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Tips For Welding Thin Metal
Welding medium stock is forgiving and beginner-friendly, but things get tricky once the thickness of the metal significantly increases or decreases. While welding both extraordinarily thick and thin metal presents unique challenges, many new welders need help dealing with thin gauges.
What makes welding thin metal so challenging is the fact there is a thin line between not getting a proper penetration and burning holes in the weld. Even small mistakes can break your entire project.
That's why we present crucial tips for welding thin metal, exploring the unique challenges of welding thin metal, and providing practical tips to help you overcome them. These tips are designed to guide and support you in your welding journey.
Why Is Welding Thin Metal So Challenging?
If you have ever tried welding metals below 5/64", it is very likely you've run into specific issues related to welding thin metal. You're not alone in this. The biggest problem with thin gauges, like 18 gauge or thinner, is the fact you need just the right amount of heat to produce complete penetration but not to burn the holes in the weld.
Burn-through, warping, distortion, and overfill are the most common defects encountered when welding thin metal. The primary cause of most issues with welding thin metal is poor heat control, which refers to the ability to maintain the correct temperature during the welding process.
- Burn-through: As the name states, burn-through occurs when your welds burn entirely through the weld metal. Seeing holes in your weld, either small ones from porosity or big ones caused by a burn-through, is never a sign of a good and robust weld. As with most other defects with a thin metal, burn-through is caused by the high heat of an arc, which melts everything away and burns the holes in the base metal.
- Warping: Extensive exposure to the heat can cause thin metals to warp and distort. Localized heating of the base metals creates local expansion and contractions, so the parts of the weld dish are inside between several stiffened points. Overcoming this issue requires tacking the pieces and using shorter welds to avoid heat buildup.
- Distortion: Uneven heating or cooling can create distortion, and this issue is also expected with thin metals. Expansions and contractions can cause your base metal to distort significantly from its original shape, and the joint may experience localized plastic deformation. Dealing with this defect also requires limiting the heat exposure and impact.
There are also some common welding defects, such as proud welds (overfill), poor weld appearance, porosity, or incomplete fusion. These are often caused by improper technique or preparation, and they can happen with any weld. However, most issues with thin metal are related to heat, so we will closely focus on solving problems with distortion and burn-through.
Welding Methods For Thin Metal
The four basic arc welding methods are MIG welding, TIG welding, Stick welding, and Flux Cored Arc Welding. Each has its ups and downs and favored applications, but when it comes to thin metal welding, welders typically turn to MIG welding and TIG welding.
Rest assured, these methods provide excellent heat control, which is essential when welding thin gauges. In some cases, you can even use Stick welding, but slag processes are generally not preferred due to their high heat. Let's explore what makes some processes a better choice for thin metals than others.
TIG Welding Thin Metal
Due to its exceptional heat control, many consider TIG welding a go-to method for thin steel. Most TIG welding machines provide a lower amperage output of 5 amps, allowing them to weld exceptionally thin gauges. There is even a form known as micro TIG welding, designed to work at less than five amps and with micro metals.
However, TIG welding is about more than just the low amperage output. This technique also provides excellent heat control by using a foot pedal or features such as pulse welding. Manually pumping the pedal can help you reduce the heat if you notice you are getting too hot during the weld.
Pulsed TIG welding is an automatic feature that makes TIG welding thin metal a breeze. You set the frequency, and the current oscillates between the high and low amperage during the weld. During the high amps, the arc melts the pieces and filler metals. During the low amps, the arc persists, but low heat promotes cooling and avoids heat buildup. That way, you reduce the overall heat input and thermal stress produced by rapid heating and cooling, which causes warping and distortion.
Additionally, TIG welding has a whole arsenal of equipment designed specifically to work at low amps and low heat, such as tungsten electrodes, small diameter fillers, larger cups for shielding gas support, etc. Although skill requirements are the highest among other welding methods, its advantages truly make TIG welding the king of sheet metal welding.
MIG Welding Thin Metals
Gas Metal Arc Welding, or MIG welding, is one of the most straightforward and, therefore, most popular welding methods among beginners. Its low skill requirements and moderate heat also make it a popular method for thin metals.
Although MIG doesn't have such a low-end amperage as a TIG, using a .023 MIG wire and softer shielding gas mixture with at least 5% or up to 25% of CO2 will enable you to MIG weld thin metals without a risk of defects. Adjustments in technique, such as pushing instead of pulling the weld, will limit the penetration, which is required to avoid a blowout.
