Author Topic: New lining for the iron furnace  (Read 4526 times)

Offline vtsteam

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New lining for the iron furnace
« on: January 12, 2022, 01:39:49 PM »
The old iron furnace has been through a fair number of changes -- originally intended as a charcoal burning sawed off cupola. That was an experiment which didn't pan out. The lining was fire brick set in fireclay grog mix. The firebricks were set on edge to the bore, which was a little over 7". The lining was 4" thick.

A few attempts were made with different configurations to get iron to flow in the cupola using charcoal. But I never got hot flowing iron. My feeling at the time was that it might have worked with coke - the density difference meant a lot lower fuel weight in the bore with charcoal. An attempt to change the tuyeres and furnace height didn't improve it enough to pour iron.

The furnace was then converted to an oil crucible furnace by adding a modified Kwiky burner and I was successful with iron in that configuration. The bore was still a little over 7" and that made it difficult to get tongs around even a number 6 crucible. It was do-able but not ideal. Also the furnace took about an hour and a half to two hours to melt a crucible of iron from cold start.

Since then, I haven't used the iron furnace -- I've mainly been casting aluminum, zamak, and occasional brass using my smaller and more convenient plaster-lined propane furnace. But last year I wanted to cast some engine parts in iron. The lining of the iron furnace had got wet and needed repair -- it was still viable, but the bore was actually smaller than the propane furnace, so I decided to tear out the old lining and try the Ironman's insulated type: ceramic blanket covered with a painted-on ceramic hot face compound. I could then increase the bore to about 10" and, I hoped, cut down substantially on melt time.

The hard part of lining with insulating blanket in the past was in trying to find a substitute for the Zircon hot face compound Ironman uses -- apparently only available in Australia. Afew years ago I had called a couple of manufacturers of similar compounds but they wouldn't sell to non-trade individuals. But since then ITC 100HT has been become openly available and is used here in the States by gas forge hobbyists. So I decided to try some.

The stuff is not cheap....$500+ a gallon. But it is sold in pint sizes at an affordable price on ebay. So a year ago I ordered that and some 2" Ceroblanket insulation for my furnace. I figured a pint would probably coat the furnace.

Last week, a year after I had ordered the materials, I installed and coated the new insulating lining, and today with temps of 14 degrees F by noon (not ideal :loco: ), I decided to bake the lining. That is supposed to be done below maximum heat for the first 6 hours. That's a lot of fuel! Instead of propane or oil (which would require the compressor and blower to be set up) I decided to do it the low tech way I did all my other linings; build a small kindling wood fire in the barrel, then let the charcoal embers heat soak the furnace for a few hours.

So, I loaded the barrel with some crumpled newspaper, and 8 small sticks of kindling. The fire caught easily, probably the insulation and hot face compound helped focus the heat.
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: New lining for the iron furnace
« Reply #1 on: January 12, 2022, 01:59:05 PM »
When the kindling sticks dropped below the top of the furnace, I swung the insulated lid over it to heat that as well. I didn't close it right away, so the whole lid face would get some heat including the sealing edge. After about 15 minutes I lowered the lid.

What surprised me after that was that the whole interior of the furnace gradually took on a bright orange glow. Just from a small amount of kindling charcoal in the bottom. There was no blast, mind you, this was all just from an inch and a quarter burner hole at the bottom as a vent and natural draft with the lid closed. The burner had been removed.

This really illustrated the reflective and insulative qualities of the blanket and coating. To have a 10 inch bore furnace walls glowing orange from just a few pieces of charcoal, and no blast is really surprising.  :med:

This is looking through the top vent at the furnace wall:
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: New lining for the iron furnace
« Reply #2 on: January 12, 2022, 02:10:04 PM »
I'm thinking to myself, cherry red, that's aluminum melting heat.  :scratch:

So naturally, I start looking around for my casting stuff, a crucible, spoon tongs, etc. I don't have a mold -- all my greensand is frozen anyway, but just for the heck of it, let's see if we can melt some Al.

