What Is Cold Welding & How Does It Work?

Cold Welding Explained

What comes to mind when you think of welding? Blue-hot flames? Sparks? Molten, magma-like metal?

These elements may be common for most welding techniques, but not for cold welding methods. Cold welding, also known as solid-state welding, requires little to no heat and uses vacuum pressure instead of pressure and heat. Cold welding is commonly used to make butt or lap joints between aluminum and copper wires, especially for smaller-diameter wires. The process of cold welding involves cleaning the metals, smoothing surface irregularities and pressing the metals together with equal pressure to create a uniform metal bond. The benefits of cold welding include lower risk of heat-affected zones, clean and strong welds, the ability to weld different metals without melting them and the ability to weld smaller-diameter aluminum wires.

If you’re thinking of becoming a welder, whether that’s with cold welding techniques or otherwise, consider the following statistics on welding industry demand, from the Bureau of Labor Statistics (BLS):

• There are more than 45,000 estimated average annual welding job openings in the U.S.⁴²
• Total welder employment is expected to exceed 463,000 by 2033.⁵⁰

Cold welding could be an exciting career path. UTI offers a Welding Technology training program that teaches students essential welding processes, including cold welding, and provides state-of-the-industry equipment and tools for hands-on learning.¹

However, you should first understand what it is, what it’s used for and how it works. Keep reading to learn more!

What Is Cold Welding?

Cold welding is also known as solid-state welding. It’s called “cold” welding because it requires little to no heat.

Welding usually uses high heat and pressure to transform metals. On the other hand, cold welding uses vacuum pressure rather than pressure and heat.

What Is Cold Welding Used For?

Cold welding techniques are commonly used to make butt or lap joints, typically between aluminum and copper wires. Hot welding has more uses than cold welding but is generally unsuitable for this task.

That’s because thermal energy, also known as heat, is used in hot welding techniques. However, molten metal can easily result in a messy and inefficient weld, especially with fragile, thinner materials like metal sheets and wires.

Wires of smaller diameter can be welded with portable cold welding machines. However, wires of larger diameter often require pneumatic (air-pressure driven) cold welding technology, including industrial cold welding machinery.

Read: Welding Joint Types: Butt, Lap, Edge Joints & More

How Does Cold Welding Work?

Cold welding is mostly done on aluminum and copper wires, but precious metals like gold and silver are also included. To perform a cold weld successfully, welders must first prepare their materials.

1. Clean metals

Cleaning metals prevents them from oxidizing, or rusting. This is usually done with grease, a wire brush or another chemical oxidation removal method. Otherwise, rust can block access to pure metal and impede the weld.

2. Smooth surface irregularities

Metal materials with surface irregularities are difficult to weld together. That’s why cold welders may smooth out any bumps or nicks with mallets, hammers or larger-scale machinery.

Start welding

Using no heat or a third filler metal material, metals are pressed together with equal pressure from both sides. This process produces uniform metal bonds and ensures complete surface contact. The resulting joint is called a “flash.”

What Are the Benefits of Cold Welding?

As previously stated, most welding tasks require thermal energy from hot welding. Cold welding, on the other hand, has a few distinct advantages!

Lower HAZ risk

Heat-affected zones (HAZ) are unmelted areas of metal whose properties have been altered by heat. These alterations can degrade the base metal materials, which can impact their structural integrity. Because cold welding uses little to no heat, it has a lower HAZ risk.

Clean and strong welds

Since cold-welded metals don’t go through a molten or liquid phase, no liquid metals are pushed out of joints. Because there is a lower chance of HAZ, cold-welded materials are stronger after welding. Cold-welded joints are also much easier to trim cleanly.

Welding different metals

Welding different metals is typically difficult due to their differing properties, particularly their melting points. Cold welders don’t face this disadvantage because cold welding doesn’t involve melting metals.

Aluminum welding

Certain diameters of aluminum wire can’t be welded without cold welding techniques. As a result, cold welding has become an indispensable welding method for projects requiring aluminum wires of smaller diameter to be welded.

Read: How to Weld Aluminum: The Beginner’s Guide

History of Cold Welding

Cold welding has been used for centuries, dating to 3300 B.C. However, it wasn’t recognized as a welding principle until the 1940s to 1950s.

In 1724, the Rev. John Theophilus Desaguliers tested the theory of cold welding by holding two lead balls together and twisting them. He found that they stuck together which proved the concept of cold welding.

Start Pursuing a Cold Welding Career!

Cold welding isn’t the easiest welding process. However, for many welders this isn’t a drawback. In fact, the process’ unique challenges and benefits are exactly what excites them!

Technical training is a great way to gain technical skills that can be applied to various welding trades. UTI’s 36-week Welding Technology program provides comprehensive hands-on learning to help equip students with the technical knowledge they need to train for welding careers — and even potentially pursue careers as cold welders.

When you’re ready to start learning, request more information and apply to our welding school!