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The Shop => Metal Stuff => Topic started by: vtsteam on January 12, 2022, 01:39:49 PM

Title: New lining for the iron furnace
Post by: vtsteam 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.
Title: Re: New lining for the iron furnace
Post by: vtsteam 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:
Title: Re: New lining for the iron furnace
Post by: vtsteam 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:
Title: Re: New lining for the iron furnace
Post by: vtsteam 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:
Title: Re: New lining for the iron furnace
Post by: vtsteam 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:
Title: Re: New lining for the iron furnace
Post by: vtsteam 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:
Title: Re: New lining for the iron furnace
Post by: awemawson 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.

Title: Re: New lining for the iron furnace
Post by: vtsteam 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.
Title: Re: New lining for the iron furnace
Post by: vtsteam 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:
Title: Re: New lining for the iron furnace
Post by: vtsteam 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)



Title: Re: New lining for the iron furnace
Post by: tom osselton 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.
 
Title: Re: New lining for the iron furnace
Post by: vtsteam 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!
Title: Re: New lining for the iron furnace
Post by: tom osselton 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!
Title: Re: New lining for the iron furnace
Post by: tom osselton on January 14, 2022, 07:34:25 PM
Hereís some more.
https://www.mtixtl.com/1800c3270fhi-purityzirconiacoatingquart.aspx
https://www.zircarceramics.com/product-category/coating/zirconia/

And others
https://www.google.ca/search?q=zircon+coating&ie=UTF-8&oe=UTF-8&hl=en-ca&client=safari
Title: Re: New lining for the iron furnace
Post by: vtsteam 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.
Title: Re: New lining for the iron furnace
Post by: vtsteam on January 14, 2022, 07:42:56 PM
Okay, more info:

https://digitalfire.com/material/zircon
Title: Re: New lining for the iron furnace
Post by: vtsteam 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.
Title: Re: New lining for the iron furnace
Post by: awemawson 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.
Title: Re: New lining for the iron furnace
Post by: vtsteam 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.
Title: Re: New lining for the iron furnace
Post by: vtsteam 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.  :(

Title: Re: New lining for the iron furnace
Post by: PekkaNF 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.
Title: Re: New lining for the iron furnace
Post by: vtsteam 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....
Title: Re: New lining for the iron furnace
Post by: awemawson 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.

Title: Re: New lining for the iron furnace
Post by: vtsteam 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:
Title: Re: New lining for the iron furnace
Post by: mattinker 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
Title: Re: New lining for the iron furnace
Post by: vtsteam on January 19, 2022, 08:43:20 AM
Mathew is your present furnace used for iron? Or do you plan to use the future one for iron?
Title: Re: New lining for the iron furnace
Post by: vtsteam on January 19, 2022, 08:52:29 AM
I think the first casting I'd like to pour will just be a 2" solid cylinder of cast iron. That would come in handy for making pistons in the sizes I'm interested in. I'm thinking it may work to just pour that vertically with an open top. In which case it also doesn't need much of a flask -- I've done that before in a stainless kitchen canister with just some greensand packed around the pattern.

I did much the same thing with the Tee slot bars for the carriage on my new lathe.

(http://www.sredmond.com/vtsteam/Lathe/TeeBars5.jpg)
Title: Re: New lining for the iron furnace
Post by: mattinker on January 19, 2022, 10:29:52 AM
Mathew is your present furnace used for iron? Or do you plan to use the future one for iron?

The kiln I referred to is a ceramics kiln on which I used the sodium silicate, I was running it at up to 1100įC , the sodium silicate easily resisted those temperatures. I have bought the Zirconium silicate and the Kaolin which I intend using on a cast iron foundry. the kaolin which is porcelain clay fires at 1300į plus, I don't know how it will react with the Zirconium, but I think it's worth a try!

Cheers, Matthew
Title: Re: New lining for the iron furnace
Post by: vtsteam on January 19, 2022, 01:52:31 PM
Mathew, that should be really interesting.  :coffee:

I spread out a new tarp in front of our home woodstove (with permission!) and have been drying the greensand that way, but it is still very slow going!
Title: Re: New lining for the iron furnace
Post by: awemawson on January 19, 2022, 01:55:24 PM
Keep the cat off it  :bugeye:
Title: Re: New lining for the iron furnace
Post by: vtsteam on January 19, 2022, 02:39:18 PM
No cat!

