Production method of low-cost carbon spiral spring steel wire rod

Abstract

The invention discloses a production method of a low-cost carbon spiral spring steel wire rod, the chemical components of the steel grade do not contain precious alloy elements, the production process comprises the steps of converter top and bottom combined blowing smelting, LF refining, 6 # small square billet continuous casting, slow cooling and rolling in a wire factory, and the use requirements of users can be met without VD refining furnace production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metallurgical industrial production of metal materials and steelmaking, and particularly relates to a production method of low-cost carbon spiral spring steel wire rod. BACKGROUND

[0002] 65Mn wire rod is generally used for manufacturing mechanical springs after drawing. The traditional method needs lead quenching before manufacturing the spring. Through the quenching process, the wire rod can obtain a sorbite (fine pearlite) metallographic structure, thereby obtaining good comprehensive mechanical properties: i.e. tensile strength ≥ 1050 MPa, and reduction of area ≥ 36%. Only with such metallographic structure and mechanical properties, the 65Mn wire rod can not break during spring bending and has long fatigue life and good comprehensive mechanical properties of the spring. Since the high-speed wire rod mill is equipped with an advanced Stelmor controlled cooling line, if the controlled cooling process parameters are properly selected, the wire rod can obtain good metallographic structure and high strength and toughness, so that the lead bath quenching before manufacturing the spring can be cancelled, thereby reducing the production cost.

[0003] According to the patent "Suspension spring, spring steel wire rod and preparation method thereof" (Application Publication No. CN 118109740 A) applied by Yang Xiaowei et al. of Shagang Iron and Steel Research Institute Co., Ltd. on May 31, 2024, the invention relates to a suspension spring, spring steel wire rod and a preparation method thereof. The method includes (1) steelmaking, the molten steel contains C 0.48-0.55%, Si 1.55-1.65%, Mn 0.75-0.85%, Cr 0.65-0.75%, Cu ≤ 0.04%, Al ≤ 0.005%, the balance of Fe and impurities, and at least one of Nb 0.05-0.10%, V 0.10-0.15%, Mo 0.07-0.12%, and Ni 0.12-0.16%; (2) continuous casting; (3) cogging; (4) flaw detection; and (5) spraying anti-decarburization coating. The production process is different from the present method.

[0004] According to the patent "1100MPa Si-Cr spring steel wire rod and controlled rolling and controlled cooling method" (application publication number CN 118007033 A) applied by Peng Mengdu of Jiangsu Yonggang Group Co., Ltd. on May 10, 2024, the invention relates to a 1100MPa Si-Cr spring steel wire rod and a controlled rolling and controlled cooling method. The spring steel wire rod adopts a carbon reduction and Mo and Nb carbon fixation component design, combined with heating furnace heating, high line controlled rolling and controlled cooling, and online molten salt controlled cooling technology to effectively control decarburization throughout the process, so that the decarburization layer depth is ≤0.4% D. Large reduction is used to induce NbC precipitation to refine grains. Large supercooling degree is formed at low temperature before online molten salt controlled cooling treatment to promote the refinement of sorbite lamella spacing. The temperature is raised after the online molten salt controlled cooling treatment to promote the homogenization and toughening of the structure. The chemical composition of the steel grade is different from that of the present invention.

[0005] According to the patent "Rolling method of high-strength automobile spring steel wire rod" (application publication number CN 111530925 A) applied by Qin Shuchao of Xingtai Iron and Steel Co., Ltd. on August 11, 2020, the control rolling process is controlled. The temperature of the wire rod entering the finishing rolling is 926-980℃, and the wire laying temperature is 938-950℃. The controlled cooling process is to cool the wire rod to 780℃ after wire laying, and the controlled cooling speed C1 is 5.0-10.0℃ / s. The wire rod is cooled from 780℃ to 600℃ at an average cooling speed C2 of 0.5-4.0℃ / s. The high-strength automobile spring steel wire rod has the following chemical composition and weight percentage: C 0.51%-0.64%, Si 1.20%-2.00%, Mn 0.60%-0.90%, P≤0.025%, S≤0.025%, Cr≤0.80%, and the rest is Fe and unavoidable impurity elements. The chemical composition of the steel grade is different from that of the present invention. SUMMARY

[0006] The present invention aims to provide a low-cost carbon spiral spring steel wire rod production method, which does not contain valuable alloy elements in its chemical composition, and its production process is: converter top and bottom combined blowing smelting-LF refining-6# small billet continuous casting-cold rolling-rolling mill, which can meet the user's requirements without VD refining furnace, thus reducing the production cost. The specific technical scheme is as follows.

