To obtain excellent yield extensibility without requiring large scale rolling equipment, when heating a steel having a specified compsn. and next subjecting it to hot rolling to produce a reinforcing bar by controlling the rough rolling temp., intermediate rolling temp. and rolling finishing temp. to the specified ones.
This is a method for subjecting steel composed of, by weight, 0.20 to 0.50% C, 0.15 to 1.50% Si, 0.50 to 1.80% Mn, 0.02 to 0.50% Cu, 0.02 to 0.50% Cr, 0 to 0.50% Ni, 0.05 to 0.40% V, 0.01 to 0.10% Nb, 0.005 to 0.02% N, and the balance Fe or the like to heating in a heating furnace and hot rolling, and the rough rolling temp. is controlled to 830 to 900°C, the intermediate rolling temp. to 890 to 950°C, and the rolling finishing temp. to >950 to 1050°C so that the yield elongation percentage of the reinforcing bar [the ratio (-y)/y between the strain y at the starting point of yielding and the strain (-y) till stress furthermore reaches 755 N/mm2 therefrom] is controlled to the prescribed value, preferably to ≥5.0.
YOSHINO HIDEO
SEKIGUCHI TOSHIO
Next Patent: PRODUCTION OF ROLLED SILICON STEEL SHEET