| 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 + 0.5 W" 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 × V f - 104.7 × - ln t h / r o
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 tn indicates a radial thickness (mm) of a pipe after piercing. |
