METHOD FOR PRODUCING SEAMLESS PIPE AND HOLE TYPE ROLL

摘要

There is provided a method for manufacturing a seamless pipe or tube and a grooved roll with which, even when the target wall thickness of pipe or tube is different, a mandrel bar having the same outside diameter can be used, and the wall thickness eccentricity along the circumferential direction of the pipe or tube can be effectively suppressed. A method for manufacturing a seamless pipe or tube according to the present invention includes a step of drawing and rolling a pipe or tube wherein the step of drawing and rolling comprises, in a case where there exist a plurality of target wall thicknesses of pipe or tube after drawing and rolling, preliminary replacing only the grooved rolls disposed in the finishing stand among the plurality of rolling stands with grooved rolls each of which meets the requirement given by the following expression (1) and each of which has a groove bottom radius of curvature differently depending on a target wall thickness of pipe or tube after drawing and rolling, and drawing and rolling a pipe or tube by using the replaced grooved rolls, -0.1mm≤1-cos θ⋅S≤0.1mmwhere θ is an angle expressed by θ = 90/i degrees if the number of grooved rolls disposed in each rolling stand is i (i = 2 to 4), and S is the offset amount (mm) for the grooved roll.