# Casting aluminum on a backyard



## r3292c

I'm not casting a lot, neither often. I'm casting more for fun.
I started casting aluminum a couple of years back. I bought some natural clay bricks in Home Depot and built a primitive foundry. I don't use any kind of cement to glue the bricks together. No, I put them together only when I need a foundry. And store them in a shed when I don't need it.
In the beginning I was using charcoal briquettes as a fuel, and old hair dryer without heater as a blower. That setup worked well enough.
The clay-grafite crucible is from Amazon.




I tried Styrofoam casting, green sand casting, as well as plaster mold casting.







Then I switched to propane torch, it's much cleaner.
Here is a video of my latest casting. By the way, that bricks I bought a couple of years back are still alive.


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## Shootymacshootface

I have only smelted and cast lead alloys for making bullets. 
Do you have to flux and mix the alloy before casting? Or do the alloys in the aluminum stay suspended on their own?


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## r3292c

The pieces of aluminum that had been casted are preferred. Extrusion aluminum isn't good for casting. Soda cans is one of the worst source of aluminum - extrusion, too thin, and too much dross. Aluminum chips are also not good for casting. Some people do mix aluminum and zinc, but zinc vapors aren't healthy.


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## Aukai

Darn, last year I recycled 4 cast aluminum rims from my wife's Monte Carlo, and got 25 bucks for 4 of them. What grade of aluminum would you end up with if melting down car wheels?


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## vtcnc

Aukai said:


> Darn, last year I recycled 4 cast aluminum rims from my wife's Monte Carlo, and got 25 bucks for 4 of them. What grade of aluminum would you end up with if melting down car wheels?


I imagine a better grade than aluminum cans!


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## benmychree

Pistons are also a poor source of scrap, permanent mold castings contain iron, which prevents the metal from sticking to the molds, and iron narrows the solidification range of the molten metal, making it necessary to pour excessively hot to fill the mold, resulting in excessive shrink and hot tears.


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## Shootymacshootface

benmychree said:


> Pistons are also a poor source of scrap, permanent mold castings contain iron, which prevents the metal from sticking to the molds, and iron narrows the solidification range of the molten metal, making it necessary to pour excessively hot to fill the mold, resulting in excessive shrink and hot tears.


Good to know. Thanks!


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## benmychree

Shootymacshootface said:


> I have only smelted and cast lead alloys for making bullets.
> Do you have to flux and mix the alloy before casting? Or do the alloys in the aluminum stay suspended on their own?


Yes, you do have to flux the melt, otherwise you get lots of porosity.


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## DavidR8

Not that I expect to start casting any time soon, but what is a good source of material?


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## r3292c

Heatsinks are not a good source - they're extruded. The better source is what had been casted already.
To get some material I went to auto service shop, and asked people there if they could share some scrap aluminum. And they gave me a cast aluminum car wheel. You can see pieces of this wheel in the video above.


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## Shootymacshootface

So, car wheels, water pumps front covers, engine mounts, engine brackets and the like?


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## benmychree

Shootymacshootface said:


> So, car wheels, water pumps front covers, engine mounts, engine brackets and the like?


Likely front covers, water pumps, etc are permanent mold castings, not good.  Cylinder heads, on the other hand may be a good source, at one time I cut up a number of Jaguar heads, good heavy sand castings.


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## rwm

Also, many car wheels are forged so they are not ideal. That alloy is similar to extrusion. Cast car wheels would be good.
Robert


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## savarin

I was impressed there was no sign of heat shrinking in the centre of the cast can.
Very good.


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## OTmachine

This is a GOOD book:


			Casting Aluminum book by C.W. Ammen


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## Mikelkie

I do a lot of castings in aluminium, best source is automotive cylinder heads,gearbox casings etc
machines beautifully, but never pistons or alloy wheels or extrusions


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## frugalguido

Can  you expand on the propane burner in your YouTube video?


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## r3292c

I bought the propane torch in this store 3 years ago
https://foundry101.com/shop/


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## Samsquanch

Awesome to see other folks interested in pouring metal!  I have a gas-fired furnace and a smaller electric one, use both often for brass and nickel silver casting.   Use either natural sand or investment casting methods.   I love the utility and simplicity of the home built furnace.


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## gr8legs

Randomly surfing on YouTube I came across this roadside aluminum foundry - 1-man operation making cookpots and lids.

Fascinating - especially seeing how he formed the handle for the lid with a piece of wire.


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## rwm

Those are real skilled craftsman. Their sand is actually better than mine! But I don't usually hold down my cope with my bare foot!
I would buy one from him if I could.
Robert


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## savarin

way finer than mine as well, liquid metal and bare feet, ouch, and in the rain.


