| 摘要 |
PROBLEM TO BE SOLVED: To provide a new rustproof steel sheet for a fuel tank using no Pb by studying various factors on the material side affecting the soldering and brazing property, and properly controlling the contact resistance value of the surface. SOLUTION: A small contact resistance value is desirable in view of a soldering and brazing property, the contact resistance value is set to 0.1-8 mΩfor increasing a resistance welding property, and the contact resistance value is preferably set to 0.1-3 mΩfor reconciling the resistance welding property and soldering and brazing property. Factors controlling the contact resistance value include surface roughness and the film thickness of the most surface in an Sn-plated steel sheet. When the surface roughness is above 2μm in RMS, the thickness of the surface film has irregularities, local heating easily occurs, and the resistance welding property becomes inferior. Some kind of film contributing to contact resistance is applied to the surface of the steel sheet, the film is an industrial chemical conversion coating or an organic resin film, and the total film quantity is set to 2 g/m2 or below on one face.
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