Study On The Microstructure And Properties Of High-Ductility Ductile Iron Cooling Stave And Its Experiment Of Solidified Simulation

As-cast high-ductility ductile iron cooling stave is easy to appear some problems,such as leakaged,burn-out,cracking,rupture and low service life. By uesing metallographic microscope,SEM and tensile testing machine'observe the microsructures and test the tensile strength and elongation.This paper studies the effection of microstructures and properties of high-ductility ductile iron cooling staves on silicon,thickness,cooling rate and breeding crafts,and graphite distortion.As well as it simulates the solidification processing of the high-ductility ductile iron cooling staves,studies the effection of graphite distortion on processing and time of the solidification.The experiment inoculation adopts bottom nurtured,launder nurtured and anubandha nurtured.Changing the quantity of the inoculant is found that:Adding bottom nurtured 0.9%,launder nurtured 0.5%,anubandha nurtured0.1% is the best inoculation. The studies of attachedtestcoupon of the high-ductility and heavy section ductile iron cooling stave show that Percent of spheroidization comes up to 90%,the ferrite content reaches 88～90% and non-carbide appears.Average elongation achieves 24.8%,Tensile strength is about 400MPa.In the attachedtestcoupon of high-ductility and heavy section ductile iron cooling stave,when carbon content is about 3.5%,Si is 2.3-2.9%,the body is ferrite,no carbide and pearlite appear,with the increasing of Si,spherize goes to worse and the elongation decline. When the content of silicon is 2.3%,the grade of spherize is 2,the dimension of graphite is 7. the graphite is small and round and normal.The highest elongation is 25.9%,tensile strength is 406MPa.When the thickness of high-ductility and heavy section ductile iron cooling stave is 250 or 3000mm,Compare the microstructure and property of simulation samples,it can be fund that with the increase of the thickness,the grade of spherize drop to 3 from 2,the dimension of graphite change from 7 to 6,and elongation show the phenomenon of decline,the highest elongation is 26.39% when the thickness is 250mm.Choosing the specimens between the two storey cooling channels of the ductile iron cooling stave,with the decline of cooling rate,At first,Graphite is look like chunky or worm-like,gradually small and round and normal,at last,the graphite appears at the Shape of chunky.the best grade of spherize is ahout 2-3,the worst's is 6;the dimension of graphite is 7 when it looks the best,and the worst is 4.Elongation and tensile strength rise at first,then fall,the highest tensile strength is 397MPa,the lowest is 311MPa,and elongation reaching the top is 19%,the lowest is only 4%.The research of CAE solidification processing show:molten metal fill steady and no vortex produced.With the filling processing,the temperature of liquid reduce about 40℃,which of arouding the cooling channels almost decline 70℃.With the delaying the orders and the time of solidification,graphite grow up gradually from small and round,Finally appears like blossom and chunky.At the first area of the cast,the grade of spherize is between 2 to 3,the dimension of graphite comes to 7.At the last area of the cast the grade of spherize is only 6,the dimension of graphite is 4.Liquid distribution of CAE simulation interprets the reason how to produce the graphite distortion,it also explains it is easy to appear dispersed shrinkage and shrinkage at the last solidification area with the dispersed shrinkage's criterion of Niyama.