DEFORMED REINFORCING BAR AND ITS MANUFACTURE

摘要

PROBLEM TO BE SOLVED: To provide an inexpensive deformed reinforcing bar stably satisfying the mechanical properties of the SD 345 standard and excellent in gas pressure weldability. SOLUTION: C and Mn are contained by 0.18-0.27% and <=0.70% by weight, respectively. In order to form the structure in the surface layer part into tempered martensite, hot rolling is performed at a finish rolling finishing temperature in the range between (Ar3 transformation point + 50 deg.C) and (Ar3 transformation point + 250 deg.C) and then rapid cooling is performed under the condition that surface temperature is regulated to a value not higher than the Ms point and that the surface temperature is regulated to 620-780 deg.C by recuperation after the stoppage of rapid cooling.