Solid State Welding Processes | Advantages and Disadvantages

SOLID STATE WELDING

Solid state welding is a group of welding processes which produces coalescence at temperature below the melting point of base materials being welded without the addition of brazing filler metal. Metallurgical bond is created without melting the base metals. In this welding, heat may or may not be applied. These processes are sometimes called solid state bonding processes.

This group of welding processes includes the following types:
(i) Cold welding
(ii) Diffusion bonding
(iii) Explosive welding
(iv) Ultrasonic welding
(v) Friction welding
(vi) Forge welding
(vii) Roll welding
(viii) Hot pressure welding.

In all of these welding processes, time, temperature and pressure individually or in combination produce coalescence of the base metal without significant melting. Solid state welding is the oldest welding process and some of them are the newest. One of the solid state welding processes, called friction welding, is shown in Figure 3.1. In this friction welding, one of the workpiece is rotating at high speed and the other is stationary. When the stationary workpiece is forced to rotating workpiece at high pressure, the weld is formed due to friction  between these two surfaces.

solid state welding
solid state welding

Advantages, Limitations and Applications of Solid State Welding

Advantages of Solid State Welding :

1. The base metal does not melt and form a nugget.
2. The metals being joined retain their original properties. Hence, there is no heat 
affected zone problems involved.
3. Metallurgical purity is maintained.
4. Dissimilar metals can be bonded.
5. It eliminates liquid phases.
6. It can be applied at different temperatures and under different stresses.
7. Weld is free from microstructure defects.
8. There is no use of filler material, fluxes and shielding gas required.

Limitations of Solid state Welding :

1. Surface preparation is necessary.
2. Joint design is limited.
3. Elaborate and expensive equipment may be required.
4. Non-destructive inspection is very limited.
5. Equipment is expensive.

Applications of Solid State Welding :

1. Bonding of stainless steel liners in aluminum fry pans.
2.Aluminum cladding bonded to uranium fuel rods.
3. Ultrasonic and thermo-compression bonding in microelectronics industry.
4. Friction welding in aerospace and automotive applications.
5. Intake / exhaust automatic valves.

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