Cat's and foundries don't mix.......
Title: Re: New lining for the iron furnace
Post by: vtsteam on January 20, 2022, 09:56:47 AM
I cleared up the tarp and sand by evening.

When I first started drying, I did a moisture check by heating a 100 gram sample of the greensand in our toaster oven, spread out on a scrap of aluminum foil. I brought the whole above 100C for 15 minutes. Weight loss was 10 grams to start.

At the end of the drying session, a second heated sample showed a 7 gram loss, so after a full day we went from 10% moisture content down to 7%. 

To cast iron, I need to drop it to 4%. To me the sand still feels quite wet in the hand.
Title: Re: New lining for the iron furnace
Post by: awemawson on January 20, 2022, 12:43:55 PM
Can you put it in a container and pull a vacuum to remove the moisture? I have an Edwards vacuum pump that I used to use for lost wax degassing, and once used this trick on my last remaining bit of core sand that had absorbed too much water.  It was surprisingly quick.
Title: Re: New lining for the iron furnace
Post by: vtsteam on January 20, 2022, 06:50:27 PM
Nope, no vacuum pump, Andrew.

Spread it out today for another few hours, turning it every once in awhile. Down to 6% now. Starting to feel a little better in the hand, but still too damp, yet.

I did some physical measurements, out of curiosity with a micrometer of various sands I have. The first was my aluminum and zinc molding sand -- which I've used for many years. I did several samples and averaged them -- surprisingly they were all quite close. This measures the largest average grain size -- it isn't a uniform sand. I rinsed all clay (hawthorn fireclay) off to do the measurements. It worked out to .012" or a #50 screen.

I then measured my ceramic grade quartz sand, which seems very uniform, also rinsing off the clay (bentonite) and it worked out to .010" or #60. Which confirms what the bag it came in said.

Finally I measured some "Fine" masonry sand purchased bagged at a local building supply store. It also tested out at #60. No idea how refractory it is as I've never tried it or mixed it with clay. But I'd like to try it with fireclay and see how it compares with my old aluminum greensand.

Interesting to find that my aluminum sand was so coarse. I thought it was up closer to #100 (.006") Several casting book authorities talk about #100 - #120 sieve for aluminum sand. Yet, my aluminum castings have always seemed to come out quite satisfactory, and better looking than most I see online. I did once try a bagged #120 blasting sand, but it had poor permeability, tended to short pour, and I ended up only using it for facing sand sometimes.

Anyway it was all something to do on a January day, indoors. High temps for the days will be well below freezing for the next week or so, and nghts around 0F with winds, so no casting yet.
Title: Re: New lining for the iron furnace
Post by: awemawson on January 21, 2022, 03:15:22 AM
Casting sand grain sizes are not logical Iím afraid when you compare the surface finishes on the castings. Certainly with iron quite coarse sands can give a surprisingly smooth finish due to the gas layer formed from the crushed coal.

Thereís quite a bit to it, permeability, refractory quality, surface finish, cohesiveness, ability to release the pattern and of course availability!

Artificially chemically bonded sands such as the phenolics and sodium silicate raise a whole new set of variables but are more predictable ( but have the disadvantage of not being reusable)

Towards the end of my foundry playing about I went over practically exclusively to sodium silicate. The sand when the carbon dioxide has done its bit is very stable, and intricate patterns can be pulled with little chance of it all falling out when inverted. For that to happen with a greensand mould is very disheartening!

Title: Re: New lining for the iron furnace
Post by: vtsteam on January 21, 2022, 01:11:16 PM
One of the facts I like about casting is that there are a huge number of variables...and so, a seemingly infinite number of  problems and approaches. And so, it tends toward creating a personal style for the person casting. What I like about it is, it's still an art. And an art based on personal experience.
Title: Re: New lining for the iron furnace
Post by: vtsteam on January 28, 2022, 07:02:26 PM
The sand has finally dried to a good molding feel. It's been 2 weeks in a low indoor humidity of 30%!

