CPM D2 heat pre-heat/equalizing

E

Ethan Spalding

Joined
Mar 12, 2021
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Going by the heat treat instructions on NJ steel baron’s website, it says to pre-heat/equalize the CPM D2 at 1200 for 10-15 minutes, then 1400 for 10-15, then soak at 1850 for 30 minutes before plate quenching. My question is do I put the blade in the HT oven cold, allowing it to warm up with the oven? Or let it hit 1200 then put it in? And if so, after I put it in at 1200, does it stay in all the way up until the soak is completed?
 
Put it in once oven is at 1200, then leave it in for all cycles (don't remove between 1200 and 1400, etc)
 
I read the pdf, despite that, I don’t think you need any of that preheat equalize cycling.
If anyone has any evidence to support performance differences, I’m interested to know

maybe knifesteelnerds has a write up on D2, did you check?
 
Ethan Spalding said:
Going by the heat treat instructions on NJ steel baron’s website, it says to pre-heat/equalize the CPM D2 at 1200 for 10-15 minutes, then 1400 for 10-15, then soak at 1850 for 30 minutes before plate quenching. My question is do I put the blade in the HT oven cold, allowing it to warm up with the oven? Or let it hit 1200 then put it in? And if so, after I put it in at 1200, does it stay in all the way up until the soak is completed?
Click to expand...
Never put a blade in a cold furnace, always have up to a temperature first.
 
If you really want kickass try a prequench at around 1700 degrees, austenitize at 1900 degrees with a 30 minute soak, plate quench for a minute or two and then cryo. Temper to your hardness level according to your Rockwell readings.
 
Seedy Lot said:
If you really want kickass try a prequench at around 1700 degrees, austenitize at 1900 degrees with a 30 minute soak, plate quench for a minute or two and then cryo. Temper to your hardness level according to your Rockwell readings.
Click to expand...
Why? You should explain this.... what is a prequench and what does it do? What is the benefit and how do you know there is one?

If you just state something without the why and the how and what the benefit is, Then it just becomes some random statement like the guy who once said - I just sharpen my edge on the belt grinder with a worn belt....

i’m not picking on you...I’m asking you to educate us.
 
HSC /// said:
Why? You should explain this.... what is a prequench and what does it do? What is the benefit and how do you know there is one?

If you just state something without the why and the how and what the benefit is, Then it just becomes some random statement like the guy who once said - I just sharpen my edge on the belt grinder with a worn belt....

i’m not picking on you...I’m asking you to educate us.
Click to expand...

Why do you prequench AEB-L? Same set of factors involved. Grain refinemnt and pinning grain boundaries for improved hardness. Seems that many of the makers who speak of superior heat treat employ a prequench.

I have not yet used a prequench on D2 but have on M4 and AEB-L with an increase in hardness compared to the pieces that did not receive prequench. Big reason to try a prequench on D2 is Nathan's word on the subject.

Skip prequench if it does not suit you but cryo is defiantly a positive. Crucible metallurgists a while back wrote a paper on cryo and RA in a number of steels and D2 defiantly benefited.

Plenty of arm chair posters on this forum, i am not one of them...
 
It's not always an ace in the hole, it can change how much carbon and other elements go in solution so the austenitizing temp for hardening may need to be adjusted to avoid more RA by building hardness curves to see the pop and drop.

Seedy Lot said:
Why do you prequench AEB-L? Same set of factors involved. Grain refinemnt and pinning grain boundaries for improved hardness. Seems that many of the makers who speak of superior heat treat employ a prequench.

I have not yet used a prequench on D2 but have on M4 and AEB-L with an increase in hardness compared to the pieces that did not receive prequench. Big reason to try a prequench on D2 is Nathan's word on the subject.

Skip prequench if it does not suit you but cryo is defiantly a positive. Crucible metallurgists a while back wrote a paper on cryo and RA in a number of steels and D2 defiantly benefited.

