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steve
11-16-2004, 09:43 PM
guys i've got a couple questions on aluminum. there are 200+ types out there, are these all man made variations, or are different types mined?
will mixing different types affect my castings?
what about aluminum wire i had thought it to soft but recently saw web site where they used wire. will it harden after being heated and cast? i can get all the wire i want free!

SJorgensen
11-16-2004, 09:52 PM
All aluminum is man made. It doesn't exist in nature in its metalic form and yet it is the most abundant metal in the form of bauxite. All the variations are due to alloying with other metals and compounds. Pure aluminum also readily absorbs nitrogen when molten and this gas tends to bubble out when you cast causing pinholes in the metal. So you need degassing compounds. If you cast with metal from castings like transmission housings there will often be enough residual degassing compounds for you to get a good result. I would probably grab all that wire and melt it down. It might be labor intensive getting that jacket off it though.

Good luck,

Spence

wierdscience
11-16-2004, 10:03 PM
Spence is right,you can melt almost anything down and cast it,but the level of difficulty will vary depending on what the melt contains.
Extrusions like screen door frames and TV antennas mixed 50/50 with things like transmisson cases make for a good pour.
Also you can make simple alloys yourself.One old alloy used to make aircraft engine components in the 30's and 40's was 92/8.Thats 92% aluminum and 8%copper by volume.
You simply melt the aluminum and skim off the dross,then preheat and drop in(using tongs)the copper,once the copper hits the aluminum it begins to dissolve and in a matter of minutes will nearly completely dissolve and form the desired alloy.
You might wonder what about all the rest of the stuff in the aluminum base melt.Well to answer that I use crushed aluminum cans for the base.They are nearly pure aluminum and not so good for casting by themselves,but add the copper and it improves dramatically.What you end up with are ductile casting that are easy to machine.
If you don't want to pickup your own cans do what I do and buy them from the scrapyard,most times I even get them crushed already for a few cents over what the yard pays.

[This message has been edited by wierdscience (edited 11-16-2004).]

Elninio
11-17-2004, 10:01 PM
i've heard that the aluminum from pop cans isnt real low quality , is this true? Also you know how some of the higher quality aluminums like 6061 arent 100%, they are mixed with other metals.. IF i were to re-melt for example chips from machining it earlier, would it be same quality or would it have decreased in quality?

ibewgypsie
11-17-2004, 10:16 PM
Aluminum wheels are my favorite, busted mags..

They are bringing 6$ a piece to the junk dealers now thou.

David

sdeering
11-17-2004, 10:39 PM
I think I read somwear you should leave the dross on top of the molten aluminium until the pore, keeps it from oxidizing I think.
Any home made sand recipes out there. I tried green diamond sand mixed with I think 10% bentonite and water.
Also tried an oil based petrobond home recipe, sand, synthetic 2 stroke oil, special bentonite like product used as an oil based drilling rig mud and a little alcohol. Second worked the best.

ben78
11-18-2004, 01:46 AM
Elninio - 6061 is an Alloy, therefore it is a mixture of Al and other metals. If you collect the chips you need to be 100% certain that you are collecting chips only, no lube, no iron, no paint etc. The larger the surface area of whatever you melt (eg chips and cans have a large surface area) the more dross you will have.

I leave the dross until I am nearly done, then skim and pour. Any oxides that form after skimming are just going to float, I am not producing commercial quality castings, just bearing blocks and the like so it doesn't worry me, same goes for the steel pipe crucible, a bit of dissolved iron doesn't worry me.

My favourite casting source? old sand cast engine heads and blocks. Cheap as and a source of kg's of alloy per block.

Mike Burdick
11-18-2004, 03:01 AM
For those interested, here's some information about melting and casting in your backyard:

http://users.frii.com/katana/castindex.html

WJHartson
11-18-2004, 03:05 AM
Bauxite is mined and then processed through the Bayer process to produce alumina, the white power, Al203. In a reduction process, Hall process, aluminum is refined. The aluminum is typically 99.85% aluminum and the remainder is mostly silica and iron as impurities. This is called P85 metal.

All of the alloys of aluminum are mixed with other elements to produce the desired alloy.

