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Most welders are familiar with the traditional components of a TIG torch: the collet, collet body, nozzle, back cap and tungsten. However, many may not have heard of the gas lens before. Gas lenses tend to cost more than other components and are usually reserved for use on critical applications. In this article, we will explore the benefits of using a gas lens and discuss its applications.
What is a Gas Lens?
A gas lens will replace the collet body in a TIG torch. Together with the collet, the gas lens will hold the tungsten in place to create the electrical contact needed for good electrical conductivity.
Usually, a gas lens is composed of a copper/brass body with layered mesh screens of steel/stainless steel. This design helps to distribute the shielding gas uniformly around the tungsten and along the weld puddle. There is also a more durable but expensive type of gas lens. This one features an engineered porous filter media that provides even better laminar gas flow.
The Benefits of Using a Gas Lens
The main purpose of the gas lens is to reduce shielding gas turbulence and provide a longer, undisturbed laminar flow of the gas to the weld puddle. This is especially useful when welding materials that are highly reactive to atmospheric contaminants, such as stainless steel, titanium and aluminium. Poor gas coverage on these alloys can result in porosity and material degradation, which may affect the strength of the weld. Even for the welding of steel, a gas lens can provide a more consistent welding performance because of the improved shielding gas coverage.
In addition, because of the laminar flow created by the gas lens, the welder may move the nozzle further away from the joint and extend the tungsten electrode past the nozzle by one inch. This provides a better visibility of the joint and the welding arc, and the welder can confidently produce a high-quality weld in critical applications and hard-to-reach areas such as TKY joints.
Lastly, with all things being equal, the laminar flow provided by the screens in the gas lens will create a wider and more uniform gas coverage area without an increase in shielding gas consumption.
Selecting the Most Suitable Gas Lens
Before choosing a gas lens, you will first need to identify the amperage requirements for the job, the tungsten size to be used, along with the joint configuration and accessibility of the joint. You will also need to know the model of the TIG torch you are currently using.
There are generally three types of gas lenses. Standard, Extra-Large and Stubby. A standard gas lens is sufficient for basic, lower amperage TIG applications. Extra Large gas lenses will provide improved gas coverage on specialty alloys that tend to react to atmospheric contaminants. For hard-to-reach applications, the Extra-Large gas lens will also allow for greater tungsten stickout for extra visibility of the weld puddle and increased access to the weld joint. A Stubby gas lens features the same orifice as the Extra-Large gas lens but are much shorter in height. The smaller torch profile not only increases operator comfort by reducing the overall weight of the torch, but it also allows for enhanced access to confined joints.
If an application calls for the use of a Stubby gas lens, it is recommended to combine it with a short back cap to give the welder a better torch balance and control.
Installing the Gas Lens
When installing a gas lens to an existing torch, always remember to replace the existing nozzle with a larger nozzle. In addition, you will need to purchase an additional transition insulator. This insulator seals the area where the nozzle screws into the gas lens. Without this, atmospheric air will enter into the shielding gas stream and cause porosities and other weld defects.
A gas lens is a consumable, as such, they will need to be replaced from time to time. Gas lenses can become contaminated with weld spatter, leading to blockages in shielding gas flow and negatively affecting the quality of the weld. Always perform visual inspection of the gas lens to observe for spatter or wear and tear before starting your welding operations.
Final Comments
The use of gas lenses will not be suitable for every TIG welding application. However, if welders are encountering applications that require extra gas coverage or better accessibility to hard-to-reach joints, then it will be best to consult a trusted welding supplier to understand if a gas lens could be a potential solution.