Effects of Manganese Content on the Hot Processing Properties of Low Alloy Steels and the Microscopic Mechanisms

This study investigates hot processing properties in low alloy steels containing 0.65, 1.15, and 1.65 wt% Mn. Stress–strain curves, hot processing maps, and microstructures to clarify how Mn governs workability is analyzed. The 0.65% Mn steel shows abnormal grain growth and insufficient dynamic recrystallization (DRX) at high temperatures, while deformation at intermediate temperature and moderate strain rate yields a stable, refined microstructure. The 1.15% Mn steel shows superior hot processing properties at intermediate temperatures and medium to high strain rates. The 1.65% Mn steel displays pronounced solute drag and elevated stacking‐fault energy (SFE), which favor dominant dynamic recovery (DRV) and suppress DRX, higher strain rates are required to avoid flow‐instability regions identified in processing maps. Microstructural analysis at 1090 °C and 1.0 s −1 shows that the 1.15% Mn steel forms fine, equiaxed recrystallized grains and achieves a high fraction of high angle grain boundaries. Thereby delivering the best microstructural uniformity and processing stability. Overall, Mn modulates austenite stability, SFE, and solute drag, thereby controlling the DRX‐DRV competition and delineating the hot processing window. Accordingly, Mn‐specific hot processing schedules is proposed to concurrently optimize processing stability and mechanical properties.