Topics related to brazing to aid with learning and understanding the technical aspects of brazing, how brazing works, why it works, along with useful hints and tips.
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In brazing, there is always the possibility of dangerous fumes and gases rising from base metal coatings, ink and cadmium-bearing filler metals, and from fluorides in fluxes. The following well-tested precautions should be followed to guard against any hazard from these fumes.
1. Ventilate confined areas. Use ventilating fans and exhaust hoods to carry all fumes and gases away from work, and air supplied respirators as required.
2. Clean base metals thoroughly. A surface contaminant of unknown composition on base metals may add to fume hazard and may cause a too rapid breakdown of flux, leading to over heating and fuming.
3. Use sufficient flux. Flux protects base metals and filler metal during heating cycle. Full flux coverage reduces fuming. Also, consult your MSDS regarding specific hazards associated with brazing flux.
4. Heat metals broadly. Heat the base metals broadly and uniformly. Intense localized heating uses up flux, increases danger of fuming. Apply heat only to base metals, not to filler metal (direct flame on filler metal causes overheating and fuming).
5. Know your base metals. A cadmium coating on a base metal will volatilize and produce toxic fume during heating. Zinc coatings (galvanized) will also fume when heated. Learn to recognize these coatings. It is recommended that they be removed before parts are heated for brazing.
6. Know your filler metals. Be especially careful not to overheat assembly when using filler metals that contain cadmium. Consult the Material Safety Data Sheet for maximum recommended brazing temperatures of a specific filler metal. The filler metal carries a warning label. Be sure to look for it and follow the instructions carefully.
(For other safety considerations, see the American National Standard Z49.1, "Safety in Welding and Cutting", published by the American Welding Society (AWS), 550 N.W. LeJeune Rd., Miami, Florida 33126.)