Kobe Steel, Ltd.

Kabushiki Kaisha Kobe Seiko Sho

Nippon Koshuha Steel Co., Ltd.

Takeshi Nakahara

Toyofumi Hasegawa

Takehiko Kato

Sadayoshi Furusawa

Masatoshi Nishizawa

Toshihiro Minami

Described herein is high strength steels used for bolts containing as alloy elements:

High strength steel bolts

A method for warm forging a cup-shaped piece is disclosed. In warm forging a blank is heated between 400.degree. and 800.degree. C. and is inserted within a die having a cross sectional area substantially larger than that of the blank. The ends of the blank are clamped between a recess in the die and a recess in an upsetting punch and the upsetting punch compresses the blank until its sides become sufficiently bulged to almost touch, or touch, the sides of the die. The upsetting punch is then removed and a backward extruding punch is press fitted into the bulged blank and the blank is extruded to form a cup. The extrusion punch is lubricated and cooled by lubricant and coolant applicators at a position remote from the die so that the blank is not prematurely cooled by the coolant.

Warm forging method for cup-shaped pieces

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Akashi, Japan

Takeshi Nakahara