That was really interesting. I throughly enjoyed that.
I had a really good lesson in hot vs. cold rolled after I bought my small ironworker. I had specified cold rolled for a project where I needed to punch thousands of holes in 16 gauge steel. Hot rolled and cold rolled obviously got mixed up. After a while I could hear the difference between the two and knew which was which. Cold rolled "snaps" when punched on a 25 ton ironworker. And because it is a small machine I could literally feel the ductility as the punch entered the die. Hot rolled is "gummy" compared to the snap of cold rolled. You could also see the difference in the plugs that were spat out of the die in the way they deformed. Cold rolled were sharp; hot rolled compressed on the edges and stuck more inside the dies.
BTW, it is just me, or was the narrator here in almost every educational film ever shown since the dawn of time? His voice transports me to junior high school where the instructor didn't feel like letting us use machines that day so he sat us all down and showed us a film.
Thanks for posting.