Processing Variants in Medium-Mn Steels

Abstract

This paper highlights some recent efforts to extend the use of medium-Mn steels for applications other than intercritically batch-annealed steels with exceptional ductility (and strengths in the range of about 1000 MPa). These steels are shown to enable a range of promising properties. In hot-stamping application concepts, elevated Mn concentration helps to stabilize austenite and to provide a range of attractive property combinations, and also reduces the processing temperatures and likely eliminates the need for press quenching. The “double soaking” concept also provides a wide range of attractive mechanical property combinations that may be applicable in cold-forming applications, and could be implemented in continuous annealing and/or continuous galvanizing processes where Zn-coating would typically represent an additional austempering step. Quenching and partitioning of steels with elevated Mn concentrations have exhibited very high strengths, with attractive tensile ductility; and medium-Mn steels have been successfully designed for quenching and partitioning using room temperature as the quench temperature, thereby effectively decoupling the quenching and partitioning steps.

Physical Metallurgy of High Manganese Steels

“…This Special Issue gathers manuscripts from internationally recognized researchers with stimulating new ideas and original results. It consists of fifteen original research papers, seven contributions focus on steels with manganese content above 12% mass [4][5][6][7][8][9][10], whereas eight deal with alloys having less manganese [11][12][13][14][15][16][17][18].…”

“…Due to the importance of elemental partitioning during annealing, intensive research has been devoted to the microstructure formation during hot deformation, cooling and annealing, especially intercritical annealing. This has also been addressed in the contributions by Speer et al [11], Mueller et al [12], Liu et al [13] and Gramlich et al [14]. Some novel processing scenarios are presented in [11], namely MMnS for hot-stamping, double-soaked MMnS as well as processing by Q&P. The authors put a focus on steels with increased strength level in order to widen the field of potential applications.…”

“…This has also been addressed in the contributions by Speer et al [11], Mueller et al [12], Liu et al [13] and Gramlich et al [14]. Some novel processing scenarios are presented in [11], namely MMnS for hot-stamping, double-soaked MMnS as well as processing by Q&P. The authors put a focus on steels with increased strength level in order to widen the field of potential applications. Mueller et al [12] and Liu et al [13] investigated the influence of pre-deformation on annealing behavior.…”

Thermodynamic analysis and isothermal bainitic transformation kinetics in lean medium-Mn steels

“…These steels are designed to compromise between cost and mechanical properties. Medium-Mn steels should have higher mechanical properties than first generation AHSS but be cheaper than second generation of AHSS (advanced high-strength steels) [1][2][3].…”

Mechanical stability of retained austenite in aluminum-containing medium-Mn steel deformed at different temperatures

“…The retained austenite in the tested steel (5% Mn) was less stable due to the lack of additional partitioning of Mn into the ɣ phase [41]. The application of intercritical annealing allows for the stabilization of the austenite with this element [42,43]. It does not take place for the hot-rolled 5Mn steel sheets cooled directly from the finishing rolling temperature [44].…”