Prototype of Japanese sword-type steel sheet with control of interfacal microstructure in order to realizes both high strength and formability

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H03433
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Material processing/Microstructural control engineering
• Research Institution: National Institute for Materials Science
• Principal Investigator: 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, 主幹研究員 (80380145)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 鉄鋼材料 / 塑性加工 / 複合材料 / 金属組織 / 相変態 / 熱処理 / 強度 / 延性

Outline of Final Research Achievements

In order to achieve the strengthening of steel, a steel plate simulating the structure of a Japanese sword was prototyped and the relationship between its microstructure and mechanical properties was clarified. Focusing on the fact that the internal structure of a Japanese sword has a kind of composite structure of carbon steels with different strengths, the sandwich-type composite steel sheets consisting of both low carbon and high carbon steels (Japanese sword type steel sheet) were prototyped. It was found that the hardenability in high carbon steel layer deteriorates when the volume fraction of the low carbon steel layers is large. In addition, through experiments and calculation of a composite steel sheet in which irregularities were artificially added to the dissimilar material interface morphology, it was clarified that a dissimilar material interface is preferably a smooth interface in which local stress concentration is less likely to occur.

Free Research Field

材料組織学

Academic Significance and Societal Importance of the Research Achievements

構造用金属材料において成形性を有しつつ強靭化を図ることは、安全性向上や小型化を通じて、環境規制への対応や資源節約を実現する方策であり、工業分野の基本課題である。この課題に対する解決策として、高強度で成形性に優れた金属材料を得るための組織の革新的理想像として、日本刀の造り込みから着想した「日本刀型鋼板」を新たに提案する。ここでは日本刀型鋼板を、「サブミリメートルスケールの層厚さを有する軟質低炭素鋼層と硬質中（高）炭素鋼層からなるサンドイッチ型複合材料」と定義する。日本刀型鋼板を模擬した複合鋼板の試作などにより、優れた機械的性質を得るための指針を探索した。