METHOD FOR PRODUCING A COATED METAL BAND HAVING AN IMPROVED APPEARANCE

摘要

A hot-dip-coated, non-skin-passed, cold-rolled metal strip is provided. The metal strip is obtained by passing the metal strip through a bath of molten metal, wiping the coated metal strip with nozzles that spray a gas on each side of the strip and making the strip pass through a confinement zone. The metal coating of the metal strip includes a waviness Wa0.8 of less than or equal to 0.70 μm, 0.2 to 8% by weight of aluminum and magnesium in the following proportions: 0.1 to 8% by weight of magnesium for an aluminum content equal to or greater than 0.2% but less than 2% by weight or a content greater than 5% but less than or equal to 8% by weight of magnesium for an aluminum content equal to or greater than 2% but less than or equal to 8% by weight, and up to 0.3% by weight of additional elements, the balance being zinc and inevitable impurities. Metal parts are also provided.

主权项

1. A hot-dip-coated, non-skin-passed, cold-rolled metal strip obtained by a process comprising the following steps:
passing the metal strip through a bath of molten metal, comprising 0.2 to 8% by weight of aluminum and magnesium in the following proportions:
0.1 to 8% by weight of magnesium for an aluminum content equal to or greater than 0.2% but less than 4% by weight ora content greater than 5% but less than or equal to 8% by weight of magnesium for an aluminum content equal to or greater than 4% but less than or equal to 8% by weight,and comprising up to 0.3% by weight of additional elements, the balance being zinc and inevitable impurities; then wiping the coated metal strip by means of nozzles that spray a gas on each side of the strip, said gas having an oxidizing power lower than that of an atmosphere consisting of 4% oxygen by volume and 96% nitrogen by volume; and then making the strip pass through a confinement zone bounded:
at the bottom, by the wiping line and the upper external faces of said wiping nozzles,at the top, by the upper part of two confinement boxes placed on each side of the strip, just above said nozzles, and having a height of at least 10 cm in relation to the wiping line andon the sides, by the lateral parts of said confinement boxes, the atmosphere in said confinement zone having an oxidizing power lower than that of an atmosphere consisting of 4% oxygen by volume and 96% nitrogen by volume and higher than that of an atmosphere consisting of 0.15% oxygen by volume and 99.85% nitrogen by volume, the metal coating of the metal strip so obtained including:
a waviness Wa0.8 of less than or equal to 0.70 μm;0.2 to 8% by weight of aluminum and magnesium in the following proportions:
0.1 to 8% by weight of magnesium for an aluminum content equal to or greater than 0.2% but less than 2% by weight ora content greater than 5% but less than or equal to 8% by weight of magnesium for an aluminum content equal to or greater than 2% but less than or equal to 8% by weight, andup to 0.3% by weight of additional elements, the balance being zinc and inevitable impurities.