The Mo super high tension electric resistance welded tube null where ductility

摘要

PURPOSE: To provide an Mo-based ultrahigh tensile strength resistance welded steel tube used for structural members for automobile, etc., and excellent in tensile strength and ductility. ;CONSTITUTION: In a resistance welded steel tube having a composition consisting of, by weight, 0.15-0.30% C, 0.05-0.50% Si, 2.0-3.0% Mn, 0.005-0.020% P, 0.0005-0.0060% S, 0.01-0.08% Al, 0.001-0.003% B, 0.002-0.0050% N, 0.3-1.5% Mo, 0.01-0.20% Ti and/or 0.01-0.20% Nb, and the balance Fe with inevitable elements, normalizing is done as heat treatment and a microstructure composed essentially of bainite is formed. This method is economical because it can dispense with hardening after resistance welded steel tube making for forming an ultrahigh tensile strength resistance welded steel tube, and even square steel tubes and steel tubes of special form can be easily produced.;COPYRIGHT: (C)1993,JPO&Japio