Hitachi Industrial Products, Ltd.

Youhei Tanno

Tomohiro Naruse

Taiji Hashimoto

Takeshi Kazama

Ryuhei Tsukahara

A bolt fastening structure has an upper flange and a lower flange of a casing to which inner pressure is applied, the upper flange and the lower flange defining an abutting interface therebetween; a bolt hole formed through the abutting interface; and a counterbored portion formed asymmetric about a bolt hole center. The abutting interface includes a first region extending from a bolt hole inner side edge to an upper and lower flanges inner edge and being a region where the upper flange and the lower flange are in surface-to-surface contact with each other; and a partial contact region extending from a bolt hole outer side edge to an upper and lower flanges outer edge and being a region where the upper flange and the lower flange are partially in surface-to-surface contact with each other. In the partial contact region, the upper flange and the lower flange are in surface-to-surface contact with each other in a second region, and the first region is larger than the second region.

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Tokyo, Japan

Youhei Tanno