Improvement of Axial Compression Mechanical Properties of Laser Remelted Recycled H-Shaped Steel Short Columns

To address the dual bottlenecks of high energy consumption in traditional remanufacturing through remelting and performance degradation in direct reuse, this study proposes a short-process remanufacturing method based on laser remelting technology, establishing a circular pathway of “dismantling-remelting-certification-reuse. ” As a regenerative repair technique, laser remelting offers advantages such as superior mechanical properties of the remelted layer, elimination of surface defects, and optimization of the microstructure. Although this technology has proven effective at the material level, systematic research at the member scale remains insufficient. In this study, the mechanical and microstructural properties of the remelted layer were characterized through uniaxial tensile tests and metallographic analysis. Defect measurements and axial compression tests were conducted on laser-remelted recycled H-section steel stub columns fabricated using four different scanning strategies to evaluate the improvement in axial compressive performance and the effectiveness of the repair. A finite element model was developed using Abaqus to validate the experimental results and reveal the mechanisms underlying the improvement in mechanical performance. The results indicate that the centrally symmetric scanning strategy using a single robotic arm (with a power of 1.5 kW and a scanning speed of 1.2 m/min) increases the yield strength and ultimate bearing capacity of the members by more than 27% and 38%, respectively. Metallographic analysis shows that laser remelting transforms coarse surface grains into fine dendrites, forming a high-strength remelted layer, with the component transitioning into a “remelted layer-substrate-remelted layer” composite structure. Finite element simulations further elucidate the synergistic load-bearing mechanism of this composite structure under axial compression. This study fills the research gap regarding the performance of laser-remelted recycled steel structures at the member scale, providing a theoretical foundation for practical engineering applications.