The Shop > Metal Stuff
New lining for the iron furnace
RotarySMP:
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
vtsteam:
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:
tom osselton:
It’s almost amazing how fast it heats up with the blanket.
vtsteam:
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.
awemawson:
Can you set the burner in a block of fireclay to give it strength to the furnace outer shell. If it’s not too large the heat loss of not being Kaowool at that point will be minimal.
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