하이브리드(Nd:YAG+MIG) 용접을 이용한 알루미늄(Al-Mg-Si)합금의 열적 거동 및 역학적 특성에 관한 연구

Abstract

Presently the consumption and application of aluminum alloys has been increased in many industrial fields, aerospace, automobiles, shipbuilding, electronics, building constructions etc. for light in weight and high strength. Therefore welding technology of aluminum alloys has already become a most important problem in industrial settings. Aluminum alloys are light in weight materials suitable for high-speed and durability because it has a high ratio of strength to density, corrosion resistance, good toughness and metallurgical characteristics at low temperature. For example 5xxx and 6xxx series of aluminum alloys has been raised in shipbuilding due to distinguished corrosion resistance, and they are not affected by big difference of salinity or temperature. However aluminum alloys are very active materials and has high thermal conductivity and thermal expansion coefficient. So welding defects and deformation can be generated by the high hydrogen solubility between liquid-state and solid-state. Thus when welding of aluminum alloys, high heat input and current are required in a short time. According to increase in use of aluminum alloys, new welding technology has been required for improvement of productivity and quality, while making up the weak points of conventional welding method and process. In this study new joining technology, laser+arc hybrid welding, was introduced and observed the weldability and feasibility in aluminum alloys for complementing the disadvantages of conventional arc welding. The 6xxx series of aluminum alloys were butt jointed by CW 3kW Nd:YAG laser+MIG hybrid welding. Firstly characteristics of thermal distribution and residual stress distribution in weldment by hybrid welding were surveyed using numerical analysis. Secondly the optimum parameters of hybrid welding were determined based on experiments. And mechanical testing and residual stress measurement were carried out and compared with the numerical analysis. In conclusion, application possibility of laser+arc hybrid welding to aluminum alloys are confirmed.