Smelting method of large-specification HRB400E straight reinforcing steel bar with diameter phi of 28-40mm

Abstract

The invention discloses a smelting method of a large-specification HRB400E straight reinforcing steel bar with the diameter phi of 28-40 mm. The large-specification HRB400E straight reinforcing steel bar comprises the following chemical components in percentage by mass: 0.19-0.25% of C, 0.45-0.65% of Si, 1.30-1.5% of Mn, less than or equal to 0.04% of S, less than or equal to 0.04% of P, 0.008-0.012% of N, 0.025-0.035% of Ti, 0.1-0.25% of Cr and 0.52-0.62% of T value [C + (Si + Mn + Cr) / 6]. The smelting method comprises the following process steps: (1) adding a pre-deoxidized composite slag washing agent after molten steel of steel ladle is seen during converter tapping, wherein the pre-deoxidized composite slag washing agent comprises the following components in percentage by mass: 5-10% of fluorite, 65-75% ofcalcium carbide and 15-25% of limestone; (2) converter tapping is completed, the pre-deoxidation composite slag washing agent is added, then silicon-manganese alloy, silicon iron and high-carbon ferrochrome are added in sequence, the adding amount is set according to component requirements, all the alloys must be added when 1 / 3 of tapping is conducted, and adding of all the alloys is finished when 3 / 4 of tapping is conducted; (3) the steel ladle is conveyed to an argon blowing station through a steel car after tapping is completed, and a high-nitrogen composite enhancer is added according to component requirements; and (4) soft blowing is conducted after ferrotitanium and a high-nitrogen composite enhancer are added.

Description

technical field [0001] The invention belongs to the technical field of metallurgy, and relates to a method for smelting large-scale Φ28-40mm HRB400E straight steel bars that meet the requirements of the GB / T1499.2-2018 standard. Background technique [0002] HRB400E is the grade of steel bar specified in GB / T1499.2-2018 "Reinforcement Bars for Reinforced Concrete Part 2: Hot-rolled Ribbed Steel Bars", and it is a high-strength seismic steel bar. V, Nb, Ti micro-alloy strengthening technology or rapid cooling fine-grain strengthening technology is widely used at home and abroad to produce HRB400E. The use of rapid cooling fine grain strengthening technology requires additional rolling water penetration equipment, which is likely to cause the metallographic structure of the steel bar to fail to meet the requirements of GB / T1499.2-2018, so it is rarely used. The microalloying of domestic steel mainly uses V, Nb, V-N composite, V-Nb composite, etc. to strengthen the steel, so t...

AI Technical Summary

Problems solved by technology

For large-scale HRB400E steel bars above Φ28mm, due to the small rolling compression ratio, large cross-section, and slow cooling after rolling, generally the steel bars produced with the same composition and the same rolling specification will have lower strength.

Images