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## r3292c

Here is a video about new casting I recently had.
In general, the part looks OK, but porosity on the machined surfaces is quite high. Any idea how to reduce porosity? Aluminum was pre-casted to "muffin" ingots, borax was used for degassing, casting temperature was 680C = 1256F. Regular green sand (silica sand plus bentonite clay) was used.
Any comments or suggestions are very welcome. I'm just learning things.


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## savarin

My last cast was one of my most solid, ie no porosity visible.
I used my muffin tin ingots but barely let them melt before pouring.
check out post 210 for pics








						The Giant Binocular
					

Sav, have you looked at the various wetsuit repair kits available, might find something useful at a SCUBA shop. Must be a few in your area of the world. John.  Yes, they are for sticking neoprene to neoprene. Works well for that but doesnt stick to the glass or aluminium. I will experiment today...




					www.hobby-machinist.com
				



I'm also wondering if too much gas, ie too rich a flame adds to porosity, still testing this though.


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## ericc

How much porosity are you getting?  Does it undermine the intended use of the casting?  It was hard to tell in the video, since the angle plate looked good.


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## rwm

Gas porosity in Al is related to solution of hydrogen gas. It comes out of solution as the metal solidifies forming bubbles. The melt is always exposed to hydrogen in a combustion furnace. Even water can break down and be absorbed as hydrogen.
Borax is a flux, not to degas. In fact it may have water in it and contribute to porosity. I would not use any flux unless you have dirty metal or some known issue that requires it. Melting your aluminum into ingots first is also a bad idea. Every time you melt the metal you pick up more porosity. The best way to prevent porosity is to use clean metal, melt it quickly and pour as soon as possible. The melt will be absorbing hydrogen the whole time it is liquid. Degassing is possible but very cumbersome in a home foundry.
I am convinced that running a furnace lean (oxidizing environment) is helpful but others have argued I was wrong on this. Take that with a grain of salt.
I also think electric furnaces are better is this regard since they do not produce hydrogen.  You can even inert them with Ag if you wish.
Not trying to sound critical. I hope that helps.
Robert


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## r3292c

Hello Robert, thanks for you reply
Yes, I understand the porosity (gas porosity) might come from Hydrogen, out of the water: Al + H2O = Al2O3 + H2
H2O may come from flux, or from baking soda (some people use). As well as from propane burning, even from green sand (we add water into it). I keep my borax in a zip lock bag to limit amount of water in it. Added to crucible with melted aluminum, borax creates lots of bubbles. I plunge borax to the bottom of crucible, thinking it acts like degassing agent, bubbling through aluminum. Maybe my understanding isn't correct.
About re-melting aluminum. I'm not an expert, but I heard re-melting helps reducing porosity. When the aluminum solidifies, it pushes hydrogen out. So, once aluminum solidifies, the amount of hydrogen in it is reduced by an order - see screenshot. This means, even porous ingot has much less hydrogen dissolved than shiny melted metal.
I agree with you that electric furnaces are better, clean metal should be used, melt it quickly and pour as soon as possible.


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## rwm

I don't think Borax is appropriate to degas. Some people use chlorine pool tablets which scavenge the hydrogen. Rotary degassing with inert gas is used in industry. 
I disagree about remelting. I think it makes porosity worse. You should consider becoming a member at Alloy Avenue. If you search over there for porosity you will find some detailed discussions. Those discussions with experienced casters are the basis for my advice. Another good site is http://forums.thehomefoundry.org/index.php
Robert


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## r3292c

Thank you for the link!


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## deakin

my cabinet maker friend got into alum casting among other things and says he uses beer cans because he as access to a lot. somewhere i have a casting stamped with the weight and amount of beer cans.


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## john.k

Cans are worth a 10c refund here .....never see one ,not even the stainless ones....When I was a kid ,a guy down the road used old motor bike alloy to make pulleys ...Indians,Harleys ,Hendersons ...all went to make pulleys.


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## brino

john.k said:


> Cans are worth a 10c refund here .....never see one ,not even the stainless ones



The beer stores here have stopped taking back bottles and cans for deposit (due to covid-19).
They are starting to pile up.

If the aluminum to other(paint, interior coating) ratio was better, I would consider melting them down.

I might start throwing them in the blue recycling bin........

-brino


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## speedybtx

Source from Sand castings, eh ?   So old Maico Dirtbike engines.   NOOOOOO ! save them!


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## Diecutter

Large aluminum castings such as transmission housings can be heated up  (in a log fire, with a weed burner, etc.) and then easily broken into  crucible sized pieces with a hammer.  The temperature needed is way less than melting temperature.  I have also had luck in sawing  aluminum auto cylinder heads into pot sized sections on my 4x6 bandsaw, then simply fishing out the valve seats, guides, etc. when the sections melted.


