18 replies to this topic

[RegimentalPyro]

Well the God of Pyro's smiled on me this week. I took delivery of 1Kg of Magnalium (50/50). Unfortunately it was in the form of large [1inch average!] nuggets, so I thought I'd share my experiences in getting this down to a usable powder. (in quantity)

Magnalium is very brittle, and a sharp whack will fracture it quite nicely. However it shatters all over the place and you tend to lose a lot of the "fines" when you use this method. I discovered fairly quickly that this is not the way to proceed.

"No worries" I thought. "Into the ball mill you go". Whilst this worked, it was very slow. The media I was using [brass bar] would only yield about a tablespoon of powder every hour. Because of this I can't really recommend this method either.

Upon a recommendation from the supplier, I tried using an electric coffee grinder. Now this works! Lots of powder produced quickly. However there is a snag - you can only put small [2-3mm] fragments into your grinder otherwise it will knacker the grinder fairly quickly. The final method I devised was as follows.

Take a large saucepan with large nuggets in it and put it inside a bin bag, and place on a firm [concrete?] surface

Using a lump hammer [also inside the bin bag] whack the nuggets until they are of a usable size. The bin bag does a good job of keeping everything inside the saucepan. I would whack a few times, then sieve out the fines, then return the larger chunks for more "beatings"

Finally put the fines into the coffee grinder and pulse it until no more "rattles" are heard.

The resultant powder should yield a variety of sizes, from 40 mesh all the way to airfloat. Using this method I produced 300g of MgAl in well under an hour - Result!

Refinements to this method are welcomed

[karlfoxman]

Well me and waz just come across the same idea, we started by filing the stuff....it took 30 mins to get 25g of 60 mesh!! We then decided to use the coffee grinder, it turned the lot into dust in 1 min!!! 100g was 60mesh in 10mins. We did try a chunk and we were lucky to still have the grinder work, it jammed the blades so take it from us use pieces no more than 5mm square or you will be buying a new magnallium duster!! Happy wizzing.

Glad you bought this up Regimental

Karl

[sasman]

Vodka... Hmmmm.. makes my memory a bit blurred but i remember posting about powdering some of My home made Magnalium...its on the Forum somewhere...

But i can clearly remember my very very fine powdered Magnalium...it was close to Dark Al...It was ground to a very fine powder very fast..Using a ball mill..+ 19mm Steel balls...Magnalium is very brittle.. this property makes it very good to powder...

[minalth]

Milling and coffee grinding seem to make different results, the milled magnalanium comes out looking darker, the ground brighter (like glitter is bright).

Planning on doing some tests sometime, and seeing what the difference is.

[RegimentalPyro]

I'd be very interested in seeing the results of those tests.

sasman: When you ball milled did you put large chunks in, or did you already have it down to splinters first? I suspect my mill cannot cope with large chunks, but I'd be interested in seeing how it deals with MgAl that has already been powdered to a large extent. I believe it could increase my yield of smaller-than-200mesh powder

[Richard H]

Put it this way. I recently milled 1kg of Stibnite (Antimony Trisulphide). It was supplied in fist sized chunks which I placed in thick plastic sheeting and then gave them a good wack with the sledgehammer. After I got it all passing 40 mesh I put it in the mill, about 6 hours later a fine, jet black, and very sparkly powder passing 200 mesh was produced.

I expect doing the same with MgAl will yield same results given its brittle nature.

[chemicalwazi]

A LARGE bench vice, makes a great crusher, if you bag your material well or indeed a hand press (when i get hold of a bottle jack). Then as you say ball mill or stick in a evil grinder.

[Creepin_pyro]

Remember when you're powdering your Mg/Al to save some coarser grades... Larger particles work very well in fountains, the finer particles being perfect for colour stars.

[Draco_Americanus]

one needs to be carefull with realy fine Mg/Al if it's used in flash, I have some thats about 400 mesh and my expermentaion yielded a critical mass of about 3-4g.

[sasman]

er

Edited by sasman, 25 October 2010 - 09:48 PM.

[tdpyro]

I found that sieving fine powder magnalium is a lot easier with the coffee ground type. The coffee grinder makes a more granular particle, as opposed to ballmilled powder , which seems to be more like flake, causing it to jam in fine mesh sieves.
This probably also has implications when being burnt , different effects may be achieved with the different particle grades, although I have not tested this yet.

[minalth]

did you smell whiff of ammonia when you were grinding it up?...

Yes, I did. Don't know why, but I think it forms when the metal is cooling... my MgAl was porous, and I think it must have been ammonia in the bubbles...

[alany]

In my experence the porosity is normally hydrogen dissolved in the metal from reduction of the propane and its combustion products (e.g water). It is likely that the high temperatures and metal itself catalyse ammonia production from atmospheric nitrogen and the dissolved hydrogen.

I've also noted that if you are silly enough to get water anywhere near hot magnalium the ammonia just pours out. It is scary how fast it can generate a cloud of ammonia/ammonium hydroxide spray that will incapacitate you outdoors if you get a lung full, let alone in a confined space. I'd recommend never attempting to quench your magnalium, especially if you use a propane furnace to alloy it.

In cases where my magnalium has caught and burnt for a while I find large amounts of carbide in the dross too, producing ethyne when I wash it off. I guess that is one very inefficient way to make carbides without an arc furnace.

[Draco_Americanus]

has anyone been able to make this stuff with an inert/protective gas? Maby fill the furnace with nitrogen or argon? As I understand the indrustral way to make Mg/Al is to do it in a vacuume but that set up may not be feasable in a home work shop.
I also would be very concerned about that ammonia smell

[gilbert pinkston]

in my case i got by without the inert gas yesterday i made about a pound and a half of magnalium out side over a charcoal fire in a coffee can with some forced air using a deep iron skellett with a lid i think we call them a dutch oven about one quart capacity
i melted the Al and Mg together no problems the stuff did catch fire when i poured it out it may have been too hot or some thing but i lost very little material i did pour it in water (maybe a bad idea according to recent posts) so i may have to work on my cooling and recovery method.....smelled kinda like carbide and faintly of ammonia but not bad
it could be crumbled in my hands amazingly brittle don't know if the water had something to do with that but a good property i dried it quickly with a hair drier
i wonder if it would be so brittle (and easy to remove) if i just kept the lid on and let it cool in the pot and chipped it out later that would shure make things easier
one thing is for sure and preparation is important here ..... when magnalium burns in any significant amount you are going to have a hard time getting it out just be ready and be somewhere that an uncontrolable fire will not cause damage this cannot be over stated be prepaired for anything
so far like most things ( i manage to make or get Cheap about 90% of my pyro supplies)i have managed to get what i wanted without overcomplicating things or spending much ...... i try if possable to keep it simple