What condition is an indicator of overheating during the brazing process?

Burn marks on the substrate are a clear and direct indicator of overheating during the brazing process. When the substrate undergoes excessive heat, it can lead to local burning, which results in visible marks or discoloration on the material. These burn marks may not only compromise the aesthetic quality of the joint but can also weaken the base material, affecting its structural integrity and overall performance.

While other factors, like a deformed joint shape or a color change in the filler material, may also suggest overheating, they could arise from other issues in the brazing process that are not necessarily tied to extreme heat. Excessive smoke production can indicate that the flux or other materials are decomposing, but it is not a definitive sign of overheating the joint itself. Therefore, burn marks provide the clearest visual evidence of the detrimental effects of excess heat on the substrate during brazing.