Forging Versus Casting
While forging and casting can both produce near-net shape parts, they are two completely different metal-forming processes. The characteristics of the parts produced in each process are also different.
If you’re sourcing metal components, it’s important to understand the capabilities of each forming process. In this article, we’ll take a closer look at forging and casting, how they differ, and how to choose the best method.
Forging is a deformation process where a billet or preform is manipulated (pounded, squeezed, hammered, etc.) and shaped under pressure.
Many metals can be forged, including carbon steel, stainless steel, and steel alloys, although differences in composition and properties will influence which forging process is used. There are many forging processes, including, but not limited to, hot forging, cold forging, warm forging, impression die forging, and press forging. You can view our blog post here to learn more about the various forging methods.
Regardless of the particular method used, forging doesn’t add or remove material, so the resultant form has the same weight and volume as the billet until the part is trimmed from the platter.
One of the biggest advantages of forging is its effect on alloy structure. All metals are composed of grains, and how they interlock is a significant factor in their strength and ductility. Manipulating a metal blank by forging stretches these grains in directions perpendicular to where the force is applied from. This increases strength, sometimes dramatically, from its original state.
A second benefit of deformation is a dramatic reduction in internal defects like porosity and alloy segmentation.
Other advantages of forging include:
Forging is not without its limitations. There are two primary constraints:
Casting is where metal is melted, poured into a cavity shaped like the final component, and allowed to solidify. Cavities can be produced as expendable molds used once or as permanent molds. Sand and investment casting are expendable mold casting processes, while gravity and die casting use permanent molds. Molds require channels for metal to flow into the part cavity and “risers” that act as reservoirs as metal contracts during cooling.
Internal cavities are created with cores; the cores are placed in the mold before the metal is poured. After the metal solidifies, the cavity is broken apart as the final component is released from the mold.
All types of casting produce near-net shape parts, although the level of detail reproduced and the amount of metal to be machined away depend on the process used. Sand casting is the least precise, while investment casting, in particular, is capable of fine detail and smooth surface finishes.
Any metal can be cast, but oxidation can be a problem. This is addressed through vacuum melting and pouring, which adds to the complexity of the equipment needed.
Casting processes have a lot of versatility. Key advantages are:
There are many situations and types of parts for which casting is not optimal.
Particular issues include:
Selecting a metal forming process requires an application evaluation.
Forging is generally more cost-effective, less wasteful, and faster than casting, produces stronger components, and is great for small- and high-volume orders. Forgings are typically preferred for applications requiring high wear resistance or components expected to perform well in stressful environments. However, forging may not be the best option for extremely large, complex components or if the application requires using a material that cannot be forged.
General applications for forged parts include automotive components like connecting rods and crankshafts, power transmission parts like crown wheels and pinions, and parts for marine, defense, forestry, and mining applications.
Comparatively, casting processes, especially investment casting, are ideal for producing lightweight, complex, thin-walled parts with exceptional surface finish and heavier components weighing over 100 pounds. But defects are more common in castings than forgings, and the tooling creation process generally takes longer to complete.
Casting processes are commonly used to produce engine blocks, pistons, pipes, valves, and other components for aerospace, automotive, and industrial applications.
Founded in 1967, Trenton Forging is an industry-leading forging manufacturer specializing in impression die forging. We can produce asymmetrical and symmetrical forgings from steel, stainless steel, steel alloys, and microalloyed steels for clients in many industries, ranging from defense and automotive to agriculture and forestry.
If you’d like to learn more about the advantages of forging, please visit our blog for additional resources. If you need forged components or want to discuss a project with us, please fill out our online form today.
