Modern forging uses massive presses or hammers to compress metal materials in a solid state (but heated to a softened, malleable state) into the desired shape.
During the repeated compression by heavy hammers or presses, the internal grain structure of the metal is refined and compacted, much like squeezing out air bubbles from dough, making it very dense. This grain structure aligns along the shape of the part (professionally called flow lines), making the part particularly strong in the direction of applied force.
Forged parts have extremely high strength, are resistant to fracture under repeated stress, have excellent impact resistance, and are virtually free of internal defects such as pores or shrinkage cavities.
Applicable scenarios: Critical components in aircraft, crankshafts in automobile engines, gears in heavy machinery, etc.
The forging process effectively eliminates microscopic defects within the material, making the quality of the parts very reliable and stable.
Although the initial mold costs and processing costs of forging may be higher, because forged parts are particularly durable and long-lasting, they significantly reduce the number of part replacements, making them more cost-effective in the long run for applications requiring high strength.
Casting has a longer history. It involves heating metal to a liquid state, then pouring it into a pre-made mold, and allowing it to cool and solidify to form the part.
This is the most unparalleled advantage of casting. Because the metal is liquid, it can flow into every corner of the mold, whether it's complex internal cavities or various oddly shaped geometric structures; casting can form them in one go.
Forging is very difficult or impossible when making complex parts with internal holes.
For mass production or parts with extremely complex shapes, casting is usually more economical than forging. This is because the casting process is simple, the production speed is fast, and it does not require massive pressure equipment like forging. The cast parts are very close to the final required dimensions, thus reducing the amount of subsequent machining and saving considerable time and cost.
Casting can be used for almost all metal materials, including some special alloys that are difficult to process by forging, such as cast iron.
| Comparison Dimension | Casting | Forging |
| Forming Principle | Metal is melted into liquid, poured into a mold and cooled to harden | Metal remains solid after heating, shaped by hammering/extrusion |
| Metal Structure | Internal grains are large and disordered, easy to have small holes and sand holes | Grains are pressed to be fine and dense, compact structure without defects |
| Mechanical Properties | Average strength and toughness, can't stand repeated stress and vibration | Strong and tough, durable, able to bear complex forces |
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