TWI Industrial Member Report Summary 28/1976
By J G Garland and N Bailey
The effects of C, S, P, Mn, Al, Nb and Si at two levels on the susceptibility to solidification cracking of submerged arc welds have been assessed in a quarter factorial experiment using the Transvarestraint test. Plate compositions were varied between 0.11 and 0.27%C, 0.007 and 0.05%S, 0.003 and 0.046%P, 0.05 and 0.64%Si, 0.5 and 1.5%Mn, 0.01 and 0.04%Al and <0.005 and 0.09%Nb. Welds were made with a l%Mn wire and a neutral alumina-based flux using constant welding conditions to give a deposit with 70% dilution.
The effects of C, S, P and Mn were found to be consistent with a previous full factorial experiment which examined their individual effects and interactions in detail. Nb was found to promote cracking, although less markedly than C, S, or P for a given addition, and niobium carbides were identified on crack surfaces. Si and Al both reduced cracking, the latter principally by its influence on transfer efficiency of the other deoxidants C, Si and Mn. Multiple regression analysis of the results showed that, in terms of weld metal composition, crack susceptibility could be expressed as being equal to:
223C + 197S + 10OP + 48Nb - 14.3Si - 6Mn - 16Al + 0.5.