Definition of Cold Welding and Its History
As you may guess from the name, cold welding uses little to no heat to weld non-ferrous metal together. However, the processes used in this welding method aren’t that simple. It’s an interesting materials science, and this article will explain why.
Because the cold welding method doesn’t use heat, the metals are never molten and, therefore, always solid. Instead of heat, metallurgists use pressure to weld metal pieces together. There’s no phase during which the metal is liquid. So in some ways, it’s simpler than liquid-state welding, but some processes and details must be fleshed out and explained.
For example, let’s take pressure. How would a metalworker apply pressure to ensure the cold weld is strong and durable? Well, as the parent metal workpieces are joined together, the distance between the two decreases to what’s finally a negligible amount. At this point, metal atoms jump back and forth across the joint and seal the new piece in a near-perfect bond.
Cold welding dates back to the 1940s, but some sources say it has an even earlier history. For example, in 1724, a man named Reverend J. I. Desaguliers appeared to have used the predecessors to cold welding techniques, if not de facto techniques themselves.
He pressed and twisted together two lead balls of the same diameter and demonstrated that they would adhere to one another. While the weld wasn’t very consistent, the principle still stood, and the joints were as strong as the parent metals.
How Cold Welding Works
Let’s go into a little more depth about some of the physics behind cold welding.
The primary forces in cold welding are pressure and mechanical rolls and dies. All these produce consistent and near-perfect cohesion. That is why cold welding is sometimes known as contact welding.
Now, it’s essential to understand certain factors that affect the success of adhesion. As a technique with inherent limitations, cold welding needs to be bolstered by some crucial elements. These include properly cleaned and brushed surfaces, lack of oxygen contact, and malleable metal parts. In addition, ensuring proper alignment of the joints’ geometry is critical.
So what are these types of malleable metals? Well, they include aluminum, 70/30 brass, copper, silver (including various silver alloys), nickel, gold, and zinc. Also important to note is that cold welding is especially effective for joining dissimilar metals that would otherwise be difficult to weld. Cold welding is generally the most conducive to welding wires (made of some of the abovementioned materials).
Applications and Advantages of Cold Welding
Cold welding is used the most advantageously in the electronics, aerospace, and automotive industries.
Now we can examine cold welding's benefits and drawbacks.
- No HAZ (Heat Affected Zone). Cold welding work doesn’t produce heat, preventing chemical or mechanical changes that could affect the base metals being welded.
- Strong and clean welds. Cold welding is precise and durable, preventing the formation of intermetallic compounds at the join.
- Efficacy at joining dissimilar metals. As mentioned above, cold welding can take otherwise difficult-to-weld dissimilar metals and join them relatively easily.
- Welding aluminum and its alloys. Cold welding can join different formulations of aluminum, which is otherwise difficult to do in other welding processes.
- You must ensure that the metal surface of the parent metals is smooth and clean with no oxide layer to create a successful cold weld. This can prove tricky in high-volume industrial production settings because it takes time to clean and de-oxidize the metal parts properly.
- Limitations on material types. Only malleable metals can be used in the cold welding process, so those that have undergone severe hardening or aren’t intrinsically ductile are not possible to cold weld.
- Shape of the material. You need to ensure that your parent metal workpieces are evenly shaped and structured; those with surface irregularities or unusual shapes will not be suitable for cold welding work.
1. Does cold welding produce a permanent bond?
Yes. If all conditions are met, the cold welding process can produce high-performance, durable, permanent bonds as strong as heat-based welding.
2. What materials can be cold welded?
You can cold weld aluminum, brass and brass alloys, silver and silver alloys, copper, zinc, and nickel – particularly in the form of a wire.
3. Can the cold welding technique be used for large-scale projects?
The cold welding technique is most conducive to smaller projects, as you must factor in various conditions to weld your materials properly. However, it can be done if you have enough of a workforce.
4. What are some potential challenges with a cold weld?
You must ensure each metal surface is clean, regularly shaped, positioned, brushed, and de-oxidized. If they’re not, your cold weld won’t be as effective or successful. You also can’t weld metals that aren’t sufficiently ductile or malleable. Beyond these preconditions, you’re mostly set!