Smelting control method for Ti content and TiN type inclusions in high-purity bearing steel

Abstract

The invention relates to a smelting control method for Ti content and TiN inclusions in high-purity bearing steel. The method comprises the following steps: requirements on carbon, silicon, titanium and temperature in molten iron as a steelmaking raw material: requirements on carbon, silicon, titanium and temperature in molten steel as a refining raw material; molten steel deoxidation alloying treatment is conducted; alloy component fine adjustment and desulfurization are carried out; and conventionally carrying out molten steel vacuum treatment. According to the method, titanium oxide inclusions are generated in the refining process through the aluminum-titanium complex deoxidation reaction, SiO2 with the particle size being 0.05-0.25 micrometer is used for slagging, the content of titanium brought into the alloy is reduced while the inclusions in the steel are reduced, the alloy with modified inclusions does not need to be additionally added or repeated slagging-off does not need to be conducted, operation is convenient, and the cost is low. The titanium content in the steel after refining can be reduced to 0.0015 wt.% or below; and when the titanium content is 0.0013 wt.%, the number of TiN type inclusions in the steel is reduced by at least 38.0% compared with similar inclusions in the steel when the titanium content is 0.0027 wt.%, so that the TiN type inclusions in the steel are reduced from the source, the smelting quality of the GCr15 bearing steel is improved, and the tensile strength of the GCr15 bearing steel at 800 DEG C is improved by about 6.0%.

Description

Technical Field

[0001] The invention relates to a refining method for bearing steel, in particular to a preparation process for bearing steel with low titanium content, and more specifically to a method for controlling the titanium content and TiN inclusions in GCr15 bearing steel. Background Art

[0002] Bearings are a key component commonly used in mechanical equipment. GCr15 bearing steel is currently the most produced and widely used important raw material for manufacturing bearing rolling elements and rings. As the service conditions of bearings for high-end equipment such as high-speed railways and shield machines become increasingly stringent, high-end equipment bearings are required to have high contact fatigue life and rolling speed limits, which puts higher requirements on the cleanliness and uniformity of bearing steel.

[0003] The literature (Discussion on Quality Control of GCr15 Steel Production Process. China Metallurgy, 2009, 19(1):31-35) points out that when the oxygen content in bearing steel is controlled at 6×10 -4 wt% or less, large-sized inclusions such as TiN and Ti(C,N) become the main factors affecting the contact fatigue life of bearing steel. Among the inclusions of the same size, TiN inclusions rank first in terms of the degree of damage to the fatigue life of bearing steel. The harmful effect of nitride inclusions of 6 to 8 μm in steel on fatigue performance is equivalent to that of oxides with an average size of 25 μm, and this effect is aggravated as the size of inclusions increases (Effect of steel manufacturing processes on the quality of bearing steels. Philadelphia: ASTM, 1988: 149-186).

[0004] At present, due to the low removal efficiency of nitrogen in the refining process of bearing steel, there is no specific limit on the nitrogen content in the steel during the factory quality inspection of bearing steel products. The key to controlling TiN inclusions in steel is to accurately control the amount of titanium brought in by refining slag and alloy. Although the total oxygen content of GCr15 bearing steel smelted by advanced domestic and foreign companies using a long process has been reduced to 0.0003% to 0.0005%, and the sulfur content in the steel can be lower than 0.0020%, it is very difficult to stably control the titanium content in the steel to less than 0.0015%.

[0005] During the secondary refining process of bearing steel, the titanium element contained in the carburizer, SiC, alloy and refining slag enters the molten steel, causing titanium to combine with nitrogen and carbon in the steel to form TiN and Ti(C,N), or to generate oxynitrides or oxysulfurnitrides containing TiN with oxides, sulfides and oxysulfides as the core.

[0006] The applicant has found in the research that after the titanium content is reduced to about 0.0020%, large-sized TiN inclusions with a size of more than 10μm still exist in the steel; TiN composite inclusions are angular and easily become a source of stress concentration during the bearing load process. Effectively controlling the amount of titanium added during the refining process of bearing steel, and removing the titanium in the steel in the form of titanium oxide through refining slag, reducing the segregation and precipitation of TiN inclusions during the solidification of molten steel, and reducing the generation of TiN inclusions in steel from the source are the key to controlling TiN inclusions in bearing steel. At present, reducing the titanium content in steel with high efficiency and low cost, and reducing large-sized TiN inclusions in steel are technical bottlenecks in the production process of GCr15 bearing steel.

[0007] After searching:

[0008] The literature (Melting route effects on the rotatory bending fatigue and rolling contact fatigue properties of high carbon bearing steel SAE52100. International Journal of Fatigue, 2020, 140, 105854) reported the influence mechanism of various inclusions on fatigue life in bearing steel smelted by different process flows, and clearly pointed out that even if the oxygen content in the steel is controlled to 6×10 -4 wt%, the titanium content in the steel is controlled within 0.0015%, and TiN and Ti(C,N) inclusions in the steel can still be important factors affecting the fatigue strength and life of bearing steel. However, this document does not involve how to reduce the titanium content in the steel efficiently and at low cost to reduce the harm of TiN inclusions.

[0009] The document with Chinese patent publication number CN 106435093 B discloses "A refined slag for bearing steel production and its smelting process", which optimizes the refined slag composition and addition amount, and controls TiN inclusions by adding deoxidizer less and more frequently. Frequent addition of deoxidizer makes the operation process complicated and easily destroys the atmosphere of the smelting process, resulting in further oxygen and nitrogen addition to the molten steel, reducing the control effect of inclusions.

[0010] The document with Chinese patent publication number CN 108998720 B discloses "A method for preparing low-titanium bearing steel". Its main operation is to perform silicon alloying during steel tapping, and no Si-Fe alloy is added during LF refining, thereby reducing the amount of titanium added by the Si-Fe alloy during LF refining. In this method, silicon alloying during steel tapping is likely to cause large silicon burnout and increase smelting costs. This patent is particularly suitable for Si-Mn bearing steel for wind power steel balls with a silicon mass content of not less than 0.4%. The titanium content control requirement in the steel is lower than that of high-purity GCr15 bearing steel.

[0011] The document with Chinese patent application number 201811319185A discloses "Alloy process for inhibiting the formation of TiN composite inclusions in bearing steel by adding Ce", which provides a method of adding different contents of rare earth Ce to bearing steel to generate rare earth oxides (Ce2O3) or rare earth oxysulfides (Ce2O2S), reducing MgAl2O4 inclusions, and inhibiting the heterogeneous nucleation and precipitation of TiN on MgAl2O4 during solidification. However, this method increases the amount of rare earth alloy, and although it may reduce MgAl2O4 inclusions, it increases rare earth oxide or rare earth oxysulfide inclusions, and the effect of reducing TiN inclusions from the source is limited.

[0012] The document with Chinese patent application number 202111353575A discloses "A method for controlling the smelting of titanium nitride inclusions in high-carbon chromium bearing steel". It controls the TiO2 in the slag to enter the molten steel by slagging molten iron and molten steel, and adopts argon blowing throughout the process and adjusts the argon blowing amount to reduce the titanium content in the steel to 0.0010%~0.0015%, and the nitrogen content to 0.0027%~0.00031% to control TiN inclusions. However, it only mentions that the amount of Cr-Fe alloy and deoxidizer added in the steel-making process is controlled. The LF refining process relies on changing the amount of argon blowing and increasing the amount of slagging to increase the exposed area of ​​molten steel to reduce TiN inclusions, which is likely to lead to increased burnout of metal elements and increased smelting costs.

