Gray Cast iron with high austenite to eutectic ratio. Part III. High strength, low hardness, high carbon equivalent gray iron with superfine graphite

The standard methods to increase the mechanical properties of gray cast iron include the use of a lower carbon equivalent (CE) and/or of alloying elements. However, these methods produce higher hardness and, in particular for the case of lower carbon equivalent, increased propensity to shrinkage defects. This paper describes a method of increasing the tensile properties of hypoeutectic gray iron of relatively high carbon equivalent through the manipulation of the chemical analysis of the iron and otherwise standard procedures. When using appropriate sulfur and titanium contents the primary austenite-to-eutectic ratio is highly augmented and superfine interdendritic graphite is produced. The tensile strength of gray iron of average 4% carbon equivalent can be increased to 300-350 MPa, without a significant increase in hardness, which remains in the range of 185-200 HB.