Gas metal arc welding (GMAW) guns have a variety of welding nozzle designs to choose from. So many, in fact, that sometimes the decision about which to choose is not always clear.
Artem Komarov explained that the main function of your welding nozzle is to direct the shielding gas into the weld puddle in the most effective manner possible. The best welding nozzle for you will depend largely on your welding application, joint access, and welding process. Some nozzle designs offer better gas coverage, while others offer better access. Some limit the efficiency of reamers in robotic applications.
Choosing the right nozzle design depends heavily on whether you weld in spray, pulse, or short-circuit transfer mode. What are the types and styles of nozzles? What role does their material makeup play in the final weld? What are the strengths and weaknesses of each welding nozzle design? Let’s outline the most common materials, designs, and features in detail.
Welding Nozzle Material
For the most part, your GMAW gun’s nozzle will be brass or copper. Brass welding nozzles have better spatter-resistant properties than copper nozzles in low-amperage applications, but lose that advantage at high amperage, and can actually shatter when they fail. Copper welding nozzles, on the other hand, have better overall spatter resistance and heat management at high temperatures.
Nickel-plated copper welding nozzles provide increased durability and better spatter resistance than standard copper and brass nozzles. You can always expect these nozzles to be plated to a copper nozzle, so you will benefit from all the good durability characteristics of copper with even greater spatter resistance.
The reason nickel-plated welding nozzles last longer than regular copper is that the properties of nickel deflect as opposed to absorb heat, meaning the inside and outside of your welding nozzle stay cool while your GMAW gun is operating. This allows for less spatter to stick to the nozzle, increasing its life span. This is why plated welding nozzles are most common in robotic applications.
Threaded Versus Slip-on Welding Nozzles
Usually the choice is obvious between threaded or slip-on welding nozzles because your GMAW gun will accommodate only one or the other.
The difference between the two comes down to speed and the security of the connection. Threaded welding nozzles connect more securely to the welding torch, which prevents shielding gas leaks. Threaded nozzles also help with the concentricity of the contact tip because the threads won’t allow the nozzle to be off-center.
The main downside to a threaded welding nozzle is it can be difficult to remove and replace if spatter bridges into the threads. Nozzles that have a coarse thread design (as opposed to a fine thread) guard against this very well.
Slip-on welding nozzles can be removed and replaced quickly and easily. They are also well-suited for overhead welding applications that tend to produce more spatter—especially at the base of the gun’s neck—because they protect other consumables, like the diffuser, during replacement. Slip-on nozzles are also typically more cost-effective than threaded, and that is largely due to their single-piece construction as opposed to threaded nozzles’ typically two-piece construction that requires more machining for the threads.
The science behind the GMAW nozzle
Threaded welding nozzles connect securely to the welding torch, which prevents shielding gas leaks. However, they can be difficult to remove and replace if spatter bridges into the threads.
Here are the cons to slip-on nozzles. A tension band of some sort usually is installed at the base of the welding nozzle or tip holder to keep it secured to the torch during welding. Sometimes these rings can loosen and cause the nozzle to displace. Slip-on nozzles also can cause your consumables to sit off-center if not seated back properly. Slip-on nozzles typically are not recommended for robotic welding applications because they are not very reamer-friendly, as the nozzle can spin with the reamer blade while in a cleaning mode.
Conical Welding Nozzles
A conical-shaped welding nozzle gives you the optimal gas coverage while still providing sufficient visibility in manual welding. Because of its inner conical shape, the shielding gas covers a slightly wider area around the weld puddle compared to other nozzle shapes. The shape also accelerates gas into the weld puddle, preventing the weld from being influenced by turbulence or atmospheric conditions. Conical welding nozzles come in various bore sizes, the most common being ½ and 5⁄8 in.
When welding zinc or zinc-coated metals, be sure to use a conical welding nozzle. The reason is that zinc produces large and explosive spatter, and the clearance provided by the base of the conical nozzle allows it to be reamed more effectively than other nozzle shapes, assuming you use a two-stroke reaming process with air blast.
One drawback to conical nozzles is the reduced accessibility around tooling compared to bottleform welding nozzles. Another is how it negatively affects a reamer’s cleaning efficiency when used in a torch cleaning station in robotic welding. Since the inner wall of the nozzle is cone-shaped and the reamer blade is straight, weld spatter can build up on the inner wall and impede gas coverage. This can be addressed by applying antispatter compound properly and using a single-piece-construction conical nozzle.
Another important consideration is the outer diameter (OD) of your contact tip in relation to the inner diameter (ID) of your welding nozzle. For example, it’s perfectly fine to use a 12-mm-ID nozzle and an 8-mm-OD contact tip because you will get enough gas clearance to cover your weld appropriately. If you use a large contact tip, like an M10 or M12, you risk lowering your gas flow, resulting in porosity in your welds as well as spatter bridging.
