Short-process SWRH82B wire rod production method

Abstract

The invention provides a short-process SWRH82B wire rod production method, and relates to the technical field of high-carbon hard wire production, the short-process SWRH82B wire rod production method comprises the following steps: S1, a regenerated steel raw material is added into an electric furnace, ferrotitanium or ferroboron is added, and the titanium-nitrogen ratio is controlled to be 3-4; or the ratio of boron to nitrogen is 0.2-0.3; and S2, the electric furnace is started for heating, the regenerated steel raw materials are completely molten into molten steel, refining, continuous casting, rolling and controlled cooling are sequentially conducted subsequently, and the SWRH82B wire rod is obtained. According to the SWRH82B wire rod production process, regenerated steel is adopted as a steelmaking raw material, an electric furnace smelting process is combined, and compared with a traditional long-flow process, carbon emission per ton of steel is reduced by 60% or above. The martensite of the prepared SWRH82B wire rod is less than or equal to grade 1; network carbide < = grade 1; the lamellar spacing of pearlite is 150-170nm, and the Soxhlet formation rate is greater than or equal to 95%; the tensile strength is 1150-1250MPa, and the percentage reduction of area is greater than or equal to 35% And the work hardening rate is smaller than or equal to 0.210, and good drawing deep processing performance is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of high-carbon hard wire production, in particular to a short-process SWRH82B wire rod production method. Background Art

[0002] At present, recycled steel raw materials and electric furnace steelmaking have become the research focus of the steel industry. Compared with traditional long-process steelmaking, every ton of recycled steel raw materials combined with electric furnace steelmaking technology can reduce carbon emissions by 1.2-1.4 tons. However, during electric furnace steelmaking, the high-temperature electric arc ionizes nitrogen atoms in the air into nitrogen ions, and nitrogen ions are easily dissolved in molten steel. When using electric furnace steelmaking, the nitrogen content in the steel can reach 80-120ppm, while the nitrogen content in steel smelted in the traditional long process is only 40-60ppm. Excessive nitrogen content in steel will lead to reduced plasticity and increased work hardening rate, which will lead to problems such as excessive wire breakage rate and brittle steel performance during the subsequent wire rod drawing process.

[0003] Furthermore, SWRH82B high carbon hard wire is mainly used to produce prestressed steel strands, which are widely used in bridge engineering, building structures, roads and railways, etc., playing a role in enhancing structural strength, improving bearing capacity and extending service life. The production process of prestressed steel strands adopts a large deformation cold drawing process, which puts forward higher requirements for the abnormal organization control, composition uniformity and plastic toughness of the raw materials.

[0004] Therefore, regulating the residual N element in the short-process steelmaking of recycled steel raw materials and reducing the damage of N element to steel properties are important for the production of high-carbon hard wire. Summary of the invention

[0005] In order to solve the technical problem of excessively high nitrogen content in steel when SWRH82B wire rod is produced by using recycled steel raw materials in the prior art, the purpose of the present invention is to provide a short-process SWRH82B wire rod production method to achieve the control of residual element N in SWRH82B wire rod produced by electric furnace using recycled steel raw materials. The method converts solid-solution nitrogen into combined nitrogen by forming nitrides with Ti and B elements, which can effectively reduce the adverse effects of nitrogen generated by electric furnace steelmaking of recycled steel raw materials, and the carbon emission per ton of steel is less than 800kg, which is more than 60% lower than the carbon emission per ton of steel produced by traditional long-process SWRH82B wire rod.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] A short-process SWRH82B wire rod production method comprises the following steps:

[0008] S1. Add the recycled steel raw material into an electric furnace, and add ferrotitanium or ferroboron to control the titanium-nitrogen ratio to 3-4; or the boron-nitrogen ratio to 0.2-0.3; the present invention has no restriction on the source and element content of the recycled steel raw material, and only needs to control the titanium-nitrogen ratio or the boron-nitrogen ratio therein, because Ti and B elements easily form carbonitrides with N and C elements in steel, and TiC has a low free energy, so it is necessary to add 3-4 times the Ti element of N element to achieve the ideal nitrogen fixation effect, and compared with BC, BN has a lower free energy and therefore will react with N element first, and only 0.2-0.3 times the nitrogen content of boron element needs to be added to achieve the ideal nitrogen fixation effect.

[0009] S2, the electric furnace is turned on for heating, the recycled steel raw material is completely melted into molten steel, and then refining, continuous casting, rolling, and controlled cooling are performed in sequence to obtain the SWRH82B wire rod. The refining, continuous casting, rolling, and controlled cooling in the present invention are all prior arts, and the specific parameters are described in the examples.

