This paper concentrates on the form of the hardness gradient
in the heat affected zones (HAZs) produced by submerged arc
welding of two low-carbon Q & T steels. The results show
unequivocally that the gradient differs from that found in
steels of lower carbon equivalent in that the peak HAZ hardness
is displaced from the grain coarsened heat affected zone
(GCHAZ) into the grain refined heat affected zone (GRHAZ).
Weld thermal cycle simulation has been used to confirm the
results obtained from actual welds and to clarify the cause of
this unexpected phenomenon.