| 摘要 |
1,209,712. Corrosion resistant steel pipes. BENTELER-WERKE A.G. 24 Sept., 1968 [29 Sept., 1967], No. 45372/68. Heading F2P. A pipe, e.g. for heating installations, comprises a flexible steel pipe 2 having an internal layer of corrosion resistant material 1, preferably a homogeneous plastics material such as polyolefine, and an external sheath 3 of expanded plastics material having a volumetric weight of less than 0À7 pond/cub. cm. The layer 2 may comprise an acid and alkaliresistant chrome-nickel steel, or copper, the sheath 3 preferably consisting of a polyolefine expanded by azodicarbonamide as the propellant. Before being shaped into a tube and longitudinally welded a sheet of steel can be roll plated on one side with a thin chrome-nickel steel sheet. A tube of copper may be telescoped into the steel tubing both tubes being drawn down to a reduced cross-section and bonded together by pressure diffusion on a mandrel and finally heated to a temperature of about 930‹ C. It is preferable to expand the plastics external sheath by means of a propellant to a volumetric weight below 0À5 pond/cub. cm., and to add to the sheath about 6-15 parts by weight of light weight heat insulating material, e.g. asbestos or powdered diatomite. |
