METHOD AND DEVICE FOR HOT MANUFACTURE OF STEEL PIPE

PURPOSE:To stabilize the operation for long time in the hot production line of a steel pipe by forming the skelp heated within the prescribed temp. range in the cylindrical shape having an open seam and by welding the seam part with a high frequency resistance welding method. CONSTITUTION:A skelp 1 is passed to a preheating furnace 2 via a turn roller 3 and the skelp 1 preheated at 450-700 deg.C is fed to a forming roll device 6 via a turnaround roll 4. The skelp 1 formed in the cylindrical shape having an open seam upwards by the roll device 6 is completely joined by welding at its seam part by a high frequency resistance welding machine 7 and welding roll 10. The welding machine 7 incorporates a contact piece 9 in square or hexagonal shape rotatable to the pivot 8 for feeding and performs the feeding to the seam part of the skelp 1. In this way the stabilization of the continuous operation for long time in the hot production line of a steel pipe is realized.