| 摘要 |
A Ni-base heat resistant alloy excellent in weldability and strength at elevated temperatures and suited for use in manufacturing cracking furnace tubes and reformer furnace tubes to be used in ethylene plants as well as a welded joint therefor is provided. The alloy of the invention is a Ni-base heat-resistant alloy, which comprises C: not more than 0.1%, Si: not more than 2%, Mn: not more than 2%, P: not more than 0.025%, S: not more than 0.005%, N: not more than 0.04%, Cr: 10 to 30%, Al: 2.1 to less than 4.5%, and Mo: 2.5 to 15% or W: 2.5 to 9% or Mo and W: 2.5 to 15% in total, and satisfies the relation (1) given below:In the welded joint of the invention, both of the base metal and weld metal are made of the alloy having the above composition, and the ST value of the weld metal as calculated according to the following formula (2) or (3) is larger by not less than 3 than the ST value of the base metal:
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