1. Mick West

    Mick West Administrator Staff Member

    It's hard to keep track of the various temperatures involved in discussions around 9/11. So I made the above chart. It's a work in progress, so corrections and suggestions are much appreciated.


    Melting points of Lead, Aluminum, and Steel: https://www.engineeringtoolbox.com/melting-temperature-metals-d_860.html

    "Soft" temperature of steel: https://en.wikipedia.org/wiki/Forging_temperature
    NatGeo Pit Fire: National Geographic Science & Conspiracy Part 3 (5:56)

    Molten steel image: https://commons.wikimedia.org/wiki/File:Scunthorpe_Molten_Steel.jpg

    Temperature colors (scale on left) https://en.wikipedia.org/wiki/Red_heat
    I used the colors in the illustration there to create a photoshop scale between 550°C and 1300°C, then did white above, and a slight fade down to grey below.

    Hydrocarbon fire range of 800°C-1200°C, various. Common temp cited for house fires is 1100°C, but range is more.

    Strength reduction in steel - various, this is a topic in itself. There's a variety of graphs of this, and it varies between steel types and there's a different between yield strength and compressive strength.

    (Diagrams from Brockenbrough and Merritt’s Structural Steel Designer’s Handbook.)

    The "50% at 1200°F/650°C" actually seems a bit high a temperature, but it's a conservative round number.

    Attached Files:

    Last edited: Nov 10, 2018
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  2. Mick West

    Mick West Administrator Staff Member

    Might want to do more detail on "Hydrocarbon Fires". There's quite a range possible. House fires, Bonfires, burning paper, wildfires. I currently have it at 800°C to 1200°C

    This video shows peak temperatures of 850°C (1562°F) in a simple forest fire

    Source: https://www.youtube.com/watch?v=zvPa_yEEd4E

    National Resources Canada says:
  3. Mick West

    Mick West Administrator Staff Member

  4. Oystein

    Oystein Active Member

    An ordinary but undisturbed, well-ventilated candle on your dinner table reaches, so I remember having read, something like 1400 °C. You know, the blue (and actually partially invisible) center of the flame. But that goes for a small volume of low-density gas (and plasma?) and represents pretty little heat. You can move your finger through that flame and not get burned - and any disturbance gets the temperature down drastically.
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  5. Mick West

    Mick West Administrator Staff Member

    Almost hot enough to melt steel.

    One thing people miss here is the speed at which yellow hot steel cools down in a situation where only part of it is heated. If you hold some steel wire in a candle you might get it red hot, but the instant the heat wavers the temperature will plummet. I've seen this when heating a temperature probe with a blowtorch. The flame of the torch is theoretically over 2,000°C. Full blast on the temperature probe can heat it up to 1150°C, but it drops very rapidly, especially if in contract with a larger piece of metal. See: https://www.metabunk.org/posts/219926/
  6. Tomi

    Tomi Member

    I think you should add some of the measures temperatures of the pile and some of the temperatures measured in a furnace. Since the pile was a big furnace
  7. Mick West

    Mick West Administrator Staff Member

    Well, it was a big pile, with some fires burning in it, and some areas that might have acted like furnaces when the air went through them right at some time.

    I think there's a danger is seeking explanations for things like "molten steel" or "high" temperatures, when there's no real evidence that those things existed. There's absolutely zero physical evidence of "large pools of molten steel"

    What were the temperatures measured in the pile, and how were they measured? Were they measuring the temperature of solid matter in the pile or the temperature of flames/gas?

    NIST discusses various temperature points:
    And discuss molten steel in the pile without reference to temperatures:
    The AVRIS data from Sept 16 is loosely described as "over 800°F", and the highest temperature mentioned is "727°C/1341°F" for "14% of the pixel" in hot spot A" (which is actually not as precise as it sounds, being a rough fit to a round figure of 1000°K)
    https://pubs.usgs.gov/of/2001/ofr-01-0429/thermal.r09.html[Broken External Image]:https://pubs.usgs.gov/of/2001/ofr-01-0429/hotspot.key.tgif.gif

    Actually, hotspot G is listed at 1020°K, 747°C, 1376°F, but basically the same given the accuracy range.

    And this was not "in the pile", it was the surface of the pile visible from above. Does that mean the interior of the pile was a lot hotter 747°C in places - yes it does, but remember that a hydrocarbon fire can burn at 800°C to 1100°C, so having some visible spots at 727°C is entirely in keeping with a normal non-furnace hydrocarbon fire (i.e. wood, paper, and plastic). Thre

    And these two spots (A and G) were the HOTTEST of the hot spots. Other hot spots were in the range 700 to 900 Kelvin, which is 427°C/800°F to 627°C/1160°F. All far off the 1100°C/2012°F of a hydrocarbon fire.

    Now furnaces that melt iron will have to get that iron to the much hotter 1538°C/2800°F. Usually, this is done with forced air in an enclosed space, which would be termed a "forced air" furnace. But it can also be done in a "draft" or "natural draft" furnace where the air flow comes from the convective action of the fire rising through a chimney and creating a draft. There are a few videos of such furnaces, but blast furnaces are more common.

