Washington Alloy Silicon Bronze is a copper-based filler metal containing 3% silicon and small amounts of manganese, tin, and zinc. Primarily used for MIG, TIG, and oxyacetylene welding of copper, copper-silicon, and copper-zinc base metals to themselves and to steel. The oxyacetylene gas flame should be slightly oxidizing. Keep the weld puddle small in order to promote fast solidification and minimize cracking. A high boric acid flux should be used both before and during welding. Preheating is NOT recommended.