Gray cast iron with high austenite-to eutectic ratio. Part II. Increasing the austenite-to eutectic ratio trough inoculation

A higher amount of primary austenite in the microstructure of gray iron typically results in higher strength, if the pearlite-to-ferrite ratio is constant. The most common method to increase the amount of austenite in the microstructure is by decreasing the carbon equivalent. However, a lower carbon equivalent produces higher hardness and increased propensity to shrinkage defects. This paper describes a method of increasing the austenite fraction through the manipulation of the chemical analysis of the iron. Iron powder, iron shots and ferrotitanium additions were explored. When using appropriate titanium additions the austenite fraction in a 4% carbon equivalent gray iron can be increased, for example, from 0.18 to 0.27. This was accompanied by the solidification of superfine interdendritic graphite. A detailed analysis of the graphite through optical and electronic microscopy is also provided.