How many Coats of Satanite to High Temperature Wool

I have basically completed construction of my very low mass iron-melting furnace and have test fired it. Here is a brief "teaser" on its function with a thread detailing its construction to be posted within the next week.



The furnace is made from a 30 gallon barrel and lined with 2" of 2600 deg ceramic wool. So far I have put two coats on and the buildup is probably an 1/8th inch or less. I'd like a bit more to improve resistance to incidental damage from bumps and thumps. But I have heard to much will flake off. So what is just right?

I can say this furnace comes up to white hot in under 5 minutes---much much faster than my cast hard-face prior furnace (30 mins?) using the same burner tube setup. The furnace itself not counting frame probably weighs something like 50 pounds.

Denis

 

That is a nice looking furnace.
I would expect that it would come up to temperature very fast, since it basically has no appreciable mass to it.

It also sounds more quiet than the other one.
Am I imagining that is it really running more quiet without so much reverb?

I would suspect that the ceramic wool may have to be rated for 3,000 F, but I have no experience with coated refractory, so I am just speculating.

Let us know how it melts iron.
I think you are going to save a lot of time and fuel.

.

 

PatJ,

It could be a little bit quieter since the chamber sizes larger one would expect that that might reduce the vert reverberation frequency and perhaps the intensity. If you exaggerated this situation to making the chamber size as big as a bedroom you would expect no reverberation and a very quiet operation.

The amount of material actually being heated up in this furnace is indeed very small since it consists mainly of the Satanite lining of the chamber plus maybe a third or 1/2 of the underlying wool. That amount of material probably is only a five or 10 pounds so there isn’t much that has to heat up to come up to temperature.

I am Very anxious to try out the furnace actually melting iron. My hope is that it will, indeed, result in a much reduced melt times.

If all goes well, I will be in melting tomorrow. I’ve been spending the last three or four days drying out sand that unfortunately got wet due you do a storm that ran water under the barn door where I work and into the sand which ended up way too wet. I’ve been running two fans and stirring the sand two and three times a day to finally get the moisture content down to where I can mull it and mold it.

Denis

 

Denis,
Hightemp tools recommends a 1/4" layer. The thicker it is the more mass because it does create a hot face.
What I found, if you put that much on the lid, gravity pulls it loose from the wool over time. I only do two coats there.
I really like the stuff and it will be interesting to see the longevity when exposed to iron temps.

 

Thanks Fishbonz,

The lid is not subject to much injury from my clumsiness. The walls are another matter. Maybe I’ll compromis and put on another layer and call it good. Probably will be 3/16 or so.

Heat durability is the big question. Will see how that goes——hoping for the best.

Also thinking about a final coat of ITC 100.

Denis

 

Given mine is smaller and not intended for iron, but the first few coats I mixed up rather thin and vitrified before adding more substantial coats that were mixed a bit thicker. The thin coats are understandably rather fragile and I managed to damage them brushing on additional coats, but I'm somewhere around 3/16-1/4" thick currently and it seems much more rigid. Not sure it helps, but that's all I've got.

 

So you are putting on coats 1/16" thick?

Do you have to bake it and cool to room temp before the next coating? Or bake it and apply the next coat as soon as possible while still hot?

How well does it do on the underside of lids over time does it break off?

 

I put Satanite around the flue opening and under the arch on mine and it is holding up extremely well. Over 150 thermal cycles with no real deterioration.

 

Denis: It will be interesting to see whether you melt the ceramic fiber behind the Satanite. I don't think it will melt until above 3,400F.

 

First, you should not be asking ME what I do with Satanite as I am at my first Satanite rodeo. ;-) (I have watched quite a few YouTubes on forge making with wool and Satanite and what I did is an amalgamation of the info derived.) But, I mixed it up pretty thin---like sour cream or a little thinner. Then brushed it on with a chip brush. I could see it go from a medium grey color just after application to gradually turning a light grey when dry a few hours later. Then let it dry for a day or so assisted by a fan in my 60 deg shop and then reapplied. That seemed to work pretty well, but I would love to hear from those that know how to do it better.

Yesterday I did vitrify the first two layers by running my furnace white hot for 20 mins a couple times. I think I will go back and put on one more coat on the side walls but not the lid.

I would think the furnace reached its "terminal" temp in that amount of time as it seemed to go from cold to white hot in 5 mins and then just stayed there. Afterward I looked carefully for signs of melting or delamination of the wool, but found none so far. That is, of course, a far cry from blasting away for an hour or two as I will need to do with my next melts. I do have one mold ready to go tomorrow if weather allows and expect to ram up another in the AM. We'll see what happens.

