The Influence Of Rare Earth Elements On Microstructure And Properties Of Low Carbon Equivalent Gray Cast Iron

The application of rare earth in cast iron has a history in nearly60years. It is one of the important fields of rare earth in industrial application, With the constant improvement of the properties requirements’of gray cast iron, the rare earth puts an important role in the gray cast iron as an efficient nucleating agent and draw more and more attention, Its application and technology also has been continuously developed and improved. Now, using rare earth to make up nodular cast iron, vermicular cast iron and some special cast iron have achieved good results, especially in making up ductile iron and vermicular cast iron, the technology is more improved.Low carbon equivalent gray cast iron generally refers to the carbon equivalent which is lower than eutectic point (3.7%-3.9%) of cast iron, Low carbon equivalent gray cast iron’s strengtrh、wear resistance、heat resistance、excellent anti-vibration and casting performance is much better, and it has become more and more widely used in industrial production. But low carbon equivalent gray cast iron’s chilling tendency, hot tearing and shrinkage tendency are all serious. Also, it’s flow performance is low. At the same time, it’s brittleness is big and it has poor processing, thus it is very important to improve the performance of low carbon equivalent cast iron.This topic is that when smelting the low carbon equivalent cast iron, we add different amounts of rare earth alloys to iron liquid for outside the furnace. After pouring, we test it’s crystallization process, the casting properties, crystal structure, metallographic structure and mechanical properties. Finally analyze the results and discuss to draw the influence of rare earth elements on micro structure and properties of low carbon equivalent gray cast iron.Passing test, we can get that rare earth alloy can effectively improve the low carbon equivalent gray cast iron casting’s casting properties.When rare earth alloy’s addition amount is0.1%, low carbon equivalent gray cast iron’s casting properties is the best. Low carbon equivalent gray cast iron’s graphite morphology is gradually mainly to with E type undercooled graphite. The flake graphite is more bulky. With the increase of the addition of rare earth ferrosilicon, graphite gradually becomes small A type graphite. And then, it transforms E type, D type, vermicular and spheroidal graphite. After using rare earth alloy to inoculate, the interlamellar spacing of pearlite is reduced. When the rare earth alloy’s addition amount is0.20%and0.30%, the interlamellar spacing of pearlite is relatively small. With the increase of the addition of rare earth ferrosilicon, The number of eutectic group changes little. Eutectic boundary can be clearly seen. It’s solid-liquid interface is smooth and football-shaped bunches of eutectic group is obvious. Adding rare earth alloy can destroy the a-Fe crystal lattice and increase deformation resistance. That is helpful to increase strength and hardness. Rare earth alloy has the effect of narrowing the austenitic area. The more amount the rare earth adds, the more higher the eutectoid temperature is. This will facilitate the formation and refining of pearlite to improve grey cast iron’s mechanical properties.Experimental results show that:Rare earth can improve the low carbon equivalent gray cast iron’s metallographic organization and casting performance. At the same time, it can Kept its good mechanical properties. And then, the comprehensive mechanics performance of the low carbon equivalent gray cast iron is improved.