알루미늄합금 용접의 보호가스 영향에 관한 연구

Abstract

ABSTRACT

A Study on Influence of Shield Gas in Aluminium Allow Welding

Mo, Sung-Chang Advisor : Prof. Chung, Jae-Kang Ph.D. Mechanical & Metallurgical Education Graduate School of Education, Cosun University

This study was to evaluate welding strength of Al5083-O aluminum alloy according to the shield gas mixing ratio and heat input. The GMA(Gas Metal Arc) welding of the base metal was carried out with four different shield gas mixing ratios(Ar100%+He0%, Ar67%+He33%, Ar50%+He50%, and Ar33%+He67%). Tensile and Charpy impact test were performed from room temperature(+25℃) to cryogenic temperature (-30℃, -85℃, and -196℃). The specimens were specified by base metal, weld metal, fusion line, and HAZ specimen according to the machined notch position to investigate the strength of the specified weld zones.

The summarized results from the experiment are as follows ;

1) Regarding the influence on the bead shape of the shield gas mixing ratio, the bead width was greatest in pure Argon. But the bead depth and area were greatest in Ar33%+He67% mixture considering that the lower Argon gas ratio, the higher bead depth and area. Also, the dilution was also best in the mixing shield gas ratio.

2) The size and number of defects were least in Ar33%+He67% mixture. Higher Helium gas ratio resulted less defects in the radiographic test.

3) The tensile strength was not affected greatly from shielding gas mixing ratio, heat input, yield strength and elongation were not affected from heat input. But, the higher yield strength and elongation were obtained with the higher Helium gas mixing ratio.

4) The Charpy absorbed energy level was lowest in weld metal, and it increased in order of fusion line, base metal and HAZ. Ar33%+He67% mixture resulted the best toughness and it can be consider the more Helium gas results the higher absorption energy. The energy increased with the temperature from +25℃ to -85℃ but it decreased at -196℃.