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Is “Cold Welding” The Same As Cold Spray?

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When we think of welding, the very first thing that springs to our mind is HEAT. Heating metals to their melting point and fusing them is how most welding techniques work. Cold welding, however, refers to the process of joining two workpieces at room temperature. The joining’s strength is somewhat close to “normal” welding: The binding is permanent and can usually only be reversed by damaging the workpieces.

In this blog post, let’s take a closer look at what cold welding is – and why it’s NOT the same as cold spray.

Unlike cold welding, VRC Cold Spray solutions can make industrial repairs “as good as” or sometimes “better than new” requirements. Contact us to find out how VRC Cold Spray technology can benefit your metal repairs.

What Is Cold Welding?

While welding is often associated with hot, fiery sparks and molten metal, some welding processes do not fit this visual.

One of the most notable of these different welding processes is called “cold welding.” It has been used in industrial settings for nearly a century and has several advantages that other welding processes do not possess.

Cold welding is defined as a solid-state welding process that requires little to no heat to join together two or more metals. Instead of heat, the energy used to merge the materials comes in the form of pressure, so this process is sometimes called contact welding or cold pressure welding. During cold welding, no metal is liquified or even heated to a notable degree.

How can cold welding bond two metals together without heat? It is because of the removal of the layers of oxide on the surfaces of the metals; this removal exposes fresh metal. We will describe how this is key.

What oxides? Almost all metal materials in normal conditions have some type of oxide layer.

Rust is a well-known type of oxide layer on iron, but in many cases oxide layers may not be visible to the naked eye, and they may even be beneficial. Aluminum, for example, oxidizes in air very quickly. The oxide layer then protects the aluminum from further oxidation, making it corrosion resistant. The appearance is virtually unchanged, however. Fresh, un-oxidized aluminum is a little brighter than oxidized aluminum, but the difference is nothing like fresh vs. rusted iron.

The metal oxides not only prevent further corrosion of many materials, they also are barrier that prevents the metal atoms on each of the materials from being compressed together and eventually bonding. However, once the oxide layer is removed from the metal pieces, the metal atoms can join each other when clean surfaces are put against each other with enough pressure. When metal atoms “see” each other without any oxide barriers between them they can join together very tightly, and the resulting bond is very strong.

How do you remove the oxide layer? To remove the metal’s oxide layer, various chemical and mechanical methods are used. Degreasing, wire brushing, acid etching, and other techniques ensure that the metals’ surfaces are free from all contamination and oxides.

In addition to being oxide-free, the metals must also be somewhat malleable. Ductile metals include aluminum, copper, brass, and magnesium alloys. To a lesser degree, these metals can be included in the list also: zinc, lead, tin, nickel and titanium alloys, and refractory metals.

Metals and alloys that contain carbon in their composition are not able to be joined using cold welding.

Heavy-duty industrial machinery creates the pressure needed to develop the metallurgical bonds of cold welding.

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Cold Welding Applications

Typically, the cold welding process creates butt or lap joints. Cold welding is also often used for joining wires together.

One of the most common instances of cold welding is when joining dissimilar metals. When different metals are traditionally welded or melted together, they do not “join” or meld well. This incompatibility can result in the metals not joining together at all.

It can also lead to weak or cracked welds. Cold welding avoids these problems as it relies only on the atomic bonds formed through intense pressure.

Industries that use cold welding include:

  • advanced fabrication applications
  • aerospace
  • automotive
  • laboratories

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Advantages of Cold Welding

One of the most significant advantages for most users of the cold welding process is that there is no heat-affected zone. This lack of a heat-affected zone reduces the risk of the most damaging chemical and mechanical changes to the materials during the cold welding process.

Another critical advantage of cold welding is the ability to join dissimilar metals, as noted above.

One last advantage we would like to mention is that if cold welding is performed correctly, it creates a weld that is at least as strong as the weakest parent material.

Disadvantages of Cold Welding

The primary disadvantage of cold welding is that the materials must be immaculately clean and oxide-free to create a satisfactory weld. The parts to be joined must also be very smooth. This level of cleanliness can be difficult to attain, especially for metals that oxidize quickly. It can also be an expensive process and difficult to implement in a high-volume setting.

Since at least one of the metals being joined must be ductile, the cold welding process is limited by what metals or alloys can be joined together.

What Is A Great Alternative To Cold Welding For Metal Repairs?

Cold welding and cold spray are both solid-state processes that happen in the absence of high heat, avoiding the formation of a heat-affected zone. The ability to “join” dissimilar metals is also a similarity; however, the “joining” process is different and the applications are different. Cold welding is used to join parts together, while cold spray is primarily a means of depositing material.

Cold spray relies on high kinetic energy and deformation of small (human-hair diameter) particles, and does not require the extreme cleanliness that cold welding does. It can also be applied to a wide range of geometries, and it can also be used to create coatings of mixed materials, such as metal and ceramic blends.

Unlike cold welding, VRC Cold Spray solutions can make industrial repairs “as good as” or sometimes “better than new” requirements. Contact us to find out how VRC Cold Spray technology can benefit your metal repairs.

Contact VRC Metal Systems

Call, email, snail mail or visit the VRC Metal Systems offices today to talk to a representative about how your business can benefit from our cold spray systems and service.

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605.716.0061

VRC Metal Systems
600 N Ellsworth Rd
Box Elder, SD 57719

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