| 摘要 |
PROBLEM TO BE SOLVED: To prevent a trace of treatment, produced when removing casting fins of a bent part with an acute angle by a definning tool, from becoming a starting point of a crack caused by thermal stress. SOLUTION: An exhaust manifold 11 is produced by casting melts into a mold formed by uniting two-piece divided type casting molds. This exhaust manifold 11 is equipped with a main pipe part 12, a branch pipe part 13 branched at an acute angle from the main pipe part 12, and a bent part 14 with an acute angle, which is formed at the branch part of the branch pipe part 13 and has a designated radius of curvature. Casting fins 16 are produced on the united surface of the two casting molds of the exhaust manifold 11, and the fins 16 are removed by a deburring tool 17. Among those casting fins 16 the casting fin 16 produced at the bent part 14 with the acute angle is removed by operating the deburring tool 17 along its longitudinal 21 direction, and the trace of processing is extendedly formed in the longitudinal direction of the casting fins 16.
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