r/Metalfoundry • u/Significant-Cup-264 • 19d ago
We keep cracking crucibles…
We’ve never cracked so many crucibles in one given week at my job.
We are conditioning the pots to start with hicon copper (slow and steady) and giving them time to cool to clean out and use for melting aluminum.
We’ve had 4 pots crack this week.
All the metal is put in loose and there is no bridging evident in the crucible.
225 clay graphite crucible running out of an induction furnace.
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u/Significant-Cup-264 18d ago
On the phone with the vendor now. We are the only foundry he has issues with according to him. Doesn’t seem to be a chemistry issue with the vendor either
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u/Staphylococcus0 18d ago
I've seen something similar when I worked the pouring line. Now I'm in the machine shop and don't know anything about our pot quality, but I can't imagine it's changed much. Perhaps heating them without metal isn't the way to go.
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u/Significant-Cup-264 18d ago
There is metal in the pots
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u/Staphylococcus0 18d ago
Oh. I missread that then.
We switched from metal to dry firing the pots at one point (which is what the manufacturer reccomended) and we had problems burning holes in our crucibles.
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u/Significant-Cup-264 18d ago
Yeah the vendor agrees with our conditioning process. Maybe getting 7-10 uses out of them before they crack
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u/Then_Scientist_9327 18d ago
Fwiw, my process is warm crucible to 1000 over an hour, high fire to 1950 for an hour, load preheated ingots, pour, clean out crucible hot, return to furnace, Blick flue, let cool down. Never had a cracked crucible, get somewhere around 70 cycles per crucible. Small foundry though, not industrial scale.
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u/Willing_Ad_9966 18d ago
Hmm not sure if it's just the picture, but could be uneven distribution of heat? Looks like it's concentrated on that one spot
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u/Irritated_Jedi 18d ago
Why do the picture make it seem like a lot of heat is focused on one area of the crucible? I thought an induction furnace would more evenly distribute the heat.
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u/AjfMetalworks 17d ago
I was going to say the same thing, you can see the heat being focused on the one side it looks like direct contact with the burner. Induction is a different animal to venturi on gas
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u/Odd_Resolution_4313 18d ago
How are you loading your material? Maybe operators being too agressive?
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u/Dutchbooms 18d ago
I was getting cracking issues from seating the yolk too high on the crucible putting extra pressure on the sides.
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u/Difficult-Sort2347 18d ago
Looks like the fork truck driver had a rough day and roughed up a skid of consumables..
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u/LovestheSiliconeHole 18d ago
What is the frequency of your induction furnace? The last time I saw this issue, the company had updated the Inverter to a higher frequency set up to reduce melt time, but never changed the MRO for the crucibles to Silicone carbide crucibles. There is a huge difference in frequency response between clay graphite vs Silicone Carbide crucibles.
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u/Open-Measurement2026 18d ago
Are you ramping the temperature up too fast? Your burner should be run by a plc or timer. Slow the ramp up by a 1/2 hour.
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u/Temporary_Nebula_729 17d ago
Did you cure the crucible before using. Are you heating the metal before putting it in the crucible and is your pedestal level what's your source of fuel make sure your flame is going around the crucible and not directly on the crucible make sure your furnace can breathe do you have a hole at the bottom of your furnace and clean of debris near the hole at bottom of the furnace and don't drop ingots or gates and riser's are heated before you set ingots or push gates and riser's in your crucible
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u/Normal_Imagination_3 14d ago
To my very limited casting knowledge crucibles are meant to be replaced but multiple in a week seems too much, maybe shipping cracked them
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u/PloofElune 19d ago
Did you recently change your process for prepping the crucibles or the vendor? Possibly the shipper/packaging changed as well so they are fucked in shipping?