When they’re learning to weld, most people use scrap pieces of mild steel. Mild steel is easy to work with, relatively consistent, and very forgiving of a beginner’s mistakes. It’s also fairly common in the wild and will be a frequent target for welding, so it’s good to learn the practicalities right away.
Aluminum is a different story entirely. It shows up in construction, automotive uses, and many more. Aluminum is used all over the place because it’s corrosion-resistant, relatively durable for its weight, and exceptionally lightweight. It also forms alloys with other metals quite well, generally introducing a variety of properties that can be beneficial in specific uses.
The trouble is that many of aluminum’s benefits are also why it can be tricky to weld. Welding aluminum presents several unique challenges, including:
Despite its qualities, aluminum requires more heat than mild steel to weld properly.
The weld puddle for aluminum looks very different than steel, so your visual cues will be different.
It’s surprisingly easy to burn through aluminum and drop your weld pool right through the material, especially with thinner material.
Different alloys require different kinds of filler to weld properly, and picking the appropriate filler can be difficult.
Welding aluminum is often considered difficult, but it’s not necessarily as tricky as it is different. If you’re used to working with mild steel, you’ll need to break yourself out of your habits and turn off your mental auto-pilot to weld aluminum properly.
Can You MIG Weld Aluminum?
MIG welding is entirely possible to use on aluminum, yes. Most professionals recommend TIG welding if possible, but MIG is perfectly acceptable (if a little more challenging) to get right.
Depending on who you ask, MIG might be better for thinner metal gauges, or TIG may be the preferred method.
This decision is largely down to preference and the comfort level of the welder; if you’re a beginner, TIG may be a better alternative if you have the equipment.
The key is the type of aluminum you are welding and the type of welder you have. Aluminum is a generic term and refers to many kinds of alloys, which we’ll get to here in a bit. If it’s an alloy compatible with MIG welding, you can weld it with a MIG gun.
What Equipment is Necessary to MIG Weld Aluminum?
If you’re planning on MIG welding aluminum, you must get your equipment and tool settings configured before you begin. Otherwise, you risk the metal not reacting as you expect, and the whole project can fail in various ways.
What do you need?
1. Cleaning Tools
One of the essential parts of welding aluminum is ensuring that the surface you’re working with is clean. This step is only sometimes necessary for particular welding projects and metals, but it’s a requirement for aluminum.
Why?
Aluminum oxides are much more heat-resistant than plain old aluminum or aluminum alloys. If there are any oxides on your work surface, the heat from your welder will melt the aluminum, but not the oxides. The aluminum melts at around 1200 degrees, while the oxides don’t melt until a whopping 3700 degrees! Those oxides will sink into your weld puddle and create inclusions, pockets, and weak spots in the weld.
Cleaning is also essential when welding aluminum because the oxide coating on aluminum can make it more challenging to adhere to. You may need to use a wire brush or sandpaper with your wire wheel for the best results.
After removing dirt, corrosion, and coatings, you must clean both of the parts you want to join with solvent or soapy water.
Not only is it critical to clean your surface before welding, but it’s also just as important to clean it the right way. For example, a steel brush can contaminate the surface just as quickly as if you left it dirty. An aluminum brush is recommended, and you’ll want to be careful with softer aluminum to ensure that you don’t muddle over inclusions rather than brush them away.
2. Filler Rods of the Proper Alloy
Selecting the right filler rod can be a significant chore. The wrong alloy can leave your weld susceptible to cracking or breaking, weaker than the joint should be, or otherwise not suitable for the job.
Choosing the appropriate alloy filler depends on the answers to several questions:
What is the base designation of the materials?
Does your weld need to withstand prolonged high temperatures?
Will the weldment be anodized when completed?
Does your weld have specific flexibility, strength, or toughness considerations?
Will it need to be heat treated?
These questions and a chart like this can help you decide what filler is best for your job.
That said, this is a beginner’s guide. That means you’re likely welding practice materials or learning directly from a mentor with more specific, practical advice. Everyone who teaches welding has their concept of what is most important, so be sure to ask them for specifics if necessary.
