CN112159928A - Zr-containing bearing steel and preparation method thereof - Google Patents

Zr-containing bearing steel and preparation method thereof Download PDF

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CN112159928A
CN112159928A CN202011038125.5A CN202011038125A CN112159928A CN 112159928 A CN112159928 A CN 112159928A CN 202011038125 A CN202011038125 A CN 202011038125A CN 112159928 A CN112159928 A CN 112159928A
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steel
bearing steel
oxysulfide
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CN112159928B (en
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鲁金龙
成国光
丘文生
龙鹄
张志明
刘栋
王云鹏
余大华
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SGIS Songshan Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/076—Use of slags or fluxes as treating agents
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C22C33/06—Making ferrous alloys by melting using master alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

The application relates to the field of steel smelting, and relates to Zr-containing bearing steel and a preparation method thereof. The steel includes C: 0.95% -1.05%, Si: 0.2-0.3%, Mn: 0.3% -0.4%, Cr: 1.4% -1.65%, P:<0.020％，S：0.001％～0.004％，Al：0.010％～0.018％，O：<0.0010％，Ca：<0.0008％，Mg：<0.0008%, Zr: 0.0025 to 0.0050 percent, and the Zr content meets the requirement of Zr>(0.2 × Al + 0.0005%). The bearing steel contains oxides and oxygen in the amount of composite oxysulfideMore than 90% of the total number of sulfides, and equivalent diameter>The distribution density of 1 μm of the complex oxysulfide is 1-4/mm2And the adverse effect of large-size oxides in the traditional bearing steel on the fatigue performance can be reduced.

Description

Zr-containing bearing steel and preparation method thereof
Technical Field
The application relates to the field of steel smelting, in particular to Zr-containing bearing steel and a preparation method thereof.
Background
The bearing is one of the most important basic parts in industrial machinery, and is widely applied to the fields of precision machine tools, wind power, large machinery and the like. The fatigue life of the bearing is one of the important indexes for evaluating the quality of bearing steel. A large number of researches show that the oxygen content in the bearing steel has a negative exponential relation with the fatigue life of the bearing, so that the extremely low oxygen content is the key for ensuring the metallurgical quality of the bearing steel all the time. In recent years, with continuous progress of domestic metallurgical technology and smelting equipment, some steel enterprises can stably produce bearing steel with the oxygen content of 4-6 ppm.
With the continuous reduction of the oxygen content, the type and size control of inclusions in steel becomes the key to further improve the metallurgical quality of bearing steel. At present, the more harmful inclusions in the bearing steel mainly include large-sized calcium aluminate, aggregated magnesium aluminate spinel (alumina, magnesia, etc.) and large-sized TiN.
Because the basicity of the bearing steel slag is generally higher and the Al content in the steel is also higher, under the conditions of high basicity and high Al, CaO in the slag is reduced, Ca element enters molten steel, and therefore calcium aluminate inclusion is generated in the steel. In addition, bearing steel generally needs to be subjected to vacuum treatment, and MgO in refining slag and refractory materials is easily reduced by Al in the steel under the vacuum condition to cause Mg to enter molten steel, so that magnesium aluminate spinel inclusions are generated in the steel. In order to reduce the number and size of inclusions in bearing steel as much as possible, the prior patents CN 109777918A, CN 109402327A, and the like all have strict requirements on the external refining process. However, there is a limit to reduce the amount and size of oxides in bearing steel, and there is no information on how to further reduce the harm of oxides in steel after the oxygen content in bearing steel is reduced and the size of oxides is reduced to a certain extent.
MnS is a common inclusion in bearing steel, and because the hardness of MnS is not high, the damage to the fatigue performance of the bearing steel is far lower than that of calcium aluminate and magnesium aluminate spinel. In addition, MnS is often generated at the final stage of molten steel solidification, and the steel often has a composite oxysulfide in which MnS is wrapped on the periphery of calcium aluminate and magnesium aluminate spinel, and the composite oxysulfide has a soft-packing hard layered structure, so that the damage of pure calcium aluminate and magnesium aluminate spinel on the fatigue performance of bearing steel can be greatly reduced. How to utilize MnS inclusion in steel to greatly improve the proportion of soft-package-hard composite oxysulfide so as to further reduce the harm of oxides in bearing steel, and no related research exists at present.
