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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

Melting aluminium / magnesium alloy



 
 
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  #1  
Old November 21st 04, 03:08 PM
Richard
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Default Melting aluminium / magnesium alloy

In pyrotechnics we use an alloy of 50:50 magnesium / aluminium called
magnalium, this is a very brittle material that is very useful in fireworks
manufacture. I would like to attempt to manufacture some and wondered what
might the best way to go about it.

My idea is to take a cast iron pot with lid, place equal amounts of metal
within, and then put the pot on an enclosed kettle bbq with a good charcoal
fire built around it. To increase airflow I was thinking perhaps something
along the lines of a leaf blower or hair dryer connected to the bbq air
vent. I'm confident that the metals should mix sufficiently by themselves
assuming they reach melting point. Accuracy is not too important for these
purposes.

Reckon this sounds viable on a backgarden scale with limited budget?
--
Richard H
UKRA#1172 L2 Cert
NSRG#008
http://www.ukrocketry.co.uk
http://www.neodaemos.co.uk
richard [at] ukrocketry [dot] co [dot] uk

'We can produce in air sounds as loud as thunder and flashes bright as
lightning'
Roger Bacon


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  #2  
Old November 21st 04, 04:01 PM
AZOTIC
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Default

In pyrotechnics we use an alloy of 50:50 magnesium / aluminium called
magnalium, this is a very brittle material that is very useful in fireworks
manufacture. I would like to attempt to manufacture some and wondered what
might the best way to go about it.

My idea is to take a cast iron pot with lid, place equal amounts of metal
within, and then put the pot on an enclosed kettle bbq with a good charcoal
fire built around it. To increase airflow I was thinking perhaps something
along the lines of a leaf blower or hair dryer connected to the bbq air
vent. I'm confident that the metals should mix sufficiently by themselves
assuming they reach melting point. Accuracy is not too important for these
purposes.

Reckon this sounds viable on a backgarden scale with limited budget?
--
Richard H
UKRA#1172 L2 Cert
NSRG#008
http://www.ukrocketry.co.uk
http://www.neodaemos.co.uk
richard [at] ukrocketry [dot] co [dot] uk

'We can produce in air sounds as loud as thunder and flashes bright as
lightning'
Roger Bacon


Molten magnesium in a air atmosphere is quite exciting to say the least,
the alloy you desire requires smelting the two metals in a oxygen free
enviroment, a bbq will not meet these requirements. I suggest you purchase
the alloy ready made from a metals supplier, far to dangerous to attempt
to cook up some at home without the proper equiptment.

Best Regards
Tom.

  #3  
Old November 21st 04, 04:41 PM
Richard
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"AZOTIC" wrote in message
...

Molten magnesium in a air atmosphere is quite exciting to say the least,
the alloy you desire requires smelting the two metals in a oxygen free
enviroment, a bbq will not meet these requirements. I suggest you purchase
the alloy ready made from a metals supplier, far to dangerous to attempt
to cook up some at home without the proper equiptment.


The metals will be contained in a cast iron pot with a heavy lid, I suspect
that only a limited amount of oxygen is going to get in, and even then an
oxidised layer on the top of the melt should stop any further oxidation. My
theory anyway! I've read of pyrotechnists trying this without incident, so
my main concern is generating the heat to melt the metals sufficiently.

Obviously I will be taking precautions just in case something happens, I'm
well aware of the reactive nature of magnesium and aluminium, afterall this
is why we use them in fireworks :-)
--
Richard H
UKRA#1172 L2 Cert
NSRG#008
http://www.ukrocketry.co.uk
http://www.neodaemos.co.uk
richard [at] ukrocketry [dot] co [dot] uk

'We can produce in air sounds as loud as thunder and flashes bright as
lightning'
Roger Bacon


  #4  
Old November 21st 04, 04:51 PM
Peter Fairbrother
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Richard wrote:

"AZOTIC" wrote in message
...

Molten magnesium in a air atmosphere is quite exciting to say the least,
the alloy you desire requires smelting the two metals in a oxygen free
enviroment, a bbq will not meet these requirements. I suggest you purchase
the alloy ready made from a metals supplier, far to dangerous to attempt
to cook up some at home without the proper equiptment.


The metals will be contained in a cast iron pot with a heavy lid, I suspect
that only a limited amount of oxygen is going to get in, and even then an
oxidised layer on the top of the melt should stop any further oxidation. My
theory anyway! I've read of pyrotechnists trying this without incident, so
my main concern is generating the heat to melt the metals sufficiently.

Obviously I will be taking precautions just in case something happens, I'm
well aware of the reactive nature of magnesium and aluminium, afterall this
is why we use them in fireworks :-)


On your head be it ...

