When you think of welding, you likely picture sparks and heat being used to fuse two pieces of metal together. Cold welding is the complete opposite of that. There’s no heat or sparks at all. Instead, pieces of metal are welded together under ambient temperatures through an immense amount of pressure.
This article will help you have a better understanding of this welding process, how it works, its benefits and challenges, and when you should consider using it!
What is Cold Welding?
Cold welding is a welding process that joins two or more pieces of metal together using little to no heat or fusion.
With other welding processes, heat is used to soften metals and bond them with a filler material. While the exact technique can differ between types of arc welding, the general concept is the same.
Most types of welding can’t be done without using heat energy. For two pieces of metal to be welded together, heat needs to be used to soften the metal being welded. This makes it possible for the pieces of metal to fuse with one another and a filler metal.
The process of cold welding is a little bit different than you might be used to seeing inside a fabrication shop.
Also referred to as contact welding or solid-state welding, cold welding uses a form of pressure to join the materials. Just like with other welding processes, the amount of pressure required to cold weld can vary similar to the way amperage can vary when MIG or TIG welding. It all depends on the type and size of the materials you’re working with.
With cold welding, there are no sparks, liquid or molten phases like you see when MIG or TIG welding. When materials are prepared beforehand, two or more pieces of metal can be brought together in a vacuum and create a bond.
How Does Cold Welding Work?
Cold welding doesn’t happen as easily as you might think. If you were to just grab two random flat pieces of aluminum and rub them together, they won’t magically become bonded.
Before you can cold weld two pieces of metal together, you need to properly prepare the materials. Doing so will allow you to create a vacuum when the pieces of metal come in contact with one another.
To get started with cold welding, you’ll need to thoroughly clean the pieces of metal you are planning to weld together.
Metals left sitting out under normal conditions will form an oxidized layer on the surface. This layer (plus other impurities like grease or dirt) needs to be removed as it acts like a barrier that prevents the metal atoms from bonding.
You can clean your materials with a wire brush to easily remove these barriers.
Just remember that if you’re working with aluminum, make sure to use a wire brush that is only used on aluminum. Otherwise, you’ll just be introducing impurities from other metals that can contaminate the aluminum.
Once the oxidized layer is removed, the pieces of metal can be pressed together. Using a high amount of pressure, you can create metallurgical bonds.
This type of bond occurs when the atoms that make up both pieces of metal can’t differentiate and jump between the metals to create a physical bond. For the best results, you’ll want to make sure pressure is equally applied to both parts. This ensures that there is 100% surface contact at the joint.
Pros and Cons of Cold Welding
While cold welding might not be the most popular welding process, it’s a valuable option and one that you should know how to do properly. Sure, the majority of professional welders and DIYers aren’t working on spacecraft or with other applications that would require cold welding.
But, knowing how to cold weld is still important.
Pros of Cold Welding
As you’ll see below, there are a few big benefits to cold welding and some instances where it’s your only option!
Join Different Types of Metal
It isn’t always easy to join together different types of metals. For instance, aluminum and copper have two drastically different melting temperatures that are over 800 degrees apart!
This vast difference means that it would be difficult to weld these materials using traditional welding processes.
But because cold welding doesn’t need heat energy, properly cleaning and pressing the materials can create a solid bond.
Create Strong and Clean Welds
With other welding processes, like MIG welding, there can be splatter left around the weld area that needs to be cleaned up afterward.
There’s also the risk that the weld could become brittle or crack if there were any contaminants present around the weld pool.
With cold welding, you can avoid both of these problems. There’s no melting or fusion happening that you’ll need to clean up with a wire brush or grinder. Better yet, the strength of the weld is as strong as the parent materials that are used.
No Negative Impacts from Heat-Affected Zones
If you aren’t careful when welding, it’s easy to overheat a piece of aluminum or mild steel and burn a hole right through the workpiece.
The more common welding processes can each create heat-affected zones around the base materials. When this happens, the materials can become compromised, weakened, and deformed as a result. Cold welding avoids all of these problems. Since there is no heat energy being used to create the weld, there are no heat-affected zones that can cause issues.
More Versatility When Working with Aluminum
Cold welding makes working with aluminum easier. In fact, welding with certain types of aluminum is not even possible unless you are cold welding them. 2xxx and 7xxx series aluminum are prime examples of that. These types of aluminum cannot be welded using any process other than cold welding.
Cons of Cold Welding
As you can see, there are several benefits to cold welding. When the conditions and materials are right, cold welding can be an effective way to get the job done. But, as with any welding process, there are certain limitations and drawbacks. For a lot of welders, these drawbacks make it difficult to use cold welding as their primary process. Here are some of the biggest challenges of cold welding.
