Quality Evaluation Of Base Iron Melt And Its Effect On Microstructure And Properties Of Grey Cast Iron

Grey cast iron is widely used in automobiles,engineering machinery and other fields because of its excellent properties such as thermal conductivity,friction reduction,shock absorption and low notch sensitivity,what's more,it has enough strength.Through years of practical experience,the properties of castings,such as mechanical properties,casting properties,machining properties,and casting defects such as subcutaneous pores and shrinkage cavities are related to the quality of the base iron melt.The quality evaluation of the base iron melt usually has three indicators: the temperature of the molten iron,the composition and the purity of the molten iron.In addition,the another metallurgical quality parameters are commonly used,such as maturity and relative strength,hardness and relative hardness;quality coefficient to measure the metallurgical quality when product grey cast iron.But these indicators need to measure the strength and hardness of grey cast iron.In this paper,the effects of carbon equivalent of grey iron in liquid iron,the holding time of grey iron in liquid iron furnace and the proportion of pig iron in charge on the curve of thermal analysis of grey iron in liquid iron,the precipitation of primary austenite,the number of eutectic cell and the proportion of A type graphite were studied.The mathematical model of the eigenvalue and the amount of primary austenite precipitation,the number of eutectic cell and the proportion of A type graphite in the base iron melt of grey cast iron.The precipitation of primary austenite in the base iron melt of grey cast iron,the number of eutectic cell and the proportion of A type graphite are used as indicators to achieve the objective of predicting the quality of molten iron metallurgy online;the primary crystallization process of grey cast iron was studied;the high temperature holding time of grey cast iron were studied for the microstructure and properties of grey cast iron.The results show:(1)The increase of carbon equivalent will reduce the precipitation of primary austenite in the solidification of grey cast iron,the increase of the number of eutectic cell,and the chilling tendency of molten iron;the prolongation of the holding time of grey cast iron in the furnace,the precipitation of primary austenite increases,the number of eutectic cell decreases,and the chilling tendency of molten iron increases;the increase of pig iron content in grey cast iron charge precipitates the primary austenite during solidification of grey cast iron,the amount of influence is not large,the number of eutectic cell decreases,and the chilling tendency of molten iron increases.(2)The characteristic value TSEF of grey iron thermal analysis curve is not the temperature at which eutectic nucleation begins in the traditional sense,but the comprehensive result of internal heat balance of the sample.(3)There are certain mathematical models for the characteristic value of thermal analysis curve and the precipitation of primary austenite,the number of eutectic cell and the proportion of A type graphite after the solidification of the grey iron in the cast iron.By the actual test of the mathematical model,the mathematical model of the regression predicts the results within the required error range.(4)The quality of molten iron of grey cast iron can be evaluated online by thermal analysis in casting production,which is of guiding significance to the production of grey cast iron.(5)When the high temperature holding time is too long,the chilling tendency of the grey cast iron tends to increase,and the inoculation effect of the grey cast iron becomes worse.Under the same treatment process,the mechanical properties of the grey cast iron obtained after the high temperature standing time of the molten iron is Poor.