A method for synergistically refining liquated carbides and inclusions in GCr15 bearing steel

Abstract

This invention discloses a method for synergistically refining liquid-precipitated carbides and inclusions in GCr15 bearing steel, belonging to the field of bearing steel smelting technology. In this method, Ce must be added first, followed by Mg. This order ensures that Ce preferentially reacts with O, S, and Al2O3 to form fine rare earth inclusions. The subsequent addition of Mg generates bubble flotation and a stirring effect, promoting the removal of inclusions by flotation. Simultaneously, Mg enriches at the solid-liquid interface, inhibiting carbide coarsening. If the order is reversed (Mg first, then Ce), Mg will be prematurely vaporized and lost, failing to exert its synergistic effect, and neither inclusions nor carbides will be refined.

Description

Technical Field

[0001] This invention belongs to the field of bearing steel smelting technology, and particularly relates to a method for synergistically refining liquid carbides and inclusions in GCr15 bearing steel. Background Technology

[0002] GCr15 bearing steel, a high-carbon chromium bearing steel (C: 0.95~1.05 wt.%, Cr: 1.40~1.65 wt.%), is typically produced using a process flow of electric arc furnace (EAF) or converter (BOF) → LF refining → VD / RH vacuum degassing → continuous casting or ingot casting → hot rolling → spheroidizing annealing. Under this process, the steel contains two types of harmful phases that severely impact fatigue life: one type is inclusions, mainly derived from deoxidation products (such as Al2O3 generated from aluminum deoxidation), MgO·Al2O3 spinel generated from secondary oxidation, and calcium aluminates entrained in ladle slag; the other type is liquid-precipitated carbides (primary carbides), which are formed during the solidification of molten steel due to solute redistribution in the interdendritic region, precipitating as M3C-type carbides in the final solidification stage. For a long time, the control effects of the two types of harmful phases mentioned above have been insufficient to meet the stringent requirements of high-end bearings (such as high-speed rail bearings, wind turbine main shaft bearings, and aerospace bearings) for ultra-long life and high reliability. The specific manifestations are as follows: 1. Under traditional aluminum deoxidation processes, the Al2O3 inclusions formed in GCr15 bearing steel are mostly irregular blocks or clusters, with high hardness and poor plasticity. Their coefficients of thermal expansion differ significantly from the steel matrix, making them prone to stress concentration at the inclusion / matrix interface under alternating loads, thus becoming preferential initiation points for fatigue cracks. To improve the inclusion morphology, calcium treatment is often used industrially to modify Al2O3 into low-melting-point calcium aluminates (such as 12CaO·7Al2O3). However, these inclusions tend to exhibit irregular shapes due to cooling shrinkage during the solidification of molten steel, and their size often reaches 10~30 μm, still failing to meet the requirements of bearing steel for small, spherical inclusions. Some companies have attempted single rare earth (Ce or La) treatment, which can transform Al2O3 into rare earth oxides or rare earth oxysulfides. However, because the density of rare earth inclusions is similar to that of molten steel and their solidification rate is slow, they easily aggregate and grow towards the end of solidification, resulting in coarse rare earth inclusions of 20-50 μm, or even large-particle rare earth inclusion defects. While single magnesium treatment can transform MgO·Al2O3 spinel into finer, high-melting-point MgO particles, magnesium has a low boiling point (1090 ℃) and high vapor pressure, leading to highly unstable yields in molten steel. Furthermore, magnesium treatment alone has limited effect on reducing the number of inclusions, leaving some irregularly shaped composite inclusions. Therefore, existing inclusion control technologies have consistently failed to reliably obtain a large number of fine (<5 μm), spherical, and diffusely distributed non-metallic inclusions.

[0003] 2. GCr15 bearing steel has high carbon and chromium content and a wide solidification range (approximately 1450 ℃ to 1250 ℃). In the solid-liquid two-phase region, strong carbon and chromium segregation occurs between dendrites, ultimately resulting in the precipitation of coarse liquid carbides during the eutectic reaction stage. In typical production, these liquid carbides are in the form of blocks, lamellar sheets, or networks, with lengths typically ranging from 40 to 80 μm, and some exceeding 100 μm. Their hardness is much higher than the matrix. Although they can partially break down during subsequent hot rolling or forging, they cannot be completely eliminated and remain as short rods or fragments, becoming rapid pathways for fatigue crack propagation. To mitigate the harmful effects of liquid carbides, current technologies generally employ high-temperature diffusion annealing, heating the billet to 1200–1250 ℃ and holding it for 10–30 hours. This high temperature accelerates carbon atom diffusion, causing partial spheroidization of the carbides and reducing dendrite segregation. However, this process has significant drawbacks: First, it consumes extremely high energy, increasing the cost per ton of steel by approximately 200-400 yuan; second, prolonged high-temperature heating leads to severe oxidation and decarburization on the surface of the steel billet, reducing the yield by 3-5%; third, even after high-temperature diffusion annealing, the size of the precipitated carbides can only be reduced from about 60 μm to 30-40 μm, still far exceeding the critical size allowed for high-performance bearings (generally considered to be less than 15 μm). More importantly, high-temperature diffusion annealing can only passively improve the morphology of the precipitated carbides, but cannot inhibit the nucleation and growth of precipitated carbides during solidification at the source.

[0004] 3. The rolling contact fatigue life of bearing steel is affected by both inclusions and precipitated carbides. In traditional processes, coarse, irregular inclusions and coarse precipitated carbides coexist, and the two are interdependent: micro-segregation of alloying elements usually exists around the inclusions, promoting the precipitation of carbides near the inclusions, forming an inclusion-carbide composite defect region. The local stress concentration factor in this region is much greater than that of either defect alone. Currently, industrially produced GCr15 bearing steel, under the condition of meeting cleanliness standards (total oxygen content ≤ 8 ppm), has a rated life L... 10 The reliability (90%) is often only 50% to 60% of the theoretical calculation value, with a large dispersion and a high proportion of early failures. For this reason, long-life applications such as high-speed rail bearings and wind turbine main shaft bearings still rely on imported high-end bearing steel. The key technological bottleneck lies in the inability to simultaneously refine inclusions and liquid carbides. Although metallurgists have developed modification technologies for inclusions (such as rare earth treatment, magnesium treatment, and calcium treatment) and high-temperature diffusion processes for carbides, these technologies are independent and even mutually restrictive. For example, while rare earth treatment can modify inclusions, it may promote heterogeneous nucleation of carbides along the rare earth inclusion interface, thus exacerbating carbide coarsening; and high-temperature diffusion annealing may lead to the growth of the modified inclusions or deterioration of their morphology. Therefore, there is an urgent need to develop a method that can achieve "synergistic refinement control" of inclusions and liquid carbides. Summary of the Invention