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## r3292c

Here is one more experiment. I tried to compare green sand to water glass sand on the same draft.
My water glass sand was more sticky, so I had much less loose sand with it. The green sand was made of finer sand, it provides smoother surface on non-machined areas. This is also expected. But what wasn't really expected that porosity is much better with water glass sand. Do you think that the water used in the green sand may cause more porosity? All other conditions were the same - the same batch aluminum, the same foundry, the same Borax used, about the same casting temperature...
By the way, when I pour aluminum to a tin can, the porosity is also much better than with using green sand.


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## Cheeseking

If we need good finish we use a zirconium (zircon) sand. Its a pain tho making a separate setup apart from the silica/air set line.


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## Nutfarmer

A little trivia on aluminum cans. The lid ( top of the can ) is 5182 allloy. The inside of soda cans are coated , while beer cans are not. Beer is not as corrosive as soda.


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## Larry$

I do a little AL casting. My favorite video site is Olfoundryman. I fire a home made furnace on propane.  Use a clay/graphite crucible.  I bought a commercial degassing product. Helps but not absolute. I just buy fine sand at Home Depot & bags of Bentonite at the local concrete company. I use sodium silicate & sand for cores. I bought a cylinder of CO2  to set the sodium silicate. Have never tried baking an oil, sand, clay core. Depending on what I'm making I'll use about any alloy. But for best result with scrap I like old automotive castings. I think pistons usually have 10+% silicone. Things I've made with them came out OK.  Extrusions are less than ideal but readily available and OK for many things. I get 6061 cut offs from a machine shop. Melting cans is a waste of fuel.  I've had some zinc get mixed in and like the resultant harder(?) less gummy machining characteristics. Controlling shrinkage seems to be mostly in the design of the mold, use of gates and riser-size/ connection. limiting oxide inclusion is done with  pouring so the oxides are kept floating and not entering the mold. I've been using a pouring well and a quite small tapered sprue that has been better than my previous attempts at just using a hole left by a piece of 3/4" piece of copper tube.


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## brino

Larry$ said:


> I do a little AL casting.



Indeed. Lots of details and hints packed into that post.
Thanks!
-brino


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## r3292c

Casting of a hand


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## Tim Keith

Is a direct melting furnace a good choice for casting 50 pounds of aluminum ?

On Monday I'm visiting a foundry to observe them casting bronze!


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## savarin

Tim Keith said:


> Is a direct melting furnace a good choice for casting 50 pounds of aluminum ?
> 
> On Monday I'm visiting a foundry to observe them casting bronze!


Will they let you take photos


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## Tim Keith

I'll see if I can take photos.


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## Tim Keith

Tim Keith said:


> I'll see if I can take photos.


The furnace was below ground level.  It was fueled by propane.  Not much to see.  They were melting brass and wax for investment casting


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## vtcnc

benmychree said:


> Likely front covers, water pumps, etc are permanent mold castings, not good. Cylinder heads, on the other hand may be a good source, at one time I cut up a number of Jaguar heads, good heavy sand castings.



@benmychree - Are die cast aluminum castings considered “permanent mold” castings?


Sent from my iPhone using Tapatalk


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## r3292c

Making 3-way pulley


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## r3292c

Another aluminum casting adventure


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## benmychree

vtcnc said:


> @benmychree - Are die cast aluminum castings considered “permanent mold” castings?
> 
> 
> Sent from my iPhone using Tapatalk


Yes, they are considered permanent mold castings; the alloy contains iron to prevent sticking of the aluminum to the molds, and causes castings made from such scrap to shrink to a higher extent and cause puckers in castings of uneven section.  Pistons are poor scrap for making sand castings, and melting in an iron pot exascerbates the situation even more.


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## Larry$

For me, its not about using the perfect or correct alloy. Its about getting a casting that works for the intended use. I've never made a perfect casting! I try to improve my results but less than perfect is still fine. Its the doing and learning that turns my crank. I've never made something that is maxed out strength wise. If I feel I'm pushing it, I'll resort to the PDS system (Plenty Damn Strong.) Aluminum has a high rate of shrinkage no matter what the alloy. Design your patterns to compensate. Provide feed reservoirs for thick areas or better don't make thick areas. Use chill plates to control rates of solidifying so those areas can pull molten material from the feed areas as they shrink. Plan your sprue, gates, & well to minimize turbulence and prevent dross from entering the mold. You can buy chemicals to put on top of the finished pour that burn to keep it hot so metal continues to flow. Absolutely none of these are my ideas, but they make sense once observed in practice. All require judgement and practice. Credit Olfoundryman videos. Have fun, Failure is a system for learning. Its cheaper to learn from other's mistakes.


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