To make thermal conductivity higher and heat capacity smaller and to improve the mechanical characteristics at the time of high temperature by coating the outer side of a metallic pipe with a pipe of aluminum or aluminum alloy by a shrinkage fit.

The outer side of the metallic pipe essentially consisting of copper, iron or nickel is coated with the pipe made of the aluminum or aluminum alloy by the shrinkage fit. At this time, a low melting metal or alloy of a melting point below the melting point of the aluminum between the core material pipe and the aluminum is applied to either of the outer surface on the core material side or the inner surface on the aluminum side. Metals, such as zinc, indium, cadmium and tin, and alloys, such as aluminum-zinc, aluminum- germanium, aluminum-silicon and aluminumcadmium, are enumerated as the low melting metal. Electroplating, hot dip coating, wire brushing of molten metal, etc., are used as the coating application method. The coating application thickness is specified to about 0.001 to 1 mm.