What is cold welding?

cold welding

Whenever we think about or talk about cold welding, we look at it through the same lens as the heater. The first thing that comes to mind when talking about welding is thermal energy to heat and weld metal objects.   

Most welding techniques involve heating metals to their melting point and then joining them together to create a fusion that not only lasts longer but is also more durable and functional.

All welding techniques, such as friction welding, arc welding, laser welding, and ultrasonic welding, involve heat in one way or another. Heat is seen as a necessary addition to the welding process and makes it easier to monitor it.   

However, what we perceive and believe about welding is far from reality. Cold welding is a prevalent form of welding that works without the need or presence of heat.   

To make the process easier, cold welding is a reasonably efficient method of joining two metals together without using heat or thermal energy. To the naked and inexperienced eye, this whole procedure may seem too incredible to be true.   

However, cold welding is an integral part of the welding industry, and it is undeniable.   

How to connect metals without heat?

cold welding

To understand how metals can be joined together without heat, we first need to understand how the process works when you do it with heat energy. The presence of heat during a welding process will help make metal parts sufficiently plastic.   

As soon as the parts become plastic and flexible, the welding process jumps in the direction of diffusion of the atoms. The release process involved either the two jobs you’re working with or a completely different medium in between.   

However, contrary to popular belief, you do not need heat energy to perform a welding job  . Cold welding using energy generated by free ions and electrons is living proof of how welding can be done without thermal energy.                 

Cold welding shows in real-time how welding can be done without thermal energy. Cold welding, also known as contact welding or cold pressure welding, uses pressure to join and diffuse two materials’ atoms.   

This process is scientifically recognized and known in scientific circles as solid-state diffusion. It is scientifically possible to weld two metal parts using compressive forces.   

Usually, when you press two metal surfaces or materials together, they will not weld together. No matter how hard you put on the materials, the pressure alone will not help create a weld.   

This obstacle is particularly noticeable because of the additional oxide layer on the surface of these two materials. This oxide layer acts as a barrier and prevents the layers from bonding together by simple pressure.   

Since welding is the most common practice on metals, let’s take their example. Almost all metals have an additional superficial oxide layer on the surface, which acts as a barrier.   

The surface layer prevents metals from being welded with just the application of force or pressure. You cannot weld the two pieces together because the oxide layer on the surface will not allow the two metals’ atoms to diffuse together.   

Cold welding takes this problem and the possibilities of pressure welding into perspective and prepares both metal surfaces for what is to come. The preparation process is extensive and includes cleaning and brushing all metal surfaces to the point of removing the top layer of oxide.   

Since the oxide is no longer there, it can easily weld substances under pressure. No thermal energy is required, and you can add a whole new definition to the weld using cold welding.   

However, the cleaning and brushing process requires a thorough application without leaving any stains on the surface intact. The process includes the degreasing of all metal surfaces involved in the process.   

After degreasing, gently brush the entire surface of the metals.

Once you have achieved the desired cleaning of both surfaces, the critical process of applying pressure can begin. Remember not to rush through the process, as you will need to brush and clean the surface with all the necessary adjustments.   

During the step of applying pressure, you need to make sure that the materials are pressed together and that the correct force is applied. Strength is not the same for all metals.   

Different materials have different properties, so it is best to understand their welding properties and weld them at high pressure.

Cold welding also has its conditions that should also be considered before starting the project. On the one hand, cold welding only works with materials that have not undergone extensive hardening and are malleable.   

The process cannot be performed on objects that have undergone rigorous hardening procedures and inherently ductile objects.

Once this condition is applied, many materials will be cut. This will eventually narrow down the list of materials that may be possible candidates for the cold welding process.         

To help you make a decision, cold welding should be your first choice for welding soft metals.

Cold welding can be used to make a wide variety of joints. The most common connections that can be made through this process include:    

  •       Overlapping joints
  •       Butt joints

With butt joints, it is not necessary to clean the surface layer of metals welded together. In this sense, you can easily break the extra layer on the surface by the pressure exerted on it.   

This saves you the extra time and effort that you would have otherwise spent on cleaning and brushing.

On the other hand, overlapping seams require special cleaning and brushing of the surface, as metals do not stick or stick together without cleaning. These connections require extra effort in the process.   

History of cold welding

cold welding

Cold welding may seem like a relatively new concept to you, but its history dates back centuries. Excavators who study relics and snippets from the past have found tools welded using cold welding techniques.   

Some of these tools date back to the Bronze Age and demonstrate the antiquity of the concept of cold welding.

Although the world’s citizens have long practiced cold welding, the first scientific experiment on this technique was conducted by the Rev. JI Desaguliers in 1724. This experiment was the first of its kind and helped to advance research in this domain.            

Desaguliers tested the concept of cold brazing with two lead balls. The two lead balls had the same diameter and were carefully observed.      

What Desaguliers has done to keep these two lead balls together and then apply pressure as they turned. In doing so, Desaguliers noticed that the balls were sticking together.                        

It was the first scientific test of its kind, and it opened the doors to the science of cold welding.

