The MIG/MAG welding process is very demanding and both man and material are pushed to their limits? – often even beyond. Therefore, it is all the more important to work with good tools, especially the welding torch with its wear parts. These parts are very close to the process and have to withstand heat and weld spatter for as long as possible. Especially the gas nozzle, which, in addition to its actual task, is often misused as a hammer.
The task of the gas nozzle is to calm the gas flow and to lead it evenly and laminarly into the process in order to ensure good shielding gas coverage of the welding area and to dissipate heat as quickly as possible. The gas nozzle is the part of a welding torch in the front area of the torch head that is the first to come into contact with the heat from the process and flying weld spatter. Because the MIG/MAG welding process is an arc process, desired or undesired short circuits always produce more or less weld spatter, which get stuck both inside and outside the gas nozzle. Specially coated gas nozzles for MIG/MAG torches can considerably limit this unwanted effect and thus ensure a longer lifetime of the gas nozzle.
The main body of more or less every gas nozzle for MAG or MIG welding is made of copper – or a copper alloy. Copper is an excellent heat conductor, can be processed easily and is nevertheless very robust. The property of good thermal conductivity is important because heat from the process is inevitably absorbed in the gas nozzle and should be dissipated as quickly as possible, which in turn extends the service life of all wear parts. The cooler the gas nozzle, the lower the spatter adhesion, since these cannot even stick to the nozzle, can be easily removed or do not penetrate as deeply into the material of the gas nozzle body. The functionality, service life and ease of maintenance of the gas nozzle are increased in this way.
There are gas nozzles made of pure copper resp. brass on the one hand, but also with coatings such as nickel on the other. The nickel coating acts like a separating layer and makes it difficult for weld spatter to burn in or stick on. In addition, nickel has the property of reflecting – not only light, but also heat – which is good for less heat absorption from the welding process. There are even high-gloss nickel-plated gas nozzles, as we use them in our ABIMIG® welding torches.
As already mentioned, it cannot be avoided at all that particles or metal spatter sticks onto and in the gas nozzle during the welding process. Gas nozzles must be cleaned regularly so that they can continue to guarantee a good laminar gas flow. The use of special cleaning pliers is recommended here for this purpose.
However, if burnt-on weld spatter builds up and cannot be removed, it is time to replace the gas nozzle. In case welding is continued despite the stuck particles, interference contours in the flow path of the shielding gas would occur and a laminar gas flow is no longer given. In a gas nozzle with accumulations of particles, the gas is dammed up in front of the foreign bodies and a whirl forms behind it. This turbulence can cause air to be sucked in from the atmosphere as if in a kind of re-entrainment effect and thus contaminate the gas. The result is shown as pore formation and black spots on and next to the weld seam due to oxidation.The coating material of a gas nozzle therefore decides how quickly weld spatter builds up onto and in the gas nozzle or how well they prevent weld spatter from sticking due to their own properties. Regardless of this, a well-adjusted, largely spatter-free welding process creates the basis for a long service life of the wear parts.
In addition, you can prepare your gas nozzles before welding so that they are protected against burning in: for example spraying with ceramic spray or dipping in anti-spatter paste before welding coats the surface of the nozzle and makes weld spatter burn in less quickly. Separating sprays form a separating layer on the gas nozzle, thus hot particles do not adhere as quickly and can be easily removed there.
MB series torches have a slip-on gas nozzle that is pushed directly onto the torch head, the so-called gas nozzle seat. Slip-on gas nozzles, which have a larger contact surface for heat dissipation compared to screw-on gas nozzles, are also equipped with a retaining ring that holds the gas nozzle in place as soon as it is pushed onto the gas nozzle seat. However, if you have changed the gas nozzle on a welding torch many times, the material is also removed from the gas nozzle seat. A retaining ring ensures that the gas nozzle still holds in place.
Of course, a MIG/MAG gas nozzle must fit just as securely when warm as when cold. The retaining ring or a retaining spring help to bridge the differences by expanding or contracting the material safely. As a result, the gas nozzle always sits securely on the gas nozzle seat.
Every weld has its own individual requirements for the shape of a gas nozzle. Some tasks require good accessibility to the component, while others require broad gas coverage. And quite often, compromises have to be made.
The wider the front end of the gas nozzle – this is referred to as nominal width (NW) – the wider the gas dome. ABICOR BINZEL offers gas nozzles in nominal widths of 7 mm (narrow gap set for MB 401/501) to 21 mm (cylindrical for ABIMIG®), although there are still other conical variants between these types depending on the torch type. If access to the workpiece is very poor or if the seam to be welded is in a narrow gap or is even angled, so-called narrow-gap gas nozzles or those with a front end bent at 45 degrees offer valuable help. More on that in a moment.
If you choose the wrong gas nozzle, there is a high risk that the shielding gas coverage will not be sufficient. The following images visualize the gas flow that can be recorded with the so-called Schlieren interferometry in the ABICOR BINZEL ARCLab. In the in-house research and development department, the gas flow is visualised and analysed with special cameras while the welding process is running.
