Production method of steel with mark of 10B21 for manufacturing fasteners

Abstract

The invention discloses a production method of steel with the mark of 10B21 for manufacturing fasteners. The production method mainly comprises the following production processes: a smelting route: blast furnace molten iron, molten iron pretreatment, converter top and bottom combined blowing smelting, LF furnace external refining, small square billet continuous casting and long material factory rolling; a rolling route comprises the steps of billet heating, high-pressure water descaling, rough rolling, flying shearing, intermediate rolling, cutting-off shearing, finish rolling, cooling water tank control, spinning, stelmor cooling, coil collecting, trimming, sampling inspection, collecting and bundling, weighing and finished wire rod obtaining. And steel-making process control parameters and steel rolling process control parameters are limited. The invention aims to provide the production method of the steel with the mark of 10B21 for manufacturing the fastener, so that the fastener manufactured by 10B21 base metal has high strength, good toughness and shear resistance.

Description

Technical Field

[0001] The invention relates to the field of metallurgy and rolling technology, and in particular to a production method of 10B21 steel for making fasteners. Background Art

[0002] 10B21 steel, as a common grade in fastener manufacturing, is favored for its superior performance and wide application fields. Cold heading is one of the commonly used processing technologies in fastener manufacturing. It processes steel into fastener products of various shapes by plastic deformation at room temperature. Therefore, cold heading property is crucial for fastener steel. 10B21 steel has good cold heading property. This is due to its suitable chemical composition and microstructure. In terms of chemical composition, the carbon content and silicon content of 10B21 steel are moderate, which not only ensures sufficient strength and hardness, but also maintains good plasticity and toughness. In terms of microstructure, 10B21 steel can obtain uniform and fine grain structure after heat treatment, which is conducive to improving the cold heading performance of steel. However, its performance does not come out of thin air, but is affected by multiple factors. The chemical composition of 10B21 steel is the basic factor affecting its performance. According to the SAE J403 standard, the main chemical components of 10B21 steel include carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S) and boron (B). The content and proportion of these elements in the steel directly determine the mechanical properties, processing properties and welding properties of the steel. Summary of the invention

[0003] The object of the present invention is to provide a production method for steel with a grade of 10B21 for making fasteners, so that the fasteners made of 10B21 base material have high strength, good toughness and shear resistance.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention discloses a method for producing steel with a grade of 10B21 for making fasteners, and the main production process is as follows:

[0006] Smelting route: blast furnace hot metal - hot metal pretreatment - converter top and bottom blowing smelting - LF refining - billet continuous casting - long product mill rolling

[0007] Rolling route: billet heating - high-pressure water descaling - rough rolling - flying shear - intermediate rolling - shearing - finishing rolling - controlled cooling water tank - wire laying - Stelmor cooling - coiling - trimming - sampling inspection - collection and bundling - weighing - finished wire rod; its characteristics are:

[0008] Steelmaking:

[0009] (1) Slag making system: single slag or double slag is used according to the molten iron conditions, and the end point basicity is controlled at 2.5-3.5;

[0010] (2) Deoxidation and alloying: Final deoxidation uses Al deoxidation;

[0011] (3) Add 300kg of top slag lime when tapping;

[0012] (4) Refining and heating for 8-10 minutes, adding 150-200 kg of bauxite, 600-800 kg of lime, 40 kg of aluminum iron, and 30-50 kg of aluminum particles according to the slag surface of the molten steel;

[0013] (5) The pouring must be protected throughout the entire casting process. The long water nozzle of the large ladle should be protected by argon sealing so that the tundish does not expose the steel liquid surface. The temperature of the tundish should be measured once every 5 minutes after the pouring starts. After that, the temperature can be calibrated by referring to the continuous temperature measurement. The normal pouring liquid level is not allowed to be lower than 400mm, and the liquid level when the pouring is stopped is not less than 250mm. The T-shaped mouth of the tundish and the slag in the tundish shall not be larger than 100mm. If it exceeds 100mm, the slag discharge operation shall be carried out in time; the liquid level control in the crystallizer must be automatic, and the liquid level fluctuation shall be ≤5mm;

[0014] Steel rolling:

[0015] (1) For the design of steels containing alloy Ti and Cr, the furnace temperature of the heating section is set to ≤980°C, and the temperature of each soaking section is set to ≤1080°C. The furnace temperature of steels containing Ti and Cr is controlled according to the upper and lower limits;

