heat expansion

[commodore]

How does heat expansion work?
I'm interested in how metal will bend either away or towards heat.
What if you heat just a little section of metal with heat (not hot enough to melt, just expand), and keep the rest at normal temperature, what will happen to the heated part? My idea is that it will expand and form a little bump in the metal.

 

[Carburize]

I believe you are correct - the expansion of the hot zone will be constrained by cool material around it and if the zone is hot enough to creep it will produce a bump. The technique you are describing is sometimes used in welding stainless steel pipework - a hot pass over the weld with a TIG torch with no filler wire will increase the height of the weld bead. The technique only works on stainless steel - because if its lower thermal conductivity (compared to carbon steel) and retains the heat aclose to the weld zone long enough for the creep to occur.