PLASMA CUTTING METHOD OF SPIRAL WELDED PIPE

摘要

PURPOSE:To minimize generation of fumes by increasing an arc current value to the value optimum to the thickness of a spiral pipe only when a plasma-cutting torch passes through the weld seam part of the spiral pipe. CONSTITUTION:A timer T is provided to a driving source M of a flying cutter 4 and the time (t) until a cutting torch 6 intersects with a weld seam 3 where traveling starts is set to the timer T; at the same time, the timer T is so arranged that the signal therefrom is transmitted to an arc current regulator 10. The plasma arc current is increased up to the current value optimum for the thickness l+alpha of the weld seam 3 only during the time when the torch 6 passes through the seam 3 upon emission of the limit signal of the set time (t) from the timer T. Therefore, the torch 6 starts traveling and the plasma arc current value is automatically controlled at all times to the current value optimum for the thickness of a spiral pipe 5 until said torch finishes cutting the pipe.