As most materials increase/decrease in temperature they don't absorb/release heat evenly - for example, when you're melting lead - it always seems to get *really* hot then takes forever to finally liquify.
This might be what you're experiencing - the red end of the steel absorbing heat from the rest of the rod to sustain it's ... red. Quench it and it transfers heat uniformly through the rod. Normally such rapid heat changes occur when a material is changing state (solid -> liquid -> gas) but I could see how glowing red steel could exhibit the same property. |