| 摘要 |
PURPOSE:To obtain the titled steel having increased toughness at its weld heat- affected zone by restricting the contents of C, Si, Mn, P, S and N and dispersing a specified number of Ti oxide grains having a specified diameter. CONSTITUTION:This high toughness steel for welding contains <=0.18% C, <=0.80% Si, 0.40-2.0% Mn, <=0.020% P, <=0.020% S and <=0.0050% N as essential components and grains of Ti oxide and/or a composite body consisting of Ti oxide and Ti nitride. The diameter of the grains is 0.1-3.0mum, and the number is 5X10<4>-1X10<8> per 1mm.<3> steel. To the steel may be added one or more among <=5% Ni, <=2% Cr, <=0.5% Mo, <=0.15% Nb, <=0.15% V, <=2% Cu, <=0.09% Al and <=0.003% B, and a very small amount of a rare earth element, Ca, Mg or Zr may be added furthermore. The toughness of the weld zone of the steel at low temp. is improved by said composition.
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