| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for stably mass-producing electric resistance welded steel tubes superior in low temperature toughness.SOLUTION: The method for manufacturing the electric resistance welded tube includes forming a steel band, which contains 0.03-0.15% of C, 0.5% or less of Si, and 0.5-2.0% of Mn, in mass%, and further contains one or more selected from 0.1% or less of Nb, 0.1% or less of Ti and 0.1% or less of V, into a substantially tube-like open-tube, then butting and welding both edges of the open-tube. In the method, after giving tapers on both an outer surface side and an inner surface side of both the edges of the open-tube, electric-resistance welding is performed in an upset amount of 40-75% of steel band thickness. Thereafter, the welded outer surface after electric resistance welding is heated up to 960-1,250°C and cooled at a cooling rate of 10-50°C/sec from a temperature of 880°C or higher to 200-450°C, and then reheated to 500-780°C to be tempered as a series of heat treatment. |