[0010] Furthermore, in step S2, after the recycled steel raw material is completely melted into molten steel, the mass percentage of each element is adjusted to make C: 0.80-0.85%; Mn: 0.60-0.90%; Si: 0.12-0.32%; N: 0.010-0.015%; S≤0.025%; P≤0.025%; Cu≤0.20%, and the titanium-nitrogen ratio is controlled to 3-4; or the boron-nitrogen ratio is 0.2-0.3.

[0011] Furthermore, in step S2, the heating temperature of the electric furnace is ≥ 1600°C.

[0012] Furthermore, according to the statistics of the World Steel Association in 2024, carbon emissions per ton of steel in my country's steel industry are about 1.8tCO 2 / t, while the carbon emissions from producing one ton of steel in a blast furnace and converter is 1.2tCO 2 / t, while the carbon emissions per ton of steel produced by an electric arc furnace using scrap steel is only 0.04tCO 2 / t. Therefore, the carbon emissions per ton of steel produced by the production method of the present invention can be reduced by about 1.16tCO 2 / t, which reduces carbon emissions per ton of steel by 64.4% compared with traditional long-process steelmaking.

[0013] The present invention also provides SWRH82B wire rod produced by the method.

[0014] Furthermore, the SWRH82B wire rod produced in the present invention has a martensite of ≤1 grade; a network carbide of ≤1 grade; a pearlite interlamellar spacing of 150-170nm, and a Soxhletization rate of ≥95%.

[0015] Furthermore, the SWRH82B wire rod produced in the present invention has a tensile strength of 1150-1250 MPa, a cross-sectional shrinkage of ≥35%, and a work hardening rate of ≤0.210.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention converts the solid-solution nitrogen in the SWRH82B wire rod into the combined nitrogen in the nitride through Ti and B nitrogen fixation, thereby eliminating the plastic damage of SWRH82B caused by the solid-solution N atoms. At the same time, the microalloy nitride pins the grain boundary. The nitride is formed during the steel smelting process and is not dissolved during the subsequent heat treatment process. The fine and dispersed nitride pins the grain boundary, inhibits the growth of austenite, reduces the pearlite interlamellar spacing and pearlite ball size of the SWRH82B wire rod, and significantly reduces carbon emissions and improves its plastic toughness compared to the traditional long-process SWRH82B wire rod. Compared with the electric furnace production of SWRH82B using recycled steel raw materials without Ti and B nitrogen fixation, the plastic damage caused by the SWRH82B wire rod caused by the excessively high N content is completely eliminated, and the tensile strength is also increased by 50-100MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. 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 creative work.

[0019] Figure 1 This is the optical microscopic photograph of SWRH82B in Example 1;

[0020] Figure 2 This is the optical microscopic photograph of SWRH82B in Example 2;

[0021] Figure 3 This is the optical microstructure photo of SWRH82B in Comparative Example 1;

[0022] Figure 4 This is the optical microstructure photo of SWRH82B in Comparative Example 2;

[0023] Figure 5 This is the optical microstructure photo of SWRH82B in Comparative Example 3;

[0024] Figure 6 This is the optical microstructure photo of SWRH82B in Comparative Example 4;

[0025] Figure 7 This is the BSEM microstructure photo of SWRH82 in Example 1;

[0026] Figure 8 This is the BSEM microstructure photo of SWRH82 in Example 2;

[0027] Fig. 9 This is the BSEM microstructure photo of SWRH82 in Comparative Example 1;

[0028] Fig.10 This is the BSEM microstructure photo of SWRH82 in Comparative Example 2;

[0029] Fig.11 This is the BSEM microstructure photo of SWRH82 in Comparative Example 3;

[0030] Fig.12 This is the BSEM microstructure photo of SWRH82 in Comparative Example 4;

[0031] Fig.13 is the engineering stress-strain curve of SWRH82B in Example 1;

[0032] Fig.14 is the engineering stress-strain curve of SWRH82B in Example 2;

[0033] Fig.15 is the engineering stress-strain curve of SWRH82B in comparative example 1;

[0034] Fig.16 is the engineering stress-strain curve of SWRH82B in comparative example 2;

[0035] Fig.17 is the engineering stress-strain curve of SWRH82B in comparative example 3;

[0036] Fig.18 This is the engineering stress-strain curve of SWRH82B in comparative example 4. DETAILED DESCRIPTION

[0037] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0038] Example 1

[0039] This embodiment provides a method for producing SWRH82B wire rod by electric furnace of recycled steel raw materials:

[0040] S1. Add the recycled steel raw materials into the electric furnace, control the furnace temperature ≥1600℃, completely melt the recycled steel raw materials into molten steel, add ferrotitanium to control the composition of the molten steel to C: 0.80%; Mn: 0.60%; Si: 0.12%; N: 0.0101%; Ti: 0.0350%; S: ≤0.025%; P: ≤0.025%; Cu: ≤0.20%. Then transfer the molten steel to the refining furnace, the steel output is 65%, and the titanium-nitrogen ratio in this embodiment is 3.47;

