[TheForge] Re: cold drawn steel

Mon Oct 20 22:34:01 2003

When I was buying steel for engineering use -- for heavy equipment -- almost
100 percent was hot rolled, hot finished material and in many cases it was
alloy steel i.e. 4140 or 4340 etc.  For some very heavy applications the
product was a forging rather that rolled.  Still hot finished.  Most
engineering steels and heavy drops you might find at a scrap yard will be
hot rolled.  In use it was machined, heat treated and then final machined or
ground depending on end use and requirements.  One interesting company,
Finkl, in Chicago produces and sells their heavy bars as forgings rather
than by rolling. (8 to 16 inches in diameter standard)  The company I work
for before retirement purchased some large forging from Finkl for new screws
for a large plate mill.  Finish diameter of the screws was 36 inches.  Total
length including the drive spline was about 20 feet.  Now that's a screw.
Some of you might enjoy their web site -- http://www.finkl.com/

Note that their trade mark -- is the same as Francis Whitaker's touchmark.

Dave Smucker

----- Original Message ----- 
From: <[email protected]>
To: <[email protected]>
Sent: Monday, October 20, 2003 8:02 PM
Subject: Re: [TheForge] Re: cold drawn steel

> 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,
> [email protected] 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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