Keg foundry furnace build

The keg build started in my propane burner build here: https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/propane-burner-build-the-mule/125823/page2/ But for TLDR I'll recap from the beginning here. 

Did a lot of research first before jumping in. Compressor and propane tanks, steel drums, kegs, fabricated shells etc.

Originally planned a 30 gal. grease drum furnace, I have one sitting in the shop. Research over the winter found a half keg may be best... and it is stainless, who don't like stainless.

After months of scouring CL and other sites w/ no results I found this half keg listed on CL... was only posted for 10 hours when I saw it. First call in and scored it two days later for $80. 1.5 hour drive. Seller was super nice and met me off the interstate to save me 30 minutes each way, no bartering, I woulda paid full price anyway. Keg has no dings, minor scratches on the beads from rolling it across the dock maybe once.

Pristine actually, too nice to cut up, in fact woulda made a cool man cave table all polished up w/ a beveled glass top. I take this as a sign from the gods of fire and metal that this score was meant to be.

Build time, let's cut 'er up.

Step one:

Depressure keg. Rag over ball check in tap flange, depress ball w/ large screwdriver to bleed off pressure.

Gushed quite a bit considering it was last used in 2002 at his sisters graduation party according to the seller. Spewed over a quart of beer out w/ considerable pressure yet after 15 years.

Funny tho, the beer didn't even smell stale. 

Next: removing the lock ring, kinda stubborn.

Shoot w/ WD, rubber hammer, grind down old screw driver to fit the slots and finesse the motherberkeleyer out.

Calculated the lid cut to have a minimum 3" refractory thickness. Max thick w/ the dome of the lid will be 4" at flue out.

Cut w/ Milwaukee 4-1/2" angle grinder w/ Dewalt cut off wheel. Pretty easy cuttin'... edges dressed w/ flap wheel, drum and wire wheel.

There goes my tap room table.

.125" x 1" 304 SS flat, rolled on Pexto slip rolls to 15.5" dia. Keg walls and lid sections at cut lines are pretty stout, just adding reinforcement. SS rivets to attach.

1/8" X 1" 304 SS flat is now attached to the keg lid and bottom w/ SS 3/16" X .250" grip pop rivets, 3" on centers. I left 3/16" stickout of the flat above the keg wall. 

Used a 2-1/4" hole saw cut out for the guide plug in the lid to cut the flue vent.

2X4 for the cutout plug.

Popped the cutout from the hole saw and made an arbor from a long 1/4" bolt w/ hex head cut off for use w/ die grinder. Welded a washer on the bolt shaft, cinched w/ washer and nut, sanded down to fit the ID of the dip tube flange. Hammer fit.

Spot on, hammered in.

Milwaukee 2-1/2" hole saw, Milwaukee 1/2" Magnum drill FTW... nice n slow.

Later ground out the 2-1/2" vent to 3"

Cardboard template made from beer box. 1/8" pilot drill and 1-1/4" hole saw to fit 1" PVC pipe center guide in keg bottom. This will later be cast in as a drain. 

Stripped the paint w/ 3M purple pad on pneumatic disc sander, polished w/ compound and wool cutting pad. Not necessary but cleaned up nice.

Rods for securing refractory.

1" Inswool was a last minute decision. Better to have than not. Glued in w/ Clearco 444 spray adhesive. Similar installation on the keg base.

Ordered Kastolite 30 LI Plus from local refractory dealer. Fresh born on date. 

Drier mix. Rammed mix w/ 2X2 on the inner and outer circumferences but not over the wool. Old pneumatic jitterbug sander used as table shaker to remove entrained air, it worked quite well. 

1" PVC pipe guide to hold center. Mineralac and beam clamp FTW. Ran outta 1/4" all thread, so compromise. This would prove to hold the center well.

Surfaces covered w/ plastic, air dry at 60°F for 36 hours. Cooler nights brought in halogen work lights to maintain temps. Gradually raised temps 60-70-80 degrees w/ moving the lamps closer. Held 95-100° for 48 hours w/ lamps (90-110°F recommended). 

October temps (2017) went from August to November overnight. Needed two more weeks of good temps to finish walls, cure and dry out w/ burner but temps never came back. Keg and lid moved inside house for the winter. 

10" form tube was used for bore mold. Tubes come shipped nested in set of four, so 10" is nominal size. Chose a 9.5" tube as best for use w/ Salamander A6, A8 nad A10 clay graphite crucibles. 

