THE EFFECT OF VARIATION OF ELECTRIC CURRENT ON MICRO STRUCTURE AND HARDNESS IN SS400 STEEL WELDING PROCESS USING THE SMAW METHOD

Abstract

The objective of research was to find out the effect of current on microstructure and hardness value in Alloy Steel SS400 before (raw material) and after welding using Shielded Metal Arc Welding (SMAW).

This research uses experiment methods. Technique of analyzing data used was a descriptive comparative research. The instruments used for testing microstructure and hardness were Olympus Metallurgical Microscope and Vickers Hardness Tester.

Base on the result of research, it could be concluded that the result of microstructure testing showed the improved  ferrite structure after welding. In raw material, ferrite structure seemed to looks evenly, but the result of welding using SMAW welding method with current of I20 A, 130 A, and 140A showed that ferrite structure reduced in each specimen, so that  perlite structure was very dominant. The hardness value of hardness result showed the different hardness level. The specimen with current of 140 A had higher hardness level of 231,055 VHN than the specimen with current of 120 A (219.222 VHN) and 130 A (223,333 VHN). The result of hardness testing on raw material was 182,333 VHN. This research showed that the welding using varying current changed microstructure and affected the hardness value of Alloy Steel SS400.