Research On Formation Mechanism And Arc Sensing Characteristics Of Local Dry Horizontal Welding

The local dry horizontal welding process has a large number of application requirements in the welding of underwater structural parts.However,in the horizontal welding,the droplets and the molten pool are affected by the gravity,which can easily cause the defects of the upper undercut and the lower weld.Local dry welding requires the use of high-pressure gas to discharge the water around the welding torch.The turbulent wind field generated by the high pressure gas severely affects the arc morphology and the droplet transfer characteristics.Therefore,how to ensure the welding quality has become a major problem that restricts the application of the partial dry horizontal welding process.For this reason,this article studies the wind field characteristics,arc shape,droplet transition characteristics,and molten pool behavior in the drainage hood.It attempts to reveal the partial dry welding seam forming mechanism and provides technical support for welding quality control.The numerical simulation of the wind field in the drainage hood was carried out.The results show that the inlet pressure is greater than 0.05 Mpa.When you can achieve a better drainage effect.After the drainage is completed,an upward wind field is formed in the hood,which is beneficial to supporting the collapsed molten pool.A transparent drainage cover was made to observe the drainage process and drainage effect.The results show that the drain cover can drain quickly and the gas flow inside the hood is consistent with the numerical simulation results.High-speed video was used to observe the partial dry arc welding behavior.As a result,it was found that the arc brightness gradient was greater in the local dry environment.Increasing the welding current increases the brightness of the arc,the size of the spot region,and the area of the arc column.The shape of the arc gradually changes from a bell jar type to a triangle,and the influence of the crosswind on the arc is reduced.For large currents,large amounts of iron vapor exist in the arc space and numerical simulations are performed.The simulation results show that the presence of iron vapor increases the current density,increases the stiffness of the arc,and contracts the arc.The characteristics of the droplet transfer in the transverse welding of the local dry process were analyzed.In the short-circuit transient state,due to the influence of the lateral wind field,the B-type short circuit transition is more likely to occur.In the transition of large droplets,due to the large volume of the droplets,the supporting effect of the lateral wind field is not obvious,and the droplets transition into the molten pool along the inclination of the welding wire.During the transition of the jet,the lateral wind field has less influence on the arc,which causes the droplet to deflect slightly upwards,which helps to reduce the degree of squatting in the molten pool.The forming characteristics of the partial dry welding seams were analyzed.The results show that: when the short-circuit transition occurs,the penetration depth is shallow and the spatter is large;when the large-drop transition occurs,the undercut of the upper side of the weld seam and the collapse of the weld pool are serious;the weld quality during the transition of jets It is better,the melting depth is larger,and the collapse phenomenon is lighter.The numerical simulation of the local dry horizontal welding pool shows that the cooling rate of the molten pool becomes faster under local dry conditions,and the depth of penetration increases with the increase of water depth,and the collapse phenomenon first decreases and then increases.The experimental investigation of the arc sensing characteristics in the local dry welding environment was carried out.The experimental results show that the lateral wind field has a great influence on the stability of the welding process.With the increase of the lateral wind speed,the arc extinguishing rate of the welding process increases significantly.The multiple-regression method was used to process the experimental data,and arc sensing models with different lateral wind speeds were obtained.The model shows that the sensitivity of the arc sensor becomes worse as the lateral wind speed increases.