This specification covers castings made of silicon-molybdenum ferritic iron, commonly known as SiMo, with spheroidal graphite (SG), compacted graphite (CG), and medium-nodularity graphite (MG) microstructure, respectively, and intended for high temperature service in automotive and allied industries.
(1) Among ASTM standards of iron castings, there are two standards (A518 and A861) specifying very high-Si content of approximately 14% for corrosion-resistance. But the rest of iron casting standards specify 3.0% Si. Advantage of Si is evident in solution strengthening and heat resisting for ferritic iron castings. ASTM specifications are lacking for high-Si iron castings for use at elevated-temperatures in which Si content ranges from 3.5 to 5.0%, for instance. (2) ASTM standards are available for spheroidal graphite (SG) iron with min. 90% graphite nodularity (A395), and for compacted graphite (CG) iron with max. 20% nodularity (A842). The medium-nodularity graphite (MG) iron has the graphite nodularity between CG and SG. However, no standard specification for MG iron has been created yet. In the previous draft, MG stood for mixed graphite. (3) This draft was prepared mainly according to all the feedback received from the February 2014 ballot. (4) There are companies producing MG SiMo, as listed at the end of this draft for the rationale of including MG iron in this work item.
KeywordsHigh-Silicon Ferritic Iron; Silicon-molybdenum (SiMo) Iron; Spheroidal Graphite (SG); Medium-nodularity Graphite (MG); Compacted Graphite (CG); High Temperature Applications.
The title and scope are in draft form and are under development within this ASTM Committee.Back to Top