To further narrow things down, filler rods 4043 and 5356 generally apply to a vast majority of aluminum welding applications. It’s not perfect – there are certain situations where other rods will be necessary – but keeping those two on hand will cover many of your bases.
If you’re curious about the designations for filler rods, here’s a rundown. In short:
1XXX is close to pure aluminum.
2XXX is a copper alloy primarily used in heat treatment welds.
4XXX is a silicon alloy and is extremely common in various forms.
5XXX is a magnesium filler typically used in high-strength welds.
Each has numerous pros and cons, so choosing the appropriate filler is critical in many applications.
3. The Right Gas
Picking the correct gas is also vital for welding aluminum. Your choice of shielding gas will be a primary factor in the quality of the resulting joint.
For the vast majority of projects, the go-to choice is Argon gas. 100% pure Argon is a good shielding gas because of its ionization potential and ability to keep a weld clean.
The alternative, used by many pro welders, is a mixture of Argon and Helium. Helium offers a more significant ionization potential and thermal conductivity, making for broader, deeper welds. As a beginner, a wider, deeper aluminum weld is much more likely to burn through, so stick with Argon until you’re comfortable with it. Helium is best added to the mix for more extensive, thicker pieces of aluminum where weld depth and penetration are required.
The critical piece of information here is that using CO2 in your gas mixture won’t work, which is why many attempts to MIG weld aluminum fail.
4. What Settings are Best for MIG Welding Aluminum?
Properly configuring your MIG welding equipment is also important.
First, set your gas flow rate properly. You need enough gas flow to shield your weld correctly. Since you’ll be moving reasonably fast, a flow rate of around 20-30 cubic feet per hour is the general range to work in.
Second, the voltage of your welding gun should be appropriately configured. Usually, a voltage of around 21-24 is ideal. You’ll also want to ensure your MIG gun is set to DCEP (Direct Current Electrode Positive) polarity for the proper process.
Finally, welding aluminum is best done with the spray welding procedure. With this procedure, your arc is constant, and tiny molten filler droplets are sprayed from your gun along the arc and onto your weld surface.
Another common issue beginners run into is a cheap welding gun that jams rather than smoothly feeding the filler wire. Your gun needs a fast feed speed for its filler for this process to work correctly. Wire feed settings can also vary depending on the thickness of the wire you’re using.
5. What’s the Right Technique for MIG Welding Aluminum?
Welding aluminum is a high-heat process. Aluminum melts quickly, but it’s very thermally conductive, so the heat dissipates just as readily. This characteristic means it’s susceptible to variations in movement, and if you move the wrong way, your weld won’t work.
Proper aluminum welding requires three things.
First, you need a fast travel speed. This requirement is due to the heat involved; if you linger too slowly as you move, you’ll put too much heat into your materials, and risk burn-through. This scenario is prevalent with newbies attempting to weld aluminum. The travel speed required is much faster than with steel, and it will feel uncomfortably fast until you get used to it.
The second requirement is using the forehand technique. Where a backhand technique angles the gun away from the direction of travel, this does not facilitate good shielding gas coverage when you’re moving as fast as you need to. That means regular air will get into the weld pool and contaminate it. The forehand technique, where you tilt the gun 15 degrees toward travel, ensures proper shielding.
Third, you want to use simple weave patterns as you weld and avoid complex patterns. Using zigzag, looping, or other welding patterns is a technique used on steel to widen a weld and let heat linger a bit longer to increase depth.
Both are bad when welding aluminum and dramatically increase the risk of burn-through.
In cases where you’re welding thicker pieces of aluminum or need a larger fillet weld, multiple straight passes are better than an attempt at a wider weave.
My Weld is Bad: What Went Wrong?
If you’ve tried out a few aluminum welds using the MIG process and had mixed results, there are a lot of possible points of failure to diagnose. You can start by narrowing it down based on what went wrong.
1. Your weld burned through.
Burn-through or melt-through is caused by excess heat in one spot. There are numerous possible causes, but the most common for beginners is moving too slowly across the joint. Even if you think you’re moving fast enough, it’s likely that you aren’t.
