PRODUCTION OF ELECTRIC WELDED PIPE

摘要

PURPOSE:To eliminate penetrators and cold junction defects and to obtain an electric welded pipe having high quality by limiting the distance between the center of squeeze rolls and a power feed means for heating and melting both ends of an open pipe as well as the rate of upsetting. CONSTITUTION:A pipe is manufactured by determining the spacing size l between a power feed means which heats and melts both opposed end faces of an open pipe OP and squeeze rolls 2 which join both end faces to each other by butt welding at >=3.2 times the pipe having >=30mm. outside diameter and determining the rate of upsetting at the rate equiv. to the wall thickness of the pipe or above. The electromagnetic force acting on both end faces of the pipe OP from the means 1 to the rolls 2 is thus considerably decreased to decrease the movement of the molten metal and to suppress generation of penetrators; moveover, the generated penetrators and cold junction defects are discharged to the outside by high upsetting. The reason for specifying the outside diameter of the pipe at >=30mm. lies in that if <30mm. the reactive current flowing in the inside surface of the open pipe OP increases sharply to make welding difficult.