Looking for cryo treatment parameters of a rather uncommon steel?!?

M

mark23

Joined
Jul 14, 2002
Messages
375
Hi!
I need your help regarding cryo treatment parameters for a steel called CRV2/1.2631 . As I want to get the grain as fine as possible, I want a cryo treatment having done with it as a part of the heat treatment. The metallurgy of the steel reads

C - 0.5%
Si - 0.9%
Mn - 0.5%
Cr - 8.5%
Mo - 1.2%
W - 1.2%
Fe - balance

I want a cryo treatment right after hardening/quenching prior to a double or triple temper. Information on the standard heat treatment can be downloaded here: PDF file.

Any recommendations?

Thanks for your help!!!

Best Regards

Mark23
 
Here is an other Link with information on the heat treat cycle with a triple temper PDF file.

By the way, which parameters would you choose to get the finest grain out of this steel? The tungsten should eat up quite a lot of the carbon when doing a high temperature tempering (aiming for secondary hardness), and the tungsten carbides should be very small ...

Additional Info on the geometry: The knife has a length of about 220 mm and is ground from 1/8 stock.

Thanks!!!


Best regards

Mark23
 
CRYO DOES NOT REDUCE GRAIN SIZE !! This is a high speed steel type in that it's secondary hardening elements will maintain hardness at high temperaturs as the tooling gets hot. Considering that the heat treatment given does not include cryo , it's probably not very beneficial. This is a complex steel and grain size will be small if you follow the heat treat recipe that is given with particular attention to temperatures.
 
Mark23

Interesting steel, that is. Looks like it will be incredibly tough stuff.

Regarding grainsize: If I'm not mistaken that's going to be established, before hardening. Cryo isn't going to effect that. So, if you want the finest grain, you should look into the process of normalizing. Which happens before hardening.

Some hi-tech steels come from the manufacturer with as fine as grain as you are going to get.

How this steel responds to cryo treatment? Well, it's not a HIGH alloy steel, so I don't know if it's even necessary - you'll need some testing there. The professional heattreating place I've used doesn't even bother cryo with D2 (higher alloy than CRV2) (I know somebody will argue with that, don't shoot the messenger, I'm just repeating what they say).

All it all looking at the application list, I think that steel would be great for a big chopper blade. Please let me know what your results with it are.

Steve
 
Sando said:
Interesting steel, that is. Looks like it will be incredibly tough stuff.
Click to expand...

This steel is very tough. The blacksmith whom I had asked to forge flat material (2" x 0.25") out of a rather bulky (3" x 1.25") billet swore like a trooper when he told me about it ... :D There is a similar steel in the US called "BEAVER" which has also Nickel in it.

There are quite a lot of professional heat treatment companies as well as knife makers who recommend and perform cryo treatment of D2.

Maybe I mix all it up, but AFAIK cryo treating a steel results in the steel becoming both harder and tougher to a certain extend. The "tougher" made me think it would also lead to a finer grain?

Thanks for the answers so far!

Best Regards!

Mark23
 
mete said:
CRYO DOES NOT REDUCE GRAIN SIZE !! This is a high speed steel type in that it's secondary hardening elements will maintain hardness at high temperaturs as the tooling gets hot. Considering that the heat treatment given does not include cryo , it's probably not very beneficial. This is a complex steel and grain size will be small if you follow the heat treat recipe that is given with particular attention to temperatures.
Click to expand...

Bohler Uddeholm recommends a sub zero treatment for one of their steels called "Sleipner", which similar in composition to the CRV2/1.2631. Further details on this, please see PDF file, especially page 6. You can also see that there is an increase in hardness for this steel when sub zero treated.

Thanks!

Best Regards!

Mark23
 
Mark23,

You are on the right track.

Yes you definately should expect an increase in hardness with cryo. That's what it's for: it will actually convert more steel to martensite. That doesn't mean that the grain is finer. It means you have more martensite.

Martensite is more 'difficult' to create in high alloy steels. Simple steels don't benefit from cyro because there is no (or very little) retained austentite. The more alloys the more cryo becomes necessary. But also, the better the job done in hardening the steel, the less necessary is cryo.

To use D2 as an example. If one company hardens D2 and there is a lot of retained austenite from their process, cryo is needed. Yet it is quite possible that another company, has a better process and cryo isn't an aid.

Steve
 
it will help the simple steels also,, they do it do cast iron too.
hell Stihl putts nitrogen in the their plastic handles on their Chain saws. :confused:

but it ends up,, is it worth the both/time/money with the little effect.
the steel companies that make the steel are the better judges for this.
we know it works on most, if not all the supper steels.

if you make the sandwich, you know what's in it right..at least you should :)
 
Mark, The Sleipner carbon content is .9% while the CRV2 is .5% that is a very significant difference .Usually if the manufacturer doesn't mention cryo it doesn't do that much.......BTW, For those who want to play with complex steels -take a look at the effect of austenitizing temperature on retained austenite for Sleipner!!! A 50 degree F difference raises retained austenite from 4% to 14% ! That's why I say that you MUST have accurate control for these steels .
 
Mete, OK, the carbon content differs, but Jerry Busse's proprietary INFI steel does also have a low carbon content of appr. .5% and Busse does a cryo treatment of some sort from what I have read in the forums.

AFAIK, a cryo treatment reduces the retained austenite content in case there is any left in the knife. As I have read somewhere else, cryo treatment could make up for at least some of the mistakes that could happen during "standard" heat treatment. This would be a good reason to do it as I want a very small amount of austenite in my knife. Even if the benefit will be very small, I would have a cryo treatment done unless it is likely to damage the knife/steel.

I agree with you that you have to be accurate on the temperatures.

Thanks for all the answers!!!

Best Regards!

Mark23
 
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