1095 and O1 work hardening

S

ShadowsHamon

Joined
Jun 28, 2011
Messages
40
I basically just work with 1095 and O1 at this time and I have noticed they both will work harden. I was wondering what is going on exactly when this happens as I am curious and to figure out ways to avoid it.

If I take 1095 from the belt sander to a file, the file does not bite until I get through a thin layer of hard metal. I am sanding with bare hands and dipping in water when it gets hot.

With O1, when I mill it, if I am not doing everything just right it seems to harden. I mill drill allot of 1mm holes in 2mm diameter rods. If I peck drill, it will harden. But if I just drill straight through with the correct speed and pressure, all is good.

So my question is basically, what is going on in the metallurgy of the steel when it is work hardened in this way? It is not like the steel is reaching critical temp? Maybe on a much smaller scale the very surface of the steel being worked is reaching critical temp and since the rest of the metal is not hot, it acts like a heat sink almost instantly cooling the hot surface which is basically creating a very thin hardened layer?

This is my thoughts, what are yours? And maybe Stacy or another with the facts can chime in and tell me what is really going on.
 
It isn't heat driven, as in reaching critical. It is caused by the disruptions in the grain boundaries.

When you work the steel ,you cause strain in the boundaries. (The other name for work hardening is Strain Hardening). The same thing happens with repeated bending. Any source of energy, be it kinetic or heat, will add to the strain. Since all this happens at a temperature below the re-crystallization temperature, it is also called Cold hardening. The energy causes the boundaries to exceed their yield point, and disruptions/dislocations occur. This make the metal harder. It is these dislocations that are "healed" in annealing, and "eased" tempering.

For a rather simplified visual, imagine the rows of paving stones on your walkway....neatly nestled together. They are nice and smoothly aligned, so you might say the walk is "soft". Now lets add the energy of a few dozen winter freeze/thaw cycle and disrupt those boundaries. Now the pavers are sticking up at odd angles...and the walk is "harder".
 
If you use worn belts it will work harden the steel much more than a new belt .
 
I have been working with S7 lately and have noticed some effect like this. I was profiling a knife with a nearly worn out belt and it reached a point where it didn't want to grind much further. I was getting the steel hotter then normal trying to get the last out of that belt, now I know to just toss the belt when it is close.

I knew a lot of metal work hardened but I really did not know if steel did below critical, it makes sense now. :D
 
Thank you very much for the explanation. It is very helpful. So I would guess that basically all hardenable metals would work harden to some degree?
 
Actually strain hardening happens with all metals, this is how bronze was hardened(actually cold forging) for cutting tools before steel.
Del
 
delbert ealy said:
Actually strain hardening happens with all metals, this is how bronze was hardened(actually cold forging) for cutting tools before steel.
Del
Click to expand...

I remember a local silversmith known for his deep stamping work telling me he had to anneal a piece 5 or 6 times before he got the stamp deep enough.
 
You must log in or register to reply here.
Back
Top