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How to Weld Aluminum with a MIG Welder?—A Guide

Last updated on May 25th, 2023

Aluminum is a versatile and lightweight metal that has gained immense popularity due to its wide range of applications in various industries.

One of the most widely used methods for welding aluminum is MIG welding. MIG welder opens a world of possibilities in aluminum welding.

You should know that welding aluminum can present some challenges. But if you have the right equipment, MIG welding aluminum is not that difficult.

So, all you need is the right set of instructions and that’s where I come in. In this article, I will be delving into the intricacies of aluminum welding with a MIG welder.

Keep on reading to find out the expert tips and tricks that can help you become an efficient aluminum welder.



Understanding the Characteristics of Aluminum

Aluminum has unique and exceptional properties that really set it apart from the rest of the metals. It is lightweight, corrosion-resistant, and offers excellent electrical and thermal conductivity.

Because of these reasons, aluminum is highly desirable for a wide range of applications in various industries.

Understanding the characteristics of aluminum is a must if you want to become efficient in its welding technique.

First of all, this metal is lightweight but durable at the same time. It has a low density which means you can use it in places where weight reduction is required but because of its reliable strength, you won’t be sacrificing any durability.

Adding to this, aluminum is available in the form of various alloys, each of which has its own unique properties and applications. This makes aluminum a versatile metal with tons of applications.

Welding Challenges of Aluminum

Despite having such amazing properties, the metal still presents you with some difficulties when it comes to welding. That’s the reason you can’t just use any method for welding aluminum.

The metal has high thermal conductivity which means there will be rapid heat dissipation. Hence, it is very challenging to achieve proper fusion during the weld.

Moreover, this metal reacts with oxygen in the air, which forms a stubborn oxide layer on the surface which hinders welding. Fighting this oxide layer is very difficult for a common welder.

MIG welding helps a welder fight these challenges and enhance the welding characteristics of the metal to their fullest.

Welding Aluminum with a MIG Welder: A Step-by-Step Guide

Welding aluminum with a MIG welder is very efficient and also an easy-to-learn process.

Just follow our step-by-step guide below and you will get everything right:

Step 1: Setting Up Workspace

First of all, you need to set up a proper conducive environment for welding. Proper ventilation is a must because there will be fumes from welding that can be harmful if inhaled.

Also, you must always wear personal protective equipment to protect yourself from potential harm. Welding is a very dangerous process and if you do not protect yourself the right way, you will be at risk of several potential health hazards.

You must keep in mind that aluminum welding requires proper grounding to maintain electrical stability. So, you must ensure that your welding setup has a strong ground connection.

Step 2: Essential Tools and Welding Materials

Once you have got the right place, next comes the equipment. You must equip yourself with appropriate tools for MIG welding aluminum.

The first thing you should get is a reliable MIG welder that is suitable for aluminum welding. Ensure that the machine has proper voltage, amperage, and wire speed settings that are compatible with your welding requirements.

If the MIG welder doesn’t come with a welding gun, then you will need to purchase a dedicated one that goes with it.

Besides the basic apparatus, you will also need aluminum-specific consumables and filler materials that would go with the welding process.

You will need to use the aluminum wire electrode which will also act as the filler wire. The diameter of the wire will depend on the specifics of the project.

Step 3: Adjusting the Welding Parameters

This is the most important step. Once you have all the equipment in place, you will need to adjust the welding parameters.

Properly configuring your MIG welder is crucial to achieving desired results with aluminum welding.

You will need to adjust the voltage, amperage, and wire speed on the welding machine. The settings will depend on the thickness of the metal sheet and the desired welding properties.

Once you start with the welding process, you can fine-tune the settings to get to the optimal settings that are best suited for the project. Practice is the key to achieving the best settings.

Step 4: Shielding Gas and Gas Flow

Choosing the right shielding gas and the gas flow rate is also critical when it comes to welding aluminum.

Pure argon or a helium-argon mix is commonly used when it comes to welding aluminum.