It’s also possible that your joint type isn’t appropriate for the project. Instead of using an edge joint, you may benefit from a corner joint instead, or vice versa. This decision is very situational, however. Similarly, using thicker materials as a base might be appropriate, though you don’t always have a choice.
For more significant welds, you may need to work in shorter bursts to allow the material to dissipate some heat along the way.
2. Your welds are dirty.
Reactions or inclusions in the weld pool usually cause dirty welds.
First, check to make sure you’re using the proper technique. Forehand or push welding is necessary to properly shield your weld as you move, and if you don’t have the angle correct, you’re likely to end up with very dirty welds.
If you’re using the correct technique, it’s possible that your voltage needs to be higher, particularly considering your amperage. You won’t get a spray transfer without sufficient voltage, and your weld won’t work.
Also, make sure you’ve correctly cleaned the surface using aluminum-only tools. The wrong kind of tools will leave particulate matter behind that will cause inclusions in your weld.
Finally, double-check to ensure you’re using the correct shielding gas and filler rod. If either is incorrect, your welds will end up pretty bad.
3. Your welding gun gums up.
Two common problems can crop up, particularly with low-quality MIG welders.
First, the filler material burns back into the gun and causes problems. This scenario usually occurs if you haven’t maintained the proper tip-to-work distance along your weld, or right at the end of the weld.
There are a few “cheats” you can use to get this right, so talk to your mentor about it.
The second is when the feeding process for your filler wire is unsteady or prone to coiling up behind the gun, known as birdnesting. There are several common causes of this, which you can read more about here.
Putting It All Together
Many people claim that MIG welding aluminum is impossible. Some have never attempted to weld aluminum because they believe it is, and they are intimidated by it; others have had a bad experience trying. Others say so to warn off beginners from doing something much more challenging than welding steel. The truth is that MIG welding aluminum is possible; it’s tricky and requires proper settings and technique, but it’s easier than the rumors make it out to be.
However, since there are so many ways that aluminum welding projects can go wrong, it also requires practice and training to get them right consistently.
“Welding” is any method of joining two materials together. While welding often refers to joining metal pieces, welding can apply to other materials, including plastic and wood. Because of this variety, numerous kinds of processes are used to weld materials together. Even something as simple as glue can be considered a welding method.
However, we’re not concerned with those sorts of welds today. Instead, we’re talking about welding metal. With metal welding, you might use four main processes in a typical shop: MIG welding, TIG welding, Stick welding, and Flux-core welding.
These four kinds of welding are called “arc welding” since they use arcs of electricity as the key to their processes. Setting MIG and TIG aside, let’s discuss Stick and Flux-core welding today.(more…)
Corner joints are ubiquitous among the five primary types of joints in welding. Learning how they work and how to implement them properly is an essential part of learning how to weld, whether as a hobbyist or as preparation for a welding career.
Welding can range anywhere from simple joins and primary connections to fantastically elaborate art, but it all boils down to a small handful of techniques leveraged with mastery. Even master welders needed to start somewhere, and that somewhere is learning the different kinds of joints. Of the five types of joints, the Tee Joint is among the easiest to understand.
Welding can range anywhere from simple joins and primary connections to fantastically elaborate art, but it all boils down to a small handful of techniques leveraged with mastery. Even master welders needed to start somewhere, and that somewhere is learning the different kinds of joints. Of the five types of joints, the Tee Joint is among the easiest to understand.
What is a Tee Joint?
Different welding joints refer to various positions and angles of the two pieces of material being welded together. Tee joints are one of several kinds of joints, including butt joints, lap joints, and others.
Tee joints, also known as T joints, refer to the shape of the materials making a perpendicular connection, like a T. It doesn’t have to be precisely 90 degrees, but a right-angle connection is by far the most common. Though deceptively simple in shape, you can make tee joints with various weld types.
Tee joints are most often used when the requirements are simple: two materials need to be connected perpendicularly and aren’t shaped oddly. They are also common in machine applications and structural welding. Think table legs attaching to a table or pipes to a cross-member for a railing.
