About casting process
Casting is a process by which hot liquid material or molten metal is poured into a mold having a hollow cavity and then the material is allowed to cool so that it takes the desired shape. Intense heat is used during the process to melt the metals. The cooled or solid part is known as casting. This solid part is either ejected or broken out of the mold to complete the process.
Casting process is used to make complex shapes that are otherwise difficult to make using other methods. It is an age old process (6000 year old) and the oldest surviving casting known is of a copper frog art dating to approximately 3200 BC from Mesopotamia.
Advantages of casting
- Can be used to make Complicate designs of products, in a variety of strength
- Exclusion of various steps like machining, forging, and welding.
- Some metals can only be cast because they cannot be hot worked into bars, rod, plates and other shapes from ingots.
- Construction may be simplified.
- Enables to mold the products into one single unit than manufacturing different parts and assembling them.
- Favorable engineering properties obtained like machinability and vibration damping capacity.
- Exhibit the same properties regardless of which direction is selected.
- Wide range of alloy compositions and properties are produced in cast form.
Major casting processes
Sand casting - is a casting process where the molten metal is poured into a mold made of sand. There are various types of sand castings like Green-sand molding, air set sand casting, dry sand molding and the lost form method. Sand casting is the most commonly used Casting Process because of the cost effectiveness of the process and the east availability of raw materials.
Resin casting - is a form of plastic casting process in which the molding materials used are liquid resin like acrylics, polyesters , urethanes, epoxies, etc. This process is primarily used for casting industrial prototypes and dentistry. Resin casting is an uncomplicated casting procedure that is preferred by hobbyist and artists.
Investment casting - A pattern is made of wax and a wax gating system is separately arranged for investment casting. The pattern and gating system are assembled and dipped in a slurry of refractory coating material like tetra ethyl silicate, ethyl alcohol, hydrochloric acid, silica, magnesia, etc. The pattern is placed upside down and supported by flask. Now the molding mixture is poured around the pattern. The mold mixture is a combination of sand and and materials like alumina cement, ethyl silicate, etc.
The mold is placed in a inverted position and heated, which helps the wax that flow down to be collected for reuse. A specific temperature is maintained in the mold for pouring of the alloy and for helping preserve the intricate casting designs. When the wax completely melts out, the void space is filled with molten metal. Burnout process helps in removing the wax and gas-forming material formed in the mold.
Permanent mold casting - molds are made of metals but the patterns can be made either of sand or metals. The molds are made using metals like cast iron or steel. These metal molds expand on heating or when hot metal is poured into it. Therefore, while making the mold, it is not expanded as is done with sand and plaster molds.
In die casting process - molten metal or other materials are forced, under high pressure into the cavities of the steel mold. Dies are two part molds that are made of alloy tool steel - the fixer die half and the ejector die half. The die or mold is fabricated with the impression of the component that is to cast.
Types of dies
- Single cavity to produce one component
- Multiple cavity to produce a number of identical parts
- Unit die to produce different parts at one time
- Combinations die to produce several different parts for an assembly
The molten metal is injected into the die under high pressure and high speed, which helps in producing a casting that is smooth and precise as the original mold. The pressure is maintained on the mold until the hot metal solidifies. When the metal is hardened, the die is opened to remove the casting.
Ceramic mold casting - a casting process in which materials are combined to make a mold which has rubber like consistency. It can be used for simple home foundry casting and also complicated, intricately designed industrial castings. This casting provides attractive looks for kitchenwares and decorative items.
For more information on different casting processes including lost wax casting, pearlitic casting, metal casting and about casting industry in India, visit: industrialmetalcastings.com
About Author / Additional Info:
Mark Nel has lot of experience and great knowledge about metal casting industries. He just want to share his exrperience and knowledge through article. Now he is associated with industrialmetalcastings.com