| 摘要 |
PROBLEM TO BE SOLVED: To simultaneously realize weight reduction and high hardness by providing a double layer structure composed of a white iron structure having a highly hard cam surface and a graphite structure having a soft inner wall of a central hole. SOLUTION: A chilled cast iron hollow camshaft for an automobile engine is formed as a double layer structure composed of a white iron structure 3 having the highly hard outer periphery of a cam part and a graphite structure 5 having a soft inner wall part of a hollow hole 4 by inclusion casting of a hollow core. The shaft end is formed so as to have a matrix softer than the graphite structure 5 and excellent in cutting performance. Thus, casting takes an annealing method of placing a heating core or a pad in an end part. Thus, the graphite structure 5 can be sufficiently exhibited by using the hollow core as a core. Graphitization of this part is promoted further by arranging the heating core in the end part, and a soft matrix further transformed into ferrite can be obtained.
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