Production method of bearing steel wire rod for rolling body with long cycle fatigue life

Abstract

The invention relates to a production method of a bearing steel wire rod for a rolling body with long cycle fatigue life, the steel comprises the following chemical components in percentage by weight: 0.95-1.05% of C, 0.15-0.35% of Si, 0.25-0.45% of Mn, 1.40-1.65% of Cr, 0.15-0.25% of Mo, 0.25-0.35% of V, less than or equal to 0.012% of P, less than or equal to 0.003% of S, less than or equal to 0.0005% of O, less than or equal to 0.0002% of Ca, less than or equal to 0.0015% of Ti, 0.010-0.020% of Al, less than or equal to 0.0030% of N, less than or equal to 0.030% of Ni, less than or equal to 0.030% of Cu, less than or equal to 0.0050% of As, less than or equal

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy and relates to a production method of a bearing steel wire rod for a high cycle fatigue life rolling element. Background Art

[0002] Bearing steel is known as the "king of steel" and is the most demanding type of steel in steel production. With the rapid development of green high-end manufacturing equipment such as new energy vehicles, high-speed railways and robots, bearings are required to have longer service life, higher reliability and higher Dn value and other service performance, which puts forward more stringent requirements on the metallurgical quality stability and fatigue resistance of high-quality bearing steel. At present, there is still a significant gap between the service life and comprehensive performance of high-quality bearing steel used in domestic high-end manufacturing equipment and foreign countries. It is still heavily dependent on imports and is subject to foreign advanced companies such as Timken in the United States and SKF in Sweden. Summary of the invention

[0003] To achieve the above-mentioned purpose, the present invention provides a method for producing a bearing steel wire rod for a rolling element with a high cycle fatigue life, which solves the problems existing in the prior art.

[0004] The technical solution of the present invention:

[0005] A method for producing a bearing steel wire rod for a rolling element with a high cycle fatigue life, wherein the chemical composition of the steel is as follows by weight: C: 0.95%-1.05%, Si: 0.15%-0.35%, Mn: 0.25%-0.45%, Cr: 1.40%-1.65%, Mo: 0.15%-0.25%, V: 0.25%-0.35%, P≤0.012%, S≤0.003%, O≤0.0005%, Ca≤0.0002%, Ti≤0.0015%, Al: 0.010%-0.020%, N≤0.0030%, Ni≤0.030%, Cu≤0.030%, As≤0.0050%, Pb≤0.0005%, Sn≤0.0030%, Sb≤0.0006%, and the rest is Fe and unavoidable impurities;

[0006] The wire rod specification is Ф5.0-25.0mm; it undergoes blast furnace ironmaking → molten iron pretreatment → converter steelmaking → LF refining → VD refining → continuous casting (350mm*430mm large square billet) → large square billet insulation pit high temperature stack cooling for 48 hours → billet opening (180mm*180mm) → shot blasting → billet grinding → anti-decarburization coating → high-speed hot rolling → Stelmor controlled cooling → insulation corridor insulation slow cooling, which further improves the contact fatigue life of high carbon chromium bearing steel, L 10 Can reach 1.0×10 8 More than times.

[0007] Furthermore, the converter final carbon is ≥0.25%, and slag blocking operation is adopted.

[0008] Furthermore, the LF refining process and the VD refining process use low-titanium and low-basicity special synthetic slag for refining, the LF refining performs slag removal operation, and nano-SiC particles are added to the LF and VD refining slag surface.

[0009] Furthermore, the large square billet is subjected to high temperature diffusion at 1220-1240°C for 350-400 minutes, and the high temperature diffusion at 1210-1240°C for 60-70 minutes during high-speed wire heating; the two high temperature diffusions control carbides and improve the contact fatigue life of high carbon bearing steel.

[0010] Furthermore, the anti-decarburization coating controls the decarburization of the wire rod, with the total decarburization being 0 and the partial decarburization layer being ≤0.02mm, thereby improving the contact fatigue life of the high carbon bearing steel.

