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Author	Topic:   physics(?) question: why does heat rise in metal?
Casper Member	posted 09-24-2007 01:23 PM             I tried to google this but I was pretty much dead in the water not knowing how to go about it. Maybe it is a matter of perception but it seems real enough; when I solder, cut or weld on metal, the heat seems to rise in the metal, quite quickly too, while it doesn't seem to descend. I can't believe it is convection doing it although that could play a part. So what am i seeing? Does the heat actually rise? Why? It isn't like the steel molecules redistribute themselves as a gas or liquid would. Even sweating copper it is important to heat upwards (I am pretty good at this, having quite a bit of commercial experience). I have noticed this even inside enclosed spaces like while tig welding ductwork from the inside. And on large pipefitting jobs it appears (to me) quite evident. Any comments? IP: Logged
10SNE1 Moderator	posted 09-24-2007 01:58 PM             Nice question! I always assumed it was a convection thing, but never tried to weld in a vacuum. IP: Logged
Casper Member	posted 09-24-2007 02:14 PM             I'm not even sure how you would set up something to measure it. IP: Logged
tralfaz Member	posted 09-24-2007 02:16 PM             Heat does transfer through the metal in both directions when welding. however, air is heated by the metal, rises, and transfers heat back to the metal along the way. When sweating copper, it's the gas heating the metal in the first place, so that's why it's even more apparent. IP: Logged
Casper Member	posted 09-24-2007 02:24 PM             So it is just the perception that it is rising within the metal, and in a vacuum it would travel equally? IP: Logged
10SNE1 Moderator	posted 09-24-2007 02:34 PM             quote: Originally posted by tralfaz: Heat does transfer through the metal in both directions when welding. however, air is heated by the metal, rises, and transfers heat back to the metal along the way. When sweating copper, it's the gas heating the metal in the first place, so that's why it's even more apparent. What I thought. IP: Logged

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