| 摘要 |
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 is heated under conditions satisfying the following formula (1), and then the billet is pierced and rolled using an inclined roll type piercing mill with a roll gouge circumferential speed of 2.28 m/sec or higher. This prevents melted rash on the inner surface and lengthens the plug life. T≰1575−4.45×Vf−104.7×{−ln(th/ro)} (1) wherein T indicates a heating temperature (° C.) of the billet, Vf indicates the roll gouge circumferential speed (m/sec), ro indicates a radius (mm) of a billet at an entry-side, and th indicates a radial thickness (mm) of a pipe after piercing.
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