Carbon-reduced microalloyed bearing steel and preparation method thereof

Abstract

The embodiment of the invention discloses carbon-reduced microalloyed bearing steel and a preparation method thereof, relates to the technical field of metal materials, and can improve the obdurability of the bearing steel. The bearing steel is prepared from, by mass, 0.60%-0.90% of C, 0.15%-0.75% of Si, 0.25%-1.25% of Mn, 1.20%-2.40% of Cr, smaller than or equal to 0.025% of P, smaller than or equal to 0.020% of S, 0.20%-0.40% of V, 0.01%-0.03% of Nb, smaller than or equal to 0.0030% of Ti and the balance Fe and inevitable impurities. The embodiment of the invention is suitable for replacing the production and manufacturing of high-carbon chromium bearing steel.

Description

Technical Field

[0001] This invention relates to the field of metallic materials technology, and in particular to a carbon-reduced microalloyed bearing steel and its preparation method. Background Technology

[0002] The quality of bearing steel is a crucial foundation and guarantee for determining bearing performance, precision, lifespan, and reliability. For over a century, high-carbon chromium bearing steel has consistently been one of the most widely used and applicable key materials for bearings, with a focus on ultra-fine grains and carbides in its microstructure. High-carbon chromium bearing steel, taking GCr15 as an example, has a chromium content of 1.30%-1.65% (according to GB / T18254-2016) and a carbon content of 0.95%-1.05%.

[0003] As a typical hypereutectoid steel, high-carbon chromium bearing steel has grain boundary carbides in its quenched microstructure. On the one hand, this deteriorates the toughness; for example, GCr15 has an impact toughness of less than 10J under conventional quenching and tempering. On the other hand, the coarse grain boundary carbide particles severely restrict the refinement of intragranular carbides and reduce their uniformity.

[0004] Therefore, completely eliminating the adverse effects of grain boundary carbides is a core challenge in microstructure control. Traditional methods for controlling microstructure by suppressing network carbides through controlled rolling and cooling, combined with heat treatment techniques such as cyclic quenching, have shortcomings. For example, uneven cooling of large-diameter rolled materials, easy regeneration of network carbides during secondary heat processing, large deformation during heat treatment due to cyclic quenching, difficulty in achieving large deformation with cold deformation, and complex and inefficient isothermal quenching processes.

[0005] In summary, traditional control methods have not fundamentally solved the problem of the large number and size of grain boundary carbides. Therefore, breaking through common key technologies for improving material properties is one of the important goals of basic research in my country's bearing industry. Summary of the Invention

[0006] In view of this, embodiments of the present invention provide a carbon-reduced microalloyed bearing steel and its preparation method, which can improve the strength and toughness of the bearing steel.

[0007] In a first aspect, embodiments of the present invention provide a carbon-reduced microalloyed bearing steel, wherein the composition and mass percentage of the bearing steel are as follows: C 0.60%–0.90%, Si 0.15%–0.75%, Mn 0.25%–1.25%, Cr 1.20%–2.40%, P≤0.025%, S≤0.020%, V 0.20%–0.40%, Nb 0.01%–0.03%, Ti≤0.0030%, with the balance being Fe and unavoidable impurities; wherein the mass ratio of Cr to Mn in the composition satisfies the condition: 1≤Cr / Mn≤5.

[0008] Optionally, in the composition, the mass ratio of Nb to Ti satisfies the condition: 3.5 ≤ Nb / Ti ≤ 10.

[0009] Optionally, the mass ratio of Nb, V and C in the composition is 1:7.5:37.5.

[0010] Optionally, in the composition, the mass percentage of C is 0.70% to 0.80%, the mass percentage of Si is 0.20% to 0.40%, the mass percentage of Mn is 0.25% to 0.50%, the mass percentage of Cr is 1.50% to 2.00%, the mass percentage of P is less than 0.010%, the mass percentage of S is less than 0.010%, the mass percentage of V is 0.20% to 0.30%, the mass percentage of Nb is 0.01% to 0.02%, and the mass percentage of Ti is ≤0.0030%.

