Rare-earth-containing aviation bearing steel with excellent impact toughness and preparation method thereof

Abstract

The invention belongs to the technical field of alloy materials, and particularly relates to rare earth-containing aviation bearing steel with excellent impact toughness and a preparation method thereof. The rare earth-containing aircraft bearing steel with excellent impact toughness comprises the following chemical components in percentage by mass: 0.80%-0.85% of C, 0.15%-0.35% of Mn, 4.00%-4.25% of Cr, 4.00%-4.50% of Mo, 0.90%-1.10% of V, 0.04%-0.09% of RE, 0.10%-0.30% of Ni, 0.10%-0.30% of Si, 0.20%-0.50% of W, 0.01%-0.02% of Nb, 0.01%-0.04% of Al, less than or equal to 0.015% of P, less than or equal to 0.008% of S and the balance of Fe and inevitable impurities. The aircraft bearing steel containing the rare earth is prepared through vacuum induction melting, vacuum arc remelting, homogenizing annealing, hot working, spheroidizing annealing, quenching and two times of tempering, the content of impurity elements is low, and the material subjected to heat treatment has a smaller amount of high-temperature carbide, higher hardness and excellent impact toughness.

Description

Technical Field

[0001] The invention belongs to the technical field of alloy materials, and in particular relates to a rare earth-containing aviation bearing steel with excellent impact toughness and a preparation method thereof. Background Art

[0002] Bearings are one of the most important key basic components in the equipment manufacturing industry. They are called "joints of high-end equipment" and are widely used in various industrial production fields. With the rapid development of high-end industrial fields such as high-speed rail, aerospace, etc., the performance requirements of equipment for bearing materials are getting higher and higher. In particular, during the high-speed rotation of aircraft engine bearings, they must not only withstand high load pressure, but also withstand high ambient temperatures. The secondary hardening steel 8Cr4Mo4V can precipitate stable M2C carbides after high-temperature tempering, which can meet the working environment below 350°C. Therefore, it replaces the high-carbon chromium bearing steel GCr15 and becomes the second generation of aviation bearing steel.

[0003] Although aviation bearing steel generally adopts double vacuum smelting process, it has higher purity and composition uniformity than traditional bearing steel, but 8Cr4Mo4V bearing steel will precipitate a large number of large-sized primary carbides during solidification due to its high C, Cr, Mo, and V content, which are mainly metastable M2C primary carbides rich in Mo. Due to the large size of primary carbides, fatigue cracks are easily initiated at the interface between carbides and matrix and then expand, eventually leading to bearing fatigue failure. In addition, as the speed of aircraft engine bearings continues to increase, the DN value continues to increase. In addition to requiring bearing steel to have high temperature resistance, high hardness, wear resistance, and high fatigue resistance, it is also required to have good impact resistance.

[0004] The present invention aims to provide a rare earth-containing aviation bearing steel with excellent impact toughness and a preparation method thereof, by adding a certain content of elements to the existing 8Cr4Mo4V steel and adjusting its smelting, hot working and heat treatment processes, reducing dendrite segregation and inhibiting the growth of primary carbides, thereby improving its impact toughness. Summary of the invention

[0005] The purpose of the present invention is to provide a rare earth-containing aviation bearing steel with excellent impact toughness and a preparation method thereof, which not only has a small content of high-temperature carbides, but also has high hardness and excellent impact toughness.

[0006] In order to achieve the above object, the main technical solutions adopted by the present invention include: The first aspect of the present invention provides a rare earth-containing aviation bearing steel with excellent impact toughness, wherein the chemical components thereof are, by mass percentage, C 0.80%~0.85%, Mn 0.15%~0.35%, Cr 4.00%~4.25%, Mo 4.00%~4.50%, V0.90%~1.10%, RE 0.04%~0.09%, Ni 0.10%~0.30%, Si 0.10%~0.30%, W 0.20%~0.50%, Nb0.01%~0.02%, Al 0.01%~0.04%, P≤0.015%, S≤0.008%, and the balance is Fe and unavoidable impurities.

[0007] Preferably, the RE is a rare earth element, including one or more of lanthanum, cerium and yttrium.

