CN115637306B - Control method for B-type inclusion in high-carbon chromium bearing steel - Google Patents
Control method for B-type inclusion in high-carbon chromium bearing steel Download PDFInfo
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- 239000010959 steel Substances 0.000 title claims abstract description 115
- 238000000034 method Methods 0.000 title claims abstract description 83
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 38
- 229910052804 chromium Inorganic materials 0.000 title claims abstract description 27
- 239000011651 chromium Substances 0.000 title claims abstract description 27
- 230000008569 process Effects 0.000 claims abstract description 46
- 238000007670 refining Methods 0.000 claims abstract description 45
- 238000010079 rubber tapping Methods 0.000 claims abstract description 31
- 238000007664 blowing Methods 0.000 claims abstract description 30
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 29
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 23
- 239000002893 slag Substances 0.000 claims abstract description 22
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 17
- 238000009749 continuous casting Methods 0.000 claims abstract description 17
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- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 9
- 239000001301 oxygen Substances 0.000 claims abstract description 9
- 229910000519 Ferrosilicon Inorganic materials 0.000 claims abstract description 7
- 230000003068 static effect Effects 0.000 claims abstract description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 20
- 229910052786 argon Inorganic materials 0.000 claims description 10
- 239000007788 liquid Substances 0.000 claims description 10
- 238000005266 casting Methods 0.000 claims description 9
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- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 3
- 238000005275 alloying Methods 0.000 claims description 3
- OOJQNBIDYDPHHE-UHFFFAOYSA-N barium silicon Chemical compound [Si].[Ba] OOJQNBIDYDPHHE-UHFFFAOYSA-N 0.000 claims description 3
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims description 3
- 239000003795 chemical substances by application Substances 0.000 claims description 3
- 239000010436 fluorite Substances 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- 239000004571 lime Substances 0.000 claims description 3
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- 229910010271 silicon carbide Inorganic materials 0.000 claims description 3
- FXNGWBDIVIGISM-UHFFFAOYSA-N methylidynechromium Chemical group [Cr]#[C] FXNGWBDIVIGISM-UHFFFAOYSA-N 0.000 claims 2
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- 229910000604 Ferrochrome Inorganic materials 0.000 description 1
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
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Abstract
A control method for B-type inclusions in high-carbon chromium bearing steel belongs to the technical field of metallurgy and comprises the working procedures of converter, LF refining, RH refining and continuous casting. The converter process adopts the modes of large bottom blowing and high carbon pulling to reduce the initial oxygen content in molten steel, and partial carburant is added for pre-deoxidation in the tapping process, and oxidation products leave the molten steel in a bubble mode and cannot pollute the molten steel; the LF refining procedure feeds aluminum wires once to ensure that Al 2 O 3 The impurities are removed in a floating way for a sufficient time; adding ferrosilicon to the residual Al after S is less than or equal to 0.005% 2 O 3 Carrying out inclusion modification treatment; RH refining is carried out by adding carbon powder after high vacuum circulation stabilization, reacting with free oxygen in slag and molten steel to generate CO bubbles, further purifying molten steel, breaking air, and utilizing Ba element to balance Al 2 O 3 The denaturation treatment is carried out so as to obtain a modified product,and removing the impurities by static blowing. The grade B coarse of B-class inclusion in the high-carbon chromium bearing steel produced by the invention is less than or equal to 0.5 grade, and the grade B fine is less than or equal to 1.5 grade.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a control method of B-type inclusions in high-carbon chromium bearing steel.
Background
The international plain bearing is "industrial heart", and the bearing industry is called "army department of national economy". The bearing permeates into various departments of national economy, and the demand of the bearing in each country always keeps a certain relation with the total national production value. In the alloy steel field, the bearing steel is one of the steel types with the most inspection projects, the most strict quality requirements and the greatest production difficulty.
The high-carbon chromium bearing steel is the most widely used bearing steel series at present, and is mainly used for manufacturing important materials of bearing rings and rolling bodies. The non-metallic inclusion in the bearing steel breaks the continuity of metal, and under the action of alternating stress generated in the working process of the bearing, the stress concentration is easy to be caused, the non-metallic inclusion becomes a fatigue crack source, and the fatigue life of the bearing steel is reduced. Therefore, reducing the inclusion content in steel is a major approach to improve the fatigue life of bearing steel. Meanwhile, because of different inclusion types, different inclusion forms, numbers, sizes and distributions, the influence on fatigue life is different, and the modification treatment of the inclusions is used as an effective means for reducing the damage of the inclusions while reducing the inclusion content.
