Effect of cold working on the thermal fatigue properties of austenitic stainless steels

The effect of cold working on the thermal fatigue properties of austenitic stainless steels has been investigated under 200/7000C and 200/8000C temperature cyclings. The main results obtained are as follows. (1) The effect of cold working on the thermal fatigue lives (N sub(f)) of SUS304 was feeble, and that of SUS316 was remarkable under 200/7000C temperature cycling. The N sub(f) of SUS316 increased considerably with rolling reduction. (2) The effect of cold working on the N sub(f) of SUS304 and SUS316 was almost th e same under 200/8000C temperature cycling. The N sub(f) of the 10% rolled steels were thelowest among these steels. (3) Recrystallization occurred more easily in SUS304 than SUS316 at temperatures not exceeding 7000C. Recrystallization behavior was almost the same in SUS304 and SUS316 at 8000C. Therefore it is inferred that recrystallization has a large influence on the N sub(f) of cold-rolled materials. The N sub(f) of SUS304 and SUS316 were affected by the tensile strength rather than the ductility. (4) The N sub(f) of SUS321 and NSSERl (19Cr-13Ni-3.5Si-Nb) increased with r olling reduction in uninterrupted tests under 200/7000C temperature cycling. (5) Then N sub(f) of SUS321 and NSSERl decreased with rolling reduction under 2 00/7000C temperature cycling with hold time and under 200/8000C temperature cycling. These phenomena are due to the lowering of the toughness at elevated temperature, which is caused by remarkable precipitation taking place during thermal fatigue. (author)