Filed under: Forged vs Cast
Forging and casting processes are often confused, one with the other. To the untrained observer, the appearance of a forging compared to a casting may be similar. Surface appearances can be misleading. The significant differences lie under the surface, in the metallurgical structure, each process contributes to the finished part. An understanding of the differences between forging and casting will allow an engineer to design the component best suited to the service performance both desired and required for a manufactured product. Forged vs. Cast products undergo different processes and methods that give them varying levels of strength.
Forging is the process of plastically deforming a material while in a solid state. The application of force causes significant redistribution of the mass into a more useful configuration while enhancing the metallurgical properties. Impression die forgings are generally produced by pressing or hammering materials between dies into which cavities have been machined. Open die and ring roll forgings also utilize tooling to allow shapes nearer to the net result, but all forging involves solid material flow under pressure. Before forging materials, there are some strengths and weaknesses to consider.
Advantages of Forging
- Forging refines and redirects anisotropic grain flow, conforming the inherent raw material flow lines to the shape of the part, providing tensile strength.
- Forging drives dynamic recrystallization in the microstructure, enhancing fatigue properties and impact toughness.
- Forged metal products have more consistent microstructure, providing reliable machinability.
- Machining hours are cut down saving time and money.
- The forging process generally works for most metals including ferrous and non-ferrous.
- Forging results in more efficient inspections and manufacturing
- Forged products contain no gas pockets, voids, or shrink defects that can lead to product failure.
- “Wrought Properties”, the standard other processes seek to achieve, are the properties achieved by forging.
- The mechanical properties are is improved with forging.
- Porosity is eliminated by forging.
- While net and near-net forging processes are possible in some materials and for some configurations, forging is limited to geometry of forming between tools and dies. Complex configurations with internal cavities and voids either cannot be produced/forged or will require subsequent machining.
- Size limitations on different types of products may occur due to the equipment size and capacity.
- Raw materials are generally limited to those commercially available alloys that can be obtained from raw material producers in ingot, billet or bar form as input to the forging process.
Casting is a process in which a material in liquid form is poured, injected under pressure, or drawn by vacuum into a mold. With molten metals, after the mold is filled the casting must cool and solidify. The casting is then removed from the mold. In the case of hard molds, such as in sand, shell, or investment processes used to cast metals, the mold is used once and must be broken to release the casting. In the case of permanent mold castings, such as die casting, the dies containing the casting are separated to free the casting, then cleaned and prepared for the next casting to be made.
Advantages of Casting
- Large design freedom to create complex configurations.
- Some casting processes provide close tolerance, net shaping.
- Casting provides the option of using cores or inserts which allows internal cavities and voids
- Alloy design/selection may be larger.
- When the finished component is used only in static compression suffer few metallurgical weaknesses.
- Lower cost tooling for small volume production
- The casting process can be applied to a large variety of materials.
- With material in liquid form, inclusions of foreign matter from the environment or the mold may become part of the casting.
- Voids and defects may appear in the microstructure due to entrapped gasses.
- As metal cools from liquid to solid, shrink defects and residual stresses that weaken the finished component may result.
- Residual stresses and variations in microstructure can create problems in subsequent machining and heat treating.
Queen City Forging is ready to assist your design and production of components that require consistency, strength, and durability. Parts that must not fail in critical applications, that provide safety and security to end users, that have Wrought Properties, are FORGED parts. Call us to help you create exceptional products that create maximum value for your end user.