At present, an aluminum deoxidization process is adopted in the bearing steel production process, and the aluminum deoxidization process is inevitably carried out on molten steelAdding aluminum products into the molten steel, deoxidizing to generate Al 2 O 3 Inclusions (namely B-type inclusions) can affect the product quality if the inclusions cannot be effectively removed, and the excessive degradation of the inclusions of the existing bearing steel is mostly Al 2 O 3 Caused by inclusions of Al 2 O 3 The inclusion is brittle inclusion, so that the fatigue life of the bearing is severely limited, and therefore, the B-type inclusion in the bearing steel is urgently needed to be subjected to attack, so that the inclusion reaches the level of special grade high-quality bearing steel, the degradation of the inclusion is reduced, and the fatigue life of downstream products is improved. The requirements for bearing steel inclusions in the GB/T18254-2016 standard are shown in Table 1':
table 1': non-metallic inclusion grade requirement of bearing steel
Therefore, how to control the B-class inclusion to the B-coarse level less than or equal to 0.5 and the B-fine level less than or equal to 1.5 on the premise of not increasing the cost is a technical problem to be solved in the production of high-carbon chromium bearing steel.
Disclosure of Invention
In order to solve the technical problems, the invention provides a control method for B-type inclusions in high-carbon chromium bearing steel, which adopts the following technical scheme:
the control method of B-type inclusion in high-carbon chromium bearing steel comprises the working procedures of converter, LF refining, RH refining and continuous casting;
(1) Converter process: the bottom blowing flow in the blowing process adopts a middle-small-large bottom blowing mode, and the tapped molten steel comprises the following components in percentage by mass: c:0.08 to 0.20 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.015 percent, the temperature of molten steel tapping is 1620+/-20 ℃, the tapping oxygen is less than or equal to 350ppm, and the tapping time is 3.5 to 6.0 minutes; adding into the steel ladle in the tapping process in sequence: carburant- & gt aluminum particles- & gt ferrosilicon- & gt ferromanganese- & gt residual carburant- & gt low titanium ferrochromium- & gt premelting slag, wherein three-gear tapping is utilized in the tapping process, and a ladle sample component C is obtained after tapping: 0.90 to 0.95 percent, si:0.05 to 0.10 percent, mn:0.22 to 0.30 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.015 percent, al:0.050 to 0.070%, cr:1.35 to 1.45 percent;
(2) LF refining procedure: adding 30-50 kg of silicon carbide in the early stage of LF refining, adding lime, fluorite and premelting slag for slagging, heating for 10-15 min, sampling, detecting, adjusting the contents of Mn, cr and Al according to the detection result, if Al is more than or equal to 0.040%, and if Al is less than 0.040%, feeding the molten steel into an aluminum wire at one time, wherein the feeding quantity is controlled according to the target content of Al in the molten steel by 0.050%; after S in molten steel in the middle and later stages of refining is less than or equal to 0.005%, adding ferrosilicon at one time to carry out alloying, and after the temperature of the molten steel and the components except the element C are qualified, carrying out static blowing for 5-10 min;
(3) RH refining process: maintaining the vacuum below 100Pa for 2min, adding carbon powder at one time to adjust the C content, continuously maintaining the vacuum for more than or equal to 12min after adding the carbon powder, feeding a silicon-barium wire for 200-300 m after breaking the vacuum, and soft blowing molten steel for 15-30 min; the RH refining process does not add aluminum products into the molten steel;
(4) Continuous casting process: the continuous casting adopts an argon blowing stopper rod and a submerged nozzle, when the liquid level of a tundish reaches 350mm after the ladle is opened, 150-200 kg of special protection slag for bearing steel is put into the tundish, and then a sufficient amount of covering agent is added to ensure that the liquid level of the steel is not exposed, and the stopper rod is opened to blow argon after the casting is successful.
The bottom blowing flow corresponding to the middle-small-large bottom blowing mode in the converter process is 0.06-0.04-0.08 m 3 /（min*t）。
The converter procedure, when the adding time of the first batch of carburant is 1/5 of tapping, the adding amount is 100+/-10 kg; the adding time of the aluminum particles is 10-20 s after the first carburant is added; the addition amount of the premelting slag is 6-9 kg/t steel.
