Abstract: A method for heat treating a metal tube or pipe is provided to perform heat treatment in such a manner that metal tubes or pipes (1) to be accommodated in a heat treatment furnace are laid down on a plurality of cross beams (22) arranged along a longitudinal direction of the metal tubes or pipes with the distance between adjacent cross beams being in a range of 200 to 2500 mm. This makes it possible to inhibit bending and scratches of the metal tubes or pipes without causing discoloration and deterioration of the manufacturing efficiency for the metal tubes or pipes. When the metal tubes or pipes (1) are laid down on the cross beams (22), spacers may be interposed between the metal tubes or pipes (1) and the cross beams (22) on which they are laid down.

Abstract: A method for heat treating a metal tube or pipe is provided to perform heat treatment in such a manner that metal tubes or pipes (1) to be accommodated in a heat treatment furnace are laid down on a plurality of cross beams (22) arranged along a longitudinal direction of the metal tubes or pipes with the distance between adjacent cross beams being in a range of 200 to 2500 mm. This makes it possible to inhibit bending and scratches of the metal tubes or pipes without causing discoloration and deterioration of the manufacturing efficiency for the metal tubes or pipes. When the metal tubes or pipes (1) are laid down on the cross beams (22), spacers may be interposed between the metal tubes or pipes (1) and the cross beams (22) on which they are laid down.

Abstract: A Ni—Cr alloy tube demonstrating an excellent corrosion resistance in a high temperature water environment can be provided, wherein the difference between uniform lattice strains of the surface layer thereof satisfies the following formulas (1) and (2). S?0.002??(1) S=D500?D?200??(2) wherein the meanings of the individual symbols in the above described formulas are as follows: S: The difference between uniform lattice strains (?) of the surface layer D500: The {111} interplanar spacing (?) at a depth of 500 nm from the material surface D?200: The average value of the {111} interplanar spacings (?) at the depth of 200 nm or less from the material surface.

Abstract: A Ni—Cr alloy tube demonstrating an excellent corrosion resistance in a high temperature water environment can be provided, wherein the difference between uniform lattice strains of the surface layer thereof satisfies the following formulas (1) and (2). S?0.

Abstract: A method of heat treatment for an efficient forming of two-layered oxide film on the inside surface of a Ni-base alloy tube. The oxide film suppresses the Ni release in a high-temperature water environment. At least two gas supplying devices are provided on the outlet side of a continuous heat treatment furnace; or one gas supplying device is provided respectively on the outlet side and the inlet side thereof. The tube is put into the furnace while supplying an atmospheric gas into the tube from the front end of the tube moving direction with one of these gas supplying devices and a gas introducing pipe, which is arranged inside the furnace, and this tube is maintained at 650 to 1200° C. for 1 to 1200 minutes. The atmospheric gas consists of hydrogen or a mixture of hydrogen and argon, whose dew point is in a range of from ?60° C. to +20° C.

Abstract: A method of heat treatment for an efficient forming of two-layered oxide film on the inside surface of a Ni-base alloy tube. The oxide film suppresses the Ni release in a high-temperature water environment.

Abstract: (1) A nickel-base alloy product having, on the surface thereof, an oxide film comprising at least two layers, namely a first layer mainly composed of Cr2O3 and having a chromium content of not less than 50% relative to the total amount of metal elements and a second layer occurring outside the first layer and mainly composed of MnCr2O4, wherein the grain size of Cr2O3 crystals in the first layer is 50 to 1,000 nm and the total oxide film thickness is 180 to 1,500 nm. (2) A method of producing the nickel-base alloy product as specified above under (1) which comprises subjecting a nickel-base alloy product to oxide film formation treatment by maintaining the same at a temperature of 650 to 1,200° C. in a hydrogen atmosphere or hydrogen-argon mixed atmosphere showing a dew point of −60° C. to +20° C. for 1 to 1,200 minutes.

Abstract: (1) A nickel-base alloy product having, on the surface thereof, an oxide film comprising at least two layers, namely a first layer mainly composed of Cr2O3 and having a chromium content of not less than 50% relative to the total amount of metal elements and a second layer occurring outside the first layer and mainly composed of MnCr2O4, wherein the grain size of Cr2O3 crystals in the first layer is 50 to 1,000 nm and the total oxide film thickness is 180 to 1,500 nm.