[TheForge] Ed- heat treating S-7

Tue Sep 2 14:35:04 2003

The issue is not normalizing or annealing the steel per say.  (Let me say
also, that I did not understand this for a long time myself.)  The issue is
that what give us smaller grain size is the action of going through the
transformation point.  (in the cooling direction)  As the steel is
transformed from the FCC form to the BCC form we get the formation of
smaller grain size.  This is why Jim Batson goes through this step 3 times
before heat treating his knife.  The only other thing we can change (the
chemistry of the steel is already set) to get small grain size is forging
itself.  This physical deformation also reduces grain size.  Only problem is
that every time we heat into the forging temperature range we are helping
the formation of larger grain size.  This is one reason that fewer heats are
better as is the fact that fewer heats means more deformation per heat which
is good.
This grain size issue is why some, George Dickson for example, suggest as
much machining / grinding rather than forging for making tools.  Unlike
George, I would never quench S-7 in anything faster than oil from a cooling
stand point.  I must say that George has made 100's of tools quenching in
brine as have the many many students that have taken his classes.  The S-7
we buy from the suppliers comes with a very fine grain size -- because they
have been very careful to obtain this fine grain size to aid in the end use
of their product.  The same can not be said for many of the non-tool steels
we might work with.

Dave Smucker

----- Original Message ----- 
From: "Andrew Vida" <[email protected]>
To: <[email protected]>
Sent: Tuesday, September 02, 2003 1:33 PM
Subject: Re: [TheForge] Ed- heat treating S-7

> On Thu, 28 Aug 2003 20:41:39 -0400, Kevin donahoe <flyinpig@go-
> concepts.com> wrote:
>
> > I was wondering if normalizing is ever an issue with air quenched steel?
> > Just not part of the process, or ever a need once it's heated from
> > annealed?
>
> I would imagine that it is not.  Annealing such steels
> requires a very slow ramp to ambient, I believe in the
> 48 to 72-hour range.
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