| 摘要 |
PROBLEM TO BE SOLVED: To provide a weld-closed shear reinforcing bar, which has high strength, high yield strength, and equivalent or rather superior characteristics of welded parts to the base material. SOLUTION: A method for manufacturing the reinforcing bar comprises hot rolling a steel material into a linear rod shape, which contains 0.8-2.0% Si, 0.8-2.0% Mn, 0.005-0.050% Al, 0.005-0.150% Nb, 0.0015-0.0150% N, further one or more of 0.05-2.00% Cr, 0.05-1.00% Mo, and 0.05-1.00% V, so as to make the total amount as 0.5% or more, then slowly cooling it to make the HMV hardness as 500 or less, quenching it in a predetermined condition, tempering it at a tempering temperature of 400-600 deg.C, cutting, bending, and welding both ends. The reinforcing bar has tensile strength of 1420 N/mm<2> or higher, 0.2% yield strength of 1275 N/mm<2> or higher, and butt elongation until fracture of 5% or more, without annealing the above material.
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