I have sucessfully melted aluminium on a ceramic electric kitchen cooker hob
in a stainless steel cooking pan with a glass lid. IIRC magnesium has a
similar mp.

I'm in the UK though, and we have proper electricity (240V) here.


--
Peter Fairbrother

  #5  
Old November 21st 04, 05:04 PM
Richard
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Default

"Peter Fairbrother" wrote in message
...

On your head be it ...

I have sucessfully melted aluminium on a ceramic electric kitchen cooker
hob
in a stainless steel cooking pan with a glass lid. IIRC magnesium has a
similar mp.

I'm in the UK though, and we have proper electricity (240V) here.


I am also based in the UK, I never gave thought to an electric element based
setup, obviously outside and well away from anyone or anything! I still
reckon a charcoal fire would be the cheapest and quickest option.
--
Richard H
UKRA#1172 L2 Cert
NSRG#008
http://www.ukrocketry.co.uk
http://www.neodaemos.co.uk
richard [at] ukrocketry [dot] co [dot] uk

'We can produce in air sounds as loud as thunder and flashes bright as
lightning'
Roger Bacon


  #6  
Old November 21st 04, 05:39 PM
Peter Fairbrother
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Default

Richard wrote:

"Peter Fairbrother" wrote in message
...

On your head be it ...

I have sucessfully melted aluminium on a ceramic electric kitchen cooker
hob in a stainless steel cooking pan with a glass lid. IIRC magnesium has a
similar mp.

I'm in the UK though, and we have proper electricity (240V) here.


I am also based in the UK, I never gave thought to an electric element based
setup, obviously outside and well away from anyone or anything! I still
reckon a charcoal fire would be the cheapest and quickest option.


Saw your sig. Were you at K-Lob? I'm the turbopump guy.

--
Peter

http://www.m-o-o-t.org

  #7  
Old November 21st 04, 05:53 PM
Richard
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Default

"Peter Fairbrother" wrote in message
...

Saw your sig. Were you at K-Lob? I'm the turbopump guy.


We did the big firework display on the Saturday night :-)
--
Richard H
UKRA#1172 L2 Cert
NSRG#008
http://www.ukrocketry.co.uk
http://www.neodaemos.co.uk
richard [at] ukrocketry [dot] co [dot] uk

'We can produce in air sounds as loud as thunder and flashes bright as
lightning'
Roger Bacon


  #8  
Old November 21st 04, 08:00 PM
Harold & Susan Vordos
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Default


"Richard" wrote in message
...
snip-

I'm confident that the metals should mix sufficiently by themselves
assuming they reach melting point. Accuracy is not too important for these
purposes.

Reckon this sounds viable on a backgarden scale with limited budget?


It doesn't sound viable to me. My experience with molten metals over the
years tells me that the metals, assuming you achieve success in melting them
without a fire, are unlikely to become a homogeneous alloy. They have
little reason to unless you give them some type of stirring action. When
melted by induction in an inert atmosphere, the heating method serves that
purpose. Unlike gasses, metals do not always distribute themselves
evenly when combined, although they will do so when assisted. Some metal
combinations will stratify given the opportunity. Silver and iron, for
example. You're also going to have to come to terms with the fact that iron
will be absorbed by the molten metal. Dunno what affect it will have on the
purpose, but it's not a good idea when melting aluminum for casting.


Harold


  #10  
Old November 22nd 04, 01:57 PM
Doug Goncz
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I'd say melt the Al, add a flux cover, and then dissolve the Mg into the Al
most safely, in chunks not overflowing, to your rough 50:50. And have dry sand
available at the very least. Preferable ground coal to soak up oxygen should
you experience ignition. It's a delicate balance between heat input, molten
temperature, and time spent dissolving MG into Al.

The more time at idle, the more Zn will fume out of your Al, if there's any.
Zinc chills. Brr. And other compositional elements will boil out, but mostly
ingot Al is pretty stable.

Then, as it cools, you stir it as it freezes to break it up, like making ice
cream. You get a coarse powder that way.

Don't stir it vigorously while it's real hot!

Bah. I have a photo from a friend here showing a pool of shiny metal
inside a crucible inside a furnace, written on the back is "1.5 lbs of
freshly skimmed MagNESIUM (4Al) @ 1250F" (his capitalization :P ).


And when he poured it, did it go actinic?

The secret commercially is either a gas or flux cover. The latter
would be a salt 'alloy', such as equal parts sodium and potassium
chloride (can be had at the grocery store as "lite salt"; has to be
fused (mmm, salt ingots!) before use), with other select ingredients
to lower the melting point and improve fluxing action.


Love the stuff. Love frozen dinners, too, but what a wallop of sodium.

Maybe try 1/4 your smallest crucible one day, then upgrade....

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