A production process for HPB300 plain round steel bars

Abstract

This invention relates to a production process for HPB300 plain round steel bars, belonging to the field of metal smelting technology. The HPB300 series plain round steel bar production process adjusts the weight percentage of manganese (Mn) in the molten steel to 0.42-0.55%. The market price of manganese (Mn) iron ore is approximately 6000 yuan / ton. The cost of adding 0.01% manganese to each ton of billet is typically about 1 yuan. Within 7 months, 87914 tons of HPB300 φ6 and φ8 plain round steel bars were produced, saving 0.10 Mn per ton of steel. The production of HPB300 φ10 steel bars was 13872 tons, saving 0.20 Mn per ton of billet, i.e., 87914 × 10 + 13872 × 20 = 1,154,780 yuan; In addition, in adjusting the production process of HPB300 plain round steel bars, control the billet time in the furnace, reduce the initial rolling temperature, adjust the inlet and outlet rolling temperatures, control the final rolling temperature, and control the cooling time to avoid affecting the mechanical properties of HPB300 series plain round steel bars due to the adjustment of manganese (Mn) dosage.

Description

Technical Field

[0001] This invention belongs to the field of metal smelting technology. Specifically, this invention relates to a production process for HPB300 plain round steel bars. Background Technology

[0002] HPB300 plain round steel bars are mainly used for stirrups and tie bars, as well as horizontal and vertical reinforcement in shear walls, and most of them require bending hooks during use. HPB300 steel bars have a yield strength of 300MPa and a tensile strength of not less than 420MPa, possessing good ductility and weldability, making them suitable for various construction projects.

[0003] In existing technologies, HPB300 plain round steel bars have different requirements for the weight percentage of manganese in the chemical composition of the billet due to different production grades. This results in poor billet versatility and poses certain difficulties for production flexibility. Multiple production grades of HPB300 plain round steel bars need to be produced in separate furnaces. For example, HPB300 φ6 and φ8 plain round steel bars are produced in one furnace, HPB300 φ10 plain round steel bars in another furnace, HPB300 φ6, φ8, and φ10 in another furnace, and HPB300 φ12 plain round steel bars in another furnace. Separate furnace production requires adapting to various types of billets, which increases production costs. At the same time, stacking multiple billets occupies space. Summary of the Invention

[0004] To overcome the problems existing in the background technology, this invention discloses a production process for HPB300 plain round steel bars. In this process, the weight percentage of manganese (Mn) in the molten steel is adjusted to 0.42%-0.55%. The market price of manganese (Mn) iron ore is approximately 6000 yuan / ton. The cost of adding 0.01% manganese to each ton of billet is typically about 1 yuan. Within 7 months, 87914 tons of HPB300 φ6 and φ8 plain round steel bars were produced, saving 0.10 Mn per ton of steel. The production of HPB300 φ10 steel bars was 13872 tons, saving 0.20 Mn per ton of billet, i.e., 87914 × 10 + 13872 × 20 = 1,154,780 yuan; In addition, in adjusting the production process of HPB300 plain round steel bars, control the billet time in the furnace, reduce the initial rolling temperature, adjust the inlet and outlet rolling temperatures, control the final rolling temperature, and control the cooling time to avoid affecting the mechanical properties of HPB300 series plain round steel bars due to the adjustment of manganese (Mn) dosage.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] The production process of HPB300 plain round steel bars is characterized by the following steps:

[0007] (1) Converter smelting: Molten iron from the blast furnace is smelted in the converter;

[0008] (2) LF refining: After converter smelting, the molten steel enters the LF refining furnace for refining;

[0009] (3) Billet continuous casting: After refining, the molten steel enters the billet continuous casting machine to cast billets. After the billets pass the quality inspection, they are ready for use.

[0010] (4) Billet rolling: Billet rolling includes the steps of primary rolling, finishing rolling, final rolling, water cooling, wire cutting, and air cooling;

[0011] (5) Post-processing: The rolled steel bars are collected, cut, inspected, bundled, weighed and uncoiled to obtain finished steel bars, which are then stored in the warehouse for use.

[0012] The chemical composition and weight percentage of the molten steel in the converter are as follows: C: 0.20-0.24%, Si: 0.18-0.28%, Mn: 0.42-0.55%; S: ≤0.045%; P: ≤0.040%, with the balance being iron and unavoidable impurities.

[0013] Preferably, the chemical composition and weight percentage of the molten steel in the converter are: C: 0.22%, Si: 0.23%, Mn: 0.45%; S: ≤0.035%; P: ≤0.035%, with the balance being iron and unavoidable impurities.

[0014] Preferably, the in-furnace time for the converter steelmaking process is 30-45 min.

[0015] Preferably, the billet is subjected to homogenization in a homogenizing furnace and descaling with high-pressure water before rolling, wherein the homogenization temperature is 1100-1150℃.

[0016] Preferably, the initial rolling temperature of the billet is 890-950℃.

[0017] Preferably, the finishing rolling temperature of the cast billet is 950-1050℃.

[0018] Preferably, the final rolling temperature of the billet is 900-950℃.