[0011] Secondly, this invention provides a method for preparing carbon-reduced microalloyed bearing steel, comprising the following steps: The components of the mass percentage described in the first aspect are melted, cast into steel billets, and then hot-rolled. The hot rolling and subsequent heat treatment process includes, in sequence: heating in a heating furnace, controlled rolling and cooling, spheroidizing annealing, and quenching and tempering; wherein, heating in the heating furnace includes: heating the hot-rolled steel billet in the heating furnace for a preset time, with the soaking zone controlled at 1200-1220℃.

[0012] Optionally, the controlled rolling and cooling includes: after the heated steel billet is descaled by high-pressure water, it is rolled into a rolling mill. The initial rolling temperature is controlled at 1100-1150℃, the final rolling temperature is controlled at 850-920℃, and rapid water cooling is selected after rolling to obtain the desired rolled product. In this case, the residual austenite in the rolled microstructure is uniformly distributed, and the precipitation of secondary cementite and the transformation of pearlite are effectively controlled.

[0013] Optionally, the spheroidizing annealing includes: heating the rolled product to 740-810°C and holding it at that temperature for a preset time, then slowly cooling it to room temperature to form a uniform and fine spheroidized annealed structure.

[0014] Optionally, the tempering includes: quenching the spheroidized annealed material obtained in the previous step, heating the quenching temperature to 820-860°C and holding it for a preset time; tempering the material at 150-170°C for a preset time and then cooling it to room temperature; after quenching and tempering, a tempered structure of martensite and undissolved carbides is formed.

[0015] The carbon-reduced microalloyed bearing steel and its preparation method described in this invention reduce the carbon content and add vanadium-niobium microalloying elements to regulate the carbides in the steel, thereby achieving the control of the refinement and homogenization of the carbides in the bearing steel, which can improve the strength and toughness of the bearing steel. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 The microstructure of the uncarbonized, vanadium- and niobium-free high-carbon chromium bearing steel in the spheroidized annealed state is shown in Comparative Example 2. Figure 2 The microstructure of the carbon-reduced vanadium-niobium bearing steel in the spheroidized annealed state in Example 3; Figure 3 The microstructure of the uncarbonized, niobium-containing, vanadium-free high-carbon chromium bearing steel in the spheroidized annealed state was used as a comparative example. Figure 4 The microstructure of the uncarbonized, vanadium- and niobium-free high-carbon chromium bearing steel in the tempered state was used as a comparative example. Figure 5 The microstructure of the decarbonized vanadium-niobium bearing steel in Example 3 is shown in the tempered state. Figure 6 The microstructure of the uncarbonized, niobium-containing, vanadium-free high-carbon chromium bearing steel in the tempered state is shown in Comparative Example 4. Detailed Implementation

[0018] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] In a first aspect, embodiments of the present invention provide a carbon-reduced microalloyed bearing steel. By reducing the carbon content and adding vanadium-niobium microalloying elements to regulate the carbides in the steel, the carbon content of the bearing steel is refined and homogenized, thereby improving the strength and toughness of the bearing steel.

[0020] This invention provides a carbon-reduced microalloyed bearing steel, the composition and mass percentage of which are: C 0.60%~0.90%, Si 0.15%~0.75%, Mn 0.25%~1.25%, Cr 1.20%~2.40%, P ≤0.025%, S ≤0.020%, V 0.20%~0.40%, Nb 0.01%~0.03%, Ti ≤0.0030%, with the balance being Fe and unavoidable impurities.

[0021] Carbon (C) is one of the key elements for ensuring the hardness and wear resistance after quenching and tempering. However, sufficient hardness cannot be obtained when C is below 0.55%. On the other hand, when C is above 1.00%, the hardness of the steel increases, while its machinability and forgeability decrease. Therefore, C is set at 0.60%–0.90%, with 0.70%–0.80% being preferred.

[0022] Si is an important deoxidizing element in steel, significantly improving its hardenability and strength. When Si dissolves in cementite, it increases the hardness of the cementite, thereby enhancing the wear resistance of the steel. However, excessive Si content in steel leads to increased material hardness, reducing its machinability and forging properties. Therefore, the Si content is typically set between 0.15% and 0.75%, with a preferred range of 0.20% to 0.40%.

