抄録
The effects of cold drawing and heat treatment on the stress corrosion cracking (SCC) behavior of stainless steel having two phases of α and γ were studied in boiling 42% MgCl2 solution. It was found that the effect of cold drawing on SCC susceptibility was remarkable, and when applied stress was 8.3, 25kg/mmmm2 or 38% of Y.S., the maximum SCC susceptibility was observed in the specimens drawn at 15% and 60% after solution treatment. The critical stress on the SCC was observed in a undeformed specimen, but it was not observed in those which were subjected to cold drawing. The restraining effect of α on the propagation of cracks was not observed in all the specimens, on the contrary, the cracks were propagated in α preferentially in the 60% cold drawn specimen. On aging at 475°C, the change in hardness showed a two-stage hardening behavior. At the second stage of the hardening (aging for 100h or longer) the SCC susceptibility of the cold drawn specimen was decreased and did not fail event after 104min. This phenomenon may be interpreted by assuming the two phases separation of α-phase. On aging at 700°C from 5 to 17h or more, the SCC susceptibility was excessively increased, and at the same time the transformation of α→γ+σ occurred. This transformation had a detrimental effect on the SCC susceptibility because a volume fraction of α was varied, and furthermore σ promoted local corrosion and embrittlement of the specimens.
