Subject: Re: Softening Air Hardening Steel?

From: [email-masked] (Andy Dingley)
Date: Sun, 15 Sep 1996 11:26:35 GMT

The moving finger of [email-masked] (Ken Knaell) having
written:

>in the barbecue with a bunch of charcoal and heated it up
>to a good bright red and covered the barbecue and let the
>charcoal suffocate overnight.  It still was as hard as ever.

I've softened a piece of similar stuff by doing the same thing, but
using a coke fuelled domestic fire for the heating. It's hotter than
barbecue charcoal, as the draught is better.

Handy things solid fuel stoves (the smokeless fuel sort with a glass
door and draught control) - you can even use them for forgework, if
you don't mind carrying lumps of glowing orange iron through the
lounge.

--
Do whales have krillfiles ?

---

From: "Steven O. Smith" <[email-masked]>
Date: Mon, 16 Sep 1996 17:26:29 GMT

The air hardening steel I use has a much higher critical temp. than
carbon steel. You need to get the stuff to a nice bright orange (1800F)
for annealing to be effective.

-- 
Steven O. Smith
[email-masked]

---

From: [email-masked] (Ken Knaell)
Date: 16 Sep 1996 20:21:59 -0400

In rec.crafts.metalworking, [email-masked] (Peter Brooks) writes:
>I've been wondering about this, too.  I got a *large* rotary die (possibly
 //// SNIPPED ///
>BTW, is die steel (A2 if my memory and my understanding of Machinery's
>handbook listing) good for anything other than dies?  I keep thinking about
>making the world's biggest replica of an E.T.Westbury Atom Minor......
>The die steel might make one hell of a sleeve.
>
>Pete Brooks
>
I want to thank all (both) who came up with some answers for
me on this.  It is a very technical subject and I do not
understand the reasons fully for the process of annealing
this or these type(s) of steel.  However there was consensus on
the processes and I will try to describe the two alternative
ways.  One is the "step" method and the other involves slow
cooling through a transition region.

Both methods involve initial heating of the steel to 1560F
to 1600F (maybe higher for some rarer types).

In the "step" process the 1600F is held for one hour per
inch of thickness of metal.  Temperture is readjusted
to 1200F and held there for 18 to 24 hours and then the
sample allowed to cool to room temperture in free air.

In the "continuous" process the temperture is programmed
down from 1600F to 1200F at a rate of 20F per hour.  At
1200F the steel is again allowed to cool in free air to room
temperture.  Some steels may tolerate colling at 40F/hour
instead of the 20F/hour.

I notice that the 1200F as the lower temperture is common
to both methods and the upper temp of 1560F to 1600F is also.
I do not understand the reasons for this behavior to be
able to explain why it works.  The step method would work with
heat treat ovens that did not have the programmable ramp
down feature however and would seem to be a more workable
method in a simpler oven however.

The comment was made that the natural cooling in my
backyard barbecue by smothering the charcoal was probably
much faster than the 20-40F/hour.  So I wish I had an
oven now to try this out but that will be a ways down the
pike.

ken "stick to hamburgers" knaell
Bethesda, MD