| 摘要 |
PROBLEM TO BE SOLVED: To provide, by a simple process, a heat resistant multilayered metallic tube in which the performances are improved of a heat resistant metallic tube used under the condition where the precipitation and deposition of carbon and carburization easily occur because of its contact with hydrocarbons at high temperatures such as an ethylene tube of a naphtha cracker, and which has excellent coking resistance, and thus has satisfactory carburization resistance. SOLUTION: The face kept in contact with hydrocarbon in a tube base material (1) of a heat resistant metal is provided with a overlaying layer (2) of a Cr-Ni based alloy by cladding by welding, particularly by plasma transfer welding using powder as a filler material to prepare multilayered metallic tube. As the alloy forming the overlaying welded layer, a Cr-Ni based alloy having a composition containing, by weight, >=35% Cr and satisfying a condition of Ni%>=0.5Cr% is suitable. Part of Ni can be replaced with Co. The total content of the components other than Cr and Ni is preferably suppressed to <=20%. More preferably, the total content of the components other than Cr and Ni is suppressed to >=10%, and most preferably, the total content of the components other than Cr and Ni is suppressed to <=5%. |
