2017 Fiscal Year Final Research Report

Creation of Stronger, Tougher Steel by Microstructure Control and Development of Fracture Control Technology

Research Project

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Project/Area Number	26249107
Research Category	Grant-in-Aid for Scientific Research (A)
Allocation Type	Single-year Grants
Section	一般
Research Field	Structural/Functional materials
Research Institution	National Institute for Materials Science
Principal Investigator	Inoue Tadanobu 国立研究開発法人物質・材料研究機構, 構造材料研究拠点設計・創造分野塑性加工プロセスグループ, 分野長 (90354274)
Co-Investigator(Renkei-kenkyūsha)	KIMURA YUUJI 国立研究開発法人物質・材料研究機構, 構造材料研究拠点設計・創造分野塑性加工プロセスグループ, 主席研究員 (80253483) Qiu Hai 国立研究開発法人物質・材料研究機構, 構造材料研究拠点設計・創造分野塑性加工プロセスグループ, 主幹研究員 (50391214) NAKAZATO KOJI 国立研究開発法人物質・材料研究機構, 技術開発・共用部門材料加工グループ, 主任エンジニア (10469778)
Research Collaborator	UEJI RINTARO 国立研究開発法人物質・材料研究機構, 構造材料研究拠点設計・創造分野塑性加工プロセスグループ, 主幹研究員 (80380145)
Project Period (FY)	2014-04-01 – 2018-03-31
Keywords	構造・機能材料 / 機械材料・材料力学 / 材料強靭化 / 破壊制御 / 微細組織制御 / き裂伝播挙動 / 低合金鋼 / 結晶粒微細化
Outline of Final Research Achievements	Structural metallic materials are usually used for key components with the highest requirements for reliability and safety. However, toughness decreases with increasing strength. In the present study, first, 800 MPa and 1800 MPa class steels with an ultrafine elongated grain structure were fabricated by plastic deformation process. After that, a three-point bonding test was conducted in a temperature range from 200℃ to -196℃, and stress near the initial notch were quantitatively analyzed through numerical simulation. The relationship between microstructure (grain shape, grain size, texture, existence of second particle) and fracture mechanism (micro-crack initiation and propagation) was studied in details. As a result, the strength-toughness balance of the developed steel was remarkably improved compared with conventionally structural materials. For stronger and tougher steel, it is important to not only refine crystal grains, but also control their shape and orientation.
Free Research Field	工学