A thin hotface medium/low mass beer keg (drum size) furnace for melting Iron

Discussion in 'Furnaces and their construction' started by PatJ, Aug 24, 2017.

  1. PatJ

    PatJ Silver Banner Member

    I have always had trouble with melting and pouring iron, and some of that is due to the fact that iron is very particular about how it is melted, and part of it is due to what I think is too much mass in a furnace.

    Others have used high-mass furnaces successfully for many iron melts, and so I can't totally blame my iron problems on the fact that it takes 30 minutes to warm up, but I have also seen others use low-mass furnaces with great success in melting iron, so I know it would certainly help things along if the melt went faster.

    So with the intent of speeding up the melting process and expediting my iron-melting experiments, I have decided to make a new iron melting furnace, centered around a beer keg (edit: As it turns out, it ends up being the diameter of a 55 gallon drum, and requiring four beer kegs).

    I tried to keep the dimensions inside a standard beer keg, but could not do that and also make the furnace large enough to contain a range of crucibles, such as a #10, 16 and 20.

    So I chopped up the beer keg to make it larger.

    For the hot face, I am using 1" thick Mizzou, and so the trick has become how to ram a hot face that is only one inch thick, but quite tall.

    My solution is to make stacking shell sections so that I can ram one section at a time.
    Hopefully I can keep it all straight as I go up; I think I can with 1" wood spacers.
    Edit: The stacked shells are not necessary, just use a single shell and ram about 1" of refractory at a time, packing it well with a 1/2" wood dowel rod.

    Everything is waterproofed with heavy duty foil tape.

    I have tried a dual burner arrangement in the past, and did not really find an advantage to doing that.
    The dual-burner arrangements that are seen in commercial units sometimes occur when the crucible and furnace are relatively tall, and so the burners are stacked one on top the other, but some commercial furnaces do have dual burners at 180 degrees at the same level (at the bottom of the crucible).

    I have accumulated a lot of clean iron (about 1,000 lbs +) which consists of motor end bells.
    I do model engine work, and it is very advantageous to have an engine cast in iron for the machinability and wear characteristics of gray iron.

    I have spent a serious amount of time studying and reading about the iron success stories, and so hopefully I can pull it all together and get somewhat consistent iron melts/pours, or at least as consistent as what some others have achieved.

    My original design had 1" of Mizzou, and 1" of ceramic blanket, but I decided to err on the side of caution and use two layers of 1" ceramic blanket on the outside of the Mizou shell.

    For the lid, I first considered using the metal beer keg top, but I may cast a dome in Mizzou, and then lay a layer or two of ceramic blanket over that, and rigidize the ceramic blanket with ITC-200 mixed with water and sprayed on in a couple of coats, thus avoiding using the metal lid, and avoiding the metal lid from becoming a big heat sink.

    Below is a section of the furnace, and the cuts on the shell.
    The shell will have to be pieced back together, but that is not really a problem.

    I will be using stainless crimped 1" refractory needles to prevent cracking. Others have used them and reported no cracking with extensive iron melts, so I felt it worth a try, especially since my last furnace has cracked badly with no needles, and I noticed photos of other people's refractory also cracking without needles.



    r20170610_141911.jpg r20170610_144903.jpg










    I modified the design a bit from this original sketch, and the modified design is posted later in this thread.

    Last edited: Nov 29, 2018
    Scott K. likes this.
  2. PatJ

    PatJ Silver Banner Member

    I made a guide to go on the router in order to cut some inner form reinforcements from plywood, and that worked well.

    For the center former, I stacked the round wood forms, and spaced them with some sticks.

    For the outer former, I cut the sonotube to expand it out.

    The solution to why my photos would not load hit me in the middle of the night.
    It is the browser. I was using Chrome, and there appear to be some compatibility issues.
    I changed to Windows, and bingo, here we go.








    Last edited: Aug 31, 2017
  3. Petee716

    Petee716 Silver Banner Member

    I use 12" and 10" diameter HVAC duct for forms. The heavier stuff. I got it from a commercial supplier. My 12" od outer layer was sand/fireclay but since youre using wool you could backit up with loose sand to hold it solid and concentric. I had no trouble getting the mizzou in there. It doesnt need to be rammed so much as finessed, but is positively doable.

    Jason likes this.
  4. PatJ

    PatJ Silver Banner Member

    I was worried about ramming Mizzou with the needles in it.
    I have never used needles, and so no idea about ramming 1" needles in a 1" wide space.

    I spliced a section into the outer stacking form sections, and hot glued some guides around each section.

