Study On Prediction Of Shrinkage Tendency And Spheroidization Of Ductile Iron Based On Thermal Analysis Technology

Ductile iron with low prices and the unique performance advantages,as well as the continuous improvement of production technology and other reasons,ductile iron production has been steadily improved in recent decades.However,in the industrial production,ductile iron due to the existence of abnormal spheroidization,degradated spheroidization,shrinkage and other casting defects,resulting in high scrap rate,which seriously affect the production of ductile iron quality.Due to the progress of technology and the development of intelligent,thermal analysis technology has been widely used in the actual production of cast iron.The extensive application of thermal analysis technology has brought new understanding and methods to the causes and solutions of casting defects.In this paper,the effects of carbon,silicon,nodularizer,first inoculation,instantaneous inoculation and pouring temperature on the characteristic value,shrinkage tendency,nodularity and graphite ball number were studied by univariate experiments.Then,the SPSS regression analysis software was used to establish the mathematical model of curve characteristic value and shrinkage tendency,nodularity and graphite ball number,so as to predict the tendency of nodular cast iron shrinkage and spheroidization.The results show that:(1)When the carbon content increases from 3.4% to 3.8%,there are hypoeutectic,eutectic,near hypereutectic and hypereutectic solidification modes.The spheroidization of eutectic ductile iron is the best,and the shrinkage tendency of the near hypereutectic ductile iron is the smallest;(2)When the silicon content increases from 2.2% to 3.0%,the solidification of iron has undergone hypereutectic and eutectic solidification modes.The shrinkage tendency and characteristic value of Tliq have a decreasing trend.However,the nodularity,the number of graphite balls and the characteristic value of TER have a increasing trend;(3)With the increase of the addition amount of nodularizer,the shrinkage tendency has a decreasing trend.When the addition amount of nodularizer increased from 1.00% to 1.45%,the number of graphite balls and the nodularity increased.The number of graphite balls and the nodularity decreased when the addition amount of nodularizer increased from 1.45% to 1.60%;(4)The first inoculation can significantly improve the number of graphite core,increase the number of graphite ball and nodularity,while reducing the shrinkage tendency;(5)With the increase of instantaneous inoculation amount,the shrinkage tendency,the number of graphite balls and the nodularity increase;(6)The mathematical models of predicting the tendency of nodular shrinkage,nodularity and graphite ball were established by linear regression,which have high accuracy.