I find some scrap aluminum bar cutoffs and pop them into the crucible:
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: New lining for the iron furnace
« Reply #3 on: January 12, 2022, 02:20:01 PM »
I set them into the furnace. There's some snap crackle popping going on from the somewhat dirty cast iron plumber's pot I'm using as a crucible. Well I just set a crucible and aluminum at 14F (-10C) into a hot furnace, so you might expect a little complaint from the items in question...  :hammer:

The walls cool quickly, since they have little thermal mass, but the charcoal is still glowing. I swing the lid back into place:
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: New lining for the iron furnace
« Reply #4 on: January 12, 2022, 02:26:08 PM »
I drop a couple more small sticks in, just to get the fire going again. But in only 5 more minutes I'm seeing a pot of the shiny stuff under a small skim of dross, ready to pour:
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: New lining for the iron furnace
« Reply #5 on: January 12, 2022, 02:38:12 PM »
And there you have it. A fast 10" aluminum foundry melt. Fueled by the dregs of a very small wood fire. On a cold winter day. With no blast, and only a small port inlet.

I'm going to be interested to see what it does with an oil burner and furnace blast.  :bugeye:

My only concern is that the lining seems so physically fragile. But we'll see what we see........  :dremel:
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline awemawson

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Re: New lining for the iron furnace
« Reply #6 on: January 12, 2022, 03:19:11 PM »
Impressive result Steve  :thumbup:

Just goes to show how much energy is lost through the walls with a conventional lining.

Andrew Mawson
East Sussex

Offline vtsteam

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Re: New lining for the iron furnace
« Reply #7 on: January 12, 2022, 04:48:58 PM »
Yes, Andrew, I'm wondering now whether this furnace might manage to melt iron with propane. Ironman built a smaller propane furnace that handles up to an A3 crucible.

Interestingly it takes just about the same amount of expensive lining materials for this size furnace as it does to make a the smaller one. Both require about 2" of fiber blanket thickness, so that isn't reduced for a smaller furnace, and the area  of coverage inside doesn't increase as fast as the volume does -- the old square-cube law. Before I decided to line this furnace, I priced out what it would cost to line the smaller propane furnace I use all the time. The bore would have been 7" and the total cost would have been about $20 in savings. So I opted to line the bigger furnace.

Another interesting point, if you do have a conventional heavy refractory lining, I bet this hot face coating would make a noticeable difference in melting speed, by reflecting a lot of the heat....plus the coating would be well supported in that lining application, compared to applying it to a blanket. I can see why larger commercial outfits would plunk down the money for this stuff.
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: New lining for the iron furnace
« Reply #8 on: January 13, 2022, 03:07:03 PM »
Today I tried the furnace on propane. As a test I loaded a small clay lined crucible with scrap glass-cutting diamond holesaws, which are basically a nut shaped heavy brass collar with a thin stainless steel ring. The burner was the atmospheric propane torch I made in another thread here. There was no blast -- just the torch.

Brass melted in about 20 minutes, and I fished out the rings before pouring into an ingot mold. The melt was a success, though it could have been hotter and better skimmed. But I was beginning to get zinc fuming out of the melt, and I didn't want to lose too much, so hurried it a little.

A larger blown burner will probably melt much faster, and also reduce zinc loss, while pouring hotter. I'd probably also cover the crucible and maybe add charcoal to the pot to protect the melt if I was going to pour a mould. But it was fun today to at least melt brass in mid winter.  :dremel:
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: New lining for the iron furnace
« Reply #9 on: January 13, 2022, 07:37:56 PM »
This was the burner: https://www.madmodder.net/index.php/topic,8633.0.html .

For more heat with propane, I may just try Ironman's much simpler blown burner, like the one on his small iron furnace:

(Although I do like an atmospheric burner like my present one -- maybe I'll find a larger design for one that will work for the furnace)



I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline tom osselton

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Re: New lining for the iron furnace
« Reply #10 on: January 13, 2022, 07:38:22 PM »
Regarding the Zircon paint I just came across this at:  https://shop.vitcas.com/vitcas-zircon-paint-coating.HTML  Sorry about the screen size specs to the right.
 
« Last Edit: January 13, 2022, 07:52:23 PM by vtsteam »

Offline vtsteam

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Re: New lining for the iron furnace
« Reply #11 on: January 13, 2022, 08:00:07 PM »
Nice, Tom.  :thumbup: Now have the Mfr name. It seems very reasonably priced, too -- not sure of the container size but it seems more than a pint like the ITC 100HT. The net weight appears to be 5kg which I think might be a liter. Unfortunately for me it doesn't seem available in the States.  :(

One thing I'm wondering about -- it says the color is beige. But Ironman's liquid is violet in color, until fired. Well anyway, nice find!
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline tom osselton

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Re: New lining for the iron furnace
« Reply #12 on: January 14, 2022, 07:23:14 PM »
I wonder if someone over there could stick it on a plane it definitely shouldnít be a fire hazard!


