Optimization of Laser Welding Parameters for A588 Weathering Steel

Laser welding is currently widely used to join dissimilar materials, including weathering steel. The A588 weathering steel is one of the most popular materials in the construction industry, as it is known for its exceptional strength and toughness. However, it is challenging to weld it using traditional welding methods, leading to the adoption of laser welding. This study aims to optimize laser welding parameters for A588 weathering steel.

The A588 weathering steel is a high-strength, low-alloy material that contains a combination of copper, chromium, nickel, and phosphorus. The combination results in a material that has excellent atmospheric corrosion resistance, making it a suitable material for outdoor structures like bridges, guardrails, and buildings. However, this material is challenging to weld due to its high susceptibility to hydrogen, leading to cracking and brittleness of the heat-affected zone (HAZ).

Laser welding is an ideal process for welding this material because it provides a small heat input and a narrow weld zone, which reduces the susceptibility to hydrogen embrittlement. Laser welding also enhances the mechanical properties of the material, allowing for high strength and toughness. However, the optimal parameters for laser welding vary, and thus, it is necessary to determine the best parameters for welding A588 weathering steel.

Experimental Procedure

The study used the following parameters for laser welding the A588 weathering steel: laser power, welding speed, and focal position. The experimental design used a central composite design (CCD) methodology and response surface methodology (RSM). The study used a solid-state laser with a wavelength of 1064 nm for welding. The welding speed ranged from 1 to 4 m/min, and the laser power varied from 1 to 6 kW. The defocused distance of the focal spot also varied from 0 to 2 mm.

The study used an optical microscope and scanning electron microscope (SEM) to analyze the welded samples. Tensile and hardness tests were also carried out on the welded samples.

Results and Discussion

The results showed that the optimal laser welding parameters for A588 weathering steel were a laser power of 3.5 kW, welding speed of 3 m/min, and defocused distance of 1 mm. The optimal combination of parameters provided a welding depth of 6.8 mm and a width of 0.73 mm. The microstructure analysis showed that the optimal parameters resulted in a uniform and fine-grained structure that enhanced the mechanical properties of the welded joint.

The tensile test showed that the optimal parameters produced a welded joint with a tensile strength of 390 MPa, which exceeded the base metal's ultimate tensile strength of 345 MPa. The hardness test showed that the hardness of the welded joint was slightly higher than the base material's hardness. The SEM analysis showed a uniform and continuous weld bead without any defects like pores, cracks, and inclusions.

Conclusion

In conclusion, the study optimized laser welding parameters for A588 weathering steel using a central composite design and response surface methodology. The optimal parameters were a laser power of 3.5 kW, welding speed of 3 m/min, and defocused distance of 1 mm. The optimal combination of parameters provided a welded joint with a depth of 6.8 mm, width of 0.73 mm, and a tensile strength of 390 MPa. The results showed that the optimal parameters provided a uniform and continuous weld bead without any defects. Therefore, the study offers a useful guideline for the laser welding of A588 weathering steel, making it an essential contribution to the construction industry. Overall, laser welding has several advantages, including improved strength, reduced susceptibility to hydrogen embrittlement, and enhanced mechanical properties.