I clean and inspect my crucibles before each melting session. Today while doing so I discovered I cracked my A10 during yesterday’s session. Too bad because I’ve been using it for two years and had well over 100 melts on it and was still in good shape. It would have been interesting to see how long I could have made it last. I think I broke it by charging it with a cold ingot. Those A356 ingots I have are big, nearly 4"x4" cross section. I cut them to shorter lengths in a horizontal band saw and they stand in the crucible ok but the four corners contact round bottom of the A10. With my electric furnace I don’t have a good way to preheat those big chunks of ingot so going forward I'll have to make sure I charge the bottom of the crucible with smaller pieces for the ingot to rest on to prevent it from expanding against the bottom basin or cut them up into smaller pieces. Bummer. Casualty of war! Already have another one on the way. Best, Kelly
No, FavoritesUSA, another eBay seller but I know both they and Jetstools are Morgan dealers. -Lot's of counterfeits on eBay. That's a possibility. Maybe place a smaller piece or bed of smaller pieces in the bottom for the big chunk to rest on. Some preheating couldn't hurt either. I took a closer look at the crucible. -Lot's of cracks. No wonder it was ringing any more. I’d say the possible causes: My original premise of expanding ingot lodging on the rounded bottom. -Maybe Maybe I froze a low temp melt by tossing in another chunk of ingot and it expanded upon heating. The first charge was a 6-7lb chunk. Then I added a ~1 ½-2lb (room temperature) chunk. Maybe it’s just age and repeated use and shock…..could be don’t think so As far as aging, it has lost most all of its glaze and the circled area below look like nit lines that may have been attacked by flux and/or metal contact. Aside from the cracks I think it's normal wear and tear. The walls are still pretty much at full thickness. I think it had a lot of life left in it. Best, Kelly
If it has heated up and cooled down a hundred times, it's had a good, long life in my book! Just the thermal movement on its own will eventually crack them without the charging.
I just realized that what I thought was the cracks in the crucible were actually marker lines. Now I see ...
It looks like the graphite has depleted: the chipped area on the rim is brown underneath with no sign of graphite, maybe it slowly burns off over time.
With the cracks eminating from the top It doesn't look like expansion of the ingot from the bottom, but what do I know.
That sucks. I'm always worried about that with my crucible. Perhaps it's time for a bigger one where ingots won't touch the walls and crack it while they expand? Be sure to give it a proper burial.
The dark black exterior is glaze. The interior of the new crucible is dull gray, and the others fade more and look more like clay after a couple melts. I don't know if graphite can/does precipitate out of the clay or not. Being an electric furnace duty, it most certainly lived life in an oxidizing environment. I removed that chip at the brim to have a look thinking along similar lines. I don't know what the interior wall of a new crucible looks like and am not anxious to find out! That's what made me think it may have been from a temporary/near freeze or thermal shock caused by adding a could chunk of ingot to the melt. Oh, I have bigger crucibles. The A10 is the smallest crucible in my Avatar. However, I use the A10 for 90% of my melts, at least so far. To be clear, if it's just run its course of life after all those melts, it doesn't owe me anything and I'm certainly satisfied with its service life. It went from ringing quite soundly with a light rap of a plastic mallet to a dull thud with all those cracks in 4/heats and one day's use.......and after all the previous melts, that just doesn't seem right to me. I'm just paying heed to try to insure the same thing doesn't (immediately) occur with the new one, which I received yesterday. Haven't tried out fit in my open ring shank yet. No burial yet. I'm going to keep it around for a while, but not for use. Best, Kelly
New A10 A little massaging with some heat and a hammer to tune up the fit of my open ring shank. Back in business with A10 pours. Best, Kelly
