Deep Cryogenic Tempering

S

samuel082799

Joined
Jul 29, 2015
Messages
20
What is Deep Cryogenic Tempering, and is it better than a regular heat treat and temper, if so what are the benefits.
 
Deep cryogenic is a phrase for cryo in LN. It is mostly a sales phrase, as -310°F is the same whoever does it...and is all the deep you need. Some use the word "Deep" to notate that they are using colder temps than a dry-ice slurry ( -100°F).

Some peole wrongly call a sub-zero treatment in a dry ice slurry "cryo", which it is not.
 
People like to invent new terms ! There are two cold treatments we speak of .
Sub-zero, about -100 F . This has been used at least 60 years. No need to invent a new word for that. It minimizes RA in the steel .
Cryogenics, the freezing point of Liquid Nitrogen , - 310 F. It minimises RA AND permits the formation of small 'eta' carbides upon tempering.
These cold treatments MUST be tempered as the final step. For the most part cryogenics is limited to high tech , high alloy steels as found in most of the 'powder metal steels.

You should question anyone who uses other terms as they may not know what they are talking about .You do want to know exactly what you're getting.
 
You will generally gain 1 point in hardness doing a sub zero or cryo treatment to a knife blade. Some steels it is recommended prior to the temper cycle and some it is recommended as part of the temper cycle, ie, temper - sub zero - temper.
 
I usually consider a statement like "cryogenically tempered" in the same group as people who say, "I tempered at 1475F and quenched in motor oil". It usually shows the person doesn't understand the process.
 
samuel082799 said:
sorry for my inexperience but what is RA
Click to expand...

Retained Austinite. This results from not taking the steel to a low enough temperature to finish the conversion from Austinite to Marstinite.

Cryogenic tempering is used by the folks who make their knives from "High Speed Tool Steel":rolleyes:

It is a buzz term. Cryo is used as part of the H/T regime for certain steels.
 
SBuzek said:
Retained Austinite. This results from not taking the steel to a low enough temperature to finish the conversion from Austinite to Marstinite.

Cryogenic tempering is used by the folks who make their knives from "High Speed Tool Steel":rolleyes:

It is a buzz term. Cryo is used as part of the H/T regime for certain steels.
Click to expand...

should 1095 be cryogenic tempered
 
samuel082799,

I may be corrected very quickly as I still have MUCH to learn about metallurgy. But based on my current understanding, as others have stated, a sub-zero quench is important because it finishes the Austenite to Martensite conversion in the steel. This is more beneficial in some steels than others. Carbon steels like 1095 finish their Martensite conversion at about 200˚f. Stainless steels on the other hand don't finish their conversion until about -90˚ or so. This will leave the steel structure with retained Austenite at room temperature. So, sub-zero is necessary for stainless. Some of the carbon steels, depending on their alloy, MAY benefit from a sub-zero quench by gaining a point or more of hardness. Like everything else I'm sure it's more complicated than that.




A better explanation here:
http://www.bladeforums.com/forums/s...-and-Some-Explanations?highlight=dry+ice+cryo
 
The following page on Crucible's website is a good introduction to the basic principles of heat treating tool steels. It's well worth a read since it is concise, accurate, and relatively short:

LINK HERE
 
actually deep cryo treatment is done at around -425, it is a different process than knifemakers use, and it does do something to carbon steels although no one knows how it actually works. i know it is used for gears on awd import cars that run 7's. if the treatment is not done the gears make one pass if that. with it the gears will last a half season sometimes.
 
You must log in or register to reply here.
Back
Top