Brass and Bronze Welding
Table of Contents
Brass and bronze welding (technically braze welding due to the lower temperature) has its challenges depending on the alloy. Zinc in particular is an alloy found in brass that has a low melting point. Both metals also have high heat conductivity. Tig welding is often the approach of choice for brass, although as pictured below, a strong weld can be achieved with Mig as well.
Bronze welding uses a bronze alloy filler to achieve joint strength. Both brass and bronze are applied using gas welding (oxy-acetylene), which is preferred due to the flame intensity.
When welding brass and bronze be sure to work in a well ventilated area using a respirator or fume extractor. Flux is used to remove iron oxide.
Tig and Mig Brass Welding
Low Brasses refer to a metal that is 90% to 95% copper and 5% to 20% zinc. Brasses of this type can be welded readily in all positions by the oxyacetylene process. Welding rods of the same composition as the base metal are not available. For this reason, 1.5 percent silicon rods are recommended as filler metal. Their weldability differs from copper in that the welding point is progressively reduced as zinc is added. Fluxes are required. Preheating and supplementary heating may also be necessary.
High Brasses are comprised of 55% to 80% copper and 20% to 45% zinc. These brasses can be readily welded in all positions by the oxyacetylene process. Welding rods of substantially the same composition are available. The welding technique is the same as that required for copper welding, including supplementary heating. Fluxes are required.
Bronze Welding Video
The aluminum bronzes are seldom welded by the oxyacetylene process because of the difficulty in handling the aluminum oxide with the fluxes designed for the brasses. Sane success has been reported by using welding rods of the same content as the base metal and a bronze welding flux, to which has been added a small amount of aluminum welding flux to control the aluminum oxide.
The welding of Copper-Beryllium Alloys by the oxyacetylene process is very difficult because of the formation of beryllium oxide
From a welding standpoint, copper-nickel alloys are similar to Monel, and oxyacetylene welding can be used successfully. The flame used should be slightly reducing. The rod must be of the same composition as the base metal. A sufficient deoxidizer (manganese or silicon) is needed to protect the metal during welding. Flux designed specifically for Monel and these alloys must be used to prevent the formation of nickel oxide and to avoid porosity. Limited melting of the base metal is desirable to facilitate rapid solidification of the molten metal. Once started, the weld should be completed without stopping. The rod should be kept within the protective envelope of the flame.
Oxyacetylene welding is the preferred method for joining nickel silver alloys. The filler metal is a high zinc bronze which contains more than 10 percent nickel. A suitable flux must be used to dissolve the nickel oxide and avoid porosity.
Oxyacetylene welding is not commonly used for welding the copper-tin alloys such as phosphor bronze. The heating and slow cooling causes contraction, with consequent cracking and porosity in this hot-short material. However, if the oxyacetylene process must be used the welding rod should be grade E (1.0 to 1.5 percent tin) with a good flux of the type used in braze welding. A neutral flame is preferred unless there is an appreciable amount of lead present. In this case an oxidizing flame will be helpful in producing a sound weld. A narrow heat zone will promote quick solidification and a sound weld.
Hot-short is defined as a marked loss in strength at high temperatures below the melting point.
Copper-silicon alloys such as silicon bronze are successfully welded by the oxyacetylene process. The filler metal should be of the same composition as the base metal. A flux with a high boric acid content should be used. A weld pool as small as possible should be maintained to facilitate rapid solidification. This will keep the grain size small and avoid contraction strains during the hot-short temperature range. A slightly oxidizing flare will keep the molten metal clean in oxyacetylene welding of these alloys. This flame is helpful when welding in the vertical or overhead positions.
References for Brass and Bronze Welding
Page Author: Jeff Grill