Good question. :)
We went over that so fast in metallurgy class that I don't remember
the mechanism.
I know guys can shrink metal with a large sponge full of water on
red hot steel, like an auto body man shrinking a stretched area of
sheet metal and the drive shaft man can shrink the bowed-out side of
a drive shaft the same way.
I tried that trick on a auto-dent once... I made the stretched metal
bigger not smaller. :/
Alvin in AZ
On a hail dent, use dry ice. Just in the center when the body is hot hot in the
sun.
It puckers up and flattens out.
Martin
Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member
snipped-for-privacy@XX.com wrote:
Tom,
I'm only an amateur. And I'm not sure I properly understood your
question. But if I did, I believe the answer is: "Yes". The
mechanical / blacksmithing term for this is "upset".
Take a straight bar of steel. If you heat a point or ribbon on one
side with a torch, as it heats, it will bend in the opposite direction
from the heated side.
Upon removing the heat source, as it cools, it will return to straight.
As it continues to cool, it will continue to bend, now to the side you
heated. Once cool, it will remain there. The ribbon that you heated
will be upset i.e. thicker than when you started.
Welders say "the hot side is the short side". Sort of the welding
equivalent to the mechanic's chant "righty tighty lefty loosy".
V
Its a complex question because there are a number of phase
transformations available to steel as it cool. So due to thermal
expansion you get elongation and contraction. If the thermal stresses
are larger than the geometry allows and you exceed the yeild strength
you'll get distortion. Then depending on how hot you make it and how
you cool it you can get phase transformations depending on the
composition of the steel. Most of these transformations result in a
change in volume as the crystal structure changes. This too can cause
distortion.
|>If you heat steel then let it cool back to the original temperature,
|>does it shrink from the original size
|>Tom
The proof in the pudding is the tons of metal plants in Red
China/Beijing/Taiwan/etc... where they make a great amount of
pre/aftermarket items/parts for motors fasteners, scooters, guns (NorInCo)
that don't quite fit even when the proper cast/dies are used in the attempt
to duplicate the original.
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.