APPARATUS FOR TREATING SURFACE OF HOT DIP COATED STEEL STRIP

PURPOSE:To form a fine spangle pattern having a desired half-bright appearance by spraying solid grains on the surface of a steel strip immediately after galvanizing and providing the front and rear of its spraying port with fluid sucking ports and its outside with fluid jetting pork as well. CONSTITUTION:A steel strip 1 discharged from a galvanizing bath is passed between a pair of casings. Solid fine grains conveyed by air are sprayed on the surface of the steel strip from a spraying port 3. The above solid fine grains enter a galvanizing layer on the surface of the steel strip to produce many crystalline nucleus and to form a spangle pattern. On the other hand, the surplus solid fine grains pass together with air through passages 15 from sucking ports 10 provided before and after the above spraying port 3 and are circulated. In a surface treating apparatus for the above hot dip coated steel strip, the places toward the outsides of the above both sucking openings 10 are provide with gas jetting ports 12, by which the air is jetted in the direction of the surface of the steel strip. In this way, the outflow of the solid grains to the outside of a system is prevented to facilitate the control of the amt. of the air to be required and the amt. of the solid fine grains.