Weld Mold 750 description: Weld Mold 750 is for the repair and joining of heavy sections of cast iron. The high carbon in 750 promotes the formation of graphite in the weld metal, thereby reducing shrinkage stresses and the possibility of heat affected zone cracking. 750 weld deposits are machinable. Designed specifically for on-the-job repairs of cast iron, which eliminates the necessity of dismantling equipment. While pre-heating is recommended 750 may be used without pre-heating or post-heating in many instances.