[0023] Mn plays a positive role in the deoxidation of steel, while also imparting necessary hardenability and improving its strength. Mn can combine with sulfur in steel to form MnS and (Fe, Mn)S, which are less detrimental to steel properties, effectively reducing or inhibiting the formation of FeS, which is harmful to steel performance. In high-carbon chromium bearing steel, adding an appropriate amount of Mn helps improve the steel's performance and purity. However, if the Mn content is too high, it will lead to an increase in retained austenite, enhancing the steel's overheat sensitivity and cracking tendency, while also reducing dimensional stability. The recommended Mn content is 0.25%–1.25%, with 0.25%–0.50% being preferred.

[0024] Cr is an element that can significantly improve the hardenability of steel. To ensure its full effect, the Cr content usually needs to be controlled above 1.20%. However, when the Cr content is too high, it will promote the precipitation of carbides at grain boundaries during the cooling process after quenching, which will adversely affect the toughness of the steel. To avoid this, the Cr content is set at 1.20% to 2.40%, with 1.50% to 2.00% being preferred.

[0025] P is one of the unavoidable impurity elements in steel, and it tends to segregate at grain boundaries, leading to a decrease in the toughness of the steel. Therefore, P content should be below 0.025%, and more preferably below 0.010%.

[0026] S readily combines with Mn to form MnS, which reduces the toughness of the steel. Therefore, the content of S should be below 0.020%, preferably below 0.010%.

[0027] V can form carbides and is an effective grain refiner. However, when the V content exceeds 0.50%, the grain refinement effect tends to saturate, which not only increases costs but also deteriorates processing performance due to the large amount of carbonitrides formed. Therefore, V is set at 0.20%–0.40%, with 0.20%–0.30% being preferred.

[0028] Nitrogen (Nb) is a strong carbide-forming element that can be added alone or in combination with other elements at different stages of the process, such as smelting, casting, hot rolling, and heat treatment, to generate single or composite strong carbides. This helps to refine, homogenize, and stabilize carbides in bearing steel, thereby enhancing the hardness and toughness of new bearing steels. In medium- and high-carbon steels, trace amounts of Nb, as an alloying element, can significantly refine grains, improve the fineness and uniformity of the microstructure, and thus improve the plasticity and toughness of the steel. Nb can dissolve in the higher temperature range of austenite and can also recrystallize at low temperatures, which allows it to effectively inhibit grain growth and improve steel properties through precipitation strengthening mechanisms. Therefore, the Nb content is set at 0.01%–0.03%, with a preferred range of 0.01%–0.02%.

[0029] Ti readily combines with nitrogen in high-carbon steel to form TiN inclusions, which are categorized into Class B, Class D, and Class DS non-metallic inclusions based on their morphology. These inclusions disrupt the continuity of the steel. Under external deformation, TiN inclusions easily become stress concentration sources. During hot deformation or heat treatment, cracks easily form at the interface due to the difference in thermal expansion coefficients between the metal matrix and the TiN inclusions. As a residual element, the content of Ti in high-carbon chromium bearing steel is strictly limited; therefore, the Ti content is limited to: Ti ≤ 0.0030%.

[0030] In the traditional microalloying process of low-carbon steel, the content of microalloying elements added is usually no more than 0.05%. Their main function is to suppress the original austenite grain size of low-carbon steel, thereby achieving the purpose of refining the microstructure and improving toughness.

[0031] Unlike traditional microalloying processes, the bearing steel in this embodiment of the invention is a medium-high carbon steel. By reducing the carbon content and using microalloying (i.e., adding vanadium-niobium microalloying elements) to enhance the stability of carbides in the bearing steel, the refinement and homogenization of the bearing steel carbides can be controlled, thereby improving the strength and toughness of the bearing steel.

[0032] In some embodiments, the mass ratio of Cr to Mn in the composition satisfies the condition: 1 ≤ Cr / Mn ≤ 5, to optimize the morphology and distribution of carbides, avoid residual austenite due to excessive manganese, and ensure hardenability and microstructure uniformity. In some examples, the mass ratio of Cr to Mn is 1; in others, it is 3; and in still others, it is 5.

[0033] In some embodiments, the mass ratio of Nb to Ti in the composition satisfies the condition 3.5 ≤ Nb / Ti ≤ 10, in order to optimize the morphology and distribution of carbides, avoid the formation of coarse inclusions, and synergistically enhance the grain refinement effect. In some examples, the mass ratio of Nb to Ti is 3.5; in other examples, the mass ratio of Nb to Ti is 6; and in still other examples, the mass ratio of Nb to Ti is 10.

