DOUBLE-LAYER BEND PIPE AND ITS MANUFACTURE

摘要

PROBLEM TO BE SOLVED: To provide a double-layer bend pipe which has a useful high wear resistance as a material for piping for transporting solids, and also to provide its manufacture. SOLUTION: This double-layer bend pipe material is such that it is a centrifugal cast-iron double-layer pipe with the inner layer of 27Cr cast iron and the outer layer of carbon steel, and that this double-layer straight pipe, as a pipe stock, is formed into a desired shape of a bend pipe by high frequency bending. During the bending process, in order to prevent a crack in the inner layer (27Cr cast iron) or buckling deformation of the pipe diameter, the machining temperature is set at 1,000-1,050 deg.C, with its rising rate to the machining temperature set at 50-250 deg.C/sec, and with its lowering rate for cooling after the machining set at 50 deg.C/sec or below. The machining speed is suitable in the range of 0.3-0.8 mm/sec.