    Even with the blast furnaces though, "molten steel" is not really something they make. What these simple furnaces produce (through careful feeding, use of charcoal, and maintaining the air supply) is a "bloom" of iron and slag that has a combined lower melting point than pure iron.

    If there was an accidental furnace in the pile, it's unlikely it would have got hotter than a deliberately designed draft furnace.

    Here's some data for a variety of forced-air furnaces:
    Metabunk 2018-11-24 08-19-22.

    Again though, the "temperature" of a fire is a complex thing, and you need to be clear what you are actually measuring.
  8. Tomi

    Tomi Member

    That’s interesting. So I never understood why thin steel melts and thicker steel doesn’t. Will a filing cabinet, bar joist and rebar melt when the columns don’t?
    Is it time dependant

    And what happens to concrete.?AE911Truth claim that there was melted concrete. Presumably it will turn to dirt or perhaps concrete again if you add water and compress it.
  9. Mick West

    Mick West Administrator Staff Member

    No steel is going to melt unless it's in contact with something that's hotter than the melting point, and the net flow of heat is inward all the way past that melting point. This almost certainly did not happen (except on a micro scale) in the WTC fires.

    It's complicated. As steel approaches its melting point it's doing two things very well. It's conducting heat away, and it's radiating heat away. The hotter it gets, the more heat flows away.

    Now if you've got a large surrounding source of heat, like you're in a furnace at 1500°C, then steel will melt. Larger pieces will just take longer.

    But if you've got something like a large piece of steel where you are heading one end with a 2000°C propane torch, then the steel is not going to melt. The amount of heat supplied is only enough to heat up a local spot on the steel, and the heat is very rapidly radiated and conducted away. So it will not melt.

    Concrete does not "melt", it disintegrates into its components.
  10. Tomi

    Tomi Member

    So what you are saying is that small pieces of steel may melt if there is enough heat input and if there is insufficient mass of steel for the energy to radiate away to. That may apply to metal filing cabinets and sheet metal or even rebar.

    However big bits of steel are never going to melt because they have a heat sink

    Perhaps that explains why the ‘evaporated steel’ was such a rare event. It was thin steel compared to the WTC columns and the evaporation was close to one end so could only radiate heat in one direction.

    Or do you think this was also a chemical effect that caused it?
  11. Mick West

    Mick West Administrator Staff Member

    That was a chemical effect. Just melting steel looks totally different.
  12. Oystein

    Oystein Active Member

    It was a somewhat complicated process involving a bit of chemistry.

    Barnett, Biederman and Sisson, the authors of that FEMA report appendix on the two "evaporated" or "Swiss cheese" pieces of steel, determined that those pieces experienced temperatures in the vicinity of 900 to slightly over 1000 °C (from memory). That is certainly significantly hotter than what you expect from most smouldering underground fires, but also far below the ca. 1500 °C melting point of steel.

    Parts of the smouldering rubble pile certainly may have seen bae temperatures of several 100 °C, so to heat those steel pieces to 1000 °C is easier than would be at ambient 20 °C - the lower the temperature difference, the lower the net heat flow away from that piece by radiation and conduction.

    What happened at ca. 1000 °C was, roughly, this:

    There was ambient sulfur (not elemental - as oxide, hydroxide, carbide, whatever) in the local environment. This sulfur compound - probably a gas at such temperatures - diffused into the steel, between the boundaries of the microscopically small iron grains that steel is composed of after milling and what not. The grain boundaries in part reacted with the sulfur to form iron sulfide or similar. That is part of the hot corrosion. Also, and critically, the very existence of there being several chemical substances in intimate contact at this microlevel - a situation called a "eutectic" - results in the mix having a joint melting point significantly below that of the main component, iron. Specifically, the particular mixes of chemicals that Barnett, Biederman and Sisson found in the specimens, has a "eutectic" melting point in the vicinity of 1000 °C. In fact, Barnett, Biederman and Sisson proposed that temperature because it is the eutectic melting point of the material mix their analysis found. So the grain boundaries melted (a microscopically tiny amount of melt!), and the grain then fell off the steel - exposing more grains underneath to the sulfur-rich environment. More sulfur diffuses in between newly exposed iron grain boundaries, creating a new eutectic, and thus corroding away another grain, and so on, and so on.
    Barnett, Biederman and Sisson could not identify the source of the sulfur - but that doesn't mean it's a mystery. There are plenty of possible sources. One of the authors suggested acid rain seeping into the rubble pile may have provided enough. I read one proposal that burning PVC would release HCl, a strong acid, which in turn is capable of decomposing gypsum, freeing the sulfur in it (gypsum as such, it is claimed, would not release sulfur just by being heated to 1000 °C).
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  13. Jeffrey Orling

    Jeffrey Orling Active Member

    Perhaps the most stunning part of the "discussion" is that we have little to no real data from the actual event... standing building to collapsed building. We have videos and stills and some eye testimony. The latter is hardly reliable and mostly from untrained observers.

