Ni-CONTAINING STEEL PLATE

摘要

An object of the present invention is to provide an Ni-containing steel plate which is low in cost and has excellent low-temperature toughness. In view of the object, the Ni-containing steel plate of the present invention has a chemical composition containing by mass% C: 0.01 % to 0.15 %, Si: 0.02 % to 0.20 %, Mn: 0.45 % to 2.00 %, P: 0.020 % or less, S: 0.005 % or less, Al: 0.005 % to 0.100 %, Ni: 5.0 % to 8.0 %, and the balance being Fe and incidental impurities, and has a microstructure containing less than 1.7 % by volume fraction of retained austenite when cooled to liquid nitrogen temperature, and having an average grain size of crystal grains surrounded by high-angle grain boundaries with an orientation difference of 15° or more of 5 µm or less by equivalent circle diameter.