Serrations in chills

[Nadimuthu]

WE have received some sample castings from our overseas customers and found that the areas where the chills have been placed have criss-cross markings indicating the serrations in chills.In India ,we have not come across any foundry with this practice.This has been observed in the Aluminium sand castings.Could any of you give us a reason why such serrations are there and will it be helpful if we adopt the same method.

 

[mcguire]

Does it look like the serrations have been put there to increase the surface area and aid in heat transfer? That would be one potential reason.

 

[etch]

We as an Aluminium foundry, have found that using serated chills have greatly improved the quality of the castings. The reason for its can be put into two categories.

1. Increased surface area for chilling.

2. it helps reduce blow off (where the chill blows part of the casting away from the face of the chill) the typical defect looks like a large depression in the metal at the metal chill interface. I think that having a flat surface sitting tight againnst the metal means no venting is possible. We have found that the serrations eliminate the chills being blown off, and help reduce shrinkage.

To add to this the latest thinking is that fins should be used attached to the casting, this eliminates the need for chills. Though im still doubtful as the ability to control directional solidification.

i would say take a chill, take an grinder and take make a lattice network across the chill and try it.