A bearing steel and a method of smelting thereof

Abstract

The application discloses a kind of bearing steel, it contains Fe and inevitable impurities, in addition it also contains the following each chemical element with mass percentage content as follows: C:0.95-1.10%, Si:0.15-0.35%, Mn:0.25-0.50%, Cr:1.30-1.65%, Mg:0.0010-0.0015%, Al:0.01-0.03%, S:0.0013-0.0042%, 0 The application further discloses a smelting method of the bearing steel, which comprises the following steps: preliminary refining, refining and VD vacuum treatment to obtain a preliminary refined molten steel; feeding a magnesium-calcium-containing cored wire into the preliminary refined molten steel; and soft blowing the molten steel.

Description

Technical Field

[0001] This invention relates to a type of steel and its smelting method, and more particularly to a bearing steel and its smelting method. Background Technology

[0002] Bearings must withstand alternating loads and various instantaneous impact loads in harsh service environments. Therefore, high-quality bearing steel must not only have good wear resistance and structural stability, but also high fatigue resistance. During operation, because the rolling elements and bearing rings are in near-point contact, the alternating load is highly concentrated on a small area. Therefore, the main form of bearing failure is contact fatigue failure, such as pitting or fatigue cracks, at the contact surface.

[0003] Many defects in steel can become the source of fatigue cracks, such as oxides and banded carbides in non-metallic inclusions. Among them, Ds inclusions (magnesium aluminum spinel + calcium aluminate) are considered to be the defects that have the greatest impact on the fatigue life of bearing steel.

[0004] In the steelmaking process, bearing steel typically undergoes aluminum deoxidation, while calcium treatment is prohibited to avoid the formation of low-melting-point, easily growing calcium aluminates. However, during steelmaking, the molten steel continuously contacts the slag and refractory materials. Acid-soluble aluminum in the molten steel reacts with MgO in the slag and refractory materials, reducing Mg into the molten steel and combining with Al₂O₃ to form magnesium aluminum spinel. Furthermore, acid-soluble aluminum in the molten steel also reacts with CaO in the slag, reducing Ca into the molten steel and combining with magnesium aluminum spinel to form large-sized Ds inclusions. These inclusions are high-melting-point solid inclusions at the molten steel temperature, and during continuous casting, they easily adsorb and accumulate on the inner wall of the submerged entry nozzle, clogging the nozzle and affecting production.

[0005] Furthermore, because the coefficient of thermal expansion of Ds inclusions differs from that of the steel matrix, they are prone to stress concentration under alternating stress, thus becoming fatigue crack initiation points. The weak bonding surface between inclusions and steel also easily generates non-deformation tension, leading to void formation and consequently affecting the quality and performance of the bearing. Therefore, controlling aluminum and aluminum-calcium (magnesium) inclusions in bearing steel is crucial for improving the service life of bearing steel.

[0006] Optimizing the refining process can improve the size of inclusions in bearing steel, but the type of inclusions remains unchanged, still being the highly detrimental magnesium-aluminum spinel. Adding rare earth elements can modify the inclusions in bearing steel, but rare earth gold elements are highly reactive, making it difficult to guarantee yield after addition, and nozzle nodule formation becomes a key constraint on the continuous casting of rare earth bearing steel. High-carbon chromium bearing steel, with its excellent comprehensive properties, has broad prospects in aerospace, automotive, and robotics fields, and improving the type of inclusions in the steel is of great significance for further improving its fatigue performance. Existing patent literature covers the above-mentioned areas, including:

[0007] For example, Chinese patent document CN116752031A, published on September 15, 2023, entitled "A refining operation method for controlling Ds inclusions in bearing steel bars", discloses a refining operation method for controlling Ds inclusions in bearing steel bars. In the electric furnace / converter steel feeding process, aluminum blocks are added when 1 / 3 of the molten steel is added, followed by low-titanium high-carbon ferrochrome, low-aluminum low-titanium ferrosilicon and high-carbon ferromanganese in sequence. Then, pre-melted refining slag and active lime are added to control the basicity of the initial slag. In the early refining stage, aluminum wire is fed in for deep deoxidation as soon as the slag surface melts, followed by silicon carbide for diffusion deoxidation. Slag is then continuously slag-forming via electrolysis, and quicklime is added to control slag basicity. In the mid and late refining stages, silicon carbide is added for slag surface deoxidation and slag preservation to maintain a reducing atmosphere in the slag. Quicklime is added to maintain slag basicity, and the Al content in the molten steel is controlled at 0.030%-0.040%. The resulting bearing steel bars have a Ds inclusion level ≤ 0.5. However, the type of inclusions in the bearing steel remains unchanged, consisting of highly hazardous magnesium-aluminum spinel, and some bearing steel samples obtained in the examples still have a Ds inclusion level of 0.5.

