Aluminum Foundry

Yes you need to get the crucible temperature well above the melting point of the cans to keep the aluminum from solidifying when you remove the heat....You must maintain the aluminum in a liquid state long enough to remove the impurities and to pour the aluminum from the crucible into the forms....the crucible heats slowly but the aluminum melts quickly, you need to heat the crucible first, that then melts the aluminum....

So.....There will not be a problem because the combustion gases in contact with the cans melting ?

What is your fuel type and delivery method? The temperature required is 660°C+...What is the feedstock and final composition desired?

https://www.materialgrades.com/al-6061-material-processes-in-beverages-cans-manufacturing-1207.html

https://unitedaluminum.com/aluminum-technical-data-alloy-chmeistry-and-mechanical/?gclid=CjwKCAjwpqCZBhAbEiwAa7pXedYi-H31wI-SRvc9SkOqu7brUrYR96KWQPJrTJQjgMbJmSD5YHRqShoCh0sQAvD_BwE

I have never done this but I do know that the liquid aluminum will be more reactive than solid cold aluminum. Blowing combustion gases onto the hot aluminum for an extended period of time might be an issue.

You tell us “...within a crucible inside an isolated container.”

What is this isolated container? Is this container driving the need to heat the crucible from above?

Offhand this sounds like a lot of wasted heat/fuel compared to bottom or edge heating.

Fuel type and delivery may be another concern... you don’t want to have molten aluminum forced out of your melt vessel by the pressure of the flame.

I would think heating from above would be inefficient. You would be fighting convection.

You might find some good information here...

https://www.wikihow.com/Melt-Aluminum

What is your batch amount?

https://www.youtube.com/results?search_query=melting+aluminum+cans+into+bars

One issue might be the aluminium oxidising instead of melting. Applying flame from above exposes the aluminium directly to the flame which will likely be higher than ~660C needed to melt it. Heating the crucible might not just be more efficient; it might be a lot safer.

Also. I seem to remember from my, admittedly brief, exposure to foundry practice that aluminium has the unusual property that one can add cold aluminium to molten aluminium and it will simply melt. We were discouraged from doing this with other metals because of the violent reaction of cold metal being added to molten. An open crucible allows additional material to be added; the method you describe might deny you this convenience.

Good day.

Beside the way to open it to re-load, remove gross, remove the crucible, etc.... this follow is the schematic to better explain my concern

Finaly is convection... the heat (flame) coud be adjust upward.

Putting the exhaust above the heat input will make controlling the process heat difficult and more heat means more oxidation.

All the contributors have explained why heating should be done from beneath. What is your rationale for heating from above?

The reason to apply the heat from above is because our liquid fuel in negative pressure burn all the fuel.

My concern WAS the gases from combution could ENTER the aluminum melting and provoke more slag/dross.

I've found this machine.. similar the procedure I was looking for.

https://www.youtube.com/watch?v=pEzZ2Bp-qHo

Now I am trying to find the better additive to remove the slag/dross.

Back in the day steel ladles used in aluminium die casting work were dipped on-site in what seemed to be (and maybe was) a clay slurry. When dry it formed a stick-free surface on the inside and outside of the ladle. I would think that for a small pour such a coated ladle could be heated by torch from the outside and serve as a crucible. There would be good heat transfer and the aluminium would pour well without sticking. (a cursory search found several suppliers of refractory coating for ladles)

It’s electric now.

Try it and you will see why it is now done from the bottom,instead of from the top,and most modern metal foundries are carbon-arc powered.