High-temperature-resistant light bearing steel and preparation method thereof

Abstract

The present application relates to the field of metal material component design and heat treatment, in particular to a high-temperature-resistant light bearing steel and a preparation method thereof.The chemical components are as follows in percentage by weight: C 1.2-1.5%, Si 0.15-0.50%, Mn 0.25-0.45%, P≤0.02%, S≤0.02%, Al 4-8%, Cr 1.20-1.65%, Mo 0.02-0.08, La and Ce 0.01-0.05%, and Fe in the rest.Based on the component optimization, the present application optimizes the whole-process preparation process of the high-temperature-resistant light bearing steel, including smelting, forging and performance heat treatment and the like.The high-temperature-resistant light bearing steel has excellent performance: the density is 6.9-7.1 kg / m 3 , the hardness is ≥58HRC after long-term work at 400 ℃, the yield strength is ≥1850 MPa, and the tensile strength is ≥2150 MPa.

Description

Technical Field

[0001] This invention relates to the field of metal material composition design and heat treatment, specifically to a high-temperature resistant lightweight bearing steel and its preparation method. Background Technology

[0002] GCr15 bearing steel is widely used in many fields of industrial production, such as wind power, high-speed rail, and automobiles. It is currently the most widely used high-carbon chromium bearing steel. This is mainly due to GCr15's ease of production, low price, good wear resistance, and high hardness.

[0003] According to the standard (GB / T 18254-2002), the chemical composition of GCr15 steel is as follows:

[0004]

[0005] The heat treatment process for GCr15 bearing steel mainly includes annealing, quenching, and tempering. During annealing, the material is heated to 780–820℃, held for a period of time to ensure uniform heating, and then cooled to room temperature. During quenching, the material is heated to 850–880℃, held for a period of time to ensure complete and uniform heating, and then rapidly cooled to room temperature. During tempering, the material is heated to 150–200℃, held for a period of time, and then air-cooled to room temperature. GCr15 bearing steel treated in this way possesses high hardness and high strength, with a hardness ≥59HRC, yield strength ≥1700MPa, and tensile strength ≥2000MPa.

[0006] However, GCr15 bearing steel has poor high-temperature resistance and is generally only suitable for room-temperature conditions, failing to meet the requirements of higher-temperature service environments. Furthermore, bearing operation is always accompanied by heat generation and temperature rise, especially after initial wear occurs, leading to a significant increase in local temperature and consequently significant degradation of the bearing steel material, accelerating wear and reducing lifespan. In addition, lightweight bearings can reduce stress during operation and delay the formation of defects. Therefore, improving the high-temperature resistance of bearing steel and reducing the weight of bearings can significantly improve bearing life and expand their application scenarios, which is of great significance. Summary of the Invention

[0007] The purpose of this invention is to provide a high-temperature resistant lightweight bearing steel and its preparation method, which significantly improves its high-temperature resistance while achieving lightweighting, and maintains an economic advantage close to that of GCr15 bearing steel.

[0008] The technical solution of this invention is:

[0009] A high-temperature resistant lightweight bearing steel has the following chemical composition by weight percentage: C 1.2-1.5%, Si 0.15-0.50%, Mn 0.25-0.45%, P≤0.02%, S≤0.02%, Al 4-8%, Cr 1.20-1.65%, Mo 0.02-0.08%, La and Ce 0.01-0.05%, Fe balance.

[0010] The aforementioned high-temperature resistant lightweight bearing steel contains 0.005–0.03% La and 0.005–0.03% Ce.

[0011] The preparation method of the high-temperature resistant lightweight bearing steel includes smelting, forging, and performance heat treatment processes, with the specific steps as follows:

[0012] (1) Smelting: Vacuum induction melting + vacuum degassing treatment to ensure the purity of molten steel; after vacuum degassing, high-purity rare earth alloy is added for final deoxidation and inclusion refinement treatment to finally meet the chemical composition requirements of high temperature resistant lightweight bearing steel, and high temperature resistant lightweight bearing steel ingots are cast.

[0013] (2) Forging: The high-temperature resistant lightweight bearing steel ingot that meets the composition requirements is subjected to three-dimensional forging treatment, and the forging temperature is controlled at 1000~1250℃.

[0014] (3) Spheroidizing annealing: After forging, spheroidizing annealing is performed. The holding temperature is selected as 800-850℃. After holding for 2-8 hours, the furnace is slowly cooled to make the structure uniformly spheroidized.