[0013] The document with Chinese patent application number CN 118222904 A discloses "A method for controlling TiN inclusions in bearing steel". The specific operation is to feed Si-□Mg alloy into the ladle after LF smelting and before VD refining to produce MgO and MgS as the nucleation core of TiN in the continuous casting process. The addition of Si-Mg alloy increases the smelting cost and increases the newly generated MgO and MgS inclusions, but does not reduce TiN inclusions from the source, and is aimed at bearing steel with a titanium content of more than 0.0020%.

[0014] The document with Chinese patent application number 2015104410847A discloses "A method for preparing refined slag for desulfurization of bearing steel", which mainly solves the problems of desulfurization of molten steel and large number of inclusions in traditional bearing steel production. The refined slag contains CaF2 which affects the environment. The document does not involve the control of titanium content in steel.

[0015] In summary, the above literature clarifies the hazards of TiN inclusions, explains the production process of low-titanium bearing steel and measures to reduce TiN inclusions in bearing steel, and has achieved certain results. Reducing the titanium content in the alloy or adding Si-Mg and rare earth Ce to modify inclusions has problems such as high operating costs, poor adaptability, and limited effect on reducing TiN inclusions. In addition, the literature does not propose measures to control the titanium content in the refining process according to different raw material conditions, such as the titanium content in molten iron and the carbon content in molten steel, and the operating method is not flexible enough.

[0016] TiN inclusions in GCr15 bearing steel are mainly single TiN or composite TiN inclusions with oxides, oxysulfides and sulfides as the core, which are precipitated during the solidification of molten steel. Under the current smelting process conditions commonly used in GCr15 bearing steel, the key to reducing TiN inclusions is to reduce the titanium content in steel. Since the use of low-titanium alloys and the increase in the amount of slag removal during the smelting process increase the cost of steelmaking, it is necessary to develop flexible and efficient titanium removal technology without increasing the cost of steelmaking, so as to reduce the probability of TiN inclusions from the source, reduce the harm of TiN inclusions in GCr15 bearing steel and improve its fatigue life. Summary of the invention

[0017] The purpose of the present invention is to flexibly adjust the amount of deoxidizer according to the titanium content in the steelmaking raw material combined with the carbon and silicon content in the molten steel, and provide a method for generating titanium oxide inclusions during the refining process by utilizing the aluminum-titanium composite deoxidation reaction, and adding SiO2 with a particle size of 0.05-0.25μm in the refined slag to participate in slag making, and by providing an oxygen source at the slag-steel interface, oxidizing the titanium element brought into the alloy to reduce the amount of titanium added in the alloy, without the need to add an alloy modified by inclusions or repeatedly slagging, which is not only convenient to operate, but also can reduce the titanium content in the steel to below 0.0015wt.% after the refining is completed; when the titanium content is 0.0013wt.%, the number of TiN inclusions in the steel is reduced by at least 38% compared with the same inclusions in the steel with a titanium content of 0.0027wt.%, thereby reducing the Ti content and TiN inclusions in high-purity bearing steel from the source.

[0018] Measures to achieve the above objectives:

[0019] A method for smelting and controlling Ti content and TiN inclusions in high-purity bearing steel, the steps of which are as follows:

[0020] 1) Requirements for carbon, silicon, titanium and temperature in molten iron, the raw material for steelmaking: The sum of the mass percentages of carbon and silicon is (C Fe +Si Fe ) is controlled at 4.22-4.96wt.%, the molten iron temperature is controlled at 1260-1400°C, the mass percentage content of titanium Ti Fe According to the following formula (1), the content of 0.0445wt.% to 0.1200wt.% is controlled;

[0021] Ti Fe =-3.2828+1.3725×(C Fe +Si Fe )-0.1384×(C Fe +Si Fe ) 2 (1)

[0022] Where:

[0023] Ti Fe — is the mass percentage content of titanium measured in the molten iron entering the steelmaking furnace, unit: wt.%;

[0024] C Fe — is the mass percentage of carbon measured in the molten iron entering the steelmaking furnace, unit: wt.%;

[0025] Si Fe — is the mass percentage content of silicon measured in the molten iron entering the steelmaking furnace, unit: wt.%;

[0026] 2) Requirements for carbon, silicon, titanium and temperature in the refined raw material molten steel: After the molten iron composition and temperature meet the requirements in 1), decarburization treatment is carried out by conventional steelmaking methods, and the molten steel temperature is controlled to be not less than 1600℃. The mass percentage of carbon in the molten steel is C ST Not more than 0.460wt.%, mass percentage content of silicon Si ST Not less than 0.020wt.%, titanium content by mass ST Not more than 0.0005wt.%;

[0027] 3) Deoxidation and alloying treatment of molten steel

[0028] When the composition and temperature of the molten steel reach the requirements in step 2), Al-Fe alloy is added at 1.45-2.25 kg / t steel for deoxidation; the dissolved oxygen content in the molten steel is removed. DO It is based on the C content of molten steel at the beginning of refining. ST , and then calculate the amount of deoxidizer Al-Fe alloy added to the steel DO, the dissolved oxygen content removed from the steel is O DO The dissolved oxygen content in the steel is controlled according to the following formula (2): SO Controlled to no more than 0.0013wt%, acid-soluble aluminum Al s Mass percentage

[0029] The content is not less than 0.024wt.%;

[0030] O DO =0.1102-1.1836×Al-Fe DO +3.5360×(Al-Fe DO ) 2 (2)

[0031] Where:

[0032] O DO — is the dissolved oxygen content in the molten steel after deoxidation, unit: wt.%;

[0033] Al-Fe DO — is the amount of Al-Fe alloy added during deoxidation, unit: kg / t steel;

[0034] After deoxidation, carburizer, silicon, chromium and manganese alloy elements are added in sequence according to the conventional method for alloying treatment: after alloying, refined slag is added immediately. In addition to the conventional addition of quicklime to make slag, 0.05-0.10kg / t

[0035] SiO2 with a particle size of 0.05-0.25 μm is added to the steel, and the basicity of the initial refined slag is controlled to be not less than 10.0, and the TiO2 content in the refined slag is not higher than 0.10wt.%;

[0036] During the deoxidation alloying process, the titanium addition ΔTi AL Control is performed according to the following formula (3):

[0037] ΔTi AL =0.00139-0.00361×(ΔC AL +ΔSi AL )+0.00369×(ΔC AL +ΔSi AL ) 2 (3)

[0038] Where:

[0039] ΔTi AL —Ti is the mass percentage content of titanium in molten steel after deoxidation and alloying AL The mass percentage content of titanium Ti in the molten steel at the beginning of deoxidation STThe difference between the two is the increase in titanium during the deoxidation alloying process, unit: wt.%;

[0040] ΔC AL — is the mass percentage content of carbon C measured in molten steel after deoxidation and alloying AL The mass percentage of carbon C measured in the molten steel at the beginning of deoxidation ST The difference between the two is the amount of carbon added during the deoxidation alloying process, unit: wt.%;

[0041] ΔSi AL — is the mass percentage content Si of silicon in molten steel after deoxidation and alloying AL The mass percentage of silicon Si in the molten steel at the beginning of deoxidation ST The difference between the two is the amount of silicon added during the deoxidation alloying process, unit: wt.%; it should be noted that the temperature of the molten steel should be kept not lower than 1500℃ during the deoxidation alloying process. After the deoxidation alloying process, the amount of titanium added in the molten steel is AL Not more than 0.0008wt.%;

[0042] 4) Fine-tune the alloy composition of molten steel and desulfurize

[0043] 15 minutes after the deoxidation alloying and the addition of refined slag, add aluminum for deoxidation at a rate of 0.40-1.65 kg / t steel; add carburizer, SiC and silicon, chromium and manganese alloy elements according to the conventional method to fine-tune the composition;

