Casting: Definition, Types, and Applications

What is Casting?

Casting is a manufacturing process in which a liquid material is usually poured into a mold containing a cavity of the desired shape and then allowed to solidify. After solidification, the workpiece is removed from the mold for various finishing treatments or to be used as an end product that also defined as casting.

As casting materials usually use metals or various types of hardening materials that harden after mixing two or more components. Examples are epoxy, concrete, plaster of Paris, and clay.

This is most commonly used to make complex shapes that would otherwise be difficult or uneconomical to make using other methods.

And cast products are found in a variety of applications including automotive components, aerospace parts, Heavy equipment such as machine tool beds, ship propellers, etc. can be easily cast to the required size instead of being made by joining several small pieces together.

What is casting process?

It is a manufacturing process in which liquefied material, such as molten metal, is poured into the cavity of a specially designed mold and allowed to harden. This part is also known as casting, which is ejected or broken out of the mold to complete the process.

It is a 7,000-year-old process. The oldest surviving casting is a copper frog from 3200 BC. Modern advances in casting technology have led to a broad array of specialized casting methods.

Casting

What are the Different Types of casting?

Types of Casting Prossess:

  • Sand casting.
  • Investment casting.
  • Die casting.
  • Low pressure casting.
  • Centrifugal casting.
  • Gravity die casting.
  • Vacuum die casting.
  • Squeezing die casting.
  • Lost Foam Casting
  • Continual Casting

1. Sand Casting

Sand casting is one of the most popular and easiest types of casting and has been used for centuries. Sand casting enables smaller batches than permanent mold casting and at a very reasonable cost. Not only can manufacturers use this method to produce products at low cost, but sand casting also offers other advantages, such as very small operations.

The process allows castings that are small enough to fit in the palm of the hand to castings or large enough like train beds. Sand casting can also cast most metals, depending on the type of sand used to make the molds.

Sand casting is typically based on silica-based materials, such as synthetic or naturally bound sand. Cast sand generally consists of finely ground, spherical grains that can be tightly packed together to form a smooth mold surface.

The casting is designed to reduce the risk of cracks, tears or other defects by allowing a moderate amount of flexibility and shrinkage during the cool down phase of the process. The sand can also be strengthened by adding clay, which will make the particles more closely bond. Automotive products such as engine blocks are made by sand casting.

2. Investment casting

Investment casting is also known as lost wax casting, it uses a disposable wax pattern for each cast part. In this method wax is directly injected into a mold, removed, and then coated with refractory material and binding agent, usually in several stages, to build a thick shell.

Several samples are put together to form common sprues. Once the shells have hardened, the patterns are inverted and heated in ovens to remove the wax. These patterns require extreme care as they are not strong enough to withstand the forces involved in making molds. One advantage of investment casting is that the wax can be reused.

Investment casting is widely used to make parts for the automotive, power generation, and aerospace industries, such as turbine blades. These castings ensure that high quality components are made with key benefits of accuracy, repeatability, versatility, and integrity.

3. Die Casting

Die casting is a method of molding materials by forcing molten metal under high pressure into a mould cavity. Most die castings are made from non-ferrous metals especially zinc, copper, and aluminum based alloys. However, iron metal die-cast parts are possible.

The die casting process is particularly suitable for applications in which many small to medium-sized parts with good details, fine surface quality and dimensional accuracy are required.

4. Low pressure casting      

In low-pressure casting, the die is filled with metal from a pressurised furnace, the pressures typically being around 0.7 bar. The holding furnace is located in the lower part of the vertical die casting machine, with the molten metal being injected straight up into the bottom of the mold. The pressure holds the metal in the die until it solidifies.

One of the main advantages of this process is precise control of the die cavity filling. Molten metal flows quickly and smoothly through the feed lines, reducing oxide formation and preventing porosity.

This process was developed for the production of axially symmetrical parts such as car wheels. By using sand cores in the die, however, it is also well suited for the production of parts with hollow profiles and complex geometries.

5. Centrifugal Casting

Centrifugal casting is used to make long, cylindrical parts like cast iron pipes by relying on the G-forces developed in a spinning mold. Molten metal introduced into the mold is flung against the inside surface of the mold, creating a cast that can be void-free.

Originally invented as the de Lavaud process using water-cooled molds, the process is applied to symmetrical parts such as soil pipe and large cannon barrels and has the advantage of making parts with a minimal number of risers.

In the case of asymmetrical parts that cannot be rotated around their own axes, a variant of centrifugal casting called pressure casting, arranges several parts around a common sprue and rotates the molds around this axis.

