Is cast iron damaged by high heat?

My parents had a house fire in their home earlier this year. Pretty much a total loss. Except sitting in the piles of ashes, nails and door hinges, is their cast iron wood burning stove. Visually, it doesn’t look like it was damaged, but the fire was hot enough to melt their Calphalon pans.

Does anyone know if high heat, from a house fire, would cause damage to the metal of a cast iron wood stove? Is there any chance of being able to reuse the stove, when they rebuild, or do we risk the stove shattering/cracking/warping/etc.

I used to have a cast iron griddle. One morning I started an electric burner and put a skillet on to cook an omelette. I got the eggs, was mixing it up, flicked a drop of water in the skillet, hmm, not hot yet, and short story long, I had cranked the wrong burner. After maybe three minutes my cast iron griddle atop it cracked in half.

Granted, it wasn’t super thick. Granted, you can put a cast iron skillet in a fireplace fire to clean it. But I was shocked that an electric burner could crack cast iron in such a short period of time. Maybe I got a bad one? It sure was heavy.

I suspect the answer to your question has to do with how direct the heat was, the peak temperature, and other variables. Beyond that I’d be thinking not about the iron catastrophically failing but rather, possible CO issues or fire hazards. IOW, I’d get it tested before reinstalling it.

Cast iron can be damaged by high heat, but you’re going to have a devil of a time determining if the stove got hot enough to be damaged unless you try using it.

Calphalon is aluminum, which has a melting point of 663 C. Cast iron is… well, it’s iron of course, which has a melting point of 1538 C, which is considerably higher. In other words, it’s not that strange that a fire hot enough to melt aluminum would not visibly damage a cast iron stove.

Interesting question. In theory, you could have a fire hot enough to melt iron, which would certainly cause damage (the Chicago Historical Society has a few examples of what used to be boxes of nails from a hardware store that, after the 1871 fire, became odd little bricks of fused iron segments. Such high temperatures in a house fire would be extraordinary, but not entirely impossible.

I agree with Una that it may be impossible to know if the stove has been damaged without trying to use it. It may be perfectly OK. It may not. If there were non-iron components those may well be damaged.

cast iron can warp and crack. stoves can thin out with use in hot spots so can have temperature differences which can warp and crap.

build a small (so that if the stove is malfunctioning it won’t last long) smoky fire and look for leaks.

I suspect it was the DIFFERENCE in temperatures that cracked your griddle. By that, I mean the extremely localized heating from the electric burner, with a cold outside=bad news. Cast iron likes to be all one temperature, either all cold, or all hot (as in your throwing it into a fire to clean it). If it’s hot AND cold, the unequal expansion from the heat will break things. Especially if it’s cooled quickly.

I would bet that the woodburner of Tastes of Chocolate is perfectly fine. The cast iron parts of tractors (mostly made out of cast iron) can usually survive a barn fire, etc with no damage. It’s everything else that gets ruined.

Oh, and storytime…

My dad used to work at a cast iron foundry. They had a heat treating room for castings. I guess a new guy opened up the door one day while it was still hot, thus everything cooled off much quicker than it should have. The foundry subsequently received a call from the machine shop asking “What the !@#$ did you do to these castings!!!” because they were breaking all their tooling…the castings were too hard. At least that’s the story that I remember.

I hadn’t thought about it, but I suppose that could be another issue. The fire department pumped water onto the fire, so the stove may have been quenched, rather then cooling down slowly.

My thought is that
a) there aren’t a whole lot of moving parts to a cast-iron woodstove; and
b) it’s not going to be any hotter in use than it was during the house fire.

So, it’s hard to see how using it is going to make anything worse than it is now. So if there aren’t any cracks or breaks right now, and the door and flue work correctly now, I don’t think there’s any reason not to use it. Of course, I’d pay close attention the first time I built a fire, but I don’t see any reason it wouldn’t be salvageable.

I would think any quenching issues would cause breaks/cracks at the time. Heating usually only relieves stress.

Nope, same thing happened to mine. My wife put it on the burner and forgot about it. A few minutes later we heard a loud cracking noise. As was noted, it’s the difference in temperatures. Sort of like putting a hot glass in cold water.