How to cast copper tubes into 356 aluminum

[pesy]

I have heard that some foundries can cast copper tubes into alumiunm castings. I had a foundry that is doing some work for us try it, and the copper melted/absorbed into the aluminum. How can it be done?

I am using c12200 tubing, 1" dia, .049" wall
356 Aluminum
I need to maintain good thermal contact between the copper & aluminum, since the purpose of this part is a heat exchanger.
I could possibly use a slightly different copper alloy, such as a copper-silicon, or brass, if that makes a difference.

Thanks.

pesy

 

[btrueblood]

.049 wall sounds pretty thin, I'd start by trying thicker wall copper tube. Also, you may want to try packing the tube i.d. with clean sand (not foundry sand); the sand will support the tube and help keep it from collapsing at the high temperatures, and can be cleaned/flushed out after pouring. If all that still fails, then you may need to try and chill the i.d. of the tubes, something along the lines of filling them with water? (but watch out for the steam flashing off when pouring!) (the idea is to try to rapidly solidify the Al in contact with tube o.d., to prevent the Al from alloying with copper and "slowly" eroding it away).