CN107312908, "metallurgical Process for improving the morphology of MnS inclusions in non-heat-treated steels", mentions the possibility of adding Zr alloys to form ZrO in steels2The oxides improve the shape of MnS, and mainly aim at medium-carbon non-quenched and tempered steel, and the difference between C, Si, Mn, S, Al and O and bearing steel is large. In addition, the main objective of this patent is to improve the morphology of the sulfides in the steel, and there is no description of the damage to the oxides in the steel.
Disclosure of Invention
The embodiment of the application aims to provide Zr-containing bearing steel and a preparation method thereof, aiming at reducing the adverse effect of oxides in the Zr-containing bearing steel on the fatigue performance.
In a first aspect, the present application provides a Zr-containing bearing steel, wherein the bearing steel comprises the following chemical components by mass percent:
c: 0.95% -1.05%, Si: 0.2-0.3%, Mn: 0.3% -0.4%, Cr: 1.4% -1.65%, P: < 0.020%, S: 0.001-0.004%, Al: 0.010-0.018%, O: < 0.0010%, Ca: < 0.0008%, Mg: < 0.0008%, Zr: 0.0025% -0.0050%, and the Zr content satisfies: zr > (0.2 × Al + 0.0005%), and the balance Fe and inevitable impurity elements;
the bearing steel contains oxides and oxysulfides, and the oxides comprise: CaZrO3Or ZrO2The Zr-containing oxide of (1); the oxysulfide comprises a composite oxysulfide with Zr-containing oxide as a core and MnS wrapped at the periphery;
wherein the number of the composite oxysulfide accounts for more than 90% of the total number of the oxides and the oxysulfide, and the equivalent diameter>The distribution density of 1 μm of the complex oxysulfide is 1-4/mm2The equivalent diameter of the Zr-containing oxide in the composite oxysulfide is 5 μm or less.
In some embodiments of the present application, the chemical composition of the bearing steel comprises, in mass percent:
c: 0.95% -1.05%, Si: 0.2-0.3%, Mn: 0.3% -0.4%, Cr: 1.4% -1.65%, P: < 0.020%, S: 0.001-0.004%, Al: 0.010-0.018%, O: 0.0003% -0.0010%, Ca: < 0.0008%, Mg: < 0.0008%, Zr: 0.0025% -0.0050%, and the Zr content satisfies: zr > (0.2 × Al + 0.0005%), and the balance Fe and inevitable impurity elements.
In some embodiments of the present application, the number of complex oxysulfides is 92.7% to 96.2% of the total number of oxides and oxysulfides.
In some embodiments of the present application, the equivalent diameter>The distribution density of 1 μm of the complex oxysulfide is 1.9-3.1 pieces/mm2。
In a second aspect, the present application provides a method of manufacturing a Zr-containing bearing steel, comprising:
a primary smelting process, wherein the steel after tapping is controlled to be as follows: ω [ Al ]: 0.04 to 0.06 percent;
an LF refining process;
vacuum treatment, after re-pressing, adding zirconium alloy to make Zr content in steel meet omega [ Zr ]: 0.0025% to 0.0050%, and [ omega ] Zr (0.2 x [ omega ] Al + 0.0005%); and
and (5) continuous casting.
In some embodiments of the present application, argon gas is introduced and stirred after the zirconium alloy is added in the vacuum treatment process.
In some embodiments of the present application, argon gas is introduced to stir, thereby shaking the slag surface without exposing the molten steel.
In some embodiments of the present invention, the stirring time with argon is 25 to 30 minutes.
In some embodiments of the present application, in the LF refining process, the slag composition during refining is controlled to satisfy: omega [ CaO]：50％～60％，ω[SiO2]：5％～10％，ω[Al2O3]：20％～30％，ω[MgO]：3％～10％，ω[CaF2]: 0.5 to 3 percent, and the amount of refining slag is 15 to 20kg per ton of steel.
In some embodiments of the application, in the continuous casting process, totally-enclosed protective pouring is adopted, and the superheat degree of molten steel is controlled to be 10-35 ℃.