When you are welding thin sheets of aluminum, you will have to use pure argon because deeper penetration is not required, and using any mixture of argon will cause a burn-through.

However, for thicker aluminum sheets like ½ inch or more, you can use a mixture of helium and argon.

Helium is also an inert gas that provides you with deeper penetration and higher heat input which ensures better fusion with thicker sheets of aluminum.

When welding aluminum, the generally recommended gas flow rate is 20 to 30 cubic feet per hour (CFH).

Step 5: Cleaning the Workpiece

Before you start the welding process, you will have to clean the aluminum service to remove any dirt, oil, or oxide layer on it.

Although the oxide layer will form as soon as the aluminum comes back in contact with the oxygen, which is inevitable, you can still focus on removing the dirt and debris.

Cleaning the oxide layer is mandatory when it comes to welding aluminum. You must know that the oxide layer on aluminum has almost twice the melting temperature of that of aluminum itself.

So, if you don’t deal with the issue, the welding process will straight-on lead to a burn-through.

You can use a steel brush and acetone to clean the surface of the workpiece. You can also choose to use a dedicated aluminum cleaner if it fits your budget.

If you are using a power wire brush for the cleaning process, then you should keep the rpms and pressure low to avoid smearing the surface of the metal.

Smearing on the surface can trap oxides and impurities which will contaminate the weld.

Step 6: Proper Welding Technique

Now you must start the welding process. Maintain a suitable gun angle and travel speed to get consistent welds.

The angle should be between 10-15 degrees in the direction of the travel. You will get the welding speed right with a bit of practice.

Maintaining a steady welding speed is crucial to achieving proper heat distribution in the weld pool and also for proper penetration and fusion.

A good rule of thumb is to use the same voltage that you would have used with mild steel but double your travel speed while welding aluminum.

Another important aspect that should be focused on in the technique is whether you should push or pull while welding aluminum.

So, remember, when welding aluminum you should always use the push welding direction.

This will ensure that the shielding gas covers the weld pool completely to leave a flatter and wider bead with less penetration to avoid warping or a burn-through.

Pulling with aluminum welds leaves much more spatter and weld deposit leading to dirty welds. That’s probably because of partial gas coverage.

Step 7: Dealing with Distortion

As I have mentioned above, aluminum has high thermal conductivity which means it is prone to distortion.

There are various techniques that can be implemented to deal with this issue. You can use intermittent welding, backstepping, and clamping to minimize distortion and achieve the desired results.

Related: How to Use a MIG Welder?—Ultimate Guide & Expert Tips

Troubleshooting Common Aluminum Welding Issues

Just like any other type of welding, you can also run into some problems while welding aluminum.

Let’s take a closer look at some of the common problems and how you can resolve them.

Porosity and Cracking

These are two of the most common problems faced during MIG welding aluminum. Understanding the underlying causes of these problems is crucial to ensure their prevention.

Moisture and contamination in the weld pool can lead to porosity. So, if the environment where you are welding is moist or if you have not cleaned the workpiece properly before welding, it might be the cause of the issue.

Adding to this, excessive heat input during the welding process or improper joint preparation can lead to cracking.

So, you must ensure that there is no moisture in the environment, clean the workpiece properly to free it from any contaminants like dust, oil, and grease, and also ensure proper adjustment of welding parameters and techniques.

Following these guidelines will help you avoid porosity and cracking issues.

Burn-Through and Warping

When you are welding thin-gauge aluminum, burn-through, and warping are major concerns. Welding thinner sheets is difficult as slight problems in technique or settings can lead to these issues.

Hence, employing preventive measures and implementing correcting techniques is the way to get rid of these issues.

A burn-through usually happens because of two reasons, either you are moving your gun too slowly along the joint or the input temperature is too high.

Controlling heat input is crucial when welding thin sheets of aluminum. You must adjust the welding parameters to the specific requirements of the task to ensure that there is no burn-through.

Warping on the other hand happens because of unequal contraction and expansion of the welded aluminum. To avoid that, you can use fixtures, clamps, and heat sinks.