[0044] When adding desulfurized slag by conventional methods, SiO2 with a particle size of 0.05-0.25 μm is added at 0.10-0.15 kg / t steel, and the basicity of the initial desulfurized slag is controlled to be not less than 8.0, and the TiO2 content in the slag is not higher than 0.10 wt.%;

[0045] Composition fine-tuning and titanium addition ΔTi in molten steel after desulfurization DS Controlled by the following formula (4); Controlled refining temperature not less than 1550℃; Fine adjustment of composition and titanium addition ΔTi in molten steel after desulfurization DS Controlled to no more than 0.0005wt%, acid soluble

[0046] Aluminum s The content of is not less than 0.010wt.% and the content of sulfur is not more than 0.0020wt.%;

[0047] ΔTi DS =-0.00431+0.01253×(C AL +Si AL +Al DO-DS )-0.00766×(C AL +Si AL+Al DO-DS ) 2 (4)

[0048] Where:

[0049] ΔTi DS —Ti is the mass percentage content of titanium measured in molten steel after fine-tuning the composition and desulfurization DS Alloying with deoxidation

[0050] After the end of Ti AL The difference between the two is the amount of titanium added after the alloy composition is fine-tuned and desulfurization is completed, unit: wt.%;

[0051] C AL — is the mass percentage of carbon measured in molten steel after deoxidation and alloying, unit: wt.%;

[0052] Si AL — is the mass percentage content of silicon measured in molten steel after deoxidation and alloying, unit: wt.%;

[0053] Al DO-DS — is the amount of deoxidizer aluminum added when fine-tuning the alloy composition, unit: kg / t steel;

[0054] 5) Conventionally carry out molten steel vacuum treatment. At the end, the components and mass percentages in the steel are as follows: C:

[0055] 0.96wt.%~1.05wt.%, Si: 0.28wt.%~0.32wt.%, Al s： 0.010wt.%~0.034wt.%, Cr:

[0056] 1.45wt.%~1.51wt.%, Mn: 0.36wt.%~0.40wt.%, S: ≤0.0020wt.%, Ti: ≤0.0015

[0057] wt.%, T.[O]: ≤0.0005wt.%, N: ≤0.0050wt.%, Ca: ≤0.0003wt.%;

[0058] 6) After the vacuum treatment, the steel ingots and subsequent processes are cast under argon protection.

[0059] Further: Al s The mass percentage content is: 0.010wt.%~0.028wt.%.

[0060] Furthermore: the Ti mass percentage content is ≤0.0014wt.%.

[0061] Furthermore: the S mass percentage content is ≤0.0015wt.%.

[0062] Furthermore: the N mass percentage content is ≤0.0040wt.%.

[0063] Mechanisms and functions of the main elements and processes in the present invention

[0064] The present invention controls the sum of the mass percentages of carbon and silicon in the molten iron (C Fe +Si Fe ) is 4.22-4.96wt.%, the molten iron temperature is 1260-1400°C, the mass percentage content of titanium Ti Fe According to formula (1), the content of titanium is controlled within 0.0445wt.% to 0.1200wt.%. This is because the raw material iron for steelmaking usually contains titanium content far exceeding the control requirement of GCr15 bearing steel. Titanium is removed together with carbon during the steelmaking process. Fe +Si Fe ), molten iron temperature, molten iron Ti Fe To formulate a specific decarburization process to achieve stable decarburization and detitanium effects and reduce the burn-out of the alloy element silicon.

[0065] The present invention controls the carbon content C in the molten steel during steel tapping. ST Not more than 0.460wt.%, silicon content Si ST Not less than 0.020wt.%, the molten steel temperature is not less than 1600℃, and the titanium content in the steel is reduced to no more than 0.0005wt.%. This is because when the carbon content in the molten steel is higher than 0.460wt.%, the oxygen supply in the molten steel is less, the oxidation removal amount of phosphorus and titanium in the steel is reduced, and the requirements of steelmaking dephosphorization and detitanium are not met; when the silicon content is lower than 0.020wt.%, the molten steel is overoxidized, the alloy element silicon is burned out, and the subsequent amount of Si-Fe alloy is large; when the titanium content in the molten steel is higher than 0.0005wt.%, the difficulty of controlling the titanium content in the deoxidation and alloying process increases, and the cost increases. When the molten steel temperature is lower than 1600℃, the heat loss carried by the molten steel itself is large, and the energy consumption of the deoxidation, alloying and desulfurization processes is high.

[0066] The present invention is to add the deoxidizer Al-Fe alloy to the molten steel to increase the amount of Al-Fe DO Control the amount of deoxidation in molten steel DO , deoxidation amount in molten steel O DO According to formula (2), aluminum deoxidation is added at 1.45-2.25 kg / t steel, and the final mass percentage of dissolved oxygen in the molten steel is O SO Controlled to no more than 0.0013wt%, acid-soluble aluminum Al sThe mass percentage content is not less than 0.024wt.%, because the oxygen decarburization during steelmaking causes a certain amount of dissolved oxygen in the steel. In order to ensure the utilization rate of subsequent alloying elements and the effect of refining and desulfurization, Al-Fe needs to be added according to the oxygen content in the molten steel. DO To reduce the dissolved oxygen content in the steel, improve the utilization rate and desulfurization effect of the alloy, and reduce the titanium content brought into the alloy. At the same time, the titanium in the alloy is used to participate in the deoxidation process of the refining process and react with the acid-soluble aluminum Al in the deoxidizer. s The Al2O3-Ti3O5-TiO2 composite inclusions are removed during the reaction. Since the composite aluminum-titanium oxide inclusions are not easy to reduce, the titanium content in the steel is reduced. SO When the content exceeds 0.0013%, more deoxidizer needs to be added for deoxidation, which not only increases the amount of deoxidizer, thereby producing more alumina inclusions, but also increases the amount of alloy due to the reduction in alloy utilization, which increases the amount of titanium brought into the alloy and the subsequent refining load. s When the content is lower than 0.024wt.%, the necessary deoxidation effect cannot be achieved and the utilization rate of alloying elements is low. When the deoxidizer exceeds 2.25kg / t steel, it is easy to oxidize and produce Al2O3 inclusions.

[0067] The present invention controls the alloying treatment immediately after the deoxidation is completed. In addition to controlling the amount of deoxidizer added in the molten steel, the titanium amount ΔTi is increased. AL After control according to formula (3), the titanium addition amount ΔTi in the molten steel AL Controlled to no more than 0.0008wt%: This is because when the mass percentage content of carbon and silicon in molten steel is high, under the condition of a certain mass percentage content of carbon and silicon in the finished steel, the amount of carburizer and Si-Fe alloy added during the refining process is small, and the titanium brought into the alloy is reduced. By controlling the amount of titanium added during the refining process to no more than 0.0008wt.%, the difficulty of controlling the amount of titanium added in the subsequent process can be reduced, and the amount of titanium added in the molten steel can be reduced from the source, thereby reducing the amount of TiN inclusions generated during the solidification of the molten steel.

