Aluminum Forging Vs. Casting
Forging is a process of shaping metal while placing materials under high pressure. This process creates very strong aluminum parts. Casting involves placing molten metal into a mold, which has a cavity that is in the shape the engineers want the cooled metal to form (See References 1, Page 1). Aluminum is one of the most easily welded metals and has the greatest variety of ways that it can be cast.
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Forging Process
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With forging, there is no melting and solidification. Forging is divided into two processes: hot working and cold working. Hot working is performed at temperatures above recrystallization and cold forming is performed at temperatures below. The metal is pressed, pounded or squeezed, often with a hammer or press. With the hammer, the aluminum receives several blows, which are not always uniform. With the press, the aluminum only receives one blow with enough force to reshape the aluminum. Aluminum alloy forgings are open-die, closed-die or rolled ring forging (See References 2). Kinetic energy is the dominant form of energy that reshapes aluminum forging
Casting Process
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With casting, the molten aluminum is forced to remain in a particular shape as it solidifies as it cools. Aluminum casting involves metal melting using the foundry. The foundry is the fire used to melt down the scrap aluminum or aluminum alloy (See References 3). Aluminum is one of a handful of metals that can be cast using all casting methods (See References 4). Heat energy is the main energy source for aluminum casting.
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Forging Pros and Cons
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Forged products do not develop cracks, shrinkage porosity and segregation, like with casting. However, the forging process places the aluminum under greater internal stress, which can make the aluminum weaker. Also, aluminum is harder to shape precisely. Using a hammer, the forger cannot predict exactly how each hammer blow will shape the metal. With the die-press, engineers have the problem of spring back, where the metal moves slightly back towards its original position. For example, if the press pushes half of the aluminum piece downward, to create a bent shape, the aluminum might spring back up slightly. Forging also requires more steps than casting overall (See References 1, Page 2).
Casting Pros and Cons
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Unfortunately, cast aluminum becomes weaker because of cracks, shrinkage porosity and segregation. Heat treatments are sometimes essential after casting to cut these stresses, leading to a stronger product (See References 1, Page 1). Casting uses a lot of energy to generate the heat needed to forge metal parts. Also, the higher temperatures of the heat make it more dangerous. However, manufacturers have an easier time producing larger quantities of parts, especially large and complex parts. Casting is also less expensive than forging overall (See References 1, Page 2).
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References
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