AC 펄스 MIG 용접-브레이징을 이용한 알루미늄 합금과 용융아연도금강의 용접성에 관한 연구

Abstract

ABSTRACT

A Study on Weldability of Aluminum Alloy and Hot Dip Galvanized Steel by AC Pulse MIG Brazing

Choi Sol Advisor : Prof. Bang, Hee-Seon, Ph.D. Department of Welding and Joining Science Engineering, Graduate School of Chosun University

Recently, greenhouse gas emissions in the transport sector in the global industrial sector are 25%, and automobile fuel efficiency regulations are being tightened to restrain greenhouse gas emissions through strengthening environmental regulations. With the development of automobile products and the development of production technology, many technologies are being developed for improvement of fuel efficiency and reduction in weight for reducing CO2 emission gas.

The focus of the development of light-weighting technology for the existing body has been research and development as a substitute concept of aluminum and super high tensile steel. Therefore, it is not a single material development for securing productivity and stability and maximization of light weight, but the need for application of various metal materials, increase in moldability and material price due to acceleration of multi-materialization, and research and development for solving the problem of dissimilar material bonding .

The aluminum alloy material has a specific gravity of 1/3 as compared with steel, and has the advantages of moldability and corrosion resistance, and the utilization thereof is increasing. In addition, the application of the material of the hot-dip galvanized steel sheet to improve the corrosion resistance of the steel is increasingly applied to automobiles. However, it is difficult to expect good welding results due to the formation of intermetallic compound (IMC) which is formed at the interface between dissimilar materials using fusion welding between ferrous and non-ferrous materials.

In this study, the weld-brazing characteristics of Al 6061-T6 and hot-dip galvanized steel lap joint welding were analyzed according to welding current and EN Ratio using AC pulse MIG welding.

The wire used in the AC pulse MIG welding was Alcotec ER 4047 wire with a diameter of 1.2 mm. The material Al 6061-T6 (thickness 2 mm) and hot-dip galvanized steel sheet (thickness 2 mm) used in this study were stacked with Al 6061-T6 and the lower plate was overlapped with GI steel 20 mm and AC pulse MIG welding. the process variables, the welding currents were changed to 50A, 60A, and 70A, and the EN ratios were 0%, 10%, and 20%. Neck thickness, Leg length. Joint interface length was measured. SEM-EDS analysis was also conducted to measure the amount of Al-Fe-SI intermetallic compound at the interface between Al 6061-T6 and the hot-dip galvanized steel sheet. As a result, as the EN ratio increased, the amount of metal deposition increased, and the neck thickness, joint interface length and leg length tended to increase. As the current increased, the root porosity increased due to the increase of heat input. At welding current 60A and EN ratio 20%, the thickness of intermetallic compound was the thinest at 2.41 ㎛. As the EN ratio increases, the melting amount of the filler increases, but the intermetallic compound growth is inhibited because the heat input at the brazing interface of GI Steel is reduced. The intermetallic compound formed a mixed layer of Fe - Al - Si system. The optimum condition was the maximum tensile - shear load of 7.9kN when the welding current was 60A and En ratio was 20%.