*3.4. Evolution of the HAZ in Root Pass*

Figure 8 shows the evolution of the heat affected zone (HAZ) in the root pass for the standard GMAW welds in three different locations of the bead: start, middle and end. One can find that the arc wandering resulted in welds that are rather non-symmetrical. This was likely due to the inconsistency in penetration, associated with is incomplete fusion defect. Moreover, the size of the root face also contributed to this issue. In addition, one can note in Figure 8 that, as the weld progressed, the plate became hotter and consequently penetration was slightly increased in the end of the weld.

Figure 9 shows the root pass in three locations across the bead for CW-GMAW; no discontinuities (based on cross-sections inspection) were likely to occur in the root pass, and, generally, the sidewall penetration in the root was much more symmetrical due to the arc pinning to the cold wire. One finds that the increase in deposition decreased the penetration of the weld, causing incomplete penetration.

**Figure 8.** Root pass macrographs for the standard GMAW process: (**a**) start of the joint; (**b**) middle of the joint; and (**c**) end of the joint.

**Figure 9.** Root pass macrographs for the CW-GMAW process: (**a**) start of the joint; and (**b**) middle of the joint; and (**c**) end of the joint.
