Cold welding is a bonding process that uses pressure instead of heat to combine two metals, but not all metals are suitable. It is best for objects in space due to its limitations. Cold welding has been around for thousands of years and can be performed with less force or by raising the surface temperature. It allows for working in hostile environments but is difficult to verify the integrity of the weld.
Cold welding is a bonding process in which two elements are combined into one through intense pressure applied by dies and rollers. As the name suggests, this technique does not rely on heat to change the state of the elements to be bonded: these substances remain in a solid state throughout the procedure. Not all metals are ideal candidates for cold welding due to the oxygen content within their outer layers, and even after extensive brushing and cleaning, metals will not bond if one of them is not malleable. Likewise, if the two bonded pieces are subsequently exposed to an oxygen-rich environment or other reactive compounds, the cold weld will fail. Because of these limitations, the cold welding process is best suited for objects that will be deployed outside the Earth’s atmosphere, such as satellites or spacecraft.
Cold welding was first discovered by modern societies in the early 1940’s and considered a new phenomenon, but this process has been around for thousands of years. It has been learned that two pieces of similar metal will bond together within a vacuum as long as they possess clean, flattened surfaces and a strong initial force can be applied. During the process, deformities occur on 60-80% of the bonding surface and this allows the contact of pure and clean metals. The permanent bond then occurs at the atomic level, with far stronger welds than could be achieved by other means. Another plus is that there are absolutely no intermediate materials used as a type of weld, so until the oxides are allowed to reform on the metal surface, it should last for decades.
Since the initial period of discovery, researchers have demonstrated that cold welding can be performed even without excessive force. By applying less pressure over a longer period of time, similar results can be achieved. Another method is to raise the surface temperature of the two materials to be bonded for a short time to accelerate the molecules.
The modern uses for cold welding are numerous, but it is still definitely considered a situational process due to the limitations mentioned above. However, the technique allows working in many previously impossible hostile environments, such as the welding of underground pipes carrying flammable gases. Another drawback is that because welding occurs quickly and is considered permanent, it is very difficult to verify the integrity of the weld, especially in thicker metals.
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