[0005] This invention proposes a method for synergistically refining liquid carbides and inclusions in GCr15 bearing steel to address the following key technical challenges in existing technologies: First, single deoxidation and inclusion modification processes (such as aluminum deoxidation, calcium treatment, single rare earth treatment, or single magnesium treatment) cannot effectively achieve the refinement, spheroidization, and dispersion of non-metallic inclusions. Inclusions still exhibit irregular blocky, clustered, or aggregated growth, with sizes generally exceeding 10 μm, becoming preferential sources of fatigue crack initiation. Second, existing processes lack source suppression methods for the coarse liquid carbides (typically 40-80 μm in size) formed during the solidification of GCr15 steel. Furthermore, subsequent high-temperature diffusion annealing is energy-intensive, has low yield, and cannot refine the liquid carbides to the ideal size (<15 μm). (μm); thirdly, inclusions and liquid carbides form a composite defect region in the steel. The superposition effect of the two leads to the rolling contact fatigue life of bearing steel being far lower than the theoretical value, with a high proportion of early failures, making it difficult to meet the urgent demand for high performance in high-end equipment such as high-speed rail bearings, wind power main shaft bearings, and aerospace bearings.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for synergistically refining liquid carbides and inclusions in GCr15 bearing steel includes the following steps: Step 1: Steel melting and initial deoxidation After initial refining in an electric arc furnace or converter, GCr15 bearing steel raw material is transferred to an LF refining furnace. Conventional aluminum deoxidation processes are used to initially remove dissolved oxygen from the molten steel to a total oxygen content ≤15 ppm, controlling the Al content in the molten steel to 0.001~0.005 wt.%. Step 2: Ce processing (add first) At the end of LF refining or the beginning of VD / RH vacuum treatment, rare earth Ce is added to the molten steel at a rate of 0.01~0.05 wt.% (i.e. 100~500 ppm) based on the mass of the molten steel. After addition, the mixture is stirred evenly under vacuum or inert gas protection to allow Ce to fully react with residual oxygen, sulfur and Al2O3 inclusions in the molten steel, generating fine and dispersed Ce2O2S and CeAlO3 rare earth inclusions. Step 3: Mg treatment (added later) After Ce treatment is completed and fully reacted, metallic Mg is added to the molten steel obtained in step 2. The amount added is 0.01~0.02 wt.% (100~200 ppm) based on the mass of the molten steel. After addition, strong stirring is started immediately. Taking advantage of the low boiling point of Mg (boiling point 1090 ℃), it rapidly vaporizes at the temperature of the molten steel (1500~1600 ℃), generating a large number of fine magnesium vapor bubbles. The magnesium vapor bubbles float fully and play the following roles: (a) Bubble flotation: adsorbs the fine rare earth inclusions that have been generated and carries them to the slag layer for removal, avoiding the agglomeration and growth of rare earth inclusions; (b) Stirring purification: enhances the flow of molten steel and promotes the transformation of residual Al2O3 and spinel into MgO or MgO·Ce2O3 composite inclusions; (c) Carbide inhibition: Mg is enriched at the solid-liquid interface, increasing the supercooling of the composition. It is adsorbed on the growth steps of liquid carbide, hindering the diffusion of carbon atoms and promoting the dispersion and refinement of carbides. Step 4: Vacuum degassing and solidification control After step 3, VD / RH vacuum degassing is performed, followed by continuous casting or ingot casting; during solidification, the cooling rate is controlled at 5~20℃ / min to allow the liquid carbides to precipitate under dispersed nucleation conditions, and finally obtains GCr15 bearing steel billets with liquid carbide size ≤25 μm and inclusion size ≤3 μm.

[0007] In the method for synergistically refining liquid carbides and inclusions in GCr15 bearing steel according to this invention, Ce must be added first, followed by Mg. This order ensures that Ce preferentially reacts with O, S, and Al2O3 to form fine rare earth inclusions. The subsequent addition of Mg generates bubble flotation and a stirring effect, promoting the removal of inclusions by flotation. Simultaneously, Mg enriches at the solid-liquid interface, inhibiting carbide coarsening. If the order is reversed (Mg first, then Ce), Mg will be prematurely vaporized and lost, failing to exert its synergistic effect, and neither inclusions nor carbides will be refined.

[0008] In the method for synergistically refining liquid carbides and inclusions in GCr15 bearing steel according to the present invention, the addition order of Ce and Mg is specified as Ce first, followed by Mg. Through the synergistic metallurgical effect of this specific order, the following specific objectives are achieved simultaneously: (1) The inclusions such as Al2O3, MgO·Al2O3 spinel and calcium aluminate are transformed into fine (average size <3 μm), spherical and diffusely distributed Ce-OS-Mg composite inclusions to avoid the inclusions from agglomerating and growing. (2) Inhibit the nucleation and coarsening of liquid carbides from the solidification source, transforming them from coarse lamellar or blocky to fine (10~20 μm), diffuse granular or short rod-shaped, significantly reducing the harmfulness of carbides; (3) By using the synergistic effect of double refinement, the coupling and superposition hazards between inclusions and carbides are eliminated or weakened, which improves the mechanical properties of GCr15 bearing steel by 5-10% compared with the traditional single processing process, and significantly shortens or even eliminates the subsequent high-temperature diffusion annealing process, thereby reducing production costs and realizing low-cost, short-process manufacturing of high-performance bearing steel.

[0009] Furthermore, in step 1, the raw material for the GCr15 bearing steel includes scrap steel, pig iron, or molten iron.

[0010] Furthermore, in step 2, the rare earth Ce is added in the form of pure Ce or Ce-Fe alloy.

[0011] Furthermore, the mass fraction of Ce in the Ce-Fe alloy is 10~30%.

[0012] Furthermore, in step 2, after adding the rare earth Ce to the molten steel, the stirring time is 5 to 10 minutes.

[0013] Furthermore, in step 3, the strong stirring is bottom-blowing argon gas or electromagnetic stirring, and the stirring time is controlled at 5 to 15 minutes.

[0014] Furthermore, the bottom-blown argon flow rate is ≥0.3 Nm³. 3 / h·t steel; electromagnetic stirring power ≥200 kW.

