How can preheating affect the flow of brazing filler metal?

Preheating is an important technique in the brazing process, and it can significantly enhance the flow of brazing filler metal. When components are preheated before the application of the filler metal, the temperature of the base materials is elevated. This not only helps to reduce thermal shock during the brazing process but also facilitates better wetting action of the filler metal on the surfaces being joined.

The improved flow of the filler metal occurs because the increased temperature decreases the viscosity of the molten filler. A lower viscosity allows the brazing material to flow more easily into the joint area, ensuring complete infiltration and coverage of the surfaces to be bonded. This is particularly critical in tight-fitting joints where proper capillary action is necessary for optimal bonding.

Effective heat management allows the filler metal to flow freely, achieving a strong, consistent joint. Therefore, preheating is a key practice that positively influences the overall brazing process and the quality of the resulting joint.