A36 and A53 steels are low carbon steel with relatively similar carbon percentage, respectively 0,25-0,30% and 0,25-0,29%. Both steels are often used within the marine industry. The objective of this research is to figure out the effect of the variation of the groove angle and the heat input to the process of welding two different steel plates towards a metallography, tensile, and bending test with E71T electrode, as well as figuring out the groove angle and heat input to weld 18 mm thick steel plates. The variation of the groove angle used are 55°, 60°, and 70° with heat input variation of 140 and 180 A. Results of this experimental study shows that specimen with groove angle 70° and heat input 180 A with the largest sum of HAZ length, which is 8,4 mm, as well as the largest perlite phase, which are respectively, 67% within A36 base metal, 65% on A36 HAZ, 62% on weld metal,63% on A53 HAZ, and 66% on A53 base metal. The largest open defect value in bending tests is 1.87 mm owned by specimens with groove angle of 55° and heat input of 140 A.