[0015] Furthermore, in step 4, when performing the vacuum degassing, the vacuum degree is ≤67 Pa and the processing time is 15~25 minutes.

[0016] The present invention also provides an application of GCr15 bearing steel obtained according to the above method in high-speed rail bearings, wind turbine main shaft bearings and aerospace bearings.

[0017] Compared with existing technologies, the Ce-Mg composite treatment method (Ce first, then Mg) provided by this invention has achieved the following significant technical effects in GCr15 bearing steel: 1. Refinement and spheroidization of inclusions After treatment with this invention, the non-metallic inclusions in the steel are mainly submicron to 3 μm spherical Ce-OS-Mg composite inclusions (such as Ce2O2S, MgO·Ce2O3), with an average equivalent diameter ≤2.5 μm. Compared with single Ce treatment and single Mg treatment, the inclusion size is reduced by more than 60%, and the number density is greatly improved, exhibiting a dispersed distribution.

[0018] 2. The liquid-precipitated carbides are significantly refined. This invention suppresses the coarsening of liquid carbides at the solidification source. In GCr15 bearing steel billets treated with this invention, the liquid carbides change from the lamellar or blocky (40-80 μm) form of traditional processes to dispersed granular or short rod-shaped (20-30 μm) forms. The maximum size of the carbides is reduced by more than 40-50%, the area fraction is reduced by 30-40%, and they no longer form a continuous network or chain distribution.

[0019] 3. Reduce production costs and energy consumption Because this invention refines the liquid carbides from the source, it can eliminate or shorten the traditional high-temperature diffusion annealing process (1200~1250 ℃, 10~30 h), saving 200~400 yuan of energy per ton of steel, while reducing the depth of the surface oxidation decarburization layer and increasing the yield by 3~5%.

[0020] 4. High process stability Compared with the process of treating Mg first and then Ce, the present invention (treating Ce first and then Mg) reduces the high-temperature burn-off of Mg, stabilizes the Ce yield at 60-80%, increases the effective utilization rate of Mg by more than 2 times, and has a wider process window, making it suitable for industrial mass production. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The images show the morphology of liquid carbides in the experimental steels. (a) is the blank experimental steel (i.e., GCr15 bearing steel without any treatment), (b) is Example 1, and (c) is Example 2. Figure 2 The area ratio and maximum size of the liquid carbides in the experimental steel are shown. 1# is the blank experimental steel, 2# is Example 1, and 3# is Example 2. Figure 3 The values ​​represent the average size and number density of inclusions in the experimental steel. 1# represents the blank experimental steel, 2# represents Example 1, and 3# represents Example 2. Figure 4 The microstructures of liquid carbides and inclusions in the experimental steel are shown in (1) blank experimental steel, (2) Example 1, and (3) Example 2. Figure 5 The hardness and tensile strength of the blank experimental steel and the experimental steels of Examples 1-2 are shown. Figure 6 The microstructures of liquid carbides and inclusions in the experimental steels of Comparative Examples 1 to 4 are shown. (1) is Comparative Example 1, (2) is Comparative Example 2, (3) is Comparative Example 3, and (4) is Comparative Example 4. Detailed Implementation

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0023] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0025] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0026] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0027] This invention provides a method for synergistically refining liquid carbides and inclusions in GCr15 bearing steel. The method employs a composite treatment of rare earth elements Ce and Mg on the GCr15 bearing steel, strictly controlling the order of addition: Ce is added to the molten steel first, followed by Mg. The specific steps are as follows: Step 1: Steel melting and initial deoxidation After initial refining in an electric arc furnace or converter, GCr15 bearing steel raw material is transferred to an LF refining furnace. Conventional aluminum deoxidation processes are used to initially remove dissolved oxygen from the molten steel to a total oxygen content ≤15 ppm, controlling the Al content in the molten steel to 0.001~0.005 wt.%. Step 2: Ce processing (add first) At the end of LF refining or the beginning of VD / RH vacuum treatment, rare earth Ce is added to the molten steel at a rate of 0.01~0.05 wt.% (i.e. 100~500 ppm) based on the mass of the molten steel. After addition, the mixture is stirred evenly under vacuum or inert gas protection to allow Ce to fully react with residual oxygen, sulfur and Al2O3 inclusions in the molten steel, generating fine and dispersed Ce2O2S and CeAlO3 rare earth inclusions. Step 3: Mg treatment (added later) After Ce treatment is completed and fully reacted, metallic Mg is added to the molten steel obtained in step 2. The amount added is 0.01~0.02 wt.% (100~200 ppm) based on the mass of the molten steel. After addition, strong stirring is started immediately. Taking advantage of the low boiling point of Mg (boiling point 1090 ℃), it rapidly vaporizes at the temperature of the molten steel (1500~1600 ℃), generating a large number of fine magnesium vapor bubbles. The magnesium vapor bubbles float fully and play the following roles: (a) Bubble flotation: adsorbs the fine rare earth inclusions that have been generated and carries them to the slag layer for removal, avoiding the agglomeration and growth of rare earth inclusions; (b) Stirring purification: enhances the flow of molten steel and promotes the transformation of residual Al2O3 and spinel into MgO or MgO·Ce2O3 composite inclusions; (c) Carbide inhibition: Mg is enriched at the solid-liquid interface, increasing the supercooling of the composition. It is adsorbed on the growth steps of liquid carbide, hindering the diffusion of carbon atoms and promoting the dispersion and refinement of carbides. Step 4: Vacuum degassing and solidification control After step 3, VD / RH vacuum degassing is performed, followed by continuous casting or ingot casting; during solidification, the cooling rate is controlled at 5~20℃ / min to allow the liquid carbides to precipitate under dispersed nucleation conditions, and finally obtains GCr15 bearing steel billets with liquid carbide size ≤25 μm and inclusion size ≤3 μm.

[0028] This invention primarily addresses the technical problems of irregular and numerous inclusions, coarse liquid carbides, and insufficient fatigue life in existing GCr15 bearing steel. It is applicable to the industrial production of various types of GCr15 bearing steel and can improve the overall mechanical properties of bearing steel. If Mg is added first and then Ce, the Mg is prematurely vaporized and lost at high temperatures. Subsequently, Ce reacts with residual MgO to form clustered composite inclusions, leading to coarsening of the inclusions (the appearance of large particles ≥8 μm). Furthermore, the size of the liquid carbides remains above 40 μm, making it impossible to achieve dual refinement of both the liquid carbide and inclusion sizes.