The Zr-containing bearing steel and the preparation method thereof provided by the embodiment of the application have the beneficial effects that:
according to the scheme, the content of core elements of Zr, Al, O, Ca and Mg in the bearing steel is controlled, the characteristics of oxides and oxysulfides in the bearing steel are changed, the size of the oxides in the steel is reduced greatly, and the equivalent diameter of the oxides is reduced>The distribution density of 1 μm of the complex oxysulfide is 1-4/mm2The equivalent diameter of the Zr-containing oxide in the composite oxysulfide is 5 μm or less. Secondly, the oxysulfide of the "soft-pack hard" envelope type in the bearing steel accounts for more than 90% of the total amount of all oxides and oxysulfides. Thereby effectively reducing the adverse effect of large-size oxides in the traditional bearing steel on the fatigue performance and greatly improving the quality of the bearing steel.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
FIG. 1 is a typical SEM image of a composite oxysulfide in a material prepared in example 1 of the present application;
FIG. 2 is a typical SEM image of a composite oxysulfide in a material prepared in example 2 of the present application;
FIG. 3 is a typical SEM image of a composite oxysulfide in a material prepared in example 3 of the present application;
FIG. 4 is a typical SEM and area scan energy spectrum analysis (grey scale processing is performed on the picture) of large-size calcium magnesium aluminate in the material prepared in comparative example 1;
FIG. 5 is a typical SEM image of a composite oxysulfide in the material prepared in comparative example 2;
FIG. 6 is a typical SEM and area scan energy spectrum analysis chart (gray scale processing is performed) of the metallic inclusions in the material prepared in comparative example 3.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments.
Thus, the following detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In the present application, "%" alone represents mass percent; or "%" and "ω" are both expressed by mass percentage.
The embodiment of the application provides bearing steel, and the chemical components of the bearing steel comprise, by mass:
c: 0.95% -1.05%, Si: 0.2-0.3%, Mn: 0.3% -0.4%, Cr: 1.4% -1.65%, P: < 0.020%, S: 0.001-0.004%, Al: 0.010-0.018%, O: < 0.0010%, Ca: < 0.0008%, Mg: < 0.0008%, Zr: 0.0025% -0.0050%, and the Zr content satisfies: zr > (0.2 × Al + 0.0005%), and the balance Fe and inevitable impurity elements.
According to the scheme, the content of core elements of Zr, Al, O, Ca and Mg in the bearing steel is controlled, the characteristics of oxides and oxysulfides in the bearing steel are changed, the size of the oxides in the steel is firstly greatly reduced, and then the softly-packaged hard-packaged oxysulfide in the bearing steel accounts for more than 90% of the total amount of all the oxides and oxysulfides. Therefore, the adverse effect of large-size oxides in the bearing steel on the fatigue performance can be effectively reduced, and the quality of the bearing steel is greatly improved.
Specifically, the bearing steel contains oxides and oxysulfides, and the oxides include: CaZrO3Or ZrO2The Zr-containing oxide of (1); the oxysulfide comprises a composite oxysulfide with Zr-containing oxide as a core and MnS wrapped at the periphery;
wherein the number of the composite oxysulfide accounts for more than 90% of the total number of the oxides and the oxysulfide, and the equivalent diameter>The distribution density of 1 μm of the complex oxysulfide is 1-4/mm2The equivalent diameter of the Zr-containing oxide in the composite oxysulfide is 5 μm or less.
Furthermore, the number of the composite oxysulfide accounts for 92.7 to 96.2 percent of the total number of the inclusions. Illustratively, the number of complex oxysulfides accounts for 92.7%, 94.7%, 96.2%, etc. of the total number of inclusions.
Further, equivalent diameter>The distribution density of 1 μm of the complex oxysulfide is 1.9-3.1 pieces/mm2. Illustratively, equivalent diameter>The distribution density of 1 μm of the complex oxysulfide was 1.9 particles/mm22.6 pieces/mm2Or 3.1 pieces/mm2。
The reason why the value ranges of the components Zr, Al, O, Ca and Mg of the bearing steel are limited is described below:
Al：0.010％～0.018％：
al element is a commonly used deoxidizer in bearing steel, has the function of mainly reducing the oxygen content in the bearing steel, and has high oxygen content and large fluctuation when omega [ Al ] is less than 0.010 percent, thereby influencing the fatigue performance of the bearing steel; when omega [ Al ] is more than 0.018%, the molten steel is easy to be secondarily oxidized, and Al is seriously oxidized in the smelting process. In addition, too high Al content does not have a significant effect on further reducing the oxygen content in the steel, and therefore, it is necessary to control the ratio of ω [ Al ] in the steel at the end of smelting: 0.010-0.018%.
Further, in some embodiments of the present application, the value of the chemical component Al ranges from 0.011% to 0.017%. Further optionally, the value of the chemical component Al ranges from 0.012% to 0.016%. Illustratively, the chemical component Al mentioned above takes a value of 0.013%, 0.014%, 0.015%, or 0.016%.
