Preparation method of high-carbon hard wire steel

Abstract

The invention discloses a preparation method of high-carbon hard wire steel, and belongs to the technical field of ferrous metallurgy. The method comprises the steps of molten iron pre-desulfurization, converter smelting, LF furnace refining and small square billet casting machine continuous casting. The high-carbon hard wire steel comprises the following chemical components in percentage by mass: 0.76 to 0.80 percent of C, 0.20 to 0.35 percent of Si, 0.65 to 0.80 percent of Mn, 0.18 to 0.22 percent of Cr, less than or equal to 0.020 percent of P, less than or equal to 0.015 percent of S and the balance of Fe and inevitable impurities. According to the preparation method of the high-carbon hard wire steel, the high-carbon hard wire steel is produced through one-time heating of the small square billet, and the preparation method has the advantages of being short in production period, high in production efficiency, low in production cost and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel metallurgy, and particularly relates to a preparation method of high-carbon hard wire steel. BACKGROUND

[0002] The high-carbon hard wire steel is widely used, and is mainly used for manufacturing high-strength low-relaxation prestressed smooth steel wires, notch steel wires, female thread steel wires and steel strands of various specifications and grades, which are applied to various fields such as railway sleepers, highways, bridges, urban overpasses, large cement water pipes, high-rise anti-seismic buildings and mine supports. The high-carbon hard wire steel is required to have excellent metallurgical quality, stable composition control, small decarburization layer, high sorbite rate and good drawing performance. According to the personalized requirements of users, the tensile strength of the finished wire rod is controlled, and high-strength, super-high-strength prestressed steel and bridge cable steel are provided for customers. The high-carbon hard wire steel is mostly produced by adopting a large bloom two-fire material production process, and has low productivity and high cost.

[0003] In order to reduce the cost, the high-carbon hard wire steel is produced by adopting a small bloom one-fire material production process, and has the advantages of short production cycle, high production efficiency and low production cost. SUMMARY

[0004] The application aims to provide a preparation method of high-carbon hard wire steel, and the high-carbon hard wire steel is produced by adopting a small bloom one-fire material production process, and has the advantages of short production cycle, high production efficiency and low production cost.

[0005] To solve the above technical problems, the application adopts the following technical scheme:

[0006] The application is a preparation method of high-carbon hard wire steel, and comprises the following steps: hot metal pre-desulfurization, converter smelting, LF furnace refining and small bloom casting machine continuous casting.

[0007] (1) Converter production

[0008] In order to ensure the product quality and accurately control the composition of the finished product, the converter requires desulfurized hot metal, and the sulfur content is less than or equal to 0.050%; a single slag method is adopted for smelting, and the final slag basicity is controlled to be 3.0; lime and dolomite and iron skin balls are added for slagging auxiliary materials in the converter smelting process, and manganese iron and silicon manganese are added for deoxidization and alloying in the tapping process, and Al is used for deoxidization at the end point.

[0009] The tapping temperature of the converter end point molten steel is T≥1620℃; the tapping [C] is ≥0.08%; and the [P] is 0.007-0.015%;

[0010] (2) Refining furnace production

[0011] The range of anthracite added for refining is 0-130 kg, the soft blowing time is 15-30 minutes, and the soft blowing argon flow rate is 80-120 NL / min; the temperature of the molten steel on the continuous casting platform ranges from 1510-1560°C; the molten steel is allowed to stand for more than 5 minutes after refining treatment;

[0012] (3) VD furnace degassing treatment

[0013] In order to improve the quality of molten steel, after LF refining, the molten steel enters the VD furnace for degassing. The deep vacuum time is 15-20 minutes, and the soft blowing time is 11-22 minutes, with an average of 16 minutes, which meets production requirements.

[0014] (4) Continuous casting of small square billets

[0015] In billet continuous casting, the superheat is ≤35°C and the casting speed is between 1.9m / min and 2.0m / min. In order to improve the surface quality of the billet, electromagnetic stirring of the mold and end-stage electromagnetic stirring are used.

