Hydrogen embrittlement-resistant upgradation and its mechanism of ultrahigh strength steel through texture control

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K06852
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Structural/Functional materials
• Research Institution: Japan Atomic Energy Agency
• Principal Investigator: XU Pingguang 国立研究開発法人日本原子力研究開発機構, 原子力科学研究部門 原子力科学研究所 物質科学研究センター, 研究副主幹 (80554667)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 集合組織 / 鉄鋼材料 / 水素脆化 / 中性子回折

Outline of Final Research Achievements

The hydrogen-charged and non-charged high strength steel plates were investigated using the neutron diffraction experiments of tensile deformation. The formation of tensile textures during the uniform deformation were both observed for two cases, however, the formation of fiber texture in the hydrogen-charged case was found much rapider than that in the non-charged case. Hydrogen reduces the cohesive strength of iron cubic cell atoms along crystallographic planes, which results into the lower cooperative deformation capability among various oriented grains and the rapider formation of crystal defects. Accordingly, the heterogeneous deformation occurs in some grains than the others, finally leads to a reduced uniform elongation rate. Moreover, the rolling direction of steel plate shows better hydrogen embrittlement resistance than the transverse direction, so that the texture optimization is found possible to improve the directionality of hydrogen embrittlement of steel plate.

Free Research Field

集合組織、鉄鋼材料、中性子回折

Academic Significance and Societal Importance of the Research Achievements

自動車などの軽量化のために超高強度鋼が急速開発されている一方、微量な水素による危険な延性低下現象が生じるメカニズムの解明が必要である。これまで多くの水素脆化学説があったが、その統合的な解明には、バルク材料を負荷しながら水素脆化破断に至る結晶配向を含むその場組織変形挙動が不可欠だった。本研究では、水素含有有無の条件は集合組織がある高強度鋼板の単軸変形挙動とその異方向特性に影響すること、また、集合組織制御によって、水素脆化の異方向特性が一定程度に改善される可能性があることを解明した。この研究が今後の超高強度鋼板の開発に応用され、将来的には地球温暖化問題の解決にも貢献していくと期待できる。