We generally associate welding with heat. But there is a unique welding method available called cold welding, where no heat or very little heat is required. It might surprise many, but cold welding can be used to weld different types of metal comfortably. We will explain everything you need to know about cold welding starting from its working to its different types.
- What Is Cold Welding?
- What Are The Applications Of Cold Welding?
- How Strong Is Cold Welding?
- Difference Between Cold Welding And Hot Welding
- What Are The Metals That Are Suitable For Cold Welding?
- What Are The Variations Of Cold Welding?
What Is Cold Welding?
The cold welding is a process of welding where there is no heat requirement. This means the metal pieces stay in solid state and not in molten state. Instead of heat, the process involves pressure to bind metals. The pressure brings the surfaces of the objects close for welding. Once the objects are only a few nanometers away, the atoms of the metals bind with one another.
Therefore, the welding is homogeneous and organic. The metal surfaces need to be free of impurities, and the metals should be compatible to bind with one another when they are pressurized and made to come close to one another. Cold welding is widely used for welding aluminum such as aluminum with copper. Cold weld bonding is considered to be near-perfect joint.
What Are The Applications Of Cold Welding?
Cold welding finds its application in various industries starting from automotive and electronics to aerospace and manufacturing. Cold welding is popular for welding wires of different metals. Since no heat is involved in the process, it is widely used in welding underground wire where flammable gases could be present. Besides, it finds application in welding objects that are heat sensitive such as thin containers and explosive items.
Working Of Cold Welding
In this process, metals are joined at room temperature without any heat or electricity. The force is applied to bring the workpieces together. In the process, the atoms of the metal surfaces interact with one another.
But before the cold welding process can begin, you need to remove impurities and oxidized layers from metal surfaces. If not impurities, metal surfaces have oxidized layers. If not removed, the bonding during the welding will not be strong.
When totally cleaned and applied uniform pressure, the metallurgical bond is formed, and the workpieces become one. Cleaning is such a critical step as any irregularity can be fatal in the long run.
There are two main requirements in cold welding process. The most important factor is that the metal surfaces must be crystal clear of impurities. The second factor is the geometry of the workpieces. It is always better if the workpieces are completely flattened such as a wire.
There are different ways to remove impurities such as wire brushing, chemical removal, mechanical removal and even degreasing. In fact, you should get started with degreasing first to remove any oily deposits from metal surfaces. Thereafter, wire brushing removes deep impurities and exposes the real metal surface.
How Strong Is Cold Welding?
Since there is no heat or electric arc involved, there are many who wonder how strong cold welding will be. It can be as strong as the metals are joined through cold welding. This is because it is all about inter-bonding of metal atoms. That is why the strength of the joint in cold welding depends on the properties of the metals that are being joined.
Moreover, if there are impurities, the strength of the joint can get lowered. As a matter of fact, the shape of the workpieces or the joint surfaces can determine the strength of cold welding. Under ideal conditions, cold welding can form strong and durable joints.
Cold Welding Mechanism
There are two types of joints where cold welding mechanism is the best. They are butt and lap joints. The butt joints are applicable in joining wires and pipes. The lap joints are applicable in joining metal sheet.
Cold welding is done through cold welding machines. These machines are hand operated and they are suitable for wires with small diameters. For wires with large diameters, the cold welding machines are electrically operated or pneumatic operated. These machines are highly portable.
Difference Between Cold Welding And Hot Welding
In hot welding, the process involves electric arc, active flame, and fusing metal. In cold welding, the process involves only applying the pressure. The cold welding is applicable to certain metals only but the hot welding is applicable to almost all materials.
|Electric arc required
What Are The Metals That Are Suitable For Cold Welding?
The most popular choices of metals where cold welding is widely applicable are aluminum, copper, lead and zinc. Along with them, alloys of silver, aluminum and nickel as well as soft metal like silver, gold and platinum are welded using cold welding process.
The reason why these metals and alloys are suitable is they tend to crack when they are heated up for traditional welding. Since the heat input is negligible in cold welding, these metals do not crack and form a homogeneous bond.
In short, a metal that is highly ductile in nature can be suitable for cold welding. On the contrary, any metal having carbon atoms cannot be cold welded. Cold welding works that best with metal atoms having cubic arrangements for instant bonding.
What Are The Variations Of Cold Welding?
There are different variations of cold welding available. They differ from the traditional cold welding. We have mentioned them below for your understanding.
Cold Metal Transfer Welding
In this process, an electric arc is used to join workpieces. It is more of MIG welding process than cold welding. But it requires 90% less heat in comparison to the traditional MIG welding process. Since the heat requirement is so low, it is considered to be cold welding.
Technically, it is quite wrong to call it a cold welding process. It involves electric arc and filler wire. It is suitable where the traditional cold pressure welding process is not applicable. But in the real world, the process is expensive as it is performed by automatic machine system.
TIG Cold Welding
Again, this is not traditional cold welding, but there is a MIG welding process available that is performed under cold settings. This means the welding operation follows TIG’s principles, but the input heat is limited. An electric arc is applied for a short time to get the job done.
The temperature of the entire process stays minimal, and heat is also dissipated quickly. It is applicable for welding metal sheets and wires. But instead of this TIG welding, traditional cold welding is suitable for welding thin metal sheets and wires.
In this process, the workpieces are not really welded. They are joined using epoxy, base, and activator. These are mixed to form a paste, and then it is applied to the metal parts. Thereafter, clamps are used to secure the joint for the curing process. Naturally, the bonding is weak in comparison to traditional cold welding. Therefore, it is applicable for minor repairs and welding jobs.
Cold welding is a slightly different mechanism to weld non-ferrous and non-carbon metals. It is safer because no heat and electric arc is involved. That is why it is applicable to metals that are highly ductile and can get damaged by heat. We have clearly explained everything about cold welding starting from the process to the types of cold welding for complete understanding.