CN114318173B

CN114318173B - Bearing steel and production method thereof

Info

Publication number: CN114318173B
Application number: CN202111550280.XA
Authority: CN
Inventors: 姜婷; 汪开忠; 张晓瑞; 尹德福; 丁雷
Original assignee: Maanshan Iron and Steel Co Ltd
Current assignee: Maanshan Iron and Steel Co Ltd
Priority date: 2021-12-17
Filing date: 2021-12-17
Publication date: 2022-08-19
Anticipated expiration: 2041-12-17
Also published as: CN114318173A

Abstract

The invention discloses bearing steel and a production method thereof. The bearing steel has heat resistance and corrosion resistance, and comprises the following components in percentage by weight: 0.50 to 0.60% of carbon, 0.30 to 0.40% of silicon, 2.20 to 2.50% of chromium, 1.00 to 1.20% of nickel, 0.80 to 1.00% of cobalt, 1.10 to 1.30% of tungsten, 0.010 to 0.025% of lanthanum, 0.010 to 0.025% of yttrium, a trace of to 0.015% of sulfur, 0.005% or less of titanium, 0.0015% or less of oxygen, and the balance of Fe and other unavoidable impurities. The invention fully utilizes the inclusion modification effect and the corrosion resistance effect of La and Y, simultaneously ensures that the corrosion resistance coefficient I is more than or equal to 2.40, the corrosion resistance of the steel reaches more than 2.5 times of that of general bearing steel GCr15, and the yield strength R is 500 DEG C _p0.2 ≥1400MPa。

Description

Bearing steel and production method thereof

Technical Field

The invention belongs to the technical field of bearing steel, and particularly relates to bearing steel and a production method thereof.

Background

The bearing is an important basic element of mechanical equipment, and with the continuous progress and development of industrial technology, the quality requirement of bearing steel is higher and higher. Bearing steel is mainly used for manufacturing balls and rolling rings of bearings, and is required to have high hardness, strength and wear resistance. And the bearing steel has severe and complex working conditions and is recognized as one of the most representative steel types in the special steel industry. The bearing runs in a complex environment with high alternating stress, and the bearing steel is required to have high surface hardness, wear resistance and contact fatigue performance, and some bearing steel also has the performances of temperature resistance, corrosion resistance, impact resistance and the like in special environments.

In order to solve the problems, through search, the chinese patent CN113088799A discloses a low-cost, ultra-pure, high-toughness, low-carbon stainless bearing steel and a preparation method thereof: 0.13 to 0.30 percent of C; 0.05 to 0.2 percent of Si; 0.02 to 0.1 percent of Mn; 13.6 to 16.80 percent of Cr; 2.1 to 4.0 percent of Ni; 12.5 to 17 percent of Co; 5% -6% of Mo; w0.7% -2.5%; 0.7 to 1.2 percent of Nb and V; p + S + Ti is less than or equal to 0.025 percent, and Ti is less than or equal to 0.0012 percent; o is less than or equal to 0.0007 percent; n + H is less than or equal to 0.0015 percent, and N is less than or equal to 0.0014 percent; 0.05 to 0.08 percent of Al; 0.005% -0.015% of Ce; 0.005% -0.02% of La; 0.01 to 0.03 percent of Y and the other elements are Fe. The preparation process comprises the steps of primary smelting of molten steel, AOD refining, LF refining, IC casting, VIM smelting, ESR electroslag remelting and VAR vacuum consumable remelting. Compared with the prior art, the invention has the advantages of lower production cost, better obdurability of the low-carbon stainless bearing steel, longer fatigue life and extremely low content of oxygen and nitrogen impurities.

Disclosure of Invention

1. Problems to be solved

In order to solve the problems, the invention provides bearing steel which has higher heat resistance and corrosion resistance and meets the use requirements.

The invention also provides a production method of the bearing steel.

