Aluminum gravity casting process

aluminum gravity casting process

Gravity casting, which is one of the common ways of metal casting, is especially suitable to aluminum casting and is now commonly used in industry. This process begins by preheating the mold to ease the flow and reduce thermal damage to the casting. The mold cavity is then coated with a refractory material or a mold wash, which prevents the casting from sticking to the mold and prolongs the mold life. Any sand or metal cores are then installed and the mold is clamped shut. After all these preparation is done, molten metal, which is at its lowest practical temperature, is then poured into the mold. Soon after solidification the mold is opened and the casting removed. In case of aluminum, the process usually takes about 2 minutes. And then the process started all over again. Preheating usually requires in the beginning of every workday and keeps adequate then after, but workers still need to pay attention to assure the mold temperature never goes to high or too low. Also the refractory coating should last several castings. Because this process is usually carried out on large production run work pieces automated equipment is used to coat the mold, pour the metal, and remove the casting.

After raw casting is finished, different kinds of machining treatment will be done according to the usage of the products or customer's requirement, such as surface treatment, ultrasonic cleaning. For example, electroplating is a plating process in which metal ions in a solution are moved by an electric field to coat an electrode. It would effectively deposit a layer of material to bestow a desired property, e.g., abrasion and wear resistance, corrosion protection, lubricity, aesthetic qualities, etc. After certain treatment, the casting products will be packaged to wooden case, separated from each other, waiting for delivery.

As we say gravity casting is suitable for aluminum casting, actually there are other casting methods, such as sand casting, die casting. Sand casting can be characterized by using sand as the mold material for casting. It is relatively cheap but with low efficiency and output. It will be chosen when the casting product is too large for the gravity casting machine. While die casting is defined as forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process. Die casting products acquire excellent dimensional accuracy, smooth cast surfaces, but the main disadvantage for its application is its high capital cost. Both the casting equipment required and the dies and related components are very costly compared to gravity casting. Therefore to make die casting a large production volume is needed. As a result, gravity casting for aluminum comes as first choice in most cases. It has reusable mold, good surface finish and also good dimensional accuracy, rapid production rates.

Nowadays, aluminum gravity casting products are widely used in many fields, such as mechanical equipment, motor parts, furniture parts, hardware products, assembly of electronic products, architecture material and so on. With the development of gravity casting technique, its products have reached more and more fields which brings the casting industry brighter prospects.