O：<0.0010％：
The O element is the main impurity element in the bearing steel, the content of the O is too high, the fatigue performance of the bearing steel can be obviously damaged when the amount of the oxide in the steel is more, and therefore omega O in the steel is controlled to be less than 0.0010 percent when smelting is finished.
Further, in some embodiments of the present application, the chemical component O ranges from 0.0003% to 0.0010%. Further optionally, the value range of the chemical component O is 0.0004% to 0.0007%. Illustratively, the chemical component O mentioned above takes a value of 0.0004%, 0.0005%, 0.0006%, or 0.0007%.
Zr: 0.0025% -0.005%, and satisfies: zr > (0.2 × Al + 0.0005%):
the Zr element is a secondary deoxidizer in the present invention, and is used for modifying oxides such as calcium aluminate, magnesium aluminate spinel, and alumina, which have been generated in steel, to convert them into oxides such as calcium zirconate and zirconium dioxide. The Zr content is too high, the molten steel is easy to generate secondary oxidation, the cost is increased, and the excessive Zr and Ti and N elements in the molten steel are easy to generate large-size (Zr, Ti) N inclusions or other metallic inclusions; the Zr content is too low and is not completely modified, and according to the thermodynamic calculation result, the Zr content needs to meet the following requirements: zr > (0.2 xAl + 0.0005%), so that the primary oxides in the molten steel are completely denatured, and therefore, the ratio of ω [ Zr ] in the steel at the end of smelting is controlled: 0.0025% to 0.005%, and satisfies ω [ Zr ] > (0.2 × ω [ Al ] + 0.0005%).
Further, in some embodiments of the present application, Zr is selected from 0.0025% to 0.0045%. Further optionally, the value range of the chemical component Zr is 0.0030% to 0.0045%. Illustratively, the value of the chemical component Zr is 0.0030%, 0.0035%, 0.0040%, or 0.0045%.
Ca：<0.0008％：
Ca element: mainly from the CaO in the slag and a small amount from other alloy inclusions. In order to ensure extremely low oxygen content in the bearing steel, the alkalinity and high Al content of blast furnace slag are usually controlled in the refining process, Ca in the slag can easily enter molten steel to generate calcium aluminate inclusions, and the fatigue performance of the steel is greatly damaged. In addition, since the critical content of Zr element-modified calcium aluminate increases due to an excessively high calcium content, ω [ Ca ] < 0.0008% is controlled in the steel at the end of smelting.
Further, in some embodiments of the present invention, the chemical component Ca is selected from the range of 0.0001% to 0.0006%. Further optionally, the chemical component Ca ranges from 0.0001% to 0.0005%. Illustratively, the chemical component Ca is 0.0001%, 0.0002%, 0.0003%, 0.0004%, or 0.0005%.
Mg：<0.0008％：
Mg element: the magnesium aluminate spinel oxide with a regular shape has great harm to the fatigue performance of the steel, and in addition, the magnesium aluminate spinel oxide has high melting point and is easy to aggregate in molten steel to form large-size cluster or chain-shaped inclusion, thereby further damaging the fatigue performance of the bearing steel. In addition, magnesium aluminate spinel easily promotes TiN in steel to nucleate on the magnesium aluminate spinel, increases the size of TiN, and indirectly damages the fatigue performance of bearing steel. Therefore, omega [ Mg ] in the steel at the end of smelting is controlled to be less than 0.0008%.
Further, in some embodiments of the present application, the chemical component Mg ranges from 0.0001% to 0.0006%. Further optionally, the range of the chemical component Mg is 0.0001% to 0.0005%. Illustratively, the chemical composition Mg mentioned above takes a value of 0.0001%, 0.0002%, 0.0003%, 0.0004%, or 0.0005%.
In some embodiments of the present application, the chemical composition of the bearing steel comprises, in mass percent:
c: 0.95% -1.05%, Si: 0.2-0.3%, Mn: 0.3% -0.4%, Cr: 1.4% -1.65%, P: < 0.020%, S: 0.001-0.004%, Al: 0.012% -0.018%, O: < 0.0010%, Ca: < 0.0008%, Mg: < 0.0008%, Zr: 0.0025% -0.0050%, and the Zr content satisfies: zr > (0.2 × Al + 0.0005%), and the balance Fe and inevitable impurity elements.
