Production method of 600MPa high-strength steel bar

Abstract

The invention discloses a production method of a 600MPa high-strength steel bar, and belongs to the technical field of metallurgy, the method adopts a short-flow process of converter smelting, small square billet continuous casting and rolling and cooling bed cooling, vanadium is added in the form of ferrovanadium and vanadium-nitrogen alloy in the smelting process, and the high-strength steel bar comprises the following chemical components in percentage by mass: 0.21-0.28% of C, 0.60-0.70% of Si, 1.50-1.60% of Mn, 0.15-0.21% of V and the balance of Fe and inevitable impurities. And the balance of Fe and inevitable impurities. According to the production method of the 600MPa high-strength steel bar, the strength of the steel bar is improved, and the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a production method of 600MPa high-strength steel bars. Background Art

[0002] HRB600 is the grade of threaded steel bars specified in "Steel for Reinforced Concrete" GB 1499.2-2018. In modern buildings and infrastructure, high-strength steel bars are being used more and more widely. They not only improve the bearing capacity of the structure, but also reduce material usage and engineering costs.

[0003] Due to the wide range of standard components and the differences in production equipment and process control of manufacturers, the components of HRB600 hot-rolled ribbed steel bars produced by various manufacturers are different, and the production processes of various steel mills are also different. The existing HRB600 steel bars have poor mechanical strength and unstable performance. In order to improve the strength of the steel bars and reduce production costs, the present invention adopts vanadium-nitrogen microalloying combined with controlled cooling after rolling to produce HRB600 steel bars for mechanical connection. Summary of the invention

[0004] The purpose of the present invention is to provide a production method of 600MPa high-strength steel bars, thereby improving the strength of the steel bars and reducing production costs.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The present invention discloses a production method of 600MPa high-strength steel bars, which adopts a short process of "converter smelting + billet continuous casting and rolling + cooling bed cooling", and adds vanadium in the form of ferrovanadium and vanadium-nitrogen alloy during the smelting process: wherein:

[0007] The argon blowing operation is carried out according to the refining procedures throughout the whole process. Desulfurization, composition fine-tuning and temperature-raising operations are carried out according to the composition and temperature of the molten steel in the converter. Ferrovanadium and vanadium-nitrogen alloy are added in the later stage of refining. The soft blowing time at the end of refining is guaranteed to be more than 10 minutes to ensure the purity and composition uniformity of the molten steel. After refining, the silicon-calcium wire is fed, and the feeding amount is 200-300m3;

[0008] Protective pouring and electromagnetic stirring technology are used, and the continuous casting speed is 2.3-2.5m / min, thereby reducing surface defects and internal cracks of the ingot and ensuring the high quality of the ingot.

[0009] Strictly control the starting and final rolling temperatures, and through multiple rolling passes, make the steel reach the predetermined size and have a uniform microstructure; heat the continuous casting billet to 1050-1150℃, the starting rolling temperature is 900-1100℃, and the final rolling temperature is 950-1050℃;

[0010] After rolling, the steel bars are placed on a cooling bed to cool naturally to room temperature to avoid internal stress caused by rapid cooling. After the steel bars are cooled to room temperature and pass the inspection, they are wound up and packaged for shipment.

[0011] The chemical composition of the high-strength steel bar is as follows: C 0.21-0.28%, Si 0.60-0.70%, Mn 1.50-1.60%, V 0.15-0.21%, and the balance is Fe and unavoidable impurities.

[0012] Furthermore, the chemical composition of the high-strength steel bar is, by mass percentage, C 0.26%, Si 0.67%, Mn 1.53%, V 0.16%, P 0.015%, S 0.012%, and the remainder is Fe and unavoidable impurities.

[0013] Furthermore, the chemical composition of the high-strength steel bar is, by mass percentage, C 0.27%, Si 0.68%, Mn 1.54%, V 0.15%, P 0.022%, S 0.022%, and the remainder is Fe and unavoidable impurities.

[0014] Furthermore, the chemical composition of the high-strength steel bar is, by mass percentage, C 0.27%, Si 0.65%, Mn 1.53%, V 0.15%, P 0.023%, S 0.015%, and the remainder is Fe and unavoidable impurities.

[0015] Furthermore, the electromagnetic stirring current was 580 A and the frequency was 1.8 Hz.

[0016] Furthermore, the continuous casting speed is 2.4 m / min.