These will help you control warping and get the desired shape of the weld.

Dirty Welds

Sometimes you get dirty welds while welding aluminum. That is probably because of a mistake in the welding process or cleaning methods.

So, to avoid this issue there are several things you need to take into account.

As I mentioned above, using a pull or drag technique while welding aluminum doesn’t provide full coverage to the weld pool which can lead to dirty welds.

Hence, you must use a push angle while welding aluminum.

Increase the voltage to get into the spray transfer method which is also a good way to avoid this issue.

You must use proper base metal cleaning techniques to ensure that there are no contaminants on the surface of the workpiece before you start the welding process.

Well, if you have done all of that and are still getting the issue then perhaps you should check for proper shielding gas and alloy type.

Related: How Does a MIG Welder Works? Inside the Machine

Finishing and Polishing Aluminum Welds in MIG Welding

Unlike TIG welding, MIG welding doesn’t give you 100% aesthetically appealing welds. There will be spatter and a need for proper cleaning and grinding.

So, you must clean and polish the weld after completion to enhance its appearance as well as integrity.

Grinding and Cleaning

Grinding and cleaning is a pretty straightforward process, but you have to get the equipment right for the best results.

Use a dedicated aluminum grinding wheel or a flap disc to remove any excess weld material that has been deposited near the joint. This step is used to smoothen the weld seam.

However, you must ensure that you exercise extreme caution and avoid overheating the aluminum piece which can lead to distortion.

You must also clean the weld seam thoroughly to remove any and all residual oxidation or flux. You can do this through multiple cleaning methods.

This will help you prepare the surface for proper finishing.

Achieving a Professional Finish

Last but not least, you can enhance the aesthetic beauty as well as durability of your weld with proper finishing options.

You can use fine-grit sandpaper or polishing compounds to achieve a smooth and polished finish. Using these tools, you will be able to remove the visible weld pines and create a visually appealing result.

If you use the method and material properly, you will be able to make it so that the pieces were never welded and always existed as one.

You should consider anodizing or applying a protective coating to further enhance the durability and corrosion resistance of your aluminum weld.

This will get you an additional layer of protection and also improve the long-lasting ability of your weld.

Frequently Asked Questions

What process should you use for MIG welding aluminum?

Normally, the most used method for MIG welding is short-circuit transfer but when MIG welding aluminum, you should switch to spray transfer. It ensures the smooth transfer of molten metal droplets to the weld pool.

Is MIG welding aluminum safe?

Yes, MIG welding is one of the common methods that is used for welding aluminum. Not only is it a safe, reliable, and fast method for welding this metal but also results in high productivity and good-quality welds.

What is better for welding aluminum, MIG, or TIG?

TIG welding is very efficient when used for welding thin sheets of aluminum. It provides you with cleaner, stronger, and more aesthetically pleasing welds. But it is too slow a process and also more expensive. MIG welding is faster and less expensive.

Why am I getting dirty welds while MIG is welding aluminum?

There can be a lot of reasons. You might not have cleaned the weld pool properly, or you might be using the wrong direction while moving the welding gun. Read the above guide to learn how to troubleshoot this issue.

What is the right gas for MIG welding aluminum?

Argon is the best gas to be used when you are MIG welding aluminum. 100% pure argon is used for welding thin sheets of aluminum. However, for aluminum thicker than ½ inch, you will need more penetration power, so a mixture of Helium-Argon is used.

What is the most important step in MIG welding aluminum?

Aluminum has a layer of oxide formed on the surface when it comes in contact with oxygen and this layer has double the melting point of aluminum itself. So, properly cleaning the workpiece before welding can be considered the most important step.

Wrapping Up!

Mastering the art of aluminum welding with a MIG welder is not too difficult. All you need is the right guidelines, knowledge, and tons of practice.

The above guide helps you understand the unique characteristics of aluminum and also provides you with proper techniques and methods that can help you MIG weld aluminum efficiently.

You might run into some challenges in the beginning, but the guide above also helps you troubleshoot those issues.

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

Sheila James

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