Oxy-Acetylene Welding of Copper, Brass & Bronze
Copper conducts heat more rapidly than any other commercial metal. It will oxidize very easily and this oxidation is not easily apparent to the operator, but the weld becomes very brittle. The melting point is under that of steel and iron, yet because of its high conductivity a larger tip for the same size material is necessary. Cold, copper is very ductile hot, it is brittle; so care must be used when welding, since at a high heat it is very likely to fracture, either at the weld or some distance away, since the heat is conducted so rapidly that the temperature of the metal some distance from the weld is but little less than at the weld.
The metal should be prepared for welding the same as others, the V properly made, and the metal thoroughly clean. Copper should be preheated to prevent contraction cracks or strains, owing to the high conductivity of the metal, it will cheapen the welding operation considerably to heat it by other means than the oxyacetylene flame.
The welding of copper is quite difficult to realize and maintain ductility. A special welding rod is necessary containing an element opposing the action of oxygen on the copper and a flux for the same purpose as well. The cone should not come in direct contact with the metal at any time. For repair purposes, it is sometimes not practical to weld the break, and we then braze it, either with brass or bronze, using the brass flux for this purpose and following the same general directions as for brazing malleable iron.
Oxy-Acetylene Welding of Brass & Bronze
Brasses and bronzes are composed of copper, with lower melting point metals as alloys., zinc, tin, etc. Since these metals have different melting points, considerable care must be exercised in welding not to change the characteristics of the metal too much by burning out these alloys.
The metal should be prepared the same as any other, with particular care in setting up to prevent movement while being welded and to prevent collapse of the heated area. The metal should not be brought to fusion by bringing the cone in contact with it, but as with copper, the end of the cone should be slightly above the metal.
For repair purposes, bronze or brass should be used for the welding filler rod-for foundries or in manufacturing where the weld must be practically the same color and the same material as the metal, more judgment is necessary in the choice of the rod, with a view of replacing, by means: of the material in the welding rod, those metals burnt out of the line of welding by the flame.