How to melt Aluminium in a Ceramic furnace..??
How to melt Aluminium in a Ceramic furnace..??
(OP)
Hi everbody,
today I found this forum, and here I am with my first question...!!
In my company ( Ceramic MAterial Research ) we want to melt Aluminium ( either as powder or as piece ). I therefore have modified a 1700°C ceramic furance: Aluminium is placed in a small corundum cup, and nitrogen is blown on top of the aluminium surface at 20l/h to protect Aluminium from oxygen.
I Have tried twice: two hours at 750° and 800°C. Unfortunately, the powder did not melt.
Whats wrong?? Are two hours to short?? The same constellation worked out excellent with the melting of iron.
Thanks for a tip and regards,
Amin
today I found this forum, and here I am with my first question...!!
In my company ( Ceramic MAterial Research ) we want to melt Aluminium ( either as powder or as piece ). I therefore have modified a 1700°C ceramic furance: Aluminium is placed in a small corundum cup, and nitrogen is blown on top of the aluminium surface at 20l/h to protect Aluminium from oxygen.
I Have tried twice: two hours at 750° and 800°C. Unfortunately, the powder did not melt.
Whats wrong?? Are two hours to short?? The same constellation worked out excellent with the melting of iron.
Thanks for a tip and regards,
Amin





RE: How to melt Aluminium in a Ceramic furnace..??
RE: How to melt Aluminium in a Ceramic furnace..??
A cover on the crucible should be adequate.
RE: How to melt Aluminium in a Ceramic furnace..??
2) As hacksaw mentioned, N2 is not inert w.r.t. liquid Al.
I have grown AlN-matrix composites by by high-temperature rxn. of liquid Al alloys with N2. It was necessary to use (at least begin with) H2-N2 mixtures due to the inevitable traces of O2.
3) Use bulk Al and either an Argon atmosphere or a borax flux or both to protect from oxidation. A crucible lid as suggested above is also a very good idea.
Note: the borax is basically a barrier; it will not allow melting of Al powder, for that you would need a Cl- or F-containing flux.
4) Commercially, Al is degassed with Cl2; I doubt that you want to go this route.
RE: How to melt Aluminium in a Ceramic furnace..??
RE: How to melt Aluminium in a Ceramic furnace..??
RE: How to melt Aluminium in a Ceramic furnace..??
I also concur with everyone else's posts about using solids vs. powder as your melt stock. Aluminum oxide is a very stable refractory, so if there is any surface passivation (oxidation) on your powdered aluminum, it would definitely tend to resist melting.
As for the nitride, MatWeb lists aluminum nitride (if that's what you're forming) as having a melting point of 2227 C. So, even if you did get some of the aluminum to melt, the nitride would very readily form, and lo and behold, melting temp goes way up again. I hope this helps, and if I'm wrong, someone please correct.
RE: How to melt Aluminium in a Ceramic furnace..??
From my experience it's very difficult to melt powder, also it depends on the qualtity. I recomend you first do not use nitrogen at the melting stage, the powder must be moved every now and then. If posible use small pieces of aluminium first to get the melt pool then add the powder. When you have produced the molten aluminium then blow pure nitrogen into the bottom of the melt through a stainless steel tube. then the dross can be scimmed off the top.
I hope this helps you