WELDABILITY OF HIGH-TOUGHNESS IRON - 12-PERCENT NICKEL ALLOYS WITH REACTIVE METAL ADDITIONS OF TITANIUM. ALUMINUM OR NIOBIUM

摘要

Three exceptionally high-toughness Fe-12Ni alloys designed for cryogenic service were welded by using the gas-tungsten arc (GTA) welding process. Evaluation of their weldability included equivalent-energy fracture toughness KIcd tests, transverse-weld tensile tests at -196° and 25° C, and weld crack sensitivity tests. The Fe-12Ni-0.25Ti alloy proved extremely weldable for cryogenic applications, having weld and heat-affected zone (HAZ) properties comparable to those of the wrought base alloy. The Fe-12Ni-0.5A1 alloy had good weld properties only after the weld joint was heat treated. The Fe-12Ni-0.25Nb alloy was not considered weldable for cryogenic use because of its poor weld-joint properties at -196° C and its susceptibility to hot cracking.