Effect of Initial Rolling Temperature on Interfacial Reaction–Diffusion, Cladding Stability, and Tensile Failure of Industrially Hot-Rolled 316L/SWRH82B Clad Wire Rods

To meet the combined requirements of high strength, intrinsic corrosion protection, and cost effectiveness for bridge cable wires, 316L/SWRH82B stainless-steel/high-carbon-steel clad wire rods were manufactured under industrial hot rolling conditions. Three initial rolling temperatures of 1000, 1024, and 1047 °C were investigated through metallographic observation, quantitative image analysis, EPMA characterization, SEM fractography, and tensile testing, with 15 specimens tested for each temperature group. The EPMA results, together with the metallographic observations, were used to evaluate carbon diffusion, interfacial elemental redistribution, and decarburization. As the initial rolling temperature increased from 1000 to 1024 and 1047 °C, the decarburized-layer thickness on the SWRH82B side increased from 7.42 ± 1.28 µm to 11.31 ± 1.74 µm and 18.15 ± 1.76 µm, respectively, whereas the carburization-affected-zone thickness on the 316L side increased from 48.36 ± 2.73 µm to 63.04 ± 3.06 µm and 68.73 ± 3.65 µm, respectively, demonstrating pronounced asymmetric interfacial reaction–diffusion. The average tensile strengths of the three groups were 1120.07, 1146.27, and 1152.28 MPa, with corresponding standard deviations of 14.83, 4.55, and 13.34 MPa and coefficients of variation of 1.32%, 0.40%, and 1.16%, respectively. Among the tested conditions, the 1024 °C group exhibited the lowest tensile-strength standard deviation and coefficient of variation, indicating the best tensile stability and mechanical consistency. Although the 1047 °C group achieved the highest average tensile strength, it also exhibited reduced cladding thickness uniformity and renewed mechanical scatter. All 45 tensile specimens were fractured on the SWRH82B side without obvious macroscopic interfacial delamination, indicating that the interface was not the preferential macroscopic fracture path under the present uniaxial tensile-loading condition. However, the intrinsic interfacial bonding strength was not directly quantified in this work. Therefore, 1024 °C is identified as the preferred initial rolling temperature for the specific billet geometry and industrial rolling conditions examined in this work, rather than a universally applicable value. The present study is limited to as-hot-rolled clad wire rods; corrosion performance, multi-pass cold drawability, and the final performance of bridge cable wires after drawing remain to be experimentally validated.