METAL TUBE FOR USE IN CARBURIZING GAS ATMOSPHERE

摘要

A metal tube for use in a carburizing gas atmosphere, which comprises a Cu-rich layer having a Cu concentration of 0.1 atomic % or more and a thickness of 0.3 nm or more in the surface portion thereof, and comprises a base material having an alloy composition, in mass %, wherein Cr: 15 to 35 %, Ni: 30 to 75 %, Al: 0.001 to 10 %, and Cu: 0.01 to 10 %. The metal tube may further comprise an oxide scale layer containing Cr as a main component and having a Cr content of 50 % or more or an oxide scale layer containing Cr and Al as main components and having a total content of (Cr + Al) of 50 % or more, on the outside of the above Cu-rich layer, and may still further comprise a second oxide scale layer containing Si as a main component and having a Si content of 50 % or more, between the above oxide scale layer and the above Cu-rich layer. The above metal tube has a function of shielding the base material from a carburizing gas, and is excellent in the resistance to metal dusting, to carburizing and to coking.