[0016] The chemical composition of the high carbon hard wire steel in percentage by mass is: C: 0.76-0.80%, Si: 0.20-0.35%, Mn: 0.65-0.80%, Cr: 0.18-0.22%, P≤0.020%, S≤0.015%, and the rest is Fe and unavoidable impurities.

[0017] Furthermore, it also includes the detection of ingot quality and gas content: a low-magnification hot acid test is carried out on each furnace, and the defect level shall not be greater than level 2; the gas requirements in the steel are [O]≤30ppm, [N]≤70ppm.

[0018] Furthermore, the average amount of refined anthracite added is 64 kg; the soft blowing time is 15-28 minutes, with an average of 18 minutes.

[0019] Furthermore, the soft blowing argon gas flow rate is 100 NL / min.

[0020] Furthermore, the temperature of the molten steel on the continuous casting platform ranges from 1517°C to 1558°C, with an average of 1532°C, and the molten steel is allowed to stand for ≥6 minutes after refining treatment.

[0021] Furthermore, the superheat is controlled between 20 and 35°C.

[0022] Furthermore, a low-magnification hot acid test was conducted on each furnace, with the maximum central porosity at level 1.5, the maximum shrinkage cavity at level 1, the central crack at level 0.5, the middle crack at level 0.5, the subcutaneous crack at level 0, and the corner crack at level 0.

[0023] The gas content of each heat of steel was tested, [O] content: 6-20ppm, [N] content: 38-59ppm.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects:

[0025] The present invention adopts a small square billet one-fired material process to replace a large square billet process, reduces the two-fired material opening process, reduces the cost, shortens the production cycle, and thus meets market requirements. DETAILED DESCRIPTION

[0026] The industrial production process is as follows: molten iron pre-desulfurization → converter smelting → LF furnace refining → small square billet continuous casting machine (150mm×150mm).

[0027] (1) Converter production

[0028] The conditions of the converter molten iron are as follows: Si (%): 0.53-0.72, average 0.61; Mn (%) 0.36-0.63, average 0.52; P (%): 0.115-0.149, average 0.125, S (%): 0.019-0.050, average 0.032; molten iron temperature (℃): 1231-1236, 1234.

[0029] The C content, Mn content, P content, S content (mass percentage) and tapping temperature of the converter end-point molten steel are shown in Table 1.

[0030] 1 Composition and temperature of converter steel

[0031] Steel tapping temperature ℃ C content% Mn content % P content% S content% Minimum 1621 0.08 0.06 0.007 0.020 Maximum 1651 0.25 0.16 0.016 0.039 average value 1634 0.12 0.09 0.011 0.026

[0032] (2) LF furnace refining production

[0033] The average amount of refined anthracite is 64 kg; the soft blowing time is 15-28 minutes, with an average of 18 minutes, and the soft blowing time meets the requirement of ≥15 minutes. The soft blowing argon flow rate is 100NL / min; the temperature range of the molten steel on the continuous casting platform is 1517-1558℃, with an average of 1532℃, and the molten steel is allowed to stand for ≥6 minutes after refining treatment.

[0034] (3) VD furnace degassing treatment

[0035] In order to improve the quality of molten steel, after LF refining, the molten steel enters the VD furnace for degassing. The deep vacuum time is 16-20 minutes and the soft blowing time is ≥15 minutes.

[0036] (4) Continuous casting production

[0037] In the production of 150mm×150mm small square billet continuous casting machine, the superheat is controlled between 20 and 35℃, the casting speed is between 1.9m / min and 2.0m / min, and the finished steel composition (mass percentage) is controlled as shown in Table 2.