[0015] (4) Quenching and tempering treatment: After spheroidizing annealing, the temperature is raised to 900-950℃ at a rate of 50-200℃ / h, held for 2-4h, and then oil quenched to room temperature; during tempering, the temperature is raised to 150-400℃ and held for 2-5h.

[0016] In the preferred method for preparing the high-temperature resistant lightweight bearing steel, the spheroidizing annealing holding temperature is selected as 830–850℃.

[0017] The preferred method for preparing the high-temperature resistant lightweight bearing steel is as follows: the quenching heating rate is 100-200℃ / h, and the quenching holding temperature is 930-950℃.

[0018] In the preferred method for preparing the high-temperature resistant lightweight bearing steel, the tempering and heat preservation temperature is selected as 200-300℃.

[0019] The method for preparing the high-temperature resistant lightweight bearing steel describes a high-temperature resistant lightweight bearing steel with a density of 6.9–7.1 kg / m³. 3 .

[0020] The method for preparing the high-temperature resistant lightweight bearing steel described above results in a hardness ≥58HRC, yield strength ≥1850MPa, and tensile strength ≥2150MPa after long-term operation at 400℃.

[0021] The design concept of this invention is:

[0022] Based on the standard GCr15 bearing steel composition, this invention increases the C content to 1.2-1.5%, and adds 4-8% Al, as well as 0.01-0.05% La and Ce.

[0023] Al, as an alloying element, can hinder carbon diffusion when dissolved in the matrix, thus delaying the decomposition and coarsening of carbides. Simultaneously, Al forms an iron-aluminum phase with Fe, which exhibits a low aging rate at high temperatures, improving the high-temperature resistance of bearing steel. Furthermore, these iron-aluminum phases can also strengthen the matrix. However, the introduction of Al introduces a large number of non-metallic inclusions. Therefore, rare earth elements Ce and La are added to modify these inclusions and ensure material purity.

[0024] Meanwhile, as a ferrite-forming element, the introduction of large amounts of Al reduces the hardenability of bearing steel, leading to the inability to obtain a fully martensitic structure during the quenching process. Therefore, increasing the quenching temperature promotes complete austenitization during the solution treatment process, and increasing the C content yields a fully martensitic structure.

[0025] Furthermore, increasing the carbon content can further reduce the density of bearing steel, achieving a higher degree of lightweighting and improving the stress conditions during bearing operation. Changes in chemical composition inevitably lead to changes in the manufacturing process. This invention specifically optimizes and controls the entire manufacturing process of the developed high-temperature resistant lightweight bearing steel to obtain optimal performance, resulting in lightweight bearing steel with hardness and strength meeting the service requirements of bearing steel while also possessing good high-temperature resistance.

[0026] The advantages and beneficial effects of this invention are:

[0027] 1. The high-temperature resistant lightweight bearing steel developed in this invention only requires the addition of Al and trace rare earth elements, which is inexpensive; at the same time, the preparation process is simple, and many production and use experiences of high carbon chromium bearing steel can be transferred to the steel grade described above.

[0028] 2. The high-temperature resistant lightweight bearing steel developed in this invention has a density of 6.9–7.1 kg / m³. 3 Compared to traditional GCr15 bearing steel (7.81kg / m), 3It can reduce by about 10%. After long-term operation at 400℃, the hardness is ≥58HRC, the yield strength is ≥1850MPa, and the tensile strength is ≥2150MPa. While meeting the requirements of high strength and room temperature fatigue performance, it also has good high temperature resistance.

[0029] 3. Based on the optimization of composition, this invention has made targeted optimizations to the entire process of preparing the high-temperature resistant lightweight bearing steel. The prepared high-temperature resistant lightweight bearing steel has excellent performance, low preparation cost, and significant social and economic benefits. Attached Figure Description

[0030] Figure 1 This is the annealed microstructure of the high-temperature resistant lightweight bearing steel in Example 1.

[0031] Figure 2 The quenched microstructure of the high-temperature resistant lightweight bearing steel in Example 1 is shown.

[0032] Figure 3 The figure shows the hardness change of the high-temperature resistant lightweight bearing steel in Example 1 after long-term operation at 400°C. In the figure, the horizontal axis "Holding time" represents the holding time (h), and the vertical axis "Hardness" represents the hardness (HRC).

