Difference between AC Arc Welding and DC Arc Welding

AC (Alternating Current) and DC (Direct Current) are the two different types of electric current that are used in the welding process. AC arc welding is commonly used for down-hand heavy plate welds, fast fills and with aluminium TIG welding with high frequency, while DC welding is better for welding thinner metals. Also, the equipment used for DC arc welding are also cheaper than AC arc welding machinery.

The specifications of equipment used in practice for AC and DC arc welding are given as follows −

  • Specifications of AC Arc Welding Machinery - AC transformer − Step down, oil cooled, 3-phase, 50 Hz, Current rating = 50-400 A, Open circuit voltage = 50-90 V, Energy consumption = 4 kWh per kg of metal deposit, Power factor = 0.4, Efficiency = 85 %.

  • Specifications of DC Arc Welding Machinery - DC Generator − 3-phase motor-generator set, 50 Hz, Current rating = 125-600 A, Open circuit voltage = 30-80 V, Arc voltage = 20-40 V, Energy consumption = 6-10 kWh per kg of deposit, power factor = 0.4, Efficiency = 60%.

Now, the following table gives the comparison between AC arc welding and DC arc welding −

ParameterDC Arc WeldingAC Arc Welding
Power ConsumptionThe power consumption by the DC arc welding is high.Power consumed by the AC arc welding is lower than that of DC arc welding.
EfficiencyThe efficiency of DC arc welding is low.The AC arc welding is more efficient than DC arc welding.
CostThe cost of DC arc welding is high.The AC arc welding is less costly than DC arc welding
Arc StabilityThe DC arc welding produces a stable arc.The arc produced by the AC arc welding is unstable.
WeightThe welding set required for DC arc welding is heavy.The welding set of AC arc welding is light weight.
OperationThe operation of DC arc welding is noisy.The operation of AC arc welding is noiseless.
Electrode UsedIn DC arc welding, all types of electrodes, i.e. bare and coated electrodes can be used because the polarity of the supply can be changed suit the electrode.In AC arc welding, only coated electrodes can be used. It is because the current constantly reverses with every cycle.
Welding of thin sectionsDC arc welding is preferred for welding of thin sections.AC arc welding is generally not preferred for welding of thin sections.
PolarityIn case of DC arc welding, the electrode is always negative and the job is positive.In AC arc welding, the electrode can act as anode while job acts as cathode and vice-versa.
MachineryThe DC generator used in DC arc welding has rotating parts and hence it is more complicated.The transformer used in AC arc welding has no moving parts and is simpler.
Capital & Maintenance CostThe cost of DC generator is high and its maintenance cost is also high.The cost of AC transformer is low. Also its maintenance cost is low.
Arc BlowIn DC arc welding, the problem of arc blow is severe and cannot be controlled easily.The problem of arc blow does not arises in case of AC arc welding.