How to Weld Bronze

Bronze is a copper alloy that usually has tin as the primary alloying agent, although alloys with other elements such as aluminum, manganese, phosphorus and silicon also are considered bronzes. It has been made for more than 5,000 years but it is only in the last few decades that welding bronze in the modern sense has been possible.

Instructions

Difficulty: Moderately Challenging

1. Weld bronze by melting a filler rod of the same composition and fusing it so that the joint is visually and mechanically seamless. Brazing bronze is much easier and is simply the process of melting the filler material over the joint and allowing it to cool.
2. Understand that only certain types of bronze can be welded. A common bronze of copper, tin and a small amount of zinc known as gunmetal can't be welded. This bronze forms a coating of lead on the surface when heated and the weld is mechanically weak. Phosphor bronze, on the other hand, is easily weldable.
3. Use a filler material of silicon bronze with about 3 percent silicon to weld silicon bronze.
4. Employ phosphorus filler with 5 percent tin and less than 0.35 percent phosphorus to weld phosphorus bronze.
5. Implement gas tungsten arc welding or gas metal arc welding to weld bronze. Minimize hot cracking by keeping the weld pool small and the temperature below 150 degrees F between passes. The welding time should be minimized as much as possible.

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