| 摘要 |
PROBLEM TO BE SOLVED: To provide a technology for improving the toughness of 9% Ni steel used in tanks for storage of liquefied natural gas, and the like. SOLUTION: The 9% Ni steel with high toughness is characterized by including, by weight, C: 0.02-0.10%, Si: 0.1-0.5%, Mn: 0.2-1.0%, P<=0.01%, S: 0.0005-0.003%, Ni: 7.5-10.0%, Al: 0.01-0.08%, N: 0.002-0.006%, and Ca: 0.0005-0.0050%, and besides by being possible to include Mo: 0.05-0.5% and/or Cr: 0.05-0.5% and the balance iron with inevitable impurities, and also by that 40×103 particles in terms of total particles of CaO, calcium aluminate, and CaS with a mean particle size of 0.5μm or less exist dispersedly per square mm or more of the steel.
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