Development of a new mixed (ferritic-ausferritic) ductile iron for automotive suspension parts

Weight reduction is of great significance in the automotive industry, having direct consequences in materials used in car production and their development. In this context Teksid France and Inasmet have worked to improve practical knowledge on new ferrous casting alloys, particularly ADI. This material has been validated for suspension parts, but impact test results have caused some concern: energy values obtained were higher than those for ferritic grades, but ductility, measured as deflection, was lower. To improve this property, a material with a mixed proeutectoid ferrite plus ausferrite structure has been developed. Mechanical characterization shows tensile and proof stress, together with hardness, similar to pearlitic grades, and ductility at the same level as ferritic grades. This new type of ductile iron could be used for applications where ADI is restricted owing to excessive hardness. Validation in a suspension part for the automotive industry is foreseen in the near future.