Welding current effect of welded joints of base metal st37 on characteristics: corrosion rate and hardness

Abstract

This study aims to determine the effect of welding current on corrosion rate and hardness on welded joint, Heat Affected Zone (HAZ) and base metal of steel grade st37. Welding is the process of metal attachment by dilution through heating. Due to the heat of the metal around the weld will undergo thermal cycles that cause metallurgical changes in microstructure, which will affect corrosion rate and the mechanical properties such as hardness. Weld joints are one of the critical parts of a structure. The weld joints that get excessive friction will be worn fast and corrosion rate higher than the base metal. The steel grade st37 strips are treated with welding current variations of 75, 85, and 95 Amperes. The method used for corrosion rate testing is ASTM G31-72 standard where this test is based on weight loss test and corrosion solution used NaCl solution with 3% concentration. The results showed that the highest average corrosion rate of 0.10516 mmpy occurred in the strip welded to the current of 95 Ampere, followed by 85 Ampere at 0.06772 mmpy, and the current of 75 Ampere was 0.06152 mmpy. Testing of material hardness at current 75, 85, and 95 Amperes shows that the highest hardness value occurs in weld metal area with 75 Ampere with average hardness at 74.00 HRC. Current selection to during welding process has shown a significant effect on corrosion rate and hardness on the welded joint (weld metal).