The converter procedure comprises the following components in percentage by weight: caO 40-55%, siO 2 ≤10%、Al 2 O 3 30～45%、MgO≤8%、Al 3～8%。
The LF refining procedure comprises the steps of Al in refining slag components 2 O 3 The weight content is controlled between 28 and 35 percent.
The RH refining process has vacuum degree less than or equal to 100Pa and vacuum holding time more than or equal to 15min; the RH refining process only carries out carbon content adjustment, and the rest elements are all adjusted in the LF refining process.
The continuous casting process is characterized in that the special casting powder for the bearing steel is added at one time, and is not added any more in the follow-up process; the argon blowing flow of the stopper rod is 0.5-0.8L/min.
The high-carbon chromium bearing steel comprises the following components: 0.95 to 1.05 weight percent of C, 0.15 to 0.35 weight percent of Si, 0.25 to 0.45 weight percent of Mn, 1.40 to 1.65 weight percent of Cr, less than or equal to 0.020 weight percent of P, less than or equal to 0.015 weight percent of S, less than or equal to 0.0012 weight percent of O, less than or equal to 0.0015 weight percent of Ti and less than or equal to 0.00010 weight percent of Ca.
B class inclusion B coarse is less than or equal to 0.5 grade and B fine is less than or equal to 1.5 grade in the high-carbon chromium bearing steel obtained by the control method.
The design principle of the invention is as follows:
1. the converter adopts a mode of combining bottom blowing and high carbon drawing, so that the initial oxygen content in molten steel can be effectively reduced, and the addition amount of deoxidizer and inclusion formed by oxidation in the tapping process can be reduced;
2. the converter adopts the method that partial carburant is added firstly to pre-deoxidize molten steel, and carbon in the carburant reacts with oxygen to generate CO and CO 2 The produced product leaves the molten steel in a bubble mode, pollution to the molten steel is avoided, the contact between the liquid surface of the molten steel and air can be reduced by the generated bubbles on the surface of the molten steel, secondary oxidization and nitrogen increase of the molten steel are reduced, the stirring of the molten steel can be enhanced when the bubbles overflow, the rapid melting of the alloy added subsequently is promoted, the oxidizing property of the molten steel can be effectively reduced, and the molten steel is purified.
3. The converter adopts three-gear operation, so that the slag discharging amount of the converter is reduced, and the increase of inclusions caused by the entering of oxidizing slag into a ladle is prevented.
4. Aluminum behind the converter is controlled according to 0.050-0.070%, and good dynamic conditions during tapping are utilized when aluminum products react in a large quantity, so that Al is promoted 2 O 3 The impurity aggregation is removed by floating upwards, so that the feeding quantity of the aluminum wire of the LF furnace can be reduced, and even adjustment is not needed.
5. The aluminum content of the LF refining furnace is fed once to form Al in advance 2 O 3 The inclusion is removed in a floating way for a sufficient time, so that Al caused by later aluminum supplementing is avoided 2 O 3 Inclusions are difficult to remove, and Al in the slag 2 O 3 The content is favorable for absorbing the Al floating in the molten steel according to the similar compatibility principle 2 O 3 Inclusions.
6. The ferrosilicon is added once after S is less than or equal to 0.005 percent, and trace calcium in the ferrosilicon is mainly used for removing the Al which is not removed 2 O 3 The inclusion is denatured to become composite inclusion with low melting point, which is easy to be removed by collision growth in RH circulation process.
