## Abstract

The fabrication process of railway underframe structures generally involves welding, which can generate residual stress and deformation due to localized heating. This deformation has the potential to alter the dimensions and quality of the structure; therefore, a method is required to reduce it without significantly changing the mechanical properties of the material. One method used is reforming, which is a reheating process carried out at a certain temperature to reduce deformation and residual stress. This study aims to analyze the effect of reforming temperature variations on the mechanical properties of underframe materials, particularly tensile strength and hardness. The reforming process was conducted at temperatures of 700°C, 750°C, and 800°C, with one specimen without reforming used as a comparison. Tensile testing was performed to obtain the ultimate tensile strength (UTS) and yield strength values, while hardness testing was carried out using the Rockwell C (HRC) method. The results showed that reforming at 800°C produced an average UTS value of 498.87 MPa, a yield strength of 354.53 MPa, and the lowest hardness value of 1.57 HRC. These values were close to the original mechanical properties of the material, indicating that reforming at 800°C was effective in reducing welding-induced deformation without causing significant changes in mechanical properties.