In welding, what is the role of the third piece of metal?

In welding, the role of the third piece of metal, commonly referred to as filler material, is to assist in fusing the two separate pieces of base metal. This additional metal is melted during the welding process and flows into the joint between the workpieces, effectively filling any gaps and ensuring a strong bond. The filler material not only helps to join the two pieces together but also contributes to the overall integrity of the weld, allowing for improved mechanical properties in the completed joint.

Filler materials are chosen based on compatibility with the base metals and the specific application to ensure optimal performance. By filling in the joint, the filler material also helps to reduce the potential for defects such as porosity or cracks that can occur if the joint is inadequately filled.

In contrast, while stabilizing the joint, insulating the surface, or enhancing the finishing texture may be aspects linked to the welding process, they do not capture the primary purpose of the third piece of metal as effectively as the role of assisting in the fusion of two separate pieces.