Author Topic: ALU melting  (Read 15211 times)

Offline NormanV

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Re: ALU melting
« Reply #25 on: February 21, 2015, 07:02:45 AM »
Will, I built a foundry when I lived in the Falkland Islands and buying refractory cement was definitely not possible. It was possible to buy 1 kg tubs of ready mixed fire cement but to build the whole foundry with that would have cost a couple of hundred pounds. Instead I bought four pots of it, thinned it down with water and mixed it with "grog" that I made by breaking up and passing through a 1" mesh sieve a load of fire bricks that I managed to scrounge. It turned out to be entirely successful, no cracks appeared in it even after many firings. The lid was made of the same stuff in a sheet metal ring with wire reinforcement criss-crossing it.
For moulding sand I used sand from the local sand dunes mixed with fullers earth cat litter.

Offline Eugene

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Re: ALU melting
« Reply #26 on: February 21, 2015, 09:42:45 AM »
Will,

I'm doing the planning for a foundry too; one of the better internet sources for all things home machinist is "Mikes Workshop" as per http://mikesworkshop.weebly.com/furnace.html

The mix he used in his set up is .....

1. Portland cement - 1 part by volume
2. Clay - 1 part by volume. I used clay based cat litter. This is available from most supermarkets
3. Perlite - 7 parts by volume.

Looks simple enough and details of the mixing procedure are given on the site; I think I'll go with this procedure.

Eug
« Last Edit: February 22, 2015, 04:34:10 AM by Eugene »

Offline vtsteam

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Re: ALU melting
« Reply #27 on: February 21, 2015, 10:51:32 AM »
No, do not use portland cement., it won't last, it will calcify. That occurs at 600C or about the melting temp of aluminum. Use of Portland cement by amateur foundry makers has been an ongoing problem ever since Lionel Oliver first put up a portland cement furnace on his website in the early 2000's -- however he at least used a flowerpot liner (clay) so not as bad as people who use portland cement directly with no protection for the material.

Plaster of Paris (gypsum)  is MUCH more refractory -- it's used in bronze casting as a molding material -- bronze pours at a lot higher temperature than aluminum melting temps -- Mattinker can tell you and has personal experience.

Also in industry, plaster of Paris pouring basins and liners are used for even iron. Plaster of Paris has a high insulation value there, which is why it is used -- see Steve Chastain's molding books for references to this. And on the popular internet video scene, plaster of Paris is used in numerous small benchtop forge videos and ripoff videos. One of the more popular is mentioned in the intro to this thread's flick.

As I said, my objection to this video is not with the furnace body, but with the cavalier disregard of coatings combustion products.

I've just built a new furnace with a plaster of Paris sand mix, so if you want to know how well it works, I'll be able to tell you shortly

There are other references to using Plaster of Paris with bronze on sculpture casting art sites.
I love it when a Plan B comes together!
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Offline vtsteam

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Re: ALU melting
« Reply #28 on: February 21, 2015, 11:00:08 AM »
Also, you can melt aluminum in practically any furnace composition that will stand the heat -- a woodstove for example with hot embers in it, a hole in the ground, a woodfire, loose or bound bricks, a steel box or barrel, etc. People make a big deal out of it, and that can be fun, buying expensive stuff, and doing high tech things, but if you don't have money or access, you can still melt ALU.
I love it when a Plan B comes together!
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Offline vtsteam

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Re: ALU melting
« Reply #29 on: February 21, 2015, 11:26:29 AM »
I just looked at the Mikes workshop furnace, and pretty much guaranteed that the Portland cement on the inside face has calcified and it's the clay and perlite that is now holding it together in the hot area. Still, if it works it works. The cement cures quickly to form, so useful that way, but you do need clay and perlite to make it work. Many have tried pure portland cement furnaces without understanding and those have failed over time or if overheated -- brass melting, etc.