2. Technical scheme

In order to solve the problems, the technical scheme adopted by the invention is as follows:

the bearing steel of the invention has both heat resistance and corrosion resistance, and comprises the following components in percentage by weight: 0.50 to 0.60 percent of C, 0.30 to 0.40 percent of Si, 2.20 to 2.50 percent of Cr,1.00 to 1.20 percent of Ni, 0.80 to 1.00 percent of Co, 1.10 to 1.30 percent of W, 0.010 to 0.025 percent of La, 0.010 to 0.025 percent of Y, 0.015 to 0.015 percent of trace of P, 0.015 percent of trace of S, less than or equal to 0.005 percent of Ti, less than or equal to 0.0015 percent of O, and the balance of Fe and other inevitable impurities. In order to fully utilize the inclusion modification effect and the corrosion resistance effect of La and Y and avoid the risk of nodulation during casting, A is more than or equal to 0.21 and less than or equal to 0.34,

to achieve optimum corrosion resistance, it is necessary to ensure a corrosion resistance coefficient I of 2.40 or more, I1.46 Si +0.37 Cr +0.55 Ni +18.2 La + 19.0Y-0.11 Ni ² 。

(1) The content of C is controlled between 0.50wt percent and 0.60wt percent

C is the most basic effective element in steel for strong hardening and hardenability. The C element can expand and stabilize austenite, so that the high-temperature strength of the heat-resistant steel is improved; but as its content increases, ductility decreases and the risk of carbon segregation and net carbides increases.

(2) The Si content is controlled between 0.20 weight percent and 0.50 weight percent

Si is an effective strengthening element in steel, and silicon is mainly enriched on the surface of the steel, so that the stability of a rust layer is improved, and the corrosion resistance is improved. However, if the amount of the Si element is too large, the formability of the fastener is deteriorated, the room temperature plasticity and the thermoplasticity are deteriorated, and the increase of the Si element increases the diffusion of carbon in the steel, thereby increasing the decarburization of the steel.

(3) The Cr content is controlled to be 2.20 to 2.50 weight percent

The Cr element remarkably improves the obdurability, hardness and heat strength in steel, and is precipitated in the form of carbide. Cr can form a compact and complete oxide film between the rust layer on the steel surface and the steel matrix, can refine the crystal grains of alpha-FeO (OH) in the rust layer, and can effectively inhibit corrosive anions, particularly Cl ^- Invasion of ions. However, excessive Cr increases the temper brittleness of the steel.

(4) The Ni content is controlled to be 1.00 to 1.20 weight percent

Ni can generate an infinitely miscible solid solution with Fe, has the function of enlarging a phase region, and does not form carbide. The nickel can stabilize austenite and enhance the hardenability of the steel; ni is an effective element for reducing the ductile-brittle transition temperature, and the low-temperature toughness is obviously improved; the corrosion resistance of Ni is similar to that of Cr, and the addition of Cu and Ni can also accelerate the cathodic reduction of a rust layer and inhibit the anodic dissolution.

(5) The content of Co is controlled between 0.80wt percent and 1.00wt percent

Co is a non-carbide forming element and strengthens ferrite in the steel. Meanwhile, Co has oxidation resistance, and can remarkably improve the thermal stability and heat resistance of the steel. Excessive Co addition results in a decrease in material toughness and an increase in decarburization sensitivity of the steel.

(6) The W content is controlled to be 1.10wt percent to 1.30wt percent

W is resistant to high temperature, and forms carbide with carbon when dissolved in steel, and can improve the normal temperature strength and high temperature strength of the steel, but the excessive W can reduce the corrosion resistance and high temperature oxidation resistance of the steel.

(7) The La content is controlled to be 0.010 to 0.025 weight percent, and the Y content is controlled to be 0.010 to 0.025 weight percent

La and Y: adding appropriate amount of rare earth La and Y into steel, one of the functions is to wrap MnS and A1 ₂ O ₃ And the impurities are modified into rare earth impurities around the impurities, so that the impact property and the contact fatigue life of the bearing steel can be obviously improved. In addition, the La and Y large atoms are partially polymerized to the interface of the rust layer and the substrate, so that after the rust layer is formed on the surface of the steel, a protective atomic layer is formed on the substrate close to the rust layer, the rust layer is prevented from expanding to the inside of the substrate, and the corrosion rate is effectively reduced. Excessive amounts of Y and La may cause the formation of nodules during the casting of the molten steel. In order to fully utilize the inclusion modification effect and the corrosion resistance effect of La and Y and avoid the risk of nodulation during casting, A is more than or equal to 0.21 and less than or equal to 0.34, and the fluidity coefficient of molten steel is ensured

(8)P≤0.015wt％、S≤0.015wt％

S and P: the sulfur is easy to form MnS inclusion with manganese in the steel, and is harmful to the processing performance and the fatigue performance of the material; p is an element with a strong segregation tendency and usually also causes co-segregation of sulphur and manganese, which is detrimental to the homogeneity of the product structure and properties. Therefore, P is required to be controlled to be less than or equal to 0.015wt percent and S is required to be controlled to be less than or equal to 0.015wt percent.

