TWI Industrial Member Report Summary 101/1979
By N Bailey and R J Pargeter
Tests made to examine the influence of the flux on the strength and toughness of two-pass submerged arc welds deposited with an arc energy of 5.6kJ/mm in 30mm thick mild steel (1) have been extended to include welds made with basic fluxes. Tests have also been carried out to examine the effect of COD notch type and position of Charpy V notch test specimens.
The earlier conclusions, based on tests on 19mm plate, that basic fluxes gave the best resistance to both cleavage and microvoid coalescence, have been confirmed. These welds all had relatively coarse microstructures containing less than 50% acicular ferrite.
Specimens extracted from each pass of the two-pass welds gave significantly higher Charpy V transition temperatures than specimens from the root. However, changing the direction of COD notching from through the thickness (on a 4:3 W:B ratio specimen with a square ligament) to surface notching (on a square specimen notched and cracked 25% through the thickness) did not significantly affect the transition temperature.
Taking the results as a whole, it was found that increasing the weld metal Mn content in the range 0.8-1.3% and decreasing Si (0.45-0.1%) and N (0.014-0.004%) improved cleavage resistance in terms of the COD transition temperature.