Recent trends also brought the pulsing feature to MIG welding. The oscillation between background and peak amps provides heat control and prevents heat buildup, making MIG welding thin metal much more convenient.
Opting for a self-shielded wire for Flux-core welding is not preferred with thin metals. FCAW is known for its high penetration and heat input, so it can cause a lot of issues with thin sheets. Additionally, thinner flux-cored wires are rare. They typically come in a wire diameter greater than .030", so once again, they don't make a logical choice.
Stick Welding Thin Metal
Stick welding is an industry's favorite welding method due to its low cost and high penetration and depositions. It allows you to complete the job quickly and cheaply, which is essential in large-scale applications, but the lack of heat control doesn't make it a favorable thin metal welding option.
In general, Stick welding is not recommended for metals thinner than 1/8", so it is not a typical go-to method for thin sheets. High amperage, spatter, and depositions are not something you are looking for when dealing with a thin metal, so many look for alternatives.
However, you can get away with some minor repairs with Stick welding as long as the metal is not extremely thin. Welders use 1/16 inch electrodes and a lower output of 20-30 amps to stitch some thin pieces. In addition, specific electrodes such as E6013 produce shallow penetration, which can be favorable for thin metal. As long as you don't expect neat welds, you can get away with a limited amount of Stick welding on thin metals.
Essential Tips For Welding Thin Metals
Understanding the issues and choosing the suitable approach, including the welding method and equipment, significantly increases your chances of successfully welding thin metals. However, there are specific tips & and tricks that can substantially increase the odds, so let's dig in.
1. Use Skip or Stitch Welding Technique
Running a single, long bead across the entire welding joint in thin metals can cause severe heat buildup, leading to warping and distortion. So, instead of welding one bead right across the joint, you should use a series of short welds. This is known as skip welding or stitch welding, in which you lay down several shorter beads to avoid excessive heat buildup.
The primary goal of this technique is to let the base metal and previous weld cool before laying another bead. Things are even better if you are welding from opposite sides, allowing each side to cool down as you finish the previous welds.
2. Use Tack Welds
One of the best ways to avoid warping is to tack the pieces before welding. Unlike with thicker metals, where you use tacks to ensure even gaps, with thin metals, you should use multiple tacks across the joint to prevent warpage. Tacks are small, dot-like welds along the joint's length that will keep the base metal in place throughout the welding operation.
There are several features, such as a tack timer, which will help you make repetitive tacks across the joint. Inconsistent and poor tacks can have opposite results. Spending too much time on tack can burn through the pieces, so you should be careful. Once you have tacked the weld, you can run the intermittent welds to join everything up.
3. Select The Suitable Equipment
Trying to weld thin metals without proper accessories and consumables can yield highly inconsistent results, regardless of the welding process you choose.
If you are a MIG welding thin sheet, always opt for the smallest diameter wire. Anything thinner than 18 ga. will require a .023" wire and low amperage. ER70S-6 is a common MIG wire choice when welding thin steel; ER308 and ER308L are compatible with 304 stainless steel.
TIG welding thin sheets will require a smaller diameter, .020, .040, and 1/16-inch ceriated or thoriated tungsten. These electrodes support low-amp starts, which are required for thin metal, and keep the tungsten pointed when welding steel. ER70S-2 or silicon bronze rods will produce excellent results on thin sheets.
Regardless of the method you choose, we also recommend looking for a welder with pulsed feature. With its low amp output, pulse, and AC/DC options, YesWelder TIG200P AC/DC will cover most of your thin metal welding needs and metal types such as steel, stainless steel, and aluminum.
4. Adjust The Welding Technique
You will also have to adjust the technique to weld thin metal successfully. First of all, consider going faster than you usually would with medium-thickness steel. Going too slow will create heat buildup and eventually burn through the pieces. However, remember that going too fast can create incomplete fusion and penetration, so you want to be careful and moderate.
To avoid exposing larger areas of base metal to heat, avoid weaving with your torch. Simple stringer beads will create a narrow heat-affected zone (HAZ), which will prevent unnecessary heat buildup.
