Metal Casting Zone

Hi there.

I'm not very sure where to post this question, since I'm a newbie, I'll just post the question here.

Basically, I melt some Aluminum sheets at a temperature of 830 DEG C. I'm not sure why I have to go that high but the lower temperatures don't seem to melt it.

However, even at that temperature, the Aluminum sheet has not fully melt. Was wondering if anyone would have a clue to that?

Sadly, I've no idea on the specifications of the sheet as its bought from some hardware shop.

Also, how to not get the Aluminum sticked to the sides of the crucibles once it has melt?

Would be great if I can get some feedback soon.

Thanks in advance!

J3rmz

830 C should melt it. Are you getting a small pool of Aluminum in the bottom? What you are seeing may be Aluminum oxide. It sticks to the sides and won't melt. You could try to add more Aluminum, but sheet Al usually has a lot of oxidation on it. Try to find some cast Aluminum or at least some thicker bar stock.

Welcome to the forum!

Tell us about your furnace and what you are using for a crucible and fuel.

Hey Jammer.

Thks for the reply.

I'm using the carbolite CWF 13L.

As for the crucible, it's like a mini bowl that can hold up tow 125mL.

I don't see any pool of Al. Perhaps it's too little. However, when I touch it it's soft, tho I can see solid form.

Hrm, what about using powder Aluminum? Do you think it's a good idea?

J3rmz

Those are an electric lab furnace. They should work very well. I don't think powdered Al would be very good, the idea is less surface area so there is less oxidation. As soon as Aluminum oxidizes it's pretty much done and the oxide comes off as dross. That's one reason Aluminum cans are so hard to melt, you end up loosing a lot of metal to the rapid oxidation of the can. In a gas furnace, you can somewhat control the oxygen by making a rich flame.

Hrm, will increasing the temperature cause the Al to oxide any faster?

That's a good question, I don't know. I know with thin stuff, that if you can get a small pool of Aluminum in the bottom of the crucible, then you can push the new stuff into that and it helps melt it faster.
I have put charcoal on top of Brass to keep the O2 off the molten metal. That's mainly to keep the zinc from burning off.

Oh thanks for the advice.

I'll try putting some charcoal and see if it works. =)

What do you mean by "the new stuff"?

New stuff as in unmelted metal. If you can get a pool of melted metal then it's helps to melt the new metal as you push it in. This depends on your furnace if your able to feed metal into your crucible. From the pictures on the website, it doesn't look like you have access to the crucible unless you open the door. Then you lose a lot of heat.

Yeah. That's another problem too. Everytime I open the door, the temperature drops at quite a high rate.

In any case, I'll try first. Thanks so much for you advice thus far. =)

hi and welcome to the forum. you have had some sound advice from jammer. i dont think you are melting enough aluminium.????? 250 grams is about the smallest amount to melt and pour. if you are recycling you will be amazed at how much "muck" you will skim from the top of the pot/crucible. plate aluminium is a bad source for metal. its not pure and will require almost brass temp to melt!!1200 deg c. some pics would help with further advise.