[0008] In some preferred embodiments, the RE is any one of lanthanum and cerium; further preferably, the RE is cerium and lanthanum, and the mass ratio is (2-3):1; further, the RE is cerium, lanthanum and yttrium, and the mass ratio is (10-12):(4-5):1.

[0009] The selection of specific rare earth elements can not only improve the impact toughness of bearing steel, but also improve its fatigue resistance. This may be because the added rare earth elements can modify the aluminum-containing inclusions on the one hand to obtain rare earth oxysulfides and oxides, etc. Rare earth inclusions not only have lower hardness than alumina and are not easy to initiate cracks, which helps to improve the impact toughness and fatigue resistance of bearing steel, but also can precipitate at the grain boundary, hindering the migration of grain boundaries, thereby refining the grains; on the other hand, rare earth elements can inhibit the growth of M2C carbides at high temperatures, help reduce the size of primary carbides, and improve the impact resistance of bearing steel. In addition, the addition of rare earths can promote the dissolution of M2C carbides at high temperatures, reduce the number and area fraction of high-temperature carbides after quenching, help improve the impact resistance of bearing steel, and at the same time reduce the temperature of the quenching process, which helps to reduce the cost of heat treatment. In actual experiments, the addition of one rare earth element can also see the effect, but the addition of two or three or more rare earth elements is better, and there is a certain synergistic effect between them.

[0010] Preferably, the mass ratio of RE, Nb and Al is (2.5-2.8):(0.3-0.6):1.

[0011] By adjusting the mass ratio of RE, Nb, and Al, the grain size can be refined, the impact toughness of the bearing steel can be improved, and its hardness can be guaranteed. This may be because they have a synergistic effect. The combined effect of RE, Nb, and Al can significantly refine the grains. RE improves the distribution of inclusions, Nb forms stable carbides, and Al promotes grain refinement through deoxidation. Small and uniform grains can effectively prevent the expansion of cracks. The reduction of inclusions and the refinement of grains are helpful to improve the strength and impact toughness of the material. The refined grains and the formed carbides work together to improve the hardness of the material. The addition of RE improves the phase interface, and the presence of Nb and Al increases the number of hard phases, thereby ensuring the hardness of the bearing steel. In addition, the compounds of Nb and Al can maintain good stability at high temperatures, and work together with rare earth elements to reduce the aggregation and growth of carbides at high temperatures, thereby improving the performance of the material at high temperatures.

[0012] Preferably, the mass ratio of RE, V, Ni, Cr and Si is 1:(10-15):(2-3):(45-55):(2-3).

[0013] By adjusting the mass ratio of RE, V, Ni, Cr, and Si, the high-temperature carbide content can be further adjusted, and the hardness and impact toughness can be improved at the same time. This may be because these elements work synergistically. Vanadium and chromium work together to control the formation and stability of carbides, while rare earth elements optimize their precipitation behavior to make carbides smaller and more dispersed, thereby reducing the number and area fraction of high-temperature carbides. Nickel, rare earth elements, and silicon work together to promote grain refinement by providing heterogeneous nucleation sites and purifying grain boundaries. This not only enhances the strength of the material, but also improves its toughness. Vanadium, chromium, and nickel work together to not only form high-hardness VC carbides, but also indirectly improve hardness by improving hardenability and matrix strength. Nickel and rare earth elements work together to synergistically improve the impact toughness of aviation bearing steel by directly improving the plasticity and overall toughness of the material and indirectly reducing the risk of crack propagation by purifying grain boundaries.

[0014] Preferably, the mass ratio of C, V, Mo and W is (2.2-2.4):(2.7-2.8):(12-13):1.

[0015] By adjusting the mass ratio of C, V, Mo, and W, not only the amount and grain size of high-temperature carbides can be adjusted, but also the hardness can be improved and the impact toughness can be improved. This may be because carbon, vanadium, molybdenum, and tungsten work together in the formation process of carbides. By precisely controlling the carbon content and appropriately adding vanadium, molybdenum, and tungsten, the carbides can be made finer and more evenly distributed, thereby reducing undesirable high-temperature carbide types and improving the thermal stability of the material. Molybdenum and tungsten refine the grains through solid solution strengthening. At the same time, the carbides they form with carbon act as heterogeneous nucleation points, promoting the growth of finer and more uniform grains. The VC carbides formed by vanadium also further refine the grain structure. Carbon is the basis for the improvement of hardness, while the high-hardness carbides formed by vanadium, molybdenum, and tungsten further enhance the hardness of the material. These hard phases not only provide direct strength contributions, but also indirectly enhance the hardness of the matrix by hindering dislocation movement. In addition, molybdenum and tungsten can also improve the overall toughness and impact resistance of the material through solid solution strengthening and grain refinement.