Tube cut to height. An Allpax circle gasket cutter was used to cut cardboard reinforcement discs for inside the tube. We used this Allpax for cutting flange gaskets in pipe fitting and boiler plant work. Nice piece. 

Reamed a piece of 1" pipe on the pipe machine and sharpened the bore to a knife like edge. Welded a steel flange on for use in the shop press.

Took the best fitting disc and used for a template. Hammering the punch would just bounce and not hold center. Shop press worked well. Ka-chunk, good cut. The edge on the cut out punch would only last for about 3 punches before needing resharpened.

Calculated placement of tuyere hole above furnace floor on the keg wall. Hole saw to start, grind to fit.

Fit the 1" pipe guide to the drain hole. Glue gun in cardboard discs. Fit tuyere pipe mold to form tube, hole saw to start but eyeball to finish. 

Glue gunned in cardboard discs about every two inches in height. Doubled on bottom and top of form.

Form tube all glued up. Sanded and scuffed the outside of tube to remove any high spots. Coated the outer tube walls and cardboard discs with two applications of Bondo fiberglass resin. Light block sanding after to level.

Lined keg wall with Inswool, adhered with adhesive spray. 1.5" total thickness.

Was going to just weight the top of form tube w/ brake rotors or drums to hold down. I came up w/ square tube and all thread at last minute. Was able to keep the form centered better in the keg bore. Form tube outer to keg wall was all equal in N, S, and E but W was +3/32". Not too shabby.

Rammed Kastolite in, did moderate shake-out with the Jitterbug table shaker. Glad I didn't overdo it tho, as I found later. No matter how dry you think the mix is there's still a lotta water coming out. Trowel it off, add sifted Kastolite for finer material to the wet top

Original plan was a 2" DOM pipe form for tuyere hole. Last minute change to 1-1/2" pipe as I'm not running the larger coupling flare on the burner hot end. The 3/4" straight SS coupling will work fine. 1-1/2" pipe was wrapped w/ aluminum foil for easy removal.

Cover and let dry three full days. 

Remove 1" centering pipe. Removing the cardboard discs was easy. Slice w/ box cutter and pull out, kinda like opening a cardboard shipping box.

Tuyere form pipe removal was easy.

There was no buckling in of the form tube or any water or refractory intrusion inside the form.

Once the discs were removed just turn the form tube in on itself and remove. 

Touched up any surface porosity w/ sifted refractory and radiused the bore to floor.

Started the heated dry out w/ lamp base I made up. 40, 60, 100, 150, 200 to 300W bulbs. Usually almost one day at a time/ bulb. Monitored the bore temp w/ IR temp gun.

Used an old cart I had fabbed years ago for my old 30 gal. grease drum parts washer. Was going to make a flange to mount the burner to the keg. This pedestal is actually better for positioning. 

Tuned the burner down for low fire to start curing w/ a 0.023 MIG tip orifice, had to choke the primary air way down. That ain't a lot of primary air.

Slow and easy.

Bought a HF DVOM w/ thermocouple probe to monitor temp. It worked once in testing around the house then failed, returned it for refund. 

Then bought a Skutt digital kiln pyrometer, why piss around. Tried to hold the temp to 2-300°F/ hour increase. Initially temp rose faster but later stabilized. 

The Skutt reads up to 2500°F, it reached that after 6.5 hours.

I let the burner run a full eight hours, so likely hit 2700° or more from what I was seeing w/ my burner adjustments.

She got nice n cherry.

Let cool some, cleanup outside. Wrapped the furnace in a HF welding blanket and let cool in the shop overnight. IR temp gun read 100° bore temp next day.

But it was time to put it away for the 2019 season. Still had winter prep to do around the house. It lived in the house over the winter. 

All work until this year has been part time. I chose to retire in July of 2020, so this is a retirement project now. Had to get caught up on necessary projects at Dad's house and mine. Trying to put more time in now.

Had to replace the wheels and tires on the hand cart to safely move the keg to the shop before starting any keg work. Tube tires were absolute crap. Ordered semi-pneumatic tire/ wheel set online in same size. Had to cut off axle, sleeve axle to widen for new wheels and weld back in. Paint to match. While still working my shifts, this turned into a week long job, ugh. Wonder where the time goes. Cart is stout now.

Plywood on the cart got charred from the heat.

Cobbled some .040" aluminum and formed around drain hole.

Sprayed adhesive on cut offs of Inswool and glued to the aluminum.

