Method for Producing Seamless Pipe

Abstract

Disclosed is a method for producing a seamless pipe by using a piercing mill which pierces and rolls a round billet heated to 1300° C. or lower, wherein the piercing mill is composed of a pair of skew rolls disposed to face each other around a pass line, a pair of guide devices disposed to face each other around the pass line, and a plug disposed along the pass line, between the pair of the skew rolls and also between the pair of the guide devices, wherein the piercing-rolling is performed under the conditions satisfying the following formulas (1) to (3) to prevent wrinkle flaws of the seamless pipe: −1.0<Δθ  (1) Δθ=θp−θr  (2) −0.37×Δθ+1.47≦Rn≦0.37×Δθ+2.67  (3) wherein the meanings of the individual symbols in the above-described formulas are as follows: θr: The half angle (°) between the pass line and the main roll face in the condition of the feed angle of the main rolls being zero θp: The half angle (°) between the pass line and the reeling section of the plug Rn: The number of times of the reeling of the plug

Dependencies are inferred from the claim text.