7. Carbon powder is added after RH is circulated and stabilized in high vacuum and can be fully mixed with molten steel, a small amount of slag covered by an RH vacuum tank and trace free oxygen in the molten steel are reacted by utilizing the strong reducibility of the carbon in high vacuum to produce CO bubbles, the CO bubbles can accelerate the collision growth and removal of inclusions in the molten steel circulation process, and the molten steel is purified;
content of each element in bearing steel
Note that: standard requirement Al is less than or equal to 0.050%, C:0.95% -1.05%;
mutual operation coefficient of activities of elements in bearing steel
The activity coefficients of C, al and O can be calculated to be lgf according to the content of each element and the activity mutual operation coefficient of each element in the bearing steel C =0.082，lgf Al =0.132，lgf o =-0.747；
2[Al]+3[O]=Al 2 O 3 (s) ∆G θ =-1225000+393.8T（J/mol）
[C]+[O]=CO(g) ∆G θ =-22200-38.34T（J/mol）
The entering temperature is generally 1560-1570 ℃ when entering the RH furnace, the exiting temperature is 1515-1525 ℃, the vacuum degree is measured and calculated according to 100Pa, and the vacuum degree is measured and calculated according to 1560 ℃ when entering the RH furnace;
∆G（Al 2 O 3 ）=-26575.3J/mol；∆G（CO）=-68516.8J/mol；
the outbound time was measured at 1515 ℃):
∆G（Al 2 O 3 ）=-55996.6J/mol；∆G（CO）=-67379.8J/mol；
therefore, in the temperature range of the RH refining process, the fatg (Al) is always present 2 O 3 ) G (CO); in actual production, the high vacuum degree is about 30-60Pa, and the aluminum in molten steel is about 0.015% -0.025%, so that the oxidation reaction of carbon is always far stronger than that of aluminum, and therefore, the reduction of C in vacuum is utilized to produce CO bubbles and accelerate the removal reaction of inclusions.
8. RH breaking and treating molten steel by using Ba element to treat residual Al in molten steel 2 O 3 Performing denaturation treatment, and removing Al by static blowing 2 O 3 Inclusions.
9. The weak acidity of the casting powder is utilized for adsorbing alkaline oxides in molten steel, the melting point of the casting powder is low, the casting powder has good melting effect and adsorptivity on the molten steel surface, and impurities can be effectively reduced from entering a casting blank.
10. Argon blowing of the stopper rod can reduce tiny Al 2 O 3 The inclusions are accumulated in the stopper rod to make the Al tiny 2 O 3 Uniformly enter molten steel, and Al with micro-size 2 O 3 The inclusions may also play an oxide metallurgical role.
The beneficial effects of adopting above-mentioned technical scheme to produce lie in: 1. the converter adopts the large bottom blowing high carbon drawing, can effectively reduce the initial oxygen content in the molten steel, adopts the pre-adding part of carburant to pre-deoxidize the molten steel, adopts the three-gear tapping operation, and can reduce the Al in the molten steel 2 O 3 Initial inclusion content; 2. al is added with 2 O 3 The generation time of the inclusions is advanced as much as possible, and the Al is prolonged 2 O 3 The removal time of the inclusions; 3. carrying out modification treatment on the residual fine inclusions; 4. the invention has simple process, strong operability and obvious effect, and solves the problems of Al 2 O 3 The problem of excessive inclusion can realize stable production of bearing steel produced by continuous casting; the method is simple in production operation, has small influence on the period, reduces the production cost, improves the benefit of enterprises, and has excellent popularization and application values in the industry.
When the high-carbon chromium bearing steel is produced by a billet continuous casting machine, the invention comprises the following steps of Al 2 O 3 The grade of the inclusion is stably controlled to be less than or equal to 0.5 grade, the grade of B is less than or equal to 1.5 grade, the qualified proportion reaches more than 99.9 percent, the product quality is effectively improved, and the stable and controlled production process is ensured.
Detailed Description
A control method of B-type inclusion in high-carbon chromium bearing steel is suitable for the production of high-carbon chromium bearing steel GCr15, and the composition requirements are as follows: 0.95 to 1.05 weight percent of C, 0.15 to 0.35 weight percent of Si, 0.25 to 0.45 weight percent of Mn, 1.40 to 1.65 weight percent of Cr, less than or equal to 0.020 weight percent of P, less than or equal to 0.015 weight percent of S, less than or equal to 0.0012 weight percent of O, less than or equal to 0.0015 weight percent of Ti and less than or equal to 0.00010 weight percent of Ca.
The technological parameters of the equipment are as follows: the converter is a 120t top-bottom combined blown converter, the loading amount is 155+/-2 t, and the molten steel amount is 145+/-2 t; the LF refining furnace is an electrode rotary double station; the RH refining furnace is double-station; the small billet continuous casting machine is an 8-machine 8-flow 200mm×200mm billet continuous casting machine, a tundish, the weight of molten steel corresponding to 350mm of the liquid level of the tundish is 20t, and the weight of molten steel corresponding to 700mm of the liquid level of the tundish is 39t (normal casting liquid level).
