| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel tube with which even when heat stress is received by repeating the heating and the cooling, the scale on the inner surface hardly exfoliates. SOLUTION: (1) The steel tube including 9-28 mass% Cr and excellent in the exfoliating resistance for scale on the inner surface of the tube has the peculiarity, in which the maximum height of profile (Rz) on the inner surface after cold-working is≥15μm. (2) The steel tube including 9-28 mass% Cr and excellent in the exfoliating resistance for scale in the inner surface has the peculiarity, in which the maximum height of profile (Rz) on the inner surface after cold-working is≥15μm andΔHv is≥100. Wherein,ΔHv is the difference of Vickers hardness between the inner surface layer and the center part of the thickness direction of the tube. The above (1) or (2) steel tube desirably has the structure of ASTM austenite grain size No.7 or more. COPYRIGHT: (C)2007,JPO&INPIT
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