How does brazing differ from welding?

• A. Brazing uses a filler metal that melts above 450°C while the base metals remain solid; welding fuses the base metals
• B. Brazing fuses the base metals; welding uses filler metal only
• C. Brazing welds the base metals by melting them; welding uses a third metal
• D. Both are identical processes

Answer: (A)

The key difference is whether the base metals are melted during the join. In brazing, the base metals stay solid while a separate filler metal is heated above 450°C, melts, and flows into the joint by capillary action. The filler metal then bonds to the surfaces as it cools, forming the joint without melting the pieces being joined. In welding, heat is high enough to melt the base metals themselves, fusing them together to form a metallurgical bond when they solidify. A filler metal may be used in welding, but the defining part is that the base metals are melted.

This is why the statement describing brazing as using a filler metal that melts above 450°C while keeping the base metals solid, and describing welding as fusing the base metals, is the best answer. Other options misstate the process by implying brazing fuses the base metals, or that welding always means using a filler metal, or that the two processes are identical.