[0016] (2) Since high-speed wire rolling already has a high deformation rate, by controlling the finishing rolling temperature at 880-920°C, the austenite is prevented from rolling in the recrystallization region to form deformed austenite grains, so that fine ferrite grains can be obtained later;

[0017] (3) The opening degree of the heat preservation cover is changed from opening every three to closing all of them;

[0018] (4) The speed of the slow cooling line roller is set as follows: 0.30 m / s at the entrance, 0.0.31 m / s at the first section, 0.0.32 m / s at the second section, 0.34 m / s at the third section, 0.36 m / s at the fourth section, 0.38 m / s at the fifth section, 0.40 m / s at the sixth section, 0.42 m / s at the seventh section, 0.30 m / s at the eighth section, and 0.31 m / s at the exit.

[0019] Furthermore, the chemical composition of the steel with the grade 10B21 used for making fasteners is as follows by weight: C: 0.18-0.23%; Si: ≤0.10%; Mn: 0.60-0.90%; P≤0.030%; S: ≤0.030%; Ti: 0.03-0.05%; Cr: 0.20-0.25%; Al: 0.03-0.05%; B: 0.0015-0.0025%, and the remainder is Fe and a small amount of impurity elements.

[0020] Furthermore, the chemical composition of the steel with the grade 10B21 used to make fasteners is as follows: The chemical composition of the steel with the grade 10B21 used to make fasteners is as follows: C: 0.2090%; Si: 0.077%; Mn: 0.852%; P: 0.011%; S: 0.0055%; Ti: 0.0340%; Cr: 0.218%; Al: 0.04%; B: 0.0020%, and the remainder is Fe and a small amount of impurity elements.

[0021] Furthermore, the chemical composition of the steel with the grade 10B21 used for making fasteners is as follows: The chemical composition of the steel with the grade 10B21 used for making fasteners is as follows: C: 0.1900%; Si: 0.073%; Mn: 0.846%; P: 0.012%; S: 0.0037%; Ti: 0.038%; Cr: 0.223%; Al: 0.032%; B: 0.0021%, and the remainder is Fe and a small amount of impurity elements.

[0022] Furthermore, in the steelmaking process: the amount of deoxidizer added: 80% aluminum iron 200-300kg / furnace.

[0023] Furthermore, in the steelmaking process: the cold billet pressure of the straightening machine is 100 bar.

[0024] Furthermore, in the steelmaking process: the hot billet pressure is 15 bar.

[0025] Furthermore, the mechanical properties of the steel with the grade 10B21 for making fasteners meet the following requirements: the tensile strength is stable within 500MPa-550MPa, the area reduction is greater than or equal to 45%, and the elongation after fracture is greater than or equal to 25%.

[0026] Compared with the prior art, the beneficial technical effects of the present invention are:

[0027] The method of the present invention stabilizes the tensile strength within 500MPa-550MPa, the area shrinkage is greater than or equal to 45%, the elongation after fracture is greater than or equal to 25%, and the product size and appearance have no defects, and can meet various complex and harsh working conditions. DETAILED DESCRIPTION

[0028] In this embodiment, two furnaces of 10B21 products were smelted and produced by implementing the key control process of steelmaking of the present invention. The composition control results are shown in the following table:

[0029]

[0030] The specific implementation of the steel rolling process is shown in the following table

[0031]

[0032]

[0033] The product performance is shown in the following table

[0034]

[0035] Through the implementation of the steel rolling improvement plan, the mechanical properties of the products fully meet the design requirements.

