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Common TIG Welding Defects And How To Deal With Them
TIG welding, or Gas Tungsten Arc Welding, is one of the most complex welding methods, but high risks come with high rewards. TIG can yield some of the highest quality and visually appealing welds, especially on stainless steel and exotic or non-ferrous metals such as aluminum.
However, as a beginner, it will take you time and patience to get the most out of it. In your journey of unlocking the potential of GTAW, you will often encounter various issues and problems. That's why we decided to explain the common TIG welding defects and share a few tips on how to solve them.
TIG Welding Process
Photo by @welding_35 (IG)
What Are Welding Defects And How Do They Impact TIG Welding
Welding defects refer to imperfections or irregularities in the welded joint that can compromise the structural integrity or aesthetics of the weld. TIG is often specified to meet strict aesthetic, structural, or code/standard requirements, but as a fairly complex method, defects and issues often occur. It can take even the slight oversight in welding parameters, shielding gas coverage or technique to get holes, uneven and poor-looking beads, lack of fusion, etc.
The weld defects can occur on the surface of the weld bead or cause the interruption of the structural integrity of the weld in terms of mechanical, metallurgical, or physical characteristics. Typically, surface issues, such as uneven bead, affect weld bead appearance but can cause structural failure, just like weld discontinuities.
Even though the Welding Procedure Specification can allow a permissible range of extent to which there is no need for rework, TIG welding is strict. Compared to MIG welding, TIG is all about cleanliness and high quality, so even the small issues are unwanted.
Image of Clean, Precise TIG Welds
Source: https://www.youtube.com/watch?v=hhRjOa0v65U
Common TIG Welding Problems
TIG welding is a manual process, which means you will have to manually control the arc length, work angle, travel angle, welding speed, and how you feed the filler rod. Besides that, TIG welders are relatively complex machines that will allow you to control each part of the welding process.
TIG Welding Aluminum Process
Photo by @welding_35 (IG)
In the process of mastering and getting all together, you will encounter some of the common TIG welding issues, such as:
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Improper shielding gas coverage
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Wrong polarity
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Wrong filler metal type
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Lack of cleaning
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Improper fusion
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Improper heat input control
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Craters
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Tungsten inclusions
Each issue can create defects such as porosity, lack of fusion, uneven, convex, or concave welds, poor tie-in, discoloration, craters, or sugaring. None of these is a sign of a good and strong TIG weld, so let's see how and why they occur.
Image of Defective TIG Welds
Source: https://www.reddit.com/r/Welding/comments/12pkpd6
Improper Shielding Gas Coverage
Shielding gas plays a crucial role in protecting the TIG welds from atmospheric contaminations. Once heated, the tungsten electrode and filler metal are highly vulnerable to atmospheric gases such as oxygen, hydrogen, or nitrogen. Besides compromising the corrosion resistance of a stainless steel weld or an aluminum weld bead, they can also get trapped and create small holes known as porosity.
To avoid this, you must make sure you've selected the suitable shielding gas for TIG welding, adjust the gas flow rate, and make sure there are no leaks or damaged hoses and cylinders. Providing good shielding to your TIG welds is essential for achieving strong and defect-free welds, and poor gas coverage leads to various defects.
Shielding Gases for TIG/GTAW Welding with Different Metals
Source: https://www.perfectwelders.com/how-to-choose-the-best-welding-gas-for-tig-welding/
How To Solve Shield Gas Problems In TIG Welding
First, make sure you use high-purity inert shielding gas such as argon. Pure argon shielding gas (100% argon) is a go-to choice for most TIG welding on steel, stainless steel, aluminum, and other exotic or non-ferrous metals. Avoid using semi-reactive gases like CO2, as they can contaminate the tungsten electrode. You can add helium to increase the penetration and weld puddle fluidity on thicker metals.
The next step is ensuring a proper gas flow rate. Most of your hobby TIG welding will require rates of 15-20 CFH, but you can make some adjustments. If there is more draft, or when welding outdoors, you can increase the flow, but the bigger is not always the better. Excessive gas flow will create turbulent forces that will suck in the atmospheric contaminations.
If you've chosen the suitable gas shielding and adjusted the flow rate, but you still see the porosity or colors in your welds, you should troubleshoot gas contamination issues. The issues can be either gas leaks or shielding gas cylinder contamination. TIG is about cleanliness; even small leaks can pull air and contaminants into the shielding system.
How to Leak Check Welding Gas Cylinders
Source: https://www.youtube.com/watch?v=0q_L2hYhfyM
Wrong TIG Polarity
TIG welding is one of the few processes that can use both AC/DC welding, and sometimes, choosing the right polarity can be crucial for your welding project. By default, most TIG welding machines are set to DCEN (DC-), or Direct Current Electrode Negative polarity, as it provides the maximum penetration. The electrons flow from the negative side of the cycle, in this case, the electrode, into the positive side where base metal is clamped, providing enough penetration and good weld bead quality.
