Solid-state welding processes require no external heat or filler metal, and materials stay in a solid state throughout the entire welding process. These processes also require different types of welder machines.
Here are four types of welding processes that maintain materials in a solid state.
4. Diffusion welding
Diffusion welding is a process in which the atoms of two pieces of metal combine under high pressure and temperature. This high pressure starts diffusion between the surfaces of welding plates.
This method can join similar and dissimilar metals and is commonly used in the aerospace industry. It also is less prone to plastic distortion than other welding processes. However, it is also a time-consuming process that is difficult to use for mass production.
5. Friction welding
Friction welding is a solid-state welding process that uses friction between two surfaces to be joined to generate heat. This heat melts the surfaces, which creates a weld.
There are several types of welding using friction, which include:
- Continuous induced friction welding
- Inertia friction welding
- Linear friction welding
- Linear vibration welding
- Friction surfacing
Friction welding can produce high-quality welds quickly, requiring fewer supplementary materials, less time, and less skill than other types of welding. However, the cost of setting up a friction welding system is very expensive.
6. Ultrasonic welding
Ultrasonic welding is a solid-state welding process that uses high-frequency sound waves to create heat and melt the metals being joined.
All ultrasonic welding systems will include:
- A press, usually with a pneumatic or electric drive — Assembles the parts under pressure
- A nest, anvil, or fixture — These parts are placed and allow a high-frequency vibration to be directed to the interfaces
- An ultrasonic stack — This is composed of a converter or piezoelectric transducer, an optional booster, and a horn tuned to resonate at the same ultrasonic frequency (typically 15, 20, 30, 35, or 40 kHz)
- A controller — Controls the movement of the press and flow of the ultrasonic energy
Ultrasonic welding is useful in industries that use thermoplastics and materials like polypropylene. Using this method is very quick, safe, and reliable. However, it can only be used for smaller materials (joints cannot be larger than 150mm), and the cost of setting up an ultrasonic welding system is also very expensive.
7. Explosive Welding
Explosive welding is a solid-state welding process that uses a controlled, explosive charge to create enough energy to weld two pieces of metal together.
This welding process is mainly used for cladding processes and is suitable for nearly all kinds of metals and alloys. It is very time-efficient, making it suitable for mass production. However, it is also a high-energy process that can be dangerous if not done correctly.