Solidification Crack Susceptibility in Weld Metals of Fully Austenitic Stainless Steels (Report III) : Effect of Strain Rate on Cracking Threshold in Weld Metal during Solidification

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The present study was undertaken to obtain a better understanding of solidification and ductility-dip crackings occurring in fully austenitic stainless steel weld metals of SUS 310S using a combination of the Slow-Bending speed type Trans-Varestraint test and a fractographic method by the scanning electron microscopy. The cracking threshold curve showing the nucleation property of solidification cracking was first obtained by varying combinations of strains and stain rates, so that the cracking threshold curve appeared to be almost identical with the ductility curve of BTR showing the propagation property of solidification cracking obtained by the Trans-Varestraint test. The solidification crack was likely to occur because of the lowest ductility in spite of the strain rate within the higher temperature range of the BTR over which the crack surface morphology showed a dendritic appearance as an evidence of liquid, while ductility-dip cracking became unlikely to occur as the strain rate decreased. Moreover, it is concluded that the surface morphology of solidification cracks was divided into three distinct types and was closely related to the separation temperature at which cracking occurred in spite of the effects of the augmented-strain and the strain rate.
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