Metal treatment – Stock – Ferrous
Patent
1997-10-09
2000-10-03
Yee, Deborah
Metal treatment
Stock
Ferrous
148330, 148333, 148336, 428679, 428682, C22C 3800
Patent
active
061267597
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to steel sheets for 2-piece battery cans, which are suitable for DI ("draw-and-ironing"; the same shall apply hereinunder) forming.
BACKGROUND ART
Recently, in the field of battery cans, it is desired that their body weight is reduced, that the processes for producing them are simplified, that the costs of raw materials for them and also the production costs are reduced, and that the walls of their side body parts are thinned to thereby increase their capacity for fillers, for which so-called 2-piece battery cans where the cathode terminal side and the side body part are integrated have been developed (see Japanese Patent Publication No. 7-99686), and have already been put into practical use. The process of producing such 2-piece battery cans comprises a step of blanking a steel sheet having a thickness of from 0.4 to 0.5 mm or so to give steel discs and thereafter deep-drawing each steel disc into a cylindrical part, followed by a step of ironing said cylindrical part with a plurality of ironing dies thereby to produce a side body part of the can having a prolonged length while thinning the wall of said side body part. The wall of the side body part of the can as produced through said process shall finally have a reduced thickness of not larger than 0.15 mm.
Therefore, the steel sheet for such 2-piece battery cans is required to have good formability in ironing or the like, and also to have high mechanical strength and good anti-secondary work embrittlement while it is in a side body part of the can. In addition, since the terminals and other parts of such 2-piece battery cans are easily corroded, the steel sheet for said cans is required to have good corrosion resistance, for which said steel sheet is generally coated with an Ni plate to ensure its corrosion resistance.
The following techniques have heretofore been proposed for steel sheets for 2-piece battery cans. surfaces of 2-piece battery cans during draw-and-ironing of a steel sheet to give said cans in consideration of the battery characteristics and the corrosion resistance of 2-piece battery cans, the absence of said micro-cracks being helpful in ensuring good battery characteristics of the cans (see Japanese Patent Application Laid-Open No. 5-21044). ratio of a steel sheet for 2-piece battery cans during the steps of hot-rolling and cold-rolling said steel sheet in order to attenuate the in-plane anisotropy of the resulting rolled steel sheet and to enhance the uniformity thereof in the direction of its coiling width, thereby controlling the final steel sheet to have a defined r value and a defined .DELTA.r value (see Japanese Patent Application Laid-Open No. 6-344003). continuous annealing, in which the carbon content of said steel sheet is defined to be not larger than 0.009% by weight (substantially from 0.002 to 0.003% by weight) (see Japanese Patent Application Laid-Open No. 6-346150). 2-piece battery cans to thereby prolong the life of the mold to be used for draw-and-ironing molding of said steel sheet (see Japanese Patent Application Laid-Open No. 6-346282). Ni plate layer to be formed on the surface of a steel sheet for 2-piece battery cans, thereby ensuring the corrosion resistance of said steel sheet. (see Japanese Patent Application Laid-Open No. 6-346284).
These prior art techniques are to define the steel sheet for 2-piece battery cans and the method for producing said steel sheet as disclosed in the above-mentioned Japanese Patent Publication No. 7-99686. However, none of these suggests any explicit means of defining the optimum components of constituting the steel sheet for 2-piece battery cans in order that the steel sheet may have good DI moldability, that the steel sheet may have high mechanical strength and good anti-secondary work embrittlement while being in cylindrical forms, that the steel sheet may have good Ni-platability with homogeneous diffusion of Ni into the surface of said steel sheet being coated, and that the Ni-plated steel sheet may have good corrosion resista
REFERENCES:
patent: 5648044 (1997-07-01), Hoshino et al.
patent: 5725690 (1998-03-01), Ochi et al.
Awaya Takashi
Furuya Hirohide
Hosoya Yoshihiro
Kojima Katsumi
Tanikawa Katsumi
NKK Corporation
Yee Deborah
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