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■■■■■■■■■■■■■■■■■■■ 川崎製鉄技報 KAWASAKI STEEL GIHO Vol.31 (1999) No.3 ■■■■■■■■■■■■■■■■■■■ |
| 拡缶性に優れた溶接缶用鋼板 Tin Mill Products with an Excellent Expansion Formability for Welded Cans 荒谷 誠(Makoto Aratani) 小幡 由紀夫(Yukio Kobata) 久々湊 英雄(Hideo Kuguminato) |
| 要旨 : 缶胴部を拡大成形する飲料缶用 3 ピース溶接缶に適した鋼板を開発した。従来の硬質鋼板では，(1) 缶胴を拡大成形すると，母材部が高さ方向に大きく収縮変形し，溶接部は変形しにくいため凸形状になり，蓋を巻締めると傷める恐れがあった。r 値の問題であり，鋼中 C 量を多くし，缶胴周方向の r 値を小さくして収縮変形量を小さくした。(2) ストレッチャーストレインが発生し，美粧性を損ねた。ひずみ時効性の問題であり，箱焼鈍過時効処理を行ない解消した。(3) 大板の幅最端部位置から板取りした場合，溶接部近傍でくびれ現象が発生した。伸びが小さいことと，板幅最端部の板厚減少の問題である。伸びは中温連続焼鈍 (750℃) で増大し，板厚は熱延鋼帯の板クラウンを小さくし，変形応力を増大して解決した。 |
| Synopsis : Kawasaki Steel has developed a steel suitable for three-piece beverage cans whose bodies are expanded after welding. The reasons why the conventional steel cannot be applied to the same use are, as follows: (1) When a welded body is expanded, it shrinks in the direction of the can height, except the less formable welded portion, which becomes in a convex shape and may hurt the body when it is curled and seamed with a can top lid. This is caused by a high r-value in the peripheral direction of the can body. (2) Stretcher strain is generated and causes poor surface appearance. This is caused by the strain aging effect. (3) When a can is made from the extreme edge portion of a steel sheet, necking may occur at the welded portion of the can. This is caused by a low elongation and a decrease in thickness at the extreme edges of the steel sheet. Kawasaki Steel has solved these problems of (1) to (3) respectively by the countermeasures, which are, as follows: (1) In order to decrease the r-value in the peripheral direction of the can body, the concentration of carbon is increased. (2) In order to reduce the strain aging effect, an over-aging treatment with a batch annealing furnace is applied. (3) In order to increase the elongation, a continuous annealing at a temperature of about 750｡C is applied. And Kawasaki Steel has decreased the crown of the hot rolled strip, the raw material of a tin mill product, in order to avoid the decrease in thickness at the extreme edges of steel sheets. |
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