| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel having excellent toughness in a weld heat affected zone.SOLUTION: A steel having excellent toughness in the weld heat affected zone contains, by mass%, C:0.02 to 0.25%, Si:0.0001 to 0.4%, Mn:0.5 to 2.0%, P:0.03% or less, S:0.001 to 0.050%, O:0.001 to 0.005%, N:0.006% or less, insol.Al:0.0001 to 0.005%, sol.Al:0.0001 to 0.0005%, insol.Mg:0.0001 to 0.005%, sol.Mg:0.0001 to 0.0005% and the balance containing Fe and impurities and has 1×10/mmor more of a compound inclusion containing MnS and an oxide including Mg, Mn and Al with a grain diameter of less than 0.6 μm. One or more kinds selected from Cu, Ni, Cr, Mo, V, B, Ca, REM, Nb, Ti and Sn may be also included. |