Other related tests indicated that the seal formed after the pressure application had the same strength as that of the parent metal. Therefore, the bond formed between the lead balls had the same strength as the lead balls themselves.   

This showed that the weld was reliable and that it did not suddenly collapse.

Cold welding has been an exciting topic in science, and many scientists and budding researchers have shed light on it. We now have over a dozen theories dealing with the formation of this bond.   

Some of these theories determine and focus on recrystallization, while others have also proven the welding energy hypothesis. However, all of these investigations have been discredited and refuted for lack of evidence.   

The only acceptable explanation for creating the cold weld is the formation of a metal seam.

Metal bond has the same properties and strengths as base metals. It is formed due to the interaction between free electrons and ions of the two metals when they are pressed together, and an absolute force is exerted to exert pressure.

When done with the proper processing and material procedures, cold welding can help create a meaningful weld that will last a long time. However, this can only happen if the weld between metals is as strong as the base metal itself.   

That force and only force can be obtained if all procedures ym ed all necessary treatment are followed religiously.   

Cold welding restrictions

Since we’ve just taken you through the bright side of the picture, you might be wondering why cold welding is not standard in the industry. Fine, it’s used by many individual welders, but it’s still not the most common welding method in the industry.   

Indeed, there are certain limitations associated with cold welding.

A perfect cold weld is extremely difficult to achieve at first. The weld produced by cold welding is only as strong as base metals if the cold welding techniques are perfect.           

The lack of perfection and difficulty obtaining it is usually due to various reasons such as the presence of oxide layers on the metal surface, surface impurities, surface irregularities, and many others.

The oxide layer is often challenging to remove, even if you brush and clean it to the best of your ability. Besides, irregularities in metals’ surface can make it difficult for metals to adhere, even if the surface is clean and brushed.   

Perfect cold welding can only be done if the two surfaces you are working on are clean, free from all kinds of contaminants, have a regular shape, and have no surface irregularities. It is also essential to know that the easier it is for you to form a uniform weld, the more flat and even its surface will be.                 

If your final weld isn’t smooth or flat, it won’t have the strength you want.

Cold welding is also not an industry standard, as there is a limit to the number of metals that can be welded using cold welding techniques. As explained above, non-ductile metals or metals that have been subjected to rigorous hardening procedures would not respond effectively to cold welding processes.   

Even if you could create a cold weld on them, it wouldn’t stick for long. As you narrow your options, you will find that soft non-ferrous metals can only be welded together by cold welding.   

For example, aluminum and copper are the two most common metals welded using cold welding processes. Metals that contain some form of carbon also cannot be welded by cold welding.   

These limitations make it difficult for industry and individual welders to adapt this welding method as the primary welding source. Of course, cold welding can be beneficial in some scenarios, but the process is too tedious and inefficient in most scenarios.   

Advantages of cold welding

Just as we have discussed the limitations of cold welding, some advantages of the process deserve special mention. The most significant and notable advantage of cold welding is that it has the same adhesive strength as the starting material.   

While creating the possible configuration for cold welding can be difficult. Once you have created the correct configuration, you will be happy to know that the weld you created is strong enough. This feat is challenging to recreate with other methods of metal welding.   

Cold welding techniques can be extremely beneficial when welding 2xxx and 7xxx series aluminum. As mentioned above, cold soldering techniques are perfect for aluminum and copper surfaces.   

No other metal welding option can weld aluminum of the 2xxx and 7xxx material series together.

Cold welding is also an excellent option for welding aluminum and copper together. Other forms of soldering are known to make aluminum and copper extremely difficult to solder together.   

Cold welding simplifies the process and makes it easier to weld the two parts. The ultimate bond that you create by cold welding between these two metals is quite strong and will last a long time.   

Finally, cold welding gives you a simple solution to creating healthy, clean welds on process aiding surfaces. The welding process creates a strong bond without forming intermetallic bonds of a brittle nature.           

Cold welding applications

Although cold welding is not a common practice in the industry, it is still widely used for welding wire. The process is used when welding wires because it creates a strong weld, and no heat is generated.   

Thermal energy can damage cables, so cold welding is the order of the day.

Cold welding provides wires composed mainly of alloys of brass, zinc, copper, aluminum, silver, silver, gold, and nickel 70/30, and gold, a perfect and durable weld. Interestingly, you can also buy some easy-to-use hand tools for working with cold solder wire.   

These tools are incredibly portable and easy to carry. They can help save time and effort.   

Cold welding is also a possible option when different metals such as copper and aluminum need to be joined. We have already discussed how cold welding can create a strong bond between copper and aluminum.   

This weld is more substantial than that which can be created between these metals by any other method.

Is cold welding strong?

As we saw earlier in this article, cold welding can create a strong joint if the conditions and metals are feasible for its use. When conditions are right for cold welding, the weld created between metals will be as strong as the base metals themselves.   

However, creating the perfect conditions can be difficult as the technique cannot be applied to non-ductile and heavily cured surfaces. The brushing and cleaning process also requires considerable effort, and the metals should have a regular shape.   

However, the bottom line is that cold welding can produce the hardest and strongest welds if the environmental conditions are suitable for its use.

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