[0016] The second aspect of the present invention provides a method for preparing the rare earth-containing aviation bearing steel with excellent impact toughness, comprising the following steps: S1. Vacuum induction melting: The raw materials are subjected to vacuum induction melting according to the mass percentage of chemical components, and rare earth elements are added 3-5 minutes before steel pouring; S2, vacuum arc remelting; S3, homogenization annealing: keep at 1150-1250℃ for 7-9h and then cool to room temperature; S4, hot working: multi-directional forging after keeping at 1100-1150℃ for 0.5 h, the final forging temperature is not less than 950℃, and then slowly cooled to room temperature; S5, spheroidizing annealing: keep at 800-830℃ for 3-5h, furnace cool to 530-550℃ and then air cool to room temperature; S6, quenching: 1090~1100℃ for 0.5 h and then air-cool to 50℃; S7. Tempering: Keep at 520~530℃ for 2-3 hours, then air cool to room temperature, repeat 2-3 times to obtain rare earth-containing aviation bearing steel.

[0017] Preferably, the specific conditions of the vacuum arc remelting are: melting current 2-3 kA, melting voltage 20-26 V, melting rate 1.0-1.5 kg / min.

[0018] Preferably, the multi-directional forging is three-pier and three-draw.

[0019] Through specific processes, the various properties of aviation bearing steel, especially impact toughness, are further improved. First, in the vacuum induction melting and vacuum arc remelting stages, the raw materials are ensured to be melted in a high-purity environment, which effectively reduces the introduction of impurities and gases, improves the purity of the steel, and enhances the overall toughness and mechanical properties of the material. Homogenization annealing helps to eliminate the microsegregation formed during the casting process, so that the alloy elements are more evenly distributed throughout the material, which is not only conducive to subsequent processing, but also improves the consistency of the mechanical properties of the final product. In the hot working stage, the heat preservation and three-pier three-drawing process at a specific temperature are adopted. Compared with ordinary processes such as two-pier two-drawing, three-pier three-drawing can more effectively refine the grains and improve the organizational structure, thereby increasing the strength and toughness of the material; at the same time, a higher number of forgings can further reduce internal defects and improve the comprehensive performance of the material. Spheroidizing annealing promotes the spheroidization of carbides, forming more uniform and fine carbide particles dispersed on the matrix, which not only improves the cutting performance of the material, but also enhances the toughness and reduces the risk of brittle fracture. Quenching enables the steel to obtain a martensitic structure, greatly improving the hardness and strength. Finally, two tempering treatments can effectively relieve quenching stress, adjust the organizational structure, and achieve the best balance between hardness and toughness. Compared with one tempering, it can better stabilize the microstructure of the material, further improve the impact toughness, and ensure the long-term stability of material properties.

[0020] The rare earth-containing aviation bearing steel with excellent impact toughness has a carbide area fraction in a quenched state of ≤1.6%, a room temperature hardness of ≥62 HRC, and a non-opening impact energy of ≥85 J.

[0021] Compared with the prior art, the advantages and beneficial effects of the present invention are: 1. The rare earth-containing aviation bearing steel with excellent impact toughness prepared by the present invention is prepared by adding a certain content of elements to the existing 8Cr4Mo4V steel and adjusting its smelting, hot working and heat treatment processes to reduce dendrite segregation and inhibit the growth of primary carbides, thereby improving its impact toughness.

[0022] 2. The rare earth elements added in the present invention can not only improve the impact toughness of the bearing steel, but also improve its rolling contact fatigue life, and at the same time can reduce the temperature of the quenching process, which helps to reduce the heat treatment cost.

[0023] 3. The present invention can refine the grain size, improve the impact toughness of the bearing steel and ensure its hardness by adjusting the mass ratio of RE, Nb and Al.

