| 摘要 |
PROBLEM TO BE SOLVED: To improve the thermal fatigue resistance of the cylinder head by allowing it to contain respectively specified amounts of S and rare earth metals. SOLUTION: A cast iron material contains Cu, Cr and Mo and moreover contains, by weight, <=0.1% S and 0.015 to 0.3% rare earth metals. In this way, the crystallization of carbides contg. Cr and Mo is suppressed, and the entering of Cr and Mo into solid solution in a base structure is securely executed to improve the thermal fatigue resistance of the cast iron material. Moreover, by the incorporation of Cu, the crystallization of carbides is suppressed as well. Preferably, the content of Cu is controlled, by weight, to 0.3 to 1.2%, that of Cr to 0.1 to 0.6%, and that of Mo to 0.3 to 0.9%. Furthermore, when Ni is allowed to be contained instead of Cu, the formation of carbides can be suppressed similarly to the case of Cu, and, moreover, its corrosion resistance improves. The content of Ni is controlled to 0.3 to 1.2%. As the rare earth metals, preferably, one or more kinds among Ce, La and Nd are contained.
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