Abstract
Influence of phosphorus and silicon on the mechanical properties of spheroidal graphite cast iron was reported. Pure magnesium (0.5% Mg) was introduced to the molten metal which had been prepared from Swedish iron, ferro-silicon and ferro-phosphorus, inoculated with 0.4% Si and poured to the keel block dry sand mould. Tensile and impact tests were carried out in the ascast condition and the as-annealed condition.
In the as cast condition, the following properties were obtained; tensile strength 55 to 75kg/mm2, elongation 0.4 to 7.4%, Charpy impact strength (without notch) 0.3 to 4.7mkg. The structure of matrix was substantially pearlitic, where a small amount of ferrite could be observed. The tensile strength gradually decreased with increasing of phosphorus content, but the elongation and Charpy impact strength decreased rapidly.
In the as annealed condition, very good ductility was obtained when both phosphorus and silicon content were low. Generally the tensile strength slightly increased with increasing of phosphorus up to 0.12%. More of this amount of phosphorus caused the phosphide structure to appear, which decreased the tensile strength gradually and impact strength rapidly.
Silicon had also the important effect on toughness of the spheroidal graphite cast iron.
It was shown that 0.15% phosphorus had no appreciable effect on the elongation and impact strength of the spheroidal graphite cast iron with 2.0% Si, but the same amount of phosphorus had embrittling effect in the iron with 3.0% silicon.