[0024] 4. The present invention can further control the content of high-temperature carbides and improve hardness and impact toughness by adjusting the mass ratio of RE, V, Ni, Cr and Si.

[0025] 5. The present invention can regulate the mass ratio of C, V, Mo and W, thereby not only regulating the amount and grain size of high-temperature carbides, but also increasing the hardness and improving the impact toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art.

[0027] Figure 1 It is the rare earth oxysulfide inclusion in the rare earth-containing aviation bearing steel with excellent impact toughness as described in Example 1 of the present invention.

[0028] Figure 2 It is the primary carbide with high Mo content in the rare earth-containing aviation bearing steel with excellent impact toughness as described in Example 1 of the present invention.

[0029] Figure 3 It is the high-temperature carbide of the rare earth-containing aviation bearing steel with excellent impact toughness after quenching as described in Example 1 of the present invention.

[0030] Figure 4 It is the rare earth oxysulfide inclusion in the rare earth-containing aviation bearing steel with excellent impact toughness as described in Example 2 of the present invention.

[0031] Figure 5 It is the primary carbide with high Mo content in the rare earth-containing aviation bearing steel with excellent impact toughness as described in Example 2 of the present invention.

[0032] Figure 6 It is the high-temperature carbide of the rare earth-containing aviation bearing steel with excellent impact toughness after quenching as described in Example 2 of the present invention.

[0033] Figure 7 It is the rare earth oxysulfide inclusion in the rare earth-containing aviation bearing steel with excellent impact toughness as described in Comparative Example 1 of the present invention.

[0034] Figure 8 It is the primary carbide with high Mo content in the rare earth-containing aviation bearing steel with excellent impact toughness as described in Comparative Example 1 of the present invention.

[0035] Fig. 9 It is a high-temperature carbide of the rare earth-containing aviation bearing steel with excellent impact toughness after quenching as described in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Example 1 The present embodiment provides a rare earth-containing aviation bearing steel with excellent impact toughness, and its chemical components, by mass percentage, are: C 0.83%, Mn 0.26%, Cr 4.24%, Mo 4.14%, V 0.95%, RE 0.079%, Ni 0.20%, Si0.20%, W 0.35%, Nb 0.02%, Al 0.03%, P 0.0086%, and S 0.0016%.

[0038] The RE is Ce.

[0039] The method for preparing the rare earth-containing aviation bearing steel with excellent impact toughness comprises the following steps: S1. Vacuum induction melting: vacuum induction melting is performed on the raw materials according to the mass percentage of chemical components, and rare earth elements are added 5 min before steel pouring; S2, vacuum arc remelting; S3, homogenization annealing: keep at 1200℃ for 8h and then cool to room temperature; S4, hot working: keep at 1122℃ for 0.5h, then do three forgings and three drawing, the final forging temperature is 950℃, and slowly cool to room temperature; S5, spheroidizing annealing: keep at 817℃ for 4h, furnace cool to 538℃ and then air cool to room temperature; S6, quenching: 1090℃ for 0.5 h and then air-cooled to 50℃; S7. Tempering: Keep at 520℃ for 2h and then air cool to room temperature, repeat this process twice to obtain rare earth-containing aviation bearing steel.

[0040] The specific conditions of the vacuum arc remelting are: melting current 2.5 kA, melting voltage 24 V, melting speed 1.2 kg / min.

[0041] Example 2 The difference between this embodiment and embodiment 1 is that the rare earth-containing aviation bearing steel with excellent impact toughness has the following chemical components, by mass percentage: C 0.80%, Mn 0.27%, Cr 4.20%, Mo 4.15%, V 0.93%, RE 0.076%, Ni 0.20%, Si 0.20%, W 0.35%, Nb 0.02%, Al 0.03%, P 0.0034%, and S 0.0012%.

[0042] The RE is Ce and La, and the mass ratio is 55:21.

[0043] Example 3 The difference between this embodiment and embodiment 1 is that the rare earth-containing aviation bearing steel with excellent impact toughness has the following chemical components, by mass percentage: C 0.83%, Mn 0.26%, Cr 4.24%, Mo 4.14%, V 0.95%, RE 0.08%, Ni 0.20%, Si 0.20%, W 0.35%, Nb 0.02%, Al 0.03%, P 0.0086%, and S 0.0016%.