[0011] Preferably, the low titanium and low basicity special synthetic slag is a synthetic refined slag with low titanium content and low basicity, and its main components are SiO 2 、CaO、MgO、Al 2 O 3 , Fe 2 O 3 , where Ti content is ≤0.001%.

[0012] The chemical composition design idea of ​​the present invention is as follows: adding microalloying elements Mo and V to high carbon chromium bearing steel, refining the matrix structure of high carbon bearing steel, and improving the contact fatigue life of high carbon bearing steel; controlling O≤0.0005%, Ti≤0.0015%, reducing and controlling inclusions in bearing steel, and improving the contact fatigue life of high carbon bearing steel.

[0013] Bloom opening, casting grinding and shot blasting can control the surface quality of steel billets, eliminate microscopic defects on the surface of materials, and improve the contact fatigue life of high carbon bearing steel.

[0014] Principle of the invention: Adjust the composition of the existing GCr15 steel, alloy Mo and V, refine the grains, enhance wear resistance, improve toughness and hardenability; control the content of O and Ti, reduce the number of inclusions, and reduce the size of inclusions; slowly cool the large square billet to eliminate the internal stress of the large square billet, further release the gas, and improve the internal quality of the large square billet; open the large square billet to increase the compression ratio and improve the internal density of the steel; shot blasting, flaw detection and grinding of the square billet to ensure the surface quality of the square billet; anti-decarburization coating to control the decarburization of the wire rod surface; by controlling the internal quality, surface quality and alloying of the material, the contact fatigue life of the high carbon chromium bearing steel is further improved, L 10 Can reach 1.0×10 8 More than times.

[0015] The beneficial effects of the present invention are as follows: The present invention further improves the contact fatigue life of high carbon chromium bearing steel, L 10 Reach 1.0×10 8 More than times. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 This is a diagram of inclusions in Example 1;

[0018] Figure 2 This is a low-magnification tissue diagram of Example 1;

[0019] Figure 3 This is a diagram showing the results of the lysis of Example 1;

[0020] Figure 4 This is a diagram of the decarburized layer of Example 1;

[0021] Figure 5 This is a diagram of inclusions in Example 2;

[0022] Figure 6 This is a low-magnification tissue diagram of Example 2;

[0023] Figure 7 This is a diagram showing the results of the lysis of Example 2;

[0024] Figure 8 This is a diagram of the decarburized layer in Example 2. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The present invention will be further described below in conjunction with the embodiments.

[0027] Embodiment 1:

[0028] The invention discloses a method for producing a bearing steel wire rod for a rolling element with a high cycle fatigue life. The chemical composition of the steel is as follows: C: 0.98%, Si: 0.25%, Mn: 0.36%, Cr: 1.48%, Mo: 0.20%, V: 0.28%, P: 0.012%, S: 0.002%, O: 0.0004%, Ca: 0.0002%, Ti: 0.0012%, Al: 0.012%, N: 0.0028%, Ni: 0.012%, Cu: 0.022%, As: 0.0023%, Pb: 0.0004%, Sn: 0.0025%, Sb: 0.0004%, and the rest is Fe and unavoidable impurities. The wire rod specification is Ф25.0mm; it undergoes blast furnace ironmaking → molten iron pretreatment → converter steelmaking → LF refining → VD refining → continuous casting (350mm*430mm large square billet) → large square billet insulation pit high temperature stack cooling for 48 hours → billet opening (180mm*180mm) → shot blasting flaw detection → billet grinding → anti-decarburization coating → high-speed wire hot rolling → Stelmor controlled cooling → insulation corridor insulation slow cooling, which further improves the contact fatigue life of high carbon chromium bearing steel, L 10 Can reach 1.0×10 8 More than times. Including the following key process steps:

[0029] (1) The final carbon content of the converter is 0.26%, and slag blocking operation is adopted;

[0030] (2) The LF refining process and the VD refining process use low-titanium and low-basicity special synthetic slag for refining, and the slag removal operation is carried out in the LF. Nano-SiC particles are added to the LF and VD refining slag surface to control O: 0.0004%, Ti: 0.0012%.

