Spheroidal graphite malleable cast iron is a new structural material developed in the recent years. This paper studies the influence of the residual content of rare earth and magnesium on the nodule counts, the time o...Spheroidal graphite malleable cast iron is a new structural material developed in the recent years. This paper studies the influence of the residual content of rare earth and magnesium on the nodule counts, the time of first stage graphitization and the rate of ferritization of it. Moreover, the role of sulfides of rare earth and magnesium in the process of graphitization has been analyzed. The results show that the residual content of rare earth and magnesium has a notable influence on the graphitic nodule counts and the time of the first stage graphitization of spheroidal graphite, but has unremarkable influence on the time of the second stage graphitization. There are a large number of spherical sulfides of rare earth and magnesium in as-cast structure, which will act as the nucleus of graphite in the process of first stage graphitization.展开更多
5 Heat treatment of VGCIResearch work has shown that the microstructure of VGCI can be modified by heat treatment to give improved properties; martensitic, bainitic, sorbitic and pearlitic structures can be produced b...5 Heat treatment of VGCIResearch work has shown that the microstructure of VGCI can be modified by heat treatment to give improved properties; martensitic, bainitic, sorbitic and pearlitic structures can be produced by quenching, quenching plus tempering, austempering and normalisation respectively. The surface properties of VGCI can also be improved by high frequency induction hardening, tufftriding and ion nitriding to meet special requirements.展开更多
Thermal analysis plays a key role in the online inspection of molten iron quality.Different solidification process of molten iron can be reflected by thermal analysis curves,and silicon is one of important elements af...Thermal analysis plays a key role in the online inspection of molten iron quality.Different solidification process of molten iron can be reflected by thermal analysis curves,and silicon is one of important elements affecting the solidification of molten iron.In this study,FeSi75 was added in one chamber of the dual-chamber sample cup,and the influences of FeSi75 additive on the characteristic values of thermal analysis curves and vermiculating rate were investigated.The results show that with the increase of FeSi75,the start temperature of austenite formation TALfirstly decreases and then increases,but the start temperature of eutectic growth TSEF,the lowest eutectic temperature TEU,temperature at maximum eutectic reaction rate TEM,and highest eutectic temperature TERkeep always an increase.The temperature at final solidification point TEShas little change.The FeSi75 additive has different influences on the vermiculating rate of molten iron with different vermiculation,and the vermiculating rate increases for lower vermiculation molten iron while decreases for higher one.According to the thermal analysis curves obtained by a dual-chamber sample cup with 0.30wt.%FeSi75 additive in one chamber,the vermiculating rate of molten iron can be evaluated by comparing the characteristic values of these curves.The time differenceΔtERcorresponding to the highest eutectic temperature TERhas a closer relationship with the vermiculating rate,and a parabolic regression curve between the time differenceΔtERand vermiculating rateηhas been obtained within the range of 65%to 95%,which is suitable for the qualified melt.展开更多
文摘Spheroidal graphite malleable cast iron is a new structural material developed in the recent years. This paper studies the influence of the residual content of rare earth and magnesium on the nodule counts, the time of first stage graphitization and the rate of ferritization of it. Moreover, the role of sulfides of rare earth and magnesium in the process of graphitization has been analyzed. The results show that the residual content of rare earth and magnesium has a notable influence on the graphitic nodule counts and the time of the first stage graphitization of spheroidal graphite, but has unremarkable influence on the time of the second stage graphitization. There are a large number of spherical sulfides of rare earth and magnesium in as-cast structure, which will act as the nucleus of graphite in the process of first stage graphitization.
文摘5 Heat treatment of VGCIResearch work has shown that the microstructure of VGCI can be modified by heat treatment to give improved properties; martensitic, bainitic, sorbitic and pearlitic structures can be produced by quenching, quenching plus tempering, austempering and normalisation respectively. The surface properties of VGCI can also be improved by high frequency induction hardening, tufftriding and ion nitriding to meet special requirements.
基金the financial support of the State Key Laboratory of Engine Reliability(skler-202105)。
文摘Thermal analysis plays a key role in the online inspection of molten iron quality.Different solidification process of molten iron can be reflected by thermal analysis curves,and silicon is one of important elements affecting the solidification of molten iron.In this study,FeSi75 was added in one chamber of the dual-chamber sample cup,and the influences of FeSi75 additive on the characteristic values of thermal analysis curves and vermiculating rate were investigated.The results show that with the increase of FeSi75,the start temperature of austenite formation TALfirstly decreases and then increases,but the start temperature of eutectic growth TSEF,the lowest eutectic temperature TEU,temperature at maximum eutectic reaction rate TEM,and highest eutectic temperature TERkeep always an increase.The temperature at final solidification point TEShas little change.The FeSi75 additive has different influences on the vermiculating rate of molten iron with different vermiculation,and the vermiculating rate increases for lower vermiculation molten iron while decreases for higher one.According to the thermal analysis curves obtained by a dual-chamber sample cup with 0.30wt.%FeSi75 additive in one chamber,the vermiculating rate of molten iron can be evaluated by comparing the characteristic values of these curves.The time differenceΔtERcorresponding to the highest eutectic temperature TERhas a closer relationship with the vermiculating rate,and a parabolic regression curve between the time differenceΔtERand vermiculating rateηhas been obtained within the range of 65%to 95%,which is suitable for the qualified melt.