[0029] In this invention, Ce modifies inclusions and influences the heterogeneous nucleation of liquid carbides, while Mg purifies the molten steel through bubble stirring and accumulates at the solid-liquid interface to inhibit carbide growth. The synergistic effect of these two processes achieves simultaneous reduction in the size and optimization of the morphology of both inclusions and liquid carbides. This is an essential characteristic that distinguishes it from all single or non-sequential composite treatments.

[0030] In this invention, the amount of Ce added is 0.01~0.05 wt.%, and the amount of Mg added is 0.01~0.02 wt.%. Below the lower limit, the double refining effect is not significant; above the upper limit, it leads to the aggregation of inclusions or the coarsening of carbides again.

[0031] In a preferred embodiment of the present invention, in step 1, the raw material for GCr15 bearing steel includes scrap steel, pig iron, or molten iron.

[0032] In a preferred embodiment of the present invention, in step 2, the rare earth Ce is added in the form of pure Ce or Ce-Fe alloy.

[0033] For example, the mass fraction of Ce in a Ce-Fe alloy is 10 to 30%.

[0034] In a preferred embodiment of the present invention, in step 2, after adding rare earth Ce to the molten steel, the stirring time is 5 to 10 minutes.

[0035] In a preferred embodiment of the present invention, in step 3, the strong stirring is performed using bottom-blowing argon gas or electromagnetic stirring, and the stirring time is controlled to be 5-15 minutes. After adding Mg, strong stirring is necessary to fully utilize the flotation and macroscopic stirring effects of magnesium vapor bubbles. The stirring time after adding Mg is 5-15 minutes; too short a time will result in insufficient reaction, while too long a time will cause secondary oxidation of the molten steel.

[0036] In a preferred embodiment of the present invention, the bottom-blown argon flow rate is ≥0.3 Nm³. 3 / h·t steel; electromagnetic stirring power ≥200kW.

[0037] In a preferred embodiment of the present invention, in step 4, when performing vacuum degassing, the vacuum degree is ≤67 Pa and the processing time is 15~25 minutes.

[0038] An exemplary method for synergistically refining liquid carbides and inclusions in GCr15 bearing steel includes the following steps: Step 1: Steel melting and initial deoxidation After the raw materials of GCr15 bearing steel (including scrap steel, pig iron or molten iron) are initially refined in an electric arc furnace or converter, they are transferred to an LF refining furnace. The dissolved oxygen in the molten steel is initially removed to a total oxygen content of ≤15 ppm using a conventional aluminum deoxidation process, and the Al content in the molten steel is controlled to be 0.001~0.005 wt.%.

[0039] Step 2: Ce processing (add first) At the end of LF refining or the beginning of VD / RH vacuum treatment, rare earth Ce is added to the molten steel in the form of pure Ce or Ce-Fe alloy (Ce mass fraction 10~30%), at a rate of 0.01~0.05 wt.% (i.e. 100~500 ppm) based on the mass of the molten steel. After addition, the mixture is stirred for 5~10 minutes under vacuum or inert gas protection to allow Ce to fully react with residual oxygen, sulfur, and Al2O3 inclusions in the molten steel, generating fine and dispersed Ce2O2S and CeAlO3 rare earth inclusions.

[0040] Step 3: Mg treatment (added later) After Ce treatment is completed and the reaction is complete, metallic Mg is added to the molten steel at a rate of 0.01~0.02 wt.% (100~200 ppm) based on the mass of the molten steel. Immediately after addition, strong stirring (such as bottom-blowing argon or electromagnetic stirring) is started. Taking advantage of Mg's low boiling point (1090 ℃), it rapidly vaporizes at the temperature of the molten steel (1500~1600 ℃), generating a large number of fine magnesium vapor bubbles. The stirring time is controlled at 5-15 minutes to allow magnesium vapor bubbles to float fully and play the following roles: (a) Bubble flotation: adsorbs the fine rare earth inclusions that have been generated, carries them to float quickly to the slag layer and removes them, and avoids the rare earth inclusions from agglomerating and growing; (b) Stirring purification: enhances the flow of molten steel and promotes the transformation of residual Al2O3 and spinel into MgO or MgO·Ce2O3 composite inclusions; (c) Carbide inhibition: Mg is enriched at the front of the solid-liquid interface, increases the supercooling of the composition, adsorbs on the growth steps of liquid carbide, hinders the diffusion of carbon atoms, and promotes the dispersion and refinement of carbides.

[0041] Step 4: Vacuum degassing and solidification control After composite treatment, VD / RH vacuum degassing is performed (vacuum degree ≤67 Pa, treatment time 15~25 minutes), followed by continuous casting or ingot casting. During solidification, the cooling rate is controlled (5~20℃ / min) to allow the liquid carbides to precipitate under dispersed nucleation conditions, ultimately obtaining GCr15 bearing steel billets with liquid carbide size ≤25 μm and inclusion size ≤3 μm.

[0042] Embodiments of the present invention also provide an application of GCr15 bearing steel obtained according to the above method in high-speed rail bearings, wind turbine main shaft bearings, and aerospace bearings.

[0043] In the following embodiments and comparative examples of the present invention, the GCr15 bearing steel raw material (experimental steel) used is pig iron, which, by mass percentage, includes the following components: C 0.96wt.%, Si 0.27wt.%, Mn 0.46wt.%, Cr 1.58wt.%, P 0.010wt.%, S 0.007wt.%, with the balance being Fe and unavoidable impurities.

[0044] Unless otherwise specified, the room temperature in this invention is 25±2℃.

[0045] All raw materials used in the embodiments of the present invention were obtained through commercial purchase.

[0046] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0047] The technical solution of the present invention will be further illustrated by the following embodiments.

[0048] Example 1 A method for synergistically refining liquid carbides and inclusions in GCr15 bearing steel, comprising the following steps: Step 1: Steel melting and initial deoxidation After the GCr15 bearing steel raw material (pig iron) is initially refined in an electric arc furnace, it is transferred to an LF refining furnace. The dissolved oxygen in the molten steel is initially removed to a total oxygen content of ≤15 ppm using a conventional aluminum deoxidation process, and the Al content in the molten steel is controlled to be 0.002 wt.%.

[0049] Step 2: Ce processing (add first) At the end of LF refining, rare earth Ce is added to the molten steel in the form of pure Ce, at a rate of 0.045 wt.% (450 ppm) based on the mass of the molten steel. After addition, the mixture is stirred under vacuum for 10 minutes to allow Ce to fully react with residual oxygen, sulfur, and Al2O3 inclusions in the molten steel, generating fine and dispersed Ce2O2S and CeAlO3 rare earth inclusions.

