CPM Cru-Wear heat treat

AA Forge

Custom Knife Maker
Moderator
Joined
Apr 8, 2010
Messages
2,514
I apologize if this has been discussed on here before, but couldn’t find an old thread on it.

I am currently setting up to heat treat high alloy steels in shop and I’m considering trying CPM cru-wear.

My question is do any of you have a good heat treat recipe to start with? I looked over crucibles data sheets and was wondering if it is similar to 3V with the low tempering regiment being better for edged stability and corrosion resistance?

Thanks in advance!
 

AA Forge

Custom Knife Maker
Moderator
Joined
Apr 8, 2010
Messages
2,514
Thanks Larrin Larrin

So am I reading it right- 1950, plate quench, cryo, temper twice at 400 for 2 hours each should be 60-61RC?

How long should I hold at 1950?
 

AA Forge

Custom Knife Maker
Moderator
Joined
Apr 8, 2010
Messages
2,514
30 minute soak

So it actually has a pretty straight forward heat treat. I appreciate the input!

If anyone else has any tips to add I’m all ears! Really looking forward to giving this a try!
 
Joined
May 30, 2010
Messages
84
Gents, I need your advice.

I have a CPM Cruwear that was tempered twice at 1000 F. Hardness is fine with me but I want it to be a bit tougher. Is it okay to directly temper it again at a lower temp, that is 400 F, to improve toughness?
 
Joined
Apr 15, 2019
Messages
140
Gents, I need your advice.

I have a CPM Cruwear that was tempered twice at 1000 F. Hardness is fine with me but I want it to be a bit tougher. Is it okay to directly temper it again at a lower temp, that is 400 F, to improve toughness?

Looking at Larrin's data there is only a small increase in toughness using a low temper and cryo. I would say be happy with what you have. I have made hundreds of Cruwear knives with high temper and have have used my own very hard with zero issue and have had zero complaints from very happy clients.
 
Joined
Nov 7, 2012
Messages
4,430
Looking at Larrin's data there is only a small increase in toughness using a low temper and cryo. I would say be happy with what you have. I have made hundreds of Cruwear knives with high temper and have have used my own very hard with zero issue and have had zero complaints from very happy clients.
I agree.
I haven’t made hundreds but I’ve been making z wear for just over a year now and it’s more than suitable at the high temper.
I would leave it as is
 

AA Forge

Custom Knife Maker
Moderator
Joined
Apr 8, 2010
Messages
2,514
Looking at Larrin's data there is only a small increase in toughness using a low temper and cryo. I would say be happy with what you have. I have made hundreds of Cruwear knives with high temper and have have used my own very hard with zero issue and have had zero complaints from very happy clients.

what kind of edge stability does it have with the high temper in your opinion?
 
Joined
Apr 15, 2019
Messages
140
what kind of edge stability does it have with the high temper in your opinion?

I was perfectly happy with high temper edge stability. With identical knives I felt Cruwear had a little better edge stability than 3v but 4v was nociabley better then the other two. I sent the knives out for testing and the testers felt the same as they ran their own tests.

Now that I have switched to cryo and low temper i have not made any knives to compare high and low temper side by side.

Over hunting season I was using a little thin skinning knife in Cruwear, low temper, lots of abuse, like cutting through sternum cartlidge with plenty of bone contact on 4 deer and each time I was done I was very impressed with performance. The low temper with no secondary hardening was probably a factor but also with low temper it has been easier for me to dial in my knives to higher hardness so increased yeild strength was also a factor in the performance of the little Cruwear knife.

I switched to a cryo quench in my heat treat as I started using AEBL and it is easier for me to get liquid nitrogen than dry ice. Now I would not go back to high temper as I like being able to easily achieve higher hardness but I also really like running 2 tempers at 350-400 degrees instead of 3 tempers at 1000 degeees.
 

AA Forge

Custom Knife Maker
Moderator
Joined
Apr 8, 2010
Messages
2,514
I was perfectly happy with high temper edge stability. With identical knives I felt Cruwear had a little better edge stability than 3v but 4v was nociabley better then the other two. I sent the knives out for testing and the testers felt the same as they ran their own tests.

Now that I have switched to cryo and low temper i have not made any knives to compare high and low temper side by side.

