Shielding Gas For TIG Welding

Pure argon comes close as the go-to shielding gas in TIG welding, but it’s not always the optimal solution, certainly not for every situation. For reasons that should soon become apparent, gas selection is intelligently dictated by several factors. These include the type and gauge of metal being welded, plus any desired weld characteristics and application-specific equipment settings.

Besides argon, pure helium and mixtures of argon/helium are commonplace. These inert gasses, and blends thereof, are popularly selected on ferrous and non-ferrous applications. Expect to see their labels on cylinders of shielding gas on jobs that weld copper, mild or stainless steel, aluminum, titanium, etc.

There are also cylinders of argon that are mixed with elements that wouldn’t usually be utilized in TIG welding. These are applied in special circumstances, which will be covered later in this article.

What Is TIG Welding?

Not a great deal of time will be used on this section, not when there are other articles that cover the process in greater detail. TIG (Tungsten Inert Gas) welding is a type of arc welding that uses a non-consumable tungsten electrode to generate a highly controllable weld bead. Think about it, this is a super-hard metal with a melting point of approximately 3400°C. It’s not going to melt into the weld pool when an arc is struck on a Tooliom TIG TL-200T 2-in-1 welding machine. This is why the electrode is non-consumable, because of that impressively high melting point.

• TIG welded joints are generally strong and aesthetically pleasing
• Versatile: The process is used on multiple ferrous and non-ferrous metals
• Produces clean welds, so there’s less post-weld cleanup
• Super-controllable bead manipulation, which is perfect for thinner workpieces

In line with the welding method’s reputation for versatility, there are a handful of possible shielding gasses that can be utilized to make the work even more efficient. These shielding gasses, whether inert or blended with an active element, help to protect weld pools from atmospheric contamination, thus ensuring a clean and strong weld.

Source: https://sparcwelders.com/blogs/news/how-to-tig-weld-aluminum-the-right-way

Note: The term GTAW is used interchangeably with TIG welding. Gas Tungsten Arc Welding, as the acronym expands to, is the same thing as TIG welding.

Which Shielding Gas Is Best For TIG Welding?

As hinted at earlier, there’s no single answer. Depending on certain job variables, the type of metal being worked upon, its thickness, density and chemical properties, a matching cylinder is selected. The properties enhanced by the gas mix also target greater weld penetration and shaping, etc. Let’s take a closer look at those gasses and the process variables they affect.

Argon

Used in a cylinder on a GTAW project, pure argon provides superior protection from the air. It’s therefore the commonest gas used in TIG welding. Arc stability is a major benefit with argon, as are cleaner welds. Spotless welds with minimal spatter make it a clear choice for those that have a rep for blemish-free welding. Additionally, argon offers fairly good penetration and can be used for both thin and thick materials. That makes it a supremely versatile choice for hobbyists and pros, too. However, it may not be the best option for applications that require deeper penetration or faster welding speeds.

Of some importance in real-world situations, argon bottles are a costlier option than other shielding gasses, although they are the go-to gas for working on everything from stainless steel to aluminum. The gas is inert and imbued with a superior air displacing feature, but it’s not a particularly great conductor of heat. That, plus the fact that argon isn’t a good fit for specialized applications, leads us on to other shielding gas options.

Helium

Less commonly utilized as a single-gas choice for TIG welding project shielding, helium is nonetheless a practical option for certain, unique project applications. Referring back to argon’s thermal conductivity issues, helium delivers greater heat conductivity. That’s a feature that makes for deeper weld penetration and faster travel speeds. Weld puddles also fluidize faster when helium is present. Paradoxically, it’s easy for these benefits to become drawbacks, especially when an inexperienced welder is involved. Fast bead travel and deep penetrating welds can get out of hand when manipulated by a beginner.