[0050] Step 3: Mg treatment (added later) After Ce treatment is completed and fully reacted, metallic Mg is added to the molten steel at a rate of 0.014 wt.% (140 ppm) based on the mass of the molten steel. Immediately after addition, strong stirring (electromagnetic stirring, 200 kW) is started. Utilizing the low boiling point of Mg (1090 ℃), it rapidly vaporizes at the molten steel temperature (1580 ℃), generating a large number of fine magnesium vapor bubbles. The stirring time is controlled at 10 minutes to ensure the magnesium vapor bubbles fully float and perform the following functions: (a) Bubble flotation: adsorbing the already formed fine rare earth inclusions and carrying them rapidly to the slag layer for removal, preventing the rare earth inclusions from agglomerating and growing; (b) Stirring purification: enhancing the flow of the molten steel and promoting the transformation of residual Al2O3 and spinel into MgO inclusions; (c) Carbide inhibition: Mg accumulates at the solid-liquid interface, increasing compositional supercooling, adsorbing on the growth steps of liquid-precipitated carbides, hindering carbon atom diffusion, and promoting carbide dispersion and refinement.

[0051] Step 4: Vacuum degassing and solidification control After composite treatment, VD / RH vacuum degassing was performed (vacuum degree 67 Pa, treatment time 20 minutes), followed by ingot casting. During solidification, the cooling rate was controlled (15℃ / min) to allow the liquid carbides to precipitate under dispersed nucleation conditions, ultimately obtaining a GCr15 bearing steel billet with a maximum liquid carbide size of 22.19 μm and an average inclusion size of 2.01 μm. The standard mechanical properties of GCr15 bearing steel are mainly based on the national standard GB / T 18254-2016 "High Carbon Chromium Bearing Steel". Mechanical property tests showed an average hardness of 353.94 HV and an average tensile strength of 1080.66 MPa.

[0052] Example 2 A method for synergistically refining liquid carbides and inclusions in GCr15 bearing steel, comprising the following steps: Step 1: Steel melting and initial deoxidation After the GCr15 bearing steel raw material (pig iron) is initially refined in an electric arc furnace, it is transferred to an LF refining furnace. The dissolved oxygen in the molten steel is initially removed to a total oxygen content of ≤15 ppm using a conventional aluminum deoxidation process, and the Al content in the molten steel is controlled to be 0.001 wt.%.

[0053] Step 2: Ce processing (add first) At the end of LF refining, rare earth Ce is added to the molten steel in the form of pure Ce, at a rate of 0.05 wt.% (i.e., 500 ppm) based on the mass of the molten steel. After addition, the mixture is stirred for 10 minutes under inert gas (argon) protection to allow Ce to fully react with residual oxygen, sulfur, and Al2O3 inclusions in the molten steel, generating fine and dispersed Ce2O2S and CeAlO3 rare earth inclusions.

[0054] Step 3: Mg treatment (added later) After Ce treatment is complete and the reaction is full, metallic Mg is added to the molten steel at a rate of 0.015 wt.% (150 ppm) based on the mass of the molten steel. Immediately after addition, strong stirring is started (bottom-blown argon gas at a flow rate of 0.4 Nm³). 3 / h·t steel), utilizing the low boiling point of Mg (1090 ℃), it rapidly vaporizes at the temperature of molten steel (1580 ℃), generating a large number of fine magnesium vapor bubbles. The stirring time is controlled at 15 minutes to allow the magnesium vapor bubbles to float fully and perform the following functions: (a) Bubble flotation: adsorbing the already generated fine rare earth inclusions, carrying them to the slag layer for removal, and preventing the rare earth inclusions from agglomerating and growing; (b) Stirring purification: enhancing the flow of molten steel and promoting the transformation of residual Al2O3 and spinel into MgO inclusions; (c) Carbide inhibition: Mg is enriched at the solid-liquid interface, increasing compositional supercooling, adsorbing on the growth steps of liquid-precipitated carbides, hindering the diffusion of carbon atoms, and promoting the dispersion and refinement of carbides.

[0055] Step 4: Vacuum degassing and solidification control After composite treatment, the steel billet underwent VD / RH vacuum degassing (vacuum degree 67 Pa, treatment time 15 minutes), followed by ingot casting. During solidification, the cooling rate was controlled (20℃ / min) to allow the liquid carbides to precipitate under dispersed nucleation conditions, ultimately yielding a GCr15 bearing steel billet with a maximum liquid carbide size of 23.20 μm and an average inclusion size of 2.55 μm. Mechanical property testing showed an average hardness of 346.95 HV and an average tensile strength of 1076.63 MPa.

[0056] Example 3 A method for synergistically refining liquid carbides and inclusions in GCr15 bearing steel, comprising the following steps: Step 1: Steel melting and initial deoxidation After the GCr15 bearing steel raw material (pig iron) is initially refined in an electric arc furnace, it is transferred to an LF refining furnace. The dissolved oxygen in the molten steel is initially removed to a total oxygen content of ≤15 ppm using a conventional aluminum deoxidation process, and the Al content in the molten steel is controlled to be 0.005 wt.%.

[0057] Step 2: Ce processing (add first) At the end of LF refining, rare earth Ce is added to the molten steel in the form of pure Ce, at a rate of 0.01 wt.% (i.e., 100 ppm) based on the mass of the molten steel. After addition, the mixture is stirred under vacuum for 15 minutes to allow Ce to fully react with residual oxygen, sulfur, and Al2O3 inclusions in the molten steel, generating fine and dispersed Ce2O2S and CeAlO3 rare earth inclusions.

[0058] Step 3: Mg treatment (added later) After Ce treatment is complete and the reaction is full, metallic Mg is added to the molten steel at a rate of 0.02 wt.% (200 ppm) based on the mass of the molten steel. Immediately after addition, strong stirring is started (bottom-blown argon gas at a flow rate of 0.3 Nm³). 3 / h·t steel), utilizing the low boiling point of Mg (1090 ℃), it rapidly vaporizes at the temperature of molten steel (1580 ℃), generating a large number of fine magnesium vapor bubbles. The stirring time is controlled at 15 minutes to allow the magnesium vapor bubbles to float fully and perform the following functions: (a) Bubble flotation: adsorbing the already generated fine rare earth inclusions, carrying them to the slag layer for removal, and preventing the rare earth inclusions from agglomerating and growing; (b) Stirring purification: enhancing the flow of molten steel and promoting the transformation of residual Al2O3 and spinel into MgO inclusions; (c) Carbide inhibition: Mg is enriched at the solid-liquid interface, increasing compositional supercooling, adsorbing on the growth steps of liquid-precipitated carbides, hindering the diffusion of carbon atoms, and promoting the dispersion and refinement of carbides.