Incidentally, the plinth and and tuyere made of Kastolite 30 and brushed with Satanite seemed to tolerate the heat without batting an eye.

Denis

 

I have fired Satanite as soon as it was apparently dry, then recoated as soon as it was cool.

Did it feel solid after it cooled?

The blacksmith guys swear by the ITC-100. I have some and have used it but really can't tell if it did any good. The Satanite I have on my brick is very hard and takes a lot of tool strikes while hot with no apparent damage. It is over soft firebrick.

 

It felt rock-hard after it was fired. I have some over a couple of IFB's on the floor of the furnace. They were intended to provide a solid surface for the plinth. The rest of the base is insulated with an inch of ceramic board and then an inch of wool. the entire interior of the furnace is coated with Satanite and seems to be holding its own so far.

Thanks for the application info.

Denis

 

If I could buy a Si-C plinth of a usable size at a reasonable price, I would do so. I would think the main quality causing me to favor it would be that it would be extremely rugged and reliable. Its thermal conductivity would be a small plus. As it is, a very small percentage of the crucible surface is in contact with the plinth. I would guess (could calculate but too lazy) to be 10% or so is in contact with the plinth. That contact is not air tight and the plinth does heat quickly so the amount of efficiency gained from a SiC plinth might be a few percentage points.

I am attempting to use SiC grit between the plinth and crucible as you know. My first attempt yesterday was a failure. I selected 60-90 mesh SiC grit as it was readily available and I thought it would be coarse and dense enough to be undisturbed by flame gas turbulence. Well, that was quickly shown not to be the case as immediatley after firing up the furnace with plinth in place and the to "bowl" filled with SiC, I noticed a faint shower of sparkly material coming out of the chimney. Yup, SiC grit! Oh well. I just ordered a pound of 10 grit SiC. That better stay in place!

You are right that my use is either one or two melts and done for the day at the present time and likely for a long time. So, for me sustained heat for the long haul is not a plus. I need a dragster that goes from cold to melted as quickly as practical without burning up crucibles too rapidly and without sounding like a fighter jet with afterburners on. Well, I'd like the noise I suppose, but the neighbors won't.

Do you have any price/availability data on SiC plinths?

Photos of the plinth for those who may not have already seen them.


Denis

 

Thanks for the link to the SiC plinths. They are pricey, but not as bad as I had imagined. I think the castable is going to do the job, but if not durable, SiC would be a consideration.

Yah, I was looking forward to my first melt today too, let me tell you. But, the heart of my day was cut out by grandchild babysitting requests. Arrrgggh! (Love those grandkids, but tough to have a day cut up too) Oh well, tomorrow, I hope! I will do some more molding today and be ready for more casting tomorrow than I would have been able to do today. Hope to have three molds ready and maybe do two melts. Maybe.

Denis

 

My situation on plinth is different. Since my burner is tilted down toward the hearth my plinth gets red before the crucible and all my heat is bottom up. With the brick furnace second melts are fast. Making ingots of scrap the other day my little SS crucible was giving me a 5 lb pour every 11 minutes. Melting window frames so I was limited by time to melt long pieces and had to keep the heat down to avoid overheating the crucible. My plinth is dense castable but I'm going to take a hint from you and put Satanite on the next one. This one is about shot.

 

Well, I got to run my new furnace today. It did well but I managed to stick my plinth to the crucible, drop the plinth and break it. My coarseer grit SiC comes Saturday---I should have put some cardboard down but thought i could get by---wrong. Oh well, no big deal given that the furnace performed very well as soon as I got my burner tuned. No evidence of melting wool, no flaking of Satanite---those were my real concerns.

I will write more about the furnace in a dedicated thread probably this weekend.

However, tonight I will post pics of one of today's castings and it transformation from from not so pretty larva to a functional butterfly. This morning just 12 hours ago it was a bunch of cast iron scrap. Incidentally, I added just 3 oz of FeSi to the 30 pound melt (there was another casting) and this machines beautifully. I needed a step pulley for my wood turning lathe as the old one gave up on me..

 

I have turned flywheels that had rims that were about that thickness and size, and without ferrosilicon, and the rims were easy to machine, so for thicker parts, I have found ferro necessary at all.
It is the thinner parts where I get the extreme hardness without ferro.

Edit:
I was reading a foundry book today, and according to that book (from 1917), the wedge test or another type test is used (such as drilling), and ferrosilicon added if required.
If you add ferrosilicon to the melt when it is not required, you are solving a problem that you may not have.