CN114058970B

CN114058970B - Production method of bearing steel

Info

Publication number: CN114058970B
Application number: CN202111389730.1A
Authority: CN
Inventors: 顾超; 黄永生; 包燕平; 刘宇; 肖微; 赵阳; 王仲亮; 王敏
Original assignee: University of Science and Technology Beijing USTB; Zenith Steel Group Co Ltd
Current assignee: University of Science and Technology Beijing USTB; Zenith Steel Group Co Ltd
Priority date: 2021-11-22
Filing date: 2021-11-22
Publication date: 2022-04-22
Anticipated expiration: 2041-11-22
Also published as: CN114058970A

Abstract

The invention provides a production method of bearing steel, which mainly adopts weak deoxidizers such as silicon series and manganese series to replace aluminum series strong deoxidizers, matches with refining slag diffusion deoxidation and RH vacuum deoxidation, accurately controls the component content in the processes of converter, LF refining and RH refining through production parameter adjustment and narrow component connection among all working procedures, matches with LF refining slagging process, can reach the target component requirement in a shorter refining period, realizes that the chemical components of bearing steel meet the design requirement, the residual elements Al are less than or equal to 0.0010%, Ti is less than or equal to 0.0010%, O, N and S are respectively less than or equal to 0.0010%, less than or equal to 0.0025% and less than or equal to 0.0050%, the quantity and form of inclusions are in controllable level, B-type inclusions are less than or equal to 0.5 grade, D-type and Ds-type inclusions are not present, the fatigue life of steel is prolonged, the castability of a small square billet continuous casting process is enhanced, and the smelting period is easy to control is short, and the operation is easy to control.

Description

Production method of bearing steel

Technical Field

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

Background

In recent years, with the rapid development of equipment manufacturing industry in China, the use amount of bearings is gradually increased, and the use scenes are continuously expanded. The bearing is in a complex alternating stress state for a long time, and is required to have service performances such as high hardness, high wear resistance, high elastic limit, high contact fatigue strength and the like. Therefore, in the production of bearing steel, the technological process needs to be strictly controlled, the purity of steel is improved, and the high precision, the long service life and the high reliability of the bearing are ensured. The process flow commonly adopted for producing bearing steel at home and abroad is BOF (EAF) → LF → RH (VD) → CC, aluminum deoxidation is carried out during tapping and LF refining, high-alkalinity slag is produced to adsorb impurities, the components of final steel products meet the standard requirements, the international bearing steel quality classification standard requires that the ultra-high purity bearing steel T [ O ] is less than or equal to 5ppm, S is less than or equal to 20ppm, Ti is less than or equal to 10ppm, the total level of the impurities is less than or equal to 2.0, the maximum size is less than or equal to 20mm, and the fatigue life is more than 108.

However, the traditional aluminum deoxidation bearing steel smelting process mainly has the following problems: (1) cleanliness of molten steel: because aluminum is adopted for deoxidation in the whole process, Al2O3 inclusions are inevitably left in molten steel, and the inclusions are hard in texture, do not deform during rolling and have great destructive effect on the continuity of a steel matrix. And the reaction of aluminum with refining slag and refractory materials can also produce magnesium aluminate spinel type inclusions and even large-particle Ds type inclusions. (2) Fatigue life: the size of inclusions in bearing steel is inversely related to their fatigue life, and in addition to this, the type of inclusions also has an effect on fatigue life. The worse the plasticity of inclusions, the sharper the edge, the more easily it has a destructive effect on the steel substrate. Al2O3, magnesium aluminate spinel and Ds type inclusions which are common in the traditional aluminum deoxidation process are just nonmetallic inclusions with the characteristics, and are easy to become crack sources to reduce the fatigue life of bearing steel. (3) Nozzle nodulation in the production process: al2O3 inclusions which cannot be floated upwards and removed in molten steel accumulate on the surface of a submerged nozzle, so that the liquid level of crystallizer steel fluctuates to roll slag, and the nozzle is blocked and cannot be cast when the liquid level is serious; meanwhile, the nozzle nodules are randomly peeled off, so that the quality stability of the bearing steel is influenced; because the diameter of the water gap is small, the harm of the water gap nodulation is particularly obvious when the bearing steel billet is continuously cast.