[0033] Figure 4 The figure shows the tensile curve of the high-temperature resistant lightweight bearing steel of Example 1 after long-term operation at 400°C. In the figure, the horizontal axis Elongation represents the elongation retention (%), and the vertical axis Strength represents the strength (MPa). Detailed Implementation

[0034] In its specific implementation, this invention proposes a high-temperature resistant lightweight bearing steel and its preparation method, including composition design and performance heat treatment, the specific steps of which are as follows:

[0035] (1) Smelting: Vacuum induction melting + vacuum degassing treatment to ensure the purity of molten steel; after vacuum degassing, rare earth alloy with a purity of 99.99wt.% or higher is added for final deoxidation and inclusion refinement treatment to finally meet the chemical composition requirements of high temperature resistant lightweight bearing steel, and high temperature resistant lightweight bearing steel ingots are cast.

[0036] In terms of chemical composition, compared with GCr15 bearing steel in the national standard, the following changes are mainly made: the C content is increased from 1.0 wt.% to 1.2-1.5 wt.%, 4-8 wt.% Al is added, and about 0.01-0.05 wt.% La and Ce are added. Other components remain consistent with the national standard.

[0037] (2) Forging: The high-temperature resistant lightweight bearing steel ingot that meets the composition requirements is subjected to three-dimensional forging treatment, and the forging temperature is controlled at 1000~1250℃.

[0038] (3) Spheroidizing annealing: After the steel is forged, spheroidizing annealing is performed. The heating temperature is selected as 800-850℃. After holding for 2-8 hours, the steel is slowly cooled in the furnace to make the structure uniformly spheroidized.

[0039] (4) Quenching and tempering treatment: After spheroidizing annealing, the temperature is raised to 900-950℃ at a rate of 50-200℃ / h, held for 2-4h, and then oil quenched to room temperature. The tempering temperature is 150-400℃, held for 2-5h, and then air cooled to room temperature.

[0040] The present invention will now be described in further detail through examples.

[0041] Example 1

[0042] In this embodiment, the high-temperature resistant lightweight bearing steel is smelted through vacuum induction melting and vacuum degassing. After vacuum degassing, high-purity rare earth alloys are added for treatment. After meeting the composition requirements, it is cast into steel ingots. The chemical composition of the obtained steel ingots is as follows:

[0043] C 1.34 Si 0.50 Mn 0.43 P 0.01 S 0.001 Al 6.05 Cr 1.20 Mo 0.05 La 0.010 Ce 0.008 Fe margin

[0044] The subsequent preparation steps are as follows: ① The obtained steel ingot is heated to 1200℃ at a heating rate of 100℃ / h and held for 6 hours, followed by triaxial forging. The ingot temperature is maintained at no less than 1000℃ throughout the forging process. ② After forging, spheroidizing annealing is performed. The forged billet is heated to 830℃ and held for 2 hours, then cooled to room temperature in the furnace. The annealed microstructure is shown in the figure. Figure 1 ③ Then, quenching treatment is performed. The material is heated to 940℃ at a rate of 150℃ / h and held for 2 hours. After that, it is oil-quenched and cooled to room temperature. The microstructure of the quenched state is shown in the figure. Figure 2 ④Then temper at 220℃ for 4 hours, and after the tempering is completed, air cool to room temperature.

[0045] After the above treatment, the properties of the obtained high-temperature resistant lightweight bearing steel are as follows:

[0046] The material density is 6.96 kg / m³. 3 After being placed in a high-temperature environment of 400℃ for 100 hours, the hardness is 59.1 HRC, the yield strength is 1946 MPa, and the tensile strength is 2190 MPa. (See attached image) Figures 3-4 .

[0047] Example 2

[0048] In this embodiment, the high-temperature resistant lightweight bearing steel is smelted through vacuum induction melting and vacuum degassing. After vacuum degassing, high-purity rare earth alloys are added for treatment. After meeting the composition requirements, it is cast into steel ingots. The chemical composition of the obtained steel ingots is as follows:

[0049] C 1.49 Si 0.41 Mn 0.28 P 0.007 S 0.002 Al 7.53 Cr 1.26 Mo 0.03 La 0.015 Ce 0.021 Fe margin

[0050] The subsequent preparation steps are as follows: ① The obtained steel ingot is heated to 1200℃ at a heating rate of 100℃ / h and held for 6 hours, followed by triaxial forging. The ingot temperature is maintained at no less than 1000℃ throughout the forging process. ② After forging, spheroidizing annealing is performed. The forged billet is heated to 850℃ and held for 3 hours, then cooled to room temperature in the furnace. ③ Quenching is then performed. The material is heated to 950℃ at a rate of 160℃ / h and held for 3 hours, followed by oil quenching and cooling to room temperature. ④ Subsequently, it is tempered at 240℃ and held for 5 hours, then air-cooled to room temperature after the holding period.

