MANUFACTURE OF STEEL TUBE FOR CONSTRUCTION PURPOSE FOR LOW TEMPERATURE USE

摘要

PROBLEM TO BE SOLVED: To provide a method for the manufacture of a steel tube for construction purposes, with low yield ratio at low temp., having stable toughness at low temp. and a yield ratio as low as ≤80% at low temp. (-20 to -60°C) and enabling a new earthquake-resistant design. ;SOLUTION: An iron-base alloy having, by weight ratio, ≤30ppm oxygen content is hot-rolled, and the resultant steel plate is formed into steel tube. After the end parts are welded, the resultant steel tube is heated to the austenitic region and cooled down to room temp. at cooling rate C.R. satisfying inequality 20.6≥11.2Ceq+C.R.≥7.6 (where Ceq is represented by Ceq=C+Mn/ 6+Si/24+Ni/40+Cr/5+Mo/4+V/14). By this method, the steel tube for construction purposes for low temp. use, excellent in toughness at low temp. and having low yield ratio even at low temp., can be obtained.;COPYRIGHT: (C)1997,JPO