[0068] The invention controls the addition of refined slag immediately after alloying is completed. In addition to the conventional addition of quicklime to make slag, SiO2 with a particle size of 0.05 to 0.25 μm is added to the refined slag according to 0.05 to 0.10 kg / t steel, and the initial refined slag basicity is controlled to be not less than 10.0 according to the conventional method, and the TiO2 content in the initial refined slag is not higher than 0.10 wt.%; the addition of refined slag during the deoxidation alloying process is mainly to absorb the deoxidation products Al2O3, SiO2, etc. and partially desulfurize. In order to obtain a better inclusion removal effect, the basicity of the refined slag is required to be not less than 10.0. The SiO2 with a particle size of 0.05 to 0.25 μm is added because it is a component in the refined slag, but does not contain metal titanium and titanium oxides, and has a fine particle size, a large specific surface area, and good reaction activity. In the present invention, after deoxidation and alloying, it is used together with quicklime to participate in slag making, and can provide an oxygen source for the oxidation removal of titanium at the slag-steel interface and absorb inclusions at the slag-steel interface without increasing the oxygen absorption of molten steel, and utilizes the TiO generated by the reaction of SiO2 with titanium at the slag-steel interface to generate x , directly absorbed by the refined slag or absorbed by the refined slag after being combined with the deoxidation product Al2O3. The active SiO2 at the slag-steel interface can increase the content of alloy element silicon in the molten steel after being reduced by the titanium in the alloy, thereby improving the utilization rate of ferrosilicon alloy and reducing the titanium content brought in by the alloy and refined slag. The SiO2 with a particle size of 0.05-0.25μm in the refined slag is less than 0.05kg / t steel, which has no effect of slag formation and providing an oxygen source for the slag-steel interface. If the amount of SiO2 with a particle size of 0.05-0.25μm added exceeds 0.10kg / t steel, the slag basicity will be reduced, affecting the absorption of deoxidation products in the steel. When the TiO2 content in the initial refined slag is not higher than 0.10wt.%, since less TiO2 is reduced by alloy and deoxidizer in the refined slag, the amount of titanium added to the molten steel can be reduced from the source, and the amount of TiN inclusions generated during the solidification of the molten steel can be reduced. The SiO2 with a particle size of 0.05 to 0.25μm is used to reuse metallurgical solid waste resources, reducing the cost of the smelting process.

[0069] The present invention controls the addition of aluminum deoxidation at 0.40-1.65 kg / t steel 15 minutes after the deoxidation alloying and refining slag addition, and adds carburizer, SiC and chromium and manganese alloy elements according to the conventional method to fine-tune the composition, so as to control the acid-soluble aluminum Al in the steel. s The content is not less than 0.010wt.%, because there is a certain degree of oxygenation in the process of deoxidation alloying and adding desulfurized refining slag. In order to ensure the alloying and desulfurization effect of carbon, silicon, manganese and chromium in steel, it is necessary to add aluminum deoxidation during the refining process. The deoxidizer is added less than 0.40kg / t steel. The acid-soluble aluminum Al in the steel sWhen the content is lower than 0.010wt.%, the necessary deoxidation effect cannot be achieved. When the deoxidizer exceeds 1.65kg / t steel, the oxidation of the deoxidizer is aggravated and Al2O3 inclusions are easily generated. The addition of carburizer, SiC and chromium and manganese alloy elements to fine-tune the composition is because the addition of alloying elements does not meet the control requirements of finished steel.

[0070] The reason why the present invention controls the addition of SiO2 with a particle size of 0.05-0.25 μm at 0.10-0.15 kg / t of steel when adding desulfurization slag by the conventional method, and controls the basicity of the desulfurization slag to be not less than 8.0 and the sulfur content to be not higher than 0.0020 wt.% is that desulfurization requires thermodynamic conditions of high basicity. In order to obtain a better desulfurization effect, the basicity of the desulfurization slag is not less than 8.0. Adding an appropriate amount of SiO2 with a particle size of 0.05 to 0.25 μm not only participates in slag formation, but also provides an oxygen source at the slag-steel interface. When the oxidation component is fine-tuned, the titanium brought into the carburizer, SiC and alloy, and the silicon powder in the desulfurized slag is less than 0.10 kg / t steel, which cannot achieve the effect of slag formation and providing an oxygen source at the slag-steel interface. The addition of SiO2 with a particle size of 0.05 to 0.25 μm exceeds 0.15 kg / t steel, resulting in a decrease in slag basicity and affecting the desulfurization effect. When the sulfur content is higher than 0.0020 wt.%, the sulfide inclusions in the steel increase. When the TiO2 content in the desulfurized slag is not higher than 0.10 wt.%, since there is less TiO2 in the slag reduced by the alloy and deoxidizer, the amount of titanium added to the molten steel can also be reduced from the source, and the amount of TiN inclusions generated during the solidification of the molten steel can be reduced.

[0071] The invention controls the composition fine-tuning and titanium addition amount ΔTi of molten steel after desulfurization. DS Controlled by formula (4); the refining temperature is controlled not less than 1550℃, because high temperature is conducive to desulfurization. The carbon and silicon content in the molten steel after deoxidation and alloying affects the amount of titanium introduced into the alloy. The amount of deoxidizer aluminum added affects the alloy yield and the amount of titanium removed by oxidation. The amount of titanium added in the molten steel after fine-tuning the composition and desulfurization is ΔTi. DS The purpose of controlling the content to no more than 0.0005wt% is to reduce the amount of titanium added to the molten steel from the source of refined raw materials and reduce the amount of TiN inclusions generated during the solidification of the molten steel.

[0072] The reason why the present invention controls the titanium content in the steel to Ti≤0.0015% after the molten steel is vacuum treated is that when the titanium content exceeds 0.0015%, large-sized TiN inclusions in the steel increase, affecting the uniformity of the steel structure and the fatigue life.

[0073] The total oxygen content T.[O] is controlled to be ≤0.0005% because when the total oxygen content T.[O] in steel exceeds 0.0005%, large-sized oxides such as alumina and aluminum-magnesium spinel or TiN inclusions composed of oxygen, sulfur and nitrogen will increase in the steel, affecting the uniformity of the steel's structure and fatigue life.

[0074] The nitrogen content in steel is controlled at N≤0.0050% because when the nitrogen content exceeds 0.0050%, large-sized TiN inclusions in the steel increase, affecting the uniformity of the steel structure and fatigue life.

[0075] Controlling Acid-soluble Aluminum in Steel s The content is 0.010~0.034%, which is due to acid-soluble aluminum Al s When the content is lower than 0.010wt.%, the oxygen in the steel is not fully removed, affecting the alloying and desulfurization effects. When it exceeds 0.034wt.%, the oxide inclusions in the steel increase, and the amount of alumina, aluminum-magnesium spinel and oxysulfur nitrides increases.

[0076] Compared with the prior art, the present invention utilizes Al-Ti composite deoxidation reaction to generate titanium oxide inclusions during the refining process, utilizes SiO2 with a particle size of 0.05 to 0.25 μm to participate in slag formation, reduces the titanium content in the steel while reducing the titanium content brought into the alloy, and does not require the addition of an alloy to modify the inclusions or repeated slagging, which is not only convenient to operate, but also allows the titanium content in the steel to be reduced to below 0.0015 wt.% after the refining is completed; when the titanium content is 0.0013 wt.%, the number of TiN inclusions in the steel is reduced by at least 38% compared with the same inclusions in the steel with a titanium content of 0.0027 wt.%, thereby reducing the TiN inclusions in the steel from the source, thereby improving and improving the smelting quality of GCr15 bearing steel, and further increasing the tensile strength of GCr15 bearing steel at 800°C by about 6.0%. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 is a SEM image of MnS-TiN type inclusions detected in the steel after being treated in the embodiment;

[0078] Figure 2 This is a SEM image of MnS-TiN inclusions detected in steel after treatment using the prior art;

[0079] Figure 3 is a SEM image of oxide-MnS-TiN inclusions detected in the steel after being treated in the embodiment;

[0080] Figure 4 This is a SEM image of oxide-MnS-TiN inclusions detected in steel after being treated using the prior art. DETAILED DESCRIPTION

[0081] The present invention is described in detail below:

[0082] Example 1

[0083] The bearing steel smelted in this embodiment is GCr15;

