Let’s begin by understanding duty cycle. We all know what it is, but just for a quick refresh: Duty cycle is a rating measurement of 10 minute increments using CO2 gas. So, if we take a 350 amp gun as an example – that means at it’s maximum it can weld 10 minutes at 350 amps with a constant current using CO2 gas.
Now take into consideration factors that affect duty cycle. Argon base gas – which mixes Argon at 75% and CO2 at 25% won't cool a gun like 100% CO2. Many other gas mixes are used in welding beyondf those two mixes, such as Argon 90/10 and Argon 95/5. Pulse is yet another factor that lowers your duty cycle.
There’s also the consideration of constant voltage. Constant Voltage, or Current, is used in MIG welding. Polarity – the direction the current flow goes can be either Straight or Reverse in nature. In MIG welding, you use Reverse Polarity Constant Voltage. In this process, the heat produced is created on the ground side of the work, while the nozzle and the contact tip are exposed to reflected heat. In this welding process, CO2 acts as a cooling agent, with smoke acting as the filtering agent – shielding the reflected heat.
Pulse welding is the process of pulsing your weld current several times per second instead of holding it constant. Pulsing causes the arc to act like its welding hotter than it actually is. However, the torch will react like the current is at the peak of the pulses rather than the “average” as read on the current meter of the power source. That’s because the arc is starting and stopping constantly, which takes more power. Also, pulse welding creates less smoke, considerably less, in fact, and doesn’t filter the reflected heat to the nozzle and contact tip.
So, how does that lesson on welding actually affect the torch you may want to use?
Well, it’s all a matter of the heat you’re generating. Air cooled torches depend on thermal transfer to conduct the heat from the contact tip through the handle and into the power cable before radiating into the air. This is where the duty cycle becomes important – how much heat is generated and how fast it can be conducted and radiated? For example, aluminum power cable guns are a little better at radiating heat than copper, but are also less capable of conducting current. The nozzle is insulated, electrically and thermally from the gun and radiated heat on its own.
Water cooled guns act differently. With water-cooled (or gas or liquid-cooled…. they all mean the same thing), these depend on water (or liquid) to transfer heat into the power cable, contact tip and the nozzle. Systematically, it is a more efficient system for cooling. Heat in the water is transferred to a radiator, into a holding tank and circulated back to the welding torch.
Looking back at the break down of gases welding styles, consider that an air cooled torch rating is reduced 40 to 50% using Argon based gases, and another 20 to 30% when pulse welding is used.
Water cooled guns, on the other hand, get a duty cycle reduction of 10% for Argon base gas, and a negligible reduction for pulse welding.
There are ample pros and cons to both welding gun types, but let’s break them down here by category, and you can decide whether you’ve fairly considered each:
District Sales Manager at ABICOR BINZEL