I'm hoping that the sand/gypsum mix will allow bronze melting and steel forging as well as aluminum melting.
I love it when a Plan B comes together!
Steve
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Offline ian_in_the_midlands

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Re: ALU melting
« Reply #30 on: February 21, 2015, 02:57:47 PM »
At the risk of hijacking the thread (maybe a new one should be started?), I thought I would mention my favourite 'don't try this yourself' Youtube video:

     


The fun starts at about the two minute mark.
« Last Edit: February 21, 2015, 04:04:50 PM by dsquire »

Offline awemawson

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Re: ALU melting
« Reply #31 on: February 21, 2015, 04:07:56 PM »
I can't believe he's pushing that through the table saw with his fingers and not a pusher - crazy man  :bugeye:
Andrew Mawson
East Sussex

Offline dsquire

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Re: ALU melting
« Reply #32 on: February 21, 2015, 04:36:00 PM »
At the risk of hijacking the thread (maybe a new one should be started?), I thought I would mention my favourite 'don't try this yourself' Youtube video:

     


The fun starts at about the two minute mark.

Ian

I guess that this lad has no future use for his hands and fingers. Some guys just don't seem too have much between their ears.  :zap:

Andrew

Not only the curved rails but also several other cuts are way above my comfort zone.  :poke:

Cheers  :beer:

Don

ps: Andrew, I had started mine before you posted yours.  :D
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Offline philf

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Re: ALU melting
« Reply #33 on: February 21, 2015, 05:09:31 PM »
Quote

I guess that this lad has no future use for his hands and fingers. Some guys just don't seem too have much between their ears


Although he did care about his ears - he was wearing ear defenders - bizarre!
Phil Fern
Location: Marple, Cheshire

Offline Eugene

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Re: ALU melting
« Reply #34 on: February 21, 2015, 05:12:21 PM »
Steve,

Thanks. Just what mix of Plaster of Paris and other thingies do you recommend? 'Tis all very confusing.

Eug


Offline vtsteam

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Re: ALU melting
« Reply #35 on: February 21, 2015, 06:17:52 PM »
Eugene, I really didn't mean to play down Mike's mix, if it sounded that way -- I realized after my first reaction to Portland that the clay and perlite were what made it work well, and the cement just gives it shape and quick drying. In back of the hot face I'm sure the cement is well insulated by the perlite, so unaffected. It's actually a smart mix, and I like it. I'm sure you can melt ALU well with that.

And to be even more honest at this point, I really can't recommend a poP mix, since I'm just trying one out now, but I promise to tell (and show) how it works out, good or bad. I'm using equal parts poP, sand, and cold water for my mix.

See here for whatever happens:

http://madmodder.net/index.php/topic,10482.0.html
I love it when a Plan B comes together!
Steve
www.sredmond.com

Offline RussellT

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Re: ALU melting
« Reply #36 on: February 22, 2015, 05:21:27 AM »
Hi Steve

Have you considered High Alumina Cement instead of Portland - a bit harder to find but not that difficult here.

Russell

Offline Eugene

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Re: ALU melting
« Reply #37 on: February 22, 2015, 05:25:35 AM »
I might just pick up on Norman's idea and use two or three pots of fire cement instead of the Portland in Mike's mix. I've got one to hand already.

Just to pick up me laddo in the video .... what a shame he shows such unsafe working practises. He's obviously a pleasant and inventive sort of cove with artistic talent and practical skills that I admire, but as the saying is "I've grown attached to my hands".

Eug

Offline vtsteam

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Re: ALU melting
« Reply #38 on: February 22, 2015, 10:14:04 AM »
Eugene, I don't know what is available over there, or for him when Norman built his. I used perlite and tubbed Rutland brand (US) furnace cement on my first furnace as the lid (not the body, which was strictly fireclay and sand, per Gingery.)

I found that the lid cracked flaked off in chunks and deteriorated fairly quickly and I was patching it frequently. Here (and it may be different where you are) tubbed wet furnace cement is made up of sodium silicate (water glass) and clay. It's main use is in fireplaces between frebricks, where it is well protected.

The label heat rating isn't very high for a metal melting furnace. In short, it works for aluminum, or did for me, but isn't very refractory against furnace flames, and requires frequent patching in my experience (and the brand and type available). Your mileage may vary.
I love it when a Plan B comes together!
Steve
www.sredmond.com