Another way to prevent burn-through is to push the MIG gun. Pushing directs the wire at the cooler edge of the base metal and puddle, avoiding unnecessary buildup. Meanwhile, pulling the MIG gun directs the wire toward the hotter portion of the puddle, which piles up the heat and can cause burn-through.
5. Provide Good Part Fit-up
Welding thin metals requires a tight fit-up. When welding pieces down to 20 or 24 ga., there should be no gap between them. In extremely thin pieces, even the most minor gaps create weak spots that don't absorb heat well and potentially cause a burn-through.
Welding without a gap usually doesn't require a filler rod since there is no gap that it needs to fill. This type of welding is known as autogenous welding or fusion welding. The heat of the arc melts both pieces, which then fuse, so you don't have to add excessive filler. This approach is widely used in micro-TIG applications or whenever the thickness drops below 20 gauge.
6. Use a Backing Bar
If you have issues with heat buildup, even if you have tried all the other tricks and tips, you can use a backing bar. A backing bar is a bar made of copper or aluminum, which you clamp on the back of your weldment.
Copper and aluminum have unique thermal properties which help them dissipate heat. Therefore, clamping them to your weldment will help you with heat dissipation and reduce the overall heat buildup. Additionally, they will promote cooling. That way, you avoid building up the thermal stress, and it allows you to get back to welding much quicker.
7. Think About Shielding Gas
Shielding gases such as helium or carbon dioxide (CO2) are known to produce better penetration and more heat. These properties are particularly favorable when welding medium and thick metals but unwanted when welding thin sheets.
The big issue behind this is that both CO2 and helium also help stabilize the arc and produce more consistent results, so you want them in your shielding gas mixture. To get the best out of both worlds and successfully weld thin metal, you will want at least 5% CO2 with MIG welding, but no more than 25%.
However, if you are MIG or TIG welding aluminum, you should always opt for pure argon. The surface of aluminum is vulnerable to reactive gases, so anything other than pure inert shielding can open the door to contamination.
8. Consider The Properties Of The Metal You Are Welding
Welding thin mild steel is typically much more forgiving compared to other common metals such as stainless steel and aluminum. To weld thin mild steel, provide good fit-up, reduce the amperage, and increase the speed, and you are likely to get favorable results.
However, stainless steel sheets can be significantly more challenging to weld. Stainless steel doesn't conduct or dissipate the heat, so most of it is contained in the HAZ.
By this time, you understand why heat retention is terrible for thin sheets. Additionally, heat buildup in stainless steel can also cause oxidation. Oxidation shows in the form of colors in the weld, and it can make stainless steel lose its corrosion-resistant properties, which many go for.
Aluminum also has a set of unique properties that make it one of the hardest metals to weld, and things get even more complicated when talking about thin sheets of aluminum.
Aluminum rapidly conducts heat, but it also has a low melting point, which means you'll need excellent heat control. Too little heat and you won't get a proper fusion, and too much amperage can burn holes and cause distortion and warping. That's why welding thin aluminum is considered one of the biggest challenges for many welders worldwide.
Final Thoughts
Mastering the art of welding thin metal requires precision, patience, and the proper techniques. By choosing the appropriate equipment, setting the correct parameters, and employing methods such as tack welding and seam stitching, you can achieve solid and clean welds.
Always ensure proper material preparation and maintain a steady hand to avoid burn-through. Practice and attention to detail are crucial to improving your skills. With these tips in mind, you can confidently tackle thin metal projects, achieving professional-quality results while minimizing common challenges.
🧐Tips For Welding Thin Metal FAQ
1. Why Is Welding Thin Metal So Challenging?
Welding thin metal poses challenges due to the need for exact heat control to prevent defects like burn-through, warping, and distortion. These issues arise from inadequate heat management, which can also lead to overfill, poor weld appearance, porosity, and incomplete fusion. The key to successful thin metal welding is addressing heat-related problems to ensure weld integrity and appearance.
2. Why TIG Welding is Suitable for Thin Metals?
TIG welding is considered ideal for thin metal for several key reasons:
- Precise Amperage Control: Allows for the low amperage necessary for thin materials.
- Excellent Heat Regulation: Foot pedal and pulse welding features enable fine-tuned heat management.
- Pulsed TIG Technique: Alternates current to control heat input and prevent distortion.
- Specialized Equipment: Utilizes tools like thin electrodes for precise, low-heat applications.
- High Precision: Offers the accuracy required for welding delicate thin metals.
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