    Wrapped each section with foil tape and wrapped the center form with tape also.

    The outer stacked forms should be 1" above the top of the inner form.
    In the photo it looks like the outer forms are much higher than that, so either I measured wrong, or that is an optical illusion, but at any rate, the forms will be rammed upside down as shown in the photos, so there will be 1" of Mizzou on top after it all gets rammed.

    The center form is glued to the wood base to prevent shifting and floating.
    I will use a few 1" wood spacers as I go with the ramming, and shift them upwards with each stacking outside section, and hopefully everything will remain aligned correctly.







    Last edited: Aug 31, 2017
  5. PatJ

    PatJ Silver Banner Member

    For the tuyere, I am going to extend the refractory out a bit from the furnace, since in the past I have had difficulty getting a good seal between the refractory and the burner tube.

    I will extend the Mizzou out about 2" using the two PVC pipes as forms.

    Last edited: Aug 31, 2017
  6. Jason

    Jason Gold Banner Member

    Now WHY didn't I think of that one? I mess with HVAC... DUH!

    Pat, I used 1" mizzou, no needles.... No cracks either. Got lucky I guess. I didn't know about needles back then. Next furnace........
  7. PatJ

    PatJ Silver Banner Member

    I have heard that some do not get cracking without needles, but the oil burners used for iron melting seem to be particularly harsh on furnace hotfaces.
    Using the exact amount of recommended water in the refractory mix probably has something to do with not getting cracks too, and I have a concrete mixing tub that I will use with a hoe on this build, and I will be religious about the amount of water used, even though that makes for some very difficult manual mixing (with a good dust mask I should add).
  8. PatJ

    PatJ Silver Banner Member

    I ran across a pipe intersection program online, and while the demo version did creaate an onscreen template for the tuyere/furance intersection, the demo program does not allow you to print out the template.

    I looked at the price of the software, and for what it does, it is very prohibitively priced.

    So what I will have to do is figure out how to make my own pipe intersections in Solidworks.

    I need to make a template where the outer PVC tuyere form meets the inner form (the inner PVC pipe can extend straight into the inner sonotube form).

    And I will make another template where the outer PVC pipe exits the side of the beer keg shell.
    That should make a good clean exit for the tuyere hole instead of the usual ragged hole that I grind in the side of the furnace shell.

    That is as far as I got on this build.
    I have had a recent work project avalanche, which is good, I can start eating again, but the downside is I have to work like crazy for a while on work stuff until I get caught up.
    Last edited: Aug 26, 2017
  9. Tobho Mott

    Tobho Mott Silver Banner Member

    Oh, I just noticed you edited in a bunch of pictures above, cool!

    I used printable templates (generously supplied by Razortoe on the other forum) to figure out where to cut the 3 different shaped tuyere holes in my forms and outer shell too, that worked great! This looks like its going to be a really nice furnace, nice work.

    Getting the dense castable into the 1" gap should not be too difficult. I did not use the needles, so that may make it a little trickier, but one thing I highly recommend is to use some kind of vibration tool, it's amazing how that will make refractory mix you'd think was so dry it could only be rammed up, flow! My 2nd attempt at a vibration tool was easy to make and is described in my furnace build thread here, but one thing I think I failed to mention there is that it worked so well I could vibrate the entire 12"+ depth of my hot face even after the forms were filled to the top. I only added a couple inches at a time with a small scoop and vibed each layer separately to build it up, but had no trouble sinking the reciprocating vibration bar down through all previous layers to do the whole thing at the end, the hope being to avoid any obvious laminations that might crack apart later.

    The refractory tuyere is a neat idea. Try and get some good pictures of how you set up the forms for "pouring" that part!

  10. PatJ

    PatJ Silver Banner Member

    I was having problems using Chrome, and switched to Windows Explorer, and the photos load fine now.

    I have considered vibrating the mix, but I don't really want to settle the heavier stuff to the bottom.
    I guess will just ram it with a stick. That should work since I only have to ram 3 or 4 inches at a time.

    I will take more photos as the furnace progresses.
  11. PatJ

    PatJ Silver Banner Member

    The online demo program that I tried for making the templates for the intersection of the tuyere tubes with the furnace forms turned out to be very expensive, and so I will have to figure out how to create flat sheet metal sketches from a circular tube that has a cut on its end.
    I found this video, and I think this leads to the solution, but I don't fully understand it yet.

    A template made from a tube:

    I will take a break from work in a little while and tried this in SW.