[0031] (3) The large square billet is opened and the high temperature diffusion is carried out at 1220-1240℃ for 360 minutes and the high temperature diffusion is carried out at 1210-1230℃ for 70 minutes to refine the high carbon bearing steel matrix structure. Figure 2 As shown, the central looseness is 0.5 level, the general looseness is 0.5 level, the ingot segregation is 0.5 level, and the central segregation is 0.5 level, which improves the contact fatigue life of high carbon bearing steel; Figure 3 As shown, the carbide detection level is 0 for liquid separation and 0.5 for banding, which improves the contact fatigue life of high carbon bearing steel.

[0032] (4) Billet opening: 350mm*430mm→180mm*180mm, 180mm*180mm billet grinding and shot blasting. Billets that fail the flaw detection are selected for re-evaluation. The surface quality of the billet is controlled and microscopic defects on the surface of the material are eliminated. The metallographic detection of Ф25.0mm wire rod shows no microscopic defects, thereby improving the contact fatigue life of high carbon bearing steel.

[0033] (5) 180mm*180mm ingot is coated with anti-decarburization coating to control the decarburization of wire rod, such as Figure 4 As shown, the full decarburization is 0 and the partial decarburization layer is 0.02 mm, which improves the contact fatigue life of high carbon bearing steel.

[0034] like Figure 1 As shown, the inclusion detection ratings of A, B, C, and D are 0, and Ds is 0.5, which improves the contact fatigue life of high carbon bearing steel.

[0035] The contact fatigue life and contact fatigue performance of bearing steel are tested by rolling contact fatigue testing machine. 10 1.2×10 8 Second-rate.

[0036] Embodiment 2:

[0037] The invention discloses a production method of a bearing steel wire rod for a rolling element with a high cycle fatigue life. The chemical composition of the steel is as follows: C: 0.99%, Si: 0.28%, Mn: 0.39%, Cr: 1.55%, Mo: 0.22%, V: 0.26%, P: 0.011%, S: 0.002%, O: 0.00038%, Ca: 0.00017%, Ti: 0.0010%, Al: 0.015%, N: 0.0026%, Ni: 0.013%, Cu: 0.020%, As: 0.0021%, Pb: 0.0004%, Sn: 0.0022%, Sb: 0.0004%, and the rest is Fe and unavoidable impurities. The wire rod specification is Ф8.0mm; it undergoes blast furnace ironmaking → hot metal pretreatment → converter steelmaking → LF refining → VD refining → continuous casting (350mm*430mm large square billet) → large square billet insulation pit high temperature stack cooling for 48 hours → billet opening (180mm*180mm) → shot blasting → billet grinding → anti-decarburization coating → high-speed hot rolling → Stelmor controlled cooling → insulation corridor insulation slow cooling, which further improves the contact fatigue life of high carbon chromium bearing steel, L 10 Can reach 1.0×10 8 More than times. The process includes the following steps:

[0038] (1) The final carbon content of the converter is 0.28%, and slag blocking operation is adopted;

[0039] (2) The LF refining process and the VD refining process use low-titanium and low-basicity special synthetic slag for refining, and the slag removal operation is carried out in the LF. Nano-SiC particles are added to the LF and VD refining slag surfaces to control O: 0.00038%, Ti: 0.0010%.

[0040] (3) The large square billet is heated to 1220-1240℃ for 380 minutes and the high-speed wire is heated to 1220-1240℃ for 65 minutes to refine the high-carbon bearing steel matrix structure, such as Figure 6 As shown, the central looseness is 0.5 level, the general looseness is 0.5 level, the ingot segregation is 0.5 level, and the central segregation is 0.5 level, which improves the contact fatigue life of high carbon bearing steel; Figure 7 As shown, the carbide detection level is 0 for liquid separation and 0.5 for banding, which improves the contact fatigue life of high carbon bearing steel.