At present, the non-aluminum deoxidized bearing steel is tried more at home and abroad, and basically, multi-step refining operation is required. Chinese patent CN106811577 discloses a bearing steel smelting process beneficial to controlling inclusions, which adopts silicon deoxidation to replace the traditional aluminum deoxidation, realizes the plasticization of the inclusions through proper variation of top slag alkalinity, avoids the occurrence of D-type and Ds-type inclusions, can control the B-type inclusions to be less than or equal to 0.5 grade, and controls the T [ O ] of a rolled material to be less than 10 ppm. Chinese patent CN109055664A discloses a deoxidation control method for bearing steel liquid without Ds-type inclusions, which comprises a pre-deoxidation slagging process from steel alloying to LF treatment position, an LF treatment process and an RH refining process, wherein Ds-type inclusions are thoroughly removed under the condition of not adopting Al deoxidation by controlling the components of the steel liquid, the alkalinity of refining slag, the treatment time and the blowing gas flow at each stage, and the oxygen is controlled below 10 ppm. Obviously, in order to control the medium oxygen content of the bearing steel to be lower than 10ppm and ensure the cleanliness of the steel in the prior art, each step of operation needs to be accurately controlled and corresponding targets are achieved, which undoubtedly increases the smelting difficulty and prolongs the average smelting period, in the Chinese patent CN109055664A, the LF refining time is 35-45min, the RH refining time is more than 50min, the two-stage refining periods cannot be well connected and matched, and the middle waiting process is easy to generate component and temperature fluctuation, thereby affecting the whole production flow. Therefore, the smelting process of the non-aluminum deoxidized bearing steel, which can cooperatively control the cleanliness and the oxygen content of the molten steel and shorten the smelting period, is particularly urgent.

Disclosure of Invention

The invention provides a novel bearing steel production method which is beneficial to improving the cleanliness of molten steel, prolonging the fatigue life of steel products, enhancing the castability in the continuous casting process of small square billets, and has short smelting period and easy control of operation, aiming at the problems of the traditional bearing steel adopting an aluminum strong-deoxidation smelting process. The method mainly adopts a silicon series and manganese series weak deoxidizer to replace an aluminum series strong deoxidizer, and is matched with the diffusion deoxidation of refining slag and RH vacuum deoxidation, and the chemical components of the bearing steel meet the design requirements through the production parameter adjustment and narrow component connection among the working procedures, the chemical components of the residual element Al are less than or equal to 0.0010%, Ti is less than or equal to 0.0010%, O, N and S are respectively less than or equal to 0.0010%, less than or equal to 0.0025% and less than or equal to 0.0050%, B-type inclusions are less than or equal to 0.5, D-type and Ds-type inclusions are not contained, the small section castability is good, and the fatigue life is improved.

The invention firstly provides a production method of high-cleanness bearing steel, which adopts a process flow of KR-BOF-LF-RH-CC and is characterized by mainly comprising the following steps:

(1) the converter smelting adopts high carbon-drawing operation, the oxygen blowing amount per ton of steel is less than or equal to 50Nm3, and the oxygen blowing time per furnace is less than or equal to 13 min; controlling the tapping time of the converter to be more than or equal to 0.15 percent of C, more than or equal to 0.004 percent of Si, less than or equal to 0.015 percent of O, less than or equal to 0.015 percent of P, less than or equal to 0.006 percent of S, less than or equal to 0.0005 percent of Ti, controlling the tapping temperature to be more than or equal to 1635 ℃ and controlling the tapping time to be more than or equal to 4 min;

(2) c is more than or equal to 0.78 percent and less than or equal to 0.85 percent of molten steel arriving at a station, Si is more than or equal to 0.16 percent and less than or equal to 0.25 percent, Mn is more than or equal to 0.26 percent and less than or equal to 0.40 percent, Cr is more than or equal to 1.40 percent and less than or equal to 1.60 percent, O is less than or equal to 0.008 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.006 percent, Ti is less than or equal to 0.0008 percent, and the temperature is more than or equal to 1510 percent; the LF treatment time is 30-40min, silica is added in the refining process to control alkali to be 1.3-2.7, the LF end point controls the main components of molten steel to meet the design requirements, C is more than or equal to 1.20% and less than or equal to 1.40%, O is more than or equal to 0.002% and less than or equal to 0.003%, N is less than or equal to 0.003%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Ti is less than or equal to 0.001%, and the temperature is 1550-;

(3) RH vacuum treatment time is 15-20min, wherein the time that the pressure of the vacuum chamber is less than or equal to 67Pa is more than or equal to 8min, and the soft blowing time is 15-25min after the vacuum treatment is finished;

(4) the continuous casting process requires that the ladle is baked to more than 1150 ℃, the whole process is protected for casting, the long water gap and the submerged water gap are sealed by argon, and the tundish covering agent and the crystallizer casting powder are made of special materials for bearing steel.

