Metallurgy Question:

Heat affected zone is measured regarding the microstructure changes in the weld. For example in steels, this is the area around the weld zone, which has undergone a transformation. In other words, this is the area, which had been austenitized. For calculating the HAZ after welding, for steels, it is better to macroetech the section of the weld HAZ can be easily recognized by the contrast it makes with the base metal and the weld metal.