[0041] (4) Billet opening: 350mm*430mm→180mm*180mm, 180mm*180mm billet grinding and shot blasting, billets that fail the flaw detection are selected for re-judgment, the surface quality of the billets is controlled, and microscopic defects on the surface of the material are eliminated. The metallographic detection of Ф25.0mm wire rod shows microscopic defects of 0.01mm, which improves the contact fatigue life of high carbon bearing steel.

[0042] (5) 180mm*180mm ingot is coated with anti-decarburization coating to control the decarburization of wire rod, such as Figure 8 As shown, the full decarburization is 0 and the partial decarburization layer is 0.03mm, which improves the contact fatigue life of high carbon bearing steel.

[0043] like Figure 4 As shown, the inclusion detection ratings of A, B, C, and D are 0, and Ds is 0.5, which improves the contact fatigue life of high carbon bearing steel.

[0044] The contact fatigue life and contact fatigue performance of bearing steel are tested by rolling contact fatigue testing machine. 10 1.5×10 8 Second-rate.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A method for producing a bearing steel wire rod for a rolling element with a high cycle fatigue life, characterized in that: The chemical composition of the steel is as follows: C: 0.95% ~ 1.05%, Si: 0.15% ~ 0.35%, Mn: 0.25% ~ 0.45%, Cr: 1.40% ~ 1.65%, Mo: 0.15% ~ 0.25%, V: 0.25% ~ 0.35%, P ≤ 0.012%, S ≤ 0.003%, O ≤ 0.0005%, Ca ≤ 0.0002%, Ti ≤ 0.0015%, Al: 0.010% ~ 0.020%, N ≤ 0.0030%, Ni ≤ 0.030%, Cu ≤ 0.030%, As ≤ 0.0050%, Pb ≤ 0.0005%, Sn ≤ 0.0030%, Sb ≤ 0.0006%, and the rest is Fe and unavoidable impurities; The wire rod specification is Ф5.0-25.0mm, and it goes through blast furnace ironmaking → hot metal pretreatment → converter steelmaking → LF refining → VD refining → 350mm*430mm large square billet continuous casting → large square billet insulation pit high temperature pile cooling for 48 hours → 180mm*180mm billet opening → shot blasting flaw detection → billet grinding → anti-decarburization coating → high-speed wire hot rolling → Stelmor controlled cooling → insulation corridor insulation slow cooling, the contact fatigue life of bearing steel is L 10 Reach 1.0×10 8 More than times.

2. The method for producing a bearing steel wire rod for a rolling element with a high cycle fatigue life as claimed in claim 1, characterized in that: The final carbon content of the converter is ≥0.25%, and slag blocking operation is adopted.

3. The method for producing a bearing steel wire rod for a rolling element with a high cycle fatigue life as claimed in claim 1, characterized in that: The LF refining process and the VD refining process use low-titanium and low-basicity special synthetic slag for refining and covering. LF refining performs slag stripping operation, and nano-SiC particles are added to the slag surface of LF and VD refining.

4. The method for producing a bearing steel wire rod for a rolling element with a high cycle fatigue life as claimed in claim 1, characterized in that: The large square billet is subjected to high temperature diffusion at 1220-1240℃ and kept warm for 350-400 minutes, and the high temperature diffusion at 1210-1240℃ and kept warm for 60-70 minutes during high-speed wire heating.

5. The method for producing a bearing steel wire rod for a rolling element with a high cycle fatigue life as claimed in claim 1, characterized in that: The anti-decarburization coating controls the decarburization of the wire rod, with the total decarburization being 0 and the partial decarburization layer being ≤0.02mm, thereby increasing the contact fatigue life of the high carbon bearing steel.

6. The method for producing a bearing steel wire rod for a rolling element with a high cycle fatigue life as claimed in claim 3, characterized in that: The low-titanium and low-basicity special synthetic slag is a synthetic refined slag with low titanium content and low basicity, and its main components are SiO2, CaO, MgO, Al2O3, and Fe2O3, wherein the Ti content is ≤0.001%.

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