What is a fillet in the context of soldering or brazing?

In soldering and brazing, a fillet refers to the bead of solder or braze metal that forms at the joint where two surfaces meet. This bead is crucial for ensuring a strong bond between the materials being joined, as it helps to bridge any gaps and creates a robust connection when cooled and solidified.

The formation of a fillet is an important aspect of the soldering and brazing process because it directly impacts the mechanical strength and integrity of the joint. A well-formed fillet should have a smooth and consistent appearance, demonstrating that the solder or braze metal has adequately flowed into the joint and filled any voids.

Other options, while related to soldering and brazing, do not encapsulate the definition of a fillet accurately. For instance, the molten solder used for filling gaps refers to the liquid state of the material before it solidifies, but it does not define the fillet itself. Cleaning agents are important for ensuring proper adhesion but are not related to the joint's appearance. Tools used to apply heat are also essential to the process, but they do not pertain to the definition of a fillet.