780MPa級鋼の再現HAZにおける組織と靭性に及ぼすTiおよび合金元素の影響(相変態・材料組織)

概要

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The effect of Ti on microstructure and toughness of simulated HAZ of conventional high carbon type 780 MPa class steels and low carbon bainitic steels was investigated. The effect of alloying elements on microstructure and toughness of simulated HAZ of low carbon bainitic steels was also investigated. It was found that toughness is deteriorated by Ti addition in conventional high carbon steels because of the decrease in hardenability, but in low carbon bainitic steels toughness is improved because facet of Charpy impact surface is refined without decreasing hardenability. It was also clarified that toughness of low carbon bainitic steel of which hardenability is increased by non-carbide forming alloy is superior to that increased by carbide forming alloying elements. The difference could be explained by increasing of driving force for ferrite nucleation caused by lowering transformation temperature.
2004-05-01