[0007] One aspect of the present invention provides a low-cost carbon spiral spring steel wire rod production method, which includes the following process steps: converter top and bottom combined blowing smelting-LF refining-6# small billet continuous casting-cold rolling-rolling mill, wherein the low-cost carbon spiral spring steel wire rod is produced without VD refining furnace in the smelting process, and the chemical composition of the low-cost carbon spiral spring steel wire rod is: C: 0.62-0.67%, Si: 0.17-0.27%, Mn: 0.90-1.00%, P≤0.030%, S≤0.030%, and the balance is Fe and impurities.

[0008] In some embodiments, the low-cost carbon spiral spring steel wire rod has a chemical composition of: C: 0.65-0.66%, Si: 0.21-0.23%, Mn: 0.96-0.98%, P≤0.020%, S≤0.015%, and the balance of Fe and impurities.

[0009] In some embodiments, the converter adopts a high carbon pulling process, the tapping endpoint composition is C≥0.15%, P≤0.020%, S≤0.015%, the temperature range is 1630-1660℃, the converter tapping alloying adds a low-nitrogen carbon additive + ferrosilicon + silicon manganese (ferromanganese); the tapping blocks the slag, the LF ladle refining is operated according to the refining procedure throughout the whole process, the foaming slag is generated and Ar is blown, the refining slag basicity is controlled at 2.5, and the nitrogen content in the steel is controlled at ≤40×10 -6 .

[0010] In some embodiments, in the 6# small billet continuous casting process, the overheating degree of the molten steel is controlled in the range of 15-30℃, the withdrawal speed of the billet is controlled in the range of 3.1-3.3m / min, and the high withdrawal speed is used to reduce the production cost.

[0011] In some embodiments, in the wire mill rolling process, the opening rolling temperature of the billet is controlled at 1150-1180℃, the finish rolling temperature is 880℃, and the wire rod laying temperature is 860-870℃.

[0012] In some embodiments, the low-cost carbon spiral spring steel wire rod has mechanical properties of: tensile strength of 1050-1150MPa, and reduction of area of 36-42%.

[0013] Another aspect of the present application provides a low-cost carbon spiral spring steel wire rod obtained by the above production method.

[0014] The present application has the advantage of producing carbon spring steel by a low-cost method, which can meet the user's requirements without VD refining furnace production. DETAILED DESCRIPTION

[0015] The content of the present application is described in detail through specific examples below, and the examples are intended to help understand the present application, but not to limit the content of the present application.

[0016] Example 1

[0017] The chemical composition of the steel grade is as follows: C: 0.66%, Si: 0.21%, Mn: 0.96%, P: 0.020%, S: 0.015%, and the balance of Fe and impurities.

[0018] The production process is: converter top and bottom combined blowing smelting-LF refining-6# small billet continuous casting-slow cooling-wire mill rolling.

[0019] Converter adopts high carbon process, the end of tapping composition C: 0.21%, P: 0.011%, S≤0.009%, temperature: 1645℃, converter tapping alloying adding low nitrogen carbon additive + silicon iron + silicon manganese (manganese iron). Tapping slag, LF ladle refining whole process according to the refining procedure to make foam slag and blow Ar operation, refining slag basicity is 2.4 control, nitrogen content in steel: 36×10 -6 The molten steel is directly produced to the casting machine without VD furnace.

[0020] The superheat of the molten steel is within the range of 26℃, the speed of the billet is controlled within the range of 3.2m / min, and the high speed is used to reduce the production cost.

[0021] The opening rolling temperature of the billet is controlled to be 1180℃, the final rolling temperature is 880℃, and the wire rod drawing temperature is 865℃.