(9)O≤0.0015wt％、Ti≤0.005％

O and Ti: o forms oxide inclusions in the steel, and the content of O is controlled to be less than or equal to 0.0015 wt%; with the great reduction of oxide inclusions in bearing steel, titanium inclusions gradually become main factors influencing the fatigue life of the bearing steel, so that Ti is required to be controlled to be less than or equal to 0.005 wt%.

In the invention, the corrosion resistance is not independent of the corrosion resistance of each element, and the compound action of each alloy element is utilized to achieve the optimal corrosion resistance, so that the corrosion resistance coefficient I is required to be ensured to be more than or equal to 2.40, and the I is 1.46 Si +0.37 Cr +0.55 Ni +18.2 La + 19.0Y-0.11 Ni ² 。

The production method of the bearing steel comprises the following steps: electric arc furnace or converter smelting → LF furnace refining → RH vacuum degassing → continuous casting of a 380mm to 700mm bloom → rolling of a 250 mm bloom → rolling of a phi 15 to 80mm bar. The method comprises the following specific steps:

s101, smelting in a converter arc furnace: bottom argon blowing is carried out before tapping, the argon blowing flow is adjusted on the basis that molten steel does not tumble a tapping ladle, the tapping is carried out when slag is generated, and the slag discharge amount is strictly controlled to be more than 90 mm;

s102, LF: deoxidizing and desulfurizing, and selecting proper proportion of CaO-SiO for white slag ₂ -MgO-based slag sample (CaO: 55-60%, SiO) ₂ 20-40 percent of MgO and less than or equal to 4 percent of MgO, and keeping the white slag for more than 20 min; while controlling (FeO) + (MnO) in the refining slag<l.0%, thereby effectively reducing the oxygen content in the steel;

s103, RH: RH continuously carries out circular degassing operation to remove gas and impurities in the molten steel, and pure degassing time is controlled to be more than or equal to 15min so as to ensure that O is less than or equal to 0.0015 percent and Ti is less than or equal to 0.005 percent after vacuum treatment;

s104, continuous casting: electromagnetic stirring is adopted, La lines and Y lines are added into a crystallizer, protective casting is adopted in the whole process, a crystallizer liquid level control system is adopted, the liquid level fluctuation is controlled to be less than or equal to +/-2.5 mm, and the superheat degree is controlled to be 30-40 ℃. Continuously casting a large square billet with the thickness of 380 mm-600 mm, and then slowly cooling in a pit for more than or equal to 36 h.

S105, rolling a bar with the diameter of 15-80 mm: the soaking temperature of the heating furnace is 1300-1400 ℃, so that the steel billet is fully austenitized and the crystal grains are not coarsened.

The maximum size of the inclusions of the bearing steel bar obtained by the steps is less than or equal to 10 mu m, and the shape of the inclusions is spherical. The following heat treatment process is adopted: spheroidizing annealing at 810 ℃ (oil cooling) → 190 ℃ (air cooling). The size of carbide in the structure after heat treatment is less than or equal to 0.8 mu m; tensile property: r _m ≥2300MPa，R _p0.2 ≥1600MPa，A ₅ Not less than 3.5 percent; the hardness HRC is more than or equal to 58; impact energy A at normal temperature _KU Not less than 13J, contact fatigue life L ₁₀ ≥5.0×10 ⁷ The Cl-corrosion resistance is more than 2.5 times of that of GCr 15; high-temperature mechanical properties at 500 ℃: r is _m ≥2100MPa，R _p0.2 ≥1400MPa，A ₅ ≥11％。

3. Advantageous effects

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention fully utilizes the inclusion modification effect and the corrosion resistance effect of La and Y, simultaneously ensures that the corrosion resistance coefficient I is more than or equal to 2.40, the corrosion resistance of the steel reaches more than 2.5 times of GCr15 of the universal bearing steel, and realizes the high strength, the high toughness and the excellent fatigue property of the steel due to the comprehensive effect of inclusion modification and composite alloying, thereby achieving the aim of taking the corrosion resistance and the heat resistance into consideration;

(2) the proper amount of Co and W elements is added into the bearing steel, so that the high strength of the bearing steel at the high temperature of 500 ℃ is further ensured.

Drawings

The technical solution of the present invention will be described in further detail with reference to the accompanying drawings and examples, but it should be understood that these drawings are designed for illustrative purposes only and thus are not intended to limit the scope of the present invention. Furthermore, unless otherwise indicated, the drawings are intended to be illustrative of the structural configurations described herein and are not necessarily drawn to scale.

