Cut and pasted from elsewhere:
Casting is the process where metal is heated until molten. While in the molten or liquid state it is poured into a mold or vessel to create a desired shape.
Forging is the application of thermal and mechanical energy to steel billets or ingots to cause the material to change shape while in a solid state.
The casting process is useful for a wide range of wearparts and components that are too large, complicated, intricate or otherwise unsuitable for the forging process.
The advantages of casting include:
- No real upper size limit in casting weight
- Large range of alloy choices
- As forgings remain solid, custom alloys are far more difficult to get into production whereas with casting, alloys including Chrome, Nickel and Moly can be added at the molten stage.
- Tooling is often less expensive than forge dies
- Smaller production “runs” required
- Complicated/complex parts are no problem
Forging offers uniformity of composition and structure. Forging results in metallurgical recrystalisation and grain
refinement as a result of the thermal cycle and deformation process. This strengthens the resulting steel product particularly in terms of impact and shear strength.
Forged steel is generally stronger and more reliable than castings and plate steel due to the fact that the grain flows of the steel are altered, conforming to the shape of the part.
The advantages of forging include:
- Generally tougher than alternatives
- Will handle impact better than castings
- The nature of forging excludes the occurence of porosity, shrinkage, cavities and cold pour issues.
- The tight grain structure of forgings making it mechanically strong. There is less need for expensive alloys to attain high strength components.