Plenty of arm chair posters on this forum, i am not one of them...
Click to expand...
 
HSC /// said:
I read the pdf, despite that, I don’t think you need any of that preheat equalize cycling.
If anyone has any evidence to support performance differences, I’m interested to know

maybe knifesteelnerds has a write up on D2, did you check?
Click to expand...
Larrin has an article here with detailed analysis and heat treat recommendations with and without cryo.
 
DeadboxHero said:
It's not always an ace in the hole, it can change how much carbon and other elements go in solution so the austenitizing temp for hardening may need to be adjusted to avoid more RA by building hardness curves to see the pop and drop.
Click to expand...

"Don't cheat yourself, treat yourself" ;)

Yes coupons are ones friend.
 
Hubert S. said:
Larrin has an article here with detailed analysis and heat treat recommendations with and without cryo.
Click to expand...
yes thanks, I know it... I don't think there's any question regarding the use of liquid nitrogen. The OP is asking about pre-heat/equalize, and I'm saying it's not useful for thin knife blades.
 
Seedy Lot said:
Why do you prequench AEB-L? Same set of factors involved. Grain refinemnt and pinning grain boundaries for improved hardness. Seems that many of the makers who speak of superior heat treat employ a prequench.

I have not yet used a prequench on D2 but have on M4 and AEB-L with an increase in hardness compared to the pieces that did not receive prequench. Big reason to try a prequench on D2 is Nathan's word on the subject.

Skip prequench if it does not suit you but cryo is defiantly a positive. Crucible metallurgists a while back wrote a paper on cryo and RA in a number of steels and D2 defiantly benefited.

Plenty of arm chair posters on this forum, i am not one of them...
Click to expand...

I don't prequench AEBL... there's a point of diminishing returns for everything IMO, and I don't see AEBL as benefitting from a pre-quench, unless I've totally miunderstsood this article - https://knifesteelnerds.com/2019/03/04/all-about-aeb-l/

Digging into the D2 prequench I can see the benefit of a prequench given the data on reduced grain size...however I noticed that Larrin Larrin doesn't mention a prequench in this article - https://knifesteelnerds.com/2020/08/31/how-to-heat-treat-d2-psf27-and-cpm-d2/

I did not question the use of cryo.

regards
Harbeer
 
DeadboxHero said:
Never put a blade in a cold furnace, always have up to a temperature first.
Click to expand...
Can you explain why not? I've been cooking A2 primarily and was told by a few guys that it doesn't matter if you put it in the oven cold and bring up to pre-heat temp. So far I've hit my marks everytime with zero issues that I can tell. Or is this just a rule for D2?
 
A prequench was found to decrease grain size in D2 and M2 back in the day. The results can be found in the old Tool Steels book. However, in studies on AEB-L the improvement was small and the scatter in testing is wide enough that it isn't clear if there was a "true" improvement. As Shawn noted the prequench changes the heat treatment response some so it is important to be aware of that. With A2 steel the prequench did not provide a clear improvement. So it may be that the grain is being somewhat refined but that is not resulting in an obvious toughness benefit.
 
It is considered a poor practice to place a blade in a cold oven to heat up to a soak temperature. Ovens can overshoot the target temperature by hundreds of degrees for a short time, especially with the ramp rate set at 9999. Also, the blade can be heated higher than the oven temp due to radiant energy absorption during the rapid ramp. It isn't a guarantee that putting a blade in a cold oven will damage the steel or affect the final results, but the accepted metallurgical practice is to pre-heat the oven to the target and then add the blade.
 
Conventional D2 can benefit from a pre-quench. While the effect on grain refinement is documented, I'm not sure that grain refinement is the only attribute in play. As mentioned it does affect the heat treat response and in my experience this can play into other benefits. So yes, D2 can be pre-quenched and can have some benefits to it. CPMD2, on the other hand has not, in my experience, shown those same benefits as conventional D2.
 
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