[TheForge] Re: cold drawn steel

[theforge@mailman.qth.net]

To All,
Hot finished, cold finished, (bar or plate) I just don't know where to start! 
 
Hot finished means that the final processing step was done hot, i.e., 
incandescent.  The finishing temperature is above the recrystallization temperature 
of the alloy.  It almost always has the oxide left on it and it is usually 
about as soft as it gets. It the temperature of the material was not above the 
recrystallization temperature of the material, it would be warm working which 
would take me another hour to explain.

Cold finished begins its life as hot finished.  The oxide is pickled off and 
the material is rolled to final size oxide free.  Cold finished will show hot 
working defects more readily that hot finished as there is no oxide to hide 
the problems.  Cold finished is usually a specific grade, i.e., 1018 or 
whatever.  Cold finished is more dimensionally precise.  It is produced in smaller 
lots.

1018 refers to an AISI / SAE chemistry.

A36 refers to an ASTM specification for hot finished material used for 
mechanical purposes.  It pretty much designates a set of mechanical properties with 
chemistry being secondary.

Annealing cold finished materials pretty much return them to a near hot 
finished state.

The kinkiness that results from bending heated cold finished usually comes 
from not heating it hot enough or long enough.

Cold finishing bar or plate is done by rolling.  Rolling involves 
deformation.  Using large diameter rolls to cold finish bar or plate provides a 
nonuniform deformation of the bar or plate.  You will see apparently more deformation 
in the surface layers than you do in the center.  Shame on the cold finishers 
for not using the proper roll diameter vs thickness.

Steel that is ingot or strand cast is about as dense as you are going to get 
it.  As a matter of fact, if you cold work the material, you actually make it 
less dense.  Cold worked material is also less stiff.  Any tippy-tappying to 
compact the fibers of the material is just so much hooey.

Dr. Hochewa
Go Hokies!

In a message dated 10/20/2003 8:58:04 AM Eastern Standard Time, 
scotty@one.net writes:
>For what it is worth, I don't know of any steel products that are "rolled"
>cold.  The "proper" designation for the material is "CF" which stands for
>Cold Finished, and the hot rolled material is first descaled and then drawn
>through a die to the finished size just like wire, and becomes work hardened
>in the process.
         Wrong.  It is rolled.  I did it at the steel plant.

>Once it is heated past critical temperature, there is absolutely no
>difference from the "hot rolled" variety. I have forged many pieces of CF
>steel up to 4" dia., and once it is hot it forges exactly the same. It only
>acts kinky when you are trying to bend at a dull red, then the stiff spots
>show up.
         Wrong.  The surface of cold rolled is compacted during the rolling 
process.  I've had to check this in the micrographs while cold rolling 
stock at the steel plant.

>I have found that the quality of the cold finished bars tends to be inferior
>to the hot rolled material, that is, I suspect the mill takes the bars that
>are too ugly to sell in their "as rolled" condition, and sends them through
>the cold finishing in the hope of making "sellable" product.
         Wrong.  It is the same stock off the line.


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