[0036] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A production method for 10B21 steel for fasteners, the main production process: Smelting route: blast furnace hot metal - hot metal pretreatment - converter top and bottom blowing smelting - LF refining - billet continuous casting - long product mill rolling Rolling route: billet heating - high-pressure water descaling - rough rolling - flying shear - intermediate rolling - shearing - finishing rolling - controlled cooling water tank - wire laying - Stelmor cooling - coiling - trimming - sampling inspection - collection and bundling - weighing - finished wire rod; its characteristics are: Steelmaking: (1) Slag making system: single slag or double slag is used according to the molten iron conditions, and the end point basicity is controlled at 2.5-3.5; (2) Deoxidation and alloying: Final deoxidation uses Al deoxidation; (3) Add 300kg of top slag lime when tapping; (4) Refining and heating for 8-10 minutes, adding 150-200 kg of bauxite, 600-800 kg of lime, 40 kg of aluminum iron, and 30-50 kg of aluminum particles according to the slag surface of the molten steel; (5) The pouring must be protected throughout the entire casting process. The long water nozzle of the large ladle should be protected by argon sealing so that the tundish does not expose the steel liquid surface. The temperature of the tundish should be measured once every 5 minutes after the pouring starts. After that, the temperature can be calibrated by referring to the continuous temperature measurement. The normal pouring liquid level is not allowed to be lower than 400mm, and the liquid level when the pouring is stopped is not less than 250mm. The T-shaped mouth of the tundish and the slag in the tundish shall not be larger than 100mm. If it exceeds 100mm, the slag discharge operation shall be carried out in time; the liquid level control in the crystallizer must be automatic, and the liquid level fluctuation shall be ≤5mm; Steel rolling: (1) For the design of steels containing alloy Ti and Cr, the furnace temperature of the heating section is set to ≤980°C, and the temperature of each soaking section is set to ≤1080°C. The furnace temperature of steels containing Ti and Cr is controlled according to the upper and lower limits; (2) Since high-speed wire rolling already has a high deformation rate, by controlling the finishing rolling temperature at 880-920°C, the austenite is prevented from rolling in the recrystallization region to form deformed austenite grains, so that fine ferrite grains can be obtained later; (3) The opening degree of the heat preservation cover is changed from opening every three to closing all of them; (4) The speed of the slow cooling line roller is set as follows: 0.30 m / s at the entrance, 0.0.31 m / s at the first section, 0.0.32 m / s at the second section, 0.34 m / s at the third section, 0.36 m / s at the fourth section, 0.38 m / s at the fifth section, 0.40 m / s at the sixth section, 0.42 m / s at the seventh section, 0.30 m / s at the eighth section, and 0.31 m / s at the exit.

2. The method for producing the 10B21 steel for fasteners according to claim 1, characterized in that: The chemical composition of the steel with the grade of 10B21 for making fasteners is as follows: C: 0.18-0.23%; Si: ≤0.10%; Mn: 0.60-0.90%; P ≤0.030%; S：≤0.030％； Ti: 0.03-0.05%; Cr: 0.20-0.25%; Al: 0.03-0.05%; B: 0.0015-0.0025%, the balance is Fe and a small amount of impurity elements.

3. The method for producing steel for fasteners with a grade of 10B21 according to claim 2, characterized in that: The chemical composition of the steel with the grade 10B21 used for making fasteners is as follows: The chemical composition of the steel with the grade 10B21 used for making fasteners is as follows: C: 0.2090%; Si: 0.077%; Mn: 0.852%; P: 0.011%; S：0.0055％； Ti: 0.0340%; Cr: 0.218%; Al：0.04％； B: 0.0020%, the balance being Fe and a small amount of impurity elements.

4. The method for producing steel for fasteners with a grade of 10B21 according to claim 2, characterized in that: The chemical composition of the steel with the grade 10B21 used for making fasteners is as follows: The chemical composition of the steel with the grade 10B21 used for making fasteners is as follows: C: 0.1900%; Si: 0.073%; Mn: 0.846%; P: 0.012%; S：0.0037％； Ti: 0.038%; Cr: 0.223%; Al: 0.032%; B: 0.0021%, the balance being Fe and a small amount of impurity elements.

5. The method for producing the 10B21 steel for fasteners according to claim 1, characterized in that: In the steelmaking process: the amount of deoxidizer added: 80% aluminum iron 200-300kg / furnace.

6. The method for producing steel for fasteners with a grade of 10B21 according to claim 1, characterized in that: In the steelmaking process: the cold billet pressure of the straightening machine is 100 bar.

7. The method for producing steel for fasteners with a grade of 10B21 according to claim 1, characterized in that: In the steelmaking process: hot billet pressure is 15 bar.

8. The method for producing steel for fasteners with a grade of 10B21 according to claim 1, characterized in that: The mechanical properties of the steel with the grade of 10B21 for making fasteners meet the following requirements: the tensile strength is stable within 500MPa-550MPa, the area reduction rate is greater than or equal to 45%, and the elongation after fracture is greater than or equal to 25%.

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