One-step quenching and partitioning treatment of directly hot rolled low carbon steel

ABSTRACT

Making cost-effective quenching and partitioning (Q&P) steel with good mechanical performance is attractive to the automotive industry. A low carbon steel was hot rolled, directly quenched, and isothermally partitioned using salt bath treatment. Effects of partitioning temperature and time on the microstructures and properties of the steel were studied. The microstructure consisted of carbide-free bainitic ferrite, polygonal ferrite, and retained austenite. The hot rolling introduced strain energy to the austenite, promoting the formation of ferrite, and enhancing the diffusion of carbon in the subsequent partitioning process with an accompaniment of the growth of ferrite. The ferrite was inferred to not only improve the plasticity of the steel but also make the retained austenite more stable. Steel exhibited excellent mechanical properties with high strength and elongation (>23 GPa·%). This study presents a preliminary approach for economical online Q&P steel production.

KEYWORDS:

• Q&P
• partitioning
• hot rolling
• one-step
• ferrite
• carbide-free bainite
• product of strength and elongation

Acknowledgments

The authors gratefully acknowledge Jun Hu from Wuhan Branch of Baosteel Central Research Institute for his help in experiments and materials.

Data availability

The data used to support the findings of this study are available from the corresponding author upon reasonable request.

Disclosure statement

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

Additional information

Funding

This research was funded by National Key Research and Development Program of China [grant number 2021YFB3702402] and the Major Projects of Technology Innovation of Hubei Province [grant number 2017AAA113].