What is the purpose of filler metal in GMAW?

The purpose of filler metal in Gas Metal Arc Welding (GMAW) is primarily to add strength and mass to the welded joint. During the welding process, the filler metal is melted and deposited into the joint between the two base metals being welded. This molten metal fuses with both the base metals and solidifies, creating a stronger and more cohesive connection. The inclusion of filler metal not only reinforces the joint by ensuring a proper fusion but also compensates for any gaps or irregularities in the joint area, leading to enhanced structural integrity.

The other options suggest purposes that do not fully describe the primary function of filler metal in the welding process. For example, while it is true that controlling the heat can help prevent oxidation, stabilizing the arc directly relates more to the welding equipment and techniques rather than the filler metal itself. Additionally, cooling the weld joint or removing impurities can be elements of the welding process, but they do not capture the primary role of the filler material in enhancing the weld's mechanical properties.