Protect the bottom of your foundry

[Florida Man Metals]

It is important to protect your foundry from metal spills and flux. Putting a 3/8 inch or so layer on the bottom makes for easier clean up of any spilt materials and prolongs the life of your foundry.

I used to use a layer of fine silica on top of my fire brick to protect them from spills. I recently switched to bone ash. It is much finer than silica and works better. More of a powder than a grain consistency.

Technically the books calls for calcined bone ash. I used bone meal from Lowe's garden department. Initially it turned black upon the first firing, then turned into the desired white ash.

[Frosty]

When you say foundry it sounds like you're talking about the melter rather than the shop. No?

Frosty The Lucky.

[Florida Man Metals]

Yes, the bottom of the furnace/melter. I hope your shop doesn't get hot enought to burn bone to ash. You would definitely need some crazy PPE.

[Florida Man Metals]

You can also place it in the area where you are casting as well instead of a sand box. I guess this would technically be considered the foundry?

[Frosty]

I believe the foundry is the facility rather than a single piece of equipment though I'll be happy to learn differently. English is such a slippery thing you just never know for sure. 

One of our club members is a professional bronze caster and pours over a sand box or outdoors on dry dirt. He conducts the yearly iron pour at Art on Fire event and that's all on the ground. Until a couple years ago I demoed blacksmithing about 50' from the cupola and iron pour. 

Frosty The Lucky.

[Florida Man Metals]

Since we're on the subject of proper terminology the only melter I have is a wax melter. Have you ever seen a tilt melter or assay melter? They are referred to as furnaces. 

[Scott NC]

  I have always called them melters.  Don't forget, a drain hole to protect the bottom of your "unit" for those inevitable spills....

[Frosty]

A melter is a type of furnace though probably not a wax melter but a tar pot on the roof with the roofers is fired by propane or fuel oil would be a furnace. We heat our house with an fired oil boiler, the firebox section is called the furnace. Furnaces burn things whether as the process or the end result. 

Frosty The Lucky.

[Phil K.]

I call mine a Foundry Furnace. My small one I turn on the side and use it as a forge. In steel mills there are Electric Arc Furnaces, Basic Oxygen Furnaces, and reheat Furnaces.

[Nobody Special]

I would tend to think it would depend on the design a bit. Been a long time since I had a crucible fail inside, and since I switched to using charcoal the bottom is usually covered in regular ash. My furnace has a drain hole that I place a ceramic plinth over to set the crucible on. It's got two channels built into the bottom that run down to the hole so if something happens to the crucible it will go out the hole, plinth or not. Last time I had a problem was a long time ago, but the aluminum just ran out the bottom onto the sand.

I use a variation on the backyard metalcasting refractory recipe in my furnace, in a metal shell, over reinforcing bolts and wire, with fibreglass insulation up against the shell. Portland cement, sand, perlite, and fireclay and secret ingredient X. It's maybe not the way I would go now, but it keeps working, so why not? Worst complaint is that it's heavy.

Built my first forge out of the stuff, wouldn't recommend it for that; it chipped out a bit and widened the firepot. But I only ever had a problem using it in a furnace once; when I was ramming the refractory I left an air pocket in one wall and it blew a hole out on the inside. Patched it and it's been fine since - the one I use now. I would have thought the portland cement would fail and start to slag but it just keeps going without any apparent damage. If I was on firebrick though...

[Shiznistopher]

Hello all,

I have been a member here for quite a while, but I've not had the opportunity or ability to post anything that hasn't already been said, until I saw this post a few days back.. 

So maybe ya'll could give me some insight as to how to remove all this molten copper from the bottom of my furnace..

A bit of history of my furnace for those that are interested, I saw youtube the TKOR video where he built a furnace with everyday items and had some inspiration, shortly after I watched The Backyard Scientist on YT as well, and thought to myself that if THESE knuckleheads can do this, then I can too!

I started down a rabbit hole that would have quite a few failures and very little success until i stumbled across this site, and it has been a veritable treasure trove of information and experience, like I said previously, I've long been a member, just lurked and never posted until now!

So (this) iteration was built with a 12Qt feed pail, with Rutland castable refractory cement with light fire brick rated for 2800-3k inside the main structure with the rutland cement poured around them, as well as two 3/4" holes offset on either side of the unit, I'd intended to make this a dual burner setup from the get-go but sadly my air supply delivery mechanism wasnt quite up to the task, so i dropped back to one hole where the burner is inserted.

The burner it self, is 1" pipe that steps down to  3/4" with two propane connections, one static and the other able to be turned on or off depending on the stage of burn i am at. I usually keep it off until the furnace has heated up, and then Line to Load is accomplished with both tanks at 40# until the burn is complete.

The shiny copper key chain ornament, is the result of a successfull LOST PLA cast about 4 months ago, actually the day before the my 6" Sch 160 pipe with a cap welded to the bottom, failed and leaked molten copper to the bottom of my furnace..

So thats a lot of words to get to this point, but I am plum out of ideas to get the furnace floor cleared aside from destroying it and rebuilding it.. but that stuff aint cheap so id rather avoid that if at all possible.

AAAAAAAANYWAY, Thanks for giving this a read!
I appreciate any ideas or such you have to offer me, Thanks!

[Frosty]

Glad you delurked Shiznistopher, welcome to the active branches of the nut tree. 

I don't know if the spilled copper can be salvaged and maintain the melter's liner. Probably busting it up and hopefully recovering the copper is your best bet. Were it mine my first try would be turning the melter upside down and lighting it. Maybe the copper will melt and drip out. 

I think your liner is shot at any rate. 