[0019] Preferably, the wire-spinning temperature during the rolling of the billet is 890-930℃.

[0020] Preferably, the air cooling rate of the billet rolling process is 80℃ / min, and the air cooling time is 2.5-3.5 h.

[0021] The beneficial effects of this invention are as follows: When producing HPB300 series plain round steel bars, the weight percentage of manganese (Mn) in the molten steel is adjusted to 0.42-0.55%. The market price of manganese (Mn) iron ore is approximately 6000 yuan / ton. The cost of adding 0.01% manganese to each ton of cast billet is typically about 1 yuan. HPB300 φ6 and φ8 steel bars can be produced within 7 months. The production of plain round steel bars is 87,914 tons. Based on a saving of 0.10 manganese (Mn) per ton of steel, and the production of HPB300 φ10 steel bars is 13,872 tons. Based on a saving of 0.20 manganese per ton of billet, the total cost is 87,914 × 10 + 13,872 × 20 = 1,154,780 yuan. Furthermore, in adjusting the production process of HPB300 plain round steel bars, the time the billet spends in the furnace is controlled, the initial rolling temperature is reduced, the temperature at the finishing mill and the wire drawing temperature are adjusted, the final rolling temperature is controlled, and the cooling time is controlled to avoid affecting the mechanical properties of the HPB300 series plain round steel bars due to adjustments in the amount of manganese (Mn). Detailed Implementation

[0022] To make the above objectives, technical solutions, and beneficial effects clearer and more explicit, the present invention will be specifically described below in conjunction with embodiments.

[0023] Example 1: Production of Φ6mm HPB300 plain round steel bars:

[0024] The production process of Φ6mm HPB300 plain round steel bars is as follows:

[0025] (1) Converter smelting: blast furnace molten iron enters the converter for smelting, and the time in the furnace is 30 min; the chemical composition and weight percentage of the molten steel in the converter are: C: 0.20%, Si: 0.18%, Mn: 0.42%; S: 0.04%; P: 0.03%, with the balance being iron and unavoidable impurities;

[0026] (2) LF refining: After converter smelting, the molten steel enters the LF refining furnace for refining, and the time in the furnace is 30 minutes;

[0027] (3) Billet continuous casting: After refining, the molten steel enters the billet continuous casting machine to cast billets. The billets are subjected to homogenization in a homogenizing furnace and descaling by high-pressure water. The homogenization temperature is 1100℃. After the billets pass the quality inspection, they are ready for use.

[0028] (4) Billet rolling: Billet rolling includes primary rolling, with a primary rolling temperature of 890℃, finishing rolling, with a finishing rolling temperature of 950℃, final rolling, with a final rolling temperature of 900℃, water cooling, and wire drawing, with a wire drawing temperature of 890℃. During the air cooling process, the air cooling rate of the billet rolling is 80℃ / min, and the air cooling time is 3.5h.

[0029] (5) Post-processing: The rolled steel bars are collected, cut, inspected, bundled, weighed and uncoiled to obtain finished steel bars, which are then stored in the warehouse for use; the Ceq of Φ6mm HPB300 plain round steel bars is 0.28.

[0030] Example 2: Production of Φ8mm HPB300 plain round steel bars

[0031] The production process of Φ8mm HPB300 plain round steel bars is as follows:

[0032] (1) Converter smelting: blast furnace molten iron enters the converter for smelting, and the time in the furnace is 45 min; the chemical composition and weight percentage of the molten steel in the converter are: C 0.24%, Si: 0.28%, Mn: 0.55%; S: 0.045%; P: 0.040%, with the balance being iron and unavoidable impurities;

[0033] (2) LF refining: After converter smelting, the molten steel enters the LF refining furnace for refining, and the time in the furnace is 45 min;

[0034] (3) Billet continuous casting: After refining, the molten steel enters the billet continuous casting machine to cast billets. The billets are subjected to homogenization in a homogenizing furnace and descaling by high-pressure water. The homogenization temperature is 1150℃. After the billets pass the quality inspection, they are ready for use.

[0035] (4) Billet rolling: Billet rolling includes primary rolling, with a primary rolling temperature of 950℃, finishing rolling, with a finishing rolling temperature of 1050℃, final rolling, with a final rolling temperature of 950℃, water cooling, and wire drawing, with a wire drawing temperature of 930℃. During the air cooling process, the air cooling rate of the billet rolling is 90℃ / min, and the air cooling time is 3.5 h.

[0036] (5) Post-processing: The rolled steel bars are collected, cut, inspected, bundled, weighed and uncoiled to obtain finished steel bars, which are then stored in the warehouse for use; the Ceq of Φ8mm HPB300 plain round steel bars is 0.30.

