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Molten Steel

Huntsman said:
rwguinn and GlennB:

Steel is formed at the plastic temperature, but the iron has to be smelted from the ore before this. It has to be melted (the iron at least).

I'm with default on this one, although on further research it seems we're both a little right :)

There is a maximum temeprature, but what we need is the adiabetic temperature...not the burn temp in open air.

A good resource:

http://www.doctorfire.com/flametmp.html



ANd a note on house fires:



So, it's still plausible that a well-insulated area, fed by wood fires (or plastic, although we'd need an adiabetic temp on that as well) could melt aluminum, and quite feasibly iron and steel.
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Again, It doesn't matter. If the flame temperature-or oven temperature-or whatthehe!!ever temeperature is not as high as or higher than the melting temperature, it will not melt. Period.
you cannot melt ice in a 31 degree oven. You cannot melt steel in a 1000 degree c oven.(ETA--aluminum, yes!)
As far as temperatures climbing over time in a house (or other structural) fire, that is where the energy goes--the overall temperature will continue to climb to the point where equilibrium is reached.
This is a case where the 1st and 2nd law of thermodynamics are the rulers of the roost.
Heat always flows from hot to cold. When a body has reached the same temperature as its surroundings, that is as hot as it gets.

As for your first point, you are being ridiculously pedantic.. Yes, iron must be melted to form steel. To form an ingot, you melt it.
To forge that ingot into a sword, or wrench, or whatever, you heat it to the plastic region, not melting point. Hitting molten steel with a hammer is akin to sticking a finger in a live light socket--you only do it intentionally one time.
 
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Huntsman said:
......

So, it's still plausible that a well-insulated area, fed by wood fires (or plastic, although we'd need an adiabetic temp on that as well) could melt aluminum, and quite feasibly iron and steel.
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Thanks for that Huntsman. Again, my schoolboy science is not quite up to scratch in these much more complex situations. Adiabatic conditions (as I understand it) would mean that the maximum possible temperature would be achieved not by the fuel itself (e.g. wood) but by the component of the fuel that can achieve the highest temperature (i.e. the carbon within the wood). Thus the adiabatic temperatures for wood and carbon would be nearly identical (according to doctorfire. From its explanation I don't understand why they wouldn't be exactly the same, but whatever...)

Some more from doctorfire:

"these <adiabatic> temperatures would be achieved in a (fictional) combustion system where there were no losses"
and
"These temperatures are vastly higher than what any thermocouple inserted into a building fire will register!"

In this respect, the rubble of WTC was no longer a conventional "building fire". It was smouldering for weeks, slowly consuming the huge amounts of hydrocarbon fuel (paper,carpet,plastic etc) that came down in the collapse. Does this get us closer to adiabatic conditions than the well-ventilated original building fire? It looks like it, but that's just more guesswork.

This stuff hurts my brain sometimes. I was politely conversing on a UK firefighters forum a while back. Think I'll go over there and ask ;)

regards
 
rwguinn said:
Again, It doesn't matter. If the flame temperature-or oven temperature-or whatthehe!!ever temeperature is not as high as or higher than the melting temperature, it will not melt. Period.
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I'll explain my feeble understanding of this situation, and more knowledgeable people here can show me where I'm going wrong.

The "flame temperature" is what it is, because it's an equilibrium of the energy added by combustion of the fuel, and how fast that energy is radiated/conducted to the surrounding air. However, this necessarily makes some assumptions about the characteristics of the surroundings and how fast they can sink the heat produced. For most situations, it's a pretty good approximation to say that a flame from a certain fuel has a certain temperature.

But not necessarily in an underground fire, whose characteristics are a) a high degree of insulation, and b) combustion rate is limited by the availability of oxygen.

Consider the thought experiment of placing a fuel source in a very well insulated environment, heating it up to combustion temperature to start the process rolling, and then having a knob that varies how much oxygen enters the system.

There will be some low amount of oxygen flow, below which the equilibrium of the heat lost to the surroundings, and the heat generated by combustion, would allow the fuel's temperature to drop below what's required for combustion, and it would stop.

But as oxygen flow increases, I don't see what would constrain the temperature of the fuel to the regular open-air flame temperature. As long as there is enough oxygen available, more heat will be produced, and if that heat can't escape fast enough, the temperature will climb to high levels.
 
rwguinn said:
As far as temperatures climbing over time in a house (or other structural) fire, that is where the energy goes--the overall temperature will continue to climb to the point where equilibrium is reached.
This is a case where the 1st and 2nd law of thermodynamics are the rulers of the roost.
Heat always flows from hot to cold. When a body has reached the same temperature as its surroundings, that is as hot as it gets.
Click to expand...