Next time you build a melter slope the floor to a drain so a failed crucible can drain into a pan of DRY gravel to be recovered later. When molten copper cools it shrinks and if it's stuck to the refractory in the melter it WILL break it up. 

Next melt just buy a roper crucible, the iron in a steel pipe is soluble in molten copper, a welded steel crucible WILL fail casting copper.

The way you constructed your melter is also part of the problem though I might of misunderstood it's construction. You made the inner liner from light insulating fire brick (IFB) and poured Rutland refractory cement around it. Do I have that right?

Next build, buy a sack of "Kastolite-30 li." It's an insulating, 3,000f, water setting, high alumina, castable refractory. If you want a better insulated melter wrap the outside with two layers of 1" 8oz Kaowool, or equivalent brand, ceramic wool, refractory blanket. Look for one that is soluble in the human body! And above all wear breathing protection when handling any kind of ceramic blanket! Wrap the outside of the insulated melter, make it in an UNGALVENIZED bucket, section of a 15gal. grease barrel like you see in a service station, section of stove pipe, etc. Whatever the shell is contain the refractory blanket, the stuff is fragile and prolonged exposure can cause serious lung issues.

Check out the many proven burner designs in the "propane burner" section of Iforge. Years ago a late good friend of mine mistook my description of a propane burner I'd built. We were driving doing a little sight seeing while he was visiting Alaska. He got home some time later and sent me a photo of his interpretation of the burner I'd described. I ALMOST sent him a rely telling him he'd gotten it wrong, that won't work!

I'd described what people call a "sidearm" burner. He'd rotated the T fitting and built a T burner by happy mistake. Fortunately for me I sat there looking at the flame and realized it was beautiful and the burner was WAY more simple than the sidearms I'd built. 

Anyway, Robert was melting up to 20lbs of cast iron with one, 1" T burner. His melters were high quality builds, he was an accomplished caster and wanted to use propane rather than a coke cupola melter.

Sorry, I get carried away but you REALLY need to lose that . . . burner. I don't have a clue why you have two fuel lines staggered like that and frankly don't want to. You copied it from a Youtube video posted by a couple knuckleheads, did you say?

If you want to build a T burner, read my build plans pinned in the propane burner section. Or if you prefer build a proper gun (blown) burner but use proven plans. 

I HIGHLY suggest you subscribe to one of the casting forums and talk to folks who do this frequently and safely. 

One 10lb crucible of 2,200f molten copper spilled on a concrete floor WILL cause the concrete to spall explosively with the same energy as IIRC 2-3 sticks of 40% dynamite.

Please PLEASE join a casting forum and talk to the experts. I can help build a reasonably robust melter and burner but I am NOT a caster. One small mistake can maim or kill you, burn down the house, maybe a forest, etc. 

Frosty The Lucky.

[Shiznistopher]

HEY!

Thanks for the info about the build, I appreciate it!

As for the burner, no its been evolving since i started this process about 2 years ago. It does the trick, for now anyway, and I wanted to learn about how the systems work together to function as a whole, so instead of buying one, i built it. Mostly black steel pipe with a few fittings for fuel and valves, but it works! 

My cousin who built his own furnace/forge 20 years ago helped me along with the design of the burner, not YT  , the two fuel lines are because of the two propane tanks it takes to get it hot enough to melt aluminum or copper, and because my brother shot down the idea of letting me tie into the natural gas line at our house, he's a buzz kill lol

JK he has a lot of sense but that's the reasoning behind it.

I will check out your plans for the burner,  i took inspiration from lots of different posts here and across the internet, i just didn't want to have a carbon copy of what someone made, wanted to make it my own, yanno?
About the walls of the furnace, it is just refractory cement from Rutland, molded into a cylindrical shape to accommodate the clay/graphite crucible i have since the steel one failed and I don't know enough about how to weld to restore it to its previous functionality.

And yes the furnace construction itself was made of fire brick with rutland refrac  poured around it.

Thanks for the tips!

[Frosty]

Tying into nat gas for a shop forge, melter, etc. is EXPENSIVE! Ask the gas company how much it would cost to get 150,000 but/hr. hook up. It isn't just a meter and some plumbing.

Rutland has been around a long long time and I don't think they've improved it. Heck, I don't even know if it is a refractory or a refractory CEMENT. They are two related but very different things. Cement, mortar, etc. is for sticking fire brick, panels, etc. together NOT to survive well in direct flame contact. Refractory is formulated to be a flame face and survive incandescent yellow temps.

Kastolite has hollow silica spherules  as part of the fine aggregate which makes it physically lighter but when the refractory reaches about 1,000f the silica melts and is absorbed into the refractory leaving a small evacuated void in it's place. It's really a brilliant component. 

KOL (KastO Lite) is not only lighter weight all the evacuated voids slow energy (heat) transfer through the walls. Being high alumina it all but laughs at yellow hot borax which dissolves common 3,000f heavy fire brick sort of like hot water on a sugar cube.

There are more things you can do to increase your melter's effectiveness, things we often do to our forge liners but it's not really worth using kiln washes and zirconia washes. Melter liners take too much HIGH TEMPERATURE physical abuse from lift tongs and the incredibly harsh conditions in that little gap between liner and crucible. 

Even in you line it with the toughest effective refractory it will still degrade and need to be rebuilt. Melter and forge liners are wear items. I'm no chemist but what I've read says burning propane has VERY ACTIVE chemistry especially at high temperatures. 

Ever consider smithing? It's hot, dirty, dangerous but you HAVE TO play with fire and hit things with hammers. Seriously, what's better than that? Wearing clothes of course. 

Frosty The Lucky.