Techalloy 55 description: Techalloy 55 is used for welding of cast irons to other cast irons as well as for joining cast irons to mild steels. It is also readily used for the repair of castings. The welds are moderately hard and require carbide tipped tools for machining. A preheat and inter-pass temperature of not less than 350F (175C) is required during welding to prevent cracking.