In brazing, the filler metal melts at what temperature relative to the base metals?

• A. Above 450°C while the base metals remain solid
• B. Below 200°C
• C. At the same time as base metals melt
• D. It doesn't melt

Answer: (A)

In brazing, the filler metal is chosen to melt while the base metals stay solid. This means the filler’s melting temperature is above roughly 450°C, so you heat the assembly enough to melt the filler but not enough to melt the base metals. The liquid filler then flows into the joint by capillary action and bonds to the surfaces as it cools, forming a strong joint without melting the parts being joined.

That’s why the best description is that the filler melts at a temperature above 450°C while the base metals remain solid. If the filler melted at much lower temperatures, you’d be soldering rather than brazing. If the base metals melted too, you’d be doing fusion welding. If the filler didn’t melt, there would be no brazed joint.