Effect of Cr Content on Hot Deformation Behavior and Microstructure Evolution of Cu–Cr–Ni Bridge Weathering Steel

The hot compression tests (T = 850–1100 °C, $\dot{\epsilon }$ = 0.1–10 s⁻¹) of Cu–Cr–Ni bridge weathering steel with different Cr content (0.46% (#1), 0.64% (#2)) were performed on Gleeble-3800-D thermomechanical simulator. The effects of Cr content on hot deformation and microstructure evolution are systematically investigated by the Arrhenius constitutive equation, processing map, electron backscatter diffraction technology, and transmission electron microscope. In the results, it is demonstrated that the increase of Cr content from 0.46% to 0.64% enhances the solution strengthening and inhibits the dynamic recrystallization of the experimental steels during hot compression, resulting in the increase of flow stress. The Arrhenius constitutive equation with strain compensation is constructed. The increase of Cr content results in an augmentation of hot deformation activation energy, rising from Q_#1 = 358.47 kJ mol⁻¹ to Q_#2 = 396.79 kJ mol⁻¹, causing the increase of deformation resistance of Cu–Cr–Ni bridge weathering steel in hot compression. The optimal hot processing window of #1 and #2 experimental steels is as follows: $\dot{\epsilon }$ = 0.1–0.2 s⁻¹, T = 1050–1100 °C, $\dot{\epsilon }$ = 0.1–0.15 s⁻¹, and T = 1050–1100 °C, the increase of Cr content leads to the narrowing of the hot processing window of the experimental steels.