[0008] For example, Chinese patent document CN118441120A, published on August 6, 2024, entitled "A Method for Modifying the Morphology of Inclusions in GCr15 Bearing Steel Using Rare Earth Ce," discloses a method for modifying the morphology of inclusions in GCr15 bearing steel using rare earth Ce. The method controls the endpoint C to be 0.08-0.15%, endpoint P ≤ 0.015%, endpoint S ≤ 0.025%, and endpoint Ti ≤ 0.0005%. The refining temperature for VD (Vacuum Deposition) is 1580-1600℃, the LF (Left-Flush) treatment time is ≥ 60 min, and the VD vacuum holding time is ≥ 15 min. After the VD vacuum treatment, 1-1.5 kg / t of an alloy containing 30% rare earth Ce is added, and soft blowing is performed for ≥ 15 min. Through modification of the bearing steel inclusions using rare earth, the ratings of inclusions in categories B, C, and D are significantly improved. However, the embodiments still contain inclusions larger than 15 μm, and the composition and modification mechanism of the modified inclusions were not considered. In addition, rare earth elements are relatively reactive, and the yield after their addition is difficult to guarantee.

[0009] For example, Chinese patent document CN117845012A, published on April 9, 2023, entitled "A Method for Controlling Inclusions in High-Energy Processed Bearing Steel," discloses a method for controlling inclusions in high-energy processed bearing steel. After vacuum distillation (VD), rare earth alloys are added to the molten steel, and argon gas is used for stirring. Simultaneously, plasma rays are injected into the molten steel, followed by continuous casting and rolling to obtain bearing steel. This method can stimulate the surface of sulfide and alumina inclusions in the molten steel to generate active sites, increasing surface activity and making it easier for rare earth elements to adhere and undergo chemical reactions. This results in a triple structure of manganese sulfide encapsulating alumina and rare earth elements encapsulating manganese sulfide. Furthermore, the bearing steel inclusions are small in size, uniformly distributed, and predominantly spherical or ellipsoidal. However, in this embodiment, the bearing steel's Ds inclusion level is still 0.5, and additional equipment is required, leading to higher production costs. Summary of the Invention

[0010] One of the objectives of this invention is to provide a bearing steel with excellent properties, especially excellent fatigue resistance.

[0011] To achieve the above objectives, the present invention provides a bearing steel containing Fe and unavoidable impurities, and further containing the following chemical elements in the following mass percentages:

[0012] C: 0.95-1.10%, Si: 0.15-0.35%, Mn: 0.25-0.50%, Cr: 1.30-1.65%, Mg: 0.0010-0.001 5%, Al: 0.01-0.03%, S: 0.0013-0.0042%, 0<N≤0.006%, 0<Ti≤0.0013%, 0<Ca≤0.0005%;

[0013] It does not contain Al inclusions.

[0014] Furthermore, in the bearing steel described in this invention, the mass percentage content of each chemical element is as follows:

[0015] C: 0.95-1.10%, Si: 0.15-0.35%, Mn: 0.25-0.50%, Cr: 1.30-1.65%, Mg: 0.0010-0.0015%, Al: 0.01-0.03%, S: 0.0013-0.0042%, 0 < N ≤ 0.006%, 0 < Ti ≤ 0.0013%, 0 < Ca ≤ 0.0005%; balance is Fe and unavoidable impurities.

[0016] In the technical solution described in this invention, the design principles of each chemical element are as follows:

[0017] C: In the bearing steel described in this invention, carbon (C) is the most critical element affecting its hardness and wear resistance. A high C content can significantly improve the steel's hardenability, hardness, and wear resistance. After heat treatment, C dissolves in martensite and forms a large number of dispersed carbides, which can meet the high hardness and high contact fatigue strength requirements of bearings. However, excessively high C content will reduce the steel's toughness and machinability. It should be noted that the higher the C content in the steel, the higher its strength, but the lower its toughness. Therefore, in the bearing steel described in this invention, the mass percentage content of C is controlled between 0.95% and 1.10%.

