Which factor is essential for the proper flow of filler metal during brazing?

The proper flow of filler metal during brazing is critically dependent on correct heating. When the base metal is heated to the appropriate temperature, it allows the filler metal to reach its melting point and flow effectively into the joint. This process is essential because sufficient heat helps to create a capillary action that draws the molten filler metal into the spaces between the parts being joined.

If the heating is inadequate, the filler metal may not melt properly or may not penetrate the spaces as required, leading to weak bonds or incomplete joints. Conversely, overheating can cause issues such as excessive oxidation or deterioration of the base materials. Therefore, achieving the right temperature at the correct time is fundamental for successful brazing, as it ensures the filler metal can flow correctly and form a strong bond between surfaces.