However, DC is not suitable for all applications. The issues arise once you are welding aluminum, which has an aluminum oxide layer that forms on top. This layer forms quickly when exposed to air, so you will need a cleaning action of DC+ polarity. But DCEP (electrode positive) lacks the required heat, so you can combine the best out of both by using alternating current (AC). Using the wrong polarity affects weld bead appearance and structural integrity, so it is crucial to get it right.
AC TIG Welding Aluminum Process
Photo by @kingstonwelding (TikTok)
How To Select The Right Polarity For TIG
As we noted, DC- is the default polarity for most TIG welding applications, and you can use it when welding steel or stainless steel. The welding amperage will produce the proper penetration required to fuse medium to thick steels. Due to a lack of heat, DC+ is rarely used in TIG, but you can sometimes use it to avoid burning through thin pieces. But things get tricky once you need to TIG weld aluminum.
TIG Welding Polarity
Source: https://blog.red-d-arc.com/
Always TIG weld aluminum with AC. In the alternating current, the electrons flow from the positive to negative side in one cycle. Once the current is on the negative side, you get the proper heat required to battle the thermal characteristics of the aluminum. Still, once the current switches to the positive side, you avoid overheating it and provide good cleaning action, which is essential for strong TIG aluminum welds.
Within the AC, you can set the balance or the time your current spends on the positive or negative side of the cycle. By default, the current will spend an equal amount of time on both sides, but you can tweak it. If you notice signs of brown oxidation flakes, increase the time spent on the positive side, but don't over-tune it since it can cause excessive balling.
Source: https://www.millerwelds.com/resources/article-library/understanding-ac-tig-balance-control
Wrong Filler Metal
Selecting the right type of filler metal is crucial for achieving the strongest TIG welds, but you should also be aware of their state and composition. AWS classification states the minimum amount of additives, but they can vary from manufacturer to manufacturer.
As a result, you can either fail to choose the correct size and type or even choose the right filler, but with improper composition. As a result, you can get uneven or poorly filled weld craters and poor-looking welds with compromised structural integrity. Always check the filler metal type, size, and composition before welding to deal with this issue.
Choose the Right Filler Metal for TIG Welding
Source: https://www.youtube.com/watch?v=jxUbOvj39Hc
Lack Of Cleaning
TIG welding is a clean process that requires proper weld preparation before welding. Unlike Stick welding, GTAW is not known for its performance when welding through dirt, rust, paint, or contamination. Each contaminant can compromise the integrity of the entire weld and non-consumable tungsten electrode, causing poor weld quality, porosity, and dirty or uneven welds.
The hard part about TIG is that each part of the process must be clean. As a result, prior to welding, you must clean base and filler metals, including mill scale on hot rolled mild steel, oxide on aluminum, or dirt and grease on filler metals. To do so, grind, brush, and wipe away all potential contaminants.
When preparing and cleaning aluminum, use a dedicated stainless steel brush. A regular steel brush can add carbon steel into the aluminum or stainless steel, creating a weak spot for corrosion or structural integrity of the weld. By spending more time cleaning the pieces before TIG welding, you avoid the risk of weld contamination and increase the chances of producing the highest quality and aesthetically pleasing weld.
Use a Dedicated Stainless Brush for Cleaning Aluminum
Source: https://www.hotrod.com/how-to/ctrp-0408-tig-welding/photos/
Lack Of Fusion In TIG Weld
A lack of fusing in TIG welds can occur due to improper weld preparation and a bad welding technique. Regarding weld preparation, poor fit-up on fillet weld is the leading cause of improper fusion on TIG welds. It will take time to master the art of fitting two pieces to achieve the best fusion into both parts of the joint.
However, lack of fusion in TIG welding is far more common during the period when new welders learn and perfect the TIG technique. Assuming that you adjusted the welding parameters according to the manufacturer's recommendations for the desired material thickness, lack of fusion occurs once you hold the torch too far away from the joint (increased arc length), go too fast, and improperly feed the filler rod.
Defects occur when the TIG torch is too far from the joint, such as lack of fusion.
Source: https://www.youtube.com/shorts/lcB2L3Kv9vY
How To Deal With Lack Of Fusion In TIG Welding
To prevent the lack of fusion in TIG welding, you must master the technique of keeping a consistent arc length, travel speed, and feeding rate. Welding is all about consistency, and the importance of it is most notable in TIG welding. MIG produces a forgiving arc, which makes it a beginner-friendly method, but TIG welding needs precision and fine-tuning.
Since lack of fusion occurs due to high arc length, proper arc length control is crucial. So always keep the torch close to the joint but not too close to cause excessive heat input. Additionally, don't travel too fast, as the lack of a focused arc cone can impact the penetration.
Proper Arc Length Control
Source: https://www.youtube.com/watch?v=b79fS4kkztY
Poor Heat Control In Stainless Steel Weld And Aluminum Weld Bead
Mild steel has favorable thermal characteristics, which allows it to reach desired temperatures and fuse pieces without too much trouble, which makes it easy to weld. However, materials such as stainless steel and aluminum require fine control over the heat input.