[0051] After the above treatment, the properties of the obtained high-temperature resistant lightweight bearing steel are as follows:

[0052] The material density is 6.92 kg / m³. 3 After being placed in a high-temperature environment of 400℃ for 100 hours, the hardness is 58.6HRC, the yield strength is 1865MPa, and the tensile strength is 2179MPa.

[0053] Example 3

[0054] In this embodiment, the high-temperature resistant lightweight bearing steel is smelted through vacuum induction melting and vacuum degassing. After vacuum degassing, high-purity rare earth alloys are added for treatment. After meeting the composition requirements, it is cast into steel ingots. The chemical composition of the obtained steel ingots is as follows:

[0055] C 1.24 Si 0.45 Mn 0.36 P 0.005 S 0.003 Al 5.27 Cr 1.32 Mo 0.06 La 0.008 Ce 0.009 Fe margin

[0056] The subsequent preparation steps are as follows: ① The obtained steel ingot is heated to 1200℃ at a heating rate of 100℃ / h and held for 6 hours, followed by triaxial forging. The ingot temperature is maintained at no less than 1000℃ throughout the forging process. ② After forging, spheroidizing annealing is performed. The forged billet is heated to 840℃ and held for 5 hours, then cooled to room temperature in the furnace. ③ Quenching is then performed. The material is heated to 930℃ at a rate of 120℃ / h and held for 4 hours, followed by oil quenching and cooling to room temperature. ④ Subsequently, it is tempered at 260℃ and held for 3 hours, then air-cooled to room temperature after the holding period.

[0057] After the above treatment, the properties of the obtained high-temperature resistant lightweight bearing steel are as follows:

[0058] The material density is 7.05 kg / m³. 3 After being placed in a high-temperature environment of 400℃ for 100 hours, the hardness is 59.2HRC, the yield strength is 1987MPa, and the tensile strength is 2263MPa.

[0059] The results of the examples show that the method for preparing high-temperature resistant lightweight bearing steel involved in this invention is reasonable and feasible, and the prepared high-temperature resistant lightweight bearing steel has excellent high-temperature resistance.

[0060] For those skilled in the art, various other corresponding changes can be made based on the above technical solutions and concepts, and all such changes should fall within the protection scope of the claims of this invention.

Claims

1. A method for preparing high-temperature resistant lightweight bearing steel, characterized in that, Its chemical composition by weight percentage is as follows: C 1.2-1.5%, Si 0.15-0.50%, Mn 0.25-0.45%, P≤0.02%, S≤0.02%, Al 4-8%, Cr 1.20-1.65%, Mo 0.02-0.08%, La and Ce 0.01-0.05%, with La 0.005-0.03%, Ce 0.005-0.03%, and Fe balance; The preparation method of the high-temperature resistant lightweight bearing steel includes smelting, forging, and performance heat treatment processes, with the specific steps as follows: (1) Smelting: Vacuum induction melting + vacuum degassing treatment to ensure the purity of molten steel; after vacuum degassing, high-purity rare earth alloy is added for final deoxidation and inclusion refinement treatment to finally meet the chemical composition requirements of high temperature resistant lightweight bearing steel, and high temperature resistant lightweight bearing steel ingots are cast. (2) Forging: The high-temperature resistant lightweight bearing steel ingot that meets the composition requirements is subjected to three-dimensional forging treatment, and the forging temperature is controlled at 1000~1250℃; (3) Spheroidizing annealing: After forging, spheroidizing annealing is performed. The holding temperature is selected as 800-850℃. After holding for 2-8 hours, the furnace is slowly cooled to make the structure uniformly spheroidized. (4) Quenching and tempering treatment: After spheroidizing annealing, heat to 900-950℃ at a rate of 50-200℃ / h, hold for 2-4h and then oil quench to room temperature; during tempering, heat to 150-400℃ and hold for 2-5h. The density of high-temperature resistant lightweight bearing steel is 6.9–7.1 kg / m³. 3 After long-term operation at 400℃, the hardness is ≥58HRC, the yield strength is ≥1850MPa, and the tensile strength is ≥2150MPa.

2. The method for preparing high-temperature resistant lightweight bearing steel according to claim 1, characterized in that, Preferably, the spheroidizing annealing holding temperature is selected as 830-850℃.

3. The method for preparing high-temperature resistant lightweight bearing steel according to claim 1, characterized in that, Preferably, the quenching heating rate is 100-200℃ / h, and the quenching holding temperature is 930-950℃.

4. The method for preparing high-temperature resistant lightweight bearing steel according to claim 3, characterized in that, Preferably, the tempering and heat preservation temperature is selected as 200-300℃.

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