Method for heat treating a metal tube or pipe, metal tube or pipe, and heat treatment furnace

A method for heat treating a metal tube or pipe comprising:

• heat treating a metal tube or pipe, which is accommodated in a heat treatment furnace, the metal tube or pipe being laid down on a plurality of the cross beams with spacers having a convex top surface interposed therebetween, the plurality of cross beams being arranged along a longitudinal direction of the metal tube or pipe such that a distance between adjacent ones of the cross beams is in a range of 200 to 2500 mm, the metal tube or pipe being in contact with the spacers, wherein
• the convex top surface has a radius of curvature in a range of 50 to 300 mm.

A heat treatment furnace that performs heat treatment on a metal tube or pipe, the metal tube or pipe being accommodated in the heat treatment furnace in a state where the metal tube or pipe is laid down on a plurality of cross beams, the plurality of cross beams being arranged along a longitudinal direction of the metal tube or pipe such that a distance between adjacent ones of the cross beams is in a range of 200 to 2500 mm, the metal tube or pipe being in contact with the cross beams wherein

• as the cross beams, cross beams having a convex top surface are used, the convex top surface having a radius of curvature in a range of 50 to 300 mm.

A heat treatment furnace, that performs heat treatment on a metal tube or pipe, the metal tube or pipe being accommodated in a heat treatment furnace in a state where the metal tube or pipe is laid down on a plurality of cross beams with spacers having a convex top surface interposed therebetween, the plurality of cross beams being arranged along a longitudinal direction of the metal tube or pipe such that a distance between adjacent ones of the cross beams is in a range of 200 to 2500 mm, the metal tube or pipe being in contact with the spacers, wherein

• the convex top surface has a radius of curvature in a range of 50 to 300 mm.