CN-121992281-A - Low-titanium and low-oxygen smelting control method for high-grade bearing steel

CN121992281ACN 121992281 ACN121992281 ACN 121992281ACN-121992281-A

Abstract

The invention relates to the technical field of high-carbon chromium bearing steel smelting, and discloses a control method for low-titanium and low-oxygen smelting of high-grade bearing steel, which comprises the steps of S1 raw material pretreatment, S2 KR deep S removal treatment, S3 converter smelting, S4 LF refining, S5 VD/RH vacuum treatment, S6 continuous casting process and S7 process inspection and control, wherein the process realizes accurate and controllable Ti/O content, and meets the core requirements of special grade products: the low-Ti molten iron is strictly screened through raw material pretreatment, low-Ti auxiliary materials are selected, the slag is removed by matching with LF refining, slag skimming and slag dragging, the Ti-rich slag is removed, VD/RH vacuum strengthening deoxidation is effectively avoided, the Ti element is carried in and returned, the Ti content is stably controlled to be 0.0010% -0.0015%, the O content is accurately locked to be 0.0005% -0.00065%, the standard of special-grade products in the industry is far exceeded, the Ti/O hit rate is respectively improved to be more than 100% and 80%, and the pain point with large fluctuation of the Ti/O content in the traditional process is solved.

Inventors

Pan Xiquan
YUAN YUAN
YUAN LIN
WU MIN
ZHU JIANCHENG
LIU QING
WANG JUN
AN QIANG
HUANG ZHENHUA
LUO XIAO

Assignees

湖南华菱湘潭钢铁有限公司

Dates

Publication Date: 20260508
Application Date: 20260123

Claims (10)