What's even more surprising to me is that I dried 100 grams of it in the oven, and it looks like it's now at a moisture of 2%.
That's amazing. Unless I'm doing something wrong, but yes 2% and it has very good feel, compacts in the hand nicely without sticking, and a squeezed clump of it breaks clean. That's just how I like it. But 2% seems numerically, at least, very low. I was expecting 4% to be about right, but it was too wet at that level.

Well, not complaining -- that's actually really good in terms of casting without steam gassing problems.

Getting closer every day to trying an iron melt. I've got cores, steel flasks, furnace relined, burner tested, crucibles, tools rounded up, found my ferrosilicon and plumbago, sand at proper temper, I need to make a pattern, and I need the weather to get better.

Major 13F 20mph winds blizzard predicted for tomorrow. Wednesday the opposite, 47F, but it will rain, which will be a mess with the snow, for sure. Well, pattern making for now........

Cylinders for a Rider Stirling of 2-1/2" bore.
Title: Re: New lining for the iron furnace
Post by: PekkaNF on January 29, 2022, 02:37:56 AM
Sounds good.

Any chance of some educational pictures on paternmaking?

I sympathize with the weather. Here it is has been few days nice. Some snow, but not more than I can shovel of the driveway. This morning temp is -8C. Fine, but weekend is pretty much only time I have a chance of changing some old AC ducting in the crawl space between ceiling and roof. For evening and tomorrow weather forecast  predicts blizzard and 30-40 cm of snow. Almost tempted to postpone. Maybe I just carry some firewood inside for oven and sauna to weather the storm. But it is hard not to what I have set to my mind.
Title: Re: New lining for the iron furnace
Post by: vtsteam on January 29, 2022, 07:17:31 PM
Sure, Pekka, here:

https://www.madmodder.net/index.php/topic,13467
Title: Re: New lining for the iron furnace
Post by: PekkaNF on January 30, 2022, 03:17:28 AM
Sweet!

You describe reasoning and thought process, that is something I enjoy following and I learn there way more than from traditional "how to" instructions.

Thank you very much,
Pekka
Title: Re: New lining for the iron furnace
Post by: RotarySMP on February 06, 2022, 02:15:39 PM
My first foundry was an A5 with Kaowool, and the Mullite hard face to the recipe of the Alloy avenue moderator Anon (A name which hasnt aged well  :palm: )

I used a little normally aspirated bunsen burner from 1/2" water pipe, a reducer  and a mig nozzle, and managed an iron pour (although the mould broke). It took nearly 2 hours for the melt though.

Amazing how little energy you have to shove in, if you have good enough insulation to not have it all fall straight out again.
Mark
Title: Re: New lining for the iron furnace
Post by: vtsteam on February 09, 2022, 05:24:07 PM
The day was predicted to reach 40F and was clear with little wind so I decided to try to cast the new piston pattern in iron. i got most everything set up. It seemed like there was just a huge amount of gear to collect together for an iron melt -- mainly because I haven't done one in several years. Tongs, shanks, skimmer, flasks, leather protective gear, face shield, molding tools, oil fuel, vacuum cleaner, hoses, iron, greensand, ferrosilicon, riddle, ingot mold, plumbago, paring dust, and.....wait a minute, where's my compressor? Oh yeah, next town over, half an hour away......and a half hour back at my in law's garage.  :doh:

I Did the drive, well that killed things until after 2;30, with only a couple hours of good light left, but tomorrow was predicted to snow/rain, so I thought I'd give it a try. I set an A6 crucible with 5-1/2 lbs of iron in the furnace. Hooked up vacuum, compressor, diesel oil fuel, set comp pressure at 60 psi, soaked a small piece of rag in fuel, stuck it in the furnace, lit it with a torch, and then cracked open the oil valve. Whoosh! That familiar big yellow flare up on oil start. Always gets the adrenalin up. The outside temp was now 38F, but that didn't seem to stop the atomized oil from an instant startup. This furnace does not need propane to warm the walls before feeding oil.