[0059] Step 4: Vacuum degassing and solidification control After composite treatment, the steel billet underwent VD / RH vacuum degassing (vacuum degree 67 Pa, treatment time 25 minutes), followed by ingot casting. During solidification, the cooling rate was controlled (5℃ / min) to allow the liquid carbides to precipitate under dispersed nucleation conditions, ultimately yielding a GCr15 bearing steel billet with a maximum liquid carbide size of 28.24 μm and an average inclusion size of 2.83 μm. Mechanical property testing showed an average hardness of 340.64 HV and an average tensile strength of 1069.88 MPa.

[0060] Example 4 A method for synergistically refining liquid carbides and inclusions in GCr15 bearing steel, comprising the following steps: Step 1: Steel melting and initial deoxidation After the GCr15 bearing steel raw material (pig iron) is initially refined in a converter, it is transferred to an LF refining furnace. The dissolved oxygen in the molten steel is initially removed to a total oxygen content of ≤15 ppm using a conventional aluminum deoxidation process, and the Al content in the molten steel is controlled to be 0.003 wt.%.

[0061] Step 2: Ce processing (add first) At the end of LF refining, rare earth Ce is added to the molten steel in the form of pure Ce, at a rate of 0.05 wt.% (i.e., 500 ppm) based on the mass of the molten steel. After addition, the mixture is stirred under vacuum for 5 minutes to allow Ce to fully react with residual oxygen, sulfur, and Al2O3 inclusions in the molten steel, generating fine and dispersed Ce2O2S and CeAlO3 rare earth inclusions.

[0062] Step 3: Mg treatment (added later) After Ce treatment is completed and fully reacted, metallic Mg is added to the molten steel at a rate of 0.01 wt.% (100 ppm) based on the mass of the molten steel. Immediately after addition, strong stirring (electromagnetic stirring, 210 kW) is started. Utilizing the low boiling point of Mg (1090 ℃), it rapidly vaporizes at the molten steel temperature (1580 ℃), generating a large number of fine magnesium vapor bubbles. The stirring time is controlled at 10 minutes to ensure the magnesium vapor bubbles fully float and perform the following functions: (a) Bubble flotation: adsorbing the already formed fine rare earth inclusions and carrying them rapidly to the slag layer for removal, preventing the rare earth inclusions from agglomerating and growing; (b) Stirring purification: enhancing the flow of molten steel and promoting the transformation of residual Al2O3 and spinel into MgO inclusions; (c) Carbide inhibition: Mg accumulates at the solid-liquid interface, increasing compositional supercooling, adsorbing on the growth steps of liquid-precipitated carbides, hindering carbon atom diffusion, and promoting carbide dispersion and refinement.

[0063] Step 4: Vacuum degassing and solidification control After composite treatment, the steel billet underwent VD / RH vacuum degassing (vacuum degree 67 Pa, treatment time 15 minutes), followed by ingot casting. During solidification, the cooling rate was controlled (15 ℃ / min) to allow the liquid carbides to precipitate under dispersed nucleation conditions, ultimately yielding a GCr15 bearing steel billet with a maximum liquid carbide size of 23.93 μm and an average inclusion size of 2.64 μm. Mechanical property testing showed an average hardness of 344.11 HV and an average tensile strength of 1068.36 MPa.

[0064] Comparative Example 1 (Mg only added) Step 1: Steel melting and initial deoxidation After the GCr15 bearing steel raw material (pig iron) is initially refined in an electric arc furnace, it is transferred to an LF refining furnace. The dissolved oxygen in the molten steel is initially removed to a total oxygen content of ≤15 ppm using a conventional aluminum deoxidation process, and the Al content in the molten steel is controlled to be 0.002 wt.%.

[0065] Step 2: Mg treatment At the end of LF refining, metallic Mg is added to the molten steel at a rate of 0.059 wt.% (590 ppm) based on the steel mass. Immediately after addition, strong stirring (electromagnetic stirring, 200 kW) is initiated. Utilizing Mg's low boiling point (1090 ℃), it rapidly vaporizes at the molten steel temperature (1580 ℃), generating a large number of fine magnesium vapor bubbles. The stirring time is controlled at 10 minutes. During their ascent, these magnesium bubbles adsorb and adhere to non-metallic inclusions such as Al2O3 in the molten steel, carrying them to the slag layer for removal. Simultaneously, the strong stirring promotes the flow and mass transfer of the molten steel, accelerating the reaction of Mg with Al2O3 and spinel, transforming them into fine MgO inclusions and improving their morphology. Furthermore, Mg accumulates at the solidification interface, inhibiting the diffusion of S and C elements in the steel, thereby hindering the growth of MnS inclusions and carbides, refining inclusions and carbides, and improving the toughness of the steel.

[0066] Step 3: Vacuum degassing and solidification control After treatment, the material underwent VD / RH vacuum degassing (vacuum degree 67 Pa, treatment time 20 minutes), followed by ingot casting. During solidification, the cooling rate was controlled (15 ℃ / min) to allow the liquid carbides to precipitate under dispersed nucleation conditions, ultimately yielding a GCr15 bearing steel billet with a maximum liquid carbide size of 36.88 μm and an average inclusion size of 3.52 μm. Mechanical property testing showed an average hardness of 333.66 HV and an average tensile strength of 1037.00 MPa.

[0067] Comparative Example 2 (Ce only) Step 1: Steel melting and initial deoxidation After the GCr15 bearing steel raw material (pig iron) is initially refined in an electric arc furnace, it is transferred to an LF refining furnace. The dissolved oxygen in the molten steel is initially removed to a total oxygen content of ≤15 ppm using a conventional aluminum deoxidation process, and the Al content in the molten steel is controlled to be 0.002 wt.%.

[0068] Step 2: Ce processing At the end of LF refining, rare earth Ce is added to the molten steel in the form of pure Ce, at a rate of 0.059 wt.% (i.e., 590 ppm) based on the mass of the molten steel. After addition, the mixture is stirred under vacuum for 10 minutes to allow Ce to fully react with residual oxygen, sulfur, and Al2O3 inclusions in the molten steel, generating fine and dispersed Ce2O2S and CeAlO3 rare earth inclusions.