[0041] S2. The molten steel in step 1 is refined and the stirring time is 1.5h;

[0042] S3. The refined molten steel is continuously cast into a square billet having a cross-sectional length of 150 mm, and the continuous casting speed is 3 m / min;

[0043] S4. The steel billet is heated at 1100°C for 30 min;

[0044] S5. After heating, the billet is rolled, the starting rolling temperature is 1060°C, the final rolling temperature is 940°C, the rolling speed is 32m / s, and the square billet is rolled into Φ12.5 raw material wire rod;

[0045] S6. After rolling, the wire rod enters the air cooling track. When the surface temperature of the wire rod is above 600℃, the cooling rate is 12~16℃ / s. When the temperature is 600℃~400℃, the cooling rate when entering the insulation cover is controlled at 0.2~0.8℃ / s. When the temperature is below 400℃, air cool to room temperature.

[0046] Example 2

[0047] This embodiment provides a method for producing SWRH82B wire rod of recycled steel raw material electric furnace:

[0048] S1. Add the recycled steel raw materials into the electric furnace, control the temperature of the electric furnace to ≥1600℃ to completely melt the recycled steel raw materials into molten steel, add ferroboron to control the composition of the molten steel to be C: 0.84%; Mn: 0.90%; Si: 0.32%; N: 0.0116%; B: 0.0028%; S: ≤0.025%; P: ≤0.025%; Cu: ≤0.20%. Then transfer the molten steel to the refining furnace, the steel output is 65%, and the boron nitrogen ratio in this embodiment is 0.24;

[0049] S2-S6 are the same as in Example 1.

[0050] Comparative Example 1

[0051] This comparative example provides a traditional long-process SWRH82B wire rod production method, in which the steelmaking adopts a converter to smelt the SWRH82B steel billet with a low nitrogen content and no Ti or B elements are added, and the other processes and components, contents, and preparation processes are the same as those of Examples 1 and 2;

[0052] S1. The SWRH82B steel billet is smelted in a top and bottom combined blowing converter, and the molten steel composition is controlled to be C: 0.82%; Mn: 0.90%; Si: 0.32%; N: 0.0041%; S: ≤0.025%; Cu: ≤0.20%;

[0053] S2-S6 are the same as in Example 1.

[0054] Comparative Example 2

[0055] This comparative example provides a method for producing SWRH82B wire rod of recycled steel raw material electric furnace: Ti and B elements are not added during the electric furnace steelmaking process of this comparative example, and other processes, components, contents, and preparation processes are the same as those of Examples 1 and 2;

[0056] S1. Add the recycled steel raw materials into the electric furnace, control the temperature of the electric furnace ≥1600℃ to completely melt the recycled steel raw materials into molten steel, and control the composition of the molten steel to be C: 0.84%; Mn: 0.90%; Si: 0.32%; N: 0.0114%; S: ≤0.025%; P: ≤0.025%; Cu: ≤0.20%. Then transfer the molten steel to the refining furnace, and the output is 65%.

[0057] S2-S6 are the same as in Example 1.

[0058] Comparative Example 3

[0059] This comparative example provides a method for producing SWRH82B wire rod of recycled steel raw material electric furnace: Ti with a similar nitrogen content is added during the electric furnace steelmaking process of this comparative example, and other processes and components, contents, and preparation processes are the same as those of Examples 1 and 2;

[0060] S1. Add the recycled steel raw materials into the electric furnace, control the temperature of the electric furnace to ≥1600℃ to completely melt the recycled steel raw materials into molten steel, and control the composition of the molten steel to be C: 0.84%; Mn: 0.91%; Si: 0.29%; N: 0.0112%; Ti: 0.0121%; S: ≤0.025%; P: ≤0.025%; Cu: ≤0.20%. Then transfer the molten steel to the refining furnace, and the steel output is 65%. In this embodiment, the titanium-nitrogen ratio is 1.08.

[0061] S2-S6 are the same as in Example 1.

[0062] Comparative Example 4

[0063] This comparative example provides a method for producing SWRH82B wire rod of recycled steel raw material electric furnace: B with a nitrogen content of 0.1 times is added during the electric furnace steelmaking process of this comparative example, and other processes and components, contents, and preparation processes are the same as those of Examples 1 and 2;

[0064] S1. Add the recycled steel raw materials into the electric furnace, control the temperature of the electric furnace to ≥1600℃ to completely melt the recycled steel raw materials into molten steel, and control the composition of the molten steel to be C: 0.85%; Mn: 0.88%; Si: 0.28%; N: 0.0125%; B: 0.0013%; S: ≤0.025%; P: ≤0.025%; Cu: ≤0.20%. Then transfer the molten steel to the refining furnace, and the steel output is 65%. In this embodiment, the boron nitrogen ratio is 0.10.

