Designers often use forging for large or complex parts when suitable bars aren't available or machining is too wasteful. Forging is a good choice when parts need high toughness, strength, and performance.
Why is forging better than casting or directly turning parts? Except large-sized parts and parts with complex shapes that can be obtained through forging,which mentioned above. Forging can also enhance material properties,which has two points:
Firstly, forging can reduce or eliminate metallurgical defects that may exist in raw materials, such as cracks, hot cracks, hot spots, cold shuts, shrinkage, lack of materials, and inclusions, etc., minimize the porosity of the product, and improve the mechanical properties of the product and the stability of product quality between different batches.
Secondly, forging can make the parts have a good grain flow direction. Most raw materials, like round steel, come from rolling. During this process, the grain structure flows along the center line. In forging, this grain flow bends to match the forged shape. This directional strengthening creates high-quality parts, as shown in the figure below.. The forged parts have good impact resistance and fatigue resistance.
Machined parts, regardless of whether they're made from bars or plates, will always cut off part of the grain flow during the machining process. This is because the grain flow is unidirectional, and the resulting open grain ends make the material more susceptible to fatigue and stress corrosion cracking. Casting, on the other hand, involves pouring molten steel into a mold to create the product's blank shape. Since there's no grain flow during this process, the final product won't have increased directional strength. The following figure provides a comparative schematic diagram of the three methods, making it easier to understand.
Here are some research statistics for reference: when using the same material, forging can increase the strength-to-weight ratio by 20% compared to casting or pure machining. After forging, material properties can improve by 30% in terms of strength and toughness compared to the raw materials. For the same part, the tensile strength of the forged one is 26% higher, and its fatigue strength is 37% higher, than the cast one.Are you tempted?(来源：iMechanics机械)