[0084] A method for smelting and controlling titanium content and TiN inclusions in high-purity bearing steel, the steps of which are as follows:

[0085] 1) Requirements for carbon, silicon, titanium and temperature in molten iron, the raw material for steelmaking: The sum of the mass percentages of carbon and silicon is (C Fe +Si Fe ) is controlled at 4.22wt.% and the molten iron temperature is at 1327℃; Fe +Si Fe )=4.22wt.%Substitute into formula (1) to calculate the mass percentage content of titanium in molten iron Ti Fe 0.0445wt.%;

[0086] Ti Fe =-3.2828+1.3725×(C Fe +Si Fe )-0.1384×(C Fe +Si Fe ) 2 (1)

[0087] Where: The mass percentage of carbon measured in the molten iron entering the steelmaking furnace C Fe 4.00wt.%; the mass percentage content of silicon Si in the molten iron entering the steelmaking furnace Fe 0.220wt.%;

[0088] 2) Requirements for carbon, silicon, titanium and temperature in molten steel

[0089] Decarburize molten iron according to conventional methods and control the carbon content C in molten steel after decarburization ST At 0.171wt.%, silicon content Si ST At 0.070wt.%, the molten steel temperature is 1632℃; the mass percentage content of titanium in the molten steel is measured. ST 0.0002

[0090] wt.%:

[0091] 3) Deoxidation and alloying treatment of molten steel

[0092] When the composition and temperature of the molten steel reach the requirements in 2), add Al-Fe alloy at 1.716 kg / t steel for deoxidation;

[0093] Final dissolved oxygen removal in molten steel DO According to the following formula (2), by adding Al-Fe DO Quantity control will be based on Al-Fe DOAfter removing 0.0112wt.% of dissolved oxygen content, the dissolved oxygen content in molten steel can be reduced to O SO Controlled at 0.0013wt%;

[0094] O DO =0.1102-1.1836×Al-Fe DO +3.5360×(Al-Fe DO ) 2 (2)

[0095] Where:

[0096] Al-Fe DO The amount of deoxidizer Al-Fe alloy added at the end of steelmaking is based on the C content in the molten steel. ST The amount of addition is calculated by the general calculation method to calculate the Al-Fe DO =1.716kg / t steel;

[0097] After deoxidation, alloying treatment is carried out immediately, that is, adding carburizer, silicon, manganese, and chromium alloy elements according to the conventional method for alloying treatment:

[0098] In addition to the conventional addition of quicklime to make slag, SiO2 with a particle size of 0.05-0.25 μm was added to the refined slag at a rate of 0.092 kg / t steel; the basicity of the initial refined slag was 10.9; in the molten steel, in addition to controlling the amount of deoxidizer added, the titanium addition amount ΔTi AL Control is performed according to the following formula (3):

[0099] ΔTi AL =0.00139-0.00361×(ΔC AL +ΔSi AL )+0.00369×(ΔC AL +ΔSi AL ) 2 (3)

[0100] After testing, the carbon content C in the molten steel after deoxidation and alloying AL The carbon content C in the molten steel measured after steelmaking is 0.761wt.% ST The silicon content Si in the molten steel after deoxidation and alloying is 0.171wt.% AL The silicon content Si in molten steel at the end of steelmaking is 0.130wt.% ST is 0.070wt.%, then ΔC AL =C AL -C ST =0.761wt.%-0.171wt.%=

[0101] 0.590wt.%ΔSi AL =Si AL -Si ST =0.130wt.%-0.070wt.%=0.060wt.%;

[0102] ΔC b-AL and ΔSi b-AL The calculated value of is calculated by formula (3): ΔTi AL =0.00060wt.%;

[0103] Where: The increase in titanium during deoxidation alloying process ΔTi AL The increase in carbon content is 0.00060wt.%, and the increase in carbon content is ΔC AL The increase in silicon content is 0.590wt.%, ΔSi AL 0.060wt.%;

[0104] It should be noted that the temperature of the molten steel should be kept not lower than 1500℃ during the deoxidation and alloying process. After the deoxidation and alloying process, the titanium content Ti in the molten steel is calculated. AL 0.00080wt.%; the titanium content Ti in the molten steel was detected AL 0.0008

[0105] wt%Acid soluble aluminum Al s The content is 0.024wt.%;

[0106] 4) Fine-tune alloy composition and desulfurize

[0107] 15 minutes after the deoxidation and alloying, aluminum deoxidation is added at 1.496 kg / t steel; carburizer, SiC, chromium and manganese alloy elements are conventionally added to fine-tune the composition; when adding desulfurized slag by conventional methods, SiO2 with a particle size of 0.05-0.25 μm is added at 0.14 kg / t steel, and the initial desulfurized slag basicity is controlled to 9.7, and the TiO2 content in the slag is 0.09

[0108] wt.%; titanium addition ΔTi after composition fine-tuning and desulfurization DS Controlled by the following formula (4);

[0109] After testing, the carbon content C in the ladle after deoxidation and alloying AL The silicon content Si in the molten steel measured after deoxidation and alloying is 0.761wt.% AL The amount of deoxidizer aluminum added at the beginning of desulfurization is 0.160wt.%. DO-DS for

[0110] 1.495kg / t steel, then the measured C AL、 SiAL and Al DO-DS Substitute each value into the following formula (4) to calculate:

[0111] ΔTi DS =-0.00431+0.01253×(C AL +Si AL +Al DO-DS )-0.00766×(C AL +Si AL +Al DO-DS ) 2 (4)

[0112] After calculation, we get: ΔTi DS =0.00043wt.%;

[0113] Where: The titanium addition amount of molten steel after fine-tuning the composition and desulfurization is ΔTi DS Controlled to 0.00043wt.%; the carbon content C in the steel measured after deoxidation and alloying AL 0.761wt.%; the silicon content Si in the steel measured after deoxidation and alloying AL The amount of deoxidizer aluminum added when fine-tuning the alloy composition is 0.130wt.% DO-DS 1.495kg / t steel;

[0114] The temperature is controlled at 1566℃ during the composition fine-tuning and desulfurization process; after the composition fine-tuning and desulfurization are completed, the titanium content Ti in the molten steel is calculated. DS 0.00123wt.%; the titanium content Ti in the molten steel was detected DS 0.0014wt%, acid soluble aluminum Al s The content is 0.014wt.%, the sulfur content is 0.0016wt.%;

[0115] 5) The molten steel is vacuum treated routinely. At the end, the components and mass percentages in the steel are as follows: C: 0.956wt.%,

[0116] Si: 0.280wt.%Al s： 0.012wt.%, Cr: 1.46wt.%, Mn: 0.38wt.%, S: 0.0018wt.%, Ti:

[0117] 0.0013wt.%, T.[O]: 0.0004wt.%, N: 0.0030wt.%, Ca: 0.0002wt.%;

[0118] 6) After the vacuum treatment, the steel ingots and subsequent processes are cast under argon protection.

[0119] After testing, it was found that the number of TiN inclusions in the steel with a titanium content of 0.0013wt.% in this embodiment was reduced by 38.8% compared with the number of similar inclusions in the steel with a titanium content of 0.0027wt.%, thereby reducing the TiN inclusions in the steel from the source and improving the smelting quality of the steel. As a result, fatigue cracks caused by non-deformed TiN inclusions during processing and use of GCr15 bearing steel were reduced, thereby increasing the tensile strength of GCr15 bearing steel at 800°C by 6.8%.

