In article ,
Ed Huntress wrote:

On Fri, 16 Dec 2011 00:58:41 -0500, Ed Huntress
wrote:

On Thu, 15 Dec 2011 23:36:28 -0600, "Pete S"
wrote:

I ran into some trouble making fire strikers work properly late this summer.
I have been making them for a long time and all of a sudden they quit
working. Using brand new 3/16" X 1/4" W1 from MSC. The trouble SEEMED to
start when I got into a new 3 foot bar.
After a lot of question-asking and some research and analysis, I think I
have solved my problem.
What do you guys know about decarburization of tool steels?
Why?

Because the carbon goes away. G In general, it's the result of
heating carbon steel in air -- the hotter you get the steel, the worse
the condition is. Heating it above transition temperature (Curie
point) without protection from oxygen in the air will start decarb
immediatelyl. The carbon combines with the oxygen. The higher the temp
and the longer the part soaks at high temperature, the worse it gets.

Plain high-carbon steels (W1; music wire; AISI/SAE 1070 and above) are
the worst offenders. High-alloy steels, in general, present less of a
problem.

How much?

An eigth-inch layer of bark (decarb layer) is quite possible if you
really screw it up.

Examples?

When they used to make a lot of punches and other tools from W1, it
was a major heat-treat issue. The popular solutions are heating in a
carbon boat (for small-scale heat treating); heating in a dissociated
ammonia or other carbon-rich atmosphere; heating in a ceramic, clay,
or steel boat with charcoal or carburizing compound; and heating in a
vacuum. Look up "muffle furnace," too.

Etc.?

Etcetera. g

Oh, I forgot: Wrapping in stainless steel foil is commonly done for
onesies and twosies of alloy steels, but I don't know if it's
effective enough for plain-carbon steel. Maybe.

It works if one wraps the steel in paper before wrapping it all with
stainless steel foil. The paper burns, absorbing all the oxygen in the
packet.

Joe Gwinn