FIG. 1 is a SEM photograph showing the morphology of inclusions in example 1 of the present invention;

FIG. 2 is an SEM photograph of precipitated carbides in example 1 of the present invention.

Detailed Description

The following detailed description of exemplary embodiments of the invention refers to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration exemplary embodiments in which the invention may be practiced. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be realized and that various changes to the invention may be made without departing from the spirit and scope of the present invention. The following more detailed description of the embodiments of the invention is not intended to limit the scope of the invention, as claimed, but is presented for purposes of illustration only and not limitation to describe the features and characteristics of the invention, to set forth the best mode of carrying out the invention, and to sufficiently enable one skilled in the art to practice the invention. Accordingly, the scope of the invention is to be limited only by the following claims.

The invention adopts the steel grade with the following components, and adopts the following process to produce: electric arc furnace or converter smelting → LF furnace refining → RH vacuum degassing → continuous casting of a big square billet of 380mm to 600mm → rolling of a 250 square billet → rolling of a bar of phi 15 mm to 80 mm. The steel compositions of the examples and comparative examples are shown in Table 1, and the specific process parameters are shown in Table 2.

TABLE 1 chemical composition in wt% of inventive examples

	C	Si	Cr	Ni	Co	W	La	Y	P	S	Ti	O	Value of A	Value of I
															Example 1	0.50	0.30	2.5	1.00	1.00	1.10	0.010	0.025	0.010	0.005	0.004	0.0012	0.23	2.46
Example 2	0.60	0.40	2.2	1.20	0.80	1.30	0.025	0.010	0.012	0.007	0.004	0.0009	0.21	2.54
															Example 3	0.52	0.38	2.27	1.15	0.83	1.24	0.016	0.020	0.012	0.003	0.005	0.0008	0.27	2.55
Example 4	0.56	0.32	2.46	1.04	0.92	1.16	0.021	0.014	0.009	0.006	0.003	0.0010	0.24	2.48
															Example 5	0.58	0.34	2.33	1.17	0.85	1.21	0.020	0.017	0.011	0.002	0.004	0.0009	0.33	2.54
Example 6	0.53	0.36	2.41	1.09	0.94	1.19	0.013	0.019	0.011	0.002	0.004	0.0008	0.29	2.48
															Example 7	0.57	0.37	2.38	1.11	0.91	1.13	0.016	0.022	0.012	0.004	0.003	0.0009	0.31	2.60
Comparative example 1	0.55	0.34	2.39	1.17	0.22	0.21	0.017	0.015	0.009	0.004	0.004	0.0009	0.24	2.47
															Comparative example 2	0.56	0.36	2.41	1.09	0.94	1.17	0.005	0.007	0.012	0.002	0.005	0.0011	0.09	2.11
Comparative example 3	0.54	0.33	2.29	1.13	0.88	1.23	0.012	0.013	0.013	0.007	0.005	0.0011	0.13	2.28
															Comparative example 4	1.01	0.27	1.51	/	/	/	/	/	0.012	0.003	0.005	0.0010	/	/

TABLE 2 concrete process parameters of inventive examples and comparative examples

All samples were heat treated using the following heat treatment process: spheroidizing annealing at 810 ℃ (oil cooling) → 190 ℃ (air cooling).

And (3) carrying out performance detection after heat treatment, wherein the performance detection method comprises the following steps:

detecting the maximum size and the form of the inclusion: taking a longitudinal sample for sample grinding and polishing, scanning and analyzing inclusions by adopting ASPEX, and determining the distribution, the size and the shape and the like of the inclusions, wherein the maximum size and the shape of the inclusions are one of main factors influencing the fatigue life of steel. As shown in FIG. 1, the distribution and size morphology of the inclusions in example 1 showed a maximum size of 9.3mm and a spherical shape.

Carbide size: carbide analysis was performed by transmission electron microscopy and carbide size was measured. As shown in FIG. 2, the maximum size of the carbide of example 1 was 0.53. mu.m.

Tensile property: a standard tensile sample with the diameter of 10mm is processed, a tensile test is carried out at room temperature, and Rm, Rp0.2 and A5 values are tested.

Hardness: and removing a transverse sample, grinding the transverse sample, and testing the HRC value on a Rockwell hardness machine, wherein the test point is one half of the radius.