    I tried the procedure described starting at 13:00 in the video above, using a round tube with a slit in it, with the end cut off at a 45 degree angle, and it actually created a flat template.

    Pretty cool.
    I knew SW could do it; it was just a matter of whether I could do it with SW.
    Last edited: Aug 26, 2017
  12. Petee716

    Petee716 Silver Banner Member

  13. PatJ

    PatJ Silver Banner Member

    I saw that program, but I confused it with the commercial version which goes for perhaps $400, and I was thinking that only the paid commercial version (not the demo) would make prints.
    But now I see that the version you refer too also will make printouts.
    Unfortunately I run a separate computer for internet/email only, and it does not have a printer attached, but perhaps I can save the print file either to a file or get it as a screen capture.

    At any rate that is good to know because it is a quick and easy program to use, and free too !
    Thanks for pointing that out, I will give it a try.
  14. PatJ

    PatJ Silver Banner Member

    I was able to save the printout as a .PNG file, and then pull that into AutoCAD as a raster image, which I could then scale to the correct size, and transported to my machine with the plotter.
    Very nice, thanks again.
  15. OCD

    OCD Silver

    Hey Petee,
    Not to side track or HJ your thread but do you or any of you other folks own or have access to a drafting / design program connected to a CNC which can mill 1/8" aluminum flat plate?

    Need a backer plate made for my Foam Miter Cutter.
    Have to dig the draft up but the backer plate is under 12" x 12".
    Already have a hand drawn layout draft of the what's and where's (specs).
  16. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I can't remember if it in some one else's post (or not, or maybe at AA?) so apologies if this is a repeat but every time I see a reference to ramming castable refractory, I can only relate that for me it did about zippo for producing dense defect free refractory castings compared to vibration....and good full body vibration means you just scoop it into your form and watch the vibe make it flow like liquid. It's faster than ramming too. I did some very complicated shapes with 1/2" wall, and expendable foam coring with nothing other than ladling it in and turning the vibe on. Mixing the refractory in a bucket with a drywall mud paddle and a 1/2" drill made a 5 minute pain free job out of that dry mixture. But when the vibe hits it looks wet and just lays right down in a state of submission. If the heavier materials fall to the bottom or becomes soupy on top, you've either over-vibrated it or added too much water. For Tuyere, I just shaped a piece of EPS which had a step feature in it, wrapped it in packing tape, and glued it in place. When the refractory cured, it takes about 5 minutes to dissolve the plug with acetone and then grab the tape with pliers and pull the rest out in one shot.

    The furnace lid below was cast in two steps; the gray inner swirler was cast with a Harbison Walker dense castable and the outer spoked greenish colored bit used and HB insulating castable. All hollows were expendable polystyrene cores wrapped in packing tape for release. It was a crazy shape but was just seeing how far I could push the process.

    7 Lid.jpg

    Last edited: Aug 31, 2017
    Dan Harold likes this.
  17. PatJ

    PatJ Silver Banner Member

    That is a crazy shape.
    I will have to go back and find your thread and read it.

    I guess my main concern is with the needles being in the mix, and settling or getting out of a random position.
    Last edited: Sep 14, 2018
  18. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Here's a link. It was decimated by the Photobucket debacle but I rebuilt it.


    ..and here's where the castable refractory stuff starts.


    I understand the concern. I haven't used needles but I'm thinking needles may make ramming even more difficult and get lodged up in narrow openings so vibe might even be more helpful. Might be worth a test piece like a hollow spoked plinth or something like that to get your feet wet with only a small amount of material in play.

  19. PatJ

    PatJ Silver Banner Member

    Yep, you got nailed on the pb photo thing for sure.

    Maybe you could put a build-lite thread about it here, and just hit some highlights.

    That is some serious fabrication for sure.
  20. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Oh, and one other thing, in addition to using the drywall mud paddle to mix the castable refractory (my first hand mix was quite the work out), I also found that pre-measuring the water and castable, then mixing about half the castable refractory with all the water, then adding the remaining refractory in two or three steps to the recommended ratio helped mixing quite a bit. It helps prevent it from balling up so bad and just makes getting it evenly mixed much easier. I can remember my first go with the stuff thinking I had measured wrong, it was so dry. So I overdosed the water and it ended in a fail that wouldn't cure properly. Thankfully it was on a smaller experimental piece. I know you've worked with it before but it does take a bit of getting used to.

    Here was the result of my second try on my plinth experimental piece. The mold was just particle board mummified in packing tape.

    1 Mummified Plinth Mold.JPG

    9 Success.JPG

    Last edited: Aug 31, 2017

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