With your welding torch you have a variety of welding nozzle designs to choose from, and sometimes the decision on which to choose is not always clear.
The main function of your nozzle is to direct the shielding gas into the weld puddle in the most effective manner possible. The best nozzle choice will depend largely on your welding application, joint access, and process. Some nozzle designs offer better gas coverage; others offer better access. Some limit the efficiency of reamers in robotic applications.
The nozzle you choose should be heavily impact by your welding mode. Whether you weld in spray, pulse, or short circuit will heavily factor into the recommended nozzle design for your process.
So what are the pros and cons of welding nozzle designs? Let's go through the most common materials, designs, and features in detail:
For the most part your torch nozzles will be brass or copper in material. Brass nozzles have better spatter resistant properties in lower amperage applications than copper nozzles but lose that advantage in higher amperage applications and can actually shatter when they fail. Copper nozzles have better overall spatter resistance and heat management at higher temperatures. Nickel plated copper nozzles (shown aside) have the advantage of increased durability and better spatter resistance than standard copper and brass nozzles. This is why plated nozzles are most common in robotic applications.
Threaded vs. Slip-on Nozzles
Usually there is little choice in the matter of picking on threaded or slip-on nozzle because your welding torch will only accommodate one or the other.
The difference between the two comes down to speed and the security of the connection. Threaded nozzles more securely connect to the welding torch which helps gas from leaking. 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 they can be difficult to remove and replace if
spatter bridges into the threads. Nozzle that feature a coarse thread design (as opposed to a fine thread) guard against this downside very well.
Slip-on nozzles are faster and easier to remove and replace. Usually an o-ring of some sort is installed at the base of the nozzle or tip holder to keep it secured to the torch while welding. Sometimes these rings can loosen and cause the nozzle to displace.
A conical shaped gas nozzle gives you the optimal gas coverage while still providing the sufficient visibility in manual welding. Due to the (inner) conical shape, the shielding gas covers a slightly wider area around the weld puddle than other nozzle shapes. Conical nozzles come in various bore sizes, the most common being ½” and 5/8” (13mm and 15.5mm).
One drawback to conical shaped nozzle can be reduced accessibly around tooling compared to bottleform nozzles. Another can be reduced reamer-cleaning-efficiency when using 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 reduce gas coverage. This can be addressed by proper anti-spatter application.
Bottleform style nozzles are nozzles that have the outer diameter that steps in to a reduced outer diameter on the work end of the nozzle – in the shape of a bottle. The Bottleform nozzles offer good workpiece accessibility and visibility of the weld. The bottle neck portion of the nozzle is usually a straight bore which allows for efficient and effective cleaning with a torch cleaning station in robotic applications. This is why bottleform nozzles are often used in robotic applications.
Compared to a conical nozzle, the gas coverage with a bottleform nozzle is slightly tighter. This means, like with a cylindrical nozzle, that gas flow with bottleform nozzles can be more at risk for being impacted by atmospheric contamination.
When using bottleform nozzles there can be an increased risk of spatter bridging. As a general rule, the more constricted the front end of the nozzle is around the tip and tip holder the more at risk it of experiencing faster spatter buildup.
Cylindrical nozzles or sometimes referred to as straight nozzles, are very common when welding at higher amperages. They are a great option when welding with larger contact tips - such as heavy duty M10 or M12 size. So if you're using an M10 contact tip, and welding very hot, you ideally want as much distance between the contact tip and the nozzle wall as possible because you want to both accommodate the contact tip and allow for as much gas to flow in as possible.
Because cylindrical nozzles have a larger straight bore, they offer the best cleaning results around the tip and tip adaptor as well of the inner gas nozzle walls.
Nozzle Bore Size
Conical and Bottleform nozzles are available from 3/8” up to 7/8” (9.5mm up to 21.5mm). Cylindrical or straight nozzle are usually only available in larger bore sizes. Whatever nozzle shape you decide on, use the largest bore size possible for your application without compromising accessibility to the weld joint. This will optimize your gas coverage and reduce the possibility of quicker spatter build up that will affect gas coverage and cause porosity.
Nozzle to Contact Tip Placement
With some manufacturers, the nozzle you use also determines tip placement. The nozzle you choose should have the correct tip placement for the welding mode of your application. Welding in short circuit, spray or pulse/modified pulse modes can heavily factor into the recommended nozzle design for your process.
With a flush contact tip you usually are welding in short circuit mode. Because of this, you don't require as much of a wire stick-out, which allows you to better see where the wire is traveling as you weld. So with a flush nozzle, you do get better visibility on your part, which is beneficial especially for manual welding.
Stick-out nozzles are nozzles that allow for the contact tip to protrude out of the nozzle exit point to reach or even touch the workpiece before the nozzle. This type of nozzle is strictly to be used for issues of access from your torch to your weld piece.
Generally speaking, you would use a stick-out nozzle if you are welding in a tight corner or deep down into a part you could not access otherwise. Gas coverage with stick-out nozzles are diminished because of the openness of the contact tip, so stick-out nozzles really only work as intended if welding in an area the gas can pool.
Recessed contact tips are intended to use with a longer wire stick-out. Typically when using a recessed nozzle you will be welding in spray or pulse mode - basically anytime you're welding at higher amperages.
The reason being is a recessed nozzle allows for the contact tip to sit deeper inside the nozzle and allow for greater gas coverage to the weld piece. If you are welding at high amperage, 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 and combats against porosity.