MMA/SMAW Welding

Also known as stick welding, MMA is the most flexible arc welding process. It involves striking an arc between a covered metal electrode and a workpiece

close-up of MMA welding using a Linde MMA 170 welding machine

MMA is a fusion welding process that uses a consumable, flux-coated electrode to create an electrical arc between the electrode end and the workpiece. 

The heat of the arc causes the electrode, flux coating and the surface of the parent material to melt simultaneously. 

A continuous stream of molten metal flows from the electrode and across the electrical arc and is deposited onto the workpiece surface where it mixes with the molten parent material and a weldpool is formed. 

The flux coating also melts into the weldpool where it floats to the surface and solidifies forming a protective slag coating (similar to ceramic material).

MMA welding is one of the earliest developed and simplest arc welding processes but can still be used to produce high-quality weldments.

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How it Works

The electrode flux coating serves several purposes. As the coating melts it forms a gas shield which protects the molten weldpool and adjacent parent material from becoming contaminated by the atmosphere, this means a separate supply of shielding gas is not required for the MMA process. 

The molten flux coating mixes with the molten weldpool, it then floats to the surface of the weld and solidifies forming a hard ceramic-like coating referred to as slag which protects the surface of the cooling weld bead. The slag coating must be thoroughly removed before depositing further weld beads. Various alloying elements can be added to the flux coating to enhance the quality of the deposited weld metal and alter the welding characteristics of the electrode 

Certain MMA electrodes, such as low hydrogen electrodes, must be stored in a rod oven to prevent moisture from compromising the electrode's low hydrogen qualities.

Deposition rates for MMA welding are fairly low, this has seen MMA welding being largely replaced by MAG welding.

Schematic showing the MMA welding process
Schematic of MMA process in operation

Reduce Costs by up to 40%

We deliver a range of tried-and-tested MMA welding gases under our Specshield, Stainshield, Alushield and Argoshield families. These shielding mixtures use active gases in different concentrations to suit individual application needs. Argon-based mixtures, for instance, replace carbon dioxide with argon as the shielding gas.

Benefits include increased productivity through higher welding speeds, better wetting and penetration and reduced distortion through lower heat input – resulting in cleaner welds and less rework effort. In total, you could save up to 40 per cent on the cost front. Our application experts can advise you on the mixture best suited to your needs. They can also help you select the correct operating parameters for optimum results and support you with the equipment and gas management services you need.

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