METHOD FOR FORMING RESISTANCE WELDED PIPE

PURPOSE:To uniformize a thickness of a small diameter thick walled pipe by disposing edge upset rolls preceding break-down rolls and increasing the radius of the end part of the prescribed upper break-down rolls by specified % of the wall thickness. CONSTITUTION:On the upstream of plural break-down roll stands 3, the edge upset rolls 2 with formed tapered parts are disposed. Further, the end part radius RET of the upper roll 32 of the break-down roll 31 is expanded by a range of 1-5% of the thickness (t) of a steel loop 1. By this method, the steel loop 1 is enlarged in its thickness of both end parts, then, formed by the break- down rolls 31 of the preceding stage, succeedingly, formed by stands 4, 5 of cage rolls and fin pass rolls. Because the thickness is thickened by rolls 2, further, the forming is reinforced by rolls 31, the thickness of the pipe is formed uniformly. Therefor, the thickness of the small diameter thick pipe is uniformized.