Welding Electrode Selection Guide How to select a gas-shielded welding electrode

Efficiencies obtained by switching a welding wire or the welding method are typically neglected. Many gas-shielded electrodes, each one with distinct mechanical properties, arc behaviour, and designed applications, are readily available for a range of diverse welding purposes. Depending on the demands for quality, productivity, and cost, selection is usually made from between three distinct gas-shielded arc welding wires for any kind of distinct application.

Welding Wire Types

There are three principal forms of gas-shielded arc welding wires to select from:

1. Solid gas metal arc (GMAW) welding wire: GMAW combines a solid wire electrode called GMAW electrodes with a shielding gas to protect the weld. The wire plus gas combination have an impact on weld strength. This variety of wire is popular for the reason that it leaves slag-free deposits and does not involve much clean-up, enhancing productivity.
2. Composite GMAW metal-cored welding wire: Metal or flux-cored welding wires have metallic components in the core. These are also slagless, low-clean-up alternatives along with overall performance comparable to solid GMAW wire.
3. Gas-shielded flux-cored arc (FCAW) welding wire: Fluxing and deoxidising agents in the core help protect the weld from the atmosphere and can be designed to influence the mechanical properties of the weld deposit.

Solid GMAW Wire

GMAW process calls for a solid wire electrode or a composite metal-cored electrode. Solid wire electrodes typically are known to as GMAW electrodes. The mechanical properties plus strength of the weld deposit depend first of all on the chemistry of the wire and subsequently on the variety of shielding gas utilised. Shielding gas is essential to shield the weld from the environment. GMAW is usually recommended due to the fact that the weld deposit is slagless and involves a minimum of cleanup, which in turn enhances productivity.

Dirty Steel: Many classifications of GMAW welding wire exist with varying levels of deoxidisers. Highly deoxidised welding wire can tolerate light to moderate levels of surface impurities. For these types of applications ER70S-6 wire is utilised which offers increased levels of silicon together with manganese compared to an ER70S-3 welding wire. An intermediate electrode, ER70S-4, is often selected for applications demanding more deoxidizers when compared with ER70S-3 but less than ER70S-6.

GMAW wire selection ought to be from a crediable welding wire vendor to guarantee reliable chemistry, diameter, and feedability from lot to lot or spool to spool. There is in addition substantial variance in the labelling standards amongst different agencies like European SG2 classification and American Welding Society (AWS). GMAW classed as ER70S-6 conforming to the European SG2 classification do not fulfill ER70S-6 chemistry required by the American Welding Society (AWS) and consequently may possibly not be suited for the required use.

Travel Speed: Solid GMAW welding wire performs very well on a blasted plate workpiece. However, GMAW welding wire doesn't perform as well as metal-cored wire or flux-cored wire on a plate workpiece having heavy mill scale. Solid GMAW welding wires do not deoxidise mill scale conveniently, consequently, impacting the bead shape and travel speeds adversely.

Out-of-position Welding: Solid GMAW welding wire can be used for out-of-position welding using a short-arc procedure on thin materials which yields low deposition rates. An alternative is to make use of pulse-spray welding along with these electrodes which will maximize the deposition rates while still delivering out-of-position capabilities.

Mechanical Properties: Generally, the strength of a weld deposit made with a solid GMAW welding electrode is limited to the strength of the welding electrode. When working with a high-strength, low-alloy base material, it might be challenging to locate a solid steel GMAW wire that will meet the base material requirements. For these types of applications, a metal-cored or flux-cored electrode is more suitable.

Postweld Operations: For certain modes of metal transfer with solid GMAW welding wire, such as short-arc transfer mode and globular transfer mode, some spatter happens that necessitates postweld cleanup. Silicon islands can be deposited in the course of GMAW welding which may require to be removed prior to painting or coating. However, GMAW welding with solid welding wire is typically a clean process that requires minimum postweld operations.

Metal-Cored Wire

Metal-cored welding wires are tubular welding electrodes having metallic constituents in the core. Like solid GMAW welding wire, metal-cored welding wire makes a slagless weld that involves little or no postweld clean-up. The overall performance characteristics of metal-cored welding wires are also comparable to those of solid GMAW welding wires. Previously classified as flux-cored welding wire, metal-cored welding wire are now classified as composite GMAW welding electrodes.

