フェライト組織鋼の靭性に及ぼすCの存在状態と固溶Nの影響

  • 吉村 信幸
    日本製鉄(株)技術開発本部東日本技術研究部
  • 潮田 浩作
    金沢大学大学院自然科学研究科
  • 白幡 浩幸
    日本製鉄(株)技術開発本部鉄鋼研究所高靭性鋼材研究部
  • 星野 学
    日本製鉄(株)技術開発本部鉄鋼研究所高靭性鋼材研究部
  • 重里 元一
    日本製鉄(株)技術開発本部鉄鋼研究所高靭性鋼材研究部
  • 田中 將己
    九州大学工学研究院材料工学部門 京都大学構造材料元素戦略拠点

書誌事項

タイトル別名
  • Effects of States of Carbon and Solute Nitrogen on Toughness of Ferritic Steel
  • フェライト ソシキコウ ノ ジンセイ ニ オヨボス C ノ ソンザイ ジョウタイ ト コヨウ N ノ エイキョウ

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抄録

<p>To develop microstructure control concepts for ensuring the toughness of high-strength steel plates, basic research was conducted using ferrite single-phase steels with different amounts of C, and the effects of the states of C were investigated along with those of solute N. In this study, Fe-0.017C (mass%) alloy, wherein the state of C was changed to a solid solution, intragranular cementite, and intergranular cementite, were used for microstructural observation, Charpy testing, and fracture surface investigation. The results reveal that the toughness of the intragranular cementite steel was the best, followed by that of solute C steel and intergranular cementite steel. In intergranular cementite steel with significantly inferior toughness, the coarse intergranular cementite leads to dislocation pile-up, initial crack formation, and macroscopic brittle fracture. The brittle fracture of intragranular cementite steel was caused by the deformation twins. It is thought that the fine intragranular cementite only had a minor effect on the crack initiation and dislocation mobility. Twin was also confirmed at the initiation point of brittle fracture in the solute C steel. Hence, it was deduced that the deterioration of toughness caused by solute C resulted from the promotion of twinning, which replaced the dislocation movements. However, the deterioration of toughness caused by solute C was smaller compared with that caused by solute N, which partly caused intergranular fracture. This is attributed to the suppression of intergranular fracture by the presence of a small amount of solute C.</p>

収録刊行物

  • 鉄と鋼

    鉄と鋼 108 (2), 141-155, 2022

    一般社団法人 日本鉄鋼協会

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