Weld Mold 4940 description: Weld Mold 4940 is a copper, nickel, chromium, aluminum bronze bare wire. Weld Mold 4940 has excellent thermal conductivity wear resistance and corrosion resistance. A high performance, high thermal conductivity copper alloy commonly utilized by the injection and blow molding industries as well as others in the molding industry as an alternative product for welding beryllium copper. Also used for welding Ampco 940 molds.