The top row of the images shows an unsuitable gas nozzle with trumpet shape – left without an arc, right with an arc – which can be seen from the turbulence in the shielding gas. This comparison also clearly shows that the arc has a decisive influence on the flow behavior. The bottom row of the figures shows a cylindrical gas nozzle that ensures a constant laminar flow of shielding gas in the welding process and thus optimal gas coverage.
How good the shielding gas cover actually is can be seen by measuring the oxygen content below the gas nozzle, which can also be checked in the ABICOR BINZEL ARCLab.
The results of the oxygen measurement show the differences in the quality of the protective gas coverage for the two gas nozzle shapes.
Every freely accessible welding point is good for handling, but there are also seams to be welded with complex accessibility. If the component is difficult to access, you can select a gas nozzle shape to achieve a good quality weld also in this case. An example of this is welding of so-called T-joints, where welding has to be done »in a corner«. Materials that are sensitive to oxidation – such as stainless steel or aluminum – must be welded with a gas nozzle that provides the widest possible shielding gas coverage.
There is a selection of specialized gas nozzles for practically every special challenge in accessibility to the component:
A conical gas nozzle narrows towards the front end and is well suited for welding T-joints, for example. Strongly conical gas nozzles offer even more space at the front end and still allow sufficient shielding gas to flow through.
Their shape ensures a rather wide gas coverage and is therefore the ideal choice for welding aluminum or stainless steel – provided that accessibility allows it. If the gas coverage is insufficient with these metals, this leads to unwanted temper colour and other oxidation. Removing these oxidations is an expensive and therefore unnecessary operation. In the worst case, the workpiece is scrapped. You can prevent this with the right choice of gas nozzle.
Gas nozzles, also known as »Heavy Duty« (HD), have a thicker wall, which makes them ideal for welding applications where a lot of heat is generated. For example when welding in the high ampere range or when the workpiece has to be preheated so that the weld seam does not form cracks. Heavy gas nozzles absorb more heat and dissipate it again just as well. Heavy-duty gas nozzles are available for the types MB EVO/MB EVO PRO 25, 401, 501 and ABIMIG® W T 540.
As the name suggests, the high-performance gas nozzle is suitable for high-ampere welding and has a comparatively long service life despite the heavy load. It is not a particular shape that is decisive here, but the structure of the gas nozzle body. The gas nozzles used in the ABIMIG® torch series are provided with an insulating compound in the gas nozzle body. This ensures that no heat is emitted into the gas nozzle seat, which makes the welding torch more resistant overall.
In addition to the standard gas nozzles mentioned above, there are also those for very special applications such as welding T-joints (also called fillet welds), in a narrow gap or where very much heat is generated when welding with high currents or in pulse processes. These belong to the category of special gas nozzles. Each one of them fulfills very special requirements that make them real experts in their field and are of great help once standard nozzles reach their limits:
This bottle-shaped gas nozzle enables both good accessibility and a good view of the workpiece. Finally, the shape of the gas nozzle in combination with the contact tip, which of course also has an influence on the gas flow rate, still has to let through enough shielding gas to weld a proper seam.
For welding T-joints resp. fillet welds the 45 degree bent gas nozzle is ideally suited. With this special gas nozzle you can weld very well in corners and use a straight torch neck, which makes it possible, for example to weld a fillet weld in a narrow gap. A complete set of wear parts including a curved contact tip is required for this type of gas nozzle.
With its extreme bottle shape, this special gas nozzle makes it possible to enter very narrow gaps that cannot be reached with a standard gas nozzle. Narrow-gap gas nozzles are mainly used where thick sheets between approx. 30 to 50 mm thickness are welded and both a neat root and good intermediate layers have to be welded. Examples are shipbuilding, steel construction, plant construction and the thick sheet metal sector in general. With narrow-gap gas nozzles, it is essential to note: The gas nozzle has to be cleaned more frequently, as it clogs comparatively quickly.
This double-walled gas nozzle has its own coolant flow and return connection and can be supplied with coolant independently of the internal cooling of the welding torch. In extreme situations with maximum welding power, where other gas nozzles exceed their limit in terms of heat dissipation, this extra-cooled gas nozzle ensures a cool front end of the welding torch. This can be very helpful with preheated components, among other things.
No matter what welding tasks you have to cope with: only use gas nozzles of the best quality. Of course, the same applies to all other wearing parts for welding. People often save money, use poorly processed material, reduce wall thicknesses and then get annoyed when the result is not good and rejects pile up.
When we talk to users about gas nozzles and list which types of gas nozzles ABICOR BINZEL has on offer in addition to the standard repertoire, we often hear statements such as: "If I had known that, we would have approached the problem very differently!".
Talk to your dealer or the manufacturer directly if you have any questions about special welding applications.
With this in mind … happy welding!