Welding Parameters

Arc voltage

Arc voltage is related to the arc length. For processes where the arc voltage is controlled by the power source (SAW, MIG/MAG and FCAW) and can be varied independently from the current, the voltage setting will affect the profile of the weld.

As welding current is raised, the voltage also needs to be raised to spread the weld metal and produce a wider and flatter deposit.

For MIG/MAG, arc voltage has a major influence on droplet transfer across the arc.

Welding current

Welding current has a major influence on the depth of fusion/penetration into the base metal and adjacent weld runs.

As a general rule, the higher the current the greater the depth of penetration

Penetration depth affects dilution of the weld deposit by the parent metal and it is particularly important to control this when dissimilar metals are joined.

Polarity

Polarity determines whether most of the arc energy (the heat) is concentrated at the electrode surface or at the surface of the parent material.

The location of the heat with respect to polarity is not the same for all processes and the effects/options/benefits for each of the main arc welding processes are summarised below:

Welding Process – SMAW (Shielded Metal Arc Welding)

Polarity

DC +ve – Best Penetration

DC –ve - Less penetration but higher deposition rate (used for root passes and weld overlaying)

AC - Not suitable for some electrodes, Minimises arc blow

Welding Process – TIG (Tungsten Inert Gas Welding)

Polarity

DC +ve – Rarely used due to tungsten overheating

DC –ve – Used for all metals – except Al/Al alloys (and Mg/Mg alloys)

AC - Required for Al/Al alloys to break-up the refractory oxide film

Welding Process – GMAW solid wires (MIG/MAG) (Gas Metal Arc Welding)

Polarity

DC +ve – Used for all metals and virtually all situations

DC –ve – Rarely used

AC - Not used

Welding Process – FCAW/MCAW gas-shielded and self shielded cored wires

Polarity

DC +ve – Most common

DC –ve – Some positional basic fluxed wires are designed to run on -ve; some           metal cored wires may also be used on -ve particularly for positional welding

AC - Not used

Welding Process – SAW (Submerged Arc Welding)

Polarity

DC +ve – Best penetration

DC –ve – Less penetration but higher deposition rate (used for root passes and overlaying)

AC - Used to avoid arc blow – particularly for multi-electrode systems