I started the vacuum cleaner and then she roared - a little sooty smoky, so I eased the oil valve down until the smoke just disappeared. The furnace walls lit up almost immediately. That's the reflective face of the compound at work. It's a very fast heat up. So fast I started to wonder if I'd have time to make up a mold -- I used to have an hour and a half, more or less, but within 5 minutes the iron and crucible were now bright orange.

Unfortunately I was seeing some black smoke and soot flowing back around the burner pipe where it was attached. That meant the seal wasn't good around the burner pipe, and the pressure of the vacuum cleaner was apparently blowing some air fuel mix back out. The last lining was solid firebrick and clay ganister, so the burner was effectively cemented in for a 4" thickness. Now with this new blanket insulation, it's much easier to have a leak. The hot face coating has absolutely no strength -- It's like a thick paint layer over a cotton ball, so it doesn't hold tight to anything. I probably had just not pushed in enough insulation blanket around the burner hole when I installed it.

I kept going for a couple more minutes, but I started to see small flames licking out around the burner, so I reluctantly made the decision to abort. I shut off the fuel, the blast and the compressor. With everything shut down, the furnace was still brilliant orange hot, as were the crucible and the iron pieces. It took about a half hour to get the furnace unloaded and cool enough to patch more blanket in around the burner. I sealed it with hot face compound.

So no metal poured, but I was very pleased with the performance of the new lining so far, and I do have everything now collected for a melt as soon as the weather cooperates. I hope that can happen this weekend.  :dremel:
Title: Re: New lining for the iron furnace
Post by: tom osselton on February 09, 2022, 05:48:03 PM
Itís almost amazing how fast it heats up with the blanket.
Title: Re: New lining for the iron furnace
Post by: vtsteam on February 09, 2022, 09:57:12 PM
Sure is, Tom. I just hope the lining holds up to the amount of heat I'm pumping in. That Kwiky burner really puts it out. I was running the vacuum cleaner blower full power without a waste gate or a variable supply.

I've got an old HF router speed controller, which I'll hook up next time to the vac, and maybe turn it down a little to start with and see how fast she heats up. I still feel like that hot face coating is fragile. It's pretty expensive, and the blanket under is not rated for iron temps, or the violence of a direct oil blast, so I might back off a little next time and see what kind of heating rate we get.
Title: Re: New lining for the iron furnace
Post by: awemawson on February 10, 2022, 02:51:07 AM
Can you set the burner in a block of fireclay to give it strength to the furnace outer shell. If itís not too large the heat loss of not being Kaowool at that point will be minimal.
Title: Re: New lining for the iron furnace
Post by: vtsteam on February 10, 2022, 08:18:09 AM
That's Plan C.  :dremel:

I might do a furnace run-up to check for leaks today if precipitation holds off.
Title: Re: New lining for the iron furnace
Post by: vtsteam on February 11, 2022, 12:10:32 PM
I made up some new small molding boxes to do a piston casting. Smaller boxes are easier to roll, and use less sand, so I can mold two at once from the same pattern with the 50 pounds of sand I have.
Title: Re: New lining for the iron furnace
Post by: vtsteam on February 11, 2022, 05:13:36 PM
Wooden flasks don't last long when pouring iron. Generally it happens when there's an overflow from the sprue basin that reaches an edge, or a spill at the edge, or often just touching the crucible to the edge of the flask while pouring. Generally the rest of the box suffers less. It's mainly the top edge where the crucible is being poured from.

I do have some steel flasks that I built years ago. They are heavy and, as in this case, they aren't always ideal for the shape of the pattern you want to pour. So it's easy to quickly put some wooden boxes togetherfor a special need, but it would be nice if they lasted longer. Their light weight makes molding easier, particularly if the pattern is tall or large and you have to roll a few times.

I've thought about keeping the lightt weight of wood but adding more heat resistance by inlaying a flat metal edge. Better would be a channel shape, Though that would need to be flush with the wood on all three edges. So, it's impractical.

