Influencing factors on as-cast and heat treated 400-18 ductile iron grade characteristics

As-cast and heat-treated 400-18 ductile iron (DI) grade was obtained in different foundry conditions, as metallic charge, Mg-treatment alloy and inoculation. It was found that the Pearlitic Influence Factor (P x ) and Anti- nodulizing Complex Factor (K 1 ) have an important influence on property of DI, depending on the Mn and P level, the metallurgical quality of iron melt, rare earth (RE) and inoculation. It was also found that the influence of Mn is depended on the phosphorus and residual elements level in ductile iron. Less than 0.03%P and 0.2%Mn and P x 2.0) determines presence of pearlite in as-cast structure, while ferrite structure is obtained after a short annealing heat treatment. Lower level of phosphorus (P 1.2. Si has a significant influence on the mechanical properties of heat treated ductile irons: an important decreasing of elongation level and a moderate increasing of yield and tensile strength and their ratio in 150-170 HB typical hardness field. A typical final chemical composition for as-cast 400-18 ductile iron could include 3.5%-3.7%C, 2.4%-2.5%Si, max.0.18%Mn, max.0.025%P, max.0.01%S, 0.04%-0.05%Mg res. for P x <1.5 and K 1 <1.1. High purity pig iron, RE-bearing FeSiMg and powerful inoculant are also recommended.