Effect of Warm Rolling on the Evolution of Microstructure and Toughness in 100Cr6 Bearing Steel

Traditional spheroidization annealing of 100Cr6 bearing steel is time-consuming and energy-intensive. To address this, warm rolling is proposed as an efficient alternative for microstructure refinement and toughness enhancement. The influence of warm rolling at critical dual-phase (760 °C) and ferrite (700 °C, 650 °C) temperatures is investigated. At 760°C, dynamic recrystallization dominated with 90% recrystallized area, yielding equiaxed ferrite grains of 4–6 μm and normally distributed carbides averaging 0.37 μm in size with 32 vol%. Lower-temperature rolling at 650 °C intensified deformation bands to 3 μm spacing, promoting carbide precipitation to 47 vol% density at 15.7 particles μm⁻² while suppressing recrystallization (90% area with GOS >2). Nanoscale carbides of 0.094 μm pinned grain boundaries, transitioning deformation mechanisms from grain-boundary sliding to intragranular slip. Impact toughness increased by 30%–40% in ferrite-zone rolled specimens due to crack deflection by laminated fibrous grains and fine carbides. This work clarifies how distortion energy storage drives deformation-induced carbide precipitation, providing a pathway to achieve high toughness through tailored warm-rolling processes.