COLD DRAWING METHOD FOR PIPE, COLD-DRAWN PIPE, AND METHOD FOR PRODUCING HIGH STRENGTH OIL WELL PIPE

摘要

PROBLEM TO BE SOLVED: To provide a cold drawing method for a pipe, wherein the consumption unit of a tool and the productivity in drawing are improved, and the production cost is drastically reduced.;SOLUTION: This invention relates to the cold drawing method for a pipe where a pipe stock made of a high deformation resistance material comprising, by mass, 20 to 35% Cr and 3 to 40% Ni is drawn using a plug 2 and a die 3. When the pipe stock 1 is drawn at a working degree that the reduction of area G0 in the body part is controlled to 5 to 30%, the thickness of the pipe end part on the rear end side of the pipe stock 1 to be drawn is set so that the reduction of area G0 in the body part and the reduction of area G1 in the pipe end part on the rear end side satisfy the relation represented by inequality (3): G1/G0≤0.85, and also, the pipe stock has a cross-sectional shape in which thickness on the inner face side of the pipe is reduced in such a manner that, in a length of 20 to 1,500 mm from the pipe end part on the rear end side, it is gradually reduced from the tip side toward the rear end side.;COPYRIGHT: (C)2011,JPO&INPIT