Understanding Filler Metal in Braze Welding

Braze welding is a metal joining process where a filler metal is heated above its melting point and distributed by flowing into the joint, but unlike brazing, it does not rely on capillary action to draw the filler metal deeply into a tight joint. Instead, the filler metal is typically deposited at the joint area, similar to how filler metal is applied in arc welding processes, but using lower temperatures.

How Filler Metal Works in Braze Welding vs. Brazing

It is important to distinguish braze welding from brazing. While both use a filler metal that melts below the base metal's melting point, their methods of applying the filler metal and preparing the joint differ significantly.

• Brazing: This process relies heavily on capillary action. The filler metal melts and is drawn into the narrow gap between closely fitted joint surfaces by capillary forces.
• Braze Welding: This process uses filler metal to build up a bead at the joint, much like traditional welding. The joint preparation often involves bevelling edges, and the filler metal is deposited from a rod or wire directly onto the joint surface, forming a fillet or groove weld shape. Capillary action may play a minor role in wetting the surface, but it is not the primary mechanism for distributing the bulk of the filler metal or filling the joint volume.

Analyzing the Options

Let's evaluate the given options based on the characteristics of braze welding:

• A. Distributed by capillary attraction: This is the primary method of filler metal distribution in standard brazing, not braze welding.
• B. Melted and deposited at the point where the weld is to be made: This accurately describes how the filler metal is applied in braze welding. The filler metal is melted and added to build up the joint area.
• C. Not required: Filler metal is absolutely required in braze welding to create the joint.

Conclusion on Braze Welding Filler Metal Application

Based on the analysis, the statement that best describes the filler metal in braze welding is that it is melted and deposited at the point where the weld is to be made. This differentiates it from brazing, which relies on capillary action.