Typically electrical wire is 1100 series aluminum and is not a heavy alloy. Drink cans are typically 3003 for the body and 5182 for the lid. There is always a remelt loss of 2% or more depending on how you are melting the solid material. The melt loss will be a lot greater in a noncontroled environment. During the reheat process some of the alloying elements will burn off so you will not have exactly what you started with. When you mix different alloy in a heat you can end up with anything. Sometime you have to sweeten it with P85 metal and them add the alloying elements that you want. Chlorine is used as a fluxing agent to drive out the impurities and causes the dross to form.

One caution that you must be aware of with molen aluminum. If you pour molten aluminum into water you can produce a very violent explosion. Cast houses have been leveled when this happens. Alcoa did some testing and the results were dramatic. The first test they did completely distroyed the bunker they built to contain the explosion. Be careful.

When aluminum is cast as it cools some of the alloying element freeze out first into the skin of the casting in larger proportions than in the rest of the casting.

Hope this helps a little.

Joe

gkman11
11-18-2004, 07:53 AM
SDEERING, I'd like to hear more about the home recipe for petrobond.

sdeering
11-18-2004, 09:05 AM
I think I have it at home on my computer. Just finishing off a night shift,I will check and post tonight.
I do remember the modified bentonite was pricey 200 beans. I have a friend that is a mud man amazingly he happened to find one just laying around for free.

wierdscience
11-18-2004, 09:17 AM
The home made petro-bond sand works good,but absolute tops is the resin bond.
The resin and hardner costs about $55-65 each for a five gallon pail.That is enough to mix up 1100 lbs of sand,too much?Not really,the stuff has a long shelf life so long as its not cross contaminated.

The thing I like most about it is the property of producing a durable mould,it sets up hard and doesn't require raming,it can be just vibrated into the cope.
The other added feature is if you have a crucible furnace you can pour anything you can melt into it,aluminum,brass,bronze even cast iron is a one shot product.

Involute
11-18-2004, 09:30 AM
Give this link a try for the homemade petrobond sand...

http://www.ray-vin.com/casting/k-bond.shtml

Rustybolt
11-18-2004, 09:43 AM
<font face="Verdana, Arial" size="2">Originally posted by Elninio:
i've heard that the aluminum from pop cans isnt real low quality , is this true? Also you know how some of the higher quality aluminums like 6061 arent 100%, they are mixed with other metals.. IF i were to re-melt for example chips from machining it earlier, would it be same quality or would it have decreased in quality?</font>


Alum. cans are their own alloy. Formulated for deep drwing and not tearing.
Like others have said; you'd be better off with old alum wheels or pistons or pots and pans for that matter.

mikem
11-18-2004, 10:32 AM
You might want to take the wire you can get for free and trade it at the scrap yard for some aluminum pistons from a car engine--they are made of a better alloy to cast. The scrap dealer probably won't want to make an even trade, but even at 2 for 1, you come out fine since your wire was free to you. Aluminum cans are made from an alloy that is too ductile to machine easily. It gums up on tooling, smears and leaves big burrs on the cut edges of your work. The piston alloy machines, drills and taps well.

HTRN
11-18-2004, 06:25 PM
<font face="Verdana, Arial" size="2">Originally posted by Rustybolt:

Alum. cans are their own alloy. Formulated for deep drwing and not tearing.
Like others have said; you'd be better off with old alum wheels or pistons or pots and pans for that matter.</font>

Are you sure? I could have sworn that Aluminum cans were almost pure aluminum.

I have heard they make lousy castings and with thinlining going on(making products with less material, Soda bottles for example) it doesn't make it worth the trouble.

HTRN

sdeering
11-18-2004, 09:25 PM
The recipe I was using was the one INVOLUTE posted.

suprdvn
11-19-2004, 01:18 PM
"I could have sworn that Aluminum cans were almost pure aluminum."

Pure aluminum is like pure river water http://bbs.homeshopmachinist.net//wink.gif .

Aluminum is an alloy. It's made up of varying amounts of several metals. Changing the percentage of the ingredients changes the charactoristics.
WJHartson explains it well (see post above).

Tuckerfan
11-19-2004, 06:14 PM
Depending upon the final use for your casting, degassing may not be necessary. If it's primarily ornamental, with little machining being done to it, then I wouldn't worry about it. If you're going to be doing something a little more intensive with it, like footpedals for a motorcycle, or something where someone could be seriously injured if the casting failed, then I highly recommend that you degass the aluminum. You can buy chlorine tablets at swimming pool supply places, just make sure that it gets to the bottom of the crucible. And drop it in, about 30 minutes or so before you're ready to pour.