The control method of the B-type inclusion in the high-carbon chromium bearing steel comprises the working procedures of converter, LF refining, RH refining and continuous casting, and the working procedures are as follows:
(1) Converter process: the bottom blowing flow rate in the converting process adopts a middle-small-large bottom blowing mode, and the bottom blowing flow rate is 0.06-0.04-0.08 m 3 /(min x t). The tapping molten steel comprises the following components in percentage by mass: c: 0.08-0.20%, P is less than or equal to 0.015%, S is less than or equal to 0.015%, the temperature of molten steel tapping is 1620+/-20 ℃, tapping oxygen is less than or equal to 350ppm, and tapping time is 3.5-6.0 min. Adding into the steel ladle in the tapping process in sequence: carburant, aluminum particles, ferrosilicon, ferromanganese, residual carburant, low titanium ferrochromium and premelting slag, wherein when the adding time of the first carburant is 1/5 of tapping, the adding amount is 100+/-10 kg; the adding time of the aluminum particles is 10-20 s after the first carburant is added; the addition amount of the premelting slag is 6-9 kg/t steel, and the premelting slag comprises the following components in percentage by weight: caO 40-55%, siO 2 ≤10%、Al 2 O 3 30-45%, mgO less than or equal to 8% and Al 3-8%. Three-gear tapping is utilized in tapping processSteel ladle sample component C after tapping: 0.90 to 0.95 percent, si:0.05 to 0.10 percent, mn:0.22 to 0.30 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.015 percent, al:0.050 to 0.070%, cr:1.35 to 1.45 percent.
(2) LF refining procedure: adding 30-50 kg of silicon carbide in the early stage of LF refining, adding lime, fluorite and premelting slag for slagging, heating for 10-15 min, sampling, detecting, adjusting the contents of Mn, cr and Al according to the detection result, if Al is more than or equal to 0.040%, and if Al is less than 0.040%, feeding the molten steel into an aluminum wire at one time, wherein the feeding quantity is controlled according to the target content of Al in the molten steel by 0.050%; after S in molten steel in the middle and later stages of refining is less than or equal to 0.005%, adding ferrosilicon at one time to carry out alloying, and after the temperature of the molten steel and the components except the element C are qualified, carrying out static blowing for 5-10 min; al in refining slag component 2 O 3 The weight content is controlled between 28 and 35 percent.
(3) RH refining process: the vacuum degree is less than or equal to 100Pa, and the vacuum holding time is more than or equal to 15min; c content adjustment is carried out by adding carbon powder at one time after vacuum for 2min, vacuum is kept at 12min or more after adding carbon powder, and after breaking, a silicon barium wire is fed for 200-300 m, and molten steel is soft-blown for 15-30 min; the RH refining process does not add aluminum products into the molten steel; the RH refining process only carries out carbon content adjustment, and the rest elements are all adjusted in the LF refining process.
(4) Continuous casting process: the continuous casting adopts an argon blowing stopper rod and a submerged nozzle, when the liquid level of a tundish reaches 350mm after the pouring of a large ladle, 150-200 kg of special protection slag for bearing steel is added into the tundish, and the protection slag is added once and is not added any more later; and then adding a sufficient amount of covering agent to ensure that the liquid surface of the steel is not exposed, realizing 'black surface' pouring, and opening a stopper rod to blow argon after the pouring is successful, wherein the flow rate of blowing argon by the stopper rod is 0.5-0.8L/min.
The B-class inclusion B coarse in the high-carbon chromium bearing steel obtained by the method is less than or equal to 0.5 level, and the B fine is less than or equal to 1.5 level.
The technological parameters of the converter procedure of each embodiment are shown in table 1, and the steel ladle-like components after tapping in the converter procedure are shown in table 2; the process parameters of the LF refining procedure of each example are shown in Table 3; the process parameters of the RH refining and continuous casting procedures in each example and the detection data of B-type inclusions in the obtained high-carbon chromium bearing steel are shown in Table 4.
