PRODUCTION OF HIGH TENSILE STRENGTH ELECTRIC RESISTANCE WELDED STEEL TUBE EXCELLENT IN HAZ SOFTENING RESISTANCE

摘要

PURPOSE:To improve the roll formability and weldability at the time of tube- manufacturing by specifying the compsn. of a steel for a tube, its coiling temp. at the time of hot sheet thickness rolling and its heat treating temp. after the tube-manufacturing. CONSTITUTION:The components of a steel are formed of, by weight, 0.10 to 0.65% C, 0.05 to 0.60% Si, 0.25 to 2.0% Mn, 0.020 to 0.150% Ti, 0.1 to 0.5% Mo and the balance Fe with inevitable elements. This steel for a tube is coiled at 400 to 600 deg.C or 700 to 750 deg.C at the time of hot sheet thickness rolling. The steel is manufactured into an electric resistance welded steel tube, and after that, this steel is subjected to heat treatment at 600 to 700 deg.C to precipitate Ti. At the time of additionally executing cold sheet thickness rolling or tube manufacturing on-line cold sheet thickness rolling after the coiling at the time of the hot sheet thickness rolling, work hardening is executed, by which the steel tube having high strength can be manufactured.