Intercritical Rolling Induced Ultrafine Lamellar Structure and Enhanced Mechanical Properties of Medium-Mn Steel

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

“…similar microstructure was exhibited by Zhao et al 9) on a 7.9Mn annealed steel at 600°C for 30 min after warm rolling at 630°C. Another suchlike result was obtained by Zhan et al 10) studying the intercritical rolling effects (650°C for 6 h) on the microstructure of a 5Mn-0.10C steel. Figure 4 shows the XRD patterns of the steel in different conditions.…”

“…13,[16][17][18][19][20] Furthermore, a higher density of dislocations in the austenite warm rolled retains the carbon atoms at this stage, since this element segregates to those imperfections. [7][8][9][10] At higher temperatures, the austenite has a lower chemical stability due to the lower concentration of carbon, therefore, in further cooling, the austenite is right away turned into ferrite and/or martensite, depending on the cooling rate; making it difficult to keep the austenite in the microstructure. Figure 5 is a plot of the phase volume fractions in 0.08C%-7.8%Mn steel as a function of temperature, predicated by Thermo-Calc TM .…”

“…3,5,[6][7][8][9] Nevertheless, the warm rolling has obtained bigger interest in reducing operating costs and time. 6,[9][10][11][12] Some papers report the warm rolling of medium manganese steels. [7][8][9][10] In all of them, the application of the intercritical annealing before or after the mechanical conformation is considered to obtain an adequate fraction of stabilized austenite to optimize the steel mechanical performance by the TRIP effect.…”

“…6,[9][10][11][12] Some papers report the warm rolling of medium manganese steels. [7][8][9][10] In all of them, the application of the intercritical annealing before or after the mechanical conformation is considered to obtain an adequate fraction of stabilized austenite to optimize the steel mechanical performance by the TRIP effect. In contrast, the present work proposes the use of warm rolling, without the hot rolling and intercritical annealing steps.…”

“…In this work, the effects using the knowledge of previous works on warm rolling 11,12) and the results recently published in literature, [7][8][9][10] the authors decided to apply this approach in order to produce ultrafine grains microstructure in a medium manganese low carbon steel (8Mn-0.08C). The main difference is that the warm working was applied directly as casting and homogenized samples without hot rolling and long intercritical annealing.…”