[0034] In some embodiments, the composition comprises, by mass percentage, 0.70% to 0.80% of C, 0.20% to 0.40% of Si, 0.25% to 0.50% of Mn, 1.50% to 2.00% of Cr, less than 0.010% of P, less than 0.010% of S, 0.20% to 0.30% of V, 0.01% to 0.02% of Nb, and ≤0.0030% of Ti.

[0035] In some embodiments, the composition comprises 0.75% C by mass, 0.50-0.40% Si by mass, 0.8% Mn by mass, 1.80% Cr by mass, 0.013% P by mass, 0.0018% S by mass, 0.26% V by mass, 0.020% Nb by mass, and 0.0015% Ti by mass. Figure 5 The microstructure of the decarbonized vanadium-niobium bearing steel in this embodiment is shown in the tempered state.

[0036] In some embodiments, the mass ratio of Nb, V, and C in the composition is 1:7.5:37.5. When the mass ratio of Nb, V, and C satisfies 1:7.5:37.5, the bearing steel can have good strength and toughness while the average aspect ratio of carbides and the proportion of grain boundary carbides in the bearing steel microstructure can be controlled to a minimum.

[0037] Secondly, embodiments of the present invention provide a method for preparing carbon-reduced microalloyed bearing steel, according to which the bearing steel described in any of the foregoing embodiments can be obtained.

[0038] The method for preparing carbon-reduced microalloyed bearing steel provided in this invention may include the following steps: The components, which are described in the specified mass percentage, are melted, cast into steel billets, and then hot-rolled. The hot rolling and subsequent heat treatment process is as follows: heating in a heating furnace → controlled rolling and cooling → spheroidizing annealing → quenching and tempering.

[0039] The method for preparing carbon-reduced microalloyed bearing steel according to embodiments of the present invention enhances the stability of carbides in bearing steel by reducing carbon content and adding vanadium-niobium microalloying elements, thereby achieving the control of carbide refinement and homogenization in bearing steel, and thus improving the strength and toughness of bearing steel.

[0040] In some embodiments, the heating in the heating furnace includes heating the hot-rolled steel billet in the heating furnace for a preset time, wherein the soaking zone is controlled at 1200–1220°C. The heating time can be specifically determined based on the actual thickness of the hot-rolled steel billet.

[0041] In some embodiments, the controlled rolling and cooling includes: after the heated steel billet is descaled by high-pressure water, it is rolled into a rolling mill. The initial rolling temperature is controlled at 1100-1150℃, the final rolling temperature is controlled at 850-920℃, and after rolling, rapid water cooling is selected to obtain the desired rolled product. The cooling rate is ≥5℃ / s. The residual austenite in the rolled microstructure (i.e. the microstructure of the obtained rolled product) is uniformly distributed, and the precipitation of secondary cementite and the transformation of pearlite are effectively controlled.

[0042] In some embodiments, the spheroidizing annealing includes: heating the finished rolled product to 740–810°C, holding it at that temperature for a preset time, and then slowly cooling it to room temperature to form a uniform and fine spheroidized annealed structure. The holding time is specifically determined based on the actual thickness of the finished rolled product.

[0043] In some embodiments, the tempering includes: quenching the spheroidized annealed material obtained in the previous step by heating it to 820–860°C and holding it at that temperature for a preset time; tempering it at 150–170°C for a preset time and then cooling it to room temperature; after quenching and tempering, a tempered microstructure of martensite and undissolved carbides is formed. The holding time is specifically determined based on the actual thickness of the spheroidized annealed material; the thicker the material, the longer the holding time.

[0044] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0045] Comparative Example 1 is a bearing steel without vanadium and niobium and with reduced carbon content; Comparative Example 2 is a high-carbon chromium bearing steel without vanadium and niobium and without reduced carbon content; Comparative Examples 3-5 are high-carbon chromium bearing steels containing vanadium and niobium microalloying elements and without reduced carbon content; Examples 1-7 are bearing steels with different niobium microalloying element contents and under reduced carbon content. The alloy composition is shown in Table 1 (wherein, Nb is added in the form of niobium-iron alloy at the end of the metallurgical process).

[0046]

[0047] The shaded area is outside the scope of protection claimed by this invention.

