Patent ID: 7866199

Claim:
A method for manufacturing a seamless steel pipe from a billet made of high Cr-high Ni alloy, which contains, by mass percent, 20 to 30% of Cr, 30 to 50% of Ni, and at least one element selected from Mo and W with a value “Mo+0.5W” of 1.5% or more, characterized by, heating the billet under conditions satisfying the following formula (1), and then piercing and rolling the billet using the inclined roll type piercing mill with a roll gouge circumferential speed of 2.28 m/sec or higher: T≦ 1575−4.45× V f −104.7×{−ln( t h /r o )} (1) wherein T indicates a heating temperature (° C.) of the billet, V f indicates the roll gouge circumferential speed (m/sec), r o indicates a radius (mm) of a billet at an entry-side, and t h indicates a radial thickness (mm) of a pipe after piercing.