[0018] Si: In the bearing steel described in this invention, Si can improve the strength of the steel and enhance its tempering resistance to softening. An appropriate amount of Si also helps to inhibit pearlite transformation, promote martensite formation, and optimize the microstructure and properties after heat treatment. However, excessive Si content will reduce the plasticity and toughness of the steel. Therefore, in the bearing steel described in this invention, the mass percentage content of Si is controlled between 0.15% and 0.35%.

[0019] Mn: In the bearing steel described in this invention, Mn is mainly used to enhance hardenability and improve the uniformity of microstructure during heat treatment. Mn should be controlled at a moderate level to ensure hardenability while avoiding excessive inclusions. Therefore, in the bearing steel described in this invention, the mass percentage content of Mn is controlled between 0.25% and 0.50%.

[0020] Cr: In the bearing steel described in this invention, Cr is dissolved in the matrix to improve the hardenability of the steel. Furthermore, Cr is a carbide-forming element; Cr can replace Fe in carbides to form (Fe,Cr)3C, promoting the stability of spherical carbides and improving the strength of the steel. However, excessive Cr addition will make it difficult to dissolve and will also generate coarse M7C3 carbides. Therefore, in the bearing steel described in this invention, the mass percentage content of Cr is controlled between 1.30% and 1.65%.

[0021] Mg: Mg is a typical strong deoxidizing element. In the bearing steel described in this invention, Mg can modify traditional alumina inclusions and alumina-calcium inclusions. Micro-magnesium treatment of molten steel can effectively control the composition of non-metallic inclusions and effectively reduce the size of inclusions. However, excessive Mg content can easily lead to the formation of more inclusions. Therefore, in the bearing steel described in this invention, the mass percentage content of Mg is controlled between 0.0010-0.0015%.

[0022] Al: In the bearing steel described in this invention, Al is mainly used as a strong deoxidizer, thereby effectively reducing the oxygen content in the steel and improving its purity. In addition, Al has a certain grain-refining effect, inhibiting grain growth during austenitization and helping to improve the steel's toughness and uniformity. However, the aluminum content must be carefully controlled; excessive Al will form a large number of inclusions, reducing the steel's machinability and fatigue strength. Therefore, in the bearing steel described in this invention, the mass percentage content of Al is controlled between 0.01% and 0.03%.

[0023] S: In the bearing steel described in this invention, a certain amount of sulfur (S) is needed to combine with Ca and Mg in order to modify inclusions in the steel. However, excessive S content will deteriorate the performance of the steel. Therefore, in the bearing steel described in this invention, the mass percentage content of S element is controlled between 0.0013% and 0.0042%.

[0024] N: In the bearing steel described in this invention, N is a trace element. Excessive N content will lead to the formation of hard inclusions with Ti. Therefore, in the bearing steel described in this invention, the mass percentage content of N element is controlled to be below 0.006%.

[0025] Ti: In the bearing steel described in this invention, Ti is a trace element. Excessive Ti content will lead to the formation of TiN inclusions with high hardness, affecting the wear resistance and contact fatigue life of the bearing. Therefore, in the bearing steel described in this invention, the mass percentage content of Ti is controlled below 0.0013%.

[0026] Ca: In the bearing steel described in this invention, Ca is an impurity element in the steel, mainly originating from the reaction between molten steel and steel slag and refractory materials. To avoid the formation of large-sized calcium aluminate, the mass percentage content of Ca in the bearing steel described in this invention is controlled below 0.0005%.

[0027] Furthermore, in the unavoidable impurities of the bearing steel described in this invention: P ≤ 0.025%.

[0028] In the above technical solution, P represents an impurity element in the steel. When technical conditions permit, in order to obtain steel with better performance and higher quality, the content of impurity elements in the steel should be reduced as much as possible.

[0029] Furthermore, the inclusion size of the bearing steel described in this invention is less than 13 μm.

[0030] Furthermore, the inclusions in the bearing steel of the present invention include at least one of MgO-MgS inclusions, MgO-MgS-CaS inclusions, and TiN inclusions.

[0031] Furthermore, in the bearing steel described in this invention, MgO-MgS inclusions account for ≥80% of the total number of inclusions.

[0032] Furthermore, the fatigue life of the bearing steel described in this invention is ≥5×10⁻⁶. 7 Second-rate.

[0033] Another object of the present invention is to provide a method for smelting bearing steel, which can achieve the inclusion control desired by the present invention, thereby improving the fatigue life of bearing steel.

