Cast Iron Nodulizing Agent

The effect on the casting is very large. Because of the low temperature of molten iron, high content of sulfur and other impurities in Cupola, it is necessary to use high grade nodularizing agents such as FESIMG Lore7, FeSiMg 8re7 and FESIMG 8re5 For Electric Furnace or "duplex" hot metal melting ductile iron, the nodularizing agent with low content of rare earth and low content of magnesium is commonly used, if the thickness and weight of Spheroidizer 4 and 2 containing Mg1-6 and Re4-8 are different due to different solidification and cooling conditions, the selection of spheroidizer can not be the same. For thin-walled small parts, rapid solidification, large undercooling, suitable for spheroidal graphite growth, but also very easy to appear carbides, increase the tendency of white mouth, when the residual magnesium more than 0.07% , more easy to produce carbides, so it is appropriate to choose low rare earth, low magnesium spheroidizing agent; For Heavy Section Ductile Iron Parts with wall thickness over 100mm, spheroidizing decay exists due to the low solidification rate at the center, it is easy to choose high grade nodulizer or increase the addition amount of nodulizer which is 0.01-0.02% higher than the residual magnesium content of common ductile iron. But the high residual rare earth can also cause the phenomenon of exploding graphite and anti-white mouth, so there are some studies to add a small amount of anti-nodulizing elements such as 0.005% antimony, or bismuth, tin to neutralize the excessive rare earth elements. There is also the choice of yttrium-based heavy rare earth nodulizer, which is more resistant to decay than cerium-based nodulizer, the main factors affecting the pearlite content in nodular iron are the solidification structure, the cooling rate through EUTECTOID zone, the content of carbon and silicon, the kind and content of alloy elements, etc. . There are few graphite balls and big size in solidification structure, which is not good for carbon diffusion, and it is good for increasing pearlite and decreasing ferrite, and high carbon content in austenite and cooling rate of casting have the tendency to increase pearlite. The pearlite can be stabilized by using nodulizer containing cu, sb or ni or adding cu, SB, Ni and sn to the molten iron. The content of these elements must be controlled for ferritic ductile iron. In addition, because rare earth elements increase the SUPERCOOLING TENDENCY OF MOLTEN IRON, the low content of Re in nodularizing agent should not be more than 5% in producing ferritic castings.