process, and the heat treatment cycle is shortened from 10~20 hours to 8~12 hours, which reduces energy consumption. At the same time, the roller furnace quenching process (salt bath temperature 150~200℃ + 800 rpm stirring) realizes mass production, which is cheaper than the vacuum furnace process and avoids the high investment in carburizing equipment.

[0008] 4. Optimization of structure and performance: Spheroidizing annealing (780~820℃ insulation + slow cooling to 700~750℃) forms uniform spherical pearlite, which improves turning efficiency. Low-temperature tempering (180℃ insulation for 3~5h) eliminates 90% of quenching stress, improves impact toughness, and extends fatigue life compared to carburizing steel.

[0009] 5. Compared with GCr15, the present invention solves the problem of insufficient core hardness through composition adjustment and gradient quenching; compared with carburized steel, the hardened layer is deeper, the cost is lower, and the carbide distribution is more uniform. The comprehensive performance meets the long life requirements of the backing bearing of the rolling mill under high speed, heavy load and pollution conditions, and has significant economic and technical advantages.

[0010] The present invention further provides that: the content of each component in the 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%.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] The present invention further provides that: the roller furnace quenching process in the S4 step is to use a roller furnace to heat to 860°C at a heating rate of 20°C / h, keep warm for 60 minutes, the salt bath temperature is 180°C, and the stirring rate is 800 rpm.

[0017] The benefits of adopting the above technical solution are: the fixed roller furnace parameters, salt bath quenching + high-speed stirring (800 rpm) in the above technology achieve uniform cooling, which is suitable for batch production of complex-shaped rings, and by controlling the cooling rate to form a "surface martensite + subsurface bainite" composite structure, further improving the impact resistance.

[0018] The present invention further provides that: in the tempering process of step S5, the blank after quenching treatment is heated at a heating rate of 120° C. / h, kept at 180° C. for 4 hours, and air-cooled to room temperature after being taken out of the furnace.

[0019] The advantages of adopting the above technical solution are as follows: in the above technology, the tempering parameters are fixed, and the twin structure in the quenched martensite is selectively decomposed by low-temperature tempering at 80°C, retaining a high dislocation density to maintain hardness, while eliminating part of the quenching stress and avoiding the tempering brittleness problem of carburized steel. During the tempering process, Cr and V carbides are precipitated along the grain boundaries to form a dispersion strengthening effect, thereby improving the surface wear resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A low-power cross-sectional view of a bearing implemented by the present invention; Figure 2The diagram is a comparison of the surface tissue condition and the core tissue condition implemented by the present invention, wherein the two lower diagrams correspond to the 1000X views after heavy corrosion directly above each other; Figure 3 The hardness distribution of the present invention is compared with the hardness distribution of conventional carburizing. DETAILED DESCRIPTION

[0021] The present invention provides a backing bearing ring material and a heat treatment method thereof, comprising the following steps: S1. The raw materials are melted, cast and forged to obtain forgings. The raw material components include: 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%; S2. Perform spheroidizing annealing on the forging, wherein the spheroidizing annealing process is to heat the blank to 780-820°C at a heating rate of 10-30°C / h, keep it at that temperature for 8-12h, slowly cool it to 700-750°C at a rate of 10-30°C / h, keep it at that temperature for 4-8h, cool it with the furnace to below 550°C, and then air cool it to room temperature after it is taken out of the furnace; S3, lathe the annealed blank and perform quenching treatment, the quenching process includes using a vacuum furnace to heat to 840-880°C at a heating rate of 10-30°C / h, keeping for 30-50min, then heating to 1100-1200°C at a heating rate of 10-30°C / h, keeping for 5-10min, then cooling with helium, the inflation pressure is 2-5bar, the inflation time is 1000-1400s, finally air quenching and air cooling to room temperature before taking out of the furnace, then heating to 550°C at a heating rate of 10-30°C / h in a vacuum tempering furnace, keeping for 3-5h, and air cooling after taking out of the furnace; S4. Based on step S3, use a roller furnace to heat to 840-880°C at a heating rate of 10-30°C / h, keep warm for 50-80min, salt bath temperature of 150-200°C, stirring rate of 500-1000 rpm; S5. Based on step S4, the quenched part is tempered. The tempering process is to heat the quenched blank at a heating rate of 100-150°C / h, keep it at 180°C for 3-5h, and then air-cool it to room temperature after being taken out of the furnace.

[0022] Further: 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%.

