Aluminum Welding Flux
Anti Borax Welding Flux #8. Active temperature range, 1500-2900°F, 815-1540°C
"Ive tried them all and this is the best!" - Joe Stafford
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Aluminum, like all other metals, can be joined by many different methods. Fusion welding, however, has become an important method for fabricating aluminum. In fusion welding, only a fraction of the energy supplied contributes to the melting, and thus to coalescence. Most of the energy supplied leads to local heating of the base metal and the formation of a wide heat-affected zone (HAZ) around the weld joint. In aluminum, this zone represents a major problem, because the resulting micro structural changes lead to permanent mechanical degradation of the base material.
However, major micro structural changes do not occur during torch welding of aluminum. Heating is much gentler than with fusion welding, and no real heat-affected zone is formed. The problem is that aluminum and its alloys have a great affinity for oxygen. Aluminum molecules combine with oxygen molecules in air to form a tenacious, high-melting point oxide that covers the surface of the metal. Pure aluminum melts at only 1200°F; the oxide which protects the aluminum melts at 3700°F. Thus, the oxide does not melt during the welding process, and must be removed before the metal is welded. But this oxide will re-form on the aluminum if the aluminum is exposed to air during welding, and this is where flux comes into the picture.
Flux is essential when torch welding aluminum in air. When heated, flux performs five critical tasks:
Much goes into high-quality torch welding of aluminum. This includes excellent joint and fixture design, proper filler alloy placement, and good control of gas mixture parameters. But using the proper flux is essential in attaining the best outcome.
Courtesy of: Dr. Baskin at Superior Flux