Why do I burn my hand?

[ESjaavik]

If I heat the end of a steel bar to red hot and it's long enough, I can hold it in the other end while bending forging or doing other work. Then when I dunk the hot end in a bucket of water, the heat seems to run up the bar and it gets too hot to hold.

Why does this happen?
I know that heat doesn't like water, but how can it run away from it?

[balsaman]

Maybe it's the steam that is burning you?

Eric

[ynneb]

Good question. I dont know the answer, but maybe heat preferes to rise. When you place the bar in the water it is vertical and the heat rises. ( Theory )

Maybe you are concentrating so much on the bar when its in the water, you forget you have a cigarette in your hand, and it burns you. Happens to me all the time. I also wish they had holes in welding masks so you could have a ciggy in your mouth while welding. Maybe I should patent that idea.

[trubleshtr]

LET GO of the metal.......


If you had a beer and a buddy on one side and a stranger on the other, who would you rather give the Beer to0....(assuming you have to give the beer away?) Your buddy right? MOlecules in the steel bar that are excited will more readily transfer their "excitement" to their buddy molecules before going to the water( THink path of least resistance) That's how I would explain it.....

[Rekd]

When you put the hot metal in water, heat disapates in any direction away from the cold, thus up the rod to your hand.

[sol]

This calls for an experiment:
Take two bars and heat them together, put one in water and the other in an empty bucket while holding both...does the one in the water feel hotter than the one in the empty container? Except for the steam rushing up the bar to your hand I can see no reason for the quenched bar to feel hotter than the dry one.
I suspect it is more a matter of awareness as well as the reaching of a relatively specific pain threshold....
Be neat to hear the results, I will try to remember to give this a shot tomorrow.

[Chagrin]

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.

[sol]

Okay, I tried to replicate Esjaavik's experience today and found that the rod did indeed feel hotter when thrust into water as compared to one that was not. The water had to cover more than just the very hot tip though; after a few tries a "Well Duh" explanation became obvious.
The very hot tip transfers the heat to the water almost explosively with all of the instant steam, as the steam rushes for the water's surface it dumps heat into the cooler mid-section of the rod which of course conducts the heat up to one's hand.
As an aside but relevant: 100°F 37°C water makes a comfortable shower, 120°F 48°C water is tolerable for a while, 140°F 60°C water is dangerous and painful. The point being it does not take a great increase in temperature to go from "I can still hold this" to " Drop it NOW" and when working with live steam a 15° increase is exceedingly easily accomplished..