Well that's pretty much what I was saying, although you worded it more clearly. If the heat energy produced can't escape, then the temperature continues to rise.

You are correct that there are maximums, though, which I referred to in the website I referenced. I didn't know that, and do know. But the melting points for steel (right around 1370 C, actually higher for iron at 1510 C) mean that even a wood fire could reach this temp under well-insulated conditions.

As for your first point, you are being ridiculously pedantic.. Yes, iron must be melted to form steel. To form an ingot, you melt it.
To forge that ingot into a sword, or wrench, or whatever, you heat it to the plastic region, not melting point. Hitting molten steel with a hammer is akin to sticking a finger in a live light socket--you only do it intentionally one time.
Click to expand...

*sigh*. No, not pedantic, and sorry if it came out that way. I was just clarifying the point I was making...that even wood fires can melt iron and steel. While forging was a poor example, smelting fits, and is done in order to forge.
 
Huntsman said:
Well that's pretty much what I was saying, although you worded it more clearly. If the heat energy produced can't escape, then the temperature continues to rise.

You are correct that there are maximums, though, which I referred to in the website I referenced. I didn't know that, and do know. But the melting points for steel (right around 1370 C, actually higher for iron at 1510 C) mean that even a wood fire could reach this temp under well-insulated conditions.



*sigh*. No, not pedantic, and sorry if it came out that way. I was just clarifying the point I was making...that even wood fires can melt iron and steel. While forging was a poor example, smelting fits, and is done in order to forge.
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under well insulated conditions, Yes--but please note--virtually all smelters use a forced draft burn to get the temperature high enough. In fact, I cannot think of any that don't.
I use a coal-fired forge with a hand-cranked blower on it. To get the fire hot enough to weld mild steel, it takes a really, really heavy and quick hand on the crank.
Even with Natural gas, propane, whatever, you need a much, much leaner burn than free air will give you--so you inject additional oxygen by forcing air in at a higher pressure--you blow on the fire!
 
TruthSeeker1234 said:
....Fire experts have said they have never seen molten metal after fires....
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I assume you are talking about metal that has melted and then solidified after a fire.

I wouldn't call myself a"Fire expert", but I did spend nineteen years performing fire-resistance tests, at an average of about two a week. A great number of those were on fire-resisting doors. Typically, after a half hour test, where the test furnace temperature reaches about 840 C, the door handles on the fire exposed side would be a solidified lump on the floor of the test chamber. The melted and solidified door furniture would be aluminium. The steel parts were still in position on the door, although in a sorry state, but not melted.

Dave
 
ok, world--
Huntsman and I have PM'ed this--and we agree that we are basing our positions on different assumptions. so, while I would be surprised to find molten steel under the rubble of a fire such as at the WTC, I would not be shocked if it were, whereas Huntsman would be mildly surprised if it were not found, but not shocked.

Did I get that right, Huntsman?:D
[/derail] we now return you to your regularly scheduled Conspiracy theory
 
Eh, more or less.

I wouldn't expect it to be there, but wouldn't be suprised to find it :) Call me 50/50.

I was basing my assumptions on a very low rate of heat loss and low rate of production, while rwguinn was basing his on a higher rate of heat loss, thus needing a higher rate of heat production (difficult without additional oxygen).

So we agree on everything except, well, most of the details :) But come to a close enough conclusion to agree :D
 
In short. There were unground(debris) fires after the collapse. The temp of those fires and the effects they had upon the debris has nothing to do with anything about the collapse..
 
Crazy Chainsaw said:
Insulation still absorbs heat it is just not good at it, so the heat is still conducted away.
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so your saying the insulator becomes a worse insulator if heat is coming in too fast?

im saying the insulation can conduct X amount of heat away in Y amount of time, if the fire is producing X+1 heat in Y time, where does the 1 go?
 
http://www.unexplained-mysteries.com/forum/index.php?showtopic=78463

On a couple of different threads, several of the CTists kept harping over and over about how TK and I hadn't addressed their molten metal point; practically drooling that since we were "dodging" it that it must be a smoking gun. So, I spun off a thread to address only that point (did the same thing with the UL steel) and asked them to present why it supported their claims.

98 views. 3 replies commenting that it doesn't support their CD claim. 0 replies explaining how it would support the CD claim.
 
defaultdotxbe said:
so your saying the insulator becomes a worse insulator if heat is coming in too fast?

im saying the insulation can conduct X amount of heat away in Y amount of time, if the fire is producing X+1 heat in Y time, where does the 1 go?
Click to expand...

