"Ed Huntress" wrote in message
...
wrote in message
oups.com...
I have two samples of steel, one that is annealed, and one that is not.
Both samples are in the shapes of cylindrical pucks. In both samples,
the steel was found to be slightly harder on the inside of the sample
than on the outside, but the trend is slightly more noticeable in the
un-annealed sample. Any ideas as to why this is? Thanks!


We could make a better guess if we knew what grade of steel you're talking
about, and how it got to be "cylindrical pucks" (cast? machined from
barstock? etc.).

However, if it's a common grade of heat-treatable steel, the most likely
answers are these. The "annealed" puck that is harder inside was badly
annealed. It should be within a couple of Brinell hardness points of the
softest state of the steel (as low as 120 HB for low-carbon steel; much
higher for some alloys, such as 269 HB max for 440 stainless). If not, it
wasn't heated to a high enough temperature, or it wasn't held there long
enough, or something wasn't done right in the cooling cycle. It would be
interesting to know how the inside of the steel got hardened in the first
place: cold-rolling or other work hardening? Or heat treatment?

As for the hardened one, it could be any of several things. The surface
could be decarburized from being improperly annealed. That is, it was
annealed without sufficient protection, or sufficient carbon potential, in
the heat-treatment atmosphere.

Besides the grade of steel, it would help to know what the specific
annealing treatment was. I assume you're using the term "annealed" as it's
used in metalworking technology: heated above the transition ("critical")
temperature and held there for a specific amount of time, and cooled at a
specific rate. The "specifics" vary with steel grade and the thickness of
the pucks. If it's a high-carbon steel, annealing also requires atmosphere
control.

If you mean that somebody got it red with a torch and then walked away
g,
that's another kettle of fish. Or another piece of wrecked steel.

--
Ed Huntress

Nicely said, Ed.

Harold