Cold welding is one of the best welding techniques for non-ferrous metals.

When you think of welding procedures, the first thing that comes to mind may be the use of heat. Technologies such as arc welding, friction welding, ultrasonic welding, and laser welding all involve heat in some way. In fact, heat is considered synonymous with welding, and in the above example, heat is essential for joining two metals together. 

However, these are not the only methods. Believe it or not, you can actually fuse metals together in a process called cold welding.  

It is commonly used in aerospace and electrical engineering, and is widely regarded as one of the best ways to bond metals (and other materials) together.

This may sound impossible, but it is actually one of the most popular welding methods. Let us find out more. 

The working principle of heat-based welding is to effectively make the parts have sufficient plasticity, so that different media can be used for atomic diffusion between or between two workpieces. Although this is traditionally done by heating, there are other ways to induce atomic diffusion. 

Cold welding (also called cold pressure welding and contact welding) uses pressure instead of heat under vacuum conditions to connect two materials through a solid-state diffusion process.

It can also be used to bond other materials (such as plastic) together.

However, this raises the question of "Is the cold weld strong?" It turns out that it is.

Once the process is complete, the resulting bond is usually as strong as the bond strength of the base material.

During this process, there is no metal liquefaction, and the material is usually not heated to a significant degree. However, the process does rely on the need to first remove any oxide layer from the relevant metal. 

This is mainly because the metal usually contains a surface oxide layer, which acts as a thin barrier on the surface of the material to prevent the diffusion of metal atoms between the metal sheets. 

Under normal conditions, most metals will have some type of oxide layer on their exposed surfaces-even if it is invisible to the naked eye. They may also be contaminated with a layer of other contaminants, such as grease and dust. 

Cold welding overcomes this problem by preparing the metal before welding. The preparation process includes cleaning or brushing the metal to remove the top oxide or barrier layer. 

This usually involves a mix of chemical and mechanical methods. Degreasing, wire brush. And other techniques are used to ensure that any metal surface is as free of oxide as possible. 

As mentioned earlier, any metal to be cold welded must first be free of any oxide layer.

Once the desired surface cleanliness is achieved, the two materials will be mechanically pressed together with just the right amount of force. The magnitude of this force depends on the material itself, because some materials may only be welded under high pressure. 

But there are other requirements. 

One of the conditions required for cold welding is that at least one of the materials must be ductile and must not be severely hardened. This obviously narrows the range of candidate materials for cold welding.

Soft metals, such as aluminum or copper, are the best choice for cold welding.

The most common joints for cold welding are:

In butt joints, there is usually no need to remove the metal barrier layer, because the plastic deformation that occurs during the connection process will automatically destroy the barrier layer. This type of connector is most commonly used for metals, such as aluminum or copper wires with a diameter between 0.02 inches (0.5 mm) and 0.4 inches (10 mm). 

On the other hand, lap joints do require special treatment, otherwise the materials will not stick to each other. Lap joints are more commonly used to weld plates together or to weld plates to rods. 

Cold welding is also commonly used for wires, including aluminum, copper, zinc, 70/30 brass, nickel, silver, silver alloys, and gold.

Cold welding was first officially recognized in the 1940s, but there is evidence that its origin may be earlier. 

For example, in 1724, the priest JI Desaguliers seemed to have successfully cold welded two metals using cold welding techniques. He showed that when he pressed two shot balls of the same diameter together and twisted them together, they would stick together. The joint is somewhat unstable, but it seems to be as strong as the joint of a female lead shot. 

Although cold welding is useful, it is far from unlimited—just like any form of welding. 

It is difficult to achieve perfect cold welding. This is caused by a variety of reasons, including the oxide layer formed on top of the metal under atmospheric conditions, surface irregularities, and surface contamination. Perfect conditions can be difficult to achieve and costly, especially for large welding projects.

Optimal cold welding can only be achieved when the two surfaces pressed together are clean and free of any form of contamination. This requires additional preparation steps and may take some time to achieve.

In addition, the flatter and regular the surface, the easier and more uniform the welding. Perfectly flat and smooth surfaces are not always possible-especially on the micro and nano scales. 

Another limitation is the type of metal that can be cold welded. At least one of them must be malleable, and non-ferrous soft metals are the only candidate materials that are truly suitable for cold welding. Copper and aluminum are the two most commonly used cold weld metals.

Metals containing carbon are usually excluded from the possibility of cold welding.

The most significant advantage of cold welding is that the resulting weld has the same or very close bonding strength to the base metal. Without complete melting and recasting, it is difficult to reproduce this feat in other forms of metal processing. 

Cold working can also be used to weld 2xxx and 7xxx series of aluminum alloys. These aluminum alloys cannot be welded because they are prone to thermal cracking and are difficult to connect with other forms of welding.

In the industry, cold welding is known for its ability to weld aluminum and copper together. These aluminum and copper are often difficult to weld with other forms of welding techniques. However, the bond between the two materials produced by cold welding is very strong. 

Cold welding provides clean and strong welds without the formation of brittle intermetallic compounds. 

Cold welding is mainly used for welding wire. Since no heat is involved and the process can be completed quickly, cold welding can ensure perfect welding of wires, mainly aluminum, copper, 70/30 brass, zinc, silver and silver alloys, nickel and gold.

There are even hand-held tools that can be used for cold welding wires, making them very portable and easy to use-of course, once the metal surface is sufficiently cleaned.

Cold welding is also used when different metals must be joined, such as between copper and aluminum.

Cold welding provides one of the strongest welds and can be used to create a bond similar to the parent metal. It does not require heat or special tools. Among the most popular welding techniques, cold welding indicates that if you want to connect a specific type of material, you don't need to heat it.

By subscribing, you agree to our terms of use and privacy policy. You can unsubscribe at any time.

By subscribing, you agree to our terms of use and privacy policy. You can unsubscribe at any time.