CAST IRON 'VARI - MORPH' (VM) WITH GRAPHITE OF SEVERAL FORMS - MATERIAL FOR CASTINGS OF SPECIAL DESTINATIONS

摘要

Cast iron is a material, which mechanical, physical, technological and functional properties are formed by graphite (its shape, distribution and size) and by a metallic matrix, which the most often is ferrite, pearlite or their mixture. Generally, three grades of cast iron are produced, grey cast iron (flake graphite), vermicular cast iron (compact graphite) and spheroidal cast iron (nodular graphite). It is assumed that in the casting structure of each cast iron grade occurs graphite, homogenous in respect of its shape, and the homogeneity degree is not smaller than 90 - 95%. Grey and spheroidal cast irons dominate in the world industrial practice. The technological standards do not predict producing cast irons with a mixed graphite. Cast iron with a mixed graphite forms, with controlled fractions of individual shapes, which proposed name is VM cast iron ('Vari - Morph'), can become an interesting material for castings of a special requirements. This VM cast iron is characterised by physical and mechanical properties, which can not be achieved when graphite is homogeneous in respect of its shape.