Then this morning I thought, why does the metal protector have to be attached to the flask? Just use a piece of heavy  angle iron,cut to size and lay it on top of the pouring edge after the mold is made up. That will protect the edge the side, and also stop any sprue overflow. Adds weight, too when it's needed, Simple!!  :doh:

And that's just what I did.

btw. poured iron today........
Title: Re: New lining for the iron furnace
Post by: tom osselton on February 11, 2022, 05:19:09 PM
I was going to mention that to protect the wood. Iíve never painted my boxes but do have places on the sides to bolt both sides together in case of separation on larger pours.
Title: Re: New lining for the iron furnace
Post by: vtsteam on February 16, 2022, 05:08:27 PM
I did a third iron melt in a week today. I timed it at 15 minutes from start to melting 6 lbs of iron in an A6 crucible, and with slagging and ferrosilicon addition, plus bringing it up to pouring heat, it was 21 minutes total from lighting the furnace.to pouring iron.

I used about a gallon of diesel fuel for that, now in winter, when heavier oils would not flow or atomize as well. I'm guessing there's enough heat  in the furnace after to probably do a zinc melt with no more fuel, or an aluminum or brass melt within a few minutes of lighting up again. I imagine a second iron melt might be 10 minutes more.

This same furnace and same burner, with 4" of firebrick and ganister insulation took 1-1/2 to 2 hours to pour iron 9 years ago, and those were borderline hot enough sometimes.

The only problem I've had so far is that a small piece of the lid blanket, (which was pieced together from leftovers of the main furnace lining), has come loose twice. That didn't happen during a melt, but after cooling. The blanket tends to shrink a litlle after an initial melt, and where once it was packed in place at the edges, it loosens. I did cement all edges with sodium silicate, per Ironman's video, and covered the joints with the hot face compound, but the blanket still shrank and loosened.

Today I put positive retaining in by screwing with self tapping metal roofing screws from the sides of the lid into the looser blanket pieces. I hope that holds better.
Title: Re: New lining for the iron furnace
Post by: tom osselton on February 16, 2022, 05:32:09 PM
I had some pieces that had to be anchored on mine as well I used nicrome wire as pins or bent as staples and found no problems after that. Iím going to have to build a oil burner Iím still using propane.
Title: Re: New lining for the iron furnace
Post by: vtsteam on February 16, 2022, 08:05:32 PM
Tom I can heartily recommend the Kwiky burner. I like it because it doesn't require furnace pre-heating with propane. Instead, it  produces a very fine atomized oil mist that I believe results in a more efficient flame with better mixing than other burners I've seen. There's no welding, it's physically compact compared to most other burners and uses off-the-shelf quite small plumbing fittings.

http://metalshop.homestead.com/How-to-Build-The-Kwiky-all-Fuel-Foundry-Burner.html

The results I'm getting show how well it works.
Title: Re: New lining for the iron furnace
Post by: vtsteam on March 02, 2022, 10:03:37 PM
Well I've had several very successful Iron pours (detailed elsewhere) The lid has been a little problematic as the blanket insulation has shrunk and detached from the steel shell in several places. I've had to add sheet metal screws through the rim into the insulation all around, and done several patches of the hot face compound in damaged areas. That gets expensive. Damage was caused by the insulation dropping a half inch and scraping across the top of the furnace when the lid was rotated out of the way.

I think I've got it mechanically fastened today so it won't drop more, and also I've increased the lift mechanism's throw.

The only other problem was the burner attachment and support, since the blanket provides none. Today I fabricated a heavy metal bracket the is welded to the outside of the furnace on a removable plate. The burner sits on top of that and is fastened to it with two SS hose clamps. That makes it removable but very firmly fixed. where it penetrates the furnace, 2" of ganister surrounds it in a plug, rather than the blanket. That seems to have solved any leakage and support problems.

I'm looking forward to my next melt - possibly tomorrow. I need a third cylinder casting, and I'd also like to try to do better with the Westinghouse twin. Mainly in making a core for it (somewhat complicated in shape), and in using facing sand and disk brake rotor metal (per Ironman) and 0.25% ferrosilicon.

