Can You Weld Cast Aluminum?

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Yes, most aluminum castings can be welded. You can use 5356 filler to weld these. They aren't heat-treatable, but you may weld them with 5356 filler. However, these 7XX.0 aluminum-zinc casting alloys are also heat treatable, and they are more difficult to weld than other metals. You may not weld some of them at all.

The first thing one need to know is what kind of metal they are welding together. A welder needs to know if the metal is cast or not.

If the metal is cast, it might need to be heated before welded together. A welder will need to make sure that their preheat temperature does not exceed 400 degrees Fahrenheit.

The filler material used depends on how much time you will spend welding this spot and how much strength your weld needs.

One way to weld with a filler rod is by casting the rod simultaneously as its base metal in a mold at the same facility; post-weld heat treatment develops properties in both materials equally well in this case.

However, sometimes a welder shouldn't use a heat treatable filler material and instead, use one that's not.

The Welder should try to keep their weld composition around a ratio of 70% filler alloy and 30% base metal. The different filler materials may be adequate for the job, and only one will give you optimal results for your specific welding needs.

Related Post: TIG Welder For Aluminum

What is Cast Aluminum?

Cast aluminum is made from molten aluminum that has been heated to a very high temperature. It can be molded into many shapes and cooled, and it is a good material for a lot of things. For example, if you want a table, the molten metal is shaped into a table and then cooled off to make it solid.

Things to Consider Before Attempting Weld Cast Aluminum

Many people have a misconception about welding cast aluminum. They think it is an extremely difficult process that requires years of experience to complete successfully.

This couldn't be further from the truth, as with some basic knowledge and preparation, you can weld cast aluminum in your garage or basement without any prior experience at all!

In this part, I will give you some tips on how to do just that- so read on if you want to learn more.

01. Filler Metal Selection

Some filler may be adequate for a specific use, but only one of them will provide the optimal response to certain performance needs.

Moreover, choosing a filler metal is important for welding. It would be best to think about what you will use the weld for, and then you should choose accordingly.

The best alloys are usually the ones that are low in nickel, high in copper, and can be easily welded.

If you're not sure what filler metal to use, you can look at the list of most popular ones and see if they can fit your needs.

In this list, there are 2319, 4008, 4009, 4010, 4011 (wrought alloys similar to cast C355.0, A356.0, A357.0), 4043, 4047, and 4145 that you can buy at a store near you or online.

02. Pre-weld & Post Welds Heat Treatment

When you weld a heat-treated metal, the heat from welding will make it less strong. You do not want that to happen. Heat treats all your metal before you weld it together and then again after it is finished. This will make it stronger and last longer.

03. Use AC TIG

With TIG welding, we use an alternating current (AC) power source. It switches between positive and negative.

When the polarity is positive, it comes from the work surface towards the electrode and cleans where there is oxide not to contaminate your weld.

And when the arc switches back to negative, energy comes from the electrode to where you are working and melts metal there.

You can change how long each of these phases happens by changing a setting on your Welder called "squarewave."

Some TIG welders have a "squarewave" control feature. The squarewave can be increased up to 90% of the AC cycle, which allows the electrode negative (EN) part of the AC cycle to go up that high.

By increasing the negative phase, you will get faster welding and narrower weld beads. This means you can use a smaller diameter tungsten electrode to direct heat in a confined area more precisely.

But reducing your negative phase will make cleaning less effective for heavier oxidation and make it harder to weld on thin castings because there would be less heat penetration.

04. Use inverter-based Welder

Most of the important welding advances in the GTA focus on new ways to use power and control the AC wave.

These advances came from using "inverter-based" power sources, which allow you to do things with your Welder you never could before.

For example, you can change how much EP (electrode positive) there is in each half of the AC cycle with these sources.

But there are no rules about this! The typical mistake people make is overbalancing, which causes too much heat on the tungsten electrode.

The arc starts to degrade, and the operator cannot control the arc. The weld puddle also loses stability.

On the one hand, too much electrode negative can cause too much penetration and a scummy weld puddle. But on the other hand, if your weld puddle looks like it has black pepper flakes floating in it, add more cleaning action (EP) to remove oxides and other impurities.

Conventional welder output is at 60 Hz, but inverter-based welders adjustable frequency from 20-250 Hz.