Table 1: technological parameters of the converter process
Table 2: ladle-like composition (wt%) after tapping in converter process
Table 3: technological parameters of LF refining procedure
Table 4: technological parameters of RH refining and continuous casting processes and detection data of B-type inclusions in bearing steel
。
Claims (7)
1. A control method of B-type inclusions in high-carbon chromium bearing steel is characterized by comprising the working procedures of converter, LF refining, RH refining and continuous casting;
(1) Converter process: the bottom blowing flow in the blowing process adopts a middle-small-large bottom blowing mode, and the tapped molten steel comprises the following components in percentage by mass: c:0.08 to 0.20 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.015 percent, the temperature of molten steel tapping is 1620+/-20 ℃, the tapping oxygen is less than or equal to 350ppm, and the tapping time is 3.5 to 6.0 minutes; adding into the steel ladle in the tapping process in sequence: carburant- & gt aluminum particles- & gt ferrosilicon- & gt ferromanganese- & gt residual carburant- & gt low titanium ferrochromium- & gt premelting slag, wherein three-gear tapping is utilized in the tapping process, and a ladle sample component C is obtained after tapping: 0.90 to 0.95 percent, si:0.05 to 0.10 percent, mn:0.22 to 0.30 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.015 percent, al:0.050 to 0.070%, cr:1.35 to 1.45 percent; when the adding time of the first carburant is 1/5 of tapping, the adding amount is 100+/-10 kg; the adding time of the aluminum particles is 10-20 s after the first carburant is added; the addition amount of the premelting slag is 6-9 kg/t steel;
(2) LF refining procedure: l (L)Adding 30-50 kg of silicon carbide in the earlier stage of F refining, adding lime, fluorite and premelting slag for slagging, heating for 10-15 min, sampling, detecting, adjusting the contents of Mn, cr and Al according to the detection result, if Al is more than or equal to 0.040%, and if Al is less than 0.040%, feeding the molten steel into an aluminum wire at one time, wherein the feeding quantity is controlled according to the target content of Al in the molten steel by 0.050%; after S in molten steel in the middle and later stages of refining is less than or equal to 0.005%, adding ferrosilicon at one time to carry out alloying, and after the temperature of the molten steel and the components except the element C are qualified, carrying out static blowing for 5-10 min; al in refining slag component 2 O 3 The weight content is controlled to be 28-35 percent;
(3) RH refining process: maintaining the vacuum below 100Pa for 2min, adding carbon powder at one time to adjust the C content, continuously maintaining the vacuum for more than or equal to 12min after adding the carbon powder, feeding a silicon-barium wire for 200-300 m after breaking the vacuum, and soft blowing molten steel for 15-30 min; the RH refining process does not add aluminum products into the molten steel;
(4) Continuous casting process: the continuous casting adopts an argon blowing stopper rod and a submerged nozzle, when the liquid level of a tundish reaches 350mm after the ladle is opened, 150-200 kg of special protection slag for bearing steel is put into the tundish, and then a sufficient amount of covering agent is added to ensure that the liquid level of the steel is not exposed, and the stopper rod is opened to blow argon after the casting is successful.
2. The method for controlling B-type inclusions in high-carbon chromium bearing steel according to claim 1, wherein the bottom blowing flow rate in the converter step is 0.06 to 0.04 to 0.08m in the bottom blowing mode of medium to small to large 3 /（min*t）。
3. The method for controlling B-type inclusions in high-carbon chromium bearing steel according to claim 2, wherein the converter process comprises the following components in percentage by weight: caO 40-55%, siO 2 ≤10%、Al 2 O 3 30～45%、MgO≤8%、Al 3～8%。
4. The method for controlling B-type inclusions in high-carbon chromium bearing steel according to claim 3, wherein the RH refining step is performed under vacuum of 100Pa or less and the vacuum holding time is 15min or more; the RH refining process only carries out carbon content adjustment, and the rest elements are all adjusted in the LF refining process.
5. The method for controlling B-type inclusions in high-carbon chromium bearing steel according to claim 4, wherein the casting process is one-time addition of the special mold flux for bearing steel, and no additional addition is performed in the subsequent step; the argon blowing flow of the stopper rod is 0.5-0.8L/min.
6. The method for controlling B-type inclusions in high carbon chromium bearing steel according to any one of claims 1 to 5, wherein the composition requirements of the high carbon chromium bearing steel are: 0.95 to 1.05 weight percent of C, 0.15 to 0.35 weight percent of Si, 0.25 to 0.45 weight percent of Mn, 1.40 to 1.65 weight percent of Cr, less than or equal to 0.020 weight percent of P, less than or equal to 0.015 weight percent of S, less than or equal to 0.0012 weight percent of O, less than or equal to 0.0015 weight percent of Ti and less than or equal to 0.00010 weight percent of Ca.
7. The method for controlling B-type inclusions in high-carbon chromium bearing steel according to claim 6, wherein B-type inclusions in the high-carbon chromium bearing steel obtained by the control method are less than or equal to 0.5 level and B-type inclusions are less than or equal to 1.5 level.
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