Cast Iron Damage

[cmcramer]

How seriously is cast iron damaged by overfiring a woodstove until the iron glows red?
Is the nature of that damage "warped" cast iron? Anything else?
Is this damage cumulative over time? That is, does each instance of overfiring add up to equal "damage" some day?
How urgent is the need to cool off the fire and eliminate glowing red cast iron?
Does more time at glowing red temps = more damage?
How significant is the difference between dull red and bright, cherry red?

My stove got away from me last night.....Thanks for any advice.

 

[webbie]

It depends.

In general, cast iron can take the heat, even glowing once in a while. Enamel can tend to have problems at very high temps.

Many cracks in cast are not the result of too much heat, but of poor designs - castings that are too large, or hot in one area and cooler in another.

https://www.hearth.com/econtent/index.php/wiki/Temperature_when_metal_glows_red/

shows some of the temps involved.

Cherry red seems to be WAY above the temps that stoves are built to take, whereas a very dull red or just visible red is something that I have seen quite a few times.

All in all, though, the main thing is to inspect the stove and parts that got too hot and see if anything has physically changed. If not, chances are that everything is ok.

To answer some of the others.....

A lot depends on the exact stove and fuel. A coal stove will tend to be cumulative, because the sulfur from the coal and other chemicals starts to attack the metal. With a wood stove this is less likely. Cast iron which has been hot a number of times will often have an red-orange color when inspected....but I have seen casting that were very thick (baffles, for instance) have this color with no ill effects.

As far as cool down, thermal shock is a no-no, so closing off the air and perhaps aiming a room fan at the unit would probably be the best ways to cool off a unit. Cooling down the room with an open window or door will help also.

So, all in all, you are correct in that you would likely see warped or cracked iron if any major harm was done.

 

[crazy_dan]

I have seen many cast iron stoves glow it is the cheap ones that you have to be the most worried about. cool it down slow or it will crack cast iron does not like big fast temp changes. and as with any thing cheack it out real good when it cools.

 

[DriftWood]

Cast iron is made out of iron oar in Brazil with charcoal and air. Iron will melt if a jet of air blows into HOT coals with iron near it. Think ash clean out grate with no seal.