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About Brazing
Brazing or soldering is heating two metal parts to more than 800 degrees Fahrenheit in order to connect them using metal filler rods and flux. Flux protects the joint between the two metal parts from oxidation. Filler rods may consist of aluminum-silicon alloys, silver-base alloys or copper-zinc alloys. A handheld oxyfuel gas torch is the most common heating source for brazing.
Brass Brazing
Brass brazing is for steel that has not been heat-treated. Compared to silver, brass is less expensive and allows for wider tolerances in tube mitering and temperature control. Brass or bronze brazing is common among beginning metal frame builders. Do not use brass or bronze brazing for heat-treated steel, as the higher melting temperatures will weaken the steel.
Silver Brazing
Silver alloys melt at lower temperatures than brass and bronze, resulting in stronger joints. Silver alloys work well for wicking into very fine joints. Silver brazing alloys contain up to 60 percent silver and are effective for connecting heat-treated and stainless steel pieces. One problem with silver alloys is that some contain cadmium, a poisonous metal with toxic fumes. For this reason, only experts should use them and with proper ventilation equipment. For home use, look for cadmium-free alloys.
Nickel Silver Brazing
Despite the name, nickel silver alloy does not contain silver, but nickel and copper instead. Alloys containing nickel help prevent corrosion between the filler metal and base metal. Nickel alloys have higher melting temperatures and won't work well on heat-treated steel.
Brazing vs. Welding
Compared to welding, torch brazing increases work speed, is easier to learn and results in less burn-through of thin sheet metal or pipe. Brazed joints typically do not require grinding or finishing. A BenzOmatic torch is much more portable and less costly than the equipment required for welding.