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Eutectic Steel; Has it been Debunked Yet?

There are quite a few errors.

1:36 - "they mentioned the mysterious eutectic mixture that attacked the steel"


Basically this guy doesn't know what a eutectic is. It's not surprising because unless you've done a degree course where physical chemistry has been taught then you are not going to know.

A eutectic point is simply the point of solidification of a (single phase) liquid to a two phase solid at a specific composition and temperature in the binary phase diagram. (Obviously eutectics occur with more than two phases but this is the simplest). Yes this point is lower than the melting point of any other composition on the phase equilibrium diagram, but there is nothing mysterious about eutectics or eutectoids nor the Fe-S-O point at around 940°C. This has been studied.

He talks about the eutectic mixture attacking the steel, well this is not correct. The eutectic is by definition solid, therefore it can't attack anything. The eutectic is a by-product of the high temperature diffusion of Oxygen and Sulphur into the steel. He may mean a liquid of eutectic composition.

Let's assume that the temperature of the steel was at a constant 1000°C for the duration. Grain boundary melting or liquation will not occur at that temperature, however, if a species diffuses into the steel's surface then there is the possibility of reducing the melting point of the material sufficiently to allow localised melting to occur.

Sulphidation usually follows a parabolic rate law. x2=2k't2 where x is scale thickness, k' is parabolic rate constant and t is time.

k' is experimentally determined by taking weight measurements of a sample exposed to a diffusing species at a certain partial pressure over time. As the species diffuses into the sample the sample gains weight. http://www.scielo.br/scielo.php?pid=S1516-14392002000300021&script=sci_arttext

It takes hours/days for this to occur.

When I was looking at oxidisation of engineering ceramics (SiAlON and SiC) I had a furnace at 1200 and 1400°C for 6 months during final year at university. Solid State Diffusion takes a long time. Even an atom such as Carbon, which is highly mobile in Iron, will still take hours to diffuse into the steel at high concentration levels at temps @ 950°C during carburisation (case hardening) and times are 2-36 hours generally depending upon case depth.

So as the time progresses the composition of the steel changes as Sulphur diffuses preferentially at the grain boundary. The grain boundary is still solid until the correct eutectic composition is reached. When it's reached the grain boundary will melt. When this liquid solidifies as the temperature decreases it forms the eutectic microstructure of one phase in the othe,r namely fine lamaella of FeS and FeO. That is how we know that the temperature was so high.

In reference to the eutectic attacking the steel what he really means is the formation of an iron oxide/sulphur slag which is liquid and not a eutectic. It might be of the composition of at which a eutectic forms, which is indeterminable since the liquid was impossible to study, but it's not a eutectic.


3 minutes in he mentions the Harrit et al paper and then goes on to say that thermate (thermite with Sulphur) is a contributing cause to intergranular melting. This is incorrect because solid state diffusion rates are time, temperature and concentration dependent. A thermite reaction is over too quickly to be able to cause the depth of diffusion of Sulphur into the surface of the steel that was seen.

Harrit's paper shows no significant Sulphur in any of the samples yet he seems to equate this paper's "findings" of thermite with thermate.

We also know that thermite could not be the cause because we would also see significant quantities of Aluminium in the phases present because Aluminium will dissolve in this this high temperature slag and then precipitate upon cooling thus forming Al phases. This was not observed.

At @ 6:00 he conducts his experiment but he has no way of determining what temperatures where reached. This should have been done with a number of thermocouples placed against the steel. For high temperatures of @ 1000°C then a Platinum and Platinum/Rhodium thermocouple should be used with a multimeter and calibrated beforehand.

All we know is that temperatures were high enough to melt aluminium alloy 2024 which has a liquidus at 638°C (and a solidus at 502°C)

7.28 - he states that none of the materials caused intergranular melting. He must have super power vision to tell that by eye!! You have to do some metallography to determine the effect - clearly not done. He has no idea what effect his experiment had on the steel because he hasn't examined it. Just looking isn't enough.

7.35 - he states that no sulphidation occurred. How can he determine this?? He hasn't examined the steel metallurgically so how does he know that diffusion of Sulphur hasn't occurred? The steel beam has certainly oxidised.

He then just drivels for a bit with the usual unsupported nonsense.

At 9.16 he states that the collapse of WTC 7 from a new phenomenon called thermal expansion (due to an office fire) - which is just laughable. Thermal expansion of metals has been known for some time - infact clock makers knew about it due to errors in time keeping during summer when the pendulum's length would increase.

I'll give him credit though. He did get off his bum and actually try to do something, unfortunately it wasn't performed very well and there is no point in doing the experiment if

a) You don't perform the experiment for long enough.

b) You don't know what temperature was reached (although I expect @ 1000°C wouldn't have been difficult with the materials burned).

c) The is no metallurgical analysis of the steel afterwards. - If that had been performed then he may well have seen evidence of Sulphidation.
 
Sunstealer said:
There are quite a few errors.

