Heat treating CPM M4 ???

[C.Pettersen]

I just got done reading a very interesting write up on CPM M4 ( See Dec 06' BLADE). I am curious to know about heat treating this particular steel. Is it the same tecnique as say O-1 toolsteel ?

The write up on this new steel seems rather promising, and would like to try my hand at using some of this steel for my own evaluation.

I think its realy good to see a new carbon steel come into to light. I do like stainless steel as well, but have always been partial to carbon steel ( particularly O-1 and 5160 ) so this is CPM M4 is some interesting news to me.

[Jack Davenport]

Good morning Mr. Petterson: Warren Osborn can talk to you about CPM-M4
he has some experience in the cutting competition trail and has some views on this new steel. talk later Jack Davenport. Also you can get the heat treat schedule from crucible's web site.

[C.Pettersen]

Thanks Jack.....I just checked Crucible's data sheet on the material....very good information.

I still would like to hear from Warren or anyone else who has used this material for their own input and or tips.

Now I just need to get a hold a small amount to see if I realy want to travel down that road.

[Warren Osborne]

Hi Mr Peterson,
Glad you enjoyed the aticle on CPM M4. There are two different types of the M4 .One is conventional & the other is CPM M4.We are talking about the latter.
This is a high speed tool steel With some hi heat qualities (IE tungston) & is very tough stuff in usage as well as to work in the heat treated condition
CPM M4 cannot be forged in a conventional manner.It can be sanwiched between two pieces of softer material but to try to forge a blade out of it is extremely difficult & for me a waste of A LOT of time.There is only a very short widow to forge in & it will crack & crumble below & especially above that window.
We use CPM M4 for Cutters mainly & they perform better than any steel Ive used so far. I havent tried 5160 or 52100 but have just about exusted my ability to keep experimenting with most other steels.As far as the hi carbon steels 1086V does very well & is probably better than 01.
As for smaller knives CPM M4 will take a finer edge & hold it longer than any steel Ive used in my knifemaking career.However it is also the toughest Ive used in the hardened condition.There are probably worse steels to work but i dont wish to make knives out of them.
Heat treating . M4 is generally very stable in heat treating & can be autenized from 1850 to 2000 plus degrees.This is great for us.It does air cool & performs very well by doing so. (Forced air ).Generally I austenize at 1975 , hold for 30 mins & cool with forced air.I then draw at 1025 for two hours take it out & test for hardness. I draw again for two hours at between 1000- 1025 depending on how hard I wish it to be .The second temper will not soften dramatically at all but you could lose a point in hardness.The blade should rockwell at around RC 60- 61.
I have knives at RC 58 & they perform very well as cutters .I like them a point or two harder especially for folders & hunters.Aircooling is okay but Id probably be correct in saying that a blade heat treated where salt ,oil or atmosphere quench can be used will produce an even better blade with higher hardness.DO NOT DECARB OR SCALE M4 , you;ll be sorry!!!!

Hope this helps
Warren