The air is easy to intrude into the weld area,because the protection effect of the fillet joint is poor .So we should preload the baffle to improve the protection effect of the argon flow .

The welding parameters of argon arc welding mainly include welding current, arc voltage, welding speed, welding diameter, argon gas flow and nozzle diameter, etc. The size of these parameters varies with different welding forms.

CO2 gas shielded welding.CO2 gas shielded welding is an arc welding method with CO2 gas as the shielding gas.It uses the welding wire as an electrode, and the arc heat generated between the welding wire and the workpiece melts the welding wire and the workpiece to form a welding connector .

CO₂：The main advantages of CO2 gas shielded welding are the following :

①Low cost of welding.Protecting the arc and molten pool with CO2 is not only cheaper than argon, but also cheaper than using flux and electrode coating to protect the welding area.

②Good quality of welding.The arc and molten pool are protected by CO2 gas and are not easy to affect by air.Welding fast and small heating affected zone

③High productivity.High current density, heat concentration and high welding speed due to the automation of the wire feeding operation

④Good operating performance.Open arc welding, easy to find and deal with problems, with the flexibility of manual welding, suitable for all-position welding.

CO₂ The disadvantage of CO2 gas shielded welding are the following ：When using the larger currenfor welding, the spatter will be larger, the smoke will be more , the arc will be stronger, and the surface of the weld is not smooth and will looks bad.；When the control or operation is not appropriate, it will be easy to generate air holes；Welding amusement equipment is more complicated.

（3）Submerged arc welding Submerged arc welding can be divided into automatic welding and semi-automatic welding according to the degree of mechanization.The difference between them is the following :In the former, both the wire feeding and the relative movement of the arc are automatic, while in the latter, only the wire feeding is automatic, and the arc movement is manual.Since the application of automatic welding is far more extensive than that of semi-automatic welding, the so-called submerged arc welding generally refers to automatic submerged arc welding.

The working principle of submerged arc welding ：The two poles of the welding power source are connected to the contact tip and the weldment respectively During welding, the granular flux is evenly deposited on the part to be welded by the flux funnel through the hose, the welding wire is fed into the welding area by the wire reel through the wire feeding mechanism and the contact tip, and the arc is between the welding wire under the flux and the base metal.

Arc heat causes local melting and partial evaporation of welding wire, flux and base metal.Metal vapor, flux vapor, and gas evolved during the metallurgical process form a cavity around the arc, and the molten flux forms a slag film on top of the cavity.This slag film acts as a barrier, isolating the arc, the liquid metal from the air, and shielding the arc from the cavity.

Under the cavity, the base metal melts locally to form a molten pool; in the upper part of the cavity, the welding wire melts to form droplets, which transition into the molten pool in the form of slag wall transition, and only a few droplets take free transitions.

Features of submerged arc welding：

①Submerged arc welding has the following advantages：

a.High productivity.1000A,The welding current used in submerged arc welding can reach more than 1000A, so the penetration ability of the arc and the deposition efficiency of the welding wire are relatively high.

b.Good welding .On the one hand, since the welding parameters of submerged arc welding can be kept stable through the adjustment of the automatic arc adjustment system, and the requirements for the welder’s operating technology are not high, the weld seam is well formed and the composition is stable;On the other hand, slag is also used for protection, and the effect of isolating air is good.

c.Good working conditions.When using submerged arc automatic welding, there is no dazzling arc light, and no manual operation is required, which can not only improve the working environment, but also reduce the labor intensity.

d.Save metal and electricity.Welding parts with a thickness of less than 25mm can be welded without grooves, which not only saves the metal lost due to groove processing, but also greatly reduces the amount of filler wire in the weld.At the same time, due to the protection of the flux, the burning loss and spatter of the metal are also greatly reduced.Since the arc heat of submerged arc welding can be fully utilized, the power consumption per unit length of the weld is also greatly reduced.

②Disadvantages of submerged arc welding：

a.There are restrictions on where welding can be applied.Due to the use of granular flux for welding, it is generally only suitable for welding in the flat welding position (depressed position), such as butt joints in the flat welding position, fillet joints in the flat welding position and horizontal welding position, and surfacing welding in the flat welding position, etc. For other locations, special amusement equipment is required to ensure flux coverage of the weld zone.

b.Weld thickness is limited.In submerged arc welding, the stability of the arc usually deteriorates when the welding current is less than 100A, so it is not suitable for welding thin plates with a thickness of less than 1mm.

c.The processing and assembly requirements of welding parts are strict.Because submerged arc welding cannot directly observe the relative position of the arc and the groove, it is necessary to ensure the machining and assembly accuracy of the groove, or use an automatic welding seam tracking device to ensure that partial welding does not occur.