| 摘要 |
PROBLEM TO BE SOLVED: To provide a H shape steel for low temperature excellent in toughness at -40°C with just air cooling without adding Nb which inhibits productivity and with suppressing addition of expensive alloy elements and a manufacturing method therefor.SOLUTION: There is provided a H shape steel for low temperature containing, C:0.06 to 0.12%, Mn:0.80 to 2.00%, V:0.04 to 0.09%, Ti:0.005 to 0.025%, Cu:0.01 to 0.60%, Ni:0.01 to 0.50%, N:0.0020 to 0.0120% and having V/N of 7.0 to 22.0, CE of 0.42 or less, sheet thickness of flange of 12 to 40 mm, area percentage of ferrite at 1/4 position from an outside of sheet thickness of flange and 1/6 position from the outside of flange width of 75% or more and ferrite particle diameter of 14 μm or less. However CE=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15. There is provided a manufacturing method by hot rolling with cumulative draft at a surface temperature of flange of 900°C or less of 10% or more and air cooling.SELECTED DRAWING: Figure 1 |
