Original Article

The impact of intercritical annealing temperature on microstructure and mechanical properties of an ultra-low carbon medium manganese heavy steel plates

¹ Technical Center of Ben Gang Group Corporation, PR China
² National and Local Joint Engineering Laboratory of Advanced Automotive Steel Development and Application Technology, PR China
³ School of Materials Science & Engineering, Shenyang Ligong University, Shenyang 110159, PR China
⁴ The State Key Laboratory of Rolling and Automation Northeastern University, Shenyang 110819, PR China
⁵ Laboratory for Excellence in Advanced Steel Research, Department of Metallurgical, Materials and Biomedical Engineering, University of Texas at El Paso, 500 W. University Avenue, El Paso 79968, TX, USA

^* e-mail: yonggangdeng@126.com

Received: 17 February 2024
Accepted: 3 July 2024

Abstract

This study examines how varying intercritical annealing temperatures influences the microstructure and mechanical properties of 30 mm thick ultra-low carbon medium manganese steel plates. The results indicate that annealing at 650 °C produced superior mechanical characteristics that include yield strength of 680 MPa, tensile strength of 871 MPa, elongation of 38.2%, and impact energy of 135 J at −60 °C. The microstructure consisted of lath-like ferrite and austenite in both film-like and blocky forms. With an increase in annealing temperature, a rise in the volume percentage of austenite and its transition from a film-like to a blocky structure were observed. The enhancement in mechanical properties can be ascribed to the formation of reverted transformation austenite during intercritical annealing. Furthermore, enhanced stability of the reverted austenite contributed to improved ductility in fracture behavior.