New lining for the iron furnace

[tom osselton]

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. I’m going to have to build a oil burner I’m still using propane.

[vtsteam]

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.

[vtsteam]

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?

[ironman]

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.

[vtsteam]

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.

[ironman]

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.

[vtsteam]

I've received some Satanite, and will be trying it out.

[vtsteam]

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:

[vtsteam]

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:

[tom osselton]

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 I’ve never had a problem with it so far mind you I’ve only done alu & brass so far.

[vtsteam]

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.

[tom osselton]

I was thinking that too maybe I’ll pick up another stainless beer keg or tig some banding around it to extend it down if it’s a problem.

[vtsteam]

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.

[tom osselton]

Interesting maybe that “ dark brown glaze “ is the reason you saw a difference in melting times.

[vtsteam]

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....

[vtsteam]

 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.

[tom osselton]

It looks great on the outside it will be interesting to see if it’s inclusion free when you get around to it.

[vtsteam]

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.

[tom osselton]

Excellent looking piece you’ll have to get busy stocking up on sizes now for the winter months.

[vtsteam]

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...

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.