Re: Goodbye, Mr Roberts
Again, on what basis do you make this assumption? Have you cast steel before, or studied how it is done? Without referring to my earlier explanation on another thread, do you understand the principles of hot working, warm working, and cold working, and also of grain growth and crystallization?
If your assumption is or very similar to as follows (and this is based on your own statement), "Steel must reach a certain temperature for its structure to be reduced, and that is the only interaction between heat energy and the strength of steel; therefore since there could not have been enough heat energy to achieve the relevant temperature, the steel could not have had its strength noticeably reduced," then you are incorrect on at least two accounts.
- First, the process of applying a tremendous load, which under room temperature would only cause creep, would serve to alter the the properties of steel more rapidly as it became heated to more significant fractions of its melting temperature. Warm working takes place at 30% of the melting point, and that is the low end estimate of the temperature range. In fact, applying force to a warm piece of steel is one of the numerous ways in which it is shaped or treated.
- Second, yes, steel has good thermal conductivity to relatively quickly evenly distribute the heat. However, it has relatively low heat capacity (0.460 kJ per kg per degree K, compared to 4.184 for water). Any fire near steel, almost without regard to shape or size of that steel, will quickly deliver the thermal energy necessary to raise its temperature in a rapid fashion near the points of contact. You already know this presumably from experience with stainless steel pots and pans; void of water, these heat up very rapidly and rather uniformly. You can do an experiment with just a lighter and a pot you were going to throw away by putting the flame on one spot for, say, 56 minutes or so and let me know if that area is hot. Furthermore, there is evidence that much of the fire in the floors above your favorite one (78th) was more concentrated towards the center.
As an aside, the effects of thermal expansion on steel should not be neglected. While relatively small, the change in temperatures both up to the maximum experienced and in some places back down to room temperature were rapid. I have read some theories that this played a roll in reducing overall structural integrity and it seems plausible.
Originally posted by ThePythonicCow
View Post
If your assumption is or very similar to as follows (and this is based on your own statement), "Steel must reach a certain temperature for its structure to be reduced, and that is the only interaction between heat energy and the strength of steel; therefore since there could not have been enough heat energy to achieve the relevant temperature, the steel could not have had its strength noticeably reduced," then you are incorrect on at least two accounts.
- First, the process of applying a tremendous load, which under room temperature would only cause creep, would serve to alter the the properties of steel more rapidly as it became heated to more significant fractions of its melting temperature. Warm working takes place at 30% of the melting point, and that is the low end estimate of the temperature range. In fact, applying force to a warm piece of steel is one of the numerous ways in which it is shaped or treated.
- Second, yes, steel has good thermal conductivity to relatively quickly evenly distribute the heat. However, it has relatively low heat capacity (0.460 kJ per kg per degree K, compared to 4.184 for water). Any fire near steel, almost without regard to shape or size of that steel, will quickly deliver the thermal energy necessary to raise its temperature in a rapid fashion near the points of contact. You already know this presumably from experience with stainless steel pots and pans; void of water, these heat up very rapidly and rather uniformly. You can do an experiment with just a lighter and a pot you were going to throw away by putting the flame on one spot for, say, 56 minutes or so and let me know if that area is hot. Furthermore, there is evidence that much of the fire in the floors above your favorite one (78th) was more concentrated towards the center.
As an aside, the effects of thermal expansion on steel should not be neglected. While relatively small, the change in temperatures both up to the maximum experienced and in some places back down to room temperature were rapid. I have read some theories that this played a roll in reducing overall structural integrity and it seems plausible.
Comment