Study On TIG Welding Process With Variable Air Supply

Tungsten inert gas welding(TIG welding)is an important method of welding,in actual production has been more widely used.But it is prone to weld defects such as pores and inclusions.And compared with other welding methods,the depth of fusion is shallow,the welding speed is slower,the productivity is lower,the shielding gas is more expensive and the production cost is higher,which greatly limits the application range of TIG welding.It has also become the main problem of its development path to overcome.Therefore,this paper presents an improved method of pulsed gas supply for TIG welding and its effect on TIG welding process.In this study,we use the self-made pulsating air supply device controlled by PLC to complete the protection of gas supply.The protective gas is delivered to the welding torch in the main gas and the auxiliary gas respectively,resulting in pulsating protective gas aspirated under the protective gas flow required by the conventional TIG welding.In this paper,two kinds of gas delivery methods were adopted in the condition of pulsating gas supply with different gas supply frequencies and different frequencies.The welding experiment of 5 mm thick 304 stainless steel is carried out.Contrasting the weld morphology,weld penetration and weld width.And use the high-speed video to record the welding arc under different pulsation frequencies conditions.The results show that the pulsating air supply does not destabilize the arc,and stabilize the protection airflow at a certain frequency and improve the arc energy.The split anode method was used to measure the current density of the welding arc under the traditional air supply method and pulsating air supply conditions.The distribution of welding arc current density under different pulsating air supply conditions was calculated by MATLAB software.It is concluded that the current at the tip of TIG welding is the largest,and the arc current density is the highest in the center.Under the condition of pulsating air supply,the peak current density of welding arc is lower than the welding current of the traditional air supply.The width of maximum welding current is about 0.7 mm,the current concentration area is wider,and the current extremum is reduced.Using the water-cooled copper sensor to measure the size of the arc force under the traditional air-sending mode and pulsating air-sending conditions,it is concluded that the pulsating air-feeding mode improves the welding arc force,the pulsating impact force of the shielding gas strengthens the impact stirring of the weld,The flow of liquid metal in the pool increases the penetration depth,and at the same time,the bubbles and impurities in the pool are more likely to overflow,which reduces the porosity and inclusion of the weld and enhances the quality of the weld.Through experimental research,it can be concluded that pulsating air supply is an effective way to improve TIG welding process.Compared with the traditional air supply method,TIG welding by pulsating air supply can improve the flow of weld metal,improve the welding quality and save the consumption of protective gas.