Mechanism of Improved Ductility of 1,500 MPa-class Ultra-high Strength Cold-rolled Steel Sheet Produced by Rolling and Partitioning Method

• Hosoya Yoshihiro

  R&D, HQ, Tokushu Kinzoku Excel Co., Ltd.

• Matsumura Yuta

  R&D, HQ, Tokushu Kinzoku Excel Co., Ltd.

• Tomota Yo

  National Institute for Materials Science

• Onuki Yusuke

  iFRC, Ibaraki University

• Harjo Stefanus

  J-PARC Center, Japan Atomic Energy Agency

Bibliographic Information

Other Title

• Rolling and Partitioning法で製造される1,500 MPa級超高強度薄鋼板の高延性化のメカニズム
• Rolling and Partitioningホウ デ セイゾウ サレル 1,500MPaキュウ チョウコウキョウド ウスコウハン ノ コウエンセイカ ノ メカニズム

Abstract

By using a steel with standardized chemical composition and conventional manufacturing processes for flat-rolled steel strip, a 1,500 MPa class stainless steel sheet whose product of yield strength (YS) and total elongation (El) exceeds 30,000 MPa% was developed and its mass production has been established.Besides the excellent YS-El balance, the developed steel sheet has excellent performance for not only an anti-secondary work embrittlement but also high cycle fatigue endurance. Core technology of the developed method is composed of a combination of high precision cold-rolling and isothermal partitioning treatment in a batch furnace, the name of which was called Rolling and Partitioning (R&P) method. By the R&P method, the microstructure of steel is controlled to the mixture of a strain induced martensite as the matrix phase, and an optimum amount of retained austenite as the second phase which is dispersed in isolation and surrounded by the transformed martensite. In this paper, the microstructure formation during the R&P process and the deformation mechanism that would bring about the excellent strength-ductility balance are discussed based on the results obtained from the in-situ neutron diffraction measurement. The results have revealed that the typical Lüders-like stress-strain curve of R&P steel is caused by competitive plastic flow between austenite and martensite, and an effective transformation induced plasticity phenomenon.

Journal

• Tetsu-to-Hagane

  Tetsu-to-Hagane 106 (3), 154-164, 2020

  The Iron and Steel Institute of Japan

Keywords

• advanced high strength steel
• stainless steel
• TRIP
• rolling and partitioning method
• martensite transformation
• Lüders strain
• neutron diffraction
• nano indentation

Details

• CRID: 1390846609808620800
• NII Article ID: 130007803551
• NII Book ID: AN00151251
• DOI: 10.2355/tetsutohagane.tetsu-2019-083
• ISSN: 18832954
• ISSN: 00211575
• NDL BIB ID: 030282908
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I030282908
• Web Site: https://www.jstage.jst.go.jp/article/tetsutohagane/106/3/106_TETSU-2019-083/_pdf
• Text Lang: ja
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
  • KAKEN
• Abstract License Flag: Disallowed