Argon arc welding is a gas-shielded welding that uses argon as the shielding gas.The argon arc welding process is shown in Figure Schematic diagram of argon arc welding.
Since argon is an inert gas, it will not chemically react with the metal, so it will not cause the alloying elements in the welded metal to be burned, and it can fully protect the molten pool metal from oxidation. And because argon is insoluble in liquid metal at high temperature, it is not easy to produce pores in the weld. Therefore, the protective effect of argon is effective and reliable, and higher welding quality can be obtained.
During argon arc welding, argon gas forms a protective layer around the arc, so that the molten metal, tungsten electrode tip and welding wire are not in contact with the air, so the alloy elements in the metal to be welded and the welding wire are not easily burned during the welding process. In addition, inert gases such as argon are also insoluble in metals, so no pores will be formed during welding, which greatly improves the quality and efficiency of welding projects.
Therefore, argon arc welding has the following advantages compared with electrode arc welding:
Because argon is an inert gas, it does not decompose at high temperature, does not chemically react with the weld metal, and is insoluble in liquid metal, so the effect of gas protection is the best, and the welding pool can be effectively protected during welding. Metal.
Argon gas is a monoatomic gas. There is no secondary heat-absorbing and exothermic decomposition reaction at high temperature, poor electrical conductivity, and the compression effect and cooling effect produced by the argon flow, which makes the arc heat concentrated and the temperature high. Generally, the center temperature of the arc column can reach Above 10000K, while the arc column temperature of electrode arc welding is only 6000~8000K.
Due to the concentrated heat of argon arc welding, the argon gas ejected from the nozzle has a cooling effect, so the heat-affected zone of the weld is narrow and the deformation of the weldment is small.
No welding slag is protected by argon gas, which improves the welding work efficiency and the weld shape is beautiful and of good quality.
Argon arc welding adopts open arc operation, the visibility of molten pool is good, it is easy to observe and operate, and the operation technology is easy to master.
Argon arc welding is flexible, not limited by space and position, suitable for welding in various positions, and easy to realize mechanization and semi-automation.
In addition to ferrous metals, it can be used for welding stainless steel, aluminum, copper and other non-ferrous metals and their alloys, and is also commonly used for welding structural steel pipes and thin-walled parts.
Although argon arc welding has many welding advantages, there are also unavoidable shortcomings, which are mainly manifested in the following aspects:
The ionization potential of argon gas is high and arc ignition is difficult, especially for tungsten argon arc welding (TIG), high-frequency arc ignition and arc stabilization devices are required.
Safety protection issues. The intensity of ultraviolet rays produced by argon arc welding is 5 to 30 times that of arc welding with electrodes. Under strong ultraviolet radiation, oxygen molecules and oxygen atoms in the air collide with each other to generate ozone (O3), which is harmful to the welder’s body. In addition, if tungsten argon arc welding (TIG) uses radioactive tungsten electrodes, it will also be harmful to welders to varying degrees. The currently popularized cerium tungsten electrodes are less harmful to welders.
Argon tungsten arc welding is an arc welding method that uses inert gas-argon protection and uses tungsten rods as electrodes. The tungsten electrode does not melt during welding. This kind of non-melting argon arc welding is also called tungsten argon arc welding, or TIG welding for short. The working principle of welding is shown in Figure Working principle of argon tungsten arc welding. The argon gas ejected from the nozzle forms a thick and dense gas shield in the welding area to isolate the air. Surrounded by the laminar flow of argon gas, the arc flows between the tungsten electrode and the Combustion between the weldments, use the heat generated by the arc to melt the place to be welded and the filler wire, and connect the two separated metals together to obtain a firm welded joint.
There are many types of argon arc welding, and the main classifications are shown in Figure Classification of argon arc welding.
Metal arc welding is a welding method that uses a welding wire with similar or identical composition to the weldment as the electrode and uses argon as the protective medium. Metal arc welding is also called metal arc welding, or MIG welding for short.
MIG welding is divided into semi-automatic and automatic welding. Semi-automatic melting electrode argon arc welding relies on hand-operated welding torch, and the welding wire is output through the welding torch through the automatic wire feeding mechanism; automatic melting electrode argon arc welding is driven by the transmission mechanism to move the welding torch, and the wire feeding mechanism automatically feeds the wire, that is, mostly mechanical operation.
Non-melting electrode argon arc welding uses high-melting-point tungsten rods as electrodes. Under the protection of argon laminar flow, it relies on the arc heat generated between the tungsten rod and the weldment to melt the welding wire (generally, the welding wire is added in front of the tungsten electrode) and the base metal.
Non-melting electrode argon arc welding is also called tungsten argon arc welding. Tungsten argon arc welding can be divided into manual argon tungsten arc welding and automatic argon tungsten arc welding according to different operation methods. Manual argon tungsten arc welding is widely used in my country. It can weld various steels and non-ferrous metals. In power stations, boilers and other industries, it has been widely used for bottom welding of heated pipes, containers and pipe joints.
If a pulse device is added to the melting pole argon arc welding (MIG) or non-melting pole argon arc welding (TIG) power source, the welding current can be changed regularly, that is, the pulse current is obtained, and it is called argon arc welding with pulse current Pulse tungsten argon arc welding is usually used to weld thinner weldments. The schematic diagram of the pulsed argon arc welding power supply is shown in Figure Schematic diagram of pulse argon arc welding power supply.
There are many forms of pulses and current waveforms formed by the pulse device, and the most commonly used is a square wave, as shown in Figure Schematic diagram of pulse current waveform (square wave).
The square wave pulse current includes the following parameters:
①Pulse peak current (I 0) refers to the maximum welding current used for arc supply, which is used to melt the molten pool formed by metal.
②Pulse maintenance time (t 0), the time used to supply pulse current welding.
③ The base value current (I1) of the pulse to maintain the arc combustion refers to the minimum current value for the arc supply, which maintains the arc combustion and preheats the base material. This current is also called the base value current.
④Maintain the arc burning time (t1), the time to keep the arc burning under the minimum welding current.
When the electrode passes through the pulse current, the weldment forms a molten pool under the action of the arc heat, and the welding wire melts and drops into the molten pool (filling in from the outside during pulse tungsten argon arc welding). When the maintenance current appears, due to the heat reduction, There is no melting phenomenon, the molten pool gradually shrinks, and the liquid metal solidifies to form a solder joint. When the next pulse current arrives, a new molten pool will appear at a part of the original welding spot and the new counterpart of the weldment, and so on, and finally form a chain weld composed of many overlapping welding spots, as shown in Figure Weld formation process of pulsed argon arc welding.
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