[0044] The RE is Ce, La, and Y, and the mass ratio is 11:4:1.

[0045] Comparative Example 1 The difference between this comparative example and Example 1 is that the rare earth-containing aviation bearing steel with excellent impact toughness has the following chemical components, by mass percentage: C 0.83%, Mn 0.25%, Cr 4.22%, Mo 4.11%, V 0.93%, Ni 0.20%, Si0.20%, W 0.35%, Al 0.03%, P 0.0086%, and S 0.0016%.

[0046] Comparative Example 2 The difference between this comparative example and Example 1 is that the rare earth-containing aviation bearing steel with excellent impact toughness has the following chemical components, by mass percentage: C 0.83%, Mn 0.26%, Cr 4.24%, Mo 4.14%, V 0.95%, RE 0.079%, Ni 0.20%, Si 0.20%, W 0.35%, Nb 0.02%, P 0.0086%, and S 0.0016%.

[0047] Comparative Example 3 The difference between this comparative example and Example 1 is that the rare earth-containing aviation bearing steel with excellent impact toughness has the following chemical components, by mass percentage: C 0.83%, Mn 0.26%, Cr 4.24%, Mo 4.14%, V 0.95%, RE 0.079%, Si0.20%, W 0.35%, Nb 0.02%, Al 0.03%, P 0.0086%, and S 0.0016%.

[0048] Comparative Example 4 The difference between this comparative example and Example 1 is that the rare earth-containing aviation bearing steel with excellent impact toughness has the following chemical components, by mass percentage: C 0.83%, Mn 0.26%, Cr 4.24%, Mo 4.14%, V 0.95%, RE 0.079%, Ni 0.20%, Si 0.20%, Nb 0.02%, Al 0.03%, P 0.0086%, and S 0.0016%.

[0049] Comparative Example 5 The difference between this comparative example and Example 1 is that the preparation method of the rare earth-containing aviation bearing steel with excellent impact toughness comprises the following steps: S1. Vacuum induction melting: vacuum induction melting is performed on the raw materials according to the mass percentage of chemical components, and rare earth elements are added 5 min before steel pouring; S2, vacuum arc remelting; S3, homogenization annealing: keep at 1200℃ for 8h and then cool to room temperature; S4, hot working: keep at 1122℃ for 0.5h, then do three forgings and three drawing, the final forging temperature is 950℃, and slowly cool to room temperature; S5, spheroidizing annealing: keep at 817℃ for 4h, furnace cool to 538℃ and then air cool to room temperature; S6, quenching: 1090℃ for 0.5 h and then air-cooled to 50℃; S7. Tempering: Keep at 520℃ for 2h and then air cool to room temperature to obtain rare earth-containing aviation bearing steel.

[0050] Comparative Example 6 The difference between this comparative example and Example 1 is that the preparation method of the rare earth-containing aviation bearing steel with excellent impact toughness comprises the following steps: S1. Vacuum induction melting: vacuum induction melting is performed on the raw materials according to the mass percentage of chemical components, and rare earth elements are added 5 min before steel pouring; S2, vacuum arc remelting; S3, homogenization annealing: keep at 1200℃ for 8h and then cool to room temperature; S4, hot working: keep at 1122℃ for 0.5h, then do two forging and two drawing, the final forging temperature is 950℃, and slowly cool to room temperature; S5, spheroidizing annealing: keep at 817℃ for 4h, furnace cool to 538℃ and then air cool to room temperature; S6, quenching: 1090℃ for 0.5 h and then air-cooled to 50℃; S7. Tempering: Keep at 520℃ for 2h and then air cool to room temperature, repeat this process twice to obtain rare earth-containing aviation bearing steel.

[0051] Performance Testing The rare earth oxide sulfide inclusions, primary carbides with high Mo content and high temperature carbides after quenching in the bearing steels of Example 1, Example 2 and Comparative Example 1 were observed under a microscope. Figure 1~Figure 3 , Figure 4~Figure 6 , Figure 7~Figure 9 .contrast Figure 1 , Figure 4 , Figure 7 This shows that the rare earth addition amount and addition method adopted in the present invention have a good inclusion modification effect on bearing steel.

