LASER CUTTING NOZZLE, CUTTING HEAD INCLUDING SAID NOZZLE AND LASER CUTTING METHOD USING THESE NOZZLE AND HEAD

PURPOSE: To stabilize gas flow and to enable high performance cutting in a reasonable gas consumption by specifying shapes of at least two subsequent coaxial sections. CONSTITUTION: A cylindrical nozzle 1 includes at least two subsequent coaxial sections, an inner diameter of a first section 4 is decreased from an inlet diameter more toward an outlet diameter, an inner envelop is tangent at its outlet to a cylinder having a diameter (d). Also, a second section 5 is cylindrical having a diameter D and a length (1), a D/1 is 1.1-1.3, a D/d is 0.35-1. A shape of the inner envelop is formed with two contacting arcs of a circle as one being projecting and the other being recessed, its inner envelop is tangent at a downstream part of the first section 4. Thus, the first section inner envelop does not have a clearcut edge part, a stable and undisturbed gas flow is obtained. Further, cutting quality and cutting speed are improved.