Corten steel 588A is a low-carbon, high-strength, copper-enriched alloy known for its exceptional corrosion resistance, and is widely used in bridges, pressure vessels, and outdoor sculptures. In this study, the Nd:YAG welding process was used to join Corten steel. Initially, microstructural analysis, phase transformations, and changes in mechanical properties resulting from welding were investigated. The parameters of the laser welding process were subsequently optimized via statistical methods to enhance the mechanical properties. Therefore, response surface methodology (RSM) with the central composite design (CCD) technique was employed to optimize the key process parameters, including the welding speed, pulse duration, and focal depth. The optimal parameters were identified on the basis of the fracture force via tensile testing for strength evaluation, optical microscopy for microstructural and phase analysis, and SEM fractography for fracture surface examination. The results indicate that decreasing the welding speed and increasing the pulse duration increase the joint strength, with the highest tensile strength of 617.7 MPa observed in the sample with the maximum penetration depth, where martensitic formation occurs due to rapid cooling and solidification. In addition, the study analyzed the effect of heat input on hardness, revealing that weld metals with high penetration depths exhibit greater hardness (264 HV) than do base metals (168 HV) and HAZ (183 HV) which is attributed to a refined microstructure and the formation of a hard phase, likely martensite, resulting from rapid cooling.
