COATED STEEL SHEET OR COIL

摘要

The invention relates to a coated steel sheet or coil having a base layer which is composed of steel and to whose at least one top face is applied, by hot dip coating, a zinc coating. In the case of such steel sheets or steel coils, the zinc coating ensures a high level of corrosion resistance. The thicker the coating, the greater this resistance. Thus, in the case of a conventionally alloyed zinc coating, in a spraying test performed on a bright, uncoated sample in accordance with DIN 50021, red rust occurs after just 24 hours in the case of a coat add-on of 25 g/m² , whereas with a coating add-on of 70 g/m² red rust is formed only after 120 hours. The thickness of the coating that is needed in the prior art for sufficient corrosion resistance, however, brings problems with it in connection with weldability. This is the case in particular when laser welding at high welding speeds is to be used to produce a penetration weld in the lap joint without a minimum joining gap, of the kind required in particular in the field of the construction of car bodies or in the field of household engineering. The seam produced by such welding ought to be free from through-holes, to possess substantially no craters and to have no open pores.