How to Weld Sheet Metal (Thin) with MIG Welder? Ultimate Guide

Welding thin metal sheets is an essential skill with tons of applications in various industries ranging from automotive to construction. It even has artistic applications. 

However, it is also one of the most challenging tasks, because a lot of problems can arise when you are welding thin metal sheets, especially for beginners. 

Mastering the art of MIG welding thin metal sheets can open up a lot of doors for a welder professionally. 

In this article, I will be sharing a detailed guide that will help you learn how to weld sheet metal with a MIG welder. I will also be discussing various challenges you will face during the process and insights on how to overcome them. 

So, without any further ado, let’s get right to it. 

Understanding the Challenges: Problems That Can Arise When MIG Welding Thin Metal Sheets

Welding thin metal sheets with a MIG welder can present you with certain challenges. Let’s discuss some of the most common of these challenges in detail:

Burn-Through Issues

This issue occurs when too much heat is applied to a specific area of the thin metal sheet. It will cause the sheet to melt in the heat-affected zone entirely which will create a hole or a weak spot. 

The underlying cause of this issue is the lower mass of the thin sheet which cannot dissipate the heat as effectively as a thicker sheet of metal. 

Beginners often face this issue, especially in the early stages as they are learning the process of MIG welding. 

Warping and Distortion

Warping and distortion occur when the heat generated from the welding process is too much for the metal surrounding the heat-affected zone (HAZ). 

The issue is common when you are welding large and flat panels of thin metal sheets. The problem can ruin the metal by distorting its shape. 

Also, when you are trying to create a precise shape or angle through welding, warping and distortion problems can arise. 

Lack of Fusion

Most of the time, to avoid the above two issues, beginners tend to increase the travel speed of their welding gun or reduce the heat input. 

This leads to an increased risk of insufficient fusion between the base material and the filler wire. The lack of fusion leads to weak joints which nullifies the very purpose of welding in the first place. 

These joints are easily breakable and won’t have any strength in them. Thus, they cannot be considered reliable.

Unique Problems of Specific Metals

Each metal is unique and may present you with different challenges when it comes to welding thin metal sheets. Mild steel or carbon steel is the easiest one to weld. 

All you have to do is keep a low amperage, increase the welding gun travel speed, and space out between your welds. 

However, stainless steel and aluminum aren’t that easy to weld, even as thick plates. So, when you are welding thin sheets of stainless steel or aluminum, you will have to face certain challenges. 

Stainless steel has low heat conductivity which means the heat will be too focused on the HAZ which can lead to warping or burn-through. Even heat sinks are not very effective with stainless steel. 

On the other hand, aluminum has good heat conduction but a low melting temperature, especially since the melting temperature of base metal is lower than that of the oxide layer on the surface. 

Hence, these two metals will present special challenges that can be addressed using special techniques. 

Essential Equipment and Settings for Thin Sheet Metal Welding

Now that we have established what problems you will be facing, let’s start with selecting the right equipment before moving on to the solutions for those problems. 

The equipment will help you through the process of MIG welding thin metal sheets. 

It is crucial to use the right equipment and settings to get efficient and reliable welds. 

Selecting the Right MIG Welder

First of all, you must select the right MIG welder. There are tons of those available in the market in all price ranges. 

You need to choose one that comes with precise control over wire feed speed and voltage settings. 

While thicker sheets can be welded using any MIG welder, you will need precise control for welding thinner sheets to maintain optimal heat input and minimize the risk of burn-through. 

A welder with a wire feed speed of 50-200 inches per minute is suitable enough for thin metal sheets, but the specific settings will depend on the actual thickness of the sheet you will be welding. 

Shielding Gas and Wire Type

Shielding gas also plays a crucial role in welding thin sheets. The most common shielding gas used for MIG welding is a mixture of 75% Argon and 25% CO₂.

This blend is ideal for welding thin metal sheets as it is both economical and provides a stable arc with minimum spatter. 

However, the exact composition of the gas will depend on the type of metal you are welding. 

You should not use 100% CO2 because the active gas is responsible for maximizing penetration which is not a good idea when working with thin metal sheets. 

Similarly, for the wire electrode, you have to select a smaller diameter size. You cannot weld a thin metal sheet with a thick wire electrode because that will increase the risk of burning through. 

Another thing to keep in mind is to avoid flux-cored wires because they have higher heat input and can burn through the thin metal sheet. 

Related: What Gas Does a MIG Welder Use? Role of Gas in MIG Welding

Adjusting the Welding Parameters

When welding thin sheets of metal, you will need lower amperage settings to ensure optimum and precise heat input. 

You have to maintain precise control to avoid any of the above-mentioned problems. You should start with a lower amperage setting and then increase it gradually as required. 

Additionally, you must also closely observe the quality of your weld and adjust accordingly. The process is known as fine-tuning or trial and error method to achieve perfection. 

Related: How Many Amps Does a MIG Welder Use? Ultimate Guide

Techniques for Effective Welding on Thin Metal Sheet

Mastering a proper welding technique is essential for achieving high-quality weld beads on thin metal sheets. 

Let’s discuss some of the techniques you can use to get efficient and reliable results. 

Tack Welding: Laying Foundation to Reliable MIG Welding Results

Tack welding is one of the most effective techniques that helps you in preventing burn-through and warping when working with thin metal sheets. 

