Difference between Fusion Welding and Solid State Welding

Fusion Welding

The welding process that uses heat to join (or fuse) two or more materials by heating them to their melting point is known as fusion welding. The fusion welding process may or may not require the use of filler material for welding. Examples of the fusion welding are arc welding, gas welding, resistance welding, etc.

Solid State Welding

The welding process in which two workpieces are joined under a pressure providing an intimate contact between them and at a temperature essentially below the melting point of the base materials is known as solid state welding. The materials being joined without the addition of the filler material. In the solid state welding, the metals are joining in the solid state and hence, no change takes place in state of the base metals. Friction welding, roll welding, diffusion welding, etc. are the examples of solid state welding.

Differences between Fusion Welding and Solid-State Welding

The following table highlights the differences between fusion welding and solid state welding −

Fusion WeldingSolid-State Welding
In fusion welding, the surface of the base metals are fused to form coalescence during the welding process.In solid state welding, there is no melting of the base material.
The base material is heated to its melting point to make the weld.The base material is heated to the temperature below their melting point.
Fusion welding requires heat during the welding process.Solid state welding does not require heat, but it requires mechanical pressure for welding.
In the fusion welding, intense heat is produced which affects the mechanical and metallurgical properties of the base materials.In case of solid state welding, the mechanical and metallurgical properties of the base materials do not change because of the less heating.
In fusion welding, the filler material can be applied easily.In solid state welding, no filler material is applied.
With fusion welding, the joining of dissimilar metals is a challenging task. It becomes more challenging, when they have different melting points and thermal expansion coefficients.As the solid state welding process does not involve the melting and solidification. Therefore, the joining of dissimilar metals is comparatively easier.
In fusion welding process, there is excessive heating which results in a noticeable heat affected zone surrounding the weld bead.In the solid state welding process, the heat affected zone is usually not noticeable or a narrow heat affected zone may occur in some cases.
In fusion welding, the joint design, edge preparation and surface preparation are not crucial.The joint design, edge preparation and surface preparation, etc. are important parameters because the solid state welding process requires specific melting surface.
Due to excessive heating, the distortion in the fusion welding process is very high.In solid state welding, the distortion is small.
Fusion welding involves the change of state of the base metal, i.e. solid to liquid and then liquid to solid.In solid state welding, no state change occurs, that is the joining of the metals takes place in solid state.