Surface treated steel sheet for battery case, battery case and battery using the case

Abstract

A surface treated steel sheet for a battery case, which has a diffusion layer of a nickel-phosphorus alloy or a nickel-cobalt-phosphorus alloy formed on the outermost layer of the inside surface of a plated steel sheet for a battery case; a battery case which is produced through forming the surface-treated steel sheet having a diffusion layer of a nickel-phosphorus alloy or a nickel-cobalt-phosphorus alloy by the deep drawing method, the DI forming or the DTR forming: and a battery using the battery case. The battery case can be used for producing a battery excellent in battery characteristics.

What is claimed is: 
     
         1 . A surface treated steel sheet for a battery case comprising:
 a steel sheet having a first surface and a second surface, said first surface to be used as the inner surface of the battery case and the second surface to be used as the outer surface of the battery case;   a first diffusion layer of a nickel-cobalt phosphorous alloy formed as an uppermost layer over said first surface of the battery case;   said first diffusion layer comprising a nickel content of from 1.0 to 8.6 g/m 2 ;   a second diffusion layer of iron-nickel between said first diffusion layer and said steel sheet;   a nickel layer formed as an upper layer over the second surface; and   an iron-nickel diffusion layer between said nickel layer and said steel sheet,   wherein the first diffusion layer contains Ni 3 P,   the cobalt content in the first diffusion layer is within a range from 5 to 30% by weight,   the phosphorus content in the first diffusion layer is within a range from 1 to 12% by weight,   a thickness of the first diffusion layer is in the range of 0.1 to 2 μm,   a thickness of the nickel layer is in the range of 0.2 to 3 μm; and   wherein the surface treated steel sheet further comprises an intermediate nickel layer between said first diffusion layer and said second diffusion layer.   
     
     
         2 . A battery case comprising the surface-treated steel sheet according to  claim 1 , wherein the battery case is obtained by a drawing forming method, drawing and ironing (DI) forming method, or drawing thin and redraw (DTR) forming method. 
     
     
         3 . A battery comprising a battery case according to  claim 2 , including a positive electroactive substance and a negative electroactive substance on the inside of the battery case.