In some embodiments of the present application, the chemical composition of the bearing steel comprises, in mass percent:
c: 0.96% -1.04%, Si: 0.21-0.29%, Mn: 0.31-0.39%, Cr: 1.4% -1.65%, P: < 0.020%, S: 0.001-0.004%, Al: 0.011% -0.017%, O: 0.0003% -0.0010%, Ca: < 0.0008%, Mg: < 0.0008%, Zr: 0.0025% -0.0050%, and the Zr content satisfies: zr > (0.2 × Al + 0.0005%), and the balance Fe and inevitable impurity elements.
In some embodiments of the present application, the chemical composition of the bearing steel comprises, in mass percent:
c: 0.95% -1.03%, Si: 0.22-0.28%, Mn: 0.32-0.37%, Cr: 1.45% -1.52%, P: < 0.020%, S: 0.001-0.004%, Al: 0.010-0.018%, O: 0.0003% -0.0010%, Ca: < 0.0008%, Mg: < 0.0008%, Zr: 0.0025% -0.0050%, and the Zr content satisfies: zr > (0.2 × Al + 0.0005%), and the balance Fe and inevitable impurity elements.
Some embodiments of the present application provide a method of manufacturing a bearing steel, the bearing steel of the previous embodiments being manufactured. By strictly controlling the contents of Al, O, Zr, Ca and Mg in the steel in the smelting process, the size of oxides in the steel can be obviously reduced, the proportion of composite oxysulfide is improved, and the adverse effect of large-size oxides in the bearing steel on the fatigue performance is reduced, so that the metallurgical quality of the bearing steel is greatly improved.
Step S1, preliminary smelting process.
In the primary smelting process (converter or electric furnace), the functions of slagging, removing P, C and raising temperature are quickly completed, and after the primary smelting is finished, the aluminum iron, carbon powder, alloy and slag charge are added in turn, so that after the steel is completely tapped, the C, Si, Mn and Cr in the steel are close to the lower limit of the components. Specifically, the bearing steel comprises the following components in percentage by mass: 0.95% -1.05%, Si: 0.2-0.3%, Mn: 0.3% -0.4%, Cr: 1.4 to 1.65 percent.
Further, in the primary smelting process, the following steps in the steel after tapping are controlled: ω [ Al ]: 0.04 to 0.06 percent.
Further optionally, in the primary smelting process, controlling the following steps in the steel after tapping: ω [ Al ]: 0.041 to 0.059 percent. Further optionally, in the primary smelting process, controlling the following steps in the steel after tapping: ω [ Al ]: 0.045% -0.055%. Illustratively, in the primary smelting process, the following steel is controlled: ω [ Al ]: 0.045%, 0.048%, 0.050%, 0.052%, or 0.054%.
Step S2, LF refining process.
And adding a small amount of lime or fluorite and other slag materials when the LF arrives at the station, electrifying and heating up, adding a small amount of silicon carbide in the smelting process to quickly form white slag, and enabling the slag components in the refining process to meet the following requirements: omega [ CaO]：50％～60％、ω[SiO2]：5％～10％、ω[Al2O3]：20％～30％、ω[MgO]：3％～10％、ω[CaF2]: 0.5 to 3 percent, and the amount of refining slag is 15 to 20kg per ton of steel. And adding alloy according to the process sampling result, so that the components in the steel basically reach the target components when the LF is out of the station.
Further optionally, in the LF refining process, the slag composition during refining is controlled to satisfy: omega [ CaO]：51％～59％，ω[SiO2]：6％～9％，ω[Al2O3]：21％～29％，ω[MgO]：4％～9％，ω[CaF2]：0.6％～2.9％。
Illustratively, in the LF refining process, the slag composition in the refining process is controlled to meet the following conditions: omega [ CaO]：57.2％，ω[SiO2]：7.1％，ω[Al2O3]：26.6％，ω[MgO]：6.0％，ω[CaF2]：1.1％。
Further optionally, the amount of refining slag is 16-19 kg/ton steel. Illustratively, the amount of refining slag is 17 kg/ton steel or 18 kg/ton steel.
Step S3, vacuum processing step.
After the procedure of repressing and before blowing Ar for weak stirring, adding zirconium alloy to make Zr content in steel meet omega [ Zr ]: 0.0025% -0.0050%, and the Zr content satisfies: zr > (0.2 × Al + 0.0005%).
In some embodiments, the N and H content of the steel is sufficiently reduced by maintaining a high vacuum (<67Pa) in the vacuum furnace for more than 25 minutes during the vacuum treatment process (VD or RH). After re-pressing, adding zirconium alloy (zirconium iron or zirconium silicon iron) to make Zr content in steel meet omega [ Zr ]: 0.0025% -0.0050%, and the Zr content satisfies: zr > (0.2 × Al + 0.0005%).
