ABSTRACTFor an economical purpose, an austenitic spheroidal graphite cast iron grade, containinq nickel-manganese, has been developed to replace Ni-Resist cast iron, type D2M, for cryogenic applications.Several tests were carried out to produce semi-industrial. heats of 200 kg so as to cast samples with a thickness ranging between 25 and 75 mm, and a variable nickel and manganese content. The resulting grades were compared each other and with Ni-Resist cast irons, before and after heat treatment, for their metallographic structure, their hardness, their mechanical tensile properties at room temperature and their impact values at temperatures down to - 150° C.The results show that it is possible to produce cast iron grades with 7 to 10 % manganese and 9 to 11 % nickel contents, featuring, at quenched state, better mechanical tensile properties at room temperature than Ni- Resist D2M with a 22–25 % Ni content, for roughly equivalent impact values at low temperatures. For as-cast material, the properties obtained vary with material thickness, and ductility is steeply decreasing for thicknesses under 30 mm.Weldability of Ni/Mn cast iron can be compared to Ni-Resist D2M weldability; machinability however seems more difficult, especially when boring quenched material.Generally speaking, the overall properties of these new grades and their lower cost-price if compared to Ni-Resist cast iron, should lead to promising outlets for low temperature uses and/or applications requiring high-level mechanical properties.
Structure Distribution in Precise Cast Iron Moulded on Meltable Model