[0120] Example 2

[0121] The bearing steel smelted in this embodiment is GCr15;

[0122] A method for smelting and controlling titanium content and TiN inclusions in high-purity bearing steel, the steps of which are as follows:

[0123] 1) Requirements for carbon, silicon, titanium and temperature in molten iron, the raw material for steelmaking: The sum of the mass percentages of carbon and silicon is (C Fe +Si Fe ) is controlled at 4.27wt.%, and the molten iron temperature is at 1281℃; Fe +Si Fe )=4.27wt.%Substitute into formula (1) to calculate the mass percentage content of titanium in molten iron Ti Fe 0.0547wt.%;

[0124] Ti Fe =-3.2828+1.3725×(C Fe +Si Fe )-0.1384×(C Fe +Si Fe ) 2 (1)

[0125] Where: The mass percentage of carbon in the molten iron entering the steelmaking furnace C Fe 3.99wt.%; The mass percentage content of silicon in the molten iron entering the steelmaking furnace is Si Fe 0.282wt.%;

[0126] 2) Requirements for carbon, silicon, titanium and temperature in molten steel as raw material for refining:

[0127] Decarburize molten iron according to conventional methods and control the carbon content C in molten steel after decarburization ST At 0.216wt.%, silicon content Si ST At 0.030wt.%, the molten steel temperature is 1625℃; the mass percentage content of titanium in the molten steel is measured. ST 0.0003

[0128] wt.%:

[0129] 3) Deoxidation and alloying treatment of molten steel

[0130] When the composition and temperature of the molten steel reach the requirements in 2), add Al-Fe alloy at 1.481 kg / t steel for deoxidation;

[0131] Final dissolved oxygen removal in molten steel DO According to the following formula (2), by adding Al-Fe DO Quantity control will be based on Al-Fe DO After removing 0.0125wt.% of dissolved oxygen content, the dissolved oxygen content in molten steel can be reduced to O SO control

[0132] At 0.0005wt%;

[0133] O DO =0.1102-1.1836×Al-Fe DO +3.5360×(Al-Fe DO ) 2 (2)

[0134] Where:

[0135] Al-Fe DO The amount of deoxidizer Al-Fe alloy added at the end of steelmaking is based on the C content in the molten steel. ST The amount of addition is calculated by the general calculation method to calculate the Al-Fe DO =1.481kg / t steel;

[0136] After deoxidation, alloying treatment is carried out immediately, that is, adding carburizer, silicon, manganese, and chromium alloy elements according to the conventional method for alloying treatment:

[0137] In addition to the conventional addition of quicklime to make slag, SiO2 with a particle size of 0.05-0.25 μm was added to the refined slag at a rate of 0.062 kg / t steel; the basicity of the initial refined slag was 10.9; in the molten steel, in addition to controlling the amount of deoxidizer added, the titanium addition amount ΔTi AL according to

[0138] The following formula (3) is used for control:

[0139] ΔTi AL =0.00139-0.00361×(ΔC AL +ΔSi AL )+0.00369×(ΔC AL +ΔSi AL ) 2 (3)

[0140] After testing, the carbon content C in the molten steel after deoxidation and alloying AL The carbon content C in the molten steel measured after steelmaking is 0.845wt.% ST The silicon content Si in the molten steel after deoxidation and alloying is 0.216wt.% AL 0.150wt.% Si content in molten steel at the end of steelmaking ST is 0.030wt.%, then ΔC AL =C AL -C ST =0.845wt.%-0.216wt.%=0.629

[0141] wt.%,ΔSi AL =Si AL -Si ST =0.150wt.%-0.030wt.%=0.120wt.%;

[0142] ΔC b-AL and ΔSi b-AL The calculated value is calculated by formula (3): ΔTi AL =0.00076wt.%;

[0143] Where: The increase in titanium during deoxidation alloying process ΔTi AL The increase in carbon content is 0.00076wt.%, and the increase in carbon content is ΔC AL 0.629

[0144] wt.%, silicon increase ΔSi AL 0.120wt.%;

[0145] It should be noted that the temperature of the molten steel should be kept not lower than 1500℃ during the deoxidation and alloying process. After the deoxidation and alloying process, the titanium content Ti in the molten steel is calculated. AL The actual detection results show that the titanium content in molten steel is 0.00106wt.%; AL Control

[0146] 0.0011wt% Acid soluble aluminum Al s The content is 0.065wt.%;

[0147] 4) Fine-tune alloy composition and desulfurize

[0148] 15 minutes after the deoxidation and alloying, aluminum deoxidation is added at 0.413kg / t steel; carburizer, SiC, chromium and manganese alloy elements are conventionally added to fine-tune the composition; when adding desulfurized slag by conventional methods, SiO2 with a particle size of 0.05-0.25μm is added at 0.11kg / t steel, and the initial desulfurized slag basicity is controlled to 8.5, and the TiO2 content in the slag is 0.09

[0149] wt.%; titanium addition ΔTi after composition fine-tuning and desulfurization DS Controlled by the following formula (4);

[0150] After testing, the carbon content C in the ladle after deoxidation and alloying AL The silicon content Si in the molten steel after deoxidation and alloying is 0.845wt.% AL 0.150wt.% The amount of deoxidizer Al added at the beginning of desulfurization DO-DS for

[0151] 0.413kg / t steel, then the measured C AL、 Si AL and Al DO-DS Substitute each value into the following formula (4) to calculate:

[0152] ΔTi DS =-0.00431+0.01253×(C AL +Si AL +Al DO-DS )-0.00766×(C AL +Si AL +Al DO-DS ) 2 (4)

[0153] Calculated by formula (4): ΔTi DS =0.00044wt.%;

[0154] Where: The titanium addition amount of molten steel after fine-tuning the composition and desulfurization is ΔTi DS Controlled to 0.00044%; the carbon content C in the steel measured after deoxidation and alloying AL 0.845wt.%; The silicon content Si in the steel measured after deoxidation and alloying AL 0.150

[0155] wt.%, the amount of deoxidizer aluminum added when fine-tuning the alloy composition DO-DS 0.413kg / t steel;

[0156] The temperature is controlled at 1565℃ during the composition fine-tuning and desulfurization process; after the composition fine-tuning and desulfurization are completed, the titanium content Ti in the molten steel is calculated.DS 0.00150wt.%; the actual detection results show that the titanium content in molten steel is DS 0.0013wt%, acid soluble aluminum Al s The content is 0.026wt.%, and the sulfur content is 0.0018wt.%;

[0157] 5) The conventional steel vacuum treatment was performed. At the end, the components and mass percentages in the steel were as follows: C: 0.958wt.%,

[0158] Si: 0.26wt.%Al s： 0.024wt.%, Cr: 1.47wt.%, Mn: 0.40wt.%, S: 0.0020wt.%, Ti:

[0159] 0.0015wt.%, T.[O]: 0.0005wt.%, N: 0.0045wt.%, Ca: 0.0002wt.%;

[0160] 6) After the vacuum treatment, the steel ingots and subsequent processes are cast under argon protection.

[0161] After testing, it was found that the number of TiN inclusions in the steel with a titanium content of 0.0015wt.% in this embodiment was reduced by 38.0% compared with the same inclusions in the steel with a titanium content of 0.0027wt.%, thereby reducing the TiN inclusions in the steel from the source and improving the smelting quality of the steel. As a result, fatigue cracks caused by non-deformed TiN inclusions during processing and use of GCr15 bearing steel were reduced, thereby increasing the tensile strength of GCr15 bearing steel at 800°C by 6.0%.

