Ferritic stainless steel sheet having superior workability at room temperatures and mechanical characteristics at high temperatures, and method of producing the same

摘要

A ferritic stainless steel sheet which has not only superior high-temperature fatigue characteristics, but also superior workability at room temperatures. The steel sheet contains, by weight percent, C: not more than 0.02 %, Si: 0.2 to 1.0 %, Mn: not more than 1.5 %, Cr: 11.0 to 20.0 %, Ni: 0.05 to 2.0 %, Mo: 1.0 to 2.0 %, Al: not more than 1.0 %, Nb: 0.2 to 0.8 %, and N: not more than 0.02 %, balance essentially Fe, and an aspect ratio (d_RD/d_TD) of grain size in planes at 1/4 and 3/4 sheet thickness, seen a direction normal to a sheet surface, in the range of 1.03 to 1.35. The steel sheet has a thickness greater than 0.3 mm but not greater than 2.5 mm, and a yield strength Y.S. ≤ 360 MPa and an r-value ≥ 1.3 at 30°C, and wherein after maintaining the steel sheet at 900°C for one hour, the Y.S. ≥ 18.0 MPa.