Patent ID: 7037390

Claim:
A method of heat treatment for a Ni-base alloy tube, in which the tube is maintained at a temperature of 650 to 1200° C. for 1 to 1200 minutes in a continuous heat treatment furnace, characterized in that: at least two gas supplying devices for supplying an atmospheric gas consisting of hydrogen or a mixed gas of hydrogen and argon, whose dew point is in a range from −60° C. to +20° C., are provided on the outlet side of the continuous heat treatment furnace, so that they can move in the tube moving direction; prior to putting the tube into the continuous heat treatment furnace, the atmospheric gas is supplied into the tube from the front end of the tube moving direction by use of one of the gas supplying devices and a gas introducing pipe, which is arranged inside of the continuous heat treatment furnace; the tube is put into the continuous heat treatment furnace while being supplied with the atmospheric gas; after the front end of the tube reaches the outlet side of the continuous heat treatment furnace, the supply of the atmospheric gas from the one gas supplying device is switched to the supply from the other gas supplying device.