Further, before the working procedure of the converter, KR desulfurization arrival molten iron is controlled to meet the conditions that Si is more than or equal to 0.30% and less than or equal to 0.70%, P is less than or equal to 0.15%, S is less than or equal to 0.025%, Sn is less than or equal to 0.02%, As is less than or equal to 0.05%, Ti is less than or equal to 0.05%, and the temperature of the molten iron is more than or equal to 1300 ℃; ensuring that the desulphurization slag is completely removed and ensuring that S is less than or equal to 0.003 percent when the desulphurization slag is discharged.

And further, carrying out deoxidation alloying after tapping for 90s by the converter, and adding 1-1.5 kg/t of low-nitrogen pure silicon steel, 2-2.5 kg/t of low-carbon ferromanganese steel, 1.8-2 kg/t of low-titanium low-aluminum ferrosilicon steel and 22-25 kg/t of low-titanium high-carbon ferrochrome steel into a steel ladle.

Further, when LF refining is started, refined lime is added into the steel according to the proportion of 1.5-2kg/t for slagging, slag regulators such as fluorite and calcium carbide are added according to needs, and low-nitrogen pure silicon is used as a refining slag deoxidizer and is added according to the proportion of 0.8-1.2 kg/t for steel.

Furthermore, silica is added in the LF refining process to control the alkalinity, the alkalinity is required to be between 2.4 and 2.7 in the first 20min, and the alkalinity is required to be between 1.3 and 1.5 after slag change.

Preferably, the alkalinity is controlled to be 2.5 in the first 20min, 1.4 after slag changing and 2-3min in the process of LF refining.

Further, carbon powder, silicon-based ferroalloy and chromium-based ferroalloy used for component adjustment in the LF refining process all require low nitrogen, low titanium and low aluminum.

Further, the RH end point requires that the main component of the molten steel meets the design requirement, the residual element O is less than or equal to 0.001%, the N is less than or equal to 0.002%, the P is less than or equal to 0.015%, the S is less than or equal to 0.005%, the Ti is less than or equal to 0.001%, and the temperature is between 1500 ℃ and 1525 ℃.

Furthermore, the bearing steel comprises the components of 0.96-1.02 percent of C, 0.16-0.30 percent of Si, 0.26-0.42 percent of Mn, 1.42-1.62 percent of Cr and 0.08 percent of Mo.

The invention optimally controls the components, the operation process and the parameters of each link according to the quantity, the size and the shape change trend of inclusions in the steelmaking and refining processes and the actual situation of industrial production. Non-aluminum deoxidation alloys such as low-nitrogen pure silicon, low-carbon ferromanganese, low-titanium low-aluminum ferrosilicon and the like are added in the converter tapping process to form a large amount of deoxidation products with oxygen in steel, the amount is large, the size is large, and the deoxidation products are easy to remove in the argon blowing process; in the LF refining process, as the dissolved oxygen is obviously lower than that of converter tapping, the size of generated inclusions is smaller and the inclusions are generated continuously; in the RH vacuum refining process, the continuous collision, aggregation and growth of the inclusion can be promoted by the circular stirring of the molten steel, and the floating removal effect of the inclusion is better than that of the LF refining process. According to the invention, the quantity and the form of the inclusions are controlled under the condition that the alloy components of the slag reach the standard by controlling the alkalinity, the refining time and the carbon and oxygen content of the slag in the LF refining process, and further, the slag changing time of the LF refining is controlled, so that large-particle deoxidation products from the converter tapping to the early stage of refining are rapidly eliminated, in addition, the dissolved oxygen in the molten steel is kept in a certain range, small inclusions with a certain size can be generated, through the cooperation with the RH vacuum refining process, the collision aggregation and the floating removal of the inclusions can be accelerated, and the target component requirements are met in a short refining period.

