Thread 2936810

Hello /DIY/, I'm looking to build a higher capacity foundry as my current one is too small for the projects I'm planning, it's going to be powered by a dual fuel Propane/drip oil burner that I'm going to build once the foundry is ready.

the vessel I plan on using is an old 30 gallon water well tank like picrel (mine is an old one that has steel legs) roughly 24 inches wide and 36 tall, I'm going to weld flat plates in the top and bottom domes so the actual inside dimension will be around 24x24.

the hottest I plan on going is around 2300F to melt copper.

My question is what is the most durable lining readily available? it seems that most castable refractory linings are great insulating wise but aren't very durable and need to be relined often, not to mention them costing a shitload of money, I was thinking maybe fire and or refractory bricks as they seem to be very durable, but I have no clue where to source enough of them to line the vessel for a reasonable price.

any input would help, I'm not afraid to spend maybe a couple hundred bucks to build this thing but I'm not going to spend a shitload of money on it.

>>2936810 (OP)
Starlite

>>2936810 (OP)
don't do refractory cement, it'll crack and crumble away

have you tried kaowool? I don't think it's that expensive and it seems easy enough to work with, just measure, trim, and line.

>>2936810 (OP)
Standard practice for the higher end setups I've seen involve a layer, or two, of ceramic wool, with an appropriate ridgidizer applied. Next up is applying a thin coat of refractory cement (some people use chicken wire to help keep things more sturdy, given how flimsy the wool can be), cure appropriately then apply another coat, cure, and patch cracks.
Plan to include some sort of removable fire brick plinth - easier to replace one brick in case of a spill or cracked crucible.
People use fireplace or furnace seals around the edges of the lid, occasionally.
Some people do advanced things, like create custom 3d printed molds for modular, easily replaced burner grates that are cast out of refractory cement.

You *could* try and dig up the necessary recipes and raw ingredients needed to make your own refractory, but it would be a project unto itself, better to just buy some well rated crap off of Amazon.

You're likely looking at roughly $200-$300 in materials total.
I hope you have your casting sand or the ability to make wax positives for ceramic slurry shell negatives.

>>2937031
This is what I was thinking of doing, this method combines the properties of all the building materials to get a very efficient furnace, not to mention with the insulation acting as a filler I can expand the foundry in the future if needed.

I've been looking into lost PLA casting which will allow me to make larger more precise molds than my previous ones.

also, I finally located a refractory materials supplier near me, the prices are pretty much the same as online but I don't have to pay shipping and they also have commercial grade stuff that is supposedly much better than the stuff most consumers have access to.

Now all I have to do is make an actual design and budget everything out.

Thanks for the input.

>>2936999
Refractory cement is a sacrificial layer that protects the insulation, shitard, you're supposed to reapply it when it wears out.

>>2937227
This. Industry operates no different. Line things with refactory brick and when worn replace. It's probably tiresome but so far nothing was found that lasts.
I doubt OP is casting enough low smelting metals to worry about the cost of reappllying cement.

>>2936810 (OP)
Clay soil. Built a 50 gal furnace for aluminium, worked good

>>2936810 (OP)
On something like that, maybe an inch of cancer-wool and use a form to pour in about an inch of refractory mixed in with something like fibreglass to hold it together
Ultimately, its all a wear item and just needs due-processing- week to dry, couple of low-fire heatings and it'll hang in there for a while. You can also use mud like ->>2938465 suggests, as long as it doesn't have rocks or big chunks of organic material in there it works well (termite mounds or silt from rivers works great) and probably about every half-dozen firings it needs a bit of slop in the cracks and good to go again.
They can take a month or more to dry though depending on were you are and the seasons if its not warm

>>2936810 (OP)
Listen anon, I got you.
Refractory cement from Menards will not cut it. People who want to melt just tin and aluminum can use a 1:4 refractory cement/ pearlite mix by volume dry and mix as dry as you can.
Get real "castable refractory" look for something that brags about its alumina percentage. It's be hard to find in less than 50 lb bags at places that specialize in weird building materials and refractory. I can't remember what mine was called.. something like Missou I dont know. The important part is it's high alumina castable refractory. At least 40%. Mix this in the same 1:4 dry volume ratio as before and don't make it too wet. Mix it super well and ram 3 inches thick for a 30 gal around a removable mold. I used I giant pickle jar covered in foil but mine is a smaller party helium tank. Let set for a few days, remove mold, let set for a few days, cover and fire on low for 1-3 min, let cool, 5-10, let cool, 20, cool, slather on a decent 1/8" of pure castable refractory on all inner surfaces, because pearlite will flux at just below copper temps.
I don't know how or why this works so well but I've done cast iron in mine twice and copper probably 30 times, lots of aluminum and bronze. It's holding up great and is so much more pleasant to work with than kaowool, while still being quite insulating.

>>2939893
I meant to say it also matters what fuel you'll be using. I just have a 3/4 t burner with a big mug tip and propane. If you use waste oil in sure this will not hold up.