| 摘要 |
The present invention provides a improvement method of an internal surface of a hole of a casting in which an internal surface of a hole formed in a casting made of nonferrous metal is processed at high speed without excessively heating the same, thereby splitting and eliminating casting nests which are peculiar to the casting, and metal structure is reformed so that fluid does not leak from the casting nests formed in the casting, and to provide a casting structure whose hole internal surface of is improved, and a processing tool of the internal surface. A tool having a cross section area greater than that of a hole formed in the casting is sent and press-fitted into the hole while rotating the tool, friction heat is generated between a surface of the tool and the internal surface of the hole and then, the tool is pulled out from the hole in a state in which the rotation of the tool is maintained, thereby reforming a metal structure of the internal surface to form a reformed layer.
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