Microstructural and mechanical properties of ultra-high-strength dual-phase steel produced by ultra-fast cooling

ABSTRACT

In the present study, grain refinement of Fe–Si–Mn–Nb–B steel was achieved by high reduction hot rolling. Through the following ultra-fast cooling (UFC) and relaxation process, martensite-ferrite complexes with soft phase embedded in the hard phase were prepared. Extremely tiny ferrite grains significantly increased the toughness of the test steel, a large number of big-angle grain boundaries existing in fine martensite lath bundles effectively improved the strength and the strain hardening ability of the investigated material. The test steel with a relaxation time of 6 s shows the best comprehensive performance with a tensile strength of 1473 MPa, an elongation of 15.0%, a low yield ratio of 0.72 and a product of strength and elongation (PSE) of 22.10 GPa%.

KEYWORDS:

• Hot-rolled DP steel
• ultra-fast cooling
• microstructure
• mechanical property
• work hardening value

Acknowledgements

The research is supported by the National Natural Science Foundation of China (grant number 51771139) and Fundamental Research Funds for the State Key Laboratory of Refractories and Metallurgy (grant number 2018QN07).

Disclosure statement

No potential conflict of interest was reported by the author(s).

ORCID

Teng Wu http://orcid.org/0000-0002-1204-0128

Additional information

Funding

This work was supported by National Natural Science Foundation of China: [Grant Number 51771139]; State Key Laboratory of Refractories and Metallurgy: [Grant Number 2018QN07].