[0038] Table 2 Finished product composition of molten steel (%)

[0039] C Si Mn P S Cr Minimum 0.76 0.22 0.66 0.008 0.004 0.18 Maximum 0.80 0.34 0.78 0.017 0.011 0.22 average value 0.77 0.28 0.72 0.012 0.007 0.20

[0040] (5) Ingot quality and gas content detection

[0041] Each furnace is subjected to a low-magnification hot acid test, with the maximum central porosity being 1.5, the maximum shrinkage cavity being 1, the central crack being 0.5, the middle crack being 0.5, the subcutaneous crack being 0, and the corner crack being 0.

[0042] The gas content of each heat of steel was tested, [O] content: 6-20ppm, [N] content: 38-59ppm.

[0043] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing high carbon hard wire steel, characterized in that: include: Hot metal pre-desulfurization → converter smelting → LF furnace refining → billet casting machine continuous casting; including: (1) Converter production To ensure product quality and precise control of finished product composition, the desulfurized hot metal for converters must have a sulfur content of less than or equal to 0.050%. Single-slag smelting is adopted, and the final slag basicity is controlled at 3.

0. During the converter smelting process, lime, dolomite, and iron balls are added as slag-making auxiliary materials. During the tapping process, ferromanganese and silicon-manganese are added according to the composition requirements for deoxidation and alloying. Al deoxidation is used at the end point. The tapping temperature of the molten steel at the converter end point is T≥1620℃; tapping [C]≥0.08%; [P]0.007~0.015%; (2) Refining furnace production The range of anthracite added for refining is 0-130 kg, the soft blowing time is 15-30 minutes, and the soft blowing argon flow rate is 80-120 NL / min; the temperature of the molten steel on the continuous casting platform ranges from 1510-1560°C; the molten steel is allowed to stand for more than 5 minutes after refining treatment; (3) VD furnace degassing treatment In order to improve the quality of molten steel, after LF refining, the molten steel enters the VD furnace for degassing. The deep vacuum time is 15-20 minutes, and the soft blowing time is 11-22 minutes, with an average of 16 minutes, which meets production requirements. (4) Continuous casting of small square billets In billet continuous casting, the superheat is ≤35°C and the casting speed is between 1.9m / min and 2.0m / min. In order to improve the surface quality of the billet, electromagnetic stirring of the mold and end-stage electromagnetic stirring are used. The chemical composition of the high carbon hard wire steel in percentage by mass is: C: 0.76-0.80%, Si: 0.20-0.35%, Mn: 0.65-0.80%, Cr: 0.18-0.22%, P≤0.020%, S≤0.015%, and the rest is Fe and unavoidable impurities.

2. The method for preparing high carbon hard wire steel according to claim 1, characterized in that: It also includes the detection of ingot quality and gas content: a low-magnification hot acid test is carried out on each furnace, and the defect level shall not be greater than level 2; the gas requirements in the steel are [O]≤30ppm, [N]≤70ppm.

3. The method for preparing high carbon hard wire steel according to claim 1, characterized in that: The average weight of refined anthracite is 64 kg; the soft blowing time is 15-28 minutes, with an average of 18 minutes.

4. The method for preparing high carbon hard wire steel according to claim 1, wherein: The soft blowing argon flow rate is 100NL / min.

5. The method for preparing high carbon hard wire steel according to claim 1, characterized in that: The temperature of the molten steel on the continuous casting platform ranges from 1517 to 1558°C, with an average of 1532°C. The molten steel is allowed to stand for ≥6 minutes after refining treatment.

6. The method for preparing high carbon hard wire steel according to claim 1, characterized in that: The superheat is controlled between 20 and 35°C.

7. The method for preparing high carbon hard wire steel according to claim 1, characterized in that: Each furnace is subjected to a low-power hot acid test, with the maximum central porosity at level 1.5, the maximum shrinkage cavity at level 1, the central crack at level 0.5, the middle crack at level 0.5, the subcutaneous crack at level 0, and the corner crack at level 0; The gas content of each heat of steel was tested, [O] content: 6-20ppm, [N] content: 38-59ppm.