# Aluminum casting with soda cans



## Tony Wells

Everything I have been told says use materials that have been cast already, like lawnmower blocks. Alloys spec'd for casting are not pure aluminum. Crystal structure and growth needs to be controlled while cooling, so elements are added to get a strong casting.

Alloy Selection
There are a number of available alloys to choose from to satisfy individual requirements. Once the casting method is determined, the alloy choice is limited because not all alloys can be used with all casting methods. Sometimes, the alloy that shows the best properties on paper may have production characteristics that make it less desirable on an overall basis than other eligible alloys. Therefore, it is best to consult with a metalcasting facility, which can advise on such factors as availability and relative cost of ingot, production costs and reproducibility of results.

Service requirements also are a key consideration in alloy selection. If high strength is required, heat-treatable alloys must be used. The alloy options can be narrowed further when considering the remaining requirements, such as pressure tightness, corrosion resistance and machinability.

Alloy Designation Systemâ€”The U.S. Aluminum Association (AA) monitors industry standard specifications for designating aluminum alloys through a numbering system known as the AA â€œPink Sheets.â€ The system designates individual aluminum metalcasting alloys using a three-digit number plus a decimal, which is included on casting blueprints to specify the casting alloy to be used. The standard specifies the chemical composition limits of aluminum alloys and the percentage of each alloying element or an allowable chemistry range. The first digit of the three-digit number system categorizes the casting alloys by groups (or series) according to their major alloying elements.

The balance of the three-digit number identifies the various individual alloys within each alloy series. For example, the 300 series of alloys includes more than 50 individual alloys (319, 356, 357, 380, etc). Some of these individual alloys have multiple variations, all using the same three-digit number. These alloy designations include a letter before the three-digit alloy designation. For instance, variations of 356 are A356, B356, C356 and F356. This letter distinguishes between alloys that fall within the alloy chemistry ranges, but differ slightly in percentages of alloying elements or impuritiesâ€”such as F357.0, which has a lower minimum level and tighter range for magnesium than 356.0. These variations can determine special casting properties.

The Pink Sheet standard designations apply to aluminum alloys in the form of both castings and ingot, and the single digit following the decimal indicates how the alloy will be used. These designations include:

â€¢ XXX.0 = casting;
â€¢ XXX.1 = ingot used to make the
casting;
â€¢ XXX.2 = ingot used to make the casting with typically tighter chemical limits than the XXX.1 ingot designation.

If AA alloys 356.1 or 356.2, for example, are listed as the alloy specification on casting blueprints, they should define the chemistry of the ingot used to make the cast components, not the final castings. The number XXX.0 for castings includes a chemistry different from the ingot specifications. This leaves room for chemistry changes that can occur during remelting. The addition of casting returns, such as scrap castings, to the charge material also can alter the casting chemistry. The primary difference is that the XXX.0 specifications allow for some magnesium loss (due to burn out) and iron or zinc pickup that may be experienced during processing. The alloy chemistry of the final 356 cast component should fall within the limits of the 356.0 specifications but may not meet the chemical specification for the 356.1 ingot. 

Final cast components also should be properly designated. If a blueprint designates 356.1 as the casting alloy, it would be improper to designate the final castings as 356.1. Components should be shipped designated as 356.0 castings.

Metal Matrix Compositesâ€”Aluminum metal matrix composites (Al-MMCs) consist of nonmetallic reinforcements incorporated into an aluminum matrix. Reinforcements can be continuous or discontinuous, the most common being silicon carbide. Other reinforcements include boron, alumina and graphite fibers, as well as various particles, short fibers and whiskers. Al-MMCs have better stiffness, wear resistance and thermal conductivity than base aluminum alloys. The American National Standards Institute specifies that Al-MMCs be identified as follows:

Matrix/reinforcement/volume%/form.

Using this formula, a 356 aluminum alloy reinforced with 20% SiC particulate would be designated as 356/SiC/20p.


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## Tony Wells

There lots to read on the net about casting aluminum at home.

Here's a guide to casting alloys:

http://www.mid-atlanticcasting.com/alum-casting-alloys_FEB05.pdf


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## Highpower

> author=turbinedoctor link=topic=1586.msg9246#msg9246 date=1302169933
> Would old carbs and pistons be any good for casting?
> 
> Turbo


It worked pretty well for Burt Munro.....


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## rleete

> author=turbinedoctor link=topic=1586.msg9246#msg9246 date=1302169933
> Would old carbs and pistons be any good for casting?



