Furnace

[wierdscience]

Well I'm a doin 'it now me and a buddy have gone ahead and built a coupola furnace ala Steve Chastain we haven't lined it yet but we are rapidly getting there.My question is the books I have don't get into any real detail on the subject of charging/firing the thing any advice would be appreciated other than the usual fire ext.,body armor,911 number posted on wall next to the number for the nearest burn unit,five acre alovera farm,etc,etc,

[TONY R]

If your using fire brick to line it make sure you let it cure for atleast aweek or the bricks will explode!!! After that use low long term heat to help cure the fire brick,
GOOD LUCK TONY

<font face="Verdana, Arial" size="2">Originally posted by wierdscience:
Well I'm a doin 'it now me and a buddy have gone ahead and built a coupola furnace ala Steve Chastain we haven't lined it yet but we are rapidly getting there.My question is the books I have don't get into any real detail on the subject of charging/firing the thing any advice would be appreciated other than the usual fire ext.,body armor,911 number posted on wall next to the number for the nearest burn unit,five acre alovera farm,etc,etc,</font>

[SJorgensen]

I built a forge and I used refractory concrete. It really did work out pretty well except that I did get some cracks. I think that my next one will be built in the same way, except that I will form it in two layers about 1 1/2" thick and I will scribe it so that it cracks where I want it to. I did find the breakin process to be very important. There is a surprising amount of water in the cured refractory. It will steam for hours. Plan for the cracks for long life.
Spence

[Del]

How about giving us a report after you have fired.I have been toying with the idea of stepping up to a bigger hotter furnace. That looks like the way to go. Good luck and keep us posted.

[CCWKen]

I used refractory in mine too. The main thing to do is start out low-temp and let it cook for a couple of days. I used a hot plate set on it's lowest setting. After that, keep uping the temp for days at a time. On the first fire, keep it low also. I still had a little steam on the first fire. Fire it up on lowest heat for a couple of hours then let it set for a day. Do this for a couple of three or four days before really pouring on the heat. Don't get in a hury to "use" the furnace. I have one hair-line crack in mine but that was after a cast iron melt with a less than perfect crucible.

And one more thing... Always, Always, ALWAYS! use DRY sand under your safety outlet. Molten iron hitting even a blade of grass will explode.

[WJHartson]

Curing refractory can be tricky but if you follow the heatup curing instructions for the produce you useing the result will be very good.

As a general rule, when you cure refractory you have to dry out all of the free water first. This is done by raising the temperature slowly, start at about 1oo degrees and raise the temperature 50 degrees at a time and holding the temperature for a couple of hours at each setting until you reach 2oo degrees and holding it there until no more steam or weeping is seen. Depending on what refractory you are using and the thickness will determine the length of time for the free water to dry out.

Once the free water is gone you will now have to get the chemically bound water out. This is accomplished by raising the temperature about 50 degrees at a time and holding it there for about an hour. Continue raising the temperature until you get to about 1500 degrees. By letting the temperature soak in you will reduce the amount of cracking in the refractory. During the curing process you have to have a vent to let the water out of the furnace.

If you do get cracks, there is a product called fiberfrax, a white ceramic material that looks like fiberglass insulation, that you can stuff in the cracks to seal them up. It will burn out over time and will have to be replaced.

Slow even heat rise with soaking time is the key to curing refractory. The same is also true of refractory brick.

Hope this helps. Good luck with your project.

Joe

[darryl]

I know nothing about the furnace you're building, but the 5 acre aloe-vera farm strikes my fancy. Could I just come over and walk around in it, if I'm feeling not so good?

[CCWKen]

Gee Darryl, that alovera stuff will take over the place if you don't keep it thinned out. We burn that stuff off like cactus down here. Can't get rid of it!

[darryl]

Well, I didn't think it would be a weed! Shows what I know about agrkultcher. I did read somewhere about introduced crops that turned out to be hard to control, down your way. I'm wondering now, are the africanized honey bees there, yet, from that accidental release, in south america?

[wierdscience]

Wait a minute are you guys talking crucible or coupola furnace?I'm talking coupola you know iron and coke in a fireclay liner 3800F refractory is to fragile I had to use a home brew formula which involved mixing the clay grog dry and under heat to cook as much off as possible then use alcohol for the binder/wetting agent and ramming up inside of the shell and allowing it to gas off for a week before firing slowly to a hard glassified glaze.This sucker is suposed to be good for 500# an hour!I have done the crucible casting before but never anything with solid fuel what I am hoping to find out are some of the unknowns involved in charging the coke and scrap from a cold start.As well as air flow up thruogh the fuel/metal mass and how different loadings affect it.