What joining process fuses materials by heating them to their melting temperature?

Welding is the joining process that fuses materials by heating them to their melting temperature. In welding, the materials—typically metals—are heated until they reach a state where they can flow together. This process not only joins the pieces but also creates a strong bond as the molten material cools and solidifies, forming a robust connection often stronger than the original materials.

Welding has various techniques such as arc welding, MIG welding, and TIG welding, each tailored to different types of materials and thicknesses. The ability to reach and maintain such high temperatures is critical in welding, making it distinct from other joining methods, which typically do not reach the melting point of the materials involved.

The other options, such as soldering, adhesive bonding, and riveting, involve different mechanisms of joining. Soldering uses lower temperatures that do not melt the base materials, while adhesive bonding relies on chemical adherence rather than melting. Riveting involves mechanical fastening rather than a fusion of materials. This is why welding is the correct answer for the defined process that specifically involves fusing materials through heat to their melting point.