During the brazing process, which part of the flame should not touch the base metal?

In the brazing process, it is important that the cone of the flame does not touch the base metal. The cone contains the hottest part of the flame, where temperatures can be high enough to directly affect the integrity of the base metal. If the cone touches the base metal, it can lead to overheating, which might cause warping, burning, or other damages to the material.

The tip of the flame, while producing a concentrated heat, is not usually directed towards the material itself in a typical brazing application. The base of the flame typically has less heat than the cone and the feather, which is the outer part of the flame, provides a protective atmosphere that does not directly interact with the metal. Thus, it’s critical to maintain the correct flame placement to achieve a successful brazing without compromising the properties of the base metal.