What is Centrifugal Casting? Part 1

Many finished metal products go through different forming processes but, nearly all of them begin as an ingot that is formed by a casting process. Casting in its most basic form is a widely known metal manufacturing method. However, Centrifugal casting has great importance to the metal production industry because of the high-quality products the process creates. Understanding centrifugal casting and if it is right for your application is an important step when selecting metal products for purchase.

What is Centrifugal Casting?

Centrifugal casting involves the use of a mold in which molten metal is poured and allowed to solidify. What makes the centrifugal casting process unique from standard casting processes is that the mold is rotated rapidly rather than held statically. The rotation creates centrifugal force during solidification and gives the process additional benefits over a standard casting process.

Benefits include:

• Greater strength
• Increased purity
• Cost-efficiency

As a result of the rotation, it is also worth noting that metal components manufactured using the centrifugal casting process are virtually always cylindrical in some way.

How is Centrifugal Casting Performed?

The exact way to carry out the process of centrifugal casting depends on the type of centrifugal casting being used (the different types will be covered in part 2), but in general, the following steps occur:

First, a mold is created which is shaped to the desired final product. While the part being made does not have to be perfectly round, the mold must generally be round so that it is in balance as it begins to rotate later in the process. The mold is then typically preheated to aid in the quality of the casting as solidification occurs. The mold is also spun rapidly so that centrifugal force will be applied to the molten metal as it is poured in. Meanwhile, a volume of metal that has already been refined is heated and melted down to a liquid in a crucible. The crucible is then tilted, and the contents poured into the mold.

As the molten metal pours into the mold, rapid rotation forces the metal to the extremities of the mold (centrifugal force). The more metal added, the greater the thickness of the resulting round or cylindrical part. While spinning continues and more molten metal is added, the metal already poured into the mold begins to solidify. As solidification occurs, the centrifugal force also causes the denser parts of the metal to move to the outer diameter of the unfinished metal component while the less dense impurities move towards the inner diameter. Once the desired thickness is achieved, the crucible is tilted back to an angle where no more molten metal enters the mold, and it is allowed to cool.

Once cooled, the metal component can be removed from the mold. Since the centrifugal force moved most of the impurities to the inner diameter of the metal, machining operations can be used to easily remove these impurities from the component. Depending on the application, the outer diameter may have to be machined slightly as well. Once machining is completed, other post-processing operations such as heat treatment can be performed.

While this article provides a general overview, there are different types of centrifugal casting that are important to understand, as well as their respective advantages and disadvantages. This, and common applications of centrifugal casting, will be covered in part 2.

References:
http://what-when-how.com/
https://www.metaltek.com/blog/
https://www.youtube.com/watch?v=o4vkUHb91H0