| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of manufacturing an internally grooved tube which suppresses the fluctuation in the height of formed fins during diameter reduction working when the internally grooved tube is manufactured by roll forming in a winter or cold season and to provide an internal lubrication oil used in the manufacturing method. SOLUTION: The fins 9 are formed on the inside surface of a tube stock 1 by injecting the internal lubricating oil 8 to the upstream side of a plug 2 in the tube stock 1, subjecting the tube stock 1 to diameter reduction working by the plug 2 and a die 3 and pressing the tube stock 1 toward a grooving plug 5 by rolling balls 6. The tube stock 1 is thereafter further subjected to diameter reduction by a finishing die 7, by which the internally grooved tube 10 of≥0.20 mm in the height of the fins 9,≤20°in vertex angle and≤0.05 mm in the radius of curvature of the front end is manufactured. The lubricating oil of 100 to 7,000 cSt in dynamic viscosity at 5°C containing 0.1 to 15 mass% fatty acid ester or 8C alcohol is used for the internal lubricating oil 8. COPYRIGHT: (C)2003,JPO
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