A similar idea is used in casting very large gear ring, etc. Depending on the material being cast, metal or sand molds can be used.

6. Gravity Die casting

Gravity Die Casting is a permanent mould casting process, where the molten metal is poured from a vessel or ladle into the mould. The mould cavity fills with no force other than gravity, filling can be controlled by tilting the die.

Undercuts and cavities can be machined into the component shape using sand cores. This process offers a better surface quality than sand casting as well as better mechanical properties, both due to the rapid solidification.

In addition, this process has a higher casting rate than aluminum sand casting, but the metal molds are more expensive than sand. The advantages of this process include the possibility of low gas porosity and fine grain sizes can be achieved.

Compared to sand casting, this process requires less post-processing and cleaning, and gravity die casting tends to result in a higher quality product. The gravity die casting manufacturing process is generally less cost effective in making of tooling compared to sand casting.

7. Vacuum Die Casting

Vacuum-assisted die casting is an important process capability at Kennedy Die Casting. The vacuum evacuation of the die cavity reduces gas entrapment during metal injection and decreases porosity in the casting. The result is a die casting with a higher level of quality.

Vacuum systems are only a supplement. They do not substitute for good die casting design practice in the engineering of the die cavity, runners, gates and overflows.

8. Squeezing die casting

Squeeze casting, also called liquid forging, is a hybrid metal forming process that combines permanent mold casting with die forging in a single step where a specific amount of molten metal alloy is poured into a preheated and lubricated die and subsequently forged and solidified under pressure.

9. Lost Foam Casting

Lost-foam casting (LFC) is a type of evaporative-pattern casting process that is similar to investment casting except foam is used for the pattern instead of wax. This process takes advantage of the low boiling point of polymer foams to simplify the investment casting process by removing the need to melt the wax out of the mold.

10. Continual Casting

Continuous casting is a refinement of the casting process for the continuous mass production of metal profiles with a constant cross section. Molten metal is poured into a water-cooled, open-ended mold that allows a “skin” of solid metal to form over the still-liquid center, gradually solidifying the metal from the outside in.

After solidification, the strand, as it is sometimes called, is continuously withdrawn from the mold. Predetermined lengths of the strand can be cut off by either mechanical shears or traveling oxyacetylene torches and transferred to further forming processes, or to a stockpile.

Cast sizes can range from strip (a few millimeters thick by about five meters wide) to billets (90 to 160 mm square) to slabs (1.25 m wide by 230 mm thick). Sometimes, the strand may undergo an initial hot rolling process before being cut.

Continuous casting is used due to the lower costs associated with continuous production of a standard product, and also increased quality of the final product. Metals such as steel, copper, aluminum and lead are continuously cast, with steel being the metal with the greatest tonnages cast using this method.

Advantages of casting process

  • Any intricate shape may be internal or external can be made
  • It is practically possible to cast any material
  • Tools required for casting processes are generally inexpensive
  • Cooling of casting is generally uniform from all directions hence it is generally does not have directional properties
  • Many materials can only be processed by casting processes because of their metallurgical considerations
  • It is practically possible to make casting of any size, even up to 200 tons

Disadvantages of casting process

  • It gives poor surface finish and mostly requires surface finish operation.
  • Casting defects involves in this process.
  • It gives low fatigue strength compare to forging.
  • It is not economical for mass production.

Applications of Casting process

  • Transport: automobile, aerospace, railways and shipping
  • Heavy equipment: construction, farming and mining
  • Machine tools: machining, casting, plastics moulding, forging, extrusion and forming
  • Plant machinery: chemical, petroleum, paper, sugar, textile, steel and thermal plants
  • Defense: vehicles, artillery, munitions, storage and supporting equipment
  • Electrical machines: motors, generators, pumps and compressors
  • Municipal castings: pipes, joints, valves and fittings
  • Household: appliances, kitchen and gardening equipment, furniture and fittings
  • Art objects: sculptures, idols, furniture, lamp stands and decorative items.

FAQs.

What is Casting?

Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process.

What is Casting meaning?

Casting is a manufacturing process in which a liquid material is usually poured into a mold containing a cavity of the desired shape and then allowed to solidify. After solidification, the workpiece is removed from the mold for various finishing treatments or to be used as an end product that also defined as casting.

What are the types of casting?

Types of Casting Process:
1. Sand casting.
2. Investment casting.
3. Die casting.
4. Low-pressure casting.
5. Centrifugal casting.
6. Gravity dies casting.
7. Vacuum die casting.
8. Squeezing die casting.
9. Lost Foam Casting
10. Continual Casting