Offline vtsteam

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Re: New lining for the iron furnace
« Reply #14 on: January 14, 2022, 07:36:31 PM »
One interesting thing that came out of that, Tom is that it is actually zirconium silicate and water mixable. I am guessing that it's similar then to sodium silicate, which explains why it goes on as a kind of thick syrup, unlike the HT100, which is more of a clay-like paste. Also why it would be a better rigidizer than HT100. And finally, maybe we can find zirconium silicate over here.
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: New lining for the iron furnace
« Reply #15 on: January 14, 2022, 07:42:56 PM »
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: New lining for the iron furnace
« Reply #16 on: January 14, 2022, 08:32:02 PM »
Today I took apart and cleaned my oil burner for the iron foundry. It's a Kwoky type atomizing burner. Before reinstalling it, I was curious to see if it would draw and atomize oil on a winter day. Temp was just at freezing, and I thought waste oil might be too thick, so I opted to try diesel fuel.

It drew the diesel out of a can on the ground fine, and there was a fine spray pattern. So then I mounted it on the furnace to see whether the spray at low temp would ignite. I soaked a paper towel in fuel, set it on the bottom of the furnace, and lit it. Then I started the compressed air and slowly opened the oil throttle. Yup, it lit just fine. I didn't have the blower line hooked up to my vacuum cleaner, so I didn't test it with blast. But I have no doubt the furnace will run on diesel in winter.

I wasn't ready to cast anything yet, I had to locate my iron sand in a container in another shed, make a pattern, and find and check all of my iron casting gear, protective clothing flasks, etc. I moved the ring shanks, tongs, etc. to the tiny shed. The iron sand was not only frozen but also over saturated with water. In fall the container lid had cracked and rainwater had leaked in.

I brought the container indoors, and hope it will thaw overnight. It will be awhile until I can cast anything because the weather is going to be super cold for the weekend. I'll have to see what I can do about drying the sand out.
« Last Edit: March 02, 2022, 09:39:32 PM by vtsteam »
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline awemawson

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Re: New lining for the iron furnace
« Reply #17 on: January 15, 2022, 03:11:25 AM »
Steve I used to use the Zircon as a foundry tool dip years back. Things like stirrers and degassing plungers. It was a white thin paste that I diluted with water. May still have a dried out tub!

It set hard with heat but was liable to flake off and not very durable so Iím surprised itís suggested as a liner on the Kaowool. Sodium silicate syrup will Iím sure slightly soak in and set rock hard and be more suitable.

Iíve got the sodium silicate but not sure if Iíve any bits of Kaowool left over, if I have Iíll do an experiment.
Andrew Mawson
East Sussex

Offline vtsteam

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Re: New lining for the iron furnace
« Reply #18 on: January 15, 2022, 12:47:06 PM »
Andrew it's unclear which exact product Ironman uses for his furnaces - there appear to be many different products with the generic title "Zircon" -- they appear also to have a variety of formulations, and have widely different uses from pottery glazes to furnace linings.

If you watch Ironman (aka Luckygen 1001) building his small furnace in the YouTube video I posted about 8 posts ago, at minute 1:22 you will see him applying it to the ceramic blanket of his furnace. It's a violet colored, and thick enough for a good surface coverage rate. It heat cures to a white color. It would be nice to know what that particular formulation is because he has long term proven use of that product in his style furnace for melting iron.
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline vtsteam

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Re: New lining for the iron furnace
« Reply #19 on: January 15, 2022, 05:11:10 PM »
No furnace work for the short term. It's supposed to go to -11F tonight, that's -24C.

Then Monday we're going to reverse that trend, work our way up past freezing all the way up to 38F, through snow, sleet, freezing rain, and finally rain, with winds gusting to 26mph. Should be a right mess.

Just so we don't get too comfortable with a 50 degree/day warming trend, we're going right back down Tuesday night to 0 F. Should make for some interesting ice formations! And it looks cold for the rest of the week.....

