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Sand Casting Patterns; Types And Applications

Directional Solidification With Chills In Metal Casting


Metal casting process is not an easy process. You may think that, you just pour the liquid metal inside a mold, then wait for solidification, then take the solid parts from mold. In general, yes, it is like that. But actually, there are lots of parameters to be optimized for succesful casting operation of an engineering level product. One of the most important parameter in metal casting is solidification of poured metal inside mold. This parameter also dependent upon, other parameters actually.

In here we explain the general characteristics of directional solidification in metal casting processes.

What Is ‘Directional Solidification’?

Directional solidification expression in casting.

In general metal casting processes, shrinkage is a real problem to overcome it to obtain succesful cast part. To overcome this shrinkage thing, riser systems are used to compensate shrinkage cavities. In risers, there is liquid metal to fill the shrinkage cavities occur during the solidification of cast metal.

In the solidification phase of main part inside mold, the connection between the shrinkage cavity region and the riser is very important to fill it. If the liquid connection between the riser and shrinkage cavity region is lost by solidification of this region, shrinkage cavity will not be filled with liquid metal to compensate it. This is a very big problem in terms of mechanical properties of the obtained geometry after solidification.

So, neat solidification must be established to overcome this situation. So again, you need to design the solidification direction of the liquid metal inside mold. This is done by ‘directional solidification’ methods.

How The Directional Solidification Is Done?

External chills illustration.

By the use of ‘chills’ inside the mold and liquid metal, you can start the solidification liquid metal whenever you want. These chills are small pars that made of the same metal with liquid metal, that are placed inside the possible shrinkage cavity regions and most distant places from risers in the mold.

So, the solidification will start from the most distant places and, liquid connection between possible shrikage cavity regions and risers will not be interrupted with solidification in this region.

Also, possible shrinkage cavity regions are started solidification first with the addition of chillers. This can be very helpful to compensate shrinkage cavities. These kinds of chillers are called as ‘internal chillers’.

External chillers are also used for starting the solidification from intended places of interface with mold walls. These external chillers are placed at the surface of mold walls.

So, designing the proper solidification in casting of metals with chiller applications can be summarized like this. Do not forget to leave your comments and questions about directional solidification of liquid metals in casting molds with chillers below.

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