Study On Mechanism Of The Activating Flux Coated Wire For Magnesium Alloy Welding And Development Process

For the characteristics of low density,high specific strength,good electromagnetic shielding and recyclable,Mg alloys are praised of the green engineering material in 21^st century, which have recently attracted great attention in academic research and industry application. However,the filler wire of Mg and its alloy can't meet the demands of manufacturing at present and it has been the main problem which limits the application of magnesium alloy structural components.Hereby,the research on Mg filler wire is becoming a focal topic all over the world. In this paper,the Mechanism of the activating flux coated wire for magnesium alloy welding was studied.The interaction behavior between flux and arc plasma was studied.A practical application magnesium alloy flux wire was developed.Magnesium alloy activating flux wire of TIG welding increasing the role of penetration welding,which is an ideal high-performance magnesium alloy welding method.It was found that various welding conditions such as welding current,welding arc length,welding shielding gas flow rate,and welding speed,influence the effectiveness of the activating flux on weld penetration increasing in different levels.The maximum increase level is the 300%of the weld penetration with normal wire.In order to analyze the effect of activating fluxes on the weld bead and the arc shape, activating tungsten gas(TIG) welding for magnesium alloy has been studied using flux single side coated and flux bounded coated.The result indicated that ZnCl₂ flux with low thermal stability changed current channel conductive of the arc,so the arc shape was changed significantly.TiO₂ flux with high thermal stability could not change the current channel conductive of the arc,so the arc shape was not changed significantly.The spectra of arc plasmas in TIG welding with three different kinds of wires were analyzed,and the electron temperature and electron density of arc plasma were calculated.In the flux coated wire welding,the intensities of spectral lines of Mg increase compare with normal wire.The amount of the evaporation of magnesium will increase dramatically when flux coated wire was used.Due to the low ionization energies of the evaporation of magnesium and the activated flux elements(the dissociation of flux),the ionization degree of the arc plasma increases.The electron temperature of the arc plasma decreases with the ionization degree of the arc plasma increases.The current density increase and the arc conducting channel constriction with the electron density increase which is induced by the ionization of magnesium and flux elements atoms.The energy density of arc plasma enhances,which is the main reason the weld penetrating depth substantial increase.A practical application magnesium alloy flux wire was developed on the basis of study on mechanism of the activating flux coated wire for magnesium alloy welding.The welding test with the flux wire was carried out.The effectiveness of the activating flux on weld penetration increasing and the performance of filled wire were best of all.The binder had no obviously harmful effects on the activating flux wire welding performance.The strength of the flux wire welded joints are up to more than 90%of the base metal.