TWI Industrial Member Report Summary 25/1976
By J G Garland
A study has been made of the effects of parent plate yield strength, preheat, and composition upon the incidence of solidification cracking in submerged arc welds in C-Mn steels.
Increasing the yield strength of the parent plate by 180N/mm2 doubled the amount of centreline solidification cracking in weld metals of the same composition in simple double V butt welds. Multiple solidification cracking, i.e. centreline and interdendritic, occurred in highly restrained fillet welds with a narrower root gap in a steel with a high yield strength than in a lower yield strength steel of the same composition.
Both general preheat and preheat localised to the area of the joint reduced the likelihood of solidification cracking in an assembly where distortion due to preheat was minimised. The full extent of cracking depended critically on the techniques of preheat-ing, locally preheated welds being more liable to solidification cracking.
Compositional factors in the weld metal, as well as parent plate strength, were important in determining the pattern and extent of solidification cracking. The particular variations in composition studied in this work promoted centreline solidification cracking in previously crack-free runs and multiple solidification cracking in more severe joint configurations. The effect of weld metal composition upon solidification cracking will be considered in greater detail in a subsequent report.