1. A control method for low-titanium low-oxygen smelting of high-grade bearing steel comprises the steps of S1 raw material pretreatment, S2 KR deep S removal treatment, S3 converter smelting, S4 LF refining, S5 VD/RH vacuum treatment, S6 continuous casting technology and S7 process inspection and control, and is characterized in that the S1 raw material pretreatment comprises S101 molten iron control in a furnace and S102 auxiliary material selection; Wherein, the S4 LF refining comprises S401 slag skimming, S402 argon blowing deoxidization, S403 component fine adjustment and S404 final deoxidization treatment; Wherein, the S5 VD/RH vacuum treatment comprises S501 argon blowing control, S502 vacuum treatment, S503 temperature control and S504 gas control; The S6 continuous casting process comprises S601 protection casting, S602 crystallizer parameters, S603 reduction control and S604 casting blank treatment; Wherein, the S7 process inspection and control comprises S701 component detection, S702 casting blank quality inspection and S703 inclusion control.
2. The control method for low-titanium low-oxygen smelting of high-grade bearing steel, which is characterized in that S101 is added into molten iron for controlling [ S ] < 0.045% -0.055%, [ P ] < 0.140% -0.160%, ti < 0.05% -0.07%, and low-Ti molten iron raw materials are strictly screened to avoid bringing excessive Ti elements.
3. The low-titanium low-oxygen smelting control method for the high-grade bearing steel is characterized in that S102 auxiliary materials are selected from low-Ti alloy (low-carbon ferrochrome, low-aluminum low-titanium ferrosilicon and manganese), low-titanium low-boron premelted slag and drainage sand with excellent drainage effect, steel tanks for smelting Ti-containing steel types are forbidden to be used, slag along the tank is thoroughly cleaned before use, and a turnover tank or a special steel tank is preferably selected.
4. The control method for low-titanium and low-oxygen smelting of the high-grade bearing steel, which is characterized by comprising the following steps of: S removal, namely controlling molten steel [ S ] to be less than or equal to 0.002% -0.003%, reducing S removal load in subsequent LF refining, shortening refining time and reducing Ti element return risk in the refining process; the treatment parameters are that the stirring power is adapted according to the tonnage of molten steel, the stirring time is 30-45min, and the full contact reaction of the desulfurizing agent and the molten steel is ensured.
5. The control method for low-titanium and low-oxygen smelting of the superior bearing steel, which is disclosed in claim 1, is characterized in that the S3 converter smelting comprises the following steps: the tapping end point is controlled, namely, the end point [ C ] is 0.08-0.12%, so that the subsequent deoxidization difficulty increase caused by the peroxidation of molten steel is avoided; The slag stopping and tapping step is to adopt mechanical slag stopping and slag stopping agent to assist slag stopping, and prevent slag from bringing harmful impurities; The alloy is added, and the preset low Ti alloy and slag are added along the steel flow when tapping 1/4, and the entering component targets are [ C ] 0.82% -0.98%, [ Mn ] 0.22% -0.38% and [ Cr ] 1.32% -1.48%.
6. The control method for low-titanium low-oxygen smelting of high-grade bearing steel, as set forth in claim 1, wherein the S401 slag skimming and dragging step is performed after entering a station, and the Ti-rich slag on the surface of the molten steel is removed to reduce the Ti content of the molten steel; S402 argon blowing deoxidation, namely, performing diffusion deoxidation by adopting Al particles in 40-60min, and performing rapid slagging deoxidation and desulfurization by matching with low Ti synthetic slag, wherein the slagging time is controlled to be 20-30min; S403 component fine adjustment, namely precisely adjusting components according to target values, controlling 1.40% -1.65% of [ Cr ] and 0.94% -1.00% of out-coming [ C ], wherein the carbon quantity difference between an upper furnace and a lower furnace is less than or equal to 0.04%, and the Al content adjustment times are less than or equal to 1 time, so that the increase of inclusions caused by excessive Al is avoided; S404, final deoxidization treatment, namely throwing 5-15kg of aluminum powder to the slag surface for enhanced deoxidization when the molten steel comes out, and strictly prohibiting deoxidization or inclusion denaturation by adding Ca or Ca alloy.
7. The control method for low-titanium and low-oxygen smelting of the high-grade bearing steel, which is characterized in that the argon blowing control of S501 is that the total argon blowing time of a VD furnace is 50-70min, and the total argon blowing time of an RH furnace is 40-60min; S502, vacuum treatment, namely, vacuum degree is less than or equal to 67Pa, vacuum maintaining time is 15-25min, vacuum breaking is carried out, VD furnace soft argon blowing is carried out for 15-35min, RH furnace soft argon blowing is carried out for 15-30min, standing time is 10-25min, and floating of inclusions is promoted; S503, controlling the superheat degree of the molten steel outlet upper stage temperature, and starting a casting furnace at 18-38 ℃ and a continuous casting furnace at 12-32 ℃ (liquidus reference temperature 1450-1460 ℃); S504, controlling gas, namely extracting at least 1 furnace to detect [ H ] every casting time, controlling the [ H ] to be less than or equal to 1.2-1.5ppm, and adding a proper amount of heat preservation agent into the steel ladle when the steel ladle is out of the station.
8. The control method for low-titanium low-oxygen smelting of high-grade bearing steel, which is characterized in that S601 protection casting is performed by adopting special protection slag of carbonized rice hulls and high-carbon steel in the whole process, so that secondary oxidation of molten steel is prevented; S602, crystallizer parameters, namely 3200-4000L/min of crystallizer water quantity, 0.48-0.56m/min of pulling speed and 0.16-0.20L/kg of specific water quantity, 220-280A of electromagnetic stirring current of the crystallizer, 2.0-3.0Hz of frequency, 320-380A of tail end electromagnetic stirring current and 7.0-9.0Hz of frequency; s603, controlling the reduction, namely designing the reduction of 22-28mm, and improving the center segregation of the casting blank through heavy reduction; S604, casting blank treatment, namely, casting blank slow cooling time is more than or equal to 48-72h, the bottommost layer and the topmost layer are preferably insulated by adopting hot blanks, and casting blanks with the fluctuation of the liquid level of the crystallizer exceeding +/-4-6 mm are picked out and judged to be wasted.
9. The control method for low-titanium and low-oxygen smelting of high-grade bearing steel according to claim 1, wherein the component detection of S701 is characterized in that each heat is sampled and detected at the LF outlet, the VD/RH outlet and the casting blank stage, ti is controlled to be less than or equal to 0.0010% -0.0015%, and O is controlled to be less than or equal to 0.0005% -0.00065%; S702, performing quality inspection, namely taking samples covering all the flows every time, and performing low-power and segregation inspection, wherein the segregation index is required to be less than or equal to 1.05-1.08, and the defects of obvious center porosity and shrinkage cavity are avoided.
10. The control method for low-titanium low-oxygen smelting of high-grade bearing steel according to claim 1, wherein S703 inclusion control is performed by automatically analyzing and detecting the number and the size of the inclusions, ensuring that the inclusion size is more than or equal to 10 μm and less than or equal to 3% -5%, and avoiding the influence of large-particle inclusions on the steel.

