AUSTENITIC STAINLESS STEEL TUBE HAVING EXCELLENT WATER VAPOR OXIDATION RESISTANCE AND PRODUCTION METHOD THEREOF

摘要

PROBLEM TO BE SOLVED: To provide an austenitic stainless steel tube which has a wholly uniform, regulated, fine-grained structure where grains are not coarsened even when reheated to high temperature by welding or high temperature bending, and which maintain satisfactory oxidation resistance in moisture, and to provide a production method thereof.;SOLUTION: The austenitic stainless steel tube comprises 0.03 to 0.12% C, 0.1 to 0.9% Si, 0.1 to 2% Mn, 15 to 22% Cr, 8 to 15% Ni, 0.002 to 0.05% Ti, 0.3 to 1.5% Nb, 0.0005 to 0.03% sol.Al, 0.005 to 0.2% N and 0.001 to 0.008% O (oxygen), and the balance Fe with impurities, and has a fine-grained structure having an austenite grain size number of ≥7, and, preferably, having a grain mixing ratio of ≤10%. The production method includes (1) a process for heating and holding at 1,100 to 1,350°C, and then cooling at a cooling rate of ≥0.25°C/sec, (2) a process for plastic processing in the temperature range of ≤500°C at a reduction in area of ≥10%, and (3) a process for cooling after heat and holding at a temperature that is in the range of 1,050 to 1,300°C and lower than the heating temperature in the process (1) by ≥10°C.;COPYRIGHT: (C)2003,JPO