Research On A-TIG Repair Welding For Cast Magnesium Alloys

Magnesium alloys were widely used in aerospace, automotive, electronic communication, and other fields because of its excellent characteristics, and the use of magnesium alloy parts can effectively realize the goal of light weight. Production cost of wrought magnesium alloys is higher, so cast magnesium alloys were widely used in industry presently. Various types of defects appear easily such as porosity, crack, or mechanical defects occurring in the process of processing and transportation. These defects not only cause the waste of materials but also influence the delivery of products, so repair welding has important economic and social benefits for casting defects.Traditional tungsten inert gas (TIG) welding is often used repair welding, but it cannot meet the requirement of the engineering because of its low production efficiency, low yield. In order to improve TIG weld penetration and improve quality of weld, people put forward activeness tungsten argon arc welding (Activating Flux TIG, A-TIG) welding method, which is coated with active fluxs on the base material before welding. Under the same welding specification, A-TIG welding can increase weld penetration, greatly reduce weld porosity. Therefore, this article will make use of A-TIG repair welding, and reveal its difference with TIG repair welding, so as to improve the efficiency of repair welding and yield.Simulating cast magnesium alloys hole defects repair welding test, TIG repair welding will heal only 1 mm deep holes under the condition of welding parameters (1=120A, V=5mm/s),but A-TIG can heal 3 mm deep hole; Under healing (h=3 mm, â–¡=3mm) holes conditions, when welding current is 200 A, TIG repair welding can obtain at the same healing effect with A-TIG repair welding when the welding current 120 A, but porosity defects in the weld; simulating wrought magnesium alloys hole defects test found that the ability of A-TIG repair welding is better than that of TIG repair welding, but the surface of the weld and longitudinal section did not find porosity defects after repair welding, which suggest that differences between cast magnesium alloys and wrought magnesium alloys lead to weld porosity. Microstructure and microhardness of welding joints revealed that the use of A-TIG repair welding can not only realize the deep hole of healing, but also reduce weld porosity defects.This article will reduce repair welding defects and explore the mechanism of A-TIG repair welding. Researching on A-TIG welding automatic cold wire filling technology and simulating repair welding hole defects test, A-TIG welding automatic cold wire filling repair welding did not find porosity defects. A-TIG repair welding can reduce porosity defects, which introduce zirconium to weld to improve the weld ability of solid hydrogen and A-TIG welding molten pool internal liquidity has consistency, which helps to eliminate porosity defects. Cast magnesium alloys repair welding specification process is put forward.