| 摘要 |
PROBLEM TO BE SOLVED: To provide plugs with long life for making the seamless pipes that have excellent properties at their inside surfaces, even at the rolling of plug mills for 13 and over volume % chromium-containing steels and nickel group alloy steels. SOLUTION: The plug has the scale layer on a base metal including 5 and over volume % ferrite base spinel oxide into which chromium of the thickness from 100 to 300 μm and Vickers hardness from 5 to 20 at the temperature of 1,000 deg.C is solved. Vickers hardness at part of the base metal from its surface to 5 mm depth at the temperature of 1,000 deg.C is 15 and over. |
