I happen to have a nice large pottery kiln that I can bring up to 1100c . Looking at my historic test charts it takes 3 hours to go from 900c to 1100c+. I am wondering could I melt bronze in my large electric kiln. What is the long term effects of a graphite crucible in a kiln over hours while filled with bronze? Does anyone know?
You may achieve melt at 1100c (depending upon the bronze alloy) but not pouring temp......and it would take a very long time. My resistive electric furnace is basically a Kiln. I have an A10 clay graphite crucible that has over 100 heats in that furnace and other than fading from black to gray looks like the day I bought it. It's only seen aluminum service and I typically run the furnace at 1800-1900F. Initially there was some question about operating in air versus a reducing flame environment but that has not proven to be a problem in any way. I don't think the issue is whether the crucible can handle the bronze, moreover whether your kiln can reach satisfactory temperatures to pour bronze. Remember, you will likely have to target a pour temp at least 200-300F over melt temp. My heating coils are Kanthal A1 which has a maximum recommended operating temperature of 2600F. That seems enough to get you there but I suspect you may have longer melt times compared to fuel fired furnaces. Most NiCr elements (such as 80/20) would be in the 2200-2300F Max operating temps which may be marginal for bronze. I only melt aluminum in my electric so haven't had any reason to test the upper limits. Two caveats: The localized temperature in the heating element groove will likely be greater than the average temperature in the furnace. Operating resistive coils at/near limit can drastically reduce the life of the heating elements. Do you know the operating limits of the heating elements or refractory bricks in your Kiln? Best, Kelly
I had thought about using my kiln but did not want to open it hot. It is both tall and not designed for cold air quench. Kelly's is a top hat which pretty much lets the hot air stay around the coils as it is lifted off. I'd like to know if anyone has had a good experience melting in a pottery kiln.
I am rounding the bend on 700°c right now. I am doing just enough bronze to make one ingot. I'll let you know in a few hours how bad of an idea this is.
Started at 4:53pm, poured at 9:18pm @ 1118°c kiln temperature. I was just making about 2#'s of scrap into ingots, lots of impurities but it worked.
Looks hot A furnace is pretty easy to build if you're going to melt much. 4-1/2 hours cost how much in electricity?
Thanks, A furnace of some design or make is in my plans. This was just a whim. It costs about $1 an hour to run the kiln. ((220v*40amps)/1000)*.0969$= $0.85 an HOUR!
My electric furnace is 8.4kw but is insulated well enough when set at 1900F it only has a bout a 30% duty cycle. When it's at temperature it melts 10lbs of aluminum in about 20 minutes. I pay 8.5cents/kw-hr . If it was energized continuously it would take 71c/hr to run the furnace (that's closer to what is uses warming up on first melt) but on subsequent melts with duty cycle it's only 21c/hour. So the cost for a 20 minute 10lb melt is about 7 cents. On a whim I put a $15 imported power meter on my furnace. I thought it was just frill but it has turned out to be very useful because it continuously displays voltage, current, power, and totalizes energy consume. The current and voltage are good health indicators and another visual source that the coils have power applied. Electrics are clean cheap melting furnaces and great temp control with PiD and Thermocouple so can also be used to heat treat. They have somewhat slower melt times and are marginal for bronze but I wouldn't trade mine for what I use it for. Best, Kelly
WOW... Deja vu big time. I could have swore I saw this thread before. I trust you shut that sucker off before reaching in there right??
Turned off dials, flipped breaker and unplugged it. I don't want to know what two phases feals like while holding molten metal.
Good man. While wearing my aluminized space suit I started to reach in mine one time with it on to retrieve a ceramic shell... I caught myself before I got too far. Yeah I think I peed a little that day.