Absolutely. Anything cast will make good castings. Old lawnmower blocks, pistons and the like are excellent. Breaking it up before adding to the pot will help speed melting significantly. It's also good stress relief!

The reason you don't want to use soda cans is volume. In order to get a decent amount of material, you have to melt a small mountain of cans. Lots of the material will be either slag or vaporized before you get a decent quantity. You'll end up burning through a whole tank of gas to get enough to pour a small part. It's just not cost effective. Adding a dozen cans to an already melted pot is okay, but starting with cans will take you forever. Remember that a large percentage (weight wise) of cans is the paint on the outside and the coating on the inside.


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## Tony Wells

Lionel, the owner of this site:

http://www.backyardmetalcasting.com/

Has even built a lathe, among other tools and equipment. It's about the best home metals casting site I have run across. Tons of project ideas and instructions there.

Not just any cast material is good, though. Some are pewter, some are magnesium, some are zinc, most are mixtures. The main problem with cans is that as thin as they are, by the time they melt, they oxidize. They make slag rather than a melt. Be careful of magnesium also. Heads, transmissions, clutch housings, pistons all make good materials for home casting. Bust it up and melt it down. 

No, Turbo....I didn't type all that up. I borrowed it.


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## fluxcored

Turbo, I've used siding, heat sinks, hard disk casings, pistons. blocks, etc for casting. I tend to stay away from cans and aluminum chips because I heard about the oxidising problem.

I've also heard if you flatten or press them sufficiently you may be able to get a useful melt but who needs the extra aggro.

What I also heard and would like comments on from the experts, is to improve your melt you can add borax and table salt to it. If I remember correctly borax boils off the impurities while the salt helps the melt to flow much better when casting. I may have it wrong though.


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## Highpower

I've used Borax before in lead alloy melts as a flux to clean the metal. It's my understanding that if you leave a layer of it on top of the melt, it seals off the metal from the air and helps protect it from oxidizing. That works OK in a bottom pour furnace, but not much help when pouring from a crucible I suppose. It does make a mess of things though, and I didn't like using it.

I don't know much about smelting aluminum - did it in H.S. metal shop but that was a long time ago.   
Adding salt to an already corrosion prone metal just doesn't sound right to me. I would be interested in hearing others thoughts on this.


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## Gadget

turbinedoctor said:


> Would old carbs and pistons be any good for casting?
> 
> Turbo


I think you'll find old carbs are made of zink, not aluminum. Be careful when melting zink, it gives off a poison gas.


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## Alaskan

Old aluminum ladders work great also. I have also used grates, pieces of machinery ect.  I have people give me all kinds of broken parts of machines. I've done the can thing and ended up throwing most of it away after it was melted.


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## Chucketn

Adding my 2¢. Sell your cans and buy any type of previously cast aluminum. Car wheels are the best. Computer hard drives are good. I have tried melting aluminum cans and you loose 75% or more to slag or aluminum contaminated with crap that makes it worthless.
I have melted aluminum in a bean/coffee can, on a charcoal fire, in a galvanized bucket, with a hair dryer blower, but that is not the best/easiest way.
You can break down car wheels by heating them in a fire to the 'short-hot' point where they will crumble with a hit from any kind of hammer.
There are lots of home foundry type site with lots of information on casting aluminum.
That's a hole 'nother hobby!

Chuck


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## jocat54

I'll throw my .02 cents in here. I'm pretty new at the casting game and melting aluminum so take all this with a grain of salt. The only thing I have melted so far are aluminum cans. They are a pain in the behind, but if it's all you have at the time you can get some decent casts from them. I usually melt the cans and pour them into muffin pan and use them later (much better the second time around) There will be alot of slag, just skim it off and keep adding cans (crushed work much better).

The really down side is the cost of propane per melt verses how many cans it takes to get a good pour, but it's a good learning time. It took a whole 5 gal bucket full of crushed cans to get enough to pour a cylinder about 2.5 inches by 6 inches with very little left over. 

I made my ball turner and carriage stop from pop can melts and they work good and look pretty good too:biggrin:

I live out in the sticks so I don't have much to pick from, need to plan my trips to the city better.


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## GK1918

All I can add is qouple miles away is a real foundry and what a mountain of transmissions they have. They buy off tranny shops and junkyards check your
local tranny shop, bet they got a pile of housings smash em with a sledge and
lite the fire.