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

(1) the contents of Al, Ti and N in the bearing steel produced by the method are far lower than the national standard requirement, so that the number of inclusions of TiN, Al2O3 and CaO-Al2O3 which have the greatest harm to the fatigue life in the bearing steel is greatly reduced. The total oxygen content of the bearing steel produced by the method is obviously higher than that of aluminum deoxidized bearing steel and is 8-10 ppm, but the fatigue life of the bearing steel can reach or even exceed that of strong deoxidized bearing steel with the total oxygen content of 4-5 ppm. The production method mainly changes the type of the inclusions in the bearing steel, so that the inclusions are mainly silicate inclusions, and the influence of the inclusions on the fatigue life is reduced.

(2) According to the invention, by controlling the components and the slagging process, the LF refining period is equivalent to the RH refining period, can be controlled below 40min, the smelting period is shorter, and the connection and matching of the production flow are better realized.

(3) In the actual production of bearing steel, the number of continuous casting furnaces is obviously reduced along with the increase of the aluminum consumption, and the phenomenon is particularly obvious on the continuous casting of small square billets with the section of less than or equal to 160mm multiplied by 160 mm. The content of acid-soluble aluminum in the molten steel produced by the method is far lower than that of acid-soluble aluminum produced by an aluminum strong deoxidation process, so that the method is favorable for the castability of the molten steel, and the GCr15 bearing steel produced by the method has no water gap blockage phenomenon and can be continuously cast in 14-15 furnaces.

Drawings

FIG. 1 (a) is a graph showing the change in the size and number of inclusions in each step of example 1;

FIG. 1 (b) is a graph showing the change in the size and number of inclusions in each step of example 4;

FIGS. 2 (a) and (b) are SEM images of two types of inclusions after slag transformation in example 1;

FIGS. 3 (a) and (b) are SEM images of two types of inclusions after slag transformation in example 4;

Detailed Description

In order to better explain the present invention and to facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below.

The production method of the high-cleanness GCr15 bearing steel has the technical flow of KR-BOF-LF-RH-CC, and the core improvement of the invention is that the BOF-LF-RH process is adopted, the oxygen content in the bearing steel can be controlled to be lower than 10ppm in a non-aluminum weak deoxidation mode through the accurate control of a converter and a refining process, the smelting period of each process is shortened and homogenized, and each production link is well matched. The method has certain limitation on the control of the molten iron before the converter, and the method controls the KR desulfurized molten iron to a station before the working procedure of the converter to meet the conditions that Si is more than or equal to 0.30% and less than or equal to 0.70%, P is less than or equal to 0.15%, S is less than or equal to 0.025%, Sn is less than or equal to 0.02%, As is less than or equal to 0.05%, Ti is less than or equal to 0.05%, and the temperature of the molten iron is more than or equal to 1300 ℃; ensures that the desulfurized slag is completely removed and ensures that S is less than or equal to 0.003 percent when the desulfurized slag is discharged, and can ensure the stability of the smelting process of the converter without generating overlarge fluctuation on the subsequent process under the limit. The present invention has strict limitations on the converter smelting, LF refining and RH vacuum refining processes, and is specifically illustrated by the following examples of producing small square billet bearing steel of 160mm × 160mm by continuous casting, which are only simple examples of the present invention and do not represent or limit the scope of the present invention, which is subject to the claims.

Example 1

A production method of high-cleanness bearing steel comprises the following steps:

(1) the converter smelting adopts high carbon-drawing operation, the oxygen blowing amount per ton of steel is 50Nm3, and the oxygen blowing time is 12 min; tapping C0.16% by using a converter, Si 0.005%, O0.012%, P0.013%, S0.0055%, Ti 0.0004%, tapping temperature 1640 ℃, and tapping time 4.3 min; and (3) carrying out deoxidation alloying after tapping for 90s by the converter, and adding 1.3kg/t of low-nitrogen pure silicon steel, 2.2kg/t of low-carbon ferromanganese steel, 1.8kg/t of low-titanium low-aluminum ferrosilicon steel and 22kg/t of low-titanium high-carbon ferrochrome steel into a steel ladle.