Not good iron pouring weather, apparently.  :(

I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline PekkaNF

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Re: New lining for the iron furnace
« Reply #20 on: January 17, 2022, 07:58:47 AM »
Funny thing. Here the winter has been fluctuating too...Few days -22C etc. Then in less than 20 hours swing to +3C and then alternating order -3/+3 cold nights and snow or rain. Pretty icy roads here. Today on a little cold but snowed 10cm over glass smooth icy roads. We also got super cooled rain at -7C. It froze right when droplets hit anything solid -like road or windshield.

Looks like casting season happens on winter.

Offline vtsteam

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Re: New lining for the iron furnace
« Reply #21 on: January 17, 2022, 08:23:24 PM »
yes Pekka, it's been a weird winter. Today I woke to 8" snow. Plowed for 2 hours on the '51 John Deere M, and it turned to icy rain while I was half way through. I was soaked.

Anyway back to the iron furnace -- I'm just trying to dry the greensand out. I've got a tub of it indoors (with permission!) and though the inside humidity is in the 30's % it is taking forever to dry out. It's been 3 days and nights in an open container with me stirring it up every once in awhile, and it's still very wet. I even tried frying a couple panfuls on top of the wood stove, and they also were unusually slow to give up moisture. This is 60 mesh ceramics grade silica sand, with bentonite in it -- it's only been used a couple times to cast iron. I think the bentonite may be holding the moisture in.

It's  different feeling than the aluminum sand I've used for the last 20 years. That stuff was cheaper sandblasting sand mixed with hawthorn fire clay, 3 to 1. The aluminum sand dries quickly and has a good fluffy feel to it, and it squeezes by hand into a nice packed shape that shows good clean breakage.

The iron sand seems different, and I think that may be due to the bentonite. It feels sticky in the hand but it doesn't seem to pack as well and breaks more easily and not as cleanly. Of course it's hard to judge now since it's also too wet.

well time will tell, once I get this stuff dry enough.

EDIT: I was curious so I went back and checked out my original sand and bentonite mix proportions. I was intending 7.5% bentonite, but on recalculating the actual weight I mixed into 50 lbs of sand, I actually added 7% (3.75 lbs). I'd need another 1/4 pound to bring it to 7.5%. So I'll probably add that as soon as I can find where I put the bentonite (!) That also will help dry the mix just a little....
« Last Edit: January 17, 2022, 09:50:03 PM by vtsteam »
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline awemawson

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Re: New lining for the iron furnace
« Reply #22 on: January 18, 2022, 03:57:28 AM »
Steve,

When I 'over egged' the water in my greensand once and wanted to loose the excess reasonably quickly I set it churning in a cement mixer, and left a large gas burner burning pointing where the sand was tumbling. Well to begin with it was slurping, but started tumbling as it dried out !

No doubt a fan heater would do a similar job.

Andrew Mawson
East Sussex

Offline vtsteam

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Re: New lining for the iron furnace
« Reply #23 on: January 18, 2022, 11:57:58 AM »
I'm afraid the concrete mixer is just not going to be practical in this weather -- no indoor shop large enough for it. And apparently we won't get above freezing for a week and lots of wind. Arctic air on the menu for the foreseeable future. So no iron casting either. I guess the sand will dry by itself before I'm likely to need it. Not happy about any of that.  :bang:

Come on February!  :dremel:
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline mattinker

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Re: New lining for the iron furnace
« Reply #24 on: January 19, 2022, 04:33:50 AM »
Steve,

Steve I used to use the Zircon as a foundry tool dip years back. Things like stirrers and degassing plungers. It was a white thin paste that I diluted with water. May still have a dried out tub!

It set hard with heat but was liable to flake off and not very durable so Iím surprised itís suggested as a liner on the Kaowool. Sodium silicate syrup will Iím sure slightly soak in and set rock hard and be more suitable.

Iíve got the sodium silicate but not sure if Iíve any bits of Kaowool left over, if I have Iíll do an experiment.
I used sodium silicate on the ceramic fibre in my 200 litre oil drum kiln,it's holding up reasonably well.

I found a recipe for a kind of home-made ITC100 Silicate de Zircon 70% Kaolin 30%. I plan to try it on my next foundry project.

Cheers, Matthew