One question I have is that I've reported quite a lot higher metal loss than Ironman. I'm wondering whether that's in slagging, and/or oxidation? Spills are understandable losses, but I'm wondering whether I'm running too hot too fast with diesel fuel?
Title: Re: New lining for the iron furnace
Post by: ironman on March 03, 2022, 07:59:28 PM
The zircon paint I used on the furnace is no longer made but I still have plenty for my needs. A lot metal casters on youtube use satanite and it seems to work quite well for coating ceramic fiber used for iron melting.
Title: Re: New lining for the iron furnace
Post by: vtsteam on March 05, 2022, 04:17:06 PM
Thanks Ironman, I'll look into Satanite.

After yesterday's pour the furnace showed some serious damage to the lining, which up til now had done quite well. I'm not sure of the cause but most of the damage occurred where the flame from the burner impinged on the wall near the bottom of the furnace. There was definitely melt-back. I believe the cause was either too much heat or possibly an oxidizing flame that I didn't notice -- I do tend to run slightly rich by preference. The only difference between this melt and all prior ones was that I used an off-road diesel fuel instead of regular auto diesel.

The off road diesel seemed slightly thicker, and startup with it was a little less easy in this cold weather. It didn't seem to atomize as well early on. I'm thinking it's denser with possibly higher energy content. I might have to cut back on the burner in future.

To repair the sunken and damaged spots near the bottom, I decided to use ganister. There really seems no way to easily repair ceramic blanket with more blanket. I find that blanket joints tend to become a focus location for overheating.

In any attempted repair with more blkanket, the new blanket patch seems to shrink after  re-heating, leaving a bigger crack at the joint. That exposes more raw blanket to the heat, unprotected by hotface compound . You can't just solve those new cracks with hotface compound, because it is so thin-- basically a paint coat, and it's impossible to get it into joints. The hotface compound is also very expensive -- at about $50-60 a pint.

So I am patching with ganister (fireclay and coarse silica sand and/or ceramic grog). That does a good job of filling the  sunken blanket damaged area, and bakes to a hard exterior, easily paintable by the hotface compound. Since there still is a fair amount of insulating blanket behind the ganister patch, I don;t think the melting rate of the furnace is affected at all and it is MUCH tougher than the blanket and hotface. This is particularly important near the bottom of the furnace where the burner flame is playing directly on the wall.

I think that for non-iron furnaces, with lesser burners, these problems probably don't occur, but in my case witha possibly hotter fuel than I was using before, and very efficient burner I think we're at the limit of how intense a flame the blanket and hotface can absorb -- in that particular area.
Title: Re: New lining for the iron furnace
Post by: ironman on March 07, 2022, 07:39:45 PM
Have a look at chirpys tinkerings channel on youtube , he copied my furnace from the video showing how it was built. Because he could not get the zircon paint he used satanite instead. He has a video making a furnace using ceramic fiber and coating it with satanite. I have never used satanite but it seems to be a good substitute for the zircon paint I use.
Title: Re: New lining for the iron furnace
Post by: vtsteam on March 10, 2022, 09:44:34 PM
I've received some Satanite, and will be trying it out.
Title: Re: New lining for the iron furnace
Post by: vtsteam on May 07, 2022, 03:24:58 PM
An update on my furnace:

I received the Satanite, and it's a good and inexpensive fireclay based coating. It is high in strength and you can put it on thicker than ITC100 (which requires thinning with 50% water). However, it isn't a highly reflective coating, like the ITC100. Best practice would be to put on the Satanite first to a reasonable thickness to protect the blanket, fire it to harden, and then paint on a light coat of ITC100 over that for the benefits of a reflective coating.

On my furnace, the lid insulation has been a continuing problem, despite mechanical fastening. The cause was in trying to piece the blanket on in layers horizontally.  Ironman in the propane furnace construction video below shows doing the lid in many vertical profile pieces, which are adhered to the lid with sodium silicate.

In my experience, horizontal blanket layers cannot be cemented together successfully with sodium silicate. In using sodium silicate, the blanket-to-steel bond is good, but the blanket-to-blanket bond is poor. the adhesive is absorbed by the blanket and yields a dry joint.

