Cold welding, also known as contact welding, is a solid-state welding process that requires little or no heat or fusion to join two or more metals together. Instead, the energy used for creating a weld comes in the form of pressure.
During the cold welding process, unlike with fusion welding processes, no liquid or molten phase is present in the joint as can be seen in other techniques including arc welding, friction welding or laser welding.
What is Cold Welding and How Does it Work?
Cold welding was first recognised as a general materials phenomenon in the 1940s, although the history of cold welding goes back much further.
The basic principle of cold welding is that when two clean, flat surfaces of similar metal are brought into close contact under sufficient pressure, they form a strong metallurgical bond.
This is possible because most metals have an oxide layer on the surface that prevents the metal atoms from bonding.
If this oxide layer is removed by wire brushing, degreasing, or other chemical or mechanical techniques, the metals can be pressed together and the atoms will \”recognise\” each other and join.
The pressure required for cold welding depends on the type and condition of the metals, the surface roughness, and the presence of any contaminants.
Generally, softer and more ductile metals are easier to cold weld than harder and more brittle ones.
Some common metals that can be cold welded include aluminum, copper, gold, silver, nickel, iron, and steel.
Advantages and Disadvantages of Cold Welding
Cold welding has some advantages over other welding processes, such as:
– It does not require any external heat source, filler material, or shielding gas, which reduces the cost and complexity of the process.
– It does not produce any harmful fumes, sparks, or slag, which improves the safety and environmental aspects of the process.
– It does not alter the mechanical or physical properties of the metals, such as strength, hardness, or corrosion resistance, which preserves the integrity and quality of the joint.
– It can be performed in any environment, including vacuum or inert gas, which makes it suitable for applications in space or underwater.
However, cold welding also has some disadvantages, such as:
– It requires high pressures and precise alignment of the metal surfaces, which limits the size and shape of the parts that can be welded.
– It requires very clean and smooth metal surfaces, which may be difficult to achieve or maintain in some situations.
– It may not be compatible with some metals or alloys, especially those that have high hardness, low ductility, or complex microstructures.
– It may not provide adequate joint strength or durability for some applications, especially those that involve high temperatures, stresses, or vibrations.
Applications of Cold Welding
Cold welding has a range of applications across various industries, such as:
– Wire stock and electrical connections: Cold welding is widely used for joining wires, cables, and terminals, as it provides good electrical conductivity and reliability.
For example, cold welding can be used for making insulation-displacement connectors and wire wrap connection.
– Space and aerospace: Cold welding is an ideal process for joining metals in space, as it does not require any heat or gas, and can be performed in a vacuum or inert atmosphere.
Cold welding can also cause mechanical problems in spacecraft, as metal parts can unintentionally stick together due to the absence of oxide layers. For example, the Galileo spacecraft’s high-gain antenna failed to deploy in 1991 due to cold welding of the hinges.
– Nanotechnology and microfabrication: Cold welding can be used to create nanoscale structures and devices, as it can produce near-perfect welds with the same crystal orientation, strength, and electrical conductivity as the rest of the material.
For example, cold welding can be used to join single-crystalline ultra-thin gold nanowires within seconds by mechanical contact alone.
Cold Welding Machines and Equipment
There are various types of cold welding machines and equipment available in the market, depending on the size, shape, and material of the parts to be welded. Some common types of cold welding machines and equipment include:
– Cold welding machine: A cold welding machine is a device that applies pressure to the metal surfaces to create a weld. It can be either manual or automatic, and can have different configurations, such as rotary, linear, or orbital.
A cold welding machine can also have different features, such as adjustable pressure, speed, and time, and digital display and control.
A cold welding machine can cost anywhere from a few hundred to several thousand dollars, depending on the brand, model, and specifications.
– Tig cold welding machine: A tig cold welding machine is a type of cold welding machine that uses a tungsten inert gas (tig) torch to heat and clean the metal surfaces before applying pressure.
This can improve the quality and strength of the weld, especially for metals that are difficult to cold weld, such as cast iron, steel, or titanium.
A tig cold welding machine can also be used for hot welding, as it can adjust the temperature and current of the torch.
A tig cold welding machine can cost anywhere from a few thousand to several tens of thousands of dollars, depending on the brand, model, and specifications.
– Cold welding pen: A cold welding pen is a handheld device that uses a battery-powered electric current to heat and clean the metal surfaces before applying pressure.
It can be used for repairing small cracks, holes, or scratches on metal parts, such as jewellery, watches, or glasses.
A cold welding pen can cost anywhere from a few tens to a few hundred dollars, depending on the brand, model, and specifications.
Cold Welding vs Hot Welding
Cold welding and hot welding are two different types of welding processes that have different advantages and disadvantages, depending on the application and requirements.
Some of the main differences between cold welding and hot welding are:
– Heat: Cold welding does not require any external heat source or filler material, while hot welding does.
This affects the cost, complexity, safety, and environmental aspects of the process, as well as the mechanical and physical properties of the metals and the joint.
– Pressure: Cold welding requires high pressures to create a weld, while hot welding requires low or moderate pressures.
This affects the size and shape of the parts that can be welded, as well as the alignment and clamping of the metal surfaces.
– Environment: Cold welding can be performed in any environment, including vacuum or inert gas, while hot welding requires a suitable atmosphere, such as air or shielding gas.
This affects the compatibility and suitability of the process for different applications, such as space or underwater.
– Strength: Cold welding can produce strong and durable joints, especially for soft and ductile metals, while hot welding can produce weaker and brittle joints, especially for hard and brittle metals.
This affects the performance and reliability of the joint, especially under high temperatures, stresses, or vibrations.
Conclusion
Cold welding is a solid-state welding process that joins two or more metals together without the application of heat or fusion. It has some advantages and disadvantages over other welding processes, and has a range of applications across various industries.
Cold welding also requires different types of machines and equipment, depending on the size, shape, and material of the parts to be welded.
Cold welding and hot welding are two different types of welding processes that have different characteristics and outcomes, depending on the application and requirements.