Difference Between Fusion Welding and Solid State Welding

Welding is one type of manufacturing process by which two or more similar or dissimilar materials can be joined permanently by coalescence formation with or without the applications of external pressure, heat or filler material. Fusion of faying surfaces of parent materials is not necessary for weld bead formation. On the basis of whether base materials fuse or not, welding processes can be broadly classified into two groups—solid state welding and fusion welding.

When faying surfaces of parent materials along with filler material melt down to form weld bead, it is termed as fusion welding. Sufficient heat must be applied from some shorts of external source in order to fuse faying surfaces of base metals properly. On the other hand, if no melting takes place during welding, then it is termed as solid state welding. However, in solid state welding, parent parts may be heated to an elevated temperature (but substantially below its melting point). Instead of external heat, application of pressure is necessary for this type of welding. Following passages elaborate similarities and differences between fusion welding and solid-state welding. You may also read following articles.

Similarities between fusion welding and solid-state welding

  • Both fusion welding and solid-state welding provide permanent joints.
  • Coalescence or weld bead is formed in both the cases.
  • Both can produce sound joint, if carried out properly.

Differences between fusion welding and solid-state welding

Fusion welding Solid-state welding
Faying surfaces of base metal are fused to form coalescence. Filler metal, if used, is also fused. No such melting takes place. However the base metal may be heated to an elevated temperature but below its melting point.
Heat must be applied for welding. Heat can be supplied by various means such as electric arc, fuel-gas flame, resistance heating, laser beam, etc. No external heat source is required but pressure may be applied externally for welding.
Filler material can be applied easily. Usually no filler is applied.
Because of melting, palpable HAZ (heat affected zone) exists in the welded components. HAZ is usually not noticeable.
Mechanical properties of parent materials are affected by intense heating. Mechanical properties usually remain unaltered.
Dissimilar metal joining by fusion welding is challenging task, especially if the duo have substantially different melting point and coefficient of thermal expansion. Joining dissimilar metal is comparatively easier as processes don’t involve melting and solidification.
Level of distortion is very high with fusion welding. Solid-state welding causes minimal distortion.
Joint design and edge preparation are not crucial. These parameters mainly influence achievable penetration. It requires special type of joint design and edge preparation. In few cases, very smooth surfaces are required.
Examples of fusion welding processes:

  • Arc welding (SMAW, GMAW, TIG, SAW, FCAW, ESW, etc.)
  • Gas welding (AAW, OAW, OHW, PGW)
  • Resistance welding (RSW, RSEW, PW, PEW, FW, etc.)
  • Intense energy beam welding (PAW, EBW, LBW)
Examples of solid-state welding processes:

  • Cold Welding (CW)
  • Roll Welding (ROW)
  • Pressure Welding (PW)
  • Diffusion Welding (DFW)
  • Friction Welding (FRW)
  • Friction Stir Welding (FSW)
  • Forge Welding (FOW), etc.



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