Manufacture of Cryogenic Materials used in Automotive Industry

AbstractThe paper presents the manufacturing of a cryogenic special S.G. cast iron used in automotive industry. The material used was a Mo-Cr-Ni S.G. cast iron, which it was elaborated in an induction furnace. Nodular changes were obtained with the “In mold” method, with the help of prealloy FeSiCuMg with 10-16% Mg, added into the reaction chamber in a proportion of 1.1% of the treated cast iron. After elaboration, it was made a heat treatment and then a maintaining on a low temperature (-70°C). Cryogenic treatment is methodology of ultra-low temperature processing of materials to enhance their properties to the desired levels. Material subjected to deep cryogenic temperature develops a more uniform, redefined microstructure with greater density. Austenite, the softer molecules in the microstructure is transformed to harder martensite. The experimental tests at low temperature (-70°C), were done in a specific cryogenic installation attached to an impact strength resistance tester. This installation used carbon dioxide solid like a cooling agent and ethylic alcohol as a cryogenic liquids. It is pointed out the influence of some factors (the temperature and the maintained time at the isothermal level and low temperature - 70°C) on the phase transformation and the KCV & KCU properties of the studied cast iron