> -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Nick Arnett > Sent: Thursday, June 29, 2006 10:19 AM > To: Killer Bs Discussion > Subject: Re: Physics Prof Finds Thermate in WTC Physical Samples > > On 6/29/06, Dan Minette <[EMAIL PROTECTED]> wrote: > > > > > > Good find on the phase diagram Charlie. To pick a nit, if the > consistency > > and structural integrity at that temp was actually the same as well- > chewed > > gum, I don't think that blacksmiths would have required big hammers and > > big > > arms. :-) Hyperbola aside, I presume that you have no difficulty with > the > > multiple references to about a factor of 2 reduction in yield strength > at > > that temperature. > > > Even if it is soft, it's still heavy... and the hammers aren't just for > shaping it, they are for annealing, which requires kinetic energy.
I thought I might have been wrong about the annealing process, so I looked it up. One decent reference, which is supported by other more technical references, is http://en.wikipedia.org/wiki/Annealing_%28metallurgy%29 To quote: <quote> Annealing, in metallurgy and materials science, is a heat treatment wherein the microstructure of a material is altered, causing changes in its properties such as strength and hardness. There are several phases in the annealing process, with the first being the recovery phase, which results in softening of the metal through removal of crystal defects and the internal stresses which they cause. The second phase is recrystallization, where new grains nucleate and grow to replace those deformed by internal stresses. If annealing is allowed to continue once recrystallization has been completed, grain growth will occur, in which the microstructure starts to coarsen and may cause the metal to have less than satisfactory mechanical properties. <end quote> I think you are referencing work hardening....which increases the strength of the steel at the price of ductility. That has to do with stress/strain. A good reference on this is http://www.engineersedge.com/material_science/work_strain_hardening.htm I know I'm a bit pedantic about this, but I've had to spend a good deal of time worrying about the tradeoffs between hardness and brittleness. I had long talks on this with a colleague who has a PhD in metallurgy...so the differences are fairly big in my mind. Dan M. _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