[0065] S2-S6 are the same as in Example 1.

[0066] The following performance tests were performed on the embodiments and comparative examples:

[0067] (1) Microstructure: The microstructure parameters of the SWRH82B wire rods of Examples 1-2 and Comparative Examples 1-4 were measured according to the standards GB / T13298 Metal Microstructure Test Method, YB / T169 Metallographic Test Method for Solenite Content in High Carbon Steel Wire Rod, and YB / T 4411-2014 Method for Evaluating Central Martensite in High Carbon Steel Wire Rod.

[0068] Figure 1-6 These are optical microstructure photos of SWRH82B in Examples 1 and 2 and Comparative Examples 1-4, respectively, and the Soxhlet content in the material can be counted. Figure 7-12 The BSEM microstructure photos of SWRH82 in Examples 1 and 2 and Comparative Examples 1-4 are shown in Table 1. The pearlite ball size and interlamellar spacing can be counted.

[0069] (2) Mechanical properties: The strength of Examples 1-2 and Comparative Examples 1-4 was tested in accordance with the standard GB / T 228.3-2019 Tensile Test of Metallic Materials. Figure 13-18 The engineering stress-strain curves of SWRH82B in Examples 1 and 2 and Comparative Examples 1-4 respectively show the mechanical properties of the material. The test statistical results are shown in Table 2.

[0070] Table 1 Comparison of microstructure parameters of Examples 1, 2 and Comparative Examples 1-4

[0071]

[0072] Table 2 Comparison of mechanical properties of Examples 1, 2 and Comparative Examples 1-4

[0073]

[0074] Combined with the component analysis, it can be seen that after adding micro-alloy elements in Example 1-2 and controlling the titanium-nitrogen ratio to 3-4; or the boron-nitrogen ratio to 0.2-0.3, the plasticity of the wire rod is improved by about 20%, and the work hardening rate is similar to that of the traditional long-process low-nitrogen wire rod in Comparative Example 1, indicating that the addition of Ti and B elements has achieved a good nitrogen fixation effect.

[0075] In Comparative Example 2, too much nitrogen was introduced during the short-process smelting process, so the 82B wire rod produced had poor plasticity, and the high work hardening rate was not conducive to subsequent cold drawing. In Comparative Example 3, only Ti element with the same content as N element was added; in Comparative Example 4, only B element with 0.1 times the content of N element was added, although the plasticity of 82B was also improved, compared with the long-process low-nitrogen 82B of Comparative Example 1 and the 82B wire rod with the microalloying elements of the content specified by the present invention added in Examples 1 and 2, although it also played a certain nitrogen fixing role, the plasticity was still low and the work hardening rate was high.

[0076] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A short-process SWRH82B wire rod production method, characterized in that: The following steps are involved: S1. Add the recycled steel raw materials into the electric furnace, and add ferrotitanium or ferroboron, and control the titanium-nitrogen ratio to 3-4; or the boron-nitrogen ratio to 0.2-0.3; S2. The electric furnace is turned on for heating to melt the recycled steel raw materials into molten steel, followed by refining, continuous casting, rolling, and controlled cooling to obtain the SWRH82B wire rod.

2. The short-process SWRH82B wire rod production method according to claim 1, characterized in that: In step S2, after the recycled steel raw material is completely melted into molten steel, the mass percentage of each element is adjusted to make C: 0.80-0.85%; Mn: 0.60-0.90%; Si: 0.12-0.32%; N: 0.010-0.015%; S≤0.025%; P≤0.025%; Cu≤0.20%.

3. The short-process SWRH82B wire rod production method according to claim 1, characterized in that: In step S2, the heating temperature of the electric furnace is ≥1600°C.

4. The short-process SWRH82B wire rod production method according to any one of claims 1 to 3, characterized in that: The carbon emission per ton of steel produced by the production method of the present invention is reduced by 1.16tCO 2 / t, which reduces carbon emissions by 64.4% compared with traditional long-process steelmaking.

5. SWRH82B wire rod produced by the method according to any one of claims 1 to 3.

6. The SWRH82B wire rod according to claim 5, characterized in that: The SWRH82B wire rod martensite is ≤1 grade; the network carbide is ≤1 grade; the pearlite interlamellar spacing is 150-170nm, and the Soxhletization rate is ≥95%.

7. The SWRH82B wire rod according to claim 5, characterized in that: The SWRH82B wire rod has a tensile strength of 1150-1250 MPa, a cross-sectional shrinkage rate of ≥35%, and a work hardening rate of ≤0.210.

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