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ORIGINAL PAPER

Effects of annealing temperature on microstructure and properties of tailor‑rolled blank of medium‑manganese steel Ying Zhi1 · Di‑wen Ke1 · Xiang‑hua Liu1,2 · Zhi‑xin Feng1 Received: 6 June 2019 / Revised: 9 December 2019 / Accepted: 16 December 2019 © China Iron and Steel Research Institute Group 2020

Abstract The microstructure and mechanical properties of tailor-rolled blank (TRB) of medium-manganese steel during annealing were investigated. The annealing process of austenite-reverted transformation of the experimental steel was formulated. The effects of different morphologies on properties with different annealing temperatures in different thickness zones of TRB were analyzed. In the thin zone, the morphology is blocky, and in the thick zone, the morphology is lamellar. At the same annealing temperature, the tensile strength of the thick zone is lower than that of the thin zone, and the elongation and product of strength and elongation (PSE) of the thick zone are higher than those of the thin zone. With the increase in annealing temperature, the tensile strength increases, while the yield strength, the elongation and the PSE all decrease in the same thickness zone. Because the stability of lamellar austenite is higher than that of blocky austenite, the comprehensive mechanical properties in the thick zone are good. At the annealing temperature of 640 °C, the experimental steel has the best comprehensive mechanical properties, and the maximum PSE is more than 40.0 GPa% in different thickness zones. Particularly, PSE is up to 45.6 GPa% in the thickness zone of 2.0 mm. Keywords  Tailor-rolled blank · Medium-manganese steel · Annealing temperature · Austenite-reverted transformation · Product of strength and elongation

1 Introduction With the rapid deterioration of available energy resources, low-carbon environmental protection and energy conservation have become a global problem. The trend in the steel industry is saving energy and reducing emissions by consuming fewer resources [1]. The development of variable gauge rolling (VGR) as a distinctly new technology may play a key role in this regard. This involves the production of sheets with variable thicknesses such as longitudinal profile (LP) plates and tailor-rolled blank (TRB) [2]. In recent years, variable gauge sheets produced by rolling have shown great promises due to their good quality, low cost and high production efficiency. LP steel plates have great market potential for their use in bridge, architecture [3, 4], shipbuilding * Ying Zhi [email protected] 1



State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, Liaoning, China



School of Materials Science and Engineering, Northeastern University, Shenyang 110819, Liaoning, China

2

[5–8], etc. LP plates and TRB are produced by adjusting the gap between the rolls during rolling. TRB is used to replace tailor-welded blank (TWB) [9] in automobile manufactures. TRB has the following obvious advantages compared to TWB [10–13]: (1) no welding re