RMD방식 GMAW를 이용한 초층용접의 용접성 평가

Abstract

Welding is root industry and a key technology for the production. Also it is widely used in aircraft, ships, cars and various industries. But the welding work is difficult, dirty, dangerous. Because the smoke, noise, strong light and heat generated during welding make workers difficult. Nevertheless, the welding work is necessary at the manufacturing process of modern industry. Continuous research and development are required. Study on welding is being advanced in the direction for making high quality of the joint. High quality is associated with weld bead. So many engineers are doing research to improve the weld quality.

Welding is largely classified as SMAW, GTAW, GMAW, Laser welding and SAW etc. Among them, the share of GTA welding is only 20% in the current industry. However, its significance is fairly high compared to other welding processes.

Recently, many welding processes are being automated. GTAW is not easy to make automation equipment system. Because current automation technology doesn't accurate than manual welding.

In recently the trend of increasing Off-Shore plant and Shale Gas industry, Use of the welded pipe is increased. At this industrial sector, the welding process applied to the Root Pass welding is a GTA welding. Advantages of GTAW are high quality beads and the excellent mechanical properties of welded joints. This doesn't require post weld treatment. However, the biggest disadvantage of the GTA welding is that it requires a skilled welder operation. This rises labor costs and has low productivity.

Proficient technicians are necessary in GTA welding during Root Pass. It increases labor costs. In this paper, Instead of the high cost and low productivity in GTA, RMD-GMA welding process of the Miller company was applied. The research was conducted to study the mechanical properties about tensile, hardness, defects of the weld bead. If there is no difference in the mechanical properties compared with the GTAW, the study was conducted to improve productivity by replacing the GTAW with the RMD-GMAW.

In this study, we compared GTAW with GMAW in the same working environment that is the same specimen (Carbon Steel SS400 3t). Welding conditions(Parameter) for carbon steel SS400 was received from Miller company. Each specimen was welded by applying the optimal conditions to weld the carbon steel SS400.

When applying Root Pass Welding, Miller company RMD-GMAW Process increases productivity by about three times higher than Root Pass Welding of GTA welding. Bead and the back bead of Miller company RMD-GMAW shows a graceful appearance significantly.

In addition, the tensile strength shows almost the same level. The beads formed back bead and the good shape.

Therefore if replace the GTAW with RMD-GMAW, production cost will be reduced by half and productivity will be improved by more than three times.