[0069] Step 3: Vacuum degassing and solidification control After treatment, the material underwent VD / RH vacuum degassing (vacuum degree 67 Pa, treatment time 20 minutes), followed by ingot casting. During solidification, the cooling rate was controlled (15 ℃ / min) to allow the liquid carbides to precipitate under dispersed nucleation conditions, ultimately yielding a GCr15 bearing steel billet with a maximum liquid carbide size of 34.39 μm and an average inclusion size of 3.19 μm. Mechanical property testing showed an average hardness of 338.86 HV and an average tensile strength of 1043.73 MPa.

[0070] Comparative Example 3 (with added Mg-Ce complex) Step 1: Steel melting and initial deoxidation After the GCr15 bearing steel raw material (pig iron) is initially refined in an electric arc furnace, it is transferred to an LF refining furnace. The dissolved oxygen in the molten steel is initially removed to a total oxygen content of ≤15 ppm using a conventional aluminum deoxidation process, and the Al content in the molten steel is controlled to be 0.002 wt.%.

[0071] Step 2: Mg-Ce composite treatment At the end of LF refining, a Mg-Ce complex (Mg 25% by mass, Ce 75% by mass) is added to the molten steel at a rate of 0.059 wt.% (590 ppm) based on the mass of the molten steel. After addition, the mixture is stirred under vacuum for 10 minutes to allow the Mg-Ce complex to fully react with residual oxygen, sulfur, and Al2O3 inclusions in the molten steel, generating fine, dispersed MgO inclusions, Ce2O2S, and CeAlO3 rare earth inclusions.

[0072] Step 3: Vacuum degassing and solidification control After composite treatment, the steel billet underwent VD / RH vacuum degassing (vacuum degree 67 Pa, treatment time 20 minutes), followed by ingot casting. During solidification, the cooling rate was controlled (15 ℃ / min) to allow the liquid carbides to precipitate under dispersed nucleation conditions, ultimately yielding a GCr15 bearing steel billet with a maximum liquid carbide size of 30.66 μm and an average inclusion size of 2.73 μm. Mechanical property testing showed an average hardness of 340.67 HV and an average tensile strength of 1047.16 MPa.

[0073] Comparative Example 4 (Mg added first, then Ce added) Step 1: Steel melting and initial deoxidation After the GCr15 bearing steel raw material (pig iron) is initially refined in an electric arc furnace, it is transferred to an LF refining furnace. The dissolved oxygen in the molten steel is initially removed to a total oxygen content of ≤15 ppm using a conventional aluminum deoxidation process, and the Al content in the molten steel is controlled to be 0.002 wt.%.

[0074] Step 2: Mg treatment (add first) At the end of LF refining, metallic Mg is added to the molten steel at a rate of 0.014 wt.% (140 ppm) based on the mass of the molten steel. Immediately after addition, strong stirring (electromagnetic stirring, 200 kW) is initiated. Utilizing Mg's low boiling point (1090 ℃), it rapidly vaporizes at the molten steel temperature (1580 ℃), generating a large number of fine magnesium vapor bubbles. The stirring time is controlled at 10 minutes to allow the magnesium vapor bubbles to rise fully and preferentially react with the existing Al2O3 and spinel inclusions in the molten steel, converting them into MgO inclusions. Simultaneously, the strong stirring promotes the flow and mass transfer of the molten steel, enriching Mg at the solid-liquid interface, increasing compositional supercooling, and adsorbing it onto the growth steps of liquid-precipitated carbides, hindering carbon atom diffusion and promoting carbide dispersion and refinement.

[0075] Step 3: Ce processing (added later) After the Mg treatment is complete and the reaction is sufficient, rare earth Ce is added to the molten steel in the form of pure Ce at a rate of 0.045 wt.% (450 ppm) based on the mass of the molten steel. The mixture is then stirred under vacuum for 10 minutes to allow Ce to fully react with residual oxygen, sulfur, and inclusions such as MgO generated during the Mg treatment. Due to Ce's higher chemical reactivity, it will further modify these magnesium-containing inclusions, ultimately transforming them into fine, dispersed cerium rare earth inclusions such as CeAlO3 and Ce2O2S.

[0076] Step 4: Vacuum degassing and solidification control After composite treatment, the steel billet underwent VD / RH vacuum degassing (vacuum degree 67 Pa, treatment time 20 minutes) followed by ingot casting. During solidification, the cooling rate was controlled (15 ℃ / min) to allow the liquid carbides to precipitate under dispersed nucleation conditions, ultimately yielding a GCr15 bearing steel billet with a maximum liquid carbide size of 35.86 μm and an inclusion size of 3.48 μm. Mechanical property testing showed an average hardness of 337.06 HV and an average tensile strength of 1039.30 MPa.

[0077] Comparative Example 5 (below the lower limit) Same as Example 1, except that the amount of Ce added is 0.008 wt.% and the amount of Mg added is 0.008 wt.%.

[0078] The largest size of the liquid carbide in the final GCr15 bearing steel billet obtained in this comparative example was 37.69 μm, and the size of the inclusions was 3.74 μm.

[0079] Comparative Example 6 (above the upper limit) Same as Example 1, except that the amount of Ce added is 0.06 wt.% and the amount of Mg added is 0.03 wt.%.

[0080] The largest size of the liquid carbide in the final GCr15 bearing steel billet obtained in this comparative example is 33.51 μm, and the size of the inclusions is 3.28 μm.

[0081] Figure 1 The images show the morphology of liquid carbides in the experimental steels. (a) is the blank experimental steel (i.e., GCr15 bearing steel without any treatment), (b) is Example 1, and (c) is Example 2. Figure 2 The area ratio and maximum size of the liquid-precipitated carbides in the experimental steels are shown. 1# is the blank experimental steel, 2# is Example 1, and 3# is Example 2; [The remaining text appears to be a fragmented and incomplete description of the steel, possibly related to a test or experiment.] Figure 1 and Figure 2 It is known that in the GCr15 bearing steel billet treated by this invention, the liquid-precipitated carbides change from lamellar or blocky (40~80 μm) to dispersed granular or short rod-shaped (20~30 μm). The maximum size of the carbides is reduced by more than 40~50%, the area ratio is reduced by more than 30~40%, and they no longer form a continuous network or chain distribution. This invention inhibits the coarsening of liquid-precipitated carbides at the solidification source.

