| 摘要 |
PROBLEM TO BE SOLVED: To provide a heat treatment method by which an oxide film of two- layer structure capable of suppressing elution of Ni in a high-temperature water environment can be formed with certainty and high efficiency on the internal surface of an Ni-base alloy tube. SOLUTION: In this heat treatment method, at least two gas-feeding devices are provided on the delivery side of a continuous heat treatment furnace or one gas-feeding device is provided on both the delivery side and the entry side respectively. While feeding controlled atmospheric gas composed of hydrogen or a gaseous mixture of hydrogen and argon and having a dew point ranging from -60°C to +20°C into the inside of the tube to be treated before charging into the furnace, from its advancing-direction head-end side using one of the above gas-feeding devices and a gas-introducing pipe penetrating the furnace, the tube is charged into the furnace and held at 650 to 1,200°C for 1 to 1,200 min. In the above process, after the head end of the tube reaches the delivery side of the furnace, an operation where the feeding of the controlled atmospheric gas into the inside of the tube is switched to the feeding from the other gas- feeding device is repeated. COPYRIGHT: (C)2003,JPO
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