Analysis of the Effect of Current Variation and Pipe-to-Plate Joint Design on the Hardness of Fuel Oil Tank Piping in Tugboats

Abstract

The pipe to plate welded joint in the fuel oil tank line of a tug boat plays an important role in maintaining the reliability of the fuel system, so that welded joint quality, particularly its hardness, must be controlled through the selection of appropriate welding parameters. This study aims to analyze the effect of welding current variation in Shielded Metal Arc Welding (SMAW) and joint design on the hardness distribution of pipe to plate welded joints. The materials used were Seamless ASTM A106 Grade B pipe and SS400 plate, joined using E6013 filler electrode with an E7016 LB-52U root pass, at welding current variations of 60 A, 75 A, and 90 A, combined with single bevel and non bevel joint designs. Hardness testing was performed using the Vickers method at the base metal (BM), heat affected zone (HAZ), and weld metal (WM) regions. The results show that the weld metal consistently exhibited the highest hardness across all current variations and joint designs, reaching 183.86 HV for the single bevel joint and 187.03 HV for the non bevel joint, both at 90 A. The non bevel joint design produced a more stable hardness distribution than the single bevel design. It is concluded that welding current variation and joint design significantly affect the hardness distribution of pipe to plate welded joints.