[0034] To achieve the above objectives, the present invention provides a method for smelting bearing steel, comprising the following steps:

[0035] Primary refining, refining, and VD vacuum treatment yield pre-refined molten steel;

[0036] VD degassing;

[0037] Feed the wire containing magnesium and calcium core.

[0038] Furthermore, in the smelting method described in this invention, the magnesium-calcium cored wire contains 20%-40wt% Mg, 5-15wt% Ca, 10-20wt% Si, and 25-50wt% aluminum.

[0039] In this invention, the design principles of each element in the magnesium-calcium cored wire are as follows:

[0040] Magnesium: Magnesium is a typical strong deoxidizing element, and its deoxidizing ability increases slightly with decreasing temperature. After deoxidation, in addition to precipitating MgO, MgS is also precipitated. It can also modify traditional alumina inclusions and alumina-calcium inclusions. Alumina inclusions, including oxide inclusions containing a small amount of MgO, are usually a source of Class B harmful inclusions, while alumina-calcium inclusions are usually a source of large, non-deformable Ds harmful inclusions. In addition, micro-magnesium treatment of molten steel can effectively control the composition of non-metallic inclusions and effectively reduce the size of inclusions. The magnesium-containing cored wire added in this invention contains 20-40% Mg, providing 15-20 ppm of dissolved Mg to the molten steel.

[0041] Calcium: Bearing steel is usually deoxidized with aluminum, and the resulting Al2O3 inclusions are prone to agglomeration, leading to nozzle nodules. The magnesium-containing cored wire added in this invention contains 5-15% Ca, which can be used to modify Al2O3 inclusions in high-temperature molten steel to ensure smooth casting, thereby providing 3-5 ppm of dissolved calcium to the molten steel.

[0042] Silicon: The presence of silicon in magnesium-core wire can be used to increase the Si content in steel, thereby significantly improving the hardenability of the steel. In addition, it can also effectively deoxidize.

[0043] Aluminum: In the smelting method described in this invention, adding aluminum to bearing steel can effectively deoxidize it. Therefore, in the smelting method described in this invention, the Al content is controlled at 25-50 wt%.

[0044] In this invention, Mg, as a stronger reducing element, can replace weakly reducing elements in oxides. Therefore, it can react with magnesium aluminum spinel (3Mg + MgAl₂O₄ → 4MgO + 2[Al]) and calcium aluminate (3Mg + CaAl₂O₄ → CaO + 3MgO + 2[Al]) to modify brittle and easily growing inclusions in bearing steel. Single Mg treatment often results in a violent reaction; therefore, a composite element cored wire is used to release Mg, Ca, and other elements. Furthermore, a certain amount of S is present in the molten steel. Ca will preferentially react with S to form CaS, and the remaining Mg will continue to react with S to form MgS.

[0045] Furthermore, in the smelting method described in this invention, the oxygen content in the preliminary refined molten steel is ≤6ppm; and / or the sulfur content in the preliminary refined molten steel is 15-40ppm.

[0046] The bearing steel and its smelting method described in this invention have the following advantages and beneficial effects compared to the prior art:

[0047] The bearing steel described in this invention is free of traditional harmful inclusions such as magnesium aluminum spinel, calcium aluminate, and alumina. Furthermore, all inclusions in the steel are MgO-MgS, MgO-MgS-CaS, and TiN inclusions with a size of less than 13 μm. These fine, dispersed inclusions are beneficial for improving the fatigue life of finished bearings and enhancing the mechanical properties of the steel.

[0048] In some embodiments, the present invention, combined with composition design and smelting methods, significantly improves the contact fatigue life of the resulting bearing steel, achieving a contact fatigue life ≥ 5 × 10⁻⁶ under 4.5 GPa Hertz stress. 7 Second-rate.

[0049] The bearing steel described in this invention uses 0.0015 to 0.0020% magnesium to accurately control the type of inclusions in the bearing steel. The inclusions are mostly in the form of fine MgO-MgS, with MgO-MgS inclusions accounting for ≥80% of all inclusions. This effectively avoids the presence of inclusions in the bearing steel in the form of magnesium aluminum spinel, calcium aluminate, and alumina, and eliminates large inclusions larger than 13μm caused by the composite precipitation of aluminum and aluminum calcium (magnesium) materials. As a result, the inclusions in the bearing steel are finer and more dispersed, and there are no macroscopic inclusions. Attached Figure Description

[0050] Figure 1 The diagram shows the types and dimensions of inclusions in the bearing steel billet of Embodiment 1 of the present invention.

