Study Of Laser Assisted Activating TIG Welding Process

Recently,study of high efficiency and energy saving new welding processes has become one of hot topic of the international welding fields.Recent study of activating welding showed that,the temperature coefficient of surface tension was changed by Oxygen was the main mechanism of increasing weld penetration for mild steel,stainless steel and other steel products.A new activating welding process has been put forward by changing the way of adding activating elements-LA-TIG welding(Laser assisted Activating TIG Welding).Before the TIG welding,using the assisted Laser to prepare a thin oxide layer instead of coating activating flux,the weld penetration also can increase.Taking the Q235 low-carbon and SUS304 austenitic stainless steel as investigation object,the influence of welding conditions of LA-TIG on welding penetration and welding width was investigated.The influence of oxide layer on weld microstructure was studied by metallographic analysis,and the low-temperature impact toughness,corrosion resistance and hardness were also tested.Through the weld chemical composition analysis,the chemical composition differences between the traditional TIG welding and LA-TIG welding were studied.The results showed that the mechanical properties and chemical compositions of LA-TIG welding were very close to traditional TIG welding,and the oxide layer had little effect on the microstructure and performance of LA- TIG weld.In terms of the mechanism of increasing weld depth,first,the effect of arc contraction on weld depth was studied through the analysis of arc shape and welding voltage.Second,the effect of oxides in oxide layer on surface tension was studied by XPS test.Third,the content distribution of oxygen in the welding pool was tested by SEM and EDS analysis.At last,the relationship between the weld penetration and oxygen content was studied by calculating the oxygen content of the surface of welding pool.The results showed that arc contraction was not the main reason for increasing weld penetration,the oxygen in oxide layer as the activating element can change the temperature coefficient of surface tension was the main mechanism. Oxygen content of weld was low,and the oxygen mainly existed on the weld surface, further explained the oxide layer had little influence on weld performance.In the activating flux oxygen exists as compound,so the effect will be disturbed by other elementary.Because oxygen is the only activating element used in LA-TIG welding,we can investigate penetration effected by oxygen.The welding method can be used in automated production which can raise productivity of welding,which has an important significance in promoting the application of activating welding.