Influence of processing variables on the mechanical behavior of spheroidal graphite cast iron

The mechanical properties achievable from spheroidal iron castings are adequate for a very wide range of applications. Apart from mechanical properties, a number of other characteristics such as density, thermal expansion, thermal conductivity, specific heat, electrical conductivity, magnetic properties, and acoustic properties are also of considerable importance. Efforts are being made to improve all these properties. In the present investigation, five melts of SGI castings (M1 to M5) were prepared by standard foundry procedure and practices. The mechanical behavior of spheroidal graphite iron (SGI) castings was studied as a function of processing variables. It is found that the mechanical properties (viz. Tensile strength, Yield strength, Elongation, Impact resistance, etc) for a given chemical composition are highly dependent on processing variables (i.e. pouring temperature, preconditioning of base iron, inoculation practice, and molding materials). SGI castings are produced and tested as per ASTM 395 specifications. From the results, it is found that with varying processing conditions, the mechanical properties have been improved to a great extent; that is, the UTS (Ultimate Tensile Strength), YS (Yield Strength), EL(Elongation), and impact strength (at −20°C). The UTS has improved to 475·41 MPa; YS is also enhanced to 316·94 MPa; elongation has increased to 18%, but there is reduction in impact strength.