(2) The LF furnace controls the arrival molten steel C to be 0.81%, Si to be 0.25%, Mn to be 0.39%, Cr to be 1.58%, O to be 0.0074%, P to be 0.015%, S to be 0.006%, Ti to be 0.0007%, and the temperature to be 1558 ℃. When LF refining is started, 1.5kg/t steel of refined lime is added into slag, slag adjusting agents such as fluorite, calcium carbide and the like are added according to needs, and low-nitrogen pure silicon is used as a refining slag deoxidizer and is added according to 0.8kg/t steel. Adding silica in the refining process to control the alkalinity, wherein the alkalinity is required to be controlled to be about 2.5 in the first 20min, the alkalinity is controlled to be about 1.4 after slag changing, the slag changing process time is 3min, the LF refining treatment time is 35min, the LF end point control molten steel main components meet the design requirements, and the sampling analysis results comprise 1.24% of C, 0.003% of O, 0.0028% of N, 0.014% of P, 0.0045% of S, 0.0009% of Ti and 1575 ℃.

(3) RH vacuum treatment time is 20min, wherein the time that the pressure of a vacuum chamber is less than or equal to 67Pa is 10min, soft blowing time is 20min after the vacuum treatment is finished, and RH end point temperature is 1520 ℃;

The RH end point molten steel was sampled and analyzed, and the residual elements O were 0.001%, N was 0.0018%, P was 0.014%, S was 0.0048%, and Ti was 0.0009%. The continuous casting billet is sampled and analyzed, and the components of the continuous casting billet are C1.02%, Si 0.29%, Mn 0.38%, Cr 1.58% and Mo 0.08%.

Example 2

(1) the converter smelting adopts a high carbon-drawing operation, the oxygen blowing amount per ton of steel is 48Nm3, and the oxygen blowing time is 13 min; tapping C0.18% by using a converter, Si 0.004%, O0.014%, P0.014%, S0.0054% and Ti 0.0005%, wherein the tapping temperature is 1638 ℃, and the tapping time is 5 min; and (3) carrying out deoxidation alloying after tapping for 90s by the converter, and adding 1.3kg/t of low-nitrogen pure silicon steel, 2.3kg/t of low-carbon ferromanganese steel, 1.9kg/t of low-titanium low-aluminum ferrosilicon steel and 23kg/t of low-titanium high-carbon ferrochrome steel into a ladle.

(2) The LF furnace controls arrival molten steel C0.83%, Si 0.19%, Mn 0.35%, Cr 1.55%, O0.0076%, P0.012%, S0.0057%, Ti 0.0008%, and temperature 1551 ℃. When LF refining is started, 1.7kg/t steel of refined lime is added into slag, slag adjusting agents such as fluorite, calcium carbide and the like are added according to needs, and low-nitrogen pure silicon is used as a refining slag deoxidizer and is added according to 0.9kg/t steel. Adding silica in the refining process to control the alkalinity, wherein the alkalinity is required to be controlled to be about 2.4 in the first 20min, the alkalinity is controlled to be about 1.5 after slag changing, the slag changing process time is 2min, the LF refining treatment time is 35min, the LF endpoint control molten steel main components meet the design requirements, and the sampling analysis results comprise 1.33% of C, 0.0028% of O, 0.0025% of N, 0.014% of P, less than or equal to 0.0037% of S, 0.001% of Ti and 1566 ℃.

(3) RH vacuum treatment time is 18min, wherein the time of the vacuum chamber pressure is less than or equal to 67Pa is 8min, soft blowing time is 25min after the vacuum treatment is finished, and RH end point temperature is 1523 ℃;

The RH end point molten steel was sampled and analyzed, and the residual elements O were 0.0009%, N was 0.0020%, P was 0.014%, S was 0.0035%, and Ti was 0.001%. The continuous casting billet is analyzed by sampling, and the components of the continuous casting billet are C1.01%, Si 0.27%, Mn 0.37%, Cr 1.48% and Mo 0.06%.

Example 3

(1) the converter smelting adopts high carbon-drawing operation, the oxygen blowing amount per ton of steel is 49Nm3, and the oxygen blowing time is less than or equal to 13 min; tapping C0.18% by using a converter, Si 0.005%, O0.012%, P0.015%, S0.0053%, Ti 0.0001%, tapping temperature 1635 ℃, and tapping time 4.5 min; and (3) carrying out deoxidation alloying after tapping for 90s by the converter, and adding 1.5kg/t of low-nitrogen pure silicon steel, 2.4kg/t of low-carbon ferromanganese steel, 2kg/t of low-titanium low-aluminum ferrosilicon steel and 25kg/t of low-titanium high-carbon ferrochrome steel into a steel ladle.