A tee joint may be welded on one side of the material, or it can be welded on both sides. For example, when joining two flat pieces of metal, both sides of the vertical member are easily accessible and can be welded. When joining a pipe to a flat surface, the outer side is accessible, but the inner is not. Additionally, for added penetration and strength, the weld may use plugs from the back side of the cross-piece.
The Difference Between a Weld and a Joint
In welding, it’s important to distinguish between a weld and a joint. Both are essential to any connection, and knowing which to use in which situation is part of learning and mastering welding.
A weld is a method in which two materials are joined, and any grinding or drilling is necessary to prepare the materials. Different kinds of welds lend different types of strength to the resulting joint. The most superficial tee joints are welded using a primary fillet weld; the materials are placed against each other, and the weld adheres them together. More complex versions involve beveled welds, J-welds, plug welds, slot welds, or melt-through welds.
So: a joint is the position of the materials, and a weld is how they are connected.
The needs of the finished product largely determine the choice of the weld. For example, a simple fillet weld is usually satisfactory if the joint is mainly cosmetic and does not need a high degree of strength. Conversely, if the joint is expected to bear significant loads or withstand lamellar tearing, more thorough preparations will be necessary.
The Pros and Cons of a Tee Joint
Tee joints are simple joints with many avenues to make them more complex and robust.
Typically, a tee joint is simple and relatively easy/fast to produce. When done correctly, tee joints can be pretty strong. However, they must be done correctly; if the materials are thick, you must prepare the edges, and additional support may be necessary.
The most significant risk is lamellar tearing, where the base material cracks due to inclusions and imperfections in the metal, and the contraction is caused by the welding heat. Lamellar tearing occurs because of tensile stress, which can limit the utility of the tee joint.
Tee joints can also be deceptive. With basic fillet welding, a joint can look and feel solid while only being adhered to on a surface level, meaning the joint will be prone to failure. With thicker materials or materials that will need to bear the stress, you must ensure that proper penetration into the metal fully adheres to the pieces.
How to Weld a Tee Joint
Welding a tee joint is simple, and it’s often a great introduction to welding. Here’s how to do it. For this article, we assume that you’re using an appropriate kind of welding (between stick, TIG, and MIG) and that you have the necessary equipment. If you’re still learning, your mentor should be able to provide you with what you need.
As a quick primer:
Stick welding is the oldest process and involves consumable sticks of electrodes. It’s cheap, versatile, and easy but also prone to molten spatter and slag, requiring more finishing. Stick welding is also the best outdoors and requires the least cleaning.
MIG (Metal Inert Gas) welding uses an automatic feed process for its electrode and shielding gas to protect the weld from atmospheric contamination. It’s easy to learn but more expensive and often requires enough equipment that there are better choices than this if you need a portable solution. It also requires more pre-weld cleaning.
TIG (Tungsten Inert Gas) welding is the most complex and high-skill version of welding, most used by artists and artisans. It provides the cleanest and strongest welds but the most coordination and care and the most preparation.
Picking the right kind of welding is essential. However, as a beginner, you will likely be starting with either stick or MIG welding and learning the ins and outs of the process before digging deeper into the most appropriate kind of welding for each job.
Step 1: Safety
Welding, when done correctly, is a safe process for both hobbyists and career practitioners. However, it has many different ways to go wrong, so safety is paramount.
Make sure you have an appropriate safety checklist before starting any weld.
Ensure you have the appropriate safety equipment, including welding gloves, a helmet or mask, a jacket or apron, and work boots. You may also consider a respirator, depending on the kind of welding and the location where you’re working.
Work in an appropriate location, outdoors, in a welding shop, or in an otherwise safe area. Be wary of nearby flammable objects, and make sure you have safety tools, such as a fire extinguisher, fire blanket, and eye wash bottle.
Ensure proper ventilation when welding.
Take care of electrical safety, and ensure your equipment is in good working order.
Welding safety is critical, so take this step, no matter how deep into welding you delve.
Step 2: Prepare Your Materials
Impurities are the enemy of solid welds. Before welding metal, you must prepare that metal. There are two kinds of preparation; you must do the first for every joint, and the second depends on the type of weld.
