PURPOSE: To inexpensively and easily produce the double pipe provided with corrosion resistance, high-temp. corrosion resistance, oxidation resistance, wear resistance, etc., on the outside surface of a base pipe.
CONSTITUTION: The double pipe is produced by using powder 2 of other kinds of metals on the outside surface of a cylindrical metallic blank material 1 and forming a coating layer by a hot isostatic pressurization method under the conditions satisfying 35(t/Do2-Di2)1/2-1/2)>(Fi/(Fi-Fo))(Tu-T), t: the thickness of the coating layer, Do: the outside diameter of a coating layer forming blank material, Di: the inside diameter of the coating layer forming blank material, Fi: the extrusion force required for the metallic blank material alone having the same shape as the shape of the coating layer forming blank material at the temp. and extrusion ratio at which the material is extruded, Fo: the extrusion force required for the coating layer metal alone which has the same shape as the shape of the coating layer forming blank material and is formed by HIP at the temp. and extrusion ratio at which the material is extruded, T: an extrusion temp.; Tu: the upper limit temp. at which the coating layer metal alone which has same shape as the shape of the coating layer forming blank material and is formed by HIP can be extruded without generating cracks at the extrusion ratio to extrude the coating layer metal alone, then subjecting the coating layer to hot extrusion.
NOSE KOICHI
DENPO KOZO
OGAWA HIROYUKI
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