SJorgensen
11-19-2004, 09:55 PM
Chlorine tablets?

I bought degassing tablets from a supply house and it smelled more like naphthalene or mothballs.

Chlorine tablets are a strong oxidizer and they burn pretty good too. Wouldn't they ignite immediately or oxidize the aluminum?

Is it safe?

Also I've found it better not to keep the metal molten any longer than necessary. 30 minutes is getting long. Heat, degass, skim, pour.

[This message has been edited by SJorgensen (edited 11-19-2004).]

HTRN
11-19-2004, 10:13 PM
Superdvn: Yes "commercially pure".. I'm not talking about something from a lab...

McMaster Carr calls alloy 1100 "commercially pure". It has .95 Silicon and trace amounts of other elements.

Apparently it's often used in chemical processing...

By your reasoning there are no elements available because there are always trace amounts in them. the difference between Commercial and Lab pure is the allowable ammounts.

HTRN

------------------
This Old Shed (http://http:thisoldshed.tripod.com/enter.htm)

WJHartson
11-20-2004, 12:32 AM
Aluminum and aluminum alloys are labeled within a numbering system The first number in the system tells the major alloying element.

1xxx is considered non-alloyed all trace element with the exception of Silicon and Iron (FE)is less than 1.0 max. 1100 is 99% pure aluminum.
2xxx has the major alloy as copper, up to 6.8% and nickel up to 2.3% in a couple of the alloys.
3xxx has manganese up to 1.5%
4xxx has silicon up to 13.5%.
5xxx has magnesium up to 5.5%
6xxx has a higher percentage of many of the element than in others alloys.
7xxx has zinc up to 8%.

Silicon and iron are contaminent that occur because of the electrolitic process in smelting aluminum. Aluminum that is 99.85% pure is considered pure aluminum. Five nine metal ie 99.999% pure aluminum can be obtained through a second refining process but it is very expensive and takes special equipment.

Beverage can are made using the Draw and Iron process. Gage control across the sheet, finish (ra)on the sheet and the coolent used during the can making process is critical to making good cans. Tearoffs are a killer in the process. Can makers don't want any. Can stock was a rolling mills base product many years ago. Today Alcoa makes most of it. As the controls got tighter on can stock many mills stopped making it because they could not compete with Alcoa's quality.

Joe

Tuckerfan
11-20-2004, 01:32 AM
<font face="Verdana, Arial" size="2">Originally posted by SJorgensen:
Chlorine tablets?

I bought degassing tablets from a supply house and it smelled more like naphthalene or mothballs.

Chlorine tablets are a strong oxidizer and they burn pretty good too. Wouldn't they ignite immediately or oxidize the aluminum?

Is it safe?

Also I've found it better not to keep the metal molten any longer than necessary. 30 minutes is getting long. Heat, degass, skim, pour.

[This message has been edited by SJorgensen (edited 11-19-2004).]</font>

Well, they've never caught fire when we've used 'em at work. I'm not sure exactly how pure they are. Cholrine readily bonds to the hydrogen which can form in the aluminum and cause embrittlement. As for the 30 min, that's a rough guesstimate, and we melt about 100 pounds at a time, and after we degass with chlorine, we do another degass with oxygen, once that's done, we check the temp, and then if it's right do a pour.

SJorgensen
11-20-2004, 01:44 AM
Thanks Tuckerfan,

I'm in no way trying to contradict you but I am just surprised! I've just enough chemistry education to understand reactions when you introduce oxidizers with things that is can react with, like hydrogen or even aluminum.

Can it be used when melting magnesium?

Obviously I'm no chemist or metalurgist. If it works, it works.

Thanks,

Spence

Tuckerfan
11-20-2004, 03:45 AM
<font face="Verdana, Arial" size="2">Originally posted by SJorgensen:
Thanks Tuckerfan,

I'm in no way trying to contradict you but I am just surprised! I've just enough chemistry education to understand reactions when you introduce oxidizers with things that is can react with, like hydrogen or even aluminum.

Can it be used when melting magnesium?

Obviously I'm no chemist or metalurgist. If it works, it works.

Thanks,

Spence</font>
I wouldn't try it with magnesium. We're helping some metallurgist do some experimental research with new types of magnesium alloys, and we've been pumping lots of argon into the mix, and still haven't been able to keep it from catching fire.