To prepare your materials, you’ll need an angle grinder to remove surface materials, mill scale, dirt, paint, and any other impurities that can get between the two pieces of metal and your filler material. Remember lamellar tearing? Lamellar tearing can be minimized or avoided in various ways, including cleaning. Welding two pieces without adequately cleaning them will result in those impurities baked into the weld, weakening it for inevitable failure.
It’s also a good idea to clean a spot for your ground clamp to ensure a solid connection and reduce the risk of stray shocks.
At this point, you would typically be thinking of what kind of joint to use, but as we’re discussing tee joints, that choice is made for us. So, now you must consider what type of weld to use.
Fillet welds do not require further preparation of the materials and are best used when strength is not needed or when the materials are thin.
Beveled welds grind a straight, diagonal cross-section from the vertical member of the T, creating more space for the filler metal and deeper penetration. These are commonly used when a stronger weld is needed and for pipe welding.
J-welds are similar to beveled welds, except they leave more material at the curve of the J. This technique gives the weld more strength, similar to the beveled weld, but leaves more material in the contact surface, so there’s a more significant margin of error.
Plug or Slot welds involve drilling or grinding holes in the flat member of the T to create plugs or slots of filler material to lend additional strength to the joint. These require further preparation but form a stronger joint.
Note that the choice between a J or a V bevel primarily comes down to the tools you have on hand. A J is usually better if you have a tool to produce the bevel. J welds are slightly more robust and easier to do but are harder to bevel by hand uniformly.
Basic fillet welding is fine for practice welds or simple bevels to practice something more complex.
Step 3: Take Position and Tack Weld
High-quality welding requires even, thorough, steady handling of your welding gun. To facilitate this, you want yourself and your materials to be positioned such that you need to move as little as possible to perform the weld. Practice moving the gun across the weld, maintaining a steady hand. Reposition if you encounter something in your way or would otherwise need to reposition mid-weld.
Next, you’ll want to secure the two pieces using a tack weld. Tack welding is performed by making small dots of weld to hold the materials in place for the final weld. This step is also your last opportunity to verify accurate positioning, angles, and squaring of the materials. No one wants to weld a T only to find it looks more like a 7!
After you have tacked the vertical member in place, you are ready to begin the final weld.
Step 4: Lay the First Bead
You move your welding gun over a joint and deposit filler material when welding a joint. The pattern in which you do this is called a bead. The simplest bead is a stringer, a single straight bead across the joint being welded.
Different kinds of beads allow you to create more comprehensive welds and better control the heat in your weld. For example, this image shows multiple motions, such as waves, triangles, and ladders:
A simple stringer bead is all you need for a practice weld and a beginner welder. Later, you can practice other kinds of beads, different positions for welding, and different circumstances in which welding can go wrong. After all, it’s just as important to know how things fail as it is to understand how they go right, so you can recognize it and learn to adjust.
If your materials are particularly thick, you may need to lay more than one bead. You may also need to return to step 2 to re-clean the weld for a second pass to prevent slag from contaminating and weakening the joint.
Step 5: Grind and Finish
Once your weld is complete, it’s time to finish it.
If your weld is not going to be visible, or if the overall look of the weld doesn’t matter, then you’re done. Unfinished welds can look beautiful in the hands of a professional, but they may also be susceptible to rust when exposed to the elements. Welds are often the first area in construction to rust.
So, you may need to finish the weld. Completing a weld can involve:
Grinding the weld to remove slag left over from the welding process (particularly with stick welding).
Grinding to smooth out unevenness in the weld itself (which is familiar with beginners and those with trouble keeping steady hands.)
Paint and other treatments for the finished product.
If you are planning to grind your joint, you should exercise caution. It’s effortless to over-grind and to weaken (or even remove) your weld entirely, separating your pieces and leaving you back at square one. While that can give you a good source of another round of practicing, it’s not a habit you want to get into.
Conclusion
Welding is an essential skill for any tradesperson, and at the same time, it is one of the most satisfying. There are many different types of welds, but the tee joint is one of the most common, so if you’ve been looking for a good beginner’s guide, this should help.
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