What Is Casting Process?

Casting Process (or Casting) is a type of manufacturing process that is used to mold any type of part in the required shape. As a part of  Casting Process, the metal is heated up to its melting point (and even more) and poured into a mold cavity (cavity is the shape of the part) and then it is allowed to solidify (or cool) for a certain point of time.

As solidification completes, the mold cavity is removed and forward to the next process. The process of melting the metal, introducing molten metal into the mold cavity, and allowing the molten metal to solidify is called Casting and the metal that is manufactured using casting is called Casting Metal. There are different types of casting process that depends upon the shape to cast, metal, and process.

Casting Parts:

A casting process consists of several parts and designs to produce the proper casting metal. So, a typical casting consists of the following casting parts.

• Drag: The Drag is the Bottom half portion (or bottom part) of the casting that where the molding cavity is designed.
• Cope: The Cope is the Upper half portion of the casting where the gating system and risers are designed.
• Riser: The Riser is the internal part of the casting that helps to prevent the voids, and nulls while shrinkage of the molten metal.
• Gating System: The Gating System is a type of system that is used to introduce (or pour) the molten metal into the closed casting cavity.
• Pattern: The pattern is the masterpiece of the casting part. We will cast the required part with reference to the pattern shape.
• Cavity or Mould Cavity: The cavity is the hollow shape of the masterpiece that is designed in the drag (sometimes in drag and cope) to pour the molten metal.
• Runner: The Runner is the narrow and lengthy path (or way) that allows the molten metal to enter into the cavity of the mold.

How the Casting Process Takes Place?

The Casting Process is wide and involved several tasks. Good output in the metal casting can be achieved only with proper mold cavity, high liquidification of metal, good property ingredients, parts, and high concentration. The parts and ingredients will be varying according to the types of casting processes.

Generally, the casting cavity is prepared with the help of Sand and few other materials. The parts that are used to produce mold cavity is called Pattern. The general process of casting involves a great human effort.

As said, the sand plays an important role in the casting. The type of sand depends upon the type of molding and material. Few properties that every molding sand should acquire are Strength, Permeability, Thermal Stability, and Flowability. The sand is mixed up with few resins to make it strong and give a perfect texture for solidifying. The mixed sand is rammed into the drag by placing the required pattern shape that needs to be cast. Once the sand is rammed and acquired the strength, the pattern can be removed so, the hollow shape of the pattern called cavity is formed.

The cope is the upper part of the casting; it is also filled and rammed with the sand tightly. Before ramming, we should make sure that the riser portion and gatting system is well designed.

Now, the cope is inverted over the drag so that they both are leakproof. The required type of metal (whether cast iron, steel, bronze, etc) is heated up to its liquidification state. Then pour the molten metal into the cavity through the gatting system that providing on the cope.

As soon as the molten metal is poured, it will enter into the cavity through the runner (a narrow path). As the runner is narrow, the air that arrested in the molten metal will be squeezed and escapes. After introducing the molten metal into the mold cavity, the solidification due to the temperature drop will start; as the solidification starts, the shrinkage of metal will occur which results in dimension variation so, to prevent this dimension variation the Riser is used. The Riser will constantly introduce the molten metal into the cavity as soon as the shrinkage starts.

After solidification completes, the mold set will be dismantled or break to remove the solid shape. If the molding cavity is used for several castings then it is called Reusable Mould (or pattern), if the molding cavity is used only for a single casting operation then it is called Expandable Mould.

Types Of Casting Process: 

The casting is a regular and general manufacturing process, it is used to manufacture millions of materials, and the regular way of manufacturing and casting the materials will not suitable for every product so, there are different types of casting processes according to the application and different materials and products. So, the types of casting are depended upon the type of material that needs to manufacture. The important types of the casting processes are as follows.

Centrifugal Casting Process:

The centrifugal is the process of moving the molecules away from their center similarly, the centrifugal types of casting works. The centrifugal mold is cylindrical in shape and fixed inclined. As the molten metal is pouring into the mold, it will exactly fill up the whole mold without any voids.

