18Ni マルエージ鋼の破壊靱性におよぼす時効組織とオーステナイト結晶粒度の影響

概要

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A study has been made of the effects of the aged structure and the prior austenite (γ) grain size on plane strain fracture toughness (K_<IC>) of I8 Ni 300 and 350 grade maraging steels. The relationship between K_<IC> and tensile properties or Charpy V notch absorbed energy (CVN) has been also investigated. K_<IC> is strongly affected by the structure aged at different temperatures. It is found that K_<IC> of the specimen with high temperature aged structure is superior to those with low temperature aged and overaged structures, and the factors which affect K_<IC> of the three different aged structures are discussed. K_<IC> is scarcely affected by the prior γ grain size. This phenomenon is in contrast to those of tensile ductility and CVN which markedly decrease with increasing the prior γ grain size. Therefore, any relationship between K_<IC> and tensile properties or CVN can not be observed. This may be due to the change of the fracture mode, with increasing the prior γ grain size, from dimple in the grain to dimple along the prior γ grain boundaries or quasi-cleavage.
社団法人日本鉄鋼協会の論文
1974-02-01