Check out www.backyardmetalcasting.com
I have a pretty large collection of abandoned Aluminum 6061-T6 extrusions lying around my office. Is there anything I can or should do to these extrusions that would make them suitable for some experimental backyard hobby casting? How small a bits should I cut them up into before melting? I want to start toying with this whole home foundry thing a little, with the goal of eventually making some limited production (likely limited to 1) parts for my project car.
I blew the dust off my college materials science book *COUGH, COUGH* and scanned through the chart on aluminum alloys and their compositions- looks like the alloys commonly used in casting have silicon in them? Why, and do I need it, and how would I get it in the alloy if I do?
Silicone is put into aluminum for several reasons. As a hobby caster you have no worries about having to add anything to the aluminum as it is already an alloy. Unless your making zinc za12 or something like this you can basically melt down the aluminum, with your home made fournace and then cast using what ever method you would like to try. For sand casting oil based petrobond sand is likely the best. I have played with green sand and its not nearly as good as petrobond. What i really enjoy using at the moment is lost foam casting. As it is the easiest and most succesful i have used.
If your thinking of building a fournace. Do not use charcoal. Go right from the start with propane.
I used common 1 inch thick fire bricks, i used six to make the center of my fournace. I then cut some common fournace duct tin and made a casing. About 20 inches. Then using common refractory " you can get this anywere commercial tile is sold" mixed with perlite "home depot sells this in huge bags for 20 bucks" until it is a kinda of crumbly mix. Then litely tamp into the casing around the bricks in the center. I held the bricks in the octagon kinda shape with wire. I also cut them at an angle with a tile saw so they fit together tighter, this was not needed as the one i made for a friend worked with out cutting the tiles. Using the same size casing cut to about 5 inches i made the bottom and top by putting bricks down flat on plastic and then put the casing around them. I made the hole for the top before i packed it and then used a pop can and packed around it. Packed it the same as the mix i made for the rest and let it all cure for a week. I built the burner from Ron Reils designs on his web page. I made the crucible out of 5 inch pipe and all the tools i use for pouring were made with metal that i bent using the burner.
I have had my fournace for 2 years and have cast alot of things from lead, zinc alloys and every kind of aluminum out there. I recommond lining the fournace with the fire bricks as this has greatly increased the durability of my fournace. I have had the fournace upto 1300 degrees celsius. I was melting bronze. I recommend that you look at the Dave and Vince Gingery books at lindsay publishing. I have Vince's book on crucibles and aside from coming up with my own mixture for the crucibles it helped alot.
You might want to check out these sites.
Ron Riels web page
the yahoo groups for gingery, casting hobby
Have a good one.
That site you suggested and it's links was a wealth of information. I almost want to give casting aluminum a try. Too bad last year I threw away a perfectly good used fuel oil burner assembly out of an old fuel oil furnace. I think that would have been a good start to get things going. Since my son works at Jiffy Lube, I can get all the used oil I will ever need, but I like the idea of using fry oil better.
If it's not nailed down, it's mine.
If I can pry it loose, it's not nailed down.
I would really go with propane to start with as a fuel, for a start you have enough to worry about with a hot furnace ( very heavy - mine is small and takes about a day to cool after runing for a couple of hours ). Also until you get the hang of using oil you will probably offend any neighbors you have ( I know I did ).
This is not meant to put you off metal casting or cause offence, BUT
a reality check, before you have 2 litres of runny aluminium at 700 deg c
in you hands.
If you are really serious about this first ask yourself some questions.
a) How near is the hospital or nearest burns unit?
Could you get there with one leg?
b) The safety gear you need is not cheap but you need it, see point (a).
Head Sheild & Face Shield
Gauntlets ( Asbestos - V.Dangerous in itself )
c) Somewhere outside where there is nothing or little to catch fire.
d) Someone to watch your back all the time while your working.
After all that metal casting is VERY rewarding, a lot more complex and involved than first impressions. I can't put into words the feeling when you take your first casting out of the sand ( after a suitable delay ).
Pattern making takes quite a bit of patience, yet more skills to be acquired unless you know a pattern maker or someone with a cnc.
If you would like, I'll photograph my setup for you. There are some pictures of castings that I made for my CNC project in my user gallery.
Thanks guys- BTW- got my furnace up and running this weekend and melted some pieces of 6061 just to make some blobs (I think the technical term is ignots, but they look like blobs to me) to test out the furnace and crucible. I went with the basic pearlite / furnace cement receipe lining the inside of a 5-gallon kerosene can with the top cut off. I ran a 1/2" stainless tube (which was lying around, leftover from an old project) inside which when starting I used to deliver propane to light the charcoal (I hadn't read all the praises of propane alone at that point). I was about out of propane and thought that the propane delivered wasn't going to be adequate to do the job anyway- after all it was only a little blue flame down there... maybe I was wrong.
I ended up putting about a dozen charcoal brickettes in there and use the pipe to deliver air from a compressor which made a slurry of aluminum in my paintcan crucible in no time flat. VERY hot fire- if I hadn't been paying attention, I might have melted my steel paint can, as it was glowing bright red and just a little warped... but it held together.
Besides the PITA of the removal of ash, what is the downside to charcoal? it sure seems capable of producing more than enough heat, and the wife seems to think I'm less likely to blow myself up with it!
realy nice projects and some realy good casting, but please do not use iron crucibles, it is so dangerious.
I have posted planes and loads of instructions for building furnaces pluse a hole load more on my site
Just loved the series on lost foam casting.
Excellent site! Your presentation earned yourself a place among my bookmarks.
It is nice to see you like car wheels as a source of aluminum as I have unlimited (for my needs) access to those. I haven't tried them yet as I still have not used up my Ferguson gearcases
I always use degassing briquets. Nowadays they are a lot less harmful than the old Hexachlorethane. I also use dry sand with binder. You should try that. You can make the molds days/weeks before melting which is perfect for hobby use. Just make sure they don't collect moisture.
would like to know more about the dry sand casting, i have a feel that it is sodiumsilicate and co2???
Sodium silicate mixed into the sand and co2 to set the silicate is often used. The sand sets rock hard and it's important to remember that the sodium silicate has a shelf life and will set in the bottle over time. Co2 can be purchased at supermarkets that stock home made soda kits.
Here's a very intersting link for anyone interested in casting http://www.dmdaustralia.com.au/block.html
Looks like a lot of experience here, maybe I could get some tips. I have done some casting of Aluminum but my finished casting seems to have a lot of porosity, probably impurities, wrong temperature when pouring, mold problems? This is not good since I am trying to make some underwater diving housing for cameras & lights. My first attempt came out more like a strainer. Any tips on temperatures? or other thoughts that will help, Thanks Arnie