알루미늄 합금과 티타늄 합금의 AC 펄스 MIG 브레이징 시 EN 극성비 변화가 용접성에 미치는 영향

Abstract

Recently, to achieve global carbon neutrality, reducing greenhouse gas emissions has become a crucial objective. Accordingly, the automotive industry is focusing on improving fuel efficiency in line with environmental regulations. Reducing the weight of vehicles is recognized as a strategy to simultaneously achieve both improved fuel efficiency and reduced emissions. Aluminum alloy and titanium alloy, differing significantly in melting points by over 1000 degrees Celsius and sensitive to high heat due to their distinct physical properties, present challenges in traditional welding methods. Additionally, the formation of brittle intermetallic compounds (IMCs) at the joint interface leads to reduced joint strength. To overcome this, a process involving relatively low heat input is considered. In this study, AC pulse MIG welding was applied to dissimilar materials with a thickness of 2.5mm for aluminum alloy (AA5052-H32) and thickness of 3mm for titanium alloy (Ti-6Al-4V). The focus of the research is to analyze the impact of the EN ratio on the weld joint. The influence of electrode wire position, welding current, and EN ratio on the mechanical and metallurgical characteristics of the dissimilar joint was examined. Tensile-shear load tests and vickres hardness tests were conducted for mechanical property evaluation, and energy dispersive spectroscopy(EDS) via scanning electron microscopy (SEM) was performed to investigate the microstructural characteristics of the formed IMC layer at the joint interface. As a result of the experiment, it was revealed that an increase in the EN ratio at a constant welding current led to reduced heat input, resulting in increased tensile-shear load and suppression of IMC layer formation. Under the condition of 110A welding current and 20% EN ratio, the tensile-shear load reached 17.6 kN, and the growth of the IMC layer was restrained to 0.86㎛.