The bottom line is that (if I read it correctly) the temperature of the fire can't exceed the maximum combustion temperature of the "hottest burning" component of the fuel. In this case the adiabatic - or "perfect burning" - scenario for hydrocarbon fuel is approx 2000°C. Definitely hot enough to melt iron.

Your calculation (X,Y,+1 etc) above falls down because the equations are wrong - X is variable, depending on the temperature difference and conductivity of the materials. In the extreme case the insulation would stop conducting completely and just melt/ignite (school science - forgive me)

Let's take a very extreme case to illustrate. A piece of steel in a pan of boiling water that's incredibly well insulated with foam + rockwool + whatever. Keep it boiling for weeks. It will never melt. Try it. If it melts claim Randi's $1mill. ;)
 
GlennB said:
The bottom line is that (if I read it correctly) the temperature of the fire can't exceed the maximum combustion temperature of the "hottest burning" component of the fuel. In this case the adiabatic - or "perfect burning" - scenario for hydrocarbon fuel is approx 2000°C. Definitely hot enough to melt iron.

Your calculation (X,Y,+1 etc) above falls down because the equations are wrong - X is variable, depending on the temperature difference and conductivity of the materials. In the extreme case the insulation would stop conducting completely and just melt/ignite (school science - forgive me)

Let's take a very extreme case to illustrate. A piece of steel in a pan of boiling water that's incredibly well insulated with foam + rockwool + whatever. Keep it boiling for weeks. It will never melt. Try it. If it melts claim Randi's $1mill. ;)
Click to expand...

Just a thought, but in your boiling water example, if it is boiling, that means it is open to the air and the heat energy being put in to the water is being lost through the steam. If the piece of steel were in a sealed container of water that was infinitely strong and perfectly insulated and energy was added to the water to raise the temp of the water, what would the long term effects on the steel be?
 
defaultdotxbe said:
so your saying the insulator becomes a worse insulator if heat is coming in too fast?

im saying the insulation can conduct X amount of heat away in Y amount of time, if the fire is producing X+1 heat in Y time, where does the 1 go?
Click to expand...


Heat is only inferred radiation all materials react to it to some degree, Insulation works by being non conductive but eventually the Insulation would absorb heat and pass it to a cooler source itself.
That is the reason for double insulation layered tiles on the Space shuttle
The first tile passes the heat on to the second, the second prevents the heat from reaching the skin of the shuttle.
Insulation is rated for its resistance to conduct heat, but it still is effected, by it, and would over time heat up and release that heat to a cooler surface.
You can not insulate a fire 100 percent and have the heat build because much of the energy is lost to the surroundings no matter what they are.
All you can do is slow the flow of heat from hot to cool, that is it.
 
GlennB said:
In the extreme case the insulation would stop conducting completely and just melt/ignite (school science - forgive me)
Click to expand...

well assumign the insulation is gypsum it wouldnt melt, its melting poitn if higher than steel

but essentially what your saying is the resistance to heat would break down and it would begin to conduct heat more rapidly, that makes sense
 
Crazy Chainsaw said:
Heat is only inferred radiation all materials react to it to some degree, Insulation works by being non conductive but eventually the Insulation would absorb heat and pass it to a cooler source itself.
Click to expand...

No it isn't. Heat is a kind of phonon not photon
 
Arkan_Wolfshade said:
Just a thought, but in your boiling water example, if it is boiling, that means it is open to the air and the heat energy being put in to the water is being lost through the steam. If the piece of steel were in a sealed container of water that was infinitely strong and perfectly insulated and energy was added to the water to raise the temp of the water, what would the long term effects on the steel be?
Click to expand...

Ah, well there we might have an 'infinitely strong' container with 'perfect' insulation (whatever they are) , but with wires or pipes or something to get the energy in, which makes the perfection of the insulation a tricky business, never mind any melting of the energy-delivery system.

(Only kidding)

As I understand it your scenario would be the adiabatic model. If so, the medium for conducting the heat to the steel would be irrelevant. Water, sawdust, My Litttle Pony, whatever. The steel would reach the temperature of the fuel, as long as the fuel source itself was within the perfect insulation.

I fear the The Clausius-Clapeyron Equation might come into this, but it hurt me to even see it at :
<add stuff> theory.phy.umist.ac.uk/~judith/stat_therm/node44.html

May I stress "as I understand this"

best regards

Glenn
 
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