Weld Mold 4320 description: Weld Mold 4320 is a copper alloy base, 8% tin bronze deposit that has excellent frictional resistance. 4320 is typically used for joining, build-up and repair applications. This versatile phosphor bronze rod can also be used for joining or surfacing of cast iron, bronze, red brass and joining dissimilar metals. Also used for the repair of gears, couplings, bushings and bearings.