O1 heat treatment

scott.livesey

scott.livesey

Dealer - Purveyor
hi,
was following a discussion on Caldie and went looking for a more manly man steel. i mean come on, Caldie sounds girly maan. i thought manly maan like Ahhnold. closest i could find was Arne(http://www.uddeholm.com/files/PB_Udd...ne_english.pdf). found a section about sub-zero quench and aging:
sub-zero treatment and aging
Pieces requiring maximum dimensional stability
should be sub-zero treated and/or artificially
aged, as volume changes may occur in the
course of time. This applies, for example, to
measuring tools like gauges and certain struc-
tural components.
SUB-ZERO TREATMENT
Immediately after quenching the piece should
be sub-zero treated to between -70 and -80 °C
(-95 to -110°F), soaking time 3–4 hours,
followed by tempering or aging. Sub-zero treat-
ment will give a hardness increase of 1–3 HRC.
Avoid intricate shapes as there will be risk of
cracking.
AGEING
Tempering after quenching is replaced by
ageing at 110–140°C (230–285°F). Holding
time 25–100 hour
no information listed on hardness after aging. has anyone tried this technique?​
 
The aging is a simple matter of time vs. temperature, or rather time=temperature in diffusive based processes, the reason most folks don't have too much to say on the technique is that it is a whole lot cheaper and easier to bump up the temp and get it done in a couple of hours. There is some research that indicates that one can gain some toughness for the the same hardness by using time instead of temp.

On the other issue, dimensional stability results from the elimination of the conversion from FCC phases to more expansive BCT and BCC phases, i.e conversion of retained austenite. The 1-3 HRC difference is alarming and indicates that the heat treatment procedures given are for the cheapest/easiest route to put heavily sphreoidized material into solution with the idea of fixing the undesirable side effects later. Knifemakers have the luxury of taking our time and giving the blade the individual attention to get things done correctly from the start. One can debate super lattices and exotic carbide precipitation, but if you are getting large dimensional changes and increases in HRC, you are merely fixing retained austenite, which can be greatly reduced by proper soaking procedures with a steel as simple as O-1.
 
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