Other

Honda Motor Co., Ltd.

Nippon Steel Corporation

Takahiro Tanae

Hiroshi Akiyama

Koki Tanaka

Kazuhiko Honda

Kaoru Yamazaki

Yoshitaka Okitsu

Katsuyoshi Kaneko

Toshiyuki Katsumi

Yoshiyuki Takezawa

Yoshikazu Umeno

Naoki Tadakuma

Kazuo Ichiki

The present invention: provides a good-workability and high-strength cold-rolled steel sheet excellent in post-painting corrosion resistance to the extent of securing excellent resistance to salt warm water immersion which is a good-workability and high-strength cold-rolled steel sheet excellent in post-painting corrosion resistance characterized in that: said steel sheet contains, in mass, 0.16 to 0.19% C, 1.10 to 1.30% Si, 1.50 to 1.60% Mn, not more than 0.1% P and 0.015 to 0.050% Al, with the balance consisting of Fe and unavoidable impurities; the average of the amount of Si incrassating on the surface of said steel sheet is not more than 20 times the Si concentration in said steel sheet; and the area percentage of the portions where the ratio of the Si concentration on the surface of said steel sheet to the Si concentration in said steel sheet is not less than 10 is not more than 95%.

Good-workability and high-strength cold-rolled steel sheet excellent in post-painting corrosion resistance

A method for manufacturing a coiled spring having a high fatigue strength to be used for example as a suspension spring of a car using a rod of tensile strength 1910 to 2020 N/mm and diameter 8 to 17 mm. In a cold coiling step, the rod is formed into a coil. Annealing is then carried out to remove strains having arisen inside the coil during the coiling step. A hot setting step of utilizing surplus heat from the annealing step and applying a predetermined load to the coil to compress it for a predetermined time is then carried out. After that, multi-stage shot peening is carried out on the coil.

Manufacturing method of suspension spring for car

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Wako, Japan

Takahiro Tanae