[0082] Figure 3 The figures represent the average size and number density of inclusions in the experimental steel. 1# represents the blank experimental steel, 2# represents Example 1, and 3# represents Example 2. It can be seen that after adding Ce first and then Mg, the average size of the inclusions decreased by more than 60%, the number density increased, and they exhibited a dispersed distribution.

[0083] Figure 4 The microstructure of liquid carbides and inclusions in the experimental steel is shown in (1) blank experimental steel, (2) Example 1, and (3) Example 2. It can be seen that the liquid carbides in the blank experimental steel will precipitate by attaching to large inclusions such as MnS, which often leads to an increase in the size of the liquid carbides. After Ce followed by Mg treatment, the liquid carbides changed from precipitating by attaching to large MnS to precipitating by attaching to small double-layer composite inclusions (the inner and outer layers are Ce-OS rare earth compounds or Mg-containing inclusions). The white part is Ce-OS rare earth compound, and the black part is MnS-MgO or MgO-Al2O3 composite inclusion. The liquid carbides precipitate by attaching to this double-layer composite inclusion, and the size decreases while the morphology is approximately spherical.

[0084] Figure 5 The hardness and tensile strength of the experimental steels are shown in Figure 1. 1# is the blank experimental steel, 2# is Example 1, and 3# is Example 2. It can be seen that after Ce treatment followed by Mg treatment, the hardness and tensile strength of Example 1 are increased by 8.87% and 6.12% respectively compared to the blank experimental steel.

[0085] Figure 6The microstructures of liquid carbides and inclusions in the experimental steels of Comparative Examples 1 to 4 are shown. (1) is Comparative Example 1, (2) is Comparative Example 2, (3) is Comparative Example 3, and (4) is Comparative Example 4. It can be seen that in Comparative Example 1, which only adds Mg, most of the liquid carbides appear in the form of layered blocks and are generally large in size. The liquid carbides precipitate with MgO inclusions, and their size is refined. In Comparative Example 2, which only adds Ce, Ce reacts with O and S elements in the molten steel to form Ce-OS inclusions, which are smaller in size than MgO. The size of the liquid carbides precipitated with Ce is further reduced, and their shape is more regular. In Comparative Example 3, where the Mg-Ce complex was added, fine MgO-Al2O3 and Ce-OS inclusions were formed. While the precipitated carbides adhered to these inclusions, the segregation of Mg and Ce also hindered the segregation of carbon atoms, thus impeding the growth of the precipitated carbides and achieving a refining effect. Similarly, in Comparative Example 4, where Mg was added first and then Ce, the yield was lower due to the earlier addition of Mg, resulting in a lower number of Mg-containing inclusions. At the same time, the amount of Mg segregation was also reduced, causing the refining effect to be mainly concentrated on Ce elements. The precipitated carbides adhered to the MgO and Ce-OS inclusions, resulting in a poor size refining effect.

[0086] As can be seen from Comparative Example 4 and the examples, Ce must be added first, followed by Mg. This order ensures that Ce preferentially reacts with O, S, and Al2O3 to form fine rare earth inclusions. The subsequent addition of Mg generates bubble flotation and stirring effects, promoting the removal of inclusions by flotation. At the same time, Mg enriches at the solid-liquid interface, inhibiting carbide coarsening. If the order is reversed (Mg first, then Ce), Mg will be prematurely vaporized and lost, failing to exert its synergistic effect, and neither inclusions nor carbides will be refined.

[0087] Furthermore, the method of the present invention is not only applicable to GCr15, but can also be extended to a series of high carbon chromium bearing steels such as GCr15SiMn and GCr18Mo. Any technical solution that uses Ce followed by Mg composite treatment to achieve synergistic refinement falls within the protection scope of the present invention.

[0088] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for synergistically refining liquated carbides and inclusions in GCr15 bearing steel, characterized in that, Includes the following steps: Step 1: After primary refining of GCr15 bearing steel raw material in an electric arc furnace or converter, transfer it to an LF refining furnace. Use conventional aluminum deoxidation process to initially remove dissolved oxygen from the molten steel to a total oxygen content ≤15 ppm, and control the Al content in the molten steel to 0.001~0.005 wt.%; Step 2: At the end of LF refining or the beginning of VD / RH vacuum treatment, add rare earth Ce to the molten steel. The amount added is 0.01~0.05 wt.% based on the mass of the molten steel. After adding, stir evenly under vacuum or inert gas protection. Step 3: Add metallic Mg to the molten steel obtained in Step 2. The amount added is 0.01~0.02 wt.% based on the mass of the molten steel; immediately start strong stirring after adding. Step 4: After step 3, VD / RH vacuum degassing is performed, followed by continuous casting or ingot casting; during solidification, the cooling rate is controlled at 5~20℃ / min to allow the liquid carbides to precipitate under dispersed nucleation conditions, and finally obtains GCr15 bearing steel billets with liquid carbide size ≤25μm and inclusion size ≤3μm.

2. The method for synergistically refining carbides and inclusions in GCr15 bearing steel according to claim 1, characterized in that, In step 2, the rare earth Ce is added in the form of pure Ce or Ce-Fe alloy.

3. The method for synergistically refining liquid carbides and inclusions in GCr15 bearing steel according to claim 2, characterized in that, The mass fraction of Ce in the Ce-Fe alloy is 10~30%.

4. The method for synergistically refining liquid carbides and inclusions in GCr15 bearing steel according to claim 1, characterized in that, In step 2, after adding the rare earth Ce to the molten steel, the stirring time is 5 to 10 minutes.

5. The method for synergistically refining liquid carbides and inclusions in GCr15 bearing steel according to claim 1, characterized in that, In step 3, the strong stirring is performed by bottom blowing argon gas or electromagnetic stirring, and the stirring time is controlled between 5 and 15 minutes.

6. The method for synergistically refining liquid carbides and inclusions in GCr15 bearing steel according to claim 3, characterized in that, Bottom argon blowing flow ≥ 0.3 Nm 3 / h·t steel; electromagnetic stirring power ≥ 200 kW.

7. The method for synergistically refining liquid carbides and inclusions in GCr15 bearing steel according to claim 1, characterized in that, In step 4, the vacuum degassing is performed with a vacuum level of ≤67 Pa and a processing time of 15~25 minutes.

8. The application of GCr15 bearing steel obtained by the method according to any one of claims 1 to 7 in high-speed rail bearings, wind turbine main shaft bearings and aerospace bearings.

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