12-29-2017, 05:08 AM
It's generally not discussed much, but auto hardening is possible. It was proposed as a reason for some broken tips on knives several years ago on another forum. The tip had even less mass than the edge, and heats up even faster, and if the rest of the blade is relatively cool, it can self quench.
Softening is assumed because overheated blades generally don't behave as though they were quenched and and not tempered, ie the edges don't just break.
There is also a phenomenon in hardening of steel where the faster you heat it, the higher the hardening temperature becomes. I do not know the limits of this. There is a fair bit of work being done on flash hardened steels for automotive uses. The steels are heated, "soaked" and quenched in something like 10 seconds.
Also, that was the wrong video. Try this one.
https://youtu.be/mRuSYQ5Npek
Softening is assumed because overheated blades generally don't behave as though they were quenched and and not tempered, ie the edges don't just break.
There is also a phenomenon in hardening of steel where the faster you heat it, the higher the hardening temperature becomes. I do not know the limits of this. There is a fair bit of work being done on flash hardened steels for automotive uses. The steels are heated, "soaked" and quenched in something like 10 seconds.
Also, that was the wrong video. Try this one.
https://youtu.be/mRuSYQ5Npek