Heat-Affected Zone (HAZ)
Maximum temperature reached by the material is inversely proportional to distance from the fusion zone boundary
Structural changes in the material depend on the temperature to which the steel rises in the HAZ
Far from the weld where this temperature is less than ~650oC no structural changes occur
In the subcritical region (where temperature is between this and the eutectoid temperature (723oC)) some spherodising may occur