[0052] The average diameter and maximum diameter of primary carbides in the cast state of bearing steel are calculated in μm; the area fraction (in %), number density and number density (in mm) of high-temperature carbides in the quenched state of bearing steel are calculated. 2 ); Test the bearing steel hardness (in HRC) and the impact energy without opening (in J, refer to GB / T 229-2020 "Charpy Pendulum Impact Test Method for Metallic Materials" test). The results are shown in Table 1.

[0053] Table 1 Measurement results

[0054] According to statistics, the rare earth-containing aviation bearing steel prepared by Examples 1-3 of the present invention has finer primary carbides, and the number and volume of high-temperature carbides after heat treatment are smaller, and at the same time has higher impact toughness and hardness. Comparative Example 1 does not add RE, Comparative Example 2 does not add Al, Comparative Example 3 does not add Ni, Comparative Example 4 does not add W, Comparative Example 5 only performs one tempering, and Comparative Example 6 only performs two piercing and two drawing. The various indicators of the prepared aviation bearing steel still have gaps. Therefore, by adopting the method described in this application, by adding a certain amount of elements to the existing 8Cr4Mo4V steel, and adjusting its smelting, hot working and heat treatment processes, it is possible to reduce dendrite segregation, inhibit the growth of primary carbides, and thus improve its impact toughness and hardness.

[0055] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A rare earth-containing aviation bearing steel with excellent impact toughness, characterized in that: Calculated by mass percentage, its chemical composition is: C 0.80%~0.85%, Mn 0.15%~0.35%, Cr 4.00%~4.25%, Mo 4.00%~4.50%, V 0.90%~1.10%, RE 0.04%~0.09%, Ni 0.10%~0.30%, Si 0.10%~0.30%, W 0.20%~0.50%, Nb 0.01%~0.02%, Al0.01%~0.04%, P≤0.015%, S≤0.008%, and the balance is Fe and unavoidable impurities.

2. The rare earth-containing aviation bearing steel with excellent impact toughness according to claim 1, characterized in that: The RE is a rare earth element, including one or more of lanthanum, cerium, and yttrium.

3. The rare earth-containing aviation bearing steel with excellent impact toughness according to claim 1, characterized in that: The mass ratio of RE, Nb and Al is (2.5-2.8):(0.3-0.6):

1.

4. The rare earth-containing aviation bearing steel with excellent impact toughness according to claim 1, characterized in that: The mass ratio of RE, V, Ni, Cr and Si is 1:(10-15):(2-3):(45-55):(2-3).

5. The rare earth-containing aviation bearing steel with excellent impact toughness according to claim 1, characterized in that: The mass ratio of C, V, Mo and W is (2.2-2.4):(2.7-2.8):(12-13):

1.

6. The rare earth-containing aviation bearing steel with excellent impact toughness according to claim 1, characterized in that: The rare earth-containing aviation bearing steel with excellent impact toughness has a carbide area fraction in a quenched state of ≤1.6%, a room temperature hardness of ≥62 HRC, and a non-opening impact energy of ≥85 J.

7. A method for preparing rare earth-containing aviation bearing steel with excellent impact toughness according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Vacuum induction melting: The raw materials are subjected to vacuum induction melting according to the mass percentage of chemical components, and rare earth elements are added 3-5 minutes before steel pouring; S2, vacuum arc remelting; S3, homogenization annealing: keep at 1150-1250℃ for 7-9h and then cool to room temperature; S4, hot working: multi-directional forging after keeping at 1100-1150℃ for 0.5 h, the final forging temperature is not less than 950℃, and then slowly cooled to room temperature; S5, spheroidizing annealing: keep at 800-830℃ for 3-5h, furnace cool to 530-550℃ and then air cool to room temperature; S6, quenching: 1090~1100℃ for 0.5 h and then air-cool to 50℃; S7. Tempering: Keep at 520~530℃ for 2-3 hours, then air cool to room temperature, repeat 2-3 times to obtain rare earth-containing aviation bearing steel.

8. The method for preparing rare earth-containing aviation bearing steel with excellent impact toughness according to claim 7, characterized in that: The multi-directional forging is three-pier and three-draw.

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