(2) The LF furnace controls 0.84% of arrival molten steel C, 0.24% of Si, 0.38% of Mn, 1.53% of Cr, 0.0074% of O, 0.015% of P, 0.0054% of S, 0.0002% of Ti and 1555 ℃. When LF refining is started, refined lime is added into slag according to 2kg/t steel, slag regulators such as fluorite and calcium carbide are added according to needs, and low-nitrogen pure silicon is used as a refining slag deoxidizer and is added according to 1kg/t steel. Adding silica in the refining process to control the alkalinity, wherein the alkalinity is required to be controlled to be about 2.7 in the first 20min, the alkalinity is controlled to be about 1.3 after slag changing, the slag changing process time is 3min, the LF refining treatment time is 35min, the LF endpoint control molten steel main components meet the design requirements, and the sampling analysis result shows that C is 1.24%, O is 0.0026%, N is 0.0029%, P is 0.015%, S is 0.0044%, Ti is 0.0007%, and the temperature is 1570 ℃.

(3) RH vacuum treatment time is 19min, wherein the time that the pressure of a vacuum chamber is less than or equal to 67Pa is 11min, soft blowing time is 20min after the vacuum treatment is finished, and RH end point temperature is 1522 ℃;

The RH end point molten steel is sampled and analyzed, wherein the residual elements comprise 0.001 percent of O, 0.002 percent of N, 0.015 percent of P, 0.0043 percent of S and 0.0007 percent of Ti. The continuous casting billet is sampled and analyzed, and the components of the continuous casting billet are C1.02%, Si 0.29%, Mn 0.41%, Cr 1.60% and Mo 0.08%.

The embodiment 1-3 belongs to the same casting time in the production process, the molten steel is kept in the same condition range of the production method in the production process, no water gap blockage phenomenon exists, and the continuous casting 15 furnaces are realized in the casting time.

Example 4

(1) the converter smelting adopts high carbon-drawing operation, oxygen blowing amount per ton of steel is 49Nm3, and oxygen blowing time is 13 min; tapping C0.16% by using a converter, Si 0.0045%, O0.015%, P0.013%, S0.0058%, Ti 0.0005%, tapping temperature 1640 ℃, and tapping time 4 min; and (3) carrying out deoxidation alloying after tapping for 90s by the converter, and adding 1.2kg/t of low-nitrogen pure silicon steel, 2.1kg/t of low-carbon ferromanganese steel, 1.9kg/t of low-titanium low-aluminum ferrosilicon steel and 23kg/t of low-titanium high-carbon ferrochrome steel into a ladle.

(2) The LF furnace controls the arrival molten steel C to be 0.83%, Si to be 0.25%, Mn to be 0.38%, Cr to be 1.58%, O to be 0.0078%, P to be 0.015%, S to be 0.006%, Ti to be 0.0008%, and the temperature to be 1540 ℃. When LF refining is started, 1.6kg/t steel of refined lime is added into slag, slag adjusting agents such as fluorite, calcium carbide and the like are added according to needs, and low-nitrogen pure silicon is used as a refining slag deoxidizer and is added according to 0.9kg/t steel. Adding silica in the refining process to control the alkalinity to be 1.05-2.0, controlling the alkalinity to be about 1.9 in the first 30min, controlling the alkalinity to be about 1.2 after slag changing, refining the LF for 45min, controlling the main components of the molten steel to meet the design requirements at the LF end point, wherein the main components comprise 1.04% of C, 0.0019% of O, 0.003% of N, 0.015% of P, 0.0049% of S, 0.001% of Ti and 1559 ℃.

(3) RH vacuum treatment time is 26min, wherein the time that the pressure of a vacuum chamber is less than or equal to 67Pa is 15min, the soft blowing time is 35min after the vacuum treatment is finished, and the RH end point temperature is 1515 ℃;

And (3) sampling and analyzing RH end point molten steel, wherein the residual elements comprise 0.001% of O, 0.0019% of N, 0.015% of P, 0.0049% of S and 0.001% of Ti. The continuous casting billet is sampled and analyzed, and the components of the continuous casting billet are C1.01%, Si 0.30%, Mn 0.38%, Cr 1.61% and Mo 0.07%.

