| 摘要 |
PURPOSE:To improve resistance to sea-water pitting of a formed part mentioned below, by carrying out annealing so that an oxide film of a specific thickness is obtained at the time of annealing a cupro-nickel formed part. CONSTITUTION:At the time of annealing the above formed part in an annealing furnace such as roller-hearth furnace, etc., partial pressure of oxygen, temp., and time in the furnace are regulated to carry out annealing so that oxide-film thickness is 2,000-20,000Angstrom . In this way, pitting in sea water caused to formed part such as cupro-nickel heat-exchanger tube, etc., using sea water as cooling water, can be prevented.
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