고속 GTAW 공정변수가 Tube butt joint에 미치는 영향에 관한 연구

Abstract

Although GTAW has many advantages to get the excellent welding quality in most materials and is in generally used in the power plant industry for making the main pressure parts of equipment, there is a main problem of comparatively low productivity for low speed welding condition. The power plant industries are manufacturing the main pressure item using the small tubes is intended to supply the high speed GTAW process conditions by testing and evaluating the welding quality of non-destructive method and mechanical properties when welding base and peak current, welding speed rate, wire feeding speed for weld parameters are changed.

In this study, effect of welding parameters on the mechanical properties and microstructure of weldment and heat effect zone compare to base material (SA209MGr.T1a) has been investigated The study on experiment of weld parameters for high speed GTAW was proceed on an external diameter 57mm, thickness 7.7mm and Argon gas 100%. The welding parameters were changed to base current 130 and 140, welding peak current 160 and 170, welding speed rate 90, 100, 110, 120, 130 and 140 cm/min, respectively. As the current and welding speed rate increased, the cooling rate is increased, that means the microstructure at weldments and heat affected zone become better from 54 ㎛ to 13 ㎛ . These refined grains enhanced the significantly achieved mechanical properties such as tensile strength, yield strength and hardness. Consequently tensile strength, yield strength and hardness values of coupons is increased to 23%, 93%, 90% compare to parent material.