    The bulk of the "evidence" comes from the debris pile and that began to "degrade" or change from the moment the collapse ended. Water and chemicals to suppress fires burning in and below the debris were poured on for weeks, rain of course also occurred. Rescuers cut steel w/ torches, steel was removed. The debris pile was not static in any sense of the word. But this pile contained evidence of the collapse AS WELLS AS evidence of the erosion and changes in the debris pile as a result of chemical mixing and chemical reactions which took place in addition to the fires which were extensive for months. So the evidence taken from debris pile was in many if not most case altered evidence as chemical reactions continued over time. Mechanical deformations of steel would be unlikely although not impossible.

    The so called Swiss cheese steel looks very much like a debris artifact than it does a pre collapse artifact. But how can one know for sure? If it was recovered well after the collapse one could assume that at lease SOME corrosion/erosion occurred post collapse.
  14. Tomi

    Tomi Member

    What is also surprising is the lack of evidence of any molten steel then.

    Didn’t see any beams or columns with molten blobs at the end.

    Which implies if steel melting did occur it was rare. So the ‘rivers of molten steel’ were perhaps more likely to be trickles of aluminium or lead or something else.
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  15. LardyL

    LardyL New Member

    You'd be very hard pressed to find molten "blobs" of steel or ferrous materials in fire debris unless there have been some very unusual conditions in the fire or you are looking at steel "wool". That's based on over a thousand fire scene inspections and numerous tests of various components, dusts and materials containing ferrous residues.

    I've seen the thermite reaction occur in one fire involving a CNC laser cutter that was making car parts for Aston Martin. In that case there was a build up of aluminum alloy swarf/cuttings and fly from the processing of parts along with high magnesium steel parts and there was enough energy retained in some of the swarf/fly for that to ignite the mixture in a box section ventilation duct that served as the machine frame. The resulting material burned through 8mm plate steel of the box chassis of the machine and took out about another 20mm of precast concrete floor below. Somewhere I have photos of this as I gave a talk on it to Fire Service and Insurers - it was a very localised fire but burned very hot indeed.

    I have dealt with two explosions/fires of mill scale/steel fines from a shot blaster being used to prepare sprinkler pipes (really!) for surface coating, that were in a series of about 6 fires on the same machine. This involved ignition of ferrous material within the dust treatment plant and could only have involved the ignition of a "nut" of steel/mill scale in the very high temperature process of shot blasting the pipes.

    I've seen a very high temperature fire involving a VOC abatement plant dealing with solvent vapours from high volume printing works which rendered the stainless steel of the heat exchanger down to a ferrite core with a brittle outer layer of high carbon ferrous material. If you lived in the UK you'd know what a curly wurly is (chocolate coated toffee) - well this open mesh was a curly wurly, when you bent it the outer layer cracked and split whilst the inner layer was flexible, quite unusual. This was a very high temperature fire where a hole was burned through the outer shell of the heat exchanger and it's not common to see such artifacts in structure or even plant fires.

    Anyone who studied physics at school when we did knows that if the steel is in the right orientation and thickness then it will burn in air or in oxygen under the right conditions. You can put a match flame to steel wool and it will burn leaving droplets at the end of the fibres. But this is not going to happen to any structural steel components within a fire in a building, unless you are dealing with some form of strengthening wire, some dust/fly or powder. Certainly not with structural steel, although there are many occasions when you will see deformed steel in office, domestic or industrial fires, particularly in warehouse or storage fires where the fire loading is high or under steel/iron roofs where the fire is "held" for prolonged periods.

    Also you need to bear in mind that metals used in construction and in commercial furniture/room dividers are not the pure metals. The aluminium containing materials are often alloys and many have lower melting points that the pure metals. Also melting and softening of one material, such as an aluminium alloy, can cause the formation of a lower melting eutectic mixture if it comes in contact with another material. This commonly occurs with aluminium and copper, fooling the inexperienced investigator into thinking they have found melting of copper due to electrical arcing when it is simply that a flow of aluminium into the copper causing it to melt below the normal softening temperature. This was quite commonly seen in the old days when fire alarm wiring in vulnerable areas was installed using mineral insulated metal sheathed cable (MIMS) and the sheath employed was an aluminium alloy - to allow the cables to be bent easily. The aluminium would cause the copper to melt and run.

    You might want to look further into the likely temperatures present in structure and car fires. I know of data that was published by the Transport Research Laboratory in the UK that includes the temperatures measured at the roof of test burns on vehicles. This was from the late 1980s or early 90s and they were reporting over 1600C+ measured with thermocouples placed under the car roof at full involvement. Structure fires are also prone to hotspots where the fire will act like a furnace or oven depending on fuel loading, heat losses and ventilation. This latter aspect is the subject of ongoing research in the fire investigation field.

    Most modern research is more interested in heat release rates (as these relate to fire modelling and real world fire behaviour as opposed to temperatures). A good place to start with vehicles fires might be Mike Spearpoint's work such as: https://firesciencereviews.springeropen.com/articles/10.1186/2193-0414-2-5
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  16. Oystein

    Oystein Active Member

    Holy shmoly, LardyL!
    I know next to nothing about most things you mention, but you sound an awful lot like you know really well what you are talking about!

    Great post :)
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