Decreasing the frequency of the welding creates a better weld because it creates a wider arc cone. The arc cone is wider, and this means that it melts more metal. It also transfers more energy to the workpiece, which makes it fast to weld something.

05. Amperage setting

You can control how much electricity flows through the workpiece and how much goes to the tungsten.

For example, when welding a thick piece of aluminum, you can put 250 amps of EN into the work and only 60 amps of EP into the tungsten.

This means you will be able to weld faster. You can also use this feature to help make sure that you don't need to preheat your metal before welding it together.

Some companies have found a way to make things go faster by cutting production time by up to two-thirds.

They are using this new technology. It lets them use an electric current that is stronger than the current they are used to, but it doesn't mean that they need more gas.

This will help them weld with smaller electrodes and make narrower welds.

New technology helps make the Welder's job easier. With this new tech, you can use less tungsten and still get a good bead on the metal.

Hitting the "balance" button is important to keep your arc from getting too wide or narrow. You'll want to experiment with what values work best for your project.

06. Frequency control

Some problems happen with welders. They can't begin welding, so it's not good. This problem frequently occurs during the EN to EP change because the Welder does not have enough voltage to drive through the zero amp range and then re-establish the arc at the electrode or cannot transition through this range quickly enough.

To make the arc start better and stay on, a traditional GTAW machine can use high frequency on the AC sine wave. This makes an arc that is easier to control. If you want to help, even more, there are three ways you can do this: "HF off," "HF start only," or "HF continuous."

Welders generate HF near 1.2 MHz, which is the same as AM radio. That can interfere with electronics in your shop like computers and CNC machines.

An inverter-based welder is the best to use because it only uses high frequency when you need it and then switches back to normal AC power when you don't need high frequency anymore.

It also doesn't cost anything extra for a high-frequency module if you get an inverter welder.

What Are the Essential Variables of Weld Cast Aluminum?

A basic, professional-grade TIG welder with AC output allows the user to adjust four parameters:

  1. Shielding gas pre-flow time
  2. Gas post-flow time
  3. Amperage
  4. Balance control

The Welder will have potentiometer-style control knobs or touch displays to adjust these factors.

01. Shielding gas pre-flow time

Pre-flowing the shielding gas is for two reasons. It will clean the area of the weld, and it will start to start welding. If it's not a critical application, then you can leave it at one second. But for a critical application, you should pre-flow the shielding gas longer than six seconds.

The amount of time you need to pre-flow the gas depends on how sensitive the application is and what kind of Welder you're using. One second will be enough for a non-critical application, but if it's critical, then use six seconds or more.

When welding thin materials (25 - 50mm), there can be an increased burn-through rate due to improved heat concentration at the toes of the weld pool. This may necessitate reduced amperage or increased travel speed when adding filler wire or peaking up between passes.

02. Gas post-flow time

You need to let the gas out of your welding machine for a few seconds at the end of a weld. The "post-flowing" technique is used to keep the welding puddle safe after it has cooled through areas where it is more prone to oxidation, cracking, or contamination.

You can use one second for every 10 amps you are welding (0-50 seconds). More gas is needed if bigger puddle! Post-flow also cools tungsten to keep it from getting dirty with oxidization.

03. Amperage

"Sequencer controls" are a feature found on many TIG welders that allows you to regulate the start current, start time, crater time, and final current.

The start controls are for when you want your weld to be hotter or cooler. If you want it to be hotter, then turn the knob up. And if you wanted it to be cooler, then turn the knob down.

Aluminum castings are thick. They can be hot. The metal builds up heat over time, but if it starts hot, it will stay hotter for longer. That is why welders use a "hot start" on their metal to make it hotter when they first put the tools on the metal.

Thin pieces that are at risk for melting or warping can be helped by a cool start.

04. Balance control

The start-time control knob adjusts the timer, which is usually from 0 to 15 seconds. When the Welder's output reaches the preset start value (as opposed to ramping up), the operator activates the contactor/control device, i.e., foot pedal or fingertip controls.

Once the timer times out, amperage control returns to the foot pedal or fingertip device.

On the other hand, "Crater time" controls how long it takes to ramp down from the welding current to the minimum current over time. "Final amperage" control lets you set how much of your welding amperage you want as a final amount.

