What is the difference between globular and short-circuit transfer?
Short-circuit is a mode of metal transfer in GMAW in which metal is transferred from the electrode to the weld pool via a series of electrical shorts. When the electrode (wire) touches the base material a short occurs and the arc goes out. At this point the current increases dramatically and melts off the wire and creates essentially an explosion. This happens many times per second (around 50 – 200 times!) so we do not see the arc going out, but we do hear the cracking and popping of the arc and we certainly see all the spatter associated with this mode of transfer. This mode of transfer uses low currents and voltages which make it useful when welding out of position. However, the low energy used for this mode of transfer prevents it from being used in most structural applications. Lack of fusion and cold lap are very possible and thus short-arc should be used only thinner materials. It provides very low deposition rates so it is not ideal for a high production environment. Short-arc can be done with 100% CO2 shielding gas or Argon/CO2 mixes.
Globular transfer differs in that the electrode transfers the metal to the molten pool via large droplets (also called ‘globs’). High concentration of CO2 shielding gas and high amperage and voltage make this mode of transfer very violent. A lot of radiated heat, sparks and fume are produced. Weld bead appearance is sometimes hard to control. However, it achieves deep penetration and it is very useful when welding thick sections. It is limited to flat and horizontal positions due to the large puddle it creates. Globular transfer is sometimes used over spray transfer due to the lower cost of CO2 compared to argon.
What is your preferred mode of transfer?
Sources: AWS D1.1/D1.1M:2015 Structural Welding Code
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