[0037] Example 3: Production of Φ10mm HPB300 plain round steel bars

[0038] The production process of Φ8mm HPB300 plain round steel bars is as follows:

[0039] (1) Converter smelting: blast furnace molten iron enters the converter for smelting, and the time in the furnace is 40 min; the chemical composition and weight percentage of the molten steel in the converter are: C: 0.22%, Si: 0.23%, Mn: 0.45%; S: 0.035%; P: 0.035%, with the balance being iron and unavoidable impurities;

[0040] (2) LF refining: After converter smelting, the molten steel enters the LF refining furnace for refining, and the time in the furnace is 40 minutes;

[0041] (3) Billet continuous casting: After refining, the molten steel enters the billet continuous casting machine to cast billets. The billets are subjected to homogenization in a homogenizing furnace and descaling by high-pressure water. The homogenization temperature is 1120℃. After the billets pass the quality inspection, they are ready for use.

[0042] (4) Billet rolling: Billet rolling includes primary rolling, with a primary rolling temperature of 930℃, finishing rolling, with a finishing rolling temperature of 1000℃, final rolling, with a final rolling temperature of 930℃, water cooling, wire drawing, with a wire drawing temperature of 920℃, and air cooling. The air cooling rate of billet rolling is 85℃ / min, and the air cooling time is 3.5 h.

[0043] (5) Post-processing: The rolled steel bars are collected, cut, inspected, bundled, weighed and uncoiled to obtain finished steel bars, which are then stored in the warehouse for use; the Ceq of Φ10mm HPB300 plain round steel bars is 0.31.

[0044] Example 4: Production of Φ12mm HPB300 plain round steel bars

[0045] The production process of Φ12mm HPB300 plain round steel bars is as follows:

[0046] (1) Converter smelting: The molten iron from the blast furnace enters the converter for smelting, and the time in the furnace is 43 minutes; the chemical composition and weight percentage of the molten steel in the converter are: C: 0.22%, Si: 0.23%, Mn: 0.46%; S: 0.035%; P: 0.035%, with the balance being iron and unavoidable impurities;

[0047] (2) LF refining: After converter smelting, the molten steel enters the LF refining furnace for refining, and the time in the furnace is 40 min;

[0048] (3) Billet continuous casting: After refining, the molten steel enters the billet continuous casting machine to cast billets. The billets are heated in a soaking furnace and descaled by high-pressure water. The soaking temperature is 1130℃. After the billets pass the quality inspection, they are ready for use.

[0049] (4) Billet rolling: Billet rolling includes primary rolling, primary rolling temperature: 920℃, finishing rolling, finishing rolling temperature: 1000℃, final rolling, final rolling temperature: 900℃, water cooling, steel wire drawing, wire drawing temperature: 900℃, air cooling, the air cooling rate of billet rolling is 85℃ / min, and the air cooling time is 3.5 h;

[0050] (5) Post-processing: The rolled steel bars are collected, cut, inspected, bundled, weighed and uncoiled to obtain finished steel bars, which are then stored in the warehouse for use; the Ceq of Φ12mm HPB300 plain round steel bars is 0.34.

[0051] In Examples 1, 2, 3, and 4, HPB300 plain round steel bars with specifications of Φ6mm, Φ8mm, Φ10mm, and Φ12mm were produced in the same furnace. The Ceq of the HPB300 plain round steel bars was 0.28-0.34, indicating stable performance. The Rel of the HPB300 plain round steel bars was ≥310MPa, Rm was ≥430MPa, and A / % was ≥25.5, all of which exceeded the national standard requirements. The mechanical properties of the HPB300 plain round steel bars met the requirements.

[0052] In summary, HPB300 plain round steel bars with specifications of Φ6mm, Φ8mm, Φ10mm, and Φ12mm produced in the same furnace have a manganese (Mn) weight percentage of 0.42-0.55%. The HPB300 plain round steel bars produced have stable performance. By combining multiple production grades of HPB300 series plain round steel bars into one furnace, steelmaking production is facilitated, the versatility of billets is improved, and billet stacking space is saved.

[0053] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A process for producing HPB300 plain round steel bar, characterized in that, The process route comprises the following steps: (1) Converter smelting: the molten iron from the blast furnace is smelted in the converter, the chemical composition and the weight percentage of the molten steel in the converter are as follows: C: 0.22%, Si: 0.23%, Mn: 0.45%; S: ≤0.035%; P: ≤0.035%, the balance is iron and inevitable impurities; the in-furnace time of the converter steelmaking is 30-45 min; (2) LF refining: the molten steel after the converter smelting is refined in the LF refining furnace; (3) Billet continuous casting: the molten steel after the refining is cast into a billet by the billet continuous casting machine, and the billet after the quality inspection is qualified is reserved; (4) Billet rolling: the billet rolling comprises the steps of rough rolling, finish rolling, final rolling, water cooling, steel wire drawing, and air cooling; the heating furnace heating and high-pressure water descaling treatment are carried out before the billet rolling, wherein the heating temperature is 1100-1150℃; the rough rolling temperature of the billet rolling is 890-950℃; the finish rolling temperature of the billet rolling is 950-1050℃; the final rolling temperature of the billet rolling is 900-950℃; the wire drawing temperature of the billet rolling is 890-930℃; the air cooling rate of the billet rolling is 80℃ / min, and the air cooling time is 2.5-3.5 h; (5) Post-treatment: the steel bars after the rolling forming are collected, cut, inspected, baled, weighed, and unloaded to obtain the steel bar products, and the products are stored in the warehouse for use.