3.1.1. Frame Samples

Defects typical of aluminum weldings were observed including porosities and some incomplete penetration, as summarized in Figures 3 and 4. Figure 4 highlights some hot crackings (white circle) that occurred during MIG welding in the partially molten zone (PMZ). Indeed, the UNI ER-4043 filler wire increases the risk of liquation cracking because it decreases the local heat input and reduces the softening in the PMZ. Welds are usually inspected using liquid penetrant testing, which is a very valuable tool during new construction and in-service inspections. Figure 4 shows a liquid penetrant exam conducted during the quality tests of the present case study that revealed the presence of some incomplete penetrations of the joint. The geometries of the weld seam examined are essentially a "v" or "u" groove with a very different width, depending on the frame position.

**Figure 3.** Defects and microstructures of metal inert gas (MIG) frame joints. E-E combination.

**Figure 4.** Defects and microstructures of MIG frame joints. E-C combination.
