Influence of silicon content on the mechanical properties of as-cast and heat treated samples of nodular cast iron grade EN-1563-GJS']JS-400-18-LT

The effect of silicon content on the mechanical properties of as-cast and heat treated samples of nodular cast iron grade EN-GJS-400-18-LT, specified according to EN-1563, was studied. The presence of manganese and other pearlite forming elements and low nodule count prevented the formation of as-cast fully ferritic matrix in the samples even with silicon content over 3,0 %. Increase in silicon content, in examined range from 2,0 to 3,0 %, caused a mild reduction of hardness and tensile strength in as-east samples, yield strength stayed unchanged, while elongation values progressively increase. The effect of silicon content variation on tensile strength and hardness in heat treated samples was the quite opposite, which can be attributed to ferrite strengthening by silicon. The probability of attaining the specified values of impact toughness, tested at -20 degrees C, was increased by ferritizing annealing treatment of the samples and limiting of final silicon content in the nodular cast iron below 2,6 %.