TWI Industrial Member Report Summary 135/1981
By T G Davey and P H M Hart
Experimental work has been carried out to examine the effect of weld preparation type on heat-affected zone (HAZ) hydrogen cracking in MMA butt welds in 25mm thick C-Mn-Si-Nb steel. The critical hardnesses and arc energies have been determined for K and single-V preparations at different levels of tensile
restraint (RF) and weld metal hydrogen.
Considered in conjunction with the earlier work of Harasawa and Hart on double-V preparations, marked changes in the risk of cracking were observed due to the effect of weld preparation on the geometrical stress concentration factor and on root strain. The latter effect resulted largely from the weld
eccentricity gamma, negative values of gamma being beneficial.
The Japanese welding cracking parameters Pw, and Ph, and The Welding Institute procedure prediction nomogram were found to give unsafe welding procedures under certain conditions when compared with the experimental results.
A tentative modification to The Welding Institute procedure prediction nomogram is proposed for butt welds, on the basis of this work.