| 摘要 |
PROBLEM TO BE SOLVED: To reduce the contact resistance with a positive electrode mix and prevent the occurrence of leakage by forming the inner face of a side wall main section and the inner face of a caulk section into the prescribed surface roughnesses respectively. SOLUTION: This battery can is molded with a preplated steel sheet, and it has a bottomed cylindrical shape constituted of a caulk section 23 and a main section. The surface roughness Ra of the inner face of the side wall main section must be set to 0.10-1.9μm. When the roughness is smaller than the lower limit value, the reduction of the contact resistance with a positive electrode mix is insufficient. When the roughness is larger than the upper limit value, the constriction of the thickness is liable to be generated, causing pinholes. The surface roughness Ra of the inner face of the caulk section 23 is set to 1.0-0.01μm. When the surface is rough in caulk shrinkage machining, wrinkles by the compressive stress in the peripheral direction are easily generated, and the sealing property against an electrolyte becomes inferior.
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