In this method, you make a series of small and evenly spaced tack welds to hold the sheet together while minimizing heat input. 

With tack welds, you will lay a perfect foundation leading to successful and reliable welding.

Simply align the sheet metal pieces together to start tack welding. Before you begin, ensure that the edges are free of dirt, grease, and oxide layers. 

Once you have properly cleaned the edges, align the sheet pieces and start the tack welding process. 

Distribute the tack welds evenly along the seam and space them 1-2 inches apart. Make sure not to place consecutive tack welds directly next to each other and alternate their location along the seam. 

Also, you must avoid putting too much gap between the tacks. 

Also, make sure that the welds are small in size to minimize heat input. If you proceed in this way, you will be able to lay down the perfect foundation for successful welding. 

Maintaining consistent tasks is a difficult job. That’s why modern MIG welders come with a tack weld timer that helps you create repeatable tack welds with the same heat input and arc duration. 

So, if you have one of those welders, then your job will become a lot easier. However, if your MIG welder does not support a tack timer, then you may keep the arc lit for too long on some of the tack welds, and this may lead to warping. 

Push vs. Pull Technique

In the push technique, the welder will push the torch away from the weld pool which results in a flatter and wider bead, giving your seam a more uniform appearance. 

Compared to that, the pull technique involves dragging the welding gun away from the weld pool which forms a convex and narrow bead. 

For thin metal sheets, the push technique is highly recommended by professionals as it provides better heat input control and also prevents warping and burn-through problems. 

However, you are not totally restricted to the push method. You can use the pull technique in specific situations like when welding in tight spaces or when welding pieces in the overhead position. 

Controlling Travel Speed

Regulating the heat input is crucial in this welding scenario and one of the most effective ways to do that is by controlling the travel speed of your welding gun. 

A slower travel speed will generate excessive heat which will cause the electric arc to burn through, but a faster travel speed may not provide enough penetration and result in a lack of fusion or weaker welds. 

So, you will need to maintain a consistent travel speed that will be achieved through fine-tuning. Once you get to the right travel speed, you will have to maintain it. 

Weaving Technique

The weaving technique is also very effective when it comes to welding thin sheets of metal. Weaving or oscillating motion can help distribute the heat more evenly which solves the problem of heat dissipation. 

This technique can also help you fill uneven gaps that can be caused by misaligned metal sheets. 

However, you must keep in mind that over-weaving can lead to increased heat input. So, you have to use this technique carefully when working with thin metal sheets. 

Although it is not your first choice when welding thin sheets, it can prove to be very effective. 

Stitch Welding

Instead of welding a continuous seam, you can opt for alternating or stitch welding technique which is also very effective in MIG welding thin metal sheets. 

In this method, you will create a series of small, intermittent welds along the seam. Each weld bead will be allowed to cool down before you proceed to the next one.

You will have to alternate the location of the welds to distribute the heat evenly. 

Stitch welding is very helpful because welding a continuous seam can lead to excessive heat buildup and warping, which can be avoided by using this method. 

Backstepping

This is also an efficient technique to prevent common welding problems that arise when you are welding thin metal sheets. 

In backstepping, you will have to weld in the opposite direction of the overall seam, starting at the end of the joint and working your way back. 

The method is very helpful in allowing the heat to dissipate more effectively and reduce the risks of warping and distortion. 

Using a Heat Sink

Using a heat sink such as a copper or aluminum plate behind the weld area can help dissipate heat much more efficiently which can reduce the risk of warping, burn-through, and distortion. 

These are also known as backing or chill bars. They can be clamped to the back of the welding area or just placed beneath them when welding. 

The heat from the Heat Affected Zone will dissipate into the heat sink which will allow you to create strong and clean welds on the base metal. 

Related: How to Set Up a MIG Welder? —A Step-by-Step Guide

Frequently Asked Questions

Can you weld sheet metal with a MIG welder?

Yes, sheet metal with a thin gauge can be welded using a MIG welder. Although TIG welder is the top choice for welding thin sheets because they require higher precision of heat input, MIG welding is also very efficient. 

Is MIG good for sheet metal?

Yes, MIG welding is very good for welding sheet metal. It yields higher productivity and allows you to weld large metal sheets quickly. There are several techniques you can try to MIG weld thin metal sheets. 

What size MIG wire is best for sheet metal?

As a rule of thumb, you can remember not to use filler wire that is thicker than the base metal. For MIG welding thin gauge metal sheets, most commonly 0.023-inch or 0.024-inch wire is used. 

Can you MIG weld sheet metal without gas?

No, you cannot. Although some might argue that you can use Flux-Core wires for MIG welding thin gauge sheets, they have higher heat input which has risks of causing burn-through or warping. So, it is not recommended to use them.

Wrapping Up!

To sum it all up, you can weld thin gauge metal sheets using a MIG welder. Mastering this MIG welding technique is a valuable skill that can unlock a lot of new opportunities for a welding professional. 

The tasks do present some unique challenges but with the right tools and techniques, you will be able to overcome them and create strong and consistent welds on thin metal sheets. 

Remember, practice makes perfect. If you are facing any problems, that’s because your technique is still not perfect, and you need more practice. 

Got something on your mind? Drop it in the comments section below and I will get back to you as soon as I can.