Evaluation For Nodularization Effect Based On Quick Test Of Oxygen Content In Liquid Iron

Round graphite morphology and homogeneous matrix structure decides the mechanical property of ductile iron.Nodularization rate is widely considered to be the most important factor to evaluate the microstructure and mechanical properties.Oxygen element in iron melt has always been considered to be the most active element in the process of graphite crystallization and growth.Its content affects the final morphology of cast structure.In recent years as the oxygen concentration cell method was widly used in the steel industry,the “on-line” active oxygen content quick testing for cast iron melt also has been the hot research direction.In this paper we use self-made oxygen probe to test active oxygen content indicators: oxygen activity ?_o and oxygen potential E_o in ductile iron melt,and analyse the changing rule of oxygen content and nodularization status.Finally a set of method which uses oxygen activity ?_o and oxygen potential E_o to evaluate nodularization rate was obtained and was designed nodularization-effect evaluation system base on this method.The changing rule of oxygen activity ?_o and oxygen potential E_o in cast iron melt and ductile iron melt was studied.From the thermodynamics point of view oxygen content status was used to analyse the difference in characterizing the oxygen content changing trend.The cause of the difference was explained.Their sensibility to temperature and oxygen content change.The changing of oxygen activity ?_o oxygen potential E_o and nodularization rate with the changing amount of nodulizer and the static process of nodularized melt was studied,verified the affect that active oxygen content exerts on nodularization status,under the premise of synthetically consider oxidation effect and inoculation effect,specified low oxygen environment's importance to acquire the high-nodularization rate ductile iron(?_o<0.3 ppm,E_o<-150 m V),and specified the advantage of using oxygen activity ?_o and oxygen potential E_o to characterize the changing of oxygen content and nodularization rate in iron melt.Acquired node characteristic value of oxygen activity ?_o and oxygen potential E_o in nodularized melt with different nodularization rate,and according to the two-parameter method(?_o,E_o),given the partition of different nodularization rate,quantified the mathematical model of nodularization rate partition,on this basis,it is able to realize the forecast for nodularization rate by measuring metallurgical status parameters(E_o/mV,T'/?).The system of nodularization effect evaluation for ductile iron based on quick testing oxygen content in liquid iron was built up.It can measure temperature,oxygen activity and oxygen potential easily,quickly and accurately.According to the two-parameter mathematical model,value of nodularization rate can be predicted.Oxygen testing experiments showed that it is effective for the system to test oxygen content and forecast nodularization rate.