Arc Characteristics And Metal Transfer Behavior Of MAG Welding With Preheated Wire

Efficient welding method is an important development trend of welding method,and the traditional way to realize efficient welding method is owned to the increment ofwelding current, but the high welding current would influence the steady of weldingprocess. Therefore, this thesis promotes a new efficient welding method—MAG weldingwith preheated wire which can achieve efficient welding with lower welding current.Compared with traditional MAG welding, the difference of MAG welding withpreheated wire is preheating the wire before the wire enters into the arc space. This thesisdesigns the torch of MAG welding with preheated wire, using a TIG arc to preheat thewire. Based on that, this thesis establishes the welding system platform, the arc electricsignal acquisition system which obtains the arc voltage and welding current, the highspeed camera system which shoots the process of metal transfer.This thesis analyses the difference between MAG welding with preheated wireand traditional MAG welding on heat source of melting wire. Because the real-time wiretemperature measure cannot be realized during welding process, the temperature of wireis measured when the MAG arc is not burning.This thesis studies how the wire temperature variation influences arc characteristics,metal transfer and weld formation in MAG welding with preheated wire when the MAGwelding system adopts the constant voltage power source and the constant speed wirefeeder.The test results show, on condition that the arc voltage and wire speed is notchanged, when wire temperature get higher, the welding current gets lower. Afterpreheating wire, original spay transfer changes into projected transfer, original projectedtransfer changes into globular transfer, the frequency of metal transfer gets lower and thesize of droplet gets bigger. When the arc voltage and welding current is not changed,preheating wire needs higher wire feeding speed, the frequency of metal transfer gethigher and the size of droplet is not changed.In addition, the critical welding current value of spray transfer in MAG weldingwith preheated wire is lower than traditional MAG welding. Welding procedure testshows that preheating wire could reduce weld penetration and weld width, increase weldreinforcement.