After introducing the molten metal into the mold, the mold is rotated at a speed of 3000 RPM (Revolutions Per Minute). Due to this rotation, the fine particles will move outwards and the inner section will get solidifying with the temperature drop. The surfaces with coarser particles are called Jagged Surface.

Slush Casting Process:

Slush Casting Process is one of the simple types of the casting. The molten metal is introduced into the die or mold cavity for solidifications. The mold cavity or mold will be inverted without complete solidification. With the instant inversion, the excess molten metal will be removed.

Investment Casting Process:

Investment casting is a type of casting process that is special and helps to manufacture intricate shapes. The mold in this type of casting is prepared using wax and mercury. If the mold is wax type then it is called Lost Wax Type. 

If the mold is mercury type then it is called Mercast Process. The investment types of casting patterns will be made to dip in the slurry to prepare the mold.

The molten metal is poured into the mold and after solidification completes, the pattern is heated to get rid of the pattern.

Blow Molding Process:

Blow Molding Process is a type of air-blowing casting. The compressed air is sent into the mold so, the hallow-type parts will be produced using this blow. The plastic bottles and bulbs are manufactured using blow molding types of casting.

Apart from Centrifugal, Investment, Slush, and Blow casting process, there are a few more different types of molding processes. They are Shell Molding, Sodium Silicate Molding, Semi-Centrifuging, and Centrifuging Casting Process.

Types Of Casting Defects:

Every manufacturing and casting process does consists of defects and those are because of negligence, un-skilled labour, and atmospheric conditions. The types of casting defects are listed below.

Swell Defect:

Swelling is one of the types of casting defects that the displacement of the molten metal by sand is taken place.

Buckle Defect:

It is another type of casting defect that occur due to sand expansion. A v-shaped depression results in moldings.

Mold Shift Depression:

The Mold Shift is the type of casting defect that can be explained as the misalignment of the cope over drag which leads to the mold shift.

Scab Type Defect:

A coating over the surface of the casting is occurred while casting and this type of coating over surface is called scab type defect.

Drop Defect:

During the sand dropping, irregular shapes in the casting process over the surface are developed which is another type of defect.

Penetration Defect:

As said, the ramming should be proper and efficient. If the ramming of sand is not properly taking place then the molten metal will penetrate into the sand which is a type of defect.

Advantages of Casting:

Advantages Of Centrifugal Casting Process:

The advantages of Centrifugal Casting Process are

• The deposition of the air is absent.
• The Casting metals made by this type are strong.
• The hollow sections can be produced with the help of centrifugal casting.

Advantages Of Investment Casting:

The advantages of Investment Casting Process are

• This Process can be used to produce intricate shapes.
• The removal of patterns is easy.
• This type of casting can produce a number of products in one go.

Applications of Casting:

Applications Of Centrifugal Casting:

The applications of centrifugal casting are wide and significant. The few applications are

• This Process is used to produce composite pipes.
• It is used to manufacture ceramic and even cast-iron pipes too.

Applications Of Slush Casting Process:

The applications of Slush Casting Process are as follows:

• Slush Casting Process is used to produce Gold Jewellery.
• It is used to manufacture the lamp’s components and hallow parts.
• Slush Casting is mainly used to manufacture brass materials items.

Applications Of Investment Casting:

The applications of Investment Casting Process are as follows:

• This Process is used to manufacture intricate shapes like Pistons, Valves, etc.
• This type of casting is used to manufacture non-symmetrical shapes.
• It is used to manufacture the Jet Engine Blades and Rotors.
• It is used to manufacture the components that involve in the beverage machines.

Conclusion:

The casting is an old and regular process of manufacturing things. The products, parts, and components that available regularly in raw materials are manufactured using the casting process itself. Different types of castings are used to manufacture different types of products; even gold and jewelry are manufacture. The liquidification of the metal also depends on the type of metal, metal property, and structure.