Patent ID: 7992417
Filing Date: 2011-08-09
Classification: B21B,B21C

Abstract:
1. A method for producing an ultra thin wall metallic tube by a cold rolling method in which a cold pilger mill is applied, using a pair of rolls, which has a tapered groove die whose diameter is gradually reduced from an engaging inlet side of the roll toward a finishing outlet side thereof and a tapered mandrel bar, whose diameter is gradually expanded from an engaging inlet side toward a finishing outlet side thereof, according to outside diameters and wall thicknesses of a hollow shell and a finishing rolled tube, wherein the wall thickness is reduced to perform elongation at the same time when the outside diameter is reduced and the inside diameter is expanded while an expansion margin of the inside diameter is set larger than a reduction margin of the outside diameter and a wall thickness center diameter, which is an average diameter of the outside and inside diameter, is expanded.