| 摘要 |
PROBLEM TO BE SOLVED: To provide a tube having a high melting point, high oxidation resistance or the like as a heat exchanging tube for a high-temperature gas-cooled reactor and having an improved durability that can undergo a specific heat treating atmospheres, such as a vacuum atmosphere, a carburized atmosphere or the like. SOLUTION: The heat exchanging tube consists of a base material layer and a covering layer which is deposited at least on one surface of the base material layer for shutting it out from the heat treating atmosphere. The tube is manufactured as a hot isostatic and isotropic pressure press compact, a hot isostatic extrusion compact or the like. The base material layer consists of Cr base metal (preferably Cr or a Cr alloy having 60 wt.% or more of Cr), and the covering layer contacting the heat treating atmosphere consists of metal having atmospheric resistance. The kind of material for the covering layer is selected according to the atmosphere of an applied heat treatment furnace, for instance, metal (Ni, Ti or the like) having steam pressure lower than Cr and metal (Co, Ni or the like having higher standard free energy for forming carbide compared with Cr) having carburization resistance.
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