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## Kevinb71

I have done a few melts and to me pistons, engine heads and block work best. It only makes sense as well that they would be made of a stronger grade of alumininum due to there intended usage. I have never tried aluminum cans as everything i have ever read says it's not worth the effort. Too much slag for what you get back.


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## Video_man

turbinedoctor said:


> Anybody done this. I have heard they are not a good choice for casting due to been too pure, what ever that means. Turbo



Extruded items like cans are nearly pure Aluminum, which is gummy and doesn't pour well.  The metal used for aluminum castings is not just aluminum alone, but one of many alloys, with such things as silicon added to give the base metal the characteristics it needs to cast well.  Cans are also usually coated with lithographs and plastic coatings and basically make a mess of slag when you try to melt them in a small furnace.  The adage to cast metal that has already been cast is a good one, because it will surely be an alloy made for the purpose.


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## core-oil

Hi guys,

   I feel excercised to add my two pence worth, I served my apprenticeship in the foundry industry many years ago,  One of the materials we made castings for various industries for was Aluminium,  Some of it was to aircraft specification, However saying that & thinking of my experiences of all those 54 years back, a couple of years before that i was on cast-iron work, before being switched over to brass , bronzes &light alloy work, making components at home as distinct from ones nicely set up in a  more proffessional industrial sphere is a different ball game

    Nowadays i do not know what the modern metal specifications are especially over the pond in the U.S. or Canada, & i guess i am too old to start learning now, but taking some simple rules from my ex industrial days ,   When, i want to make up a component in my backyard facility at home,   The things i turn out, are the occasional jig or fixture to make life easy, backplates, brackets, pulleys etc 

   When i worked in the metal casting game one of the metals we used to get landed with on the rare occasion was on the old British metal specification  LM1 (L.M. meant light metal-- Brilliant aint it!) this was an almost pure metal in fact from memory 99% i believe , It could if you were not careful lead to great voids in the casting ,shrinkages &other problems, So therefore bigger feeding heads were the name of the game 

   A better metal was LM 4  formerly DTD 424  This basically was a metal with a good percentage of silicon in its make up, by and large it was a metal which poured pretty easily with not a great deal of feeder head problems , A higher spec. metal was L.M.6 which was a metal of higher tensile strength etc

   O.K. guys, where does this lead to with you folks? I assume you are only making the occasional little widget in your back yard for your model engine,workshop use etc    Should you be making things for industry , aircraft etc, back off guys, unless you have a lot of metallurgical knowledge & know what you are about, otherwise you are in a real minefied!

   So therefore making things for fun, myself & nobody else where i cannot be screwed up by litigation etc, backyard foundry work can be fun, and gives another dimension to Hobby Machining , Athough safety first is the name of the game Keep that upermost in your psyche, Hot metal is unforgiving stuff, especially when mixed with water.

  Right guys raw materials___  scrap cans are by and large a pain in the butt due to impurities, a pile like a mountain for very little return for your effort, & always the danger of horsing a can into the melting pot with some liquid in the bottom (not advisable)   What do i use ? Luckily i have a friendly scrap dealer who sells me suitable pieces of scrap alum, at a reasonable price    Motor car pistons, are ideal , other scrap cast stuff is fine, i also tend to mix in my pot a fair %centage of extruded scrap, aluminium angle, beading etc , The pot i use gives me a max of 15lbs. of molten metal

    A pitfall for home workers, is heating the metal up till it is screaming hot, thus causing oxidation a burning,  What i tend to do is gently melt till the metal looks like a mirror, after skimming off the slag, then give some extra heat till the metal is a light pink, Just above the silvery mirror stage, this gives me a metal capable of flowing in the mould to 1/8" section   Over here in the U.K, we unfortunately have seen the closure of a sand quarry which gave us a nice greensand, called Mansfield Red  now a lot of firms & amatuers are going down the road of making up a Bentonite based synthetic mixture

  Should care be taken, i find on most of my hobby stuff , i can melt a good clean melt without degassing  procedures, -- remember with Aluminium you cannot de-oxidise, Only degas,    In aluminium, Oxide is always present, it may be a miniscule level ,but always there,      You may do  as industry does, Which is,   reduce it, till it is so minimal as to be of no problem 

   The home craftsman cannot hope to emulate the industrial folks who can afford to vacuum melt, nitrogen degass etc.

  One of the biggest problem for the home guys is working out your running &riser systems + cleanliness in your mould, no breaks debris or loose parts to break off   Practice, & experimentation   That is the key to success.


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