Normal temperature impact energy: and (3) processing the impact sample of the U-shaped groove, performing impact test at room temperature according to GB/T229 method for testing impact of metal materials Charpy pendulum bob, obtaining three groups of impact toughness, and calculating an average value.

Contact fatigue test: and (3) measuring the contact fatigue life parameter by adopting a thrust sheet type contact mode similar to that of a thrust ball bearing under the Hertz stress of 3.5-4.0 GPa.

40h salt spray test: samples were taken from the billets and 150mm by 57mm by 0.8mm specimens were processed and tested in a circulating corrosive salt spray cabinet. SST is carried out according to GB/T10125 salt fog test of artificial atmosphere corrosion test, wherein a corrosion medium is 5 percent NaCl solution, the temperature in a test box is (35 +/-2) DEG C, and a continuous spraying mode is adopted. Every 80cm ² The amount of the salt mist sedimentation of (2) is about 1.5 mL/h. The test is carried out for 32h, after the test is finished, corrosion products are removed according to a physical and chemical method specified by ISO 8407, then the materials are cleaned, dried and weighed, and the unit weight loss rate W is calculated according to the following formula:

in the formula: w-weight loss per unit, g/m ^-2 (ii) a G0 — sample original weight, G; g1-weight after test specimen, G; a is sample length, mm; b-sample width, mm; c-specimen thickness, mm.

High-temperature tensile test: the test was carried out according to GB/T4338 "method for testing high temperature tensile strength of Metal Material", and Rm, Rp0.2 and A5 values at 500 ℃ were measured.

These results are shown in table 3.

TABLE 3 List of Performance test cases of inventive and comparative examples

The chemical component composition and the production method of the steels in the experimental examples 1 to 7 are properly controlled, the chemical components of the steels are ensured to be more than or equal to 0.21 and less than or equal to 0.34, the inclusion modification effect and the corrosion resistance effect of La and Y are fully utilized, the corrosion resistance coefficient I is ensured to be more than or equal to 2.40, the corrosion resistance of the steels is more than 2.5 times of that of the general bearing steel GCr15 (the comparison example 4 is GCr15), the high strength, the high toughness and the excellent fatigue performance of the steels are realized due to the comprehensive effect of the inclusion modification and the composite alloying, the proper amount of elements such as Co, W and the like are added, the steels can still maintain the high strength at the high temperature of 500 ℃, and the aim of considering both the corrosion resistance and the heat resistance of the steels is fulfilled.

Comparative example 1 is an example in which the addition of Co and W alloy elements is insufficient, resulting in that the strength and hardness of the steel at normal temperature are low, and the strength is greatly reduced at high temperature, failing to satisfy heat resistance; comparative example 2 is an example of insufficient addition of La and Y elements, which first results in insufficient modification of inclusions, still contains large long-strip-shaped inclusions in the steel, seriously prolongs the fatigue life of the steel, and in addition, no excess La and Y elements participate in formation of a rust layer, and the corrosion resistance is also insufficient; comparative example 3 the chemical composition is in the required range, but the A value and the I value do not reach the requirements, and in addition, the holding time of LF white slag and the RH pure degassing time are insufficient in the production process, so that the inclusion in the steel does not reach the requirements of the invention, and the fatigue life and the corrosion resistance are both low; comparative example 4 is a commercial bearing steel GCr15, which has high room temperature strength and hardness but does not have corrosion resistance and heat resistance.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and those skilled in the art can make various changes and modifications without departing from the scope of the present invention, and the present invention also includes equivalent embodiments.

Claims

1. The bearing steel is characterized by comprising the following components in percentage by weight: 0.50% to 0.60% carbon, 0.30% to 0.40% silicon, 2.20% to 2.50% chromium, 1.00% to 1.20% nickel, 0.80% to 1.00% cobalt, 1.10% to 1.30% tungsten, 0.010% to 0.025% lanthanum, 0.010% to 0.025% yttrium, a trace to 0.015% sulfur, 0.005% or less titanium, 0.0015% or less oxygen, a trace to 0.015% phosphorus, the balance being Fe and other unavoidable impurities; wherein elements in the bearing steel satisfy the following relational expressions 1 and 2:

relational expression 1: coefficient of fluidity of molten steel

And A is more than or equal to 0.21 and less than or equal to 0.34;

relational expression 2: corrosion resistance coefficient I ═ 1.46 Si +0.37 Cr +0.55 Ni +18.2 La + 19.0Y-0.11 Ni ² And I is more than or equal to 2.40; the size of carbide in the bearing steel structure is less than or equal to 0.8 mu m; tensile property: r _m ≥2300MPa，R _p0.2 ≥1600MPa，A ₅ Not less than 3.5 percent; the hardness HRC is more than or equal to 58; impact energy A at normal temperature _KU Not less than 13J, contact fatigue life L ₁₀ ≥5.0×10 ⁷ Resistance to Cl ^- The corrosion performance of the bearing steel is more than 2.5 times of that of GCr 15; high-temperature mechanical properties at 500 ℃: r is _m ≥2100MPa，R _p0.2 ≥1400MPa，A ₅ ≥11％。

