TWI Industrial Member Report Summary 26/1976
By N Bailey
The influence of flux and wire on the solidification cracking of low dilution submerged arc welds has been examined with the Transvarestraint test. Although carbon is the most deleterious element, reducing its content below 0.08%C in the weld does not further reduce the likelihood of solidification cracking. A revised predictive formula based on weld composition, containing the term C* with a minimum value of 0.08 to allow for a discontinuous effect of carbon, has been developed. Cracking susceptibility is equal to: 230C* + 190S + 75P + 45Nb - 12.3Si - 5.4Mn - 14Al - 1.
All low dilution welds, except those made with highly hasic fluxes, contained more oxygen than previous high dilution welds. The test results did not, however, support the view that oxygen in the welds is beneficial as such, although a high weld oxygen content is indicative of a large reduction in carbon content on welding.
Increasing the Mn content of the wire from 0.5 to 2% was beneficial, but in a high dilution situation, where cracking normally occurs in practice, the effect would only be helpful in marginal cases.
There was some evidence that titanium and lead were harmful and molybdenum beneficial. No effect could be detected from 1%Ni in the weld.
No simple relationships were found between flux type, as expressed by a basicity index, and either composition or cracking behaviour.