EFFECT OF delta FERRITE ON LOW TEMPERATURE TOUGHNESS OF TYPE 316L AUSTENITIC STAINLESS STEEL WELD METAL - LOW TEMPERATURE TOUGHNESS OF AUSTENITIC STAINLESS STEEL WELD METAL (REPORT 1).

In notch toughness test of as-welded specimens at 77 and 103 K, there was no simple correlation between the notch toughness and delta -ferrite content, differing from the results of other previous studies relative to this research. In more than about 3% delta -ferrite, the notch toughness increases with delta -ferrite content and reaches a maximum values at about 7% delta -ferrite. The solidification structure indicated that in the 3% delta -ferrite specimen of minimum notch toughness, an eutectic delta -ferrite appeared and furthermore with increasing delta -ferrite content, the morphology alters to vermicular and then lathy ferrite. In heat treating the specimens at 923 K for 100 h, the absorbed energy decreased dramatically with increasing prior delta -ferrite content. This was considered because delta -ferrite changed to sigma phase and carbide by heat treating.