| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel material for tank excellent in stress corrosion crack resistance and low temperature toughness and a manufacturing method therefor.SOLUTION: There is provided a steel material for tank containing, by mass%, C:0.03 to 0.10%, Si:0.05 to 0.5%, Mn:0.9 to 2.0%, P:0.02% or less, S:0.01% or less, Nb:0.005 to 0.05%, Ti:0.005 to 0.025%, sol.Al:0.09% or less, N:0.001 to 0.010%, a structure of the steel material for tank has a ferrite with area percentage of 50 to 80% and hard structure 20 in a position of thickness t/4 from a surface of the steel material for tank, the hard structure consists of bainite, or bainite and martensite, average circle-equivalent diameter of ferrite is 5.5 to 15 μm and area percentage of a band structure having aspect ratio defined by a length in a rolling direction/a length in a draft direction of the steel material in whole hard structure is 50% or less.SELECTED DRAWING: Figure 2 |
