METHOD FOR PRODUCING SEAMLESS PIPE AND HOLE TYPE ROLL

摘要

A method for producing a seamless pipe in which a mandrel bar of the same outside diameter can be employed even when the target thickness of the pipe is different, and partial thickness can be suppressed effectively in the circumferential direction of the pipe. The method for producing a seamless pipe comprises a step for drawing/rolling a pipe while altering only a hole type roll (1) arranged on a finish stand out of a plurality of rolling stands to a hole type roll satisfying the condition of expression (1) and having a different radius R1 of curvature at the bottom of groove for every target thickness when there are a plurality of target thickness wt of pipe after drawing/rolling. -0.1mm≤(1-cosϑ)·S≤0.1mm ...(1) In the expression (1), ϑ is expressed by ϑ=90/i(°) when the number of hole rolls arranged on each rolling stand is i(i=2 through 4), and S means the offset amount (mm) of the hole roll.