Solution Strengthened Ferritic Ductile Cast Iron Properties, Production and Application

Abstract

The ductile cast iron standard in Europe also considers new ductile cast iron grades with a unique combination of tensile strength with high elongation (e.g. Rm 72520 psi with A₅14%) achieved by the solution strengthening of the ferritic matrix by silicon with contents between 3% and 4.3%. The new grades tolerate a higher amount of pearlite and carbide stabilizing elements without the generation of embrittling pearlite or carbides in the microstructure. The presence of Cr, Mn, and V do not influence the elongation significantly. An advantage of the new cast irons is the cost efficient machining due to lower tool wear. The tool life with the machining of the fully ferritic grades GJS-500-14 and GJS-600-10 is about 50–60% longer in comparison to the ferritic-pearlitic grades. The investigated grades show very good cyclic mechanical properties but lower dynamic properties. The pre-condition to achieve optimized properties by well-shaped graphite nodules, achievable with special inoculation techniques, adjusted to the high silicon content and the solidification rate, otherwise threaten graphite degenerations. There is no increased danger of dross generation or of a worsening flowability (investigated with special test equipment). Also the supposed inclination to the generation of porosities with the higher Si content was not confirmed.