关键词: 桥梁耐候钢, 终轧温度, 显微组织, 力学性能

Abstract: The effect of the finish rolling temperature on the microstructure and mechanical attributes of Cu-Cr-Ni bridge weathering steel, characterized by a low yield ratio, was exhaustively explored in this study. Advanced testing methodologies including the Gleeble-3800 thermal simulation tester, tensile tester, and Vickers hardness tester were employed, in conjunction with characterization techniques such as optical microscope (OM) and electron backscattered diffraction (EBSD). This comprehensive approach aimed to elucidate the specific mechanisms governing these transformative changes. The results of the investigation unveiled pivotal transformations within the microstructure of Cu-Cr-Ni bridge weathering steel. Initially rolled at 880℃, the steel exhibited a granular bainitic microstructure. A reduction in the finish rolling temperature to 800℃ ushered in the formation of acicular ferrite, which gradually increased in prevalence. Simultaneously, the average size of the M/A islands expanded from 1.3 to 3.3 μm, accompanied by an increase in the area fraction from 21.7% to 32.3%. Notably, a marked elevation in dislocation density within the matrix was observed, primarily attributed to the considerable reduction in the degree of matrix restitution. Furthermore, these microstructural modifications were mirrored by notable enhancements in the material's mechanical properties. The hardness and yield strength of the Cu-Cr-Ni bridge weathering steel experienced a pronounced upswing with diminishing finish rolling temperatures. The yield strength, in particular, exhibited a remarkable increase from 435 to 496 MPa. Contrarily, tensile strength remained relatively stable at approximately 710 MPa. These mechanical variations were intricately linked to the prevalence of acicular ferrite within the microstructure, the presence of M/A constituents, and the heightened dislocation density. Importantly, the yield ratio exhibited an increasing trend, albeit generally maintaining a level below 0.7, indicative of a subtle improvement in plasticity. This research not only advances the understanding of materials science but also offers valuable insights for optimizing the manufacturing process of high-performance bridge steels, thereby contributing to the continued progress of the bridge structure.

Key words: bridge weathering steel, finish rolling temperature, microstructure, mechanical property