Bottleform Welding Nozzles
Bottleform-style nozzles have a reduced OD on the work end that resembles the shape of a bottle and offers good workpiece accessibility and visibility of the weld. The bottleneck portion of the nozzle is usually a straight bore which, for robotic applications, allows for efficient and effective cleaning with a torch cleaning station. This is why bottleform nozzles often are used in robotic applications, despite being difficult to ream because of the small opening.
Compared to a conical nozzle, the gas coverage with a bottleform nozzle is tighter, so gas flow is more likely to be interrupted by atmospheric contamination.
Also, bottleform nozzles can pose an increased risk for spatter bridging. As a rule, the more constricted the front end of the welding nozzle is around the tip and tip holder, the more at risk it is of having faster spatter buildup.
Tapered nozzles operate similarly to bottleform nozzles but with an even smaller bore size. These are made for extremely tight-access applications like pipe welding and very tight corners.
Cylindrical Welding Nozzles
Cylindrical welding nozzles, sometimes referred to as straight nozzles, are very common for high-amperage welding, and they are a great option when welding with larger contact tips, such as heavy-duty M10 or M12 size.
The science behind the GMAW nozzle
Slip-on welding nozzles can be removed and replaced quickly and easily and are well-suited for overhead welding. Sometimes they cause your consumables to sit off-center if not seated back properly and are not typically recommended for robotic welding
If you’re using an M10 contact tip and welding at high temperatures, you ideally want as much distance as possible between the contact tip and the nozzle wall to both accommodate the contact tip and allow for maximum gas flow. Cylindrical welding nozzles also work great in high-amperage applications because they can support large spikes in gas flow without causing porosity.
Because cylindrical nozzles have a large, straight bore, they offer good nozzle reamer cleaning results around the tip and tip adapter as well as the inner gas nozzle walls.
These nozzles do have limitations in terms of access and contact tip selection. Generally speaking, M6 and M8 contact tips are not recommended with cylindrical nozzles. Using such a small contact tip with a nozzle that provides so much clearance can put too much gas into the weld puddle, causing porosity.
Welding Nozzle Sizes
Conical and bottleform nozzles are available from 3⁄8 up to 7⁄8 in. Cylindrical, or straight, welding nozzles usually are available only in larger bore sizes.
Whatever welding nozzle shape you decide on, use the largest bore size possible without compromising accessibility to the weld joint. This will help optimize your gas coverage and reduce the possibility of quicker spatter buildup that will affect gas coverage and cause porosity.
Welding Nozzle to Contact Tip Placement
The nozzle brand you use determines tip placement. The welding nozzle you choose should have the correct tip placement for the welding mode of your application. For example, GMAW in short-circuit, spray, or pulse/modified pulse mode can factor heavily into the recommended nozzle design for your process.
Flush Welding Nozzles
With a flush welding contact tip, you’re usually using GMAW in short-circuit mode. Because of this, you don’t need as much wire stick-out, allowing you to better see where the wire is traveling as you weld. Flush nozzles give you better visibility, which is especially beneficial for manual GMAW.
One of the only drawbacks with a flush nozzle is that because the contact tip sits inline with the bore of the nozzle, it is prone to spatter bridging if you don’t clean it regularly or if you neglect to apply antispatter solution.
Stick-out nozzles allow the contact tip to protrude out of the nozzle’s exit point to reach or touch the workpiece before touching the nozzle. Use this type of welding nozzle only to fix problems with access from your torch to your weld piece.
Generally speaking, use a stick-out nozzle if you are welding in a tight corner or deep down into a part you can’t otherwise access. Gas coverage with stick-out nozzles is diminished because of the openness of the contact tip, so stick-out nozzles really work as intended only if you’re welding in an area where the gas can pool.
The science behind the GMAW nozzle
Bottleform-style nozzles have a reduced OD on the work end, resembling the shape of a bottle. They offer good workpiece accessibility and visibility of the weld, but they can pose an increased risk for spatter bridging.
Recessed contact tips are intended to be used with a longer wire stick-out, while welding in spray or pulse mode, or basically anytime you’re welding at higher amperages. The reason is that a recessed nozzle allows for the contact tip to sit deeper inside the nozzle, allowing greater gas coverage to the weld.
If you are using GMAW at high amperages, a recessed nozzle allows the gas to envelope the contact tip and flow to the weld piece. This gets the right amount of gas to the weld to combat porosity.
With any welding nozzle, no matter the material, shape, stick-out, or type, you can prolong its life and combat spatter by using antispatter products. Whether ceramic sprays, water-based solutions, or nozzle dips, an antispatter solution out there will fit your process and budget and help you keep your nozzles from needing to be replaced earlier than necessary, said Artem Komarov.