When one thinks of welding, the first picture that likely comes to mind is molten metal, orange sparks, and the protective gear that welders must wear while working. In short, you’re probably thinking of something like the image above. However, there are several different forms of welding that do not fit with these mental images. Cold welding is one such example of this. Please continue reading to find out everything you need to know about the process of cold welding, why it’s used, and how it holds up against other welding techniques.
What is Cold Welding?
Cold welding is a type of solid-state welding (SSW) that doesn’t require high amounts of thermal energy to join metal pieces. Instead, the energy involved in this process comes from excessive amounts of pressure used to join metal components together. Compared to the traditional image of welding, cold welding does not involve metal needing to be liquified. Cold welding is also sometimes referred to as either contact welding or cold pressure welding.
Related: Ferrous & Non-Ferrous Metal: What’s the Difference?
How Does Cold Welding Work?
Cold welding can bond two metals without high heat due to the removal of layers of oxide on the metals being joined together. Under most normal conditions, nearly all metals have an oxide layer on them, though the naked human eye cannot see these layers. The oxide and other impurities, such as oil and grease, create a barrier that keeps atoms from one material from being pressed and forced to bond with another.
Oxide layers are removed from metals through a cleaning process that involves wire brushing and degreasing before the welding process begins. After this layer is gone, the two metal components’ atoms can be cold-welded together when enough of the correct amount of force is applied. The amount of force needed to cold weld successfully ultimately depends on the type of metal one is working with. Softer metals tend to be the best choice when it comes to this particular welding technique.
Cold Welding Condition Requirements
- At least one metal used in the process must be ductile and not have undergone severe hardening.
- Metal surfaces must be flat and clean, with the oxide layer removed.
How Strong is Cold Welding?
Cold welding can create solid and stable bonds between the materials involved in the process, even if two different metals are used. It’s essential to note this because it can be quite challenging to combine different metals using other welding techniques. For example, cold welding can be used to weld together copper and aluminum.
If procedures are correctly followed, the resulting cold weld should be at least as strong as the weakest parent material used, and it may end up being as strong as the more robust parent metal.
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Cold Welding: What is it Used For?
Cold welding is used for many things in the realm of construction and engineering. However, the most common cases involve welding wires or joining together dissimilar metals (i.e., aluminum and copper, as mentioned above). When melted, different metals don’t join together nicely and will often lead to cracks or an overall weak weld that is at risk of falling apart. For cold welding, however, this is not the case. Additionally, cold welding is often used to create joints, specifically lap joints and butt joints.
Related: Annealing: Everything You Want to Know
Common Cold Welded Metals
Since ductile metals are typically required to perform an effective cold weld, a few specific metal types are most commonly used. These include:
- Brass alloys
Other metals, such as lead and gold, are also suitable for use in cold welding processes. However, they are not used as regularly as the three metals listed above.
Related: Bronze vs. Brass & Copper [Complete Guide]
The Advantages and Disadvantages of Cold Welding
Several advantages and disadvantages come along with the cold welding process. Here are some of the most common ones that welders, engineers, and other metalworkers should be aware of:
- Cold welding can produce clean, strong welds without allowing brittle intermetallic compounds to form, like in other welding processes.
- There is no heat-affected zone in cold welding.
- Cold welding is practical for joining or welding wires without causing heat issues.
- Cold welding can occur between dissimilar metals.
- Cold welding works with Aluminum 2xxx and 7xxx series, which other welding processes cannot do.
- Conducting a perfect cold weld is very difficult due to several issues, including the oxide layers of metals that need to be removed, surface contamination, and surface irregularities.
- The metals must be oxide-free and completely clean for an effective cold weld to take place.
- Soft, non-ferrous metals are the only metals that can undergo cold welding.
- Non-ductile, brittle metals with hard surfaces can not be used in cold welding.
- It’s not possible to cold weld metals that contain carbon.
- Unintentional cold welding can sometimes occur in space. Instances of this have resulted in a few unfortunate incidents during some of NASA’s space operations. One example includes the Galileo spacecraft sent to research Jupiter during the late 1980s and early 1990s. A primary mobile structure meant to launch an antenna got stuck due to cold welding, reducing the antenna’s efficiency significantly and impeding data collection. This issue necessitated that space scientists develop ways to prevent the threat of unintentional cold welding during space travel.
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