for something like aluminum you could go with a home recipe, even up to bronze temps.
you seen what happened to my furnace and the store bought refractory that was in the wall was 2700 degree insulating.
I'm not going to suggest one over the other, but me I would use commercial refractory because its available and in the long run is probably cheaper. the stuff that I used to redo the wall in my furnace runs about 40 dollars a bag here in OKC, now if your not going to ever entertain the though of melting iron use something with a lower rating like 2600 and use an insulating refractory instead of a high strength Castable that will get as hard as concrete. some even mix perlite and vermiculite in the High Strength stuff to turn it into a semi insulating but you almost have to have a cement mixer to do it, I recommend a mixer to mix any refractory, you get a lot better mix with less water.
How big are you planing your furnace, size is everything, you look at a tube that six inches in diameter and say that's awful big, then stick an A4 crucible in it and ask yourself how are you going to get it out because there is no room to slide tongs down between the wall and the pot. Also another question you have to be asking yourself is how much oversize do you want to go to take up expansion of skill's down the road. bigger projects call for bigger flask and crucibles and furnace.
I think I saw where you said your buddy or his father worked in a foundry, he should be able to answer all these questions and lots that I can't.
One Big thing you have to ask yourself is do you want to cast metal or reinvent the wheel. To me its a lot easier to go buy the right stuff, then it is to try and find stuff that will work to make my own, by this I mean I can buy two bags and in three days be putting heat in a furnace to dry it out. if I try to find and buy stuff that will make refractory no telling how much I may spend. Of course if aluminum is all I need to do to make some small parts to heck with the furnace grab an old 15 inch lowboy trailer brake drum, set it over a pipe with a hole in it lay a piece of steel on top to keep the charcoal out of the blast pipe and fill it up with raw/lump charcoal and stick a crucible in it, squirt a little diesel on the charcoal and steal the wife's hair dryer.
DA
you seen what happened to my furnace and the store bought refractory that was in the wall was 2700 degree insulating.
I'm not going to suggest one over the other, but me I would use commercial refractory because its available and in the long run is probably cheaper. the stuff that I used to redo the wall in my furnace runs about 40 dollars a bag here in OKC, now if your not going to ever entertain the though of melting iron use something with a lower rating like 2600 and use an insulating refractory instead of a high strength Castable that will get as hard as concrete. some even mix perlite and vermiculite in the High Strength stuff to turn it into a semi insulating but you almost have to have a cement mixer to do it, I recommend a mixer to mix any refractory, you get a lot better mix with less water.
How big are you planing your furnace, size is everything, you look at a tube that six inches in diameter and say that's awful big, then stick an A4 crucible in it and ask yourself how are you going to get it out because there is no room to slide tongs down between the wall and the pot. Also another question you have to be asking yourself is how much oversize do you want to go to take up expansion of skill's down the road. bigger projects call for bigger flask and crucibles and furnace.
I think I saw where you said your buddy or his father worked in a foundry, he should be able to answer all these questions and lots that I can't.
One Big thing you have to ask yourself is do you want to cast metal or reinvent the wheel. To me its a lot easier to go buy the right stuff, then it is to try and find stuff that will work to make my own, by this I mean I can buy two bags and in three days be putting heat in a furnace to dry it out. if I try to find and buy stuff that will make refractory no telling how much I may spend. Of course if aluminum is all I need to do to make some small parts to heck with the furnace grab an old 15 inch lowboy trailer brake drum, set it over a pipe with a hole in it lay a piece of steel on top to keep the charcoal out of the blast pipe and fill it up with raw/lump charcoal and stick a crucible in it, squirt a little diesel on the charcoal and steal the wife's hair dryer.
DA
dallen, proud to be a member of MetalworkingFun Forum since Apr 2012.
If life seems normal, your not going fast enough!
If life seems normal, your not going fast enough!