Study on Thermal Deformation Behavior and Constitutive Model of 316 Stainless Steel for Lightning Rod of Ancient Buildings

To address the specific performance requirements of lightning protection materials for ancient buildings, isothermal hot compression experiments were conducted with forged 316LN austenitic stainless steel employing a Gleeble-3500 thermal-mechanical simulator. The test matrix covered a strain rate range of (0.001–1) s⁻¹, a deformation temperature interval of (1273–1423) K, and a maximum true strain of 0.7, targeting a comprehensive exploration of the material’s high-temperature flow behaviors. A flow stress constitutive model was constructed by integrating the Arrhenius equation, and its predictive performance was validated through rigorous comparison with experimental data. Key observations indicate that under constant strain rate conditions, elevated deformation temperatures lead to reduced compressive stress in the material. This phenomenon is closely linked to enhanced atomic mobility and accelerated dynamic recrystallization, which collectively induce softening effects. In contrast, at a fixed temperature, higher strain rates result in increased compressive stress, as rapid deformation intensifies work hardening to an extent that outweighs dynamic softening. The true stress-true strain curves exhibit a distinct three-stage evolution, rapid ascent, gradual growth, and stabilization with the final stable phase arising from a dynamic equilibrium between work hardening and dynamic softening mechanisms. This research delivers essential theoretical foundations and practical engineering guidance for refining the hot working processes of 316LN stainless steel specifically tailored to the fabrication of ancient building lightning protection systems.