[0023] Furthermore, the spheroidizing annealing process in step S2 is to heat the blank to 800°C at a heating rate of 20°C / h, keep it at that temperature for 10 hours, slowly cool it to 720°C at a rate of 20°C / h, keep it at that temperature for 6 hours, cool it to below 550°C with the furnace, and then air-cool it to room temperature.

[0024] Furthermore: the vacuum furnace quenching process in the S3 step is to lathe the annealed blank to the required size of 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, and 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.

[0025] Furthermore, in the step S4, the roller furnace quenching process is to use a roller furnace to heat to 860°C at a heating rate of 20°C / h, keep warm for 60 minutes, the salt bath temperature is 180°C, and the stirring rate is 800 rpm.

[0026] Furthermore, in the step S5, the tempering process is to heat the quenched blank at a heating rate of 120° C. / h, keep it at 180° C. for 4 hours, and then air-cool it to room temperature after being taken out of the furnace.

[0027] The above-mentioned technical manual is attached Figure 1 The distribution of the hardened layer can be clearly seen; the instruction manual is attached. Figure 2The surface structure is quiescent martensite and a large number of evenly distributed carbides, with a small amount of residue, while the core structure is troostite and pearlite; by comparison in the accompanying drawings of the specification, it is concluded that the depth of the hardened layer of the present invention is about 6 mm, which is more than 3 times the depth of the conventional carburized layer, the surface hardness is 60~61HRC, the core hardness is between 35~45, and the hardness decreases slowly from the surface to the core.

[0028] 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, and calcium.

[0029] The basic principles and main features of the present invention and the advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which shall fall within the scope of the present invention to be protected. The scope of protection of the present invention shall be defined by the attached claims and their equivalents.

Claims

1. A backing bearing ring material and a heat treatment method thereof, characterized in that: The following steps are involved: S1. The raw materials are melted, cast and forged to obtain forgings. The raw material components include: 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%; S2. Perform spheroidizing annealing on the forging, wherein the spheroidizing annealing process is to heat the blank to 780-820°C at a heating rate of 10-30°C / h, keep it at that temperature for 8-12h, slowly cool it to 700-750°C at a rate of 10-30°C / h, keep it at that temperature for 4-8h, cool it with the furnace to below 550°C, and then air cool it to room temperature after it is taken out of the furnace; S3, lathe the annealed blank and perform quenching treatment, the quenching process includes using a vacuum furnace to heat to 840-880°C at a heating rate of 10-30°C / h, keeping for 30-50min, then heating to 1100-1200°C at a heating rate of 10-30°C / h, keeping for 5-10min, then cooling with helium, the inflation pressure is 2-5bar, the inflation time is 1000-1400s, finally air quenching and air cooling to room temperature before taking out of the furnace, then heating to 550°C at a heating rate of 10-30°C / h in a vacuum tempering furnace, keeping for 3-5h, and air cooling after taking out of the furnace; S4. Based on step S3, use a roller furnace to heat to 840 - 880 °C at a heating rate of 10 - 30 °C / h, keep warm for 50 - 80 min, salt bath temperature of 150 - 200 °C, stirring rate of 500 - 1000 rpm; S5. Based on step S4, the quenched part is tempered. The tempering process is to heat the quenched blank at a heating rate of 100-150°C / h, keep it at 180°C for 3-5h, and then air-cool it to room temperature after being taken out of the furnace.

2. A backing bearing ring material and heat treatment method thereof 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 backing bearing ring material and heat treatment method thereof according to claim 1, characterized in that: The spheroidizing annealing process in step S2 is to heat the blank to 800°C at a heating rate of 20°C / h, keep it at that temperature for 10 hours, slowly cool it to 720°C at a rate of 20°C / h, keep it at that temperature for 6 hours, cool it to below 550°C with the furnace, and then air-cool it to room temperature.

4. The backing bearing ring material and heat treatment method thereof according to claim 1, characterized in that: The vacuum furnace quenching process in the S3 step is to lathe the annealed blank to the required size of 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, and 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.

5. The backing bearing ring material and heat treatment method thereof according to claim 1, characterized in that: The roller furnace quenching process in step S4 is to use a roller furnace to heat to 860° C. at a heating rate of 20° C. / h, keep warm for 60 minutes, with a salt bath temperature of 180° C. and a stirring rate of 800 rpm.

6. A backing bearing ring material and heat treatment method thereof according to claim 1, characterized in that: The tempering process in step S5 is to heat the quenched blank at a heating rate of 120° C. / h, keep it at 180° C. for 4 hours, and then air-cool it to room temperature after being taken out of the furnace.

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