Thread: Aluminium Grades
I think is down to method.
Just sticking a few lumps of alloy in an old pot, melting it and pouring into another old pot will get you anything, good bad or indifferent.
For a start iron is soluble in molten aluminium and the gasses cause bubbles.
You also need ge gassing tablets to throw in that cause all the dross, shit , crap and German routers to come to the top so it can be scooped off and thrown at next doors cat.
Material also plays a part just because you stuff one grade in it doesn't meant you get that grade out as it changes in the melt.
professional smelters melt a charge, run a test to see what's in it or more important what's missing and then lob in ear of bat, tongue of newt to make up.
Things like pistons when melted contain most of the original metal plus carbon from the burnt oil and deposits which doesn't help, clean alloy is hard to get in quantities.
One of the best grades is LM25 which is available in ingot form but rare to find as scrap items, when heat treated this is closed grained, machines nice and can even be bent slightly proving how ductile a casting can be.
Unfortunately to make good casting it then becomes another hobby at the expense of others.
.John S -
Found a possible answer -
I would bet that what you are looking at is a shrinkage cavity or the location of a trapped air bubble. The melting and pouring of metal isn't really a very scientific field. The solidification of that molten metal is. If the solidification isn't done at a very controlled rate, you will have cavities where the solidification left a void. Likewhise, especially with aluminum, if molten metal isn't properly degassed, you can leave pockets of air. If the product was then cut, it would appear as a pin hole on the surface of the piece.
Not my words but sounds plausible...
Manor Foundry in Ilkeston, upper Granby Street, bottom of Bath Street, side of Tesco's, look for the big green sand silo.
Goes runs and one off's, guy called John runs it, knows what he's about as well, never had a bad castingJohn S -
So is Al casting best left alone then for small quantities?
fancy doing a crash course in Al casting for idiots?
The one i was talking about was a foundry in Ashbourne!
Used to get castings from John at Manor foundry occasionally, is he still there! Bloody hell! Got to agree though, quality castings.
Cool, Pm me your address if you want so i can work out the trip. After all this studying thing I deserve a break.
Cast some Ali, few beers and then scarper quick...(Think I can fit that mill in my boot) :naughty:
05-06-2009 #29Only £1100 for a brand new one....I'd get the sq column version.
Only joking about the mill, my agricultrally engineered pillar drill will be much better
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