Time-Consuming
For cold welding to work properly, you really need to invest some time in properly preparing the materials. This can end up being quite time-consuming. That’s why you won’t see a lot of cold welding happening at most fabrication shops unless it’s absolutely necessary. It’s just not cost-effective or manageable for most high-production environments when other techniques can get the job done much quicker.
Material Limitations
Not every piece of metal can be joined to another through cold welding. In order for this welding process to be successful, the metal needs to be ductile and soft enough. Since there is no heat being used to soften the materials, metals that have undergone severe hardening processes can’t be used. The type of metal also needs to be considered before you try cold welding. If the metal contains any form of carbon, this welding process simply won’t work.
Size and Shape Limitations
To create the strongest cold welds possible, you’ll want to stick to flat regular surfaces. This ensures you’re able to get pressure distributed evenly across the metals being joined. If there are any irregularities on the metal’s surface, it can be difficult to cold weld it.
Any surface irregularities will have to be removed, if possible, during the preparation process for the weld to be effective.
When Should You Use a Cold Welding Process?
Despite the challenges of cold welding, there are still several applications where this process is the best option. Cold welding is most often done when wires need to be welded together and thermal energy has the potential to cause problems. Cold welding can create strong joints between wires and is commonly used with aluminum, copper, 70/30 brass, nickel, gold, silver, silver alloys, and zinc.
This welding technique is also useful if you need to join two dissimilar types of metal. As mentioned above, welding aluminum and copper can be difficult due to the drastically different melting temperatures of the metals.
Cold welding makes it possible to create a strong, long-lasting weld without worrying about heat damaging the metals. The process is also effective if you’re working with 2xxx or 7xxx series aluminum and need to join two pieces together.
Cold welding doesn’t just happen on Earth. When an astronaut needs to make repairs in space to a spacecraft or the space station, they employ cold welding processes.
Being able to fuse materials without a liquid or molten phase allows astronauts to work quickly and limits the dangers that come with being outside their spacecraft.
Cold Welding FAQs
What Kind of Joints Can I Cold Weld?
There are two types of joints you can make when cold welding—butt and lap joints. Which joint you choose to create all depends on the materials you’re working with.
If you’re going to be welding aluminum or copper wires together, butt joints are the way to go. Most cold welding machines today will require you to trim the ends of the wire flat before they’re loaded into the machine. The trimming helps to ensure that there is a clean and flat end to bond with the other wire.
If you’re working with a sheet of metal like aluminum and need to weld it to another sheet, you can do so with a lap joint. Just keep in mind that due to the immense pressure being applied, at least 50% thickness of one of the sheets will be lost. This impacts the strength of the materials and needs to be considered when designing a project.
What Metals Work Best When Cold Welding
In order for cold welding to work, there cannot be any trace of carbon in the metals being used. The metal must also be ductile and soft enough for the process to be possible. If a piece of metal has undergone a hardening process, you won’t be able to cold weld it to another piece of metal.
The most common metals that are used when cold welding are aluminum, copper, 70/30 brass alloys, nickel alloys, gold, silver, silver alloys, and zinc. It’s your only option if you’re working with non-weldable grades of aluminum such as 2xxx or 7xxx series.
Is Cold Welding Permanent?
Cold welding needs to take place under the right conditions to make the weld effective. If you follow the process properly by thoroughly preparing the materials and using the right metals, you can create strong, long-lasting bonds. The only way a weld will not stay permanent is if there is extensive damage to the workpieces that causes the weld to fail.
It can’t be stressed enough that you need to take the time to properly prepare the materials and use the right shape and size. If cold welding is not done under the right conditions, the chance for joints to become weak and fail is increased. As long as you follow the cold welding best practices, you can be sure that your cold weld will be strong and hold.
Learn More About Welding Inside Welder101
If you want to learn more about cold welding and other welding processes, Welder101 is where you need to be!
Within this comprehensive training program, you’ll find a growing library of video tutorials and resources that cover every aspect of welding.
Enrollment in the program comes with a lifetime membership which means you can learn at your own pace or revisit skills anytime you need. You will also be given access to our private Facebook group where you can interact with other welders from across the world. It’s a great place to ask questions, share your work, problem solve projects, and connect with one another.
Welder101 also includes discounts on clothing and equipment from some of the industry’s most reputable companies. You can use those savings to help build your shop and maybe even pick up a new cold welding machine.
Don’t waste any more time. Enroll with Welder101 today!