Dirty Steel: Metal-cored welding wire can handle mill scale and surface contaminants much better than GMAW welding wire because of its metallic components. These components assist the metal-cored welding electrode to deoxidise the scale a lot better than solid welding wire, which is the reason this type of welding wire is a better alternative if blasting material prior to welding is not a option.

Deposition: Due to the tubular nature of metal-cored welding wire, the current density of a metal-cored welding wire is increased at a given amperage than a solid welding wire of the same diameter. This can result in higher deposition rates at a supplied amperage. In certain automated applications, large-diameter metal-cored welding wire can easily match or surpass the performance of gas-shielded flux-cored welding wire. However, large-diameter metal-cored welding wire probably won't be suited for semi-automatic welding applications because of the high amperage used in addition to the heat radiated from the arc.

Travel Speed: Metal-cored welding wire is highly recommended when travel speed is the principal issue in the application. On a plate having mill scale, metal-cored welding wire could produce superior wetting and a flatter bead shape as well as enhance productivity due to lower spatter levels, much less post-weld clean-up and faster travel speed.

Out-of-position Welding: Although it is possible to make use of metal-cored welding wire out of position at low amperage in a short-arc transfer mode, metal-cored welding wire is not generally utilised for out-of-position welding with the exception of the vertical-down position. As is the case with solid GMAW welding wire, pulse welding process can improve out-of-position deposition rates with metal-cored welding wire.

Mechanical Properties: Metal-cored welding electrodes are available for high-strength, low-alloy applications. Low-alloy metallic components can be added to the core to attain the sought after mechanical properties. This potential to add components can make it simpler to develop the desired mechanical properties with metal-cored welding electrodes than with solid welding wires of equivalent strength.

Postweld Operations: Some postweld clean-up may be required to remove the silicon islands deposited from metal-cored welding electrodes prior to painting or coating the base metal. However, the overall clean-up time might be reduced due to the fact that metal-cored welding wires generally produce hardly any spatter.

Gas-Shielded FCAW Wire

Gas-shielded FCAW welding wires are tubular electrodes containing fluxing agents in the core, as well as deoxidisers, to provide supplemental protection from the atmosphere. The flux components in these types of welding wires can be engineered to greatly enhance the mechanical properties of the weld deposit. FCAW welding electrodes are available for both out-of-position and in-position welding.

Dirty Steel: FCAW welding wire is the most tolerant of the three types of welding wires for welding unclean base metal. Since it has a flux in the core and is used together with a shielding gas, it provides an added layer of atmospheric safeguard.

Deposition: For high-deposition applications, large-diameter, gas-shielded FCAW welding wires can frequently deposit a lot more kg per hour compared to solid GMAW welding wires or metal-cored welding wires.

An exception to this rule is the tandem GMAW process which utilises two solid wires in one weld pool. Tandem GMAW welding process offers benefits similar to automatic metal-cored welding often outperforming deposition rates of gas-shielded FCAW welding wire.

Out-of-position Welding: To obtain high deposition rates for out-of-position welding, small-diameter gas-shielded FCAW welding wire is preferred. Welding wires such as AWS E71T-1 or E71T-12 offer high deposition rates when utilised in out-of-position welding. The slag from these types of products is designed to support the puddle when welding in the vertical-up or overhead position.

Mechanical Properties: Because slagging agents along with other components are included in their cores, FCAW welding electrodes can attain good mechanical properties. FCAW welding electrodes can be utilised for numerous high-strength, low-alloy applications.

Postweld Operations: FCAW welding wire requires the most labour-intensive clean-up because of the slag it leaves behind on the weld. This slag needs to be removed in between welding passes in multiple-pass applications and prior to painting or coating.

Conclusion

All gas-shielded electrodes have unique mechanical properties, arc behaviour, and intended applications, but that does not automatically indicate there is a constraint to using the same type of electrode that is generally used. Options are available for any kind of welding project depending on the intricacies of the project.

After understanding the various benefits and drawbacks of each variety of welding wire, it is furthermore essential to understand that all electrodes are definitely not created equal. The most effective welding wires are those which offers consistent chemistry, wire diameter, feedability, and arc performance. Variations in the welding wire can result in reduced productivity, increased operating costs, and inconsistent welds.

Inconsistent wire diameter can cause feeding issues and may possibly require repeated procedural modifications within a spool or between spools. Inconsistent feedability results in wire chatter, diminished gun consumables life, inadequate starting, and wire burnback in the contact tip.

Reliability in welding wire consumables is essential to boosting productivity on the production line.