Repainted the cart frame, added some angle to center the keg. Why I painted the plywood, I dunno. Paint was sitting on my bench callin' my name.

Decision 2020: ..... no, not that one

Coat the refractory walls with Satanite or ITC 100HT or leave it alone. Heard good things about the ITC as a reflective coating, reducing fuel use and heat up time so I went with that.

At $50/ pint ITC100 ain't cheap. 1 pint covered all refractory in the keg including lid, vent, drain and tuyere hole. Mix is 2 parts ITC to 1 part water. Mix well. I applied it w/ a  1-1/2" chip brush. It went on like a heavy latex paint. That brush did a 4x6" area smoothly. Try to stretch it or coat over top previously applied ITC and it would ball up. 

Let dry several days, no hurry. Come the weekend I started warming w/ the lamps again, hit 180° wall temp and decided to fire w/ the burner. Low fire w/ the 0.023 MIG tip, air choked down like previously shown. No pyrometer tho. Gradually increased starting gas pressure from 2 psi up to 10 over 2.5 hours. Got nice n cherry and called it good.

Result

Pretty pleased with the outcome. Furnace is now ready for use.

Did some tests for making plinths. Not satisfied with the results yet using Kastolite 30. Tested several types of containers also.

Best mold I found is a cut down 6" PVC coupling, slotted for release, breeze clamp, Polycarbonate sheet base and RTV sealer/ adhesive. Good clean surfaces and releases easily. Reusable too. 

Bought some 2800° IFB's to cut down also. 

Welded up some ingot trays from 1/8 x 2" angle, 1/4 x 1" and 1/4 x 1-1/2" flat stock. 

I have the steel in house for making crucible tongs and pouring shank. Rather use slip rolls for rolling to diameter. Second choice is 4" pipe or nipple for the smaller crucible and 5" pipe or nipple for larger crucibles and bending around w/ AO heat. Being retired now I don't have access to these materials or tools anymore . I'll scrounge around for pipe cutoffs in the mean time. 

Have Salamander clay graphite crucibles in A6, A8 and A10. 

Melt and pour can still happen this year but gotta get prepped for winter right now in the northeast. 

I'll leave it here, for now.

Those last lines were a bit of a gut punch. 

You have everything but the tools to grab the crucible and you're going to stop there?  Its like doing a frame off restoration of a car, firing the engine up and breaking in the cam, then not going for a test drive.

I get that other things take precedent, but still.  Oof.

cool!

This is very cool. I've been wanting a furnace to forge metal and a converted keg seems incredibly cool.

New addition for pattern making:

CR-10 4S, 16 X 16 X 16" build space. Will update the Creality firmware, add Swiss all metal hot end, print strain reliefs and thumb screw bed adjusters etc. Add LED lights because kitchen light sucks. 

It assembled well, I'm rather pleased so far. Yet to run it.

Gonna order more PLA and start playing. 3D design software. Gonna try some Mizzou for pouring in mold for the plinth. Kastolite would work but not ideal. Tools to be fabricated yet, probably in the spring. Shop is shut now.

I'd recommend you get rid of the binder clips and get some of these https://smile.amazon.com/Printer-Picture-Spring-26mmx14mm-1inchx0-55Inch/dp/B088Q63WNB/ref=sr_1_1?dchild=1&keywords=bed+clips+printer&qid=1607230218&sr=8-1

Ends up giving you more room to use your bed, and they don't snag on crap like the binder clips do

Doing test pieces now.

Doggie was the Creality test piece on file, which came out great. The others were created or downloaded into TinkerCAD for editing.  Two of the bases have 10° draft on the outer edges (3°-5° minimal recommended). Text, GM and Chevy bowtie have no draft, that can be solved with wood filler. 

TinkerCAD has limited text options. Easy button for text may be buying printed text sets with draft built in and gluing to the base as suggested on the foundry forum. 

Been dabbling in FreeCAD also, but ultimately will go to Fusion 360. TinkerCAD has been doing everything I need right now.

Bases are .250" thick, to save material and print time I may glue the featured top to MDF and sand a 5° draft into the MDF edges. 

Getting the printer dialed in also. Bed leveling, adhesion, Cura print settings. Increased bed and extruder temps and lowered print speed. Getting better all the time. 

Next step is going to a larger footprint. 8X8 or 10X10 would be a good sized plaque.

May update the propane burner to forced induction down the road. One step at a time. 

It's good winter work.