Brazing Alloys — Selection Guide

Brazing joins metals at temperatures above 840F (450C) but below the base metal’s melting point. The filler alloy flows into a tight-fitting joint by capillary action, creating a bond without melting the parts themselves. This makes brazing ideal for joining thin sections, dissimilar metals, and assemblies where heat distortion must stay minimal.

Silver brazing alloys (AWS BAg series) are the most versatile. BAg-1 (45% silver) flows at 1145F and works on steel, stainless, copper, and brass. BAg-5 (45% silver, cadmium-free) meets modern safety requirements while maintaining good flow. Higher silver content means lower melting point and better flow, but also higher material cost. Silver braze joints on properly fitted parts can exceed the strength of the base metal.

Brass brazing rods (RBCuZn series) cost less than silver alloys and work well for joining steel, cast iron, and copper. They require higher temperatures (around 1650F) and borax-based flux. Common applications include bicycle frames, furniture, and general repair work where cost matters more than precision.

Aluminum brazing uses BAlSi alloys with specialized flux or controlled-atmosphere furnaces. The narrow working temperature range (around 1080-1120F) makes aluminum brazing tricky. The flux is corrosive and must be cleaned off completely after joining. Most aluminum brazing happens in production furnace environments, not hand torch work.

Joint fit-up is critical for all brazing. Gaps of .001 to .005 inch produce the strongest capillary joints. Too tight and the filler can’t flow. Too loose and the joint weakens.

The guides below cover alloy selection by application, flux matching, and torch technique for consistent brazed joints.