Before LF slag transformation, after LF slag transformation, RH end point and continuous casting billet in the

embodiments

1 and 4 are sampled, and the result analysis of the full-automatic scanning electron microscope of the inclusions is carried out, and the obtained number density and size distribution change of the inclusions are shown in figure 1, so that the data and size of the inclusions in the LF process in the embodiment 1 are higher than those in the embodiment 4, but the final RH end point is equivalent to the number of the inclusions in the continuous casting billet.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A production method of bearing steel comprises the following components of 0.96% to 1.02% of C, 0.16% to 0.30% of Si, 0.26% to 0.42% of Mn, 1.42% to 1.62% of Cr and 0.08% of Mo, and the process flow is KR-BOF-LF-RH-CC, and is characterized by mainly comprising the following steps:

(1) the converter smelting adopts high carbon-drawing operation, and the oxygen blowing amount per ton of steel is less than or equal to 50Nm³The oxygen blowing time of each furnace is less than or equal to 13 min; controlling the tapping time of the converter to be more than or equal to 0.15 percent of C, more than or equal to 0.004 percent of Si, less than or equal to 0.015 percent of O, less than or equal to 0.015 percent of P, less than or equal to 0.006 percent of S, less than or equal to 0.0005 percent of Ti, controlling the tapping temperature to be more than or equal to 1635 ℃ and controlling the tapping time to be more than or equal to 4 min; carrying out deoxidation alloying after tapping for 90s by a converter, and adding 1-1.5 kg/t of low-nitrogen pure silicon, 2-2.5 kg/t of low-carbon ferromanganese, 1.8-2 kg/t of low-titanium low-aluminum ferrosilicon and 22-25 kg/t of low-titanium high-carbon ferrochrome into a steel ladle;

(2) c is more than or equal to 0.78 percent and less than or equal to 0.85 percent of molten steel arriving at a station, Si is more than or equal to 0.16 percent and less than or equal to 0.25 percent, Mn is more than or equal to 0.26 percent and less than or equal to 0.40 percent, Cr is more than or equal to 1.40 percent and less than or equal to 1.60 percent, O is less than or equal to 0.008 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.006 percent, Ti is less than or equal to 0.0008 percent, and the temperature is more than or equal to 1510 percent; when LF refining is started, adding refined lime into the steel according to 1.5-2kg/t for slagging, adding fluorite and calcium carbide slag modifier according to needs, and adding low-nitrogen pure silicon serving as a refining slag deoxidizer according to 0.8-1.2 kg/t; adding silica in the refining process to control the alkalinity, wherein the alkalinity is between 2.40 and 2.70 in the first 20min, the alkalinity is between 1.30 and 1.50 after slag changing, the slag changing process time is between 2 and 3min, the LF treatment time is between 30 and 40min, the LF end point controls the main components of the molten steel to meet the design requirements, C is more than or equal to 1.20 percent and less than or equal to 1.40 percent, O is more than or equal to 0.002 percent and less than or equal to 0.003 percent, N is more than or equal to 0.003 percent, P is more than or equal to 0.015 percent, S is more than or equal to 0.005 percent, Ti is less than or equal to 0.001 percent, and the temperature is between 1550 ℃ and 1575 ℃;

(3) RH vacuum treatment time is 15-20min, wherein the time that the pressure of the vacuum chamber is less than or equal to 67Pa is more than or equal to 8min, and the soft blowing time is 15-25min after the vacuum treatment is finished; the RH end point requires that the main component of the molten steel meets the design requirement, the residual element O is less than or equal to 0.001 percent, the N is less than or equal to 0.002 percent, the P is less than or equal to 0.015 percent, the S is less than or equal to 0.005 percent, the Ti is less than or equal to 0.001 percent, and the temperature is between 1500-;

2. A method for producing a bearing steel according to claim 1, wherein: before the working procedure of the converter, KR desulfurization arrival molten iron is controlled to meet the conditions that Si is more than or equal to 0.30% and less than or equal to 0.70%, P is less than or equal to 0.15%, S is less than or equal to 0.025%, Sn is less than or equal to 0.02%, As is less than or equal to 0.05%, Ti is less than or equal to 0.05%, and the temperature of the molten iron is more than or equal to 1300 ℃; ensuring that the desulphurization slag is completely removed and ensuring that S is less than or equal to 0.003 percent when the desulphurization slag is discharged.

3. A method for producing a bearing steel according to claim 1, wherein: the alkalinity is controlled to be 2.5 in the first 20min, 1.4 after slag changing and 3min in the process of LF refining.

4. A method for producing a bearing steel according to claim 1, wherein: carbon powder, silicon-based ferroalloy and chromium-based ferroalloy used for component adjustment in the LF refining process all require low nitrogen, low titanium and low aluminum.