[0048] The rolling and subsequent heat treatment process of the bearing steel described in the above embodiments and comparative examples is as follows: heating in a heating furnace → controlled rolling and cooling → spheroidizing annealing → quenching and tempering. The quenching heating temperature is 820-860℃, and the quenching heating time is 1.5 min / mm, where the dimensions are calculated according to the thinnest direction of the sample. The tempering temperature is 150-170℃, and the tempering time is determined according to the sample thickness.

[0049] Figure 2 The image shows the effect of V and Nb microalloying elements on the microstructure of spheroidized annealed bearing steel under carbon reduction conditions. V and Nb microalloying elements refine the granular pearlite. (Comparison) Figure 1 Microstructure of bearing steel containing V and Nb elements under non-carbon reduction conditions and Figure 3 In high-carbon chromium bearing steel containing Nb but no V without carbon reduction, the size uniformity of granular pearlite was found to be reduced, and rod-shaped pearlite was more abundant in the case of no carbon reduction than in the case of carbon reduction.

[0050] Example 3: Bearing steel with reduced carbon content and containing V and Nb; Comparative Example 4: High-carbon chromium bearing steel with unreduced carbon content and containing Nb but no V; Quenched and tempered microstructure as follows: Figures 5-6 As shown, the results reveal a significant refinement and increased roundness of the carbides. The aspect ratio is used to represent roundness; the closer the aspect ratio is to 1, the greater the roundness of the material. (Comparison) Figure 4 Microstructure of bearing steel without V and Nb elements under undecarburized conditions revealed that the area distribution of undissolved carbides was less uniform and the size was larger than that of bearing steel under decarburized conditions, and coarse carbide morphology still existed at grain boundaries.

[0051] Table 2 shows the aspect ratio of tempered undissolved carbides, the area ratio of grain boundary carbides, the hardness (HRC), tensile strength, and impact toughness of the embodiments and comparative examples in the embodiments of the present invention.

[0052]

[0053] Examples of steel No. 1 to 7 all exhibit a hardness of over 60 HRC and excellent toughness of over 5 J in room temperature impact test (U-type). This high toughness is due to the refinement of carbides by the V and Nb microalloying elements added in this invention, especially the purification effect on grain boundary carbides. This prevents the test steels from undergoing brittle fracture when impacted in a Charpy impact tester, instead causing fracture after a certain degree of ductile deformation. Comparative Example No. 1, without the addition of V and Nb microalloying elements while reducing the C content, has a chemical composition within the range of this invention, but its performance after heat treatment is lower than that of the example steels, with its impact toughness being lower in all cases.

[0054] The results of Comparative Examples No. 2 and 3 show that appropriately reducing the C element is effective in simultaneously improving hardness and toughness. Furthermore, the results of the comparative examples and embodiments demonstrate that V and Nb microalloying elements can simultaneously achieve both high hardness and toughness.

[0055] Comparative Example No. 3 shows that while a higher content of V microalloying element improves impact toughness, the aspect ratio of its carbides remains relatively high, and the improvement in static toughness of the steel is not significant. This indicates that the presence of rod-shaped carbides in the microstructure leads to a higher risk of stress concentration cracking, and the effect on carbide refinement is poor. Meanwhile, the higher content of Nb microalloying element in Comparative Example 4 reduces the impact toughness of the steel. This indicates that trace amounts of Nb can improve performance by controlling the carbides in the steel, but when the content exceeds a certain range, undissolved Nb exists as inclusions in the steel, resulting in excessive inclusion content and affecting the steel's performance.

[0056] The bearing steels provided in the embodiments of this invention have a two-phase microstructure consisting of quenched martensite and undissolved carbides. The coarse grain boundary carbides are significantly eliminated, while the undissolved carbides are uniformly distributed within the grains. Therefore, during deformation treatment, plate-shaped or columnar cementite is less prone to cracking due to stress concentration at its ends, and spherical cementite is uniformly dispersed, approaching an ideal state that minimizes stress concentration. This microstructure reduces the likelihood of cementite becoming a crack initiation site, significantly improving the strength and toughness of the steel, thus achieving optimized material properties.