Crater cracking is a problem with welding aluminum, and it can happen if the heat from your torch is too strong. Using the crater time control gives you more control over how much heat your aluminum workpiece is exposed to.

How to Weld Cast Aluminum: Step By Step Welding Guidelines

Cast aluminum is a popular material to use for many applications in the automotive industry. It's also used in aerospace, commercial construction, and other industries that require lightweight, corrosion-resistant products. Welding cast aluminum requires special equipment and techniques to ensure quality welds that will last.

This part addresses how to weld a cast aluminum step by step welding guidelines, including what you need before you begin preparing your workspace, proper safety precautions when welding any metal, types of electrodes you can use with TIG or MIG welding machines, and more.

01. The metal that you're welding needs to be clean. You can use chemicals to clean the metal if you want. Some people like using thermal cleaning because it makes the oils and resins go away from the casting.

But when you are using this, make sure that it's not too hot, so it doesn't become broken. Thermal cleaning can also negatively affect some metals, though, so be careful about which type of metal you use it on.

One way to eliminate all carbon is by doing a bead blast after thermal cleaning, but this might not work for everyone, depending on what kind of metal they're working with.

02. The 2nd step of the casting's inspection is to pressure test it to look for fractures and porosity leaks.

03. If repairs are needed, remove any internal or external parts that can easily catch fire or get warped.

04. To remove the crack, you need to do some work. You can use a machine called a "miller." The miller will grind out the crack. It can be messy, so make sure you are protected with eye protection and gloves.

Clean the spot where you want your casting to go with a safe, non-toxic cleaner. You can use something like acetone and then finish with alcohol. Once it is all dry, cast your piece of metal there.

05. Make the metal very hot before you weld it. Heat it for at least two hours, but not more than 500 degrees Fahrenheit. Do not heat the finished metal if it is a different kind of metal that has been treated to make it stronger. If you are welding on this metal, do not heat more than 275 degrees Fahrenheit or your finished product will be too soft.

You need to make sure that your weld time is short for about five minutes or less. If the welding goes on too long, it will start to overheat the metal. Castings will heat up for 15-20 minutes after they are heated. Put some blankets around where you are welding to keep this heat in so that air does not come in and cool the metal down too much. If it gets too cold, put it back into the oven or use a torch if possible to heat up again until it reaches its working temperature again.

06. Ensure your TIG welder has at least 250-amp capacity and a water-cooled torch with foot amp control.

07. Use argon gas when welding with 15-20 cfm or a 25/75 mixture of argon and helium when welding faster.

08. To protect your eyes, use a welding lens. The gold tint will help you to see well than the green tint.

09. To weld, first, you will need to ensure that you have the right type of tungsten. If you are using a GTA welder, pure tungsten is best. If you are using an inverter-based GTA welder, 2% thoriated tungsten is best.

Wave balancing will help clean and float contaminants out of the puddle during welding cracks. When repairing cracks, use wave balancing to clean and float any foreign substances out of the weld puddle.

When utilizing a conventional GTA welder or an inverter-based GTA welder with sharp-tipped electrodes, do not allow the tungsten electrode to contact the base metal or filler rod. Start the arc with high frequency and keep the electrode approximately 1/8" from the surface to use high frequency on a regular GTA machine.

Maintain an arc length of approximately one electrode diameter from the surface while welding with a traditional GTA welder or an inverter-based GTA welder using sharp-tipped electrodes.

10. Use ER 4043, ER 5356 filler rods. Store them in a container, so they don't get oxidized. Keep the filler rod in the weld zone when filling cracks in metal to prevent it from being oxidized.

To make the weld good, you need to hold the filler metal at a 15° angle from your workpiece and use a tungsten electrode.

11. Put the metal back into the oven after welding, allow it to cool down slowly. This will help to make sure that you do not get any new cracks on it.

12. Machine blends the weld layer if it is a shape that matches the surface next to it. Inspect for any defects before you say that your repair is done.


If you've been looking for a step-by-step welding guide to cast aluminum, look no further. This article covers everything from design considerations to preparing your equipment and materials before starting an actual weld project. We hope this guide has cleared up any confusion or questions that you may have had about how to properly weld cast aluminum.


Last Updated on December 1, 2021 by weldinghubs

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