Material for holding aluminum melt

[cercle]

What would be the best material for holding a small amount (one cu. ft) of liquid aluminum at its melting point (1220 F or 660 C) at atm. pressure?
Do I need to use costly ceramics (Silicon carbide, graphite) or does Stainless Steel (304?) can do the job?

 

[unclesyd]

We used cast iron crucibles for handling small quantities of Aluminum. You can use C/S, Graphite, or Refractory. I would stay away from S/S even though it will work for a time I read of some problems posted on other forums.
The C/S crucibles are relatively cheap. It all depends on the how much you are going to use it.

 

[kenvlach]

As unclesyd said, “It all depends on the how much you are going to use it.”
And, is this high purity aluminum that you need to avoid contaminating?
I suggest using a ceramic coating more thermodynamically stable than Al₂O₃ or else Al₂O₃ itself.

For short-term use preparing experimental alloys, I have used spray + bake coatings of stabilized-zirconia, yttria and BN from Zyp on crucibles, and paint-on graphite coating on cast iron chill molds.

http://www.zypcoatings.com/

(BN is also available through

http://www.mcmaster-carr.com

p/n 10515K35 )

For long term use, suggest Al₂O₃ crucible inside ceramic-lined carbon steel (always a chance of crucible breaking!). Zirconia-based refractory inside a steel shell also works. If you are pouring in liquid Al from a furnace, pre-heat the crucible with a natural gas flame.

Also, if there is an aluminum foundry nearby, pay them a visit.

 

[unclesyd]

kenvlach gave some sage advice when he mentioned visiting an Aluminum Foundry.
There are quite a few caveats in dealing aluminum casting.

Molten Aluminum doesn’t like moisture in any shape or form. The moisture can come from any things like the sugar in Aluminum cans that had been baked to dry out. The temperature wasn’t high enough and the person lost the aluminum he was melting. Molds can be big problem usless done right. Preheat every thing that goes into the pot.

If you are going into an industrial area I would suggest a very formal process audit and the purchase of some reference books prior to commencing any casting.

If it is one-up type work try the following website.

http://www.lindsaybks.com/

 

[cercle]

Thank you for your good advices.
The idea is not to cast parts or recycle scrap alum. but to use the phase change of a given amount of clean (and chemically "flat&quot alum. in a "thermal battery". So the same alum. is to be remelted over and over. Nasa used graphite crucible for the same purpose but without any mention of coating to stop graphite burning. Ref: S.M. Raqué et al. AIAA doc A97-31343 page 5.
In my case, alum would also be confined in a close vessel (crucible). No contact with O2, N2 or H2O. Do you think that a good coating (ex. Ceramic Oxyde, trade name Sealmet or Silicone Carbine, trade name Covergard both from Zyp) over graphite will last?
Your answers are always appreciated.
Best regards
Denis

 

[unclesyd]

Like I've mentioned before when you made a statement in a meeting and the slide rules came out you knew you were in trouble where as now you don't know what they are doing on the laptops or PDAs'.
I would contact ZYP coatings with your specific problems. The people there are very knowledgeable and quite helpful. I been looking for some names, but can't lay my hands on any.
If not mistaken their original coatings were for Graphite.

 

[arunmrao]

Graphite crucible without coating should be good enough for holding molten aluminium. If cast iron crucible is used you need to provide a ceramic coating. This is supplied by Foseco,locally called as dycote. Foseco has a range of products and a call to their representative should be helpful.

 

[drfusion]

For a few quantities (trials), we use refractories (base Al203 at least 60%) bricks or castables, we are handling and transporting the aluminum in small ladles (450 kgs); only to do trials we use a small crucible furnace (silicon carbide).

Eulogio Velasco
Melting Process Eng
Nemak