What is Slush Casting Process?
Slush casting process is a type of permanent mold casting process in which hollow castings are manufactured.
In slush process, the molten metal is poured in the metal mold and it is allowed to cool for a very short time such that only outer surface metal gets solidified.
The excess molten metal is then poured out of the hollow shell.
And finally, the hollow casting is obtained when the halves of mold are separated.
Don’t worry, I have explained the steps of slush casting process with diagrams (along with the example of manufacturing a dinosaur-like toy.)
Steps of Slush Casting Process
For manufacturing the component with slush casting process, the permanent mold is set up first.
This mold is clamped and it is prepared for pouring the molten metal.
The molten metal is poured into the mold cavity and its solidification begins.
Now one interesting thing to note here is that the solidification of the molten metal begins from the outer surface of the mold cavity.
In other words, the metal skin (or the outer layer) is formed first and then it proceeds towards the center.
The thickness of the skin increases as the solidification of the metal proceeds.
When the desired thickness is achieved, the mold is turned over and the extra molten metal is poured out.
By doing this, the hollow casting is formed which has only the solidified skin with exterior geometry of the cast part.
If the molten metal is allowed to solidify for a longer time before pouring out excess molten metal, then it will develop a casting which will have more wall thickness.
The casted part is removed from the mold and it is allowed to cool down.
Now let’s see the advantages and disadvantages of slush casting process.
Advantages of Slush Casting
The advantages of slush casting are mentioned below.
- Slush Casting method is cheaper as compared to other casting methods.
- The main advantage of slush casting is that it produces hollow castings which are light in weight.
- Use of molten metal is also less as the components are hollow.
- The die used in slush casting process is simple and of low cost.
- Accurate outer geometry can be obtained on the casted components by using this process.
- Good surface finish is also obtained.
Disadvantages of Slush Casting
The disadvantages of slush casting process are mentioned below.
- Slush casting process is suitable for metals which have lower melting temperatures.
- In order to pour out the molten metals, the mechanical turning mechanism is required.
- Slush casting is suitable for manufacturing the small quantity of castings.
- Strength and other mechanical properties of the casting components are difficult to control in this process.
- The internal geometry of the casting cannot be controlled by using slush casting process.
Applications of Slush Casting
The applications of slush casting are mentioned below.
- Slush casting process is used for manufacturing the components which are hollow (for example, toys, lamp bases, statues, etc)
- Slush process is also used for making some decorative coatings to improve the appearance of casted components.
Slush casting process: Image source (Sciencedirect)