When I first built mine, I pieced the blanket in horizontal layers because I only had remnants of 2" thick blanket to work with, (not 1" thick, as Ironman used in the propane furnace lid). The remnants were irregular in shape, and weren't large enough to cut out the numerous vertical sections required for vertical piecing. I did split the pieces into 1" thicknesses, in order to create two layers, which would allow staggered joints.

However after half a dozen melts, my lid insulation was continuing to loosen and drag across the top of the furnace when opened. Pieces would flake off -- and the lid required continued patching with expensive compound. An attempt at reinforcing with metal fasteners horizontally through the rim of the lid also did not completely solve the problem. Where there were vertical joints in the lower layer of blanket, cracks widened and blanket shrank away from the joint because hotface compound couldn't reach very deep into the cracks to protect it. Large sections of blanket would loosen and sag.

Finally, yesterday, I removed all of the insulation from the lid. I now have sufficient 1" thick blanket to do the vertical layer type blanket insulaation. I've ordered some more sodium silicate, and hope the lid built this way will last better

Ironman's propane furnace build:

Title: Re: New lining for the iron furnace
Post by: vtsteam on May 21, 2022, 10:19:49 PM
Today after some delay I attacked the lid. Well I guess attack isn't the word -- I trashed it and started again.

New (scrap) metal welded together. new insulation blanket installed. The philosophy this time WAS to do only vertical piecing. Horizontal layers don't work, because there is no reliable way to laminate layers together. Vertical piecing means that every individula section of blanket is in contact with the top of the lid and is cemented there with a generous amount of sodium silicate.

I started out trying to do the vertical half-width slice-of-pie method, as shown in the above video, but pretty quickly that showed it wouldn't work. My furnace lid is about 17" in diameter, while the oil can in the video is about 12" Maybe you can cram the inner ends together in a 12" circle, while the outer ends expand enough to fill the spaces, but not on a wider lid.

So I ended up doing a sort of roll-up method, with strips and pieces attached concentrically, except at the center. The final 3" around the exhaust hole was done in the pie wedge method -- and it made sense there -- especially because I wanted to have a leg of each piece extend up through the hole -- similar to the way Iron Man did it in the video above.

Here is the new lid packed with insulation:

Title: Re: New lining for the iron furnace
Post by: tom osselton on May 22, 2022, 07:24:50 PM
I had the same problem when my son cut off the lid too shallow forcing us to lay it down horizontal my fix was to use some nichrome wire going through the fiberwool and the lid Iíve never had a problem with it so far mind you Iíve only done alu & brass so far.
Title: Re: New lining for the iron furnace
Post by: vtsteam on May 22, 2022, 07:36:28 PM
yep, Tom I think the big problems arise when you start getting to Iron melting temps for a protracted time. It's a different world.
Title: Re: New lining for the iron furnace
Post by: tom osselton on May 23, 2022, 06:19:41 PM
I was thinking that too maybe Iíll pick up another stainless beer keg or tig some banding around it to extend it down if itís a problem.
Title: Re: New lining for the iron furnace
Post by: vtsteam on May 23, 2022, 10:18:49 PM
Tom my latest lid really has held up perfectly after the first couple of heats. It looks new even with a 1 hour iron melt. Placing the blanket on edge and using 1" blanket and generous amounts of sodium silicate is the way to go. This cements every part of the blanket edge to the top of the lid. The blanket is strongest in this direction.

I did earlier try putting fastenings into the side of the lid on my first lid -- didn't work. That lid had the layers of blanket running horizontal. It will never hold that way at iron temps.

I covered the new lid with 3 coats of Satanite, which is really tough stuff once fired. Much, much, much stronger than ITC HT-100 (and much, much, much cheaper).

You can paint coat the Satanite afterwards with ITC if you want (I have). However,  I'm not sure that will really do much in the long run. The reason is, when melting at iron temps, a dark brown glaze of vaporized slag quickly covers the interior furnace coating so it's no longer reflective.