[0162] Example 3

[0163] The bearing steel smelted in this embodiment is GCr15;

[0164] A method for smelting and controlling titanium content and TiN inclusions in high-purity bearing steel, the steps of which are as follows:

[0165] 1) Requirements for carbon, silicon, titanium and temperature in molten iron, the raw material for steelmaking: The sum of the mass percentages of carbon and silicon is (C Fe +Si Fe ) is controlled at 4.96wt.% and the molten iron temperature is at 1385℃; Fe +Si Fe )=4.96wt.%Substitute into formula (1) to calculate the mass percentage content of titanium in molten iron Ti Fe 0.1199wt.%;

[0166] Ti Fe=-3.2828+1.3725×(C Fe +Si Fe )-0.1384×(C Fe +Si Fe ) 2 (1)

[0167] Where: The mass percentage of carbon in the molten iron entering the steelmaking furnace C Fe The mass percentage of silicon in the molten iron entering the steelmaking furnace is 4.51wt.%; Fe 0.450wt.%;

[0168] 2) Requirements for carbon, silicon, titanium and temperature in molten steel as raw material for refining:

[0169] Decarburize molten iron according to conventional methods and control the carbon content C in molten steel after decarburization ST At 0.109wt.%, silicon content Si ST At 0.080wt.%, the molten steel temperature is 1650℃; the mass percentage content of titanium in the molten steel is measured. ST 0.0002

[0170] wt.%:

[0171] 3) Deoxidation and alloying treatment of molten steel

[0172] When the composition and temperature of the molten steel reach the requirements in 2), add Al-Fe alloy at 2.158kg / t steel for deoxidation;

[0173] Final dissolved oxygen removal in molten steel DO According to the following formula (2), by adding Al-Fe DO Quantity control will be based on Al-Fe DO After removing 0.0195wt.% of dissolved oxygen content, the dissolved oxygen content in molten steel can be reduced to O SO control

[0174] Made at 0.0008wt%;

[0175] O DO =0.1102-1.1836×Al-Fe DO +3.5360×(Al-Fe DO ) 2 (2)

[0176] Where:

[0177] Al-Fe DO The amount of deoxidizer Al-Fe alloy added at the end of steelmaking is based on the C content in the molten steel. STThe amount of addition is calculated by the general calculation method to calculate the Al-Fe DO =2.158kg / t steel;

[0178] After deoxidation, alloying treatment is carried out immediately, that is, adding carburizer, silicon, manganese, and chromium alloy elements according to the conventional method for alloying treatment:

[0179] In addition to the conventional addition of quicklime to make slag, SiO2 with a particle size of 0.05-0.25 μm was added to the refined slag at a rate of 0.082 kg / t steel; the basicity of the initial refined slag was 11.3; in the molten steel, in addition to controlling the amount of deoxidizer added, the titanium addition amount ΔTi AL according to

[0180] The following formula (3) is used for control:

[0181] ΔTi AL =0.00139-0.00361×(ΔC AL +ΔSi AL )+0.00369×(ΔC AL +ΔSi AL ) 2 (3)

[0182] After testing, the carbon content C in the molten steel after deoxidation and alloying AL The carbon content C in the molten steel measured after steelmaking is 0.795wt.% ST 0.109wt.% Si content in molten steel after deoxidation and alloying AL 0.160wt.% Si content in molten steel at the end of steelmaking ST is 0.080wt.%, then ΔC AL =C AL -C ST =0.795wt.%-0.109wt.%=0.686

[0183] wt.%,ΔSi AL =Si AL -Si ST =0.160wt.%-0.080wt.%=0.080wt.%;

[0184] ΔC b-AL and ΔSi b-AL The calculated value of is calculated by formula (3): ΔTi AL =0.00079wt.%;

[0185] Where: The increase in titanium during deoxidation alloying process ΔTi AL The increase in carbon content is 0.00079wt.%, and the increase in carbon content is ΔCAL 0.686

[0186] wt.%, silicon increase ΔSi AL 0.080wt.%;

[0187] It should be noted that the temperature of the molten steel should be kept not lower than 1500℃ during the deoxidation and alloying process. After the deoxidation and alloying process, the titanium content Ti in the molten steel is calculated. AL 0.00099wt.%; the actual detection results show that the titanium content in molten steel is AL Control

[0188] 0.0010wt% Acid soluble aluminum Al s The content is 0.061wt.%;

[0189] 4) Fine-tune alloy composition and desulfurize

[0190] 15 minutes after the deoxidation and alloying, aluminum deoxidation is added at 0.865kg / t steel; carburizer, SiC, chromium and manganese alloy elements are conventionally added to fine-tune the composition; when adding desulfurized slag by conventional methods, SiO2 with a particle size of 0.05-0.25μm is added at 0.13kg / t steel, and the initial desulfurized slag basicity is controlled to 12.8, and the TiO2 content in the slag is 0.08

[0191] wt.%; titanium addition ΔTi after composition fine-tuning and desulfurization DS Controlled by the following formula (4);

[0192] After testing, the carbon content C in the ladle after deoxidation and alloying AL 0.795wt.% The silicon content Si in the molten steel measured after deoxidation and alloying AL 0.160wt.%The amount of deoxidizer Al added at the beginning of desulfurization DO-DS for

[0193] 0.865kg / t steel, then the measured C AL、 Si AL and Al DO-DS Substitute each value into the following formula (5) to calculate:

[0194] ΔTi DS =-0.00431+0.01253×(C AL +Si AL +Al DO-DS )-0.00766×(C AL +Si AL +Al DO-DS ) 2 (4)

[0195] According to formula (4), we can get: ΔTi DS =0.00043wt.%;

[0196] Where: The titanium addition amount of molten steel after fine-tuning the composition and desulfurization is ΔTi DS Controlled to 0.00043%; the carbon content C in molten steel measured after deoxidation and alloying AL 0.795wt.%; The silicon content Si in the molten steel measured after deoxidation and alloying AL 0.160wt.% The amount of deoxidizer aluminum added when fine-tuning the alloy composition is Al DO-DS 0.865kg / t steel;

[0197] The temperature is controlled at 1590℃ during the composition fine-tuning and desulfurization process; after the composition fine-tuning and desulfurization are completed, the titanium content Ti in the molten steel is calculated. DS The actual detection results show that the titanium content in molten steel is 0.00142wt.%; DS Controlled at 0.0013wt%, acid-soluble aluminum Al s The content is 0.027wt.%, and the sulfur content is 0.0015wt.%;

[0198] 5) The conventional steel vacuum treatment was performed. At the end, the components and mass percentages in the steel were as follows: C: 0.968wt.%, Si: 0.31wt.%, Al s： 0.027wt.%, Cr: 1.51wt.%, Mn: 0.39wt.%, S: 0.0014wt.%, Ti:

[0199] 0.0014wt.%, T.[O]: 0.0005wt.%, N: 0.0035wt.%, Ca: 0.0002wt.%;

[0200] 6) After the vacuum treatment, the steel ingots and subsequent processes are cast under argon protection.

[0201] After testing, it was found that the number of TiN inclusions in the steel with a titanium content of 0.0014wt.% in this embodiment was reduced by 38.5% compared with the number of similar inclusions in the steel with a titanium content of 0.0027wt.%, thereby reducing the TiN inclusions in the steel from the source and improving the smelting quality of the steel. As a result, fatigue cracks caused by non-deformed TiN inclusions during processing and use of GCr15 bearing steel were reduced, thereby increasing the tensile strength of GCr15 bearing steel at 800°C by 6.4%.

[0202] The morphology and size of inclusions in the steel ingots corresponding to the present invention and the prior art were analyzed by using a scanning electron microscope combined with an energy dispersive spectrometer, and the percentage of TiN inclusions in the steel was counted. Figure 1is a SEM image of MnS-TiN type inclusions detected in the steel after being treated in the embodiment; Figure 2 This is a SEM image of MnS-TiN inclusions detected in steel after treatment using the prior art; Figure 3 is a SEM image of oxide-MnS-TiN inclusions detected in the steel after being treated in the embodiment; Figure 4 This is a SEM image of oxide-MnS-TiN inclusions detected in steel after being treated using the prior art.

