[1]It’s an issue that many of us have probably pondered at some point–what is the difference between casting and forging? Loads of companies abide by one or both of these manufacturing processes, but unless you’re intimately familiar with how each one works, it may never occur to you how the process affects the finished product what winds up in your hands.
[2]The blast furnace at Gary Works in Gary, IN.
In this article, we will discuss in some depth what separates casting from forging, as well as a few of the pros and cons you can expect from each manufacturing process.
Some of the pros about casting are versatile size limits, which allow for larger items to be crafted than could be done through forging, as well as obviating the use of complicated and expensive pieces seen in forging, such as tooling and machinery. On the flipside, casting is inferior to forging in that, in many cases, it creates a piece that is homogenous and without a crystallized grain structure, therefore resulting in less uniformity and durability in the finished product. It also gives rise to issues like becoming porous during the deformation (cooling) stage.
Similar to casting, the input process for forging involves the same first step of heating the elements to a molten level. However, that’s where the similarities end, as forging metal relies not on conforming to a shape over time, but having a shape beaten out of the metal while it is still in a semi-solid state (a.k.a. billet or ingot). It must then be heat-treated to allow it to cool in a controlled environment.
[3]A forged crankshaft emerges from the press.
One advantage of forging is that it forces the grain structure of the combined metals to reform (i.e. crystallize) without losing shape, which means the finished product will be much more sturdy and reliable than a cast one. Forged pieces also respond better to heat treating, where cast pieces can give way to alloy separation if the temperature is not closely controlled.
The major downfall of forging is simply its high cost of operation, which make the process better suited to limited production runs. Tooling, machinery, personnel and frequent maintenance can quickly become a major expenditure for a business, not to mention complications from using the equipment.
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What it comes down to, as with most things in this world, is cost versus benefit. Forging can be expensive, but its durability supersedes that of casting every day of the week; casting, meanwhile, makes sense for parts that will be manufactured for a long time, like frame rails or engine blocks, but not so much for parts that need to survive shock or impact.
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