 I have a feeling that after 3 or 4 melts there's going to be no difference between plain Satanite, and Satanite covered with ITC. I'm sure ITC works great for forges, and probably non-ferrous foundry furnaces. But at ferrous temps, it's a different story.
Title: Re: New lining for the iron furnace
Post by: tom osselton on May 24, 2022, 03:22:28 PM
Interesting maybe that ď dark brown glaze ď is the reason you saw a difference in melting times.
Title: Re: New lining for the iron furnace
Post by: vtsteam on May 24, 2022, 03:40:36 PM
Doesn't look that way, Tom, because I coated the furnace lining with new ITC before the last melt, and that one took an hour.

I'm still wondering about the disk rotor metal itself. I think the earlier iron I had (from a cast iron section of rail) was easy melting. It also poured easily without inclusions, produced nice easy machining gray iron even without ferrosilicon.

Earlier than that I was using iron from cast radiators, and had lots of problems with inclusions -- though this might have been bad crucibles, too low pouring temp, etc. as well. I might try melting radiator metal again to see how well it works now with more experience, ferrosilicon and a better setup all around.

Trying to think of a subject to cast maybe this afternoon. Something simple but useful....
Title: Re: New lining for the iron furnace
Post by: vtsteam on May 24, 2022, 08:01:07 PM
 I finally did cast something from radiator scrap this evening, just to see if there was any difference in melt times. Definitely was -- exactly half, 30 minutes to pour, compared to an hour for disk rotor scrap for the Westinghouse Twin. Melts were the same size, 7 pounds each. Both got 11 grams of ferrosilicon. This time I just cast a rod of iron, using a pipe 10" long as a pattern to try to get some 1-1/4" stock. I just plugged the ends of the pipe with sand. The pipe was 1.335" actual dia. so some machining allowance was available.

I figured it would be a handy piece of stock to have around. It poured uneventfully, though lots of slag was skimmed off. Losses were high -- about 20%. It poured just a tad short because of that -- the sprue and riser didn't completely fill -- lost maybe a half inch of head height. It was a shallow flask - 2" each, cope and drag.

There was a little shrinkage towards the ends -- I probably didn't place riser and sprue in ideal positions, but it was just a quick judgement call. I'm very interested to see if there are any internal casting flaws, and how hard it is. I had big problems with both blow holes and slag inclusions in my early days of iron when using radiator scrap. But maybe things will be different this time around.

Here's a photo of this quick casting attempt -- just before dinner!

ps....after dinner -- the runners sawed off with a hacksaw, which generally indicates it's going to be nice gray cast iron for machining.  Also the worst shrunk spot calipered to 1.28" thickness, so I can probably get 1.25" dia for almost if not the whole bar. Not that I have an immediate need for it, but both my lathes and all my QC tool holders fit on a 1.25" posts, so it's a useful size for me. Also it can be used for small engine cylinder liners and piston rings.
Title: Re: New lining for the iron furnace
Post by: tom osselton on May 25, 2022, 04:28:56 PM
It looks great on the outside it will be interesting to see if itís inclusion free when you get around to it.
Title: Re: New lining for the iron furnace
Post by: vtsteam on May 25, 2022, 05:12:07 PM
Tom, I machined half of it down to true 1.25"  to look for flaws and there weren't any. It's very nice machining iron.

Title: Re: New lining for the iron furnace
Post by: tom osselton on May 26, 2022, 03:31:36 PM
Excellent looking piece youíll have to get busy stocking up on sizes now for the winter months.
Title: Re: New lining for the iron furnace
Post by: vtsteam on May 26, 2022, 08:34:44 PM
Thanks , Tom.  I've got a whole lot of leftovers from the problem castings I had years ago both castings and sprues, etc. lots of flaws misruns, mistakes.

 I'd like to see if I can recast that metal now that I'm better at it. I don't want to risk some important casting with it, but casting raw metal stock like that bar is easy and forgiving. And even if one section has a flaw, likely, you can use the rest of whatever shape you cast. Maybe some thicker rounds and some square bars and some plate.....

It would also feel good to kind of right those mistakes. Unfortunately it's going to rain the next few days, but when it clears up... :dremel: :dremel: :dremel:

Oh also, I checked the underside of the furnace lid, and it is absolutely pristine after a couple of melts. I really like the Satanite.