Further, in the vacuum treatment step, after the zirconium alloy was added, argon gas was introduced and the mixture was stirred.
Through introducing argon gas and stirring, the inclusion can be sufficiently floated to be removed.
Further, when argon gas is introduced for stirring, the slag surface is shaken, but the molten steel is not exposed.
Further, argon is introduced and the stirring time is 25-30 minutes.
In some embodiments, the stirring is performed with a weak argon gas. The stirring intensity of the weak argon stirring is preferably that the slag surface slightly shakes and the molten steel is not exposed. Further optionally, the stirring time of the weak argon is 25-30 minutes. Illustratively, the weak argon stirring time is 26 minutes, 27 minutes, 28 minutes, or 29 minutes.
Further, the components of the molten steel before ladle lifting meet the following requirements: ω [ C ]: 0.95% -1.05%, omega [ Si ]: 0.2% -0.3%, omega [ Mn ]: 0.3% -0.4%, omega [ Cr ]: 1.4% -1.65%, ω [ P ]: < 0.020%, ω [ S ]: 0.001-0.004%, omega [ Al ]: 0.010% -0.018%, omega [ O ]: < 0.0010%, ω [ Ca ]: < 0.0008%, ω [ Mg ]: < 0.0008%, ω [ Zr ]: 0.0025% -0.0050%, and the Zr content satisfies: ω [ Zr ] > (0.2X ω [ Al ] + 0.0005%); the balance of Fe and inevitable impurity elements.
And step S4, a continuous casting process.
The whole process adopts closed protective pouring to avoid secondary oxidation of molten steel.
Further, the superheat degree of the molten steel in the tundish is 10-35 ℃. Further optionally, the superheat degree of the molten steel in the tundish is 15-33 ℃; further optionally, the superheat degree of the molten steel in the tundish is 15-30 ℃. Illustratively, the superheat of the tundish molten steel is 16 ℃, 18 ℃, 20 ℃, 25 ℃ or 28 ℃.
The features and properties of the present application are described in further detail below with reference to examples:
example 1
A bearing steel is provided having the chemical composition shown in table 1. The preparation method comprises the following steps:
in the first step, 130 tons of top-bottom combined blown converter.
110 tons of molten iron and 20 tons of scrap steel are used as main raw materials, aluminum ingots, carbon powder, ferrosilicon, ferromanganese, ferrochromium and slag are added in the tapping process, and omega Al in the steel is 0.047 percent after the molten steel is completely transferred to a steel ladle.
And secondly, LF refining.
After the LF station, 200kg of lime, 50kg of compound deoxidizer, a small amount of silicon carbide and fluorite are added to perform white slag making operation, wherein the component of the refined slag is omega [ CaO [ ]]：57.9％、ω[SiO2]：7.8％、ω[Al2O3]：26.8％、ω[MgO]：4.2％、ω[CaF2]: 1.1 percent. In the refining process, according to the component inspection result of the molten steel, a proper amount of alloy is correspondingly added according to the target component.
And thirdly, RH vacuum smelting.
And keeping the vacuum chamber at the pressure of 67Pa for 26 minutes, firstly adding ferrozirconium after repressing, then stirring for 27 minutes by weak argon, and then lifting for casting.
And fourthly, continuously casting.
The whole process adopts closed protective pouring to avoid secondary oxidation of molten steel. The superheat degree of molten steel in the tundish is 20 ℃, and the size of a casting blank is 320mm multiplied by 425 mm.
Example 2
A bearing steel is provided having the chemical composition shown in table 1. The procedure was essentially the same as in example 1, except that:
after the molten steel is completely transferred into ladle, the omega Al content in the steel is 0.054%.
The refining slag has different components. The refining slag comprises the following components: omega [ CaO]：58.7％、ω[SiO2]：7.2％、ω[Al2O3]：28.3％、ω[MgO]：3.8％、ω[CaF2]：0.7％。
Example 3
A bearing steel is provided having the chemical composition shown in table 1. The procedure was essentially the same as in example 1, except that:
after the molten steel is completely transferred into ladle, the omega Al content in the steel is 0.051%.
The refining slag comprises the following components: omega [ CaO]：57.5％、ω[SiO2]：8.0％、ω[Al2O3]：26.9％、ω[MgO]：3.9％、ω[CaF2]：1.7％。
Comparative example 1
A bearing steel is provided having the chemical composition shown in table 1. The procedure was essentially the same as in example 1, except that:
no Zr alloy is added, and the refining slag has different components.
