To provide a method for reducing impurities to the limit, the impurities concentrated in a Ni-diffusion plating layer, particularly near the surface layer, and causing failures in a Ni-diffusion plated steel sheet such as high surface contact resistance or degradation in characteristics of a cell.
Not only impurities in a plating liquid but inevitable impurities in a steel sheet or elements added to develop the material quality are concentrated in the surface layer through minute defective portions or intergranular portions of a Ni-plating layer during diffusion annealing. The method for manufacturing a Ni-diffusion plated steel sheet comprises subjecting a steel sheet to electric plating in a matte watt bath using pure Ni as a counter electrode, then to diffusion annealing to obtain a Ni-diffusion plated steel sheet and to temper rolling, wherein the sheet after diffusion annealing and prior to temper rolling is treated with an acid aqueous solution to eliminate impurities concentrated in the surface layer of the Ni-diffusion plating layer of the Ni-diffusion plated steel sheet.
COPYRIGHT: (C)2008,JPO&INPIT
Tomoya Nishiyama
Kazumi Nishimura
Yutaka Ando
Kenji Imai
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Hisataka Tanaka