What indicates the temperature target has been reached in a brazing cycle?

• A. Filler metal melting and complete flow into the joint.
• B. The base metal temperature reaches a predetermined color change.
• C. Flux completely evaporates during heating.
• D. The joint surface shows oxide scale only.

Answer: (A)

Reaching brazing temperature is shown by the filler metal melting and flowing into the joint. When the filler melts, it wets the surfaces and is drawn into the joint by capillary action, filling the gap and allowing a proper braze to form. This wetting and flow directly indicate the target temperature has been achieved and you can proceed to hold and then cool the joint.

Color changes in the base metal or flux evaporation aren’t reliable indicators of the correct temperature, since they can occur inconsistently and don’t guarantee that the filler is melting or wetting the joint. Seeing oxide scale alone suggests insufficient cleaning or poor wettability, not that the brazing temperature has been reached.