[0017] Furthermore, in the LF furnace refining, auxiliary materials are added to form slag according to the composition of the molten steel and the temperature changes, and alloys are added for fine adjustment and temperature increase operations; 300 kg of lime, bauxite and vanadium-nitrogen alloy are added.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are:

[0019] The high-strength steel bars produced by the present invention meet the standard requirements in all indicators and can meet the needs of users. The high-strength steel bars are produced by adopting the vanadium-nitrogen process and adopt post-rolling controlled cooling to achieve a low-cost process. DETAILED DESCRIPTION

[0020] Three heats of steel were produced in industrial trial production, and the specific control was as follows:

[0021] Table 1 Finished product composition (wt%, balance iron)

[0022] C Si Mn V P S Example 1 0.26 0.67 1.53 0.16 0.015 0.012 Example 2 0.27 0.68 1.54 0.15 0.022 0.022 Example 3 0.27 0.65 1.53 0.15 0.023 0.015

[0023] In LF furnace refining, auxiliary materials are added to make slag according to the composition and temperature changes of molten steel, and alloys are added for fine-tuning and temperature-raising operations; 600kg of lime, 220kg of bauxite, and 300kg of vanadium-nitrogen alloy are added, and the silicon-calcium wire is fed after refining, with a feed amount of 250m3.

[0024] Protective pouring and electromagnetic stirring technology are adopted, with electromagnetic stirring current of 580A, frequency of 1.8Hz, and continuous casting speed of 2.4m / min.

[0025] The continuous casting billet is heated to 1050-1150°C, the starting rolling temperature is 900-1100°C, the final rolling temperature is 950-1050°C, and after rolling, the steel bars are placed on a cooling bed and naturally cooled to room temperature.

[0026] Table 2 Rolling temperature control of each embodiment ℃

[0027] Heating temperature Rolling temperature Finishing rolling temperature Example 1 1120 1000 970 Example 2 1122 1001 980 Example 3 1120 1010 982

[0028] The steel bars prepared in the above three embodiments were tested for mechanical properties, and the test results are listed in Table 3:

[0029] Table 3 Mechanical properties test

[0030]

[0031] As can be seen from Table 2, all indicators of the high-strength steel bars produced by the present invention meet the standard requirements and can meet the needs of users. The high-strength steel bars are produced by the vanadium-nitrogen process and the post-rolling controlled cooling is used to achieve a low-cost process.

[0032] 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 method for producing 600MPa high-strength steel bars, characterized in that: The short process of "converter smelting + billet continuous casting and rolling + cooling bed cooling" is adopted, and vanadium is added in the form of ferrovanadium and vanadium-nitrogen alloy during the smelting process: The argon blowing operation is carried out according to the refining procedures throughout the whole process. Desulfurization, composition fine-tuning and temperature-raising operations are carried out according to the composition and temperature of the molten steel in the converter. Ferrovanadium and vanadium-nitrogen alloy are added in the later stage of refining. The soft blowing time at the end of refining is guaranteed to be more than 10 minutes to ensure the purity and composition uniformity of the molten steel. After refining, the silicon-calcium wire is fed, and the feeding amount is 200-300m3; Protective pouring and electromagnetic stirring technology are used, and the continuous casting speed is 2.3-2.5m / min, thereby reducing surface defects and internal cracks of the ingot and ensuring the high quality of the ingot. Strictly control the starting and final rolling temperatures, and through multiple rolling passes, make the steel reach the predetermined size and have a uniform microstructure; heat the continuous casting billet to 1050-1150℃, the starting rolling temperature is 900-1100℃, and the final rolling temperature is 950-1050℃; After rolling, the steel bars are placed on a cooling bed to cool naturally to room temperature to avoid internal stress caused by rapid cooling. After the steel bars are cooled to room temperature and pass the inspection, they are wound up and packaged for shipment. The chemical composition of the high-strength steel bar is as follows: C 0.21-0.28%, Si 0.60-0.70%, Mn 1.50-1.60%, V 0.15-0.21%, and the balance is Fe and unavoidable impurities.

2. The method for producing a 600MPa high-strength steel bar according to claim 1, characterized in that: The chemical composition of the high-strength steel bar is as follows by mass percentage: C 0.26%, Si 0.67%, Mn 1.53%, V 0.16%, P 0.015%, S 0.012%, and the remainder is Fe and unavoidable impurities.

3. The method for producing a 600MPa high-strength steel bar according to claim 1, characterized in that: The chemical composition of the high-strength steel bar is as follows by mass percentage: C 0.27%, Si 0.68%, Mn 1.54%, V 0.15%, P 0.022%, S 0.022%, and the balance is Fe and unavoidable impurities.

4. The method for producing a 600MPa high-strength steel bar according to claim 1, characterized in that: The chemical composition of the high-strength steel bar is as follows by mass percentage: C 0.27%, Si 0.65%, Mn 1.53%, V 0.15%, P 0.023%, S 0.015%, and the balance is Fe and unavoidable impurities.

5. The method for producing a 600MPa high-strength steel bar according to claim 1, characterized in that: The electromagnetic stirring current was 580A and the frequency was 1.8 Hz.

6. The method for producing a 600MPa high-strength steel bar according to claim 1, characterized in that: Continuous casting speed is 2.4m / min.

7. The method for producing a 600MPa high-strength steel bar according to claim 1, characterized in that: In LF furnace refining, auxiliary materials are added to form slag according to the composition of molten steel and temperature changes, and alloys are added for fine-tuning and temperature-raising operations; 500-800kg of lime, 200-300kg of bauxite, and 300kg of vanadium-nitrogen alloy are added.

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