The refining slag comprises the following components: omega [ CaO]：57.3％、ω[SiO2]：6.9％、ω[Al2O3]：28.1％、ω[MgO]：4.1％、ω[CaF2]：1.2％。
Comparative example 2
A bearing steel is provided having the chemical composition shown in table 1. The procedure was essentially the same as in example 1, except that:
the Zr alloy has different addition amount and different refining slag components.
Zr content in comparative example 2: omega [ Zr ] is 0.0018%.
The refining slag comprises the following components: omega [ CaO]：57.1％、ω[SiO2]：7.2％、ω[Al2O3]：27.1％、ω[MgO]：4.8％、ω[CaF2]：1.3％。
Comparative example 3
A bearing steel is provided having the chemical composition shown in table 1. The procedure was essentially the same as in example 1, except that:
the Zr alloy has different addition amount and different refining slag components.
Zr content in comparative example 3: omega Zr is 0.0062%.
The refining slag comprises the following components: omega [ CaO]：58.5％、ω[SiO2]：7.1％、ω[Al2O3]：25.1％、ω[MgO]：4.4％、ω[CaF2]：1.9％。
Table 1 example 1 to comparative example 3 bearing steel chemical composition content, ω%
Figure BDA0002705469870000131
Figure BDA0002705469870000141
Examples of the experiments
The bearing steels provided in examples 1 to 3 and comparative examples 1 to 3 were examined for inclusions.
And (3) carrying out impurity statistics on the casting blanks produced in the examples 1-3 and the comparative examples 1-3, and representing the impurities in the casting blanks produced in the examples 1-3 and the comparative examples 1-3 by adopting a scanning electron microscope and an energy spectrum analyzer.
The results show that:
in example 1: 92.7% of the oxides in the casting blank are composite oxysulfide, and the main component of the oxides is ZrO2The typical appearance is shown in the attached figure 1 in the specification,>the distribution density of 1 μm of the complex oxysulfide is 1.9 pieces/mm2The equivalent diameter of the oxide in the core is substantially 5 μm or less.
In example 2: 94.7% of the oxide in the casting blank is composite oxysulfide, and the main component of the oxide is ZrO2The typical appearance is shown in figure 2 in the specification,>1 μm ofThe distribution density of the composite oxysulfide is 3.1 pieces/mm2The equivalent diameter of the oxide in the core is substantially 5 μm or less.
In example 3: 96.2% of the oxides in the casting blank are composite oxysulfide, and the main component of the oxides is CaZrO3The typical appearance is shown in figure 3 in the specification,>the distribution density of 1 μm of the complex oxysulfide is 2.6 pieces/mm2The equivalent diameter of the oxide in the core is substantially 5 μm or less.
In comparative example 1: 19.3% of the oxides in the casting blank are composite oxysulfide,>the distribution density of 1 μm of the complex oxysulfide is 1.7 pieces/mm2The main component of most of the oxides is calcium aluminate or calcium magnesium aluminate, and the small amount of the oxides is magnesium aluminate spinel. The typical morphology of the calcium magnesium aluminate is shown in the attached figure 4 of the specification, the calcium magnesium aluminate contains a small amount of S elements inside, the equivalent diameter can reach more than 50 mu m, and the fatigue performance of the bearing steel is greatly influenced.
In comparative example 2: 33.1% of the oxides in the casting blank are composite oxysulfide,>the distribution density of 1 μm of the complex oxysulfide is 1.2 pieces/mm2The main component of the other partial oxides is calcium aluminate or calcium magnesium aluminate, and the small amount of magnesium aluminate spinel. The typical morphology of the complex oxysulfide is shown in the attached figure 5, and ZrO with small equivalent diameter formed after Zr is added into steel2The particles surround the calcium aluminate and finally induce MnS to form and grow on the particles in the solidification process. Because the Zr content in the steel is not enough to be added, the oxides originally generated in the steel, such as calcium aluminate, calcium magnesium aluminate, magnesium aluminate spinel, alumina and the like, are not enough to be completely converted into pure CaZrO3Or ZrO2. As can be seen from the typical morphology of the composite oxides, ZrO in steel2The particle equivalent diameter is significantly smaller than calcium aluminate.