[0051] Figure 2 The diagram shows the types and dimensions of inclusions in the bearing steel billet of Comparative Example 1. Detailed Implementation

[0052] The bearing steel and its smelting method described in this invention will be further explained and described below with reference to specific embodiments. However, such explanation and description do not constitute an improper limitation on the technical solution of this invention.

[0053] Examples 1-6 and Comparative Example 1

[0054] The bearing steel billets in Examples 1-6 were obtained using the following smelting steps:

[0055] (1) Primary refining, refining and VD vacuum treatment:

[0056] The molten iron undergoes primary refining in an electric furnace, followed by LF refining and VD vacuum treatment to obtain pre-refined molten steel. The oxygen content in the pre-refined molten steel is ≤6ppm, and the sulfur content is 15-40ppm.

[0057] (2) After the steel liquid is refined, it enters the VD degassing process. The vacuum holding time is 20 minutes. After the vacuum is broken, samples are taken, the temperature is measured, and the oxygen content is determined.

[0058] (3) Feed in magnesium-calcium cored wire, then transfer it to the continuous casting ladle turret to complete casting and solidification.

[0059] In some embodiments, the Mg content in the magnesium-calcium cored wire can be controlled to 20%-40wt%, the Ca content to 5-15wt%, the Si content to 10-20wt%, and the aluminum content to 25-50wt%.

[0060] The billet of Comparative Example 1 was obtained using the following process: molten iron was initially refined in an electric furnace, then refined by LF (electrolytic flux) and vacuum treated by VD (vacuum degassing) to obtain pre-refined molten steel with an O content of 5 ppm and an S content of 17 ppm. After refining, the molten steel entered a VD degassing chamber, where it was held under vacuum for 20 minutes. After the vacuum was broken, samples were taken, the temperature was measured, and the oxygen content was determined. Once the composition and temperature met the requirements, the steel was transferred to a continuous casting ladle turret, where casting and solidification were completed using the same parameters as in Example 1.

[0061] Table 1 lists the mass percentage of each chemical element in the bearing steel of Examples 1-6 of the present invention and the comparative steel of Comparative Example 1.

[0062] Table 1. (wt.%, balance Fe and other unavoidable impurities besides P and S)

[0063] serial number C Mn Si Cr Mg Al S N Ti Ca P Example 1 0.99 0.35 0.24 1.45 0.0010 0.0170 0.0015 0.0042 0.0009 0.0002 0.0120 Example 2 0.95 0.32 0.23 1.65 0.0015 0.0100 0.0035 0.0056 0.0010 0.0003 0.0153 Example 3 0.98 0.30 0.15 1.43 0.0012 0.0205 0.0016 0.0049 0.0007 0.0002 0.0209 Example 4 1.10 0.35 0.35 1.44 0.0012 0.0170 0.0042 0.0052 0.0013 0.0005 0.0148 Example 5 1.03 0.50 0.26 1.30 0.0013 0.0300 0.0024 0.0060 0.0009 0.0002 0.0115 Example 6 1.01 0.25 0.29 1.37 0.0011 0.0210 0.0013 0.0051 0.0006 0.0004 0.0250 Comparative Example 1 1.02 0.35 0.24 1.46 0.0003 0.019 0.0017 0.0053 0.0008 0.0003 0.0132

[0064] Table 2 lists the specific process parameters of the bearing steel of Examples 1-6 of the present invention and the comparative steel of Comparative Example 1.

[0065] Table 2.

[0066]

[0067] Note: Comparative Example 1 did not use magnesium-coated wire.

[0068] Samples were taken from the bearing steel billets of Examples 1-6 and the comparative billet of Comparative Example 1. After grinding and polishing, inclusions were automatically scanned by scanning electron microscopy, and the observation results are listed in Table 3.

[0069] Table 3.

[0070]

[0071] Figure 1 The diagram shows the types and dimensions of inclusions in the bearing steel billet of Embodiment 1 of the present invention.

[0072] like Figure 1 As shown in Example 1, inclusions in bearing steel were precisely controlled using a trace amount of 15 ppm Mg, and aluminum inclusions were modified. Scanning electron microscopy results showed that the maximum size of inclusions in the bearing steel billet was 11.4 μm, mainly MgO-MgS-CaS inclusions, and aluminum inclusions were no longer present.