[0203] This specific implementation is only the best example and is not a restrictive implementation of the technical solution of the present invention.

Claims

1. A method for controlling the Ti content and TiN inclusions in high purity bearing steel, the steps of which are as follows: 1) Requirements for carbon, silicon, titanium and temperature in molten iron, the raw material for steelmaking: The sum of the mass percentages of carbon and silicon is (C Fe +Si Fe ) is controlled at 4.22-4.96wt.%, the molten iron temperature is controlled at 1260-1400°C, the mass percentage content of titanium Ti Fe According to the following formula (1), the content of 0.0445wt.% to 0.1200wt.% is controlled; You Fe =-3.2828+1.3725×(C Fe +Si Fe )-0.1384×(C Fe +Si Fe ) 2 (1) Where: Ti Fe — is the mass percentage content of titanium measured in the molten iron entering the steelmaking furnace, unit: wt.%; C Fe — is the mass percentage of carbon measured in the molten iron entering the steelmaking furnace, unit: wt.%; Si Fe — is the mass percentage content of silicon measured in the molten iron entering the steelmaking furnace, unit: wt.%; 2) Requirements for carbon, silicon, titanium and temperature in the refined raw material molten steel: After the molten iron composition and temperature meet the requirements in 1), decarburization treatment is carried out by conventional steelmaking methods, and the molten steel temperature is controlled to be not less than 1600℃. The mass percentage of carbon in the molten steel is C ST Not more than 0.460wt.%, mass percentage content of silicon Si ST Not less than 0.020wt.%, titanium content by mass ST Not more than 0.0005wt.%; 3) Deoxidation and alloying treatment of molten steel When the composition and temperature of the molten steel reach the requirements in step 2), Al-Fe alloy is added at 1.45-2.25 kg / t steel for deoxidation; the dissolved oxygen content in the molten steel is removed. DO It is based on the C content of molten steel at the beginning of refining. ST , and then calculate the amount of deoxidizer Al-Fe alloy added to the steel DO , the dissolved oxygen content removed from the steel is O DO The dissolved oxygen content in the steel is controlled according to the following formula (2): SO Controlled to no more than 0.0013wt%, acid-soluble aluminum Al s The mass percentage content is not less than 0.024wt.%; O DO =0.1102-1.1836×Al-Fe DO +3.5360×(Al-Fe DO ) 2 (2) Where: O DO — is the dissolved oxygen content in the molten steel after deoxidation, unit: wt.%; Al-Fe DO — is the amount of Al-Fe alloy added during deoxidation, unit: kg / t steel; After deoxidation, a carburizer, silicon, chromium, and manganese alloying elements are added in sequence according to a conventional method for alloying treatment: after alloying, refined slag is added immediately, and in addition to the conventional addition of quicklime to make slag, SiO2 with a particle size of 0.05 to 0.25 μm is added according to 0.05 to 0.10 kg / t steel, and the basicity of the initial refined slag is controlled to be not less than 10.0, and the TiO2 content in the refined slag is not higher than 0.10 wt.%; During the deoxidation alloying process, the titanium addition ΔTi AL Control is performed according to the following formula (3): ΔTi AL =0.00139-0.00361×(ΔC AL +ΔSi AL )+0.00369×(ΔC AL +ΔSi AL ) 2 (3) Where: ΔTi AL —Ti is the mass percentage content of titanium in molten steel after deoxidation and alloying AL The mass percentage content of titanium Ti in the molten steel at the beginning of deoxidation ST The difference between the two, that is, the increase in titanium during the deoxidation alloying process, unit: wt.%; ΔC AL — is the mass percentage content of carbon C measured in molten steel after deoxidation and alloying AL The mass percentage of carbon C measured in the molten steel at the beginning of deoxidation ST The difference between the two is the amount of carbon added during the deoxidation alloying process, unit: wt.%; ΔSi AL — is the mass percentage content Si of silicon in molten steel after deoxidation and alloying AL The mass percentage of silicon Si in the molten steel at the beginning of deoxidation ST The difference between the two is the amount of silicon added during the deoxidation alloying process, unit: wt.%; it should be noted that the temperature of the molten steel should be kept not lower than 1500℃ during the deoxidation alloying process. After the deoxidation alloying process, the amount of titanium added in the molten steel is AL Not more than 0.0008wt.%; 4) Fine-tune the alloy composition of molten steel and desulfurize 15 minutes after the deoxidation alloying and the addition of refined slag, add aluminum for deoxidation at a rate of 0.40-1.65 kg / t steel; add carburizer, SiC and silicon, chromium and manganese alloy elements according to the conventional method to fine-tune the composition; When adding desulfurized slag by conventional methods, SiO2 with a particle size of 0.05-0.25 μm is added at 0.10-0.15 kg / t steel, and the basicity of the initial desulfurized slag is controlled to be not less than 8.0, and the TiO2 content in the slag is not higher than 0.10 wt.%; Composition fine-tuning and titanium addition ΔTi in molten steel after desulfurization DS Controlled by the following formula (4); Controlled refining temperature not less than 1550℃; Fine adjustment of composition and titanium addition ΔTi in molten steel after desulfurization DS Controlled to no more than 0.0005wt%, acid-soluble aluminum Al s The content of is not less than 0.010wt.% and the content of sulfur is not more than 0.0020wt.%; ΔYou DS =-0.00431+0.01253×(C AL +Yes AL +To DO-DS )-0.00766×(C AL +Yes AL +To DO-DS ) 2 (4) Where: ΔTi DS —Ti is the mass percentage content of titanium measured in molten steel after fine-tuning the composition and desulfurization DS After deoxidation and alloying, Ti AL The difference between the two is the amount of titanium added after the alloy composition is fine-tuned and desulfurization is completed, unit: wt.%; C AL — is the mass percentage of carbon measured in molten steel after deoxidation and alloying, unit: wt.%; Si AL — is the mass percentage content of silicon measured in molten steel after deoxidation and alloying, unit: wt.%; Al DO-DS — is the amount of deoxidizer aluminum added when fine-tuning the alloy composition, unit: kg / t steel; 5) Conventionally carry out molten steel vacuum treatment. At the end, the components and mass percentages in the steel are as follows: C: <h2 style=";text-align:left;direction:ltr">0.96wt.g~1.05wt.g,Si:0.28wt.g~0.32wt.g,Al<h2 style=";text-align:left;direction:ltr"> s： <h2 style=";text-align:left;direction:ltr"> 0.010wt.%~0.034wt.%,Cr: 1.45wt.%~1.51wt.%, Mn: 0.36wt.%~0.40wt.%, S: ≤0.0020wt.%, Ti: ≤0.0015 wt.%, T.[O]: ≤0.0005wt.%, N: ≤0.0050wt.%, Ca: ≤0.0003wt.%; 6) After the vacuum treatment, the steel ingots and subsequent processes are cast under argon protection.

2. A method for controlling Ti content and TiN inclusions in high purity bearing steel according to claim 1, characterized in that: Al s The mass percentage content is: 0.010~0.028wt.%.

3. A method for controlling Ti content and TiN inclusions in high purity bearing steel according to claim 1, characterized in that: Ti mass percentage content ≤ 0.0014wt.%.

4. A method for controlling Ti content and TiN inclusions in high purity bearing steel according to claim 1, characterized in that: S mass percentage content ≤ 0.0015wt.%.

5. A method for controlling Ti content and TiN inclusions in high purity bearing steel according to claim 1, characterized in that: N mass percentage content ≤ 0.0040wt.%.

Images