Technique for producing 500MPa level high-strength quake-proof reinforcing steel bar

Abstract

The invention discloses a technique for producing 500MPa level high-strength quake-proof reinforcing steel bar. Nitrogen is blown into molten steel in a steel ladle by a microwave field in the process of steel taping, [N] in the molten steel ranges from 0.08% to 0.012%; reducible manganese oxide pellets are added in the metaphase of smelting; reducible vanadium oxide and niobium oxide pellets are added in the later stage of smelting; manganese family alloy, silicon family alloy and carburant are added in the process of steel taping, [Mn] in the molten steel ranges from 0.60% to 1.40%, [Si] in the molten steel ranges from 0.20% to 0.60%; ferrovanadium and ferroniobium are added in the process of steel taping to fine tunes vanadium and niobium in the steel, [V] in the steel ranges from 0.02% to 0.055%, [Nb] ranges from 0.02% to 0.055%; molten steel is cast into steel billets by a conticaster, the steel billets are heated by a heating furnace, heating temperature is between 1050 DEG C and 1250 DEG C, start rolling temperature is between 950 DEG C and 1150 DEG C, finishing temperature is between 950 DEG C and 1050 DEG C, and cooling speed after rolling is between 15 DEG C / s and 500 DEG C / s; Rel of the reinforcing steel bar produced by the method is between 530MPa and 560MPa, Rm is between 660MPa and 730MPa, A is between 18% and 25%, Rm / Rel is between 1.30 and 1.45, ageing lasts for three months, undulating quantity of Rel and Rm is less than 15MPa, welding performance is good, and popularization and application prospects are promising.

Description

technical field [0001] The invention relates to a production process of low-alloy steel, in particular to a production process of 500MPa high-strength anti-seismic steel bars. Background technique [0002] At present, most low-alloy steels are designed with carbon-manganese steel-based components, manganese-based and silicon-based iron alloys are used for alloying manganese and silicon elements, vanadium-iron or vanadium-nitrogen alloys are used for vanadium microalloying, and niobium-iron alloys are used for niobium microalloying. Chemical, its main components control [Mn] between 1.2-1.6%, [Si] between 0.40-0.60%, [C] between 0.17-0.25%, [V] between 0.06-0.12% , [Nb] is controlled between 0.04-0.09%, yield strength (Rel) ≥ 500MPa, tensile strength ≥ 630MPa, reduction of area (A) ≥ 16%, mainly relying on carbon, manganese and silicon solid solution strengthening and vanadium and Niobium precipitation strengthening, this steel has the following problems: ①Silo-manganese and...

AI Technical Summary

Problems solved by technology

[0002] At present, most low-alloy steels are designed with carbon-manganese steel-based components, manganese-based and silicon-based iron alloys are used for alloying manganese and silicon elements, vanadium-iron or vanadium-nitrogen alloys are used for vanadium microalloying, and niobium-iron alloys are used for niobium microalloying. Chemical, its main components control [Mn] between 1.2-1.6%, [Si] between 0.40-0.60%, [C] between 0.17-0.25%, [V] between 0.06-0.12% , [Nb] is controlled between 0.04-0.09%, yield strength (Rel) ≥ 500MPa, tensile strength ≥ 630MPa, reduction of area (A) ≥ 16%, mainly relying on carbon, manganese and silicon solid solution strengthening and vanadium and Niobium precipitation strengthening, this steel has the following problems: ①Silo-manganese and carbon content is high, and the alloy cost increases; ②Element segregation is easy to occur during solidification and cooling; ③High carbon equivalent has poor welding performance, vanadium and High niobium content and high alloy cost; ④ prone to inconspicuous yield and mixed crystal phenomenon; ⑤ poor shock resistance

Another method is to control the composition to the lower limit, and use low-temperature large-deformation rolling to produce ultra-fine-grained steel, and the alloy composition can be reduced, but the disadvantages of this method are that ① the capacity of the rolling mill needs to be greatly increased; Conventional welding cannot be used, otherwise the strength of the steel bar in the welding zone will be greatly reduced

Another method is to control the composition to the lower limit, and use forced cooling after rolling, and the alloy composition can also be greatly reduced, but the disadvantages are: ① need to increase water penetration equipment and increase investment; ② the performance of steel bars fluctuates greatly, and the aging phenomenon is serious; ③ Welding performance is poor; ④The steel bar is easy to corrode and the shock resistance is poor