[0073] Figure 2 The diagram shows the types and dimensions of inclusions in the bearing steel billet of Comparative Example 1.

[0074] like Figure 2 As shown, the inclusions in the bearing steel billet of Comparative Example 1 are mainly magnesium aluminum spinel and calcium aluminate inclusions. Scanning electron microscopy results show that the inclusions are typical spherical particles with very smooth boundaries and a maximum size exceeding 50 μm.

[0075] The bearing steel billets of Examples 1-6 and Comparative Example 1 were sampled again, and various performance tests were performed on them. The performance test results are listed in Table 4. Among them:

[0076] Fatigue life testing: The test was conducted according to GB10622-89, the rolling contact fatigue test method for metallic materials. The samples were prepared by grinding to obtain contact fatigue specimens with a surface roughness Ra≤0.2μm. The test was carried out on a rolling contact fatigue testing machine with a test load of 4.5GPa and a spindle speed of 1500r / min.

[0077] Table 4 lists the performance test results of the bearing steels of Examples 1-6 and the comparative steel of Comparative Example 1.

[0078] Table 4.

[0079] serial number Contact fatigue life (times) under 4.5 GPa Hertz stress Example 1 <![CDATA[1×10 8 ]]> Example 2 <![CDATA[5.2×10 7 ]]> Example 3 <![CDATA[7.8×10 7 ]]> Example 4 <![CDATA[1×10 8 ]]> Example 5 <![CDATA[6.6×10 7 ]]> Example 6 <![CDATA[7.1×10 7 ]]> Comparative Example 1 <![CDATA[1.2×10 7 ]]>

[0080] As can be seen from Table 3 above, the bearing steels of Examples 1-6 of the present invention all achieve a fatigue life of 5 × 10⁻⁶ under a stress of 4.5 GPa Hertz. 7 More than once, due to the modification of traditional magnesium aluminum spinel and calcium aluminate inclusions, the contact fatigue life of bearing steel is significantly improved.

[0081] Furthermore, the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0082] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A bearing steel containing Fe and unavoidable impurities, characterized in that, It also contains the following chemical elements in the following percentages by mass: C: 0.95-1.10%, Si: 0.15-0.35%, Mn: 0.25-0.50%, Cr: 1.30-1.65%, Mg: 0.0010-0.001 5%, Al: 0.01-0.03%, S: 0.0013-0.0042%, 0<N≤0.006%, 0<Ti≤0.0013%, 0<Ca≤0.0005%; It does not contain Al inclusions.

2. The bearing steel as described in claim 1, characterized in that, Its chemical element mass percentages are as follows: C: 0.95-1.10%, Si: 0.15-0.35%, Mn: 0.25-0.50%, Cr: 1.30-1.65%, Mg: 0.0010-0.0015%, Al: 0.01-0.03%, S: 0.0013-0.0042%, 0 < N ≤ 0.006%, 0 < Ti ≤ 0.0013%, 0 < Ca ≤ 0.0005%; the balance is Fe and unavoidable impurities.

3. The bearing steel as described in claim 1 or 2, characterized in that, In unavoidable impurities: P ≤ 0.025%.

4. The bearing steel as described in claim 1 or 2, characterized in that, The size of the inclusions is less than 13μm.

5. The bearing steel as described in claim 1 or 2, characterized in that, Its inclusions include at least one of MgO-MgS inclusions, MgO-MgS-CaS inclusions, and TiN inclusions.

6. The bearing steel as described in claim 5, characterized in that, Among them, MgO-MgS inclusions account for ≥80% of all inclusions.

7. The bearing steel as described in claim 1 or 2, characterized in that, Its fatigue life meets the requirement of ≥5×10 7 Second-rate.

8. The method for smelting bearing steel according to any one of claims 1-7, characterized in that, Including the following steps: Primary refining, refining, and VD vacuum treatment yield pre-refined molten steel; VD degassing; Feed the wire containing magnesium and calcium core.

9. The smelting method as described in claim 8, characterized in that, The magnesium-calcium cored wire contains 20%-40 wt% Mg, 5-15 wt% Ca, 10-20 wt% Si, and 25-50 wt% aluminum.

10. The smelting method as described in claim 8, characterized in that, The oxygen content in the preliminary refined molten steel is ≤6ppm; and / or the sulfur content in the preliminary refined molten steel is 15-40ppm.

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