A method for producing a low-titanium bearing steel

Abstract

The application relates to a production method of low-titanium bearing steel, and the chemical composition of the steel is as follows: C=0.95% to 1.05%, Si=0.15% to 0.35%, Mn=0.25 to 0.45%, Cr=1.40% to 1.65%, P<=0.025%, S<=0.020%, Ti<=0.0015%, and the balance is Fe and inevitable impurities; the BOF+LF+VD+CC smelting technology is adopted, the end-point C of the converter is greater than or equal to 0.15%, the slide plate is used to block the slag, the alloy is added in the tapping process, the low-basicity slag material is added after the furnace and is greater than or equal to 3 kg per ton of steel; the low-basicity slag is formed in the LF, the deoxidation operation is not carried out in the smelting process, the sampling Ti is less than or equal to 0.0008%, and the slag removing operation is carried out to ensure that the slag removing is clean; the aluminum wire deoxidation is fed after the slag removing to ensure that the Al of the molten steel is 0.040 to 0.060%, the lime and the low-titanium synthetic slag are added to form the high-basicity white slag to deoxidize and de-S, and the finished product bearing steel with Ti less than or equal to 0.0015% is successfully developed.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology and relates to a method for producing low-titanium bearing steel. Background Technology

[0002] With the rapid development of the equipment manufacturing industry, the use of bearings is increasing daily. Controlling the titanium content is crucial in modern bearing steel production, and is a core solution to the problems of short service life and poor structural quality in bearing steel. When the titanium content in bearing steel exceeds 50 ppm, its fatigue life begins to decline significantly. Reducing the Ti content in bearing steel is of great importance to improving its quality. The biggest technical challenge in smelting high-grade bearing steel lies in controlling the titanium content.

[0003] Chinese patent CN2015102531122, "A production method of low-titanium bearing steel GCr15", describes a smelting process that uses ordinary ferroalloys to smelt bearing steel, and can only control the titanium content to no more than 50 ppm.

[0004] According to the information published by Jiang Chengbin and Luo Hui in their article "Practice of Titanium Content Control in Wind Power Bearing Steel GCr15SiMn" in the 2015 Proceedings of the 10th China Iron and Steel Annual Conference and the 6th Baosteel Academic Annual Conference: by adopting high-cost titanium control measures such as controlling the titanium content of electric furnace steel, using low-titanium alloys in refining, using low-basicity refining slag, and rationally using deoxidizers, the titanium content of the produced wind power bearing steel GCr15SiMn was controlled below 20ppm, but bearing steel with Ti≤15ppm was not stably produced. Summary of the Invention

[0005] This invention aims to provide a method for producing low-titanium bearing steel. It uses ordinary alloys, employs LF (Lead-Fluidized Ladle) to produce low-basicity slag to control titanium content, and uses a slag removal process to remove titanium from the ladle top slag, reducing the need for subsequent high-basicity slag production to recover titanium. This method produces bearing steel with Ti≤15ppm, meeting the needs of high-standard bearing customers.

[0006] The technical solution of the present invention:

[0007] A method for producing low-titanium bearing steel, wherein the steel's chemical composition by weight percentage is C=0.95%~1.05%, Si=0.15%~0.35%, Mn=0.25%~0.45%, Cr=1.40%~1.65%, P≤0.025%, S≤0.020%, Ti≤0.0015%, with the balance being Fe and unavoidable impurities; key process steps include:

[0008] (1) Converter smelting: final C≥0.15%, converter slide plate slag blocking, adding SiMn and high carbon CrFe during tapping, no deoxidizer added, adding ≥3kg / ton of low basicity slag during tapping;

[0009] (2) Low-alkalinity slag composition: The composition of low-alkalinity slag is controlled as follows: CaO = 39.0%~46.0%, SiO2 = 46.0%~54.0%, MgO ≤ 3.0%, Al2O3 ≤ 2.0%, TiO2 ≤ 0.02%, T.Fe ≤ 1.0%;

[0010] (3) LF slag removal operation: When molten steel enters the station, it is slag-forming by electric current and stirred with a small amount of argon gas. No deoxidizer or alloy is added during the smelting process. After sampling Ti≤0.0008%, the slag removal operation is carried out and the slag is removed cleanly.

[0011] (4) LF deoxidation and desulfurization operation; after slag removal, feed aluminum wire for deoxidation to ensure that Al=0.040~0.060% in the molten steel, add lime and low titanium synthetic slag to make high basicity white slag for deoxidation and desulfurization;

[0012] (5) Component testing: Take a sample from the middle package and analyze its components.

[0013] The beneficial effects of this invention are as follows: This invention uses ordinary alloys and combines BOF+LF+VD+CC smelting technology, which reduces production costs. The converter does not require deoxidation, and low-basicity slag is added during the tapping process. Low-basicity slag is generated in the early stage of LF refining, controlling the Ti content in the molten steel to ≤0.0008%. High-titanium, low-basicity refining slag is removed to prevent the return of titanium during subsequent high-basicity, low-oxidizing slag formation, thus reducing the titanium content in the molten steel. The low-basicity slag control range is: CaO=39.0%~46.0%, SiO2=46.0%~54.0%, MgO≤3.0%, Al2O3≤2.0%, TiO2≤0.02%, T.Fe≤1.0%. Detailed Implementation

[0014] The present invention will be further described below with reference to embodiments:

[0015] Example 1:

[0016] A method for producing low-titanium bearing steel includes the following steps:

[0017] (1) Converter smelting: The steel tapping temperature of the converter is 0.2181%, and the slag is blocked by the sliding plate. During the tapping process, 341 kg SiFe, 404 kg high carbon MnFe, 3928 kg high carbon CrFe and 412 kg low basicity slag are added.

