Mig weldingClick image to enlargeby Robert L. Bitzky

Tips on how to set the parameters for GMAW short arc welding

 

The short arc circuit transfer mode of GMAW requires a dynamic balance between two key variables: wire feed speed and voltage. Tuning these parameters to best suit the application can easily produce sound welds on metals as thin as 20 ga. carbon steel.

In short circuiting arc welding, metal is transferred from the electrode to the puddle by repeated short circuits. To obtain a smooth, stable arc, the welder must select a wire feed speed and then balance that wire speed with the proper arc voltage.

Here are some general guidelines to achieve a stable arc:
The first step is to consider the thickness of the material to be welded as well as the fit up of the joints. The low heat input, low penetration of short arc makes it most suitable for sheet metal material thicknesses up to 0.25 in. (0.635 mm). As a fundamental rule, each 0.001 in. (0.025 mm) of material thickness requires 1 Ampere.

Next, determine the best wire diameter for the application. Smaller diameter wires are capable of lower currents (less heat reduces distortion); larger diameter wires generate higher currents and bring with them the potential for burn through gage materials.

When selecting wire diameter, consider the following:

  • 0.023 in. (0.058 mm) The smallest diameter GMAW wire is suitable from 30 to 125 Amps. However, this wire's small size makes it more costly as well as harder to feed.
  • 0.030 in. (0.762 mm) This small diameter wire is suitable from 45 up to 180 Amps. This size wire offers more consistent feeding at a lower cost and is ideal for all around sheet metal work.
  • 0.035 in. (0.889 mm) For 55 up to 200 Amps, this wire is readily available and the most affordable of the smaller diameter wires. However, these electrodes can be more challenging for use on thin materials (20/ 22 gauge) because their higher current level increases the likelihood of burn through.
  • 0.045 in. (1.016 mm) This larger diameter wire handles higher currents and heavier materials, but is not normally recommended for thin gauge materials. The .045 in. diameter wire is suitable from 0.124 in. (3.175 mm) and up.

Once a wire is selected, the welder must set the proper wire speed and voltage to stabilize the arc:
Follow the manufacturer's guidelines for setting the wire speed and voltage for your application. These guidelines are usually an excellent starting point. Next, listen to the arc. A properly tuned arc sizzles (like the sound of frying bacon). There should be no popping or spitting. Adjust the voltage until it stabilizes into a uniform frying sound.

Beyond these basic guidelines, there are other variables to consider, including the wire feed system, which is the single biggest issue in producing successful welds.

To tune the arc for success when GMAW short arc welding:
Choose the wire size to fit your application.

Set the wire feed speed to achieve the proper current level for the material/joint configuration being welded.

Fine tune the voltage (up or down) to produce a uniform smooth stable arc with that perfect frying sound. SMT

Robert L. Bitzky is a business manager with ESAB Welding & Cutting Products, Florence, SC

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