In comparative example 3, 93.7% of the oxides in the cast slab were complex oxysulfides,>the distribution density of 1 μm of the complex oxysulfide is 3.2 pieces/mm2. The oxide being ZrO based2The equivalent diameter of the oxide in the core is substantially 5 μm or less. However, a large amount of white metal inclusions are simultaneously generated in the steel, the main component is Zr simple substance, the typical appearance is as followsThe result of the area scan is shown in figure 6 of the specification. The shape of the alloy is similar to that of TiN, the alloy is regular, the equivalent diameter is more than 5 mu m, and the influence on the fatigue performance is large. Therefore, the Zr content in the steel should not be too high.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (10)

1. The Zr-containing bearing steel is characterized by comprising the following chemical components in percentage by mass:
c: 0.95% -1.05%, Si: 0.2-0.3%, Mn: 0.3% -0.4%, Cr: 1.4% -1.65%, P: < 0.020%, S: 0.001-0.004%, Al: 0.010-0.018%, O: < 0.0010%, Ca: < 0.0008%, Mg: < 0.0008%, Zr: 0.0025% -0.0050%, and the Zr content satisfies: zr > (0.2 × Al + 0.0005%), and the balance Fe and inevitable impurity elements;
the Zr-containing bearing steel contains oxides and oxysulfides, wherein the oxides comprise: CaZrO3Or ZrO2The Zr-containing oxide of (1); the oxysulfide comprises a composite oxysulfide with the Zr-containing oxide as a core and MnS wrapped at the periphery;
wherein the number of the composite oxysulfide accounts for more than 90% of the total number of the oxide and the oxysulfide, and the equivalent diameter>The distribution density of the 1 μm complex oxysulfide is 1-4/mm2And the equivalent diameter of the Zr-containing oxide in the interior of the composite oxysulfide is 5 μm or less.
2. The Zr bearing steel according to claim 1, wherein the alloy steel sheet is a steel sheet,
the bearing steel comprises the following chemical components in percentage by mass:
c: 0.95% -1.05%, Si: 0.2-0.3%, Mn: 0.3% -0.4%, Cr: 1.4% -1.65%, P: < 0.020%, S: 0.001-0.004%, Al: 0.010-0.018%, O: 0.0003% -0.0010%, Ca: < 0.0008%, Mg: < 0.0008%, Zr: 0.0025% -0.0050%, and the Zr content satisfies: zr > (0.2 × Al + 0.0005%), and the balance Fe and inevitable impurity elements.
3. The Zr bearing steel according to claim 1, wherein the alloy steel sheet is a steel sheet,
the number of the composite oxysulfide is 92.7 to 96.2 percent of the total number of the oxide and the oxysulfide.
4. The Zr bearing steel according to claim 1, wherein the alloy steel sheet is a steel sheet,
equivalent diameter>The distribution density of the 1 μm complex oxysulfide is 1.9-3.1 pieces/mm2。
5. The method for producing the Zr-containing bearing steel according to any one of claims 1 to 4, characterized by comprising:
a primary smelting process, wherein the steel after tapping is controlled to be as follows: ω [ Al ]: 0.04 to 0.06 percent;
an LF refining process;
vacuum treatment, after re-pressing, adding zirconium alloy to make Zr content in steel meet omega [ Zr ]: 0.0025% to 0.0050%, and [ omega ] Zr (0.2 x [ omega ] Al + 0.0005%); and
and (5) continuous casting.
6. The method of producing a Zr bearing steel according to claim 5, wherein,
in the vacuum treatment process, after the zirconium alloy is added, argon is introduced for stirring.
7. The method for producing the Zr-containing bearing steel according to claim 6, wherein the Zr content is in the range of the upper limit value,
when argon is introduced for stirring, the slag surface is shaken, but the molten steel is not exposed.
8. The method for producing the Zr-containing bearing steel according to claim 6, wherein the Zr content is in the range of the upper limit value,
and introducing argon gas for stirring for 25-30 minutes.
9. The method of producing a Zr bearing steel according to claim 5, wherein,
in the LF refining process, the slag components in the refining process are controlled to meet the following requirements: omega [ CaO]：50％～60％，ω[SiO2]：5％～10％，ω[Al2O3]：20％～30％，ω[MgO]：3％～10％，ω[CaF2]: 0.5 to 3 percent, and the amount of refining slag is 15 to 20kg per ton of steel.
10. The method of producing a Zr bearing steel according to claim 5, wherein,
in the continuous casting process, totally-enclosed protective pouring is adopted, and the superheat degree of molten steel is controlled to be 10-35 ℃.
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