Description

Low-titanium and low-oxygen smelting control method for high-grade bearing steel Technical Field The invention relates to the technical field of high-carbon chromium bearing steel smelting, in particular to a low-titanium and low-oxygen smelting control method for high-grade bearing steel. Background The GCr15 steel is used as a core brand of high-carbon chromium bearing steel, is widely applied to the field of high-end equipment such as automobile bearings, precision mechanical bearings and the like, and special grade products thereof have strict requirements on the control accuracy of Ti and O contents, the purity of steel, the uniformity of internal tissues and the surface quality. The production of special grade GCr15 steel in the industry generally faces multiple technical bottlenecks, namely Ti element is easily brought in through molten iron raw materials, alloy auxiliary materials and smelting equipment residues, a reversion phenomenon is easily generated in the refining process, so that the Ti content is difficult to control below 0.0015%, the total oxygen content is greatly influenced by a deoxidization process, a vacuum treatment effect and secondary oxidation, fluctuation is large, the O content of most steel plants is controlled in a range of 5-9ppm, the requirement that the special grade product is difficult to reach 6.5ppm is difficult to stably reach, the inclusion removal in the smelting process is incomplete, the large-size inclusion (more than or equal to 10 mu m) accounts for higher proportion, the quality objection such as bearing ring blackspot and cracking is easy to cause, the carbon segregation problem in the continuous casting process is prominent, the carbon segregation index is more than 1.10, the uniformity of the mechanical property of steel is influenced, and the surface defects (such as folding, cracking and scab) are frequent, so that the penetrating pipe outer wrapping, self-break of a coil rod and other clients restrict the application of the steel in the field of high-end bearing. Meanwhile, although the mainstream competitors have realized lower level control of the content of Ti and O, there is still room for improvement in the aspects of precise control of inclusions, optimization of carbon segregation and quality stability, and a set of smelting process capable of realizing precise control of the content of Ti/O and considering both purity and tissue uniformity is needed in the industry. Disclosure of Invention (One) solving the technical problems Aiming at the defects of the prior art, the invention provides a low-titanium low-oxygen smelting control method for high-grade bearing steel, which has the advantages of accurate and controllable Ti/O content, meeting the core requirements of high-grade products and the like, and solves the problems that Ti element is easily brought in through molten iron raw materials, alloy auxiliary materials and smelting equipment residues and a reversion phenomenon is easily generated in the refining process. (II) technical scheme The invention provides a control method for low-titanium and low-oxygen smelting of high-grade bearing steel, which aims to realize accurate and controllable Ti/O content and meet the core requirements of special grade products, and the technical scheme comprises the following steps of S1 raw material pretreatment, S2 KR deep S removal treatment, S3 converter smelting, S4 LF refining, S5 VD/RH vacuum treatment, S6 continuous casting process and S7 process inspection and control, wherein the S1 raw material pretreatment comprises S101 molten iron control and S102 auxiliary material selection; Wherein, the S4 LF refining comprises S401 slag skimming, S402 argon blowing deoxidization, S403 component fine adjustment and S404 final deoxidization treatment; Wherein, the S5 VD/RH vacuum treatment comprises S501 argon blowing control, S502 vacuum treatment, S503 temperature control and S504 gas control; The S6 continuous casting process comprises S601 protection casting, S602 crystallizer parameters, S603 reduction control and S604 casting blank treatment; Wherein, the S7 process inspection and control comprises S701 component detection, S702 casting blank quality inspection and S703 inclusion control. Preferably, the S101 molten iron is controlled by less than or equal to 0.045% -0.055% of [ S ] < 0.140% -0.160% of [ P ] < 0.05% -0.07% of Ti, and the low-Ti molten iron raw material is strictly screened to avoid bringing excessive Ti element. Preferably, the S102 auxiliary materials are selected from low Ti alloy (low carbon ferrochrome, low aluminum low titanium ferrosilicon and manganese), low titanium low boron premelted slag and drainage sand with excellent drainage effect, and steel tanks for smelting Ti-containing steel types are forbidden to be used, slag along the tank is thoroughly cleaned before use, and a turnover tank or a special steel tank is preferably selected. Preferably, the S2 KR deep S removal tre