The Experiment Research On As-Cast High Toughness Ductile Iron Cooling Wall For Blast Furnace

The influence of process factors on the elongation of as-cast high toughness ductile iron was given in the paper, such as inoculation the C, Si contents, and so on . The experiment results show that the elongation on the single casting test sample can be over 20% by adopting many times inoculation process when the optimum composition for ductile iron was : 3.00-3.80%C;2.5-2.9%Si; <0.2%Mn; <0.03%S; <0.06%P.A study on fracture character and fracture mechanism of the tensile sample of QT400-18 as-cast high toughness graphite ductile iron was given in the paper. The experiment results showed as the following: when the elongation of tensile sample was over 20% ,the micro-character of the tensile sample was toughness rapture ,its fracture mechanism was given, at first graphite was divorced from the ferrite matrix, then sufficient plastic distortion occurred in the ferrite matrix ,finally the greater and deeper toughness nest with teared surface layer left behind in the fracture of test sample; while when the elongation of tensile sample was between 15% and 16%, due to many abnormality ductile and white impurity , some tiny cracks were found at their tine corner, these cracks spread rapidly through the crystal if they suffered the outside force; at the same time it was rather difficult that the plastic distortion took place in the matrix thanks to the ferrite content decreasing and the pearlite content raising , at last the flat toughness nest left behind in the fracture of test sample.The practical production problem and the defect of casting on as-cast high toughness ductile iron cooling wall casting for blast furnace are analyzed. The improved process measure is also given.