18 replies to this topic

[sasman]

I will post a video of my Magnesium fire!! later when i get home..I used an electric furnace to melt 2 kg of Magnalium...in a salamander crucible...The first time i made magnalium every thing went Ok.. So my 2nd batch i made a bit more..The only thing was it caught fire and i could not put it out ..

When i removed it from the furnace it burnt with a brilliant white light i left it for a moment hoping it would go out .. but nope just sat there Glowing!!white .. so i put it back in the furnace..which when i closed the door seemed to put out the fire.. but very time i opend the door it reignited...

I turned off the furnace Hoping that it would cool down a bit ..But the furnace is very well insulated so takes a very long time to cool...Al and Mg melts about 650 centigrade yet Magnalium melts at a much lower temp i think about 450?.. this is well below the ignition temp so i was hoping to get it low enough so that it would not reignite..I left it in the furnace and it just smoulderd and the crucible started filling up with some Black powdery Broccli like substance...Big thick crust which totaly covered the crucible .. even then when i removed it from the furnace and tried to remove this thick crust it reignited....

It Totaly destroyed my Crucible..and i retrived no Magnalium..all what left was this big thick black crust..I filmed it on my camcorder.. i will see if i can find the clips..and post it. later..

[alany]

Sulfur Hexafluoride is the shielding gas of choice commercially. Its density, inertness and non-toxicity make it ideal. Nitrogen is too reactive to use as a shielding gas. A shielding gas, or even a flux is by no means required, I just do it open crucible, it works fine with some care.

Sprinkling Sulfur on burning MgAl or Mg will put it out. Try it, it works every time.

[rooster]

Magnalium can also be made with a protective salt flux on top. Crazy_Swede from the APC forum knows a lot about it. I am going to try using some LiCl(about the right MP) for my first try at MgAl. Don't want it to catch fire. Also, this keeps the air away, as the molten salt layer floats on top. The only problem I can see is that it might be somewhat contaminated by LiCl. Should not be a problem if you pour the liquid MgAl out in water though...

[alany]

If you are going to pour it into water just make sure it is deep and large compared to the volume of the Magnalium. That will minimise splatter of the moltern metal and quench it fairly fast without too much boiling. A shallow tray of water just increases the chances of a steam explosion and scattering of burning moltern metal everywhere.

Using a flux is definately a good idea. Ones based on MgCl are ideal, but even your basic KCl/NaCl eutectic works. I don't like using NaCl though. The Sodium contamination which may spoil colour purity if the metal is used for colour compositions. I've used pure CaCl2 and KCl with no major dramas, except for their high melting points (in excess of 770 C more than 100 C over the melting point of Al). I always melt the Al first then add Mg ingots anyway, so it isn't a major problem, but it means the final melt is very hot and will ignite if poured or otherwise uncovered.