| 摘要 |
PURPOSE:To obtain a high toughness steel for welding whose notch toughness at welding heat affected zone is improved, by containing Ti oxide, composite body of Ti oxide and Ti nitride whose particle diameter is specified, into a steel contg. Mn, etc. as basic component. CONSTITUTION:The welding high toughness steel contains by weight, <=0.18% C, <=0.80% Si, 0.40-2.0% Mn, <=0.020% S, <=0.0060% Al, <=0.0050% N as basic components, and one kind or more of Ti oxide, or composite body of Ti oxide and Ti nitride of 0.1-3.0mu particle diameter, 5X10<3>-1X10<7> pieces/mm.<3> particle number. If necessary, suitable quantities of Cr, Ni, Mo, V, Nb, B, Cu, etc. are contained. The adding compounds such as Ti oxide, etc. exist stably at high temp. during welding heat cycle, accelerate nucleus generation of ferrites in grain during gamma-alpha transformation and refine the ferrites. Consequently, the notch toughness at welding heat affected zone in large steel structure is improved.
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