Brass is any copper and zinc alloy with a broad range of physical properties, depending on the specific composition. It is often used for applications requiring low friction, in decorations and to construct certain musical instruments. Brass has a melting point in the 900- to 940-degree F range and is relatively easy to cast.
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Use oxyacetylene to weld brass in most cases. Oxygen and acetylene are stored in separate containers and mixed when welding. It is essential that the zinc content is known before attempting to weld brass because zinc has a much lower melting point than copper.
Mix a flux with water to make a paste and paint the surfaces to be welded. Use a braze-welding flux or a flux specifically formulated for oxyacetylene welding.
Reduce the acetylene flow until you have a strong oxidizing flame just sufficient to produce coating on the base metal. You want the flame to have enough oxygen to prevent zinc fumes from coming off the metal, but not so much that the coating makes welding more difficult than it needs to be.
Employ a high quality braze welding filler if the color does not need to match the metal. Low zinc brass can actually be braze welded instead of fusion welded because of copper's relatively high melting point.
Because of brass's high heat conductivity, use a welding tip at least one size larger than the tip you would use for steel of the same thickness.