Over hunting season I was using a little thin skinning knife in Cruwear, low temper, lots of abuse, like cutting through sternum cartlidge with plenty of bone contact on 4 deer and each time I was done I was very impressed with performance. The low temper with no secondary hardening was probably a factor but also with low temper it has been easier for me to dial in my knives to higher hardness so increased yeild strength was also a factor in the performance of the little Cruwear knife.

I switched to a cryo quench in my heat treat as I started using AEBL and it is easier for me to get liquid nitrogen than dry ice. Now I would not go back to high temper as I like being able to easily achieve higher hardness but I also really like running 2 tempers at 350-400 degrees instead of 3 tempers at 1000 degeees.

Thank you for the feedback! I plan to cryo and will probably set up a head to head high vs low temper as soon as I have a bar in hand. I must say I’ve never been to terribly impressed with 3V edge stability even with a low temper heat treat, so to hear cru-wear is better is good news to me!
 

AA Forge

Custom Knife Maker
Moderator
Joined
Apr 8, 2010
Messages
2,514
Out of curiosity, does the steel need to be wrapped or protected in anyway for the 1000f temper? I’m new to heat treating air hardening steels so I apologize if it’s a stupid question.
 
Joined
Apr 15, 2019
Messages
140
Out of curiosity, does the steel need to be wrapped or protected in anyway for the 1000f temper? I’m new to heat treating air hardening steels so I apologize if it’s a stupid question.

No wrap or protection for high temper needed.

I do not do much 3v anymore, probaly even less in the future. Right now steel line up is CD#1 at 60-61rc, CPM Cruwear in the 61-62rc range and if I want a little more hardness 4v at 64 rc.

I think you will find many of the PM tool steels to be very easy to heat treat. I will take wrapping in stainless foil to smoking oil smell any day.

Quench plates are very handy with the air hardening steels. I use two C clamps and clamp plates tight with blank still in foil for about 2 minutes, then cut blank out and get it in cryo in under 3 minutes total from pulling from oven.
 
Joined
May 30, 2010
Messages
84
Gents, thank you very much. Your feedbacks are really appreciated as these are wealth of information that give guidance to a novice like me.:):thumbsup:
 
Joined
May 30, 2010
Messages
84
Thanks Larrin Larrin

So am I reading it right- 1950, plate quench, cryo, temper twice at 400 for 2 hours each should be 60-61RC?

How long should I hold at 1950?

I am just curious what will we expect if we further go lower than the recommended tempering temp. of 400 f, say 300 to 375 f? Will it increase hardness and reduce toughness significantly?
 
Last edited:
Joined
Apr 15, 2019
Messages
140
I am just curious what will we expect if we further go lower than the recommended tempering temp. of 400 f, say 300 to 375 f? Will it increase hardness and reduce toughness significantly?

Lower tempering temperture does increase hardness and lowers toughness. Yet even when CPM Cruwear is at 64rc it still has plenty of impact toughness for most all chores.

Highly recommended you get Larrin Thomas's book "Knife Engineering".
 
Joined
May 30, 2010
Messages
84
Thanks for your reply.
I just hardened my CPM Cruwear at 1020 C /1870 F, 400 F, and showed around 59 HRC. I like hardness to increase to 60-61 with still great toughness. As you said, decreasing temp. temperarure will increase hardness. I might try 350 F.

Note: Most heat treatment companies in my country charges a very high price, be it for small or big job orders. So, they consolidate
job orders until it reaches the required minimum weight and heat treat it all together. The common hardening temperature is only 1020 C.
 
Last edited:
Joined
Jun 7, 2022
Messages
4
Thanks Larrin Larrin

So am I reading it right- 1950, plate quench, cryo, temper twice at 400 for 2 hours each should be 60-61RC?

How long should I hold at 1950?
I was wondering if you could go into a little more detail about your cpm cru wear heat treat process. I read the article having a hard time trying to get my head around it
 
Joined
Nov 7, 2012
Messages
4,430
Foil wrap blades
2000F furnace temp
Place foil pouch in furnace
Timer 45 mins.
Aluminum plate quench
Liquid nitrogen soak
Temper 1000F for two hours x2
Yields 63 rc

K Knife420Guy anything specific that you didn’t understand?
 
Top