[0057] The purifying effect of spherical carbides on the original austenite grain boundaries can effectively inhibit grain boundary embrittlement, thereby avoiding the reduction in material toughness caused by grain boundary embrittlement and improving the overall mechanical properties of the material. Therefore, although the embodiments of this invention are medium and high carbon steels, the harm caused by embrittlement due to undissolved carbides is low, the Charpy impact toughness is above 5J, the tensile strength exceeds 2200MPa, and the hardness exceeds 60HRC.

[0058] The core design principle of the bearing steel in this invention is to reduce carbon content and perform vanadium-niobium microalloying. This design effectively controls carbides, significantly enhancing the strength and toughness of the bearing steel. This achievement plays a crucial role in improving the performance of high-end bearings, significantly raising the application technology level of high-end bearings. It has extremely important scientific theoretical and practical value for solving the long-standing "bottleneck" problem of high-end bearings in the high-end equipment manufacturing industry and overcoming the shortcomings in common technologies of bearing steel. It is expected to promote the upgrading and development of bearing technology in the high-end equipment manufacturing industry.

[0059] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0060] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0061] The above description is merely a specific embodiment 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 technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A carbon-reduced microalloyed bearing steel, characterized in that, The composition and mass percentage of the bearing steel are as follows: C 0.60%~0.90%, Si 0.15%~0.75%, Mn 0.25%~1.25%, Cr 1.20%~2.40%, P ≤0.025%, S ≤0.020%, V 0.20%~0.40%, Nb 0.01%~0.03%, Ti ≤0.0030%, with the balance being Fe and unavoidable impurities; in the composition, the mass ratio of Cr to Mn satisfies the condition: 1≤Cr / Mn≤5.

2. The carbon-reduced microalloyed bearing steel according to claim 1, characterized in that, In the composition, the mass ratio of Nb to Ti satisfies the condition: 3.5 ≤ Nb / Ti ≤ 10.

3. The carbon-reduced microalloyed bearing steel according to claim 1, characterized in that, The mass ratio of Nb, V and C in the composition is 1:7.5:37.

5.

4. The carbon-reduced microalloyed bearing steel according to claim 1, characterized in that, In the composition, the mass percentage of C is 0.70%–0.80%, the mass percentage of Si is 0.20%–0.40%, the mass percentage of Mn is 0.25%–0.50%, the mass percentage of Cr is 1.50%–2.00%, the mass percentage of P is less than 0.010%, the mass percentage of S is less than 0.010%, the mass percentage of V is 0.20%–0.30%, the mass percentage of Nb is 0.01%–0.02%, and the mass percentage of Ti is ≤0.0030%.

5. A method for preparing the carbon-reduced microalloyed bearing steel according to any one of claims 1 to 4, characterized in that, Includes the following steps: The components, which are described in the specified mass percentage, are melted, cast into steel billets, and then hot-rolled. The hot rolling and subsequent heat treatment process includes, in sequence: heating in a heating furnace, controlled rolling and cooling, spheroidizing annealing, and quenching and tempering; wherein, heating in the heating furnace includes: heating the hot-rolled steel billet in the heating furnace for a preset time, with the soaking zone controlled at 1200-1220℃.

6. The method for preparing carbon-reduced microalloyed bearing steel according to claim 5, characterized in that, The controlled rolling and cooling process includes: after the heated steel billet is descaled by high-pressure water, it is rolled into a rolling mill. The initial rolling temperature is controlled at 1100-1150℃, and the final rolling temperature is controlled at 850-920℃. After rolling, rapid water cooling is selected to obtain the desired rolled product. The residual austenite in the rolled microstructure is uniformly distributed, and the precipitation of secondary cementite and the transformation of pearlite are effectively controlled.

7. The method for preparing carbon-reduced microalloyed bearing steel according to claim 5, characterized in that, The spheroidizing annealing includes: heating the rolled product to 740-810°C and holding it at that temperature for a preset time, then slowly cooling it to room temperature to form a uniform and fine spheroidized annealed structure.

8. The method for preparing carbon-reduced microalloyed bearing steel according to claim 6, characterized in that, The tempering process includes: quenching the spheroidized annealed material obtained in the previous step, heating the quenching temperature to 820-860°C and holding it for a preset time; tempering the material at 150-170°C for a preset time and then cooling it to room temperature; after quenching and tempering, a tempered structure of martensite and undissolved carbides is formed.

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