Effect of Reheating on Low Temperature Toughness of Type 308L Austenitic Stainless Steel Weld Metal: —Low Temperature Toughness of Austenitic Stainless Steel Weld Metal (Report 5)—

An auther's previous paper had reported on the effect of heat-treating on the low temperature toughness of Type 316L weld metal. In this paper, the same study on Type 308L weld metal was carried out whose the heat-treating condition was at temperature from 923 to 1523K for time from 2s to 24h. In heat-treating the weld metal with δ ferrite above 2%, the absorbed energy decreased with increasing the amount of prior δ ferrite and particulary in the case of heat-treated temperature of 923K, degradation of absorbed energy was remarkable. This tendency was opposite to the result of Type 316L weld metal. This aws suggested that the addition of Mo was shifted Time-Temperature-Sensitization curve of the weld metal to the left side. In the other hand, the absorbed energy of fully austenitic weld metal was constant independent of heat-treating time and temperature. In the Type 316L weld metal reported previously, the absorbed energy tended to rise slightly by heat-treating for time up to 120s. In this Type 308L weld metal, however, such a tendency was not observed. This was considered to be attributed to somewhat good coherency of δ/γ intreface as compared to the case of Type 316L weld metal, in particular, in case of eutectic δ ferrite weld metal. The decomposition of δ ferrite in this Type 308L was somewhat slower than that in the Type 316L. This was considered to be due to good coherency of δ/γ interface.