To precisely make the weight of article, to save the machining process and to enhance the precision of the outside shape by cold machining a bar steel blank into a specific cross-section reduction ratio to form an intermediate blank, heating the intermediate blank so as to be in a specific percentage of elongation and constraint-pressure-forming it in a final finishing shape.
A bar steel 1 is put in a cold forming machine 2, it is worked in the largest cross-section reduction ration as 55% to 85%, and an intermediate blank 4 having large diameter parts on both ends of a small diameter part is formed. The intermediate blank 4 is put inside a heating furnace 5 and it is heated so as to show the percentage of elongation being made as 7% to 25%, next, it is formed in a pressure forming machine 6, metals are attached in a fitting hole of a piston and a crank shaft attaching hole, and the article 9 of connecting rod is produced. Therefore, because the bar steel is cold- machined in the restraint state, the precision of the article is improved, the weight of the article is stabilized, and the highly precise weight balance can be realized.
SOGA RYUJI
KIHARA TAKASHI
SUGITA HIROSHI
HONDA MOTOR CO LTD
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