Effect of Rare Earth and Magnesium Contents on the Solidification Process and Graphite Morphology of Compacted Graphite Cast Iron

Author of the article:HAO Bokui 1 , DENG Xiaozhou 1 , CAI Qizhou 2 , XIAO Fengzan 1 , ZHENG Weixing 1 , TIAN Yunsen 1 , CH

Author's Workplace：1. Yichang Marine Diesel Engine Co., Ltd., Yichang 443002, China; 2. State Key Laboratory of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, China

Key Words：compacted graphite cast iron; cooling curve; solidification process; eutectic recalescence; graphite morphology

Abstract： The effect of vermicular element RE and Mg content on the solidification process and morphology of vermicular
graphite was studied by thermal analysis and microstructure characterization. The results show that the eutectic point moves
to right and the primary crystallization temperature increases after vermicularization treatment by Re and Mg alloy, and
0.019%~0.023% RE and 0.006%~0.011%Mg increase the primary crystallization temperature from 1 152.7 ℃to 1 163.2~
1 166.6 ℃.There is a definite relationship between the eutectic recalescence temperature ΔT R and morphology of graphite.
With the increase of ΔT R , the vermicular rate increases. When recalescence temperature is higher than 5 ℃, the vermicular
rate is more than 50%. In crease Re/Mg ratio is beneficial to obtain high vermicular rate, and the chill tendency can be
inhibited by using high efficiency inoculants when RE/Mg ratio is increased.