2. A method of producing a bearing steel according to claim 1, wherein the method comprises: smelting → LF furnace refining → RH vacuum degassing → continuous casting of a 380 mm-700 mm big square billet → rolling of a 250 square billet → rolling of a phi 15-80 mm bar, wherein the bearing steel bar comprises the following components in percentage by weight: 0.50% to 0.60% carbon, 0.30% to 0.40% silicon, 2.20% to 2.50% chromium, 1.00% to 1.20% nickel, 0.80% to 1.00% cobalt, 1.10% to 1.30% tungsten, 0.010% to 0.025% lanthanum, 0.010% to 0.025% yttrium, trace to 0.015% sulfur, less than or equal to 0.005% titanium, less than or equal to 0.0015% oxygen, trace to 0.015% phosphorus, the balance being Fe and other unavoidable impurities; wherein elements in the bearing steel satisfy the following relational expressions 1 and 2:

relational expression 1: coefficient of fluidity of molten steel

And A is more than or equal to 0.21 and less than or equal to 0.34;

relational expression 2: corrosion resistance coefficient I ═ 1.46 Si +0.37 Cr +0.55 Ni +18.2 La + 19.0Y-0.11 Ni ² And I is more than or equal to 2.40.

3. A production method of bearing steel according to claim 2, characterized by comprising the following specific steps:

s101, smelting: bottom argon blowing is carried out before tapping, the argon blowing flow is adjusted on the basis that molten steel does not tumble a tapping ladle, the tapping is carried out when slag is generated, and the slag discharge amount is strictly controlled to be more than 90 mm;

s102, refining: deoxidizing and desulfurizing, and selecting proper proportion of CaO-SiO for white slag ₂ -MgO slag sample, white slag retention time is above 20 min; simultaneously controlling FeO + MnO in the refining slag<l.0wt％；

S103, vacuum degassing: RH continuously carries out circular degassing operation to remove gas and impurities in the molten steel, and pure degassing time is controlled to be more than or equal to 15min so as to ensure that O is less than or equal to 0.0015 wt% and Ti is less than or equal to 0.005 wt% after vacuum treatment;

s104, continuous casting: electromagnetic stirring is adopted, an La line and a Y line are added into a crystallizer, protective casting is adopted in the whole process, a crystallizer liquid level control system is adopted, the fluctuation of the liquid level is controlled to be less than or equal to +/-2.5 mm, and the superheat degree is controlled to be 30-40 ℃; continuously casting a large square billet of 380-600 mm, and then putting the large square billet into a pit for slow cooling for more than or equal to 36 hours;

s105, rolling a bar with the diameter of 15-80 mm: the soaking temperature of the heating furnace is 1300-1400 ℃.

4. The method for producing a bearing steel according to claim 3, wherein the inclusions obtained from the bearing steel bar have a maximum size of 10 μm or less and are spherical in shape.

5. A method of producing bearing steel according to claim 4, further comprising the steps of: s106, heat treatment: spheroidizing annealing at 810 deg.C → quenching oil cooling at 880 deg.C → annealing air cooling at 190 deg.C.

6. A production method of bearing steel according to claim 5, characterized in that the size of carbides in the bar structure of the bearing steel obtained after heat treatment is less than or equal to 0.8 μm; tensile property: r _m ≥2300MPa，R _p0.2 ≥1600MPa，A ₅ Not less than 3.5 percent; the hardness HRC is more than or equal to 58; impact energy A at normal temperature _KU Not less than 13J, contact fatigue life L ₁₀ ≥5.0×10 ⁷ Resistance to Cl ^- The corrosion performance of the bearing steel is more than 2.5 times of that of GCr 15; high-temperature mechanical properties at 500 ℃: r _m ≥2100MPa，R _p0.2 ≥1400MPa，A ₅ ≥11％。