What joining process uses heating to a suitable temperature and a filler metal that liquifies above 449 °C (840 °F) and below the solidus of the base metal?

• A. Welding
• B. Soldering
• C. Brazing
• D. Solid State Welding

Answer: (C)

Brazing is being described. In brazing, you heat the joint just enough to melt a filler metal, but you leave the base metals solid. The filler metal then flows into the joint by capillary action and bonds to the base metals as it cools. The filler’s melting point is above 449 °C (840 °F) and below the solidus of the base metal, so the base metals don’t melt themselves. This combination—liquified filler metal with solid base metals—distinguishes brazing from welding (where the base metals melt) and soldering (where the filler melts at even lower temperatures). Solid-state welding involves bonding without any melting of either metal.