Having said that, seasoned welders can use that deeper penetration feature to manipulate weld pools on thicker workpieces and produce stronger joints. Other factors to consider before ordering a cylinder of helium include atmospheric sensitivity and arc stability. For the first issue, helium is lighter than air, so it tends to float away on a breeze. Site contamination is the result. For the second concern, arc stability is paramount when working with super-fluid weld pools. If the arc isn’t stable, which is a possibility when utilizing helium, then control of the pool diminishes.

Argon-Helium

Next up on the gas shielding agenda for TIG welding enthusiasts, the above two inert gasses are mixed together in a way that leverages their most desirable properties. The welds produced under a protecting cloud of argon-helium are hotter, so they penetrate deeper. Better yet, the atmospheric sensitivity of helium is neutralized by the superior shielding attributes of argon.

This combination proves highly effective when dealing with thicker metals that require strong welds. It accelerates the heating of the weld pool, enhances its flowability, and enables deeper penetration. Argon serves as the primary component in these mixtures, buoyed by the addition of a small percentage of helium. Back in the real world, various ratios are employed to tailor the shielding gas \with specific weld characteristics, such as pool fluidity or bead depth penetration. Helium also plays a significant role in promoting weld bead fusion. In other words, when the appropriate gas ratio is selected to match the filler rod and base metal, fusion between the two becomes more efficient, resulting in a narrower and more focused weld. This, in turn, leads to an improvement in weld appearance, reduced spatter, and the production of a stronger, structurally sound joint.

Cost-effectiveness is an issue, however, as is the question over what ratio of the two inert elements should be selected. A balance needs to be struck between the desired weld characteristics and the cost of using helium as an additive.

Additive Elements and Their Benefits in Specialized TIG Welding Scenarios

Argon provides excellent atmospheric protection, moderate penetration and better than average pool fluidity. The gas envelope also infuses weld joints with fair to moderate aesthetical finishes. By adding helium, all of these factors receive a healthy boost. The appearance of the joint is cleaner as well.

Source: https://www.youtube.com/watch?v=yhDvRJ7HZ6E&t=5s

Suppose a higher heat input is recommended on a strong duplex steel support beam. This metal is enhanced with superior corrosion resistance, and it won’t react when in the presence of caustic chemicals. In this situation, words like ferrite and austenite come into play. Heat treatment processes are considered now, as is how the heat of a welding arc will alter the workpiece’s chemistry after it cools. This is the high end of industrial welding, where the smallest change in the ratio of a shielding gas cylinder could lead to disastrous consequences. Stepping away from argon-helium blends, hydrogen and nitrogen additives are often mixed in to counter undesirable metallurgical alterations in special metal alloys.

Hydrogen additives facilitate faster energy transfer, thus encouraging the formation of a super-fluidized weld puddle. Penetration is even deeper than when helium is utilized as a sole additive. It’s a good match, along with a corresponding filler, available in rod form, for thicker pieces of dense steel. Austenitics and nickel steels benefit from hydrogen mixes, as added to argon or argon-helium shielding gas cylinders.

Photo by @grumpyweld

On the other hand, hydrogen might not be the optimal solution when working with that aforementioned duplex steel alloy. In this case, hydrogen would be switched out for a shielding gas that instead employs nitrogen. Then again, with carbon steels, nitrogen will cause porosity problems, which could then lead to cracks. Of critical importance, there are so many metallurgical factors to consider and, oftentimes. so little time to get the job done properly, but that’s the nature of this profession. As a good rule of thumb, save argon-helium-nitrogen blends for duplex steel and high-alloy austenitic steels.

As evidenced by the above mix-and-matches, it’s never a good idea to randomly assign a shielding gas additive to an unknown metal. The composition of that alloy must be known so that weld defects, including those strength-weakening porosity defects, can be sidestepped. Perhaps that’s the difference between a beginner welder and a professional, enough awareness to weigh and evaluate every defect-causing factor before the arc trigger is ever pulled.

Source: https://fractory.com/welding-defects-types-causes-prevention/

The Importance of Gas Envelope Flow Characteristics

The various compositions of different shielding gasses for TIG welding have been explored in some detail. They affect arc stability, weld pool fluidity, penetration efficiency, and several other weld process factors when tungsten is employed as a non-consumable electrode.

