Evaluation Of The Metallurgical Quality Of Ductile Iron Based On Solidification Process

Ductile iron has been recognized for its excellent performance,low price and huge application potential,and has been widely used.However,due to defects such as shrinkage shrinkage,poor spheroidization and spheroidization,each year A large amount of waste is produced,and the occurrence of these defects is inseparable from the quality of the molten iron.According to statistics,due to the unqualified quality of molten iron,the scrap rate accounts for 60% of the total scrap rate.Therefore,it is particularly important to study how to effectively evaluate the quality of molten iron online and propose measures to improve the quality of molten iron.To this end,this thesis firstly combined the thermal analysis technology and liquid quenching technology to analyze the solidification process of ductile iron with different carbon equivalents.Then the thermal analysis technique was used to predict the magnesium content in ductile iron and the ductile iron decaying iron.The mathematical model of quality evaluation has made a rapid evaluation of the quality of molten iron.Finally,relying on the advantages of rapid analysis of the quality of molten iron by thermal analysis technology,the "two-stage method" spheroidization process was invented,effectively improving the spheroidization.The quality of the molten iron enables intelligent control of the production of ductile iron.research shows:(1)The hypoeutectic,eutectic and hypereutectic irons have higher spheroidization rate at the initial stage of solidification,but as the solidification progresses,the spheroidization rate decreases rapidly,and the spheroidization rate of the hypoeutectic iron is significantly lower than the total.For crystallization and hypereutectic iron,the spheroidization rate of eutectic iron is slightly higher than that of hypereutectic iron.(2)The temperature curve collected by the thermocouple in the thermal analysis sample cup only indicates the change of the temperature at the position of the thermocouple,and does not fully represent the tissue change at the point.In fact,the thermal analysis curve reflects the whole sample during the solidification process.The combined thermal effect of the precipitation and heat dissipation of the organization.(3)Hypereutectic iron will precipitate a large amount of graphite in the early stage of solidification,but the precipitation of per-eutectic iron and hypoeutectic iron graphite is less in the late solidification stage,which is not conducive to eliminating micro-retraction;eutectic iron still remains in the late stage of solidification.A large amount of graphite will be precipitated,which helps to eliminate the shrinkage defects of the casting.(4)The SPSS software was used to es Tablelish a mathematical model for predicting the magnesium content in molten iron,and a model for predicting the spheroidization rate and graphite sphere number of ductile iron decaying molten iron.The above model has high accuracy and can meet the requirements of prediction accuracy,can evaluate the quality of molten iron.(5)The two-stage spheroidization process can better purify the molten iron and provide more crystal core.The intelligent on-line measurement and control system of the ductile iron can accurately control the Mg content and eutecticity of the spheroidized iron solution,effectively improving the ball.The quality of the molten iron and the automation,intelligence and standardization of the spheroidizing process.