Ultrafinegrained Microstructure in a Medium Manganese Steel after Warm Rolling without Intercritical Annealing

Abstract

Medium manganese steels are a grade of the third generation of advanced high strength steels (AHSS) that combine ductility, high strength and toughness for crashing resistance, determining characteristics for application in the automotive industry. During processing these steels are subjected to a hot and cold rolling followed by intercritical annealing in the field of austenite and ferrite phases. On the other side, the warm rolling processing is capable to reduce costs and operating time due to a single operation. The aim of this work was to follow, along warm rolling, the microstructure evolution. This aim was realized by optical and scanning electron microscopy analysis, X-ray diffraction, Vickers microhardness and EBSD technique in an 8Mn-0.08C steel. A very refined and deformed microstructure in warm-rolled condition was obtained, with a higher volume fraction of retained austenite without hot-rolled as previous processing step, which result in high tensile strength and total elongation. The texture shows a greater intensity of the α-fiber components as a function of higher strain in this thermomechanical processing.

Casting and Constitutive Hot Flow Behavior of Medium-Mn Automotive Steel with Nb as Microalloying

“…Inside the laths, some carbide precipitates were observed ( Figure 5d); presumably, these carbides can be of type Mn 23 C 6 or cementite according to Thermo-Calc predictions (Figure 1b). Recently, the former type was observed in 0.086%C-8.05%Mn-0.138%Si-0.0215%Al-Fe (wt.%) in the as-cast condition [19] and the latter has been reported to occur in GX12CrMoVNbN9-1 (GP91) cast steel [23]. When there is carbide precipitation in martensite laths, usually as small bars or plates morphologies, the phenomenon has been reported in the literature as auto-tempered martensite [24,25].…”

“…In this sense, it is essential to use simulated diagrams that allow for the study of the thermodynamic stability of the phases and their transformations, thus selecting the optimal route for heat treatment to achieve a given set of properties. Consequently, the simulated diagrams obtained through software such as Thermo-Calc ® and JMatPro ® have been widely used for this purpose [18,19].…”

Enhancing the Mechanical Properties of Al‐Containing Medium Mn Steel Through Warm Rolling and Intercritical Annealing

“…Early studies of the application of intercritical rolling, i.e., WR at 650 °C after IA, to 0.1/0.2C‐5Mn steels showed that a further refined UFG ferrite and RA duplex microstructure and improved mechanical properties were gained . Similar results were also obtained in 0.08C‐8Mn steel subjected to WR at 630 °C without subsequent IA . A later investigation of HR 0.20C‐4.88Mn‐0.62Si‐3.11Al steel subjected to WR after IA at 750 °C revealed a UTS × TEL of ≈ 50 GPa · %, which was almost independent of WR thickness reduction, was obtained…”

“…HR or HR plus cold rolling (CR) and subsequent IA treatment are commonly applied to produce medium Mn steel sheets . More recently, the application of the WR technique to medium Mn steel has gained increasing attention mainly for the purpose of further improving its mechanical properties and/or simplifying and accelerating conventional production processes . Early studies of the application of intercritical rolling, i.e., WR at 650 °C after IA, to 0.1/0.2C‐5Mn steels showed that a further refined UFG ferrite and RA duplex microstructure and improved mechanical properties were gained .…”

Behavior of V-Ti Elements in Warm-Rolled Transformation-Induced Plasticity Steel with Medium Manganese Content

“…[7][8][9][10] As such, hot forming and warm forming techniques have recently regained popularity. 11) The hot forming has been studied in our previous study. 12) Recently, several warm forming studies focused on the dynamic recrystallization (DRX) and dynamic recovery (DRV) of ferrite and austenite during warm deformation process.…”