[0022] The mechanical properties of the low-cost carbon spiral spring steel wire rod meet: the tensile strength is 1150MPa, and the reduction of area is 39%.

[0023] Example 2

[0024] The chemical composition of the steel grade is as follows: C: 0.65%, Si: 0.23%, Mn: 0.98%, P: 0.018%, S: 0.013%, and the balance is Fe and impurities.

[0025] The production process is: converter top and bottom combined blowing smelting-LF refining-6# small billet continuous casting-slow cooling-wire rod mill rolling.

[0026] Converter adopts high carbon process, the end of tapping composition C: 0.25%, P: 0.010%, S≤0.008%, temperature: 1648℃, converter tapping alloying adding low nitrogen carbon additive + silicon iron + silicon manganese (manganese iron). Tapping slag, LF ladle refining whole process according to the refining procedure to make foam slag and blow Ar operation, refining slag basicity is 2.6 control, nitrogen content in steel: 32×10 -6 The molten steel is directly produced to the casting machine without VD furnace.

[0027] The superheat of the molten steel is within the range of 28℃, the speed of the billet is controlled within the range of 3.3m / min, and the high speed is used to reduce the production cost.

[0028] The opening rolling temperature of the billet is controlled to be 1180℃, the final rolling temperature is 880℃, and the wire rod drawing temperature is 870℃.

[0029] The mechanical properties of the low-cost carbon spiral spring steel wire rod meet: the tensile strength is 1090MPa, and the reduction of area is 38%.

[0030] Finally, it should be noted that the above description is only the preferred embodiments of the present application, and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art will appreciate that modifications can be made to the technical solutions described in the foregoing embodiments, or some of the technical features thereof can be replaced by equivalent features. Any modifications, equivalent replacements, improvements, 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

1. A method for producing low-cost carbon coil spring steel wire rod, characterized in that: The production method includes the following process steps: converter top and bottom blowing smelting - LF refining - 6# small square billet continuous casting - slow cooling - wire rod mill rolling, wherein the smelting process does not pass through a VD refining furnace, and the chemical composition of the low-cost carbon coil spring steel wire rod is: C: 0.62-0.67%, Si: 0.17-0.27%, Mn: 0.90-1.00%, P≤0.030%, S≤0.030%, and the balance is Fe and impurities.

2. The production method according to claim 1, characterized in that The chemical composition of the low-cost carbon coil spring steel wire rod is: C: 0.65-0.66%, Si: 0.21-0.23%, Mn: 0.96-0.98%, P≤0.020%, S≤0.015%, and the balance is Fe and impurities.

3. The production method according to claim 1 or 2, characterized in that The converter adopts high carbon drawing process, with the final composition of steel being C ≥ 0.15%, P ≤ 0.020%, and S ≤ 0.015%. The temperature range is 1630-1660℃. Low nitrogen carburizer, ferrosilicon, and silicomanganese (ferromanganese) are added to the converter steel alloying process. Slag is blocked during tapping. The LF ladle refining process is carried out according to the refining regulations to make foam slag and blow Ar. The basicity of the refined slag is controlled at 2.5, and the nitrogen content in the steel is controlled to be ≤ 40×10 -6 .

4. The production method according to claim 1 or 2, characterized in that In the 6# billet continuous casting process, the superheat of the molten steel is controlled within the range of 15-30°C, and the billet drawing speed is controlled within the range of 3.1-3.3m / min. A high drawing speed is used to reduce production costs.

5. The production method according to claim 1 or 2, characterized in that In the rolling process of the wire rod mill, the starting rolling temperature of the steel billet is controlled at 1150-1180℃, the final rolling temperature is 880℃, and the wire drawing temperature is 860-870℃.

6. The production method according to claim 1 or 2, characterized in that The mechanical properties of the low-cost carbon coil spring steel wire rod meet the following requirements: tensile strength of 1050-1150 MPa and section shrinkage of 36-42%.

7. A low-cost carbon coil spring steel wire rod, obtained by the production method according to any one of claims 1 to 6.