[0018] (2) Low alkalinity slag composition: CaO=43.48%, SiO2=50.76%, MgO=2.94%, Al2O3=1.82%, TiO2=0.017%, T.Fe=0.79%.

[0019] (3) LF slag removal operation: LF furnace refining is powered on for 10 minutes, and the Ti in the molten steel is sampled and analyzed to be 0.0007%. Slag removal operation is then performed.

[0020] (4) LF deoxidation and desulfurization operation: After slag removal, feed 320 meters of aluminum wire for deoxidation to ensure that the Al of the molten steel is 0.0452%. Add 805 kg of lime and 1322 kg of low titanium synthetic slag to make high alkalinity white slag for deoxidation and desulfurization.

[0021] (5) Composition test: Take a sample from the tundish. The composition analysis of the steel is C=0.9765%, Si=0.1735%, Mn=0.2645%, Cr=1.465%, P=0.0152%, S=0.0027%, Ti=0.0012%.

[0022] Example 2:

[0023] A method for producing low-titanium bearing steel includes the following steps:

[0024] (1) Converter smelting: The steel tapping temperature of the converter is 0.1741%, and the slag is blocked by the sliding plate. During the tapping process, 337kg SiFe, 386kg high carbon MnFe, 3934kg high carbon CrFe and 455kg low basicity slag are added.

[0025] (2) Low alkalinity slag composition: CaO=43.18%, SiO2=50.87%, MgO=2.41%, Al2O3=2.43%, TiO2=0.015%, T.Fe=0.87%.

[0026] (3) LF slag removal operation: LF furnace refining is powered on for 8 minutes, and the Ti in the molten steel is sampled and analyzed to be 0.0005%. Slag removal operation is then performed.

[0027] (4) LF deoxidation and desulfurization operation: After slag removal, feed 350 meters of aluminum wire for deoxidation to ensure that the Al of the molten steel is 0.0448%. Add 812 kg of lime and 1318 kg of low titanium synthetic slag to make high-alkalinity white slag for deoxidation and desulfurization.

[0028] (5) Composition test: Take a sample from the middle package and analyze the composition: C=0.9805%, Si=0.1935%, Mn=0.2824%, Cr=1.458%, P=0.0128%, S=0.0024%, Ti=0.0010%.

[0029] Example 3:

[0030] A method for producing low-titanium bearing steel includes the following steps:

[0031] (1) Converter smelting: The steel tapping temperature of the converter is C=0.2548%, and the slag is blocked by the sliding plate. During the tapping process, 299kg SiFe, 332kg high carbon MnFe, 3696kg high carbon CrFe and 448kg low basicity slag are added.

[0032] (2) Low alkalinity slag composition: CaO=43.46%, SiO2=50.42%, MgO=2.69%, Al2O3=1.78%, TiO2=0.017%, T.Fe=0.68%.

[0033] (3) LF slag removal operation: LF furnace refining is powered on for 7 minutes, and the Ti in the molten steel is sampled and analyzed to be 0.0005%. Slag removal operation is then performed.

[0034] (4) LF deoxidation and desulfurization operation: After slag removal, feed 360 meters of aluminum wire for deoxidation to ensure that the Al of the molten steel is 0.0524%. Add 826 kg of lime and 1334 kg of low titanium synthetic slag to make high-alkalinity white slag for deoxidation and desulfurization.

[0035] (5) Composition inspection: Take a sample from the tundish. The chemical composition of the steel is C=1.051%, Si=0.1932%, Mn=0.3542%, Cr=1.457%, P=0.0118%, S=0.0024%, Ti=0.0009%.

Claims

1. A method for producing low-titanium bearing steel, characterized in that: The chemical composition of the steel by weight percentage is C=0.95%~1.05%, Si=0.15%~0.35%, Mn=0.25%~0.45%, Cr=1.40%~1.65%, P≤0.025%, S≤0.020%, Ti≤0.0015%, with the balance being Fe and unavoidable impurities; Key process steps include: (1) Converter smelting: final C≥0.15%, converter slide plate slag blocking, adding SiMn and high carbon CrFe during tapping, no deoxidizer added, adding ≥3kg / ton of low basicity slag during tapping; (2) Low-alkalinity slag composition: The low-alkalinity slag composition is CaO=39.0%~46.0%, SiO2=46.0%~54.0%, MgO≤3.0%, Al2O3≤2.0%, TiO2≤0.02%, T.Fe≤1.0%; (3) LF slag removal operation: When molten steel enters the station, it is slag-forming by electric current and stirred with a small amount of argon gas. No deoxidizer or alloy is added during the smelting process. After sampling Ti≤0.0008%, the slag removal operation is carried out and the slag is removed cleanly. (4) LF deoxidation and desulfurization operation; after slag removal, feed aluminum wire for deoxidation to ensure that Al=0.040~0.060% in the molten steel, add lime and low titanium synthetic slag to make high basicity white slag for deoxidation and desulfurization; (5) Component testing: Take a sample from the middle package and analyze its components.