Patent ID: 7367518

Claim:
A descaling nozzle for removing scale from a steel plate surface by discharging water from a nozzle, wherein the nozzle has a nozzle orifice comprising: a discharge orifice opening at a concave surface or concave area of a front end, wherein the discharge orifice opening has a minor diameter D 2 ; a tapered segment extending towards the upstream side from said discharge orifice with a taper angle θ of 30 to 80°; and a large-diameter segment continuing with said tapered segment, said large-diameter segment having an inner diameter D 1 ; and the ratio (D 1 /D 2 ) of the inner diameter D 1 of the large-diameter segment relative to the minor diameter D 2 of said discharge orifice is not less than 3, wherein the discharge flow from the nozzle spreads in a single direction (width direction) within a plane perpendicular to the central axis of the nozzle, and the nozzle has an erosion thickness angle of 1.5 to 3° in the direction (thickness direction) that is perpendicular to the width direction, when said erosion thickness angle is determined for an aluminum of JIS-5050 under the conditions of a letting pressure of a spray of 15 MPa, a spray distance of 150 mm and an aluminum erosion time of 900 seconds.