1:36 - "they mentioned the mysterious eutectic mixture that attacked the steel"


Basically this guy doesn't know what a eutectic is. It's not surprising because unless you've done a degree course where physical chemistry has been taught then you are not going to know.

A eutectic point is simply the point of solidification of a (single phase) liquid to a two phase solid at a specific composition and temperature in the binary phase diagram. (Obviously eutectics occur with more than two phases but this is the simplest). Yes this point is lower than the melting point of any other composition on the phase equilibrium diagram, but there is nothing mysterious about eutectics or eutectoids nor the Fe-S-O point at around 940°C. This has been studied.

He talks about the eutectic mixture attacking the steel, well this is not correct. The eutectic is by definition solid, therefore it can't attack anything. The eutectic is a by-product of the high temperature diffusion of Oxygen and Sulphur into the steel. He may mean a liquid of eutectic composition.

Let's assume that the temperature of the steel was at a constant 1000°C for the duration. Grain boundary melting or liquation will not occur at that temperature, however, if a species diffuses into the steel's surface then there is the possibility of reducing the melting point of the material sufficiently to allow localised melting to occur.

Sulphidation usually follows a parabolic rate law. x2=2k't2 where x is scale thickness, k' is parabolic rate constant and t is time.

k' is experimentally determined by taking weight measurements of a sample exposed to a diffusing species at a certain partial pressure over time. As the species diffuses into the sample the sample gains weight. http://www.scielo.br/scielo.php?pid=S1516-14392002000300021&script=sci_arttext

It takes hours/days for this to occur.

When I was looking at oxidisation of engineering ceramics (SiAlON and SiC) I had a furnace at 1200 and 1400°C for 6 months during final year at university. Solid State Diffusion takes a long time. Even an atom such as Carbon, which is highly mobile in Iron, will still take hours to diffuse into the steel at high concentration levels at temps @ 950°C during carburisation (case hardening) and times are 2-36 hours generally depending upon case depth.

So as the time progresses the composition of the steel changes as Sulphur diffuses preferentially at the grain boundary. The grain boundary is still solid until the correct eutectic composition is reached. When it's reached the grain boundary will melt. When this liquid solidifies as the temperature decreases it forms the eutectic microstructure of one phase in the othe,r namely fine lamaella of FeS and FeO. That is how we know that the temperature was so high.

In reference to the eutectic attacking the steel what he really means is the formation of an iron oxide/sulphur slag which is liquid and not a eutectic. It might be of the composition of at which a eutectic forms, which is indeterminable since the liquid was impossible to study, but it's not a eutectic.


3 minutes in he mentions the Harrit et al paper and then goes on to say that thermate (thermite with Sulphur) is a contributing cause to intergranular melting. This is incorrect because solid state diffusion rates are time, temperature and concentration dependent. A thermite reaction is over too quickly to be able to cause the depth of diffusion of Sulphur into the surface of the steel that was seen.

Harrit's paper shows no significant Sulphur in any of the samples yet he seems to equate this paper's "findings" of thermite with thermate.

We also know that thermite could not be the cause because we would also see significant quantities of Aluminium in the phases present because Aluminium will dissolve in this this high temperature slag and then precipitate upon cooling thus forming Al phases. This was not observed.

At @ 6:00 he conducts his experiment but he has no way of determining what temperatures where reached. This should have been done with a number of thermocouples placed against the steel. For high temperatures of @ 1000°C then a Platinum and Platinum/Rhodium thermocouple should be used with a multimeter and calibrated beforehand.

All we know is that temperatures were high enough to melt aluminium alloy 2024 which has a liquidus at 638°C (and a solidus at 502°C)

7.28 - he states that none of the materials caused intergranular melting. He must have super power vision to tell that by eye!! You have to do some metallography to determine the effect - clearly not done. He has no idea what effect his experiment had on the steel because he hasn't examined it. Just looking isn't enough.

7.35 - he states that no sulphidation occurred. How can he determine this?? He hasn't examined the steel metallurgically so how does he know that diffusion of Sulphur hasn't occurred? The steel beam has certainly oxidised.

He then just drivels for a bit with the usual unsupported nonsense.

At 9.16 he states that the collapse of WTC 7 from a new phenomenon called thermal expansion (due to an office fire) - which is just laughable. Thermal expansion of metals has been known for some time - infact clock makers knew about it due to errors in time keeping during summer when the pendulum's length would increase.

I'll give him credit though. He did get off his bum and actually try to do something, unfortunately it wasn't performed very well and there is no point in doing the experiment if

a) You don't perform the experiment for long enough.

b) You don't know what temperature was reached (although I expect @ 1000°C wouldn't have been difficult with the materials burned).

c) The is no metallurgical analysis of the steel afterwards. - If that had been performed then he may well have seen evidence of Sulphidation.
Click to expand...

Stop trying to distort the TWOOF with science and math mumbo jumbo.
 
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