Pulse MIG welding introduction
Nowadays, more and more aluminum alloy welding adopts MIG welding, especially pulse MIG welding with excellent performance, and even double pulse MIG welding.
Due to its high welding efficiency, it can realize semiautomatic and fullautomatic welding, and the weld depth large and the strength high. But then again, she’s not as well formed as TIG. The pulse current of FGW is at a certain average current. The current output from the welding power source changes with a certain frequency and amplitude to control the droplet transition to the weld pool rhythmically. The base current maintains the steady combustion of the arc and preheats the base metal as well as welding wire.
The ideal state of transitioning a droplet with a pulse realize stably. And the transition of nozzle (or droplet) is achieved. The average current value is lower than the critical current value and the heat input is small. The adjustment range of welding current is wide. The average welding current is to adjust the wire feeding speed, which can be used for thin plate welding (not less than 1mm). It can also be used for back plate welding, especially thick wire welding sheet, wire feeding speed is still very stable, can effectively control the heat input.
As the output characteristic of the power supply is reverse connection of current. The cathode has strong atomization ability, which can effectively remove the alumina film. And the pulsed arc can also have a strong stirring effect in the molten pool. Which can change the metallurgical properties of the molten pool and be beneficial to eliminate the welding defects such as porosity and non-fusion.
Pulse MIG welding classification
There are two main types of pulse MIG welding current arc mode: medium frequency pulse mode. It is a common aluminium and aluminium alloy pulse arc mode. Generally choose hard pulsed arc, high frequency pulse, to highly concentrated arc of welding waveform to strengthen the system. When the welding aluminum and aluminum alloy to remove oxide film role well, penetration, suitable for high speed automatic welding and robot welding.
The welding specification of aluminum and aluminum alloy should be adjusted in the state of sub-jet transition (i.e. the arc voltage is low). The droplet is accompanied by a small amount of short circuit transition in the jet transition.
The welding wire melting jet pointing is good. The weld formation is beautiful. The conductive nozzle is not easy to burn. And the arc combustion is stable. There’s a low frequency pulse mode, good welding machine mostly adopts double pulse mode . That is added to the pulse signal pulse, reflect on the wire feed for pulsating wire.
Wire feed can be observed from the speed of the wheel speed is uniform. And for the operator don’t swing can weld a beautiful fish scales, at or near beautiful effect of TIG welding. Then when used according to the weld appearance quality requirements. It can be adjusted to the level of pulse, pulse frequency and pulse rate. This kind of welding machine, such as: YM400GE;TPS – 5000, etc.
Practical application of pulse MIG welding
Pulse MIG welding of aluminum and aluminum alloy often crack, for this reason, should choose the appropriate wire. Such as: aluminum alloy hull (5083) wire 5183. Aluminum alloy car (6005,7005) welding wire is 5356. Petrochemical ethylene polypropylene warehouse (LF2) welding wire for S331. Aluminum and aluminum alloy tank car (L2,LF5) welding wire is S301, S331.
Aluminum and aluminum alloy welding often produce pores (mainly hydrogen pores), pulse MIG welding is no exception, so the first cleaning work to be strict. Pay attention to the ambient temperature and humidity when welding. Reducing welding speed and increasing line energy can increase the time of weld pool.
High purity argon or argon-helium mixed gas is used to improve the heat capacity; Change the shape of the molten pool, make the tip V deform into a round bottom; Extending the residence time of the molten pool, and facilitate the gas escape.
