low temperature aging VS. tempering

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_Uddeholm_arne_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?
scott
 
Interesting reading there Scott - First time I'd seen "ageing" used for what we call "tempering". They are using long time for the steps, 3 to 4 hrs for -95ºF and 25 - 100 hours for tempering? That's 1 to 4 days held at tempering.

I'll let ya'll with MUCH more knowledge of metallurgy talk about the true tech parts.

Ken H>
 
I've done a lot of reading on cryo and I've never seen anything like "ageing" replacing tempering.
It's not like Uddeholm is new to steel or publishing anything other than solid heat treat data.
Interesting.
I went and read the .pdf you linked. I wonder if they are talking only about dimensional stability in that section?
 
scott.livesey said:
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_Uddeholm_arne_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?
scott
Click to expand...

I've never heard of anyone trying this on knives but that doesn't mean that no one has. I have an opinion on this but I wont elaborate until Kevin replies because he is the mod here and has probably forgotten more than I'll ever know about this stuff.
 
I suspect the word "ageing" is a translation of the original German word they use for our word "tempering" and when reading I mentally replaced "ageing" with "tempering". Not sure if this is correct, but seems to be what they're talking about.

I don't see any reason to use for knives - remember, it says this is for dimensional control, and the graph shows less than 0.1% which is pretty small amount on thickness of blade. Even on a 10" long blade, you're only talking about 0.010".

As Darrin says, Master Kevin is the one we'd like to hear chime in on this info.

Ken H>
 
From the way that I read it you have two things going on here. The aging is to promote dimensional stability so that you don't have the piece changing size on you, even to a very minute degree. Yes, it looks like tempering but it's not because the goal is different. Sort of like normalizing vs thermal cycling. Tempering is to produce a given hardness, toughness, and strength in the steel. That leaves me wondering if the aging process described would leave the O1 too brittle to use as a knife blade.

Doug
 
Not sure this contradicts anything we have always been taught. All things HT are a combination of time and temperature. This is simply a substitution of time for temperature.
 
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i have seen aging used to strengthen low carbon alloy steels, such as HY-180 and other high strength low alloy steel.
 
i guess there is no answer coming, sooooo, i will TOFTT and put one of the knives i finished yesterday in the welding rod oven at the office for 24 hours or so at around 250F and see what happens. the blade i will test was not given a sub-zero quench but was tempered for an hour at 325F, which tested at RC64-65.
scott
 
I think that dimensional stability is exactly what they are trying to achieve over the period of a long time. As quenched, especially with a high austenitizing temperature, RA is going to exist. If left alone, that RA will eventually convert to martensite.....over the period of a long time. This will cause a change in dimensions, even if only very minute, and to avoid that....they go with the cryo to make sure that dimensional change is kept to minimum. What I don't understand is the aging thing, which I kind of thought was the same thing as tempering. But the analogy of normalizing vs thermal cycling is a great one (that was awesome Doug). We all know that changes are affected by time and temp, much more so temp. I suppose there is something else going on using higher temps, so they came up with lower temp, but extended time. Someone who really understands the tempering processes could certainly shed more light.
 
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