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| Thermal Fatigue Behavior and Cracking Characteristics of High Si-Mo Nodular Cast Iron for Exhaust Manifolds |
| YANG Yun-long1,2,CAO Zhan-yi1,LIAN Zhen-song1,YU Hai-xia2 |
1. Key Laboratory of Automobile Materials of Ministry of Education of Department of Education, Department of Materials Science and Engineering, Jilin University, Changchun 130025, Jilin, China
2. Jilin Vocational College of Industry and Technology, Jilin 132013, Jilin, China |
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Abstract The thermal fatigue cracking behavior of high Si-Mo nodular cast iron (NCI) is investigated by means of optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectroscope (EDS), in order to find a new material used in exhaust manifolds in First Automotive Works (FAW). Nodular cast irons with silicon content about 4. 7%, in combination with up to 1. 1% molybdenum, were produced by Jilin University and FAW. The repeated heating/cooling test was performed under cyclic heating at various maximum heating temperatures (Tmax) ranging from 800 to 900 ��. Experimental results indicate that the thermal fatigue cracking resistance of high Si-Mo NCI decreases with increasing the maximum heating temperature. The periods for crack initiation are 24-36, 40-50 and 70-90 times associated with heating temperature of 900, 850 and 800 ��, respectively, when the holding time is about 10 min at Tmax. When thermal fatigue cracking occurs, the cracking always initiates at the bigger surface of specimen. The major positions of cracks propagation are generally at the eutectic oxide boundary region and the region of the graphite disappearance. At the same time, the oxidation may accelerate crack initiation and propagation. On the other hand, micro-crack number varied from large to little because of shielding effect. As exhaust manifolds, the reasonable working temperature of high Si-Mo NCI is no more than 840 �� by test and analysis.
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Received: 28 October 2011
Published: 18 June 2013
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| Fund:the Science and Technology Supporting Project of Jilin Province of china |
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Corresponding Authors:
yun-long YANG
E-mail: yyl1976@126.com
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| [1] |
YANG Yun-long,,YU Hai-xia,CAO Zhan-yi. Microstructures and Growth Resistances of Ductile Cast Irons for Exhaust Manifold[J]. Chinese Journal of Iron and Steel, 2014, 26(11): 51-54. |
| [2] |
ZHOU Jian,MA Dang-shen,KANG Ai-jun,XIAO Rui-yong,LIU Zhen-tian,CHEN Zai-zhi. Change of Microstructure and Mechanical Property in the Failure Process of H13 Mandrel[J]. Chinese Journal of Iron and Steel, 2013, 48(2): 69-74. |
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2013, Vol. 20 
