MANUFACTURE OF HIGH TOUGHNESS ELECTRIC WELDED STEEL PIPE

摘要

PURPOSE:To manufacture an electric welded steel pipe whose weld zone has superior toughness at a low cost in the manufacture of an electric welded steel pipe by electric resistance welding, by heating and cooling the weld zone under specified conditions, and tempering it. CONSTITUTION:An electric welded steel pipe is manufactured by a conventional method. The weld zone of the pipe formed by electric resistance welding is heated to a temp. in the temp. range from the Ac3 transformation point preferably to about a temperature 200 deg.C higher then the Ac3 transformation point, and it is cooled at 15-30 deg.C/sec cooling rate from >=800 deg.C. When the roundness of the pipe is improved with a sizer after the tempering, it is desirable to carry out quenching at <=650 deg.C.