Metal casting separates into two categories: reusable and expandable.
Today, we will focus on reusable methods as we discuss the different types of metal casting methods.
Permanent molds are typically made with metals with a higher melting point than the metal they’re packed with. The permanent molds are also used for iron casting along with lower-temperature alloys. To avoid cracking from the temperature difference, the molds are first preheated before pouring the first casting. It’s excellent for iron because it’s durable, but avoid using it for yellow brasses. Also, the permanent core inside of the mold must be kept simple for easy withdrawal for reuse.
The only difference between permanent and semi-permanent molds is their cores. Semi-permanent molds may use expandable sand cores to achieve more complex core shapes. If there is an opening left in the casting to remove the center, a vibrating table will shake the excess sand through an hourglass.
Centrifugal casting uses centrifugal force to cast the metal, hence its name. While hot molten liquid metal is being fed into the opening, the mold rotates at high speed around the central axis. This method is best for circular or cylindrical shapes, like rings or tubes. Since impurities end close to the inner surface, they can get machined away, and this casting method has a low defect rate.
Centrifugal and investment casting are two of the more popular forms of metal casting. They are similar but also different methods of casting.
Using forces besides gravity, pressure casting allows foundries to control the rate the mold fills because these artificial forces can be varied. Gravity only works with the same power. You’ll find gas or air, centrifugal forces, mechanical, and vacuums used in pressure casting.
Another type of metal casting method is continuous casting. This method begins high above the factory floor. Liquid metal is poured into a funnel that controls the casting rate. The mold walls become cooled down, so the exterior will freeze as it passes through, and the metal begins to solidify but is still malleable.