| 摘要 |
PROBLEM TO BE SOLVED: To provide a film formation method where, while gas produced from a degreasing residual material at the inside face of a metallic tube is exhausted from the inside of the tube, an oxide film for suppressing the elution of metal ions from the surface of the tube is formed. SOLUTION: In the film formation method where an oxide film is formed on a metal tube subjected to cold working, after degreasing, using a continuous heat treatment furnace in which pressure changes into two or more stages in the furnace, an non-oxidizing gas is introduced into the continuous heat treatment furnace whose dew point is controlled to the range from -50°C to +50°C so as to form an oxide film. Desirably, the metallic tube is subjected to oil lubrication treatment, is then cold-rolled, is subjected to degreasing by alkali immersion and degreasing with warm water, and is thereafter heat-treated so as to form the oxide film. As the non-oxidizing gas, the one composed of hydrogen, or essentially composed of hydrogen, and comprising one or more kinds selected from nitrogen, helium and argon can be used. COPYRIGHT: (C)2006,JPO&NCIPI
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