Source: https://www.sciencedirect.com/science/article/pii/S2211379718308118

The metallurgical composition of various metals was added to the mix, as they’ll influence the manner in which the tungsten electrode arc interacts with the weld pool. Argon and helium were declared the two most common inert gasses, so it was only logical that gas suppliers would blend the two to create mixes that canceled out each other’s drawbacks. With all of this covered, is there anything left? Certainly, we’ve yet to talk about one other factor that can affect performance. As the sub-heading implies, gas flow rates are worthy of a mention. Ordinarily, we might reserve a line or two for this topic, but there are several flow sensitive parameters in motion now. For one thing, with helium or hydrogen as additives, the weld pool is super fluidized. Granted, that’s a good feature to have when seeking optimal penetration depth, but that pool is now susceptible to turbulence.

Cautious welders adjust the shielding gas flow rate so that it doesn’t cause pool turbulence. If left unattended, agitated puddles will trap gasses and cool into a porosity-ridden joint that lacks strength. Going too far in the opposite direction is just as undesirable. The shielding gas envelope breaks down now, atmospheric contaminants enter the puddle, and the weld oxidizes as heat interacts with the air. A windbreak of some type will help, but the more effective solution is to pay attention to the air regulator and any gauges on the cylinder feed. If in doubt, use a shielding gas flow chart to fine tune the flow rate.

Final Thoughts and Takeaways On Shielding Gas For TIG Welding

Welders can’t bluff their way through selecting a shielding gas selection. The closest someone could come to pulling off this objectionable feat would be by selecting a cylinder of pure argon as their haz shielding envelope. But even a highly configurable Tooliom TIG TL-200T 2-in-1 welding machine can only accomplish so much if the work should require a higher heat input level and deeper penetration.

TIG/Stick High Frequency Dual Voltage TL-200T 2 in 1 Welding Machine｜Tooliom

To get that deeper penetration on a thick alloy joint, know what alloy is being worked upon and know its chemical composition. Talk to the gas supplier, learn about argon-helium gas ratios, and experiment with different gas mixtures to find the one that provides the necessary heat input and penetration. If a hotter, deeper reaching weld pool is demanded for a tough job, use charts and explore the possibility of an additive mix, one that adds hydrogen or nitrogen to the argon-helium blend. Be aware, though, that these additives will react unfavorably with some alloys.

Source: https://foxthermal.com/applications/shield-gas-flow.php

Ultimately, there are only a handful of choices when selecting a shielding gas for a TIG welding project, but those choices compound when argon-helium ratios are added. Experimentation is an option, should time and resources permit, but there’s no replacement for experience. That same journeyman level seasoning is what’ll help a pro keep tabs on the gas regulator so that there’s no turbulence to complicate an already delicate welding scenario.

For beginners, specialized super-duplex alloys and exotic ferritic microcrystalline structures are less likely to be encountered, so a basic pure argon or argon-helium blend should be enough to accommodate most jobs. For anything more intricate, consult charts or talk over your options with a more experienced welder who’s already encountered and survived every conceivable TIG welding blunder as it relates to shielding gas problems.

Note: Consult industry guidelines and charts for information on the effects contributed by specific alloy compositions.

Shielding Gas For TIG Welding - FAQ

Q: 1. What are some common shielding gases used in TIG welding?

A: Common shielding gases used in TIG welding include pure argon, pure helium, mixtures of argon/helium, and argon blends with other elements.

Q: 2. Why is gas selection important in TIG welding?

A: Gas selection in TIG welding is crucial because different metals, thicknesses, and desired weld characteristics require specific shielding gases to achieve optimal results.

Q: 3. How does the combination of argon-helium gas work in TIG welding?

A: Argon-helium mixtures combine their properties to produce hotter welds with deeper penetration. Helium's sensitivity is neutralized by argon's superior shielding attributes, making it effective for thicker metals.