Different welding cooling methods used in steel manufacturing confer different mechanical properties to the produced material. The use of the electric arc-type welding connections generates extremely high temperatures that alter the mechanical properties of the steel and also the ability of the steel to resist applied loads. Therefore, in the present study, experiments were conducted to investigate the properties of 24 specimens of standard steel plates that were cooled using different methods after the welding process. The experimental results revealed that gradual cooling through the air after the welding process exerted a negative effect on the mechanical properties of the steel material. This was evident in the values of the yield stress, ultimate stress, and modulus of elasticity, which were reduced by a factor of 11.8%, 8.4%, and 7.0%, respectively, for the specimens with a thickness of 2 mm, and by 13.8%, 12.7%, and 5.2%, respectively, for the specimens with a thickness of 5 mm. On the contrary, the process of rapid cooling using water exerted a positive influence on the mechanical properties of the steel material, which manifested as enhanced values of all mechanical properties. Moreover, the welding efficiency achieved using different cooling processes decreased with the increase in the thickness of the steel plate. It is noteworthy that the negative impact of cooling in the air on the mechanical properties of the produced steel is not considered in the current design codes.