For example, aluminum has high thermal conductivity and a low melting point, resulting in a smaller workability window. As a result, you will need focused heat to ensure proper fusion, but excessive heat can cause burn-through. In contrast, excessive heat in stainless steel welding may lead to oxidation, resulting in discoloration.
Excessive heat can cause burn-through when TIG welding aluminum.
Source: https://www.youtube.com/watch?v=kwnlcohZUZM
Solving Poor Heat Input
To solve issues such as burn-through or discoloration in stainless steel welds caused by overheating, you must reduce the amperage and increase the travel speed. However, you don't want to go too fast or with low amps, as you can deal with a lack of penetration and fusion.
The best way to improve heat input control is to use a TIG welder with pulse options, such as YesWelder TIG 200 AC/DC. Pulsing controls heat input as the current bounces from high to low amperage.
TIG-200P-ACDC-PRO AC/DC Aluminum TIG Welder
Even though pulsing reduces heat input, you get enough heat to promote proper penetration and fusion, but the current then bounces back to low amps to avoid overheating and burning through the pieces. Heat control in a stainless steel figure will produce proper penetration but eliminate the colors that appear due to heat oxidation.
TIG welding is known for its heat control, and advanced machines will allow you to adjust the starting, ramp-up, and peak amps, as well as ramp-down and end amps. Once you master the art of controlling your TIG welder, you can control the heat through welding, which is crucial when welding metals with tricky thermal characteristics.
TIG Welding Titanium Process
Photo by @mikevandijck51 (TikTok)
Craters In TIG Weld
Controlling the weld pool and allowing it to fill the joint correctly is essential for achieving even and strong welds, but beginners often make a mistake when finishing the weld. Many welders instantly reduce the welding power or remove the filler rod at the end of the weld, which creates a defect known as weld craters.
The craters are holes at the end of the weld that appear due to the quick solidification of the weld puddle or a lack of filler metal. Besides their aesthetic, cavities are weak spots vulnerable to cracking and, eventually, welding failure.
Image of a Crater in TIG Welding
Source:https://www.youtube.com/watch?v=GNxcvuXK5aY&t=363s
How To Deal With Craters
To solve the issue of craters at the end of the weld, you will need to allow the filler rod to properly fill the end of the joint and reduce the heat at the end of the bead. Patience is crucial from start to end, so allow the filler material to fill the joint completely.
As noted, there are also welding equipment features that will help you do that. By adjusting the ramp down and end amps, you will prevent the excessive heat buildup at the end of the weld. That way, you can be sure the end of your weld is fused correctly without the risk of creating holes or cracks that can compromise the integrity of the weld.
Adjusting the ramp down and end amps prevents heat buildup.
Source: https://www.youtube.com/watch?v=GfylA4O96i4&t=2147s
Tungsten Inclusions
The tungsten electrode is non-consumable in TIG welding, so it doesn't melt during the process. However, some of the material from this electrode can be deposited into the molten puddle, leading to a defect known as tungsten inclusion. Inclusions occur once you touch the base metal with the electrode or due to high heat focused on the electrode.
The tungsten has different metallurgical, thermal, and metallic characteristics than base metal, so inclusions are potential weak spots in the weld. Even smaller amounts of tungsten can compromise the integrity of the TIG weld, and this problem is hard to detect with the bare eye.
What are Tungsten Inclusions
Source: https://engineersblog.net/what-is-tungsten-inclusions-weld-defect-how-to-determine/
How To Avoid Tungsten Inclusions
Even though tungsten has a melting point of 6,191.6°F, which is the highest among all metals, the temperature of the arc is, on average, 6,500 degrees. High heat can melt the tungsten, causing it to fuse into the joint, impacting the overall properties of the weld.
To avoid tungsten inclusion, avoid exposing the tungsten to high temperatures. You can do that by keeping your arc length consistent and avoiding using contaminated or damaged tungsten. Too much heat into the tungsten can cause it to break and fuse into the joint, and a common cause is the electrode being too close to the joint. Touching the base metal with tungsten can contaminate it, so you want to use a welder with a high-frequency start when cleanliness is crucial.
Avoid using contaminated or damaged tungsten.
Source: https://www.youtube.com/shorts/RkhkrEnyGpA
Final Thoughts
Mastering the art of TIG welding entails not only the precise execution of techniques but also a vigilant commitment to addressing and rectifying common defects. You must embrace a continuous learning process, whether dealing with surface imperfections like porosity and cracks or navigating internal challenges like lack of penetration and tungsten inclusion.
The key lies in understanding the root causes, implementing corrective measures, and fine-tuning welding parameters. Even though it might take time to master the world of TIG welding as a beginner, knowing what went wrong is crucial for further improvement.
🧐Common TIG Welding Defects And How To Deal With Them FAQ
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