METHOD FOR HEAT TREATING Ni BASE ALLOY PIPE

摘要

A heat treatment method capable of growing an oxide film of two-layer structure for suppressing elution of Ni in high-temperature-water environment surely on the inner surface of an Ni base alloy pipe with high efficiency. At least two gas supply units are provided on the delivery side of a continuous heat treatment furnace or one gas supply unit is provided, respectively, on the delivery side and the supply side thereof. While supplying an atmospheric gas of hydrogen or the mixture of hydrogen and argon from one gas supply unit through a gas introduction pipe penetrating the inside of the furnace into a pipe being processed within a range from the forward end side in the advancing direction to a point where the dew point is in the range of -60°C to +20°, the pipe is inserted into the furnace and held at 650-1200°C for 1-1200 min. After the forward end of the pipe reaches the delivery side of the furnace, the operation of switching atmospheric gas supply into the pipe to a supply from another gas supply unit is repeated.