Super duper CPM-s3v heat treatment recipe?

scott.livesey said:
A: Research indicates that dipping in liquid nitrogen is successful about 10% of the time.
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They're going to have be a little more careful in their statements than that for me to take them seriously. What "research" are they referring to? What types of samples were tested? What made it unsuccessful?
 
kuraki said:
Why? If the austentite->martensite conversion is being completed, where is the residual stress coming from that would cause it to crack? The Linde article you posted also indicates they don't predict it to be useful for simple carbon steels anyway. It is very interesting that sub-zero treated D2 was found to lose toughness, while cryo D2 was found to have increased toughness. That would lend towards the idea of cryo all the things and avoid sub-zero.
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With the fast quench, simply leaving the blade on a bench overnight can result in a blade cracking apart. There's a lot of stress in the matrix that needs to be relieved. Happened to me twice. 1095, hitachi white, and W2 all go immediately into temper from quench.

The article mentioned W steels, and 1095 is basically a W steel, unless they were talking about tungsten steels. I was pondering this last time I read it. I think the W2 that is over 1.2% carbon might be what they are referring to as there is potential for a lot of carbides.
 
kuraki said:
Why? If the austentite->martensite conversion is being completed, where is the residual stress coming from that would cause it to crack? The Linde article you posted also indicates they don't predict it to be useful for simple carbon steels anyway. It is very interesting that sub-zero treated D2 was found to lose toughness, while cryo D2 was found to have increased toughness. That would lend towards the idea of cryo all the things and avoid sub-zero.
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The thing to consider is the actual heat treat protocol. Different structures at different austenitizing temps might respond differently with sub zero compared to cryo. Mete or Larrin could better answer that though. I've been reading tool steels 5th edition, and there's a lot that I had no idea about 6 months ago. I'm trying to piece it together. The higher alloy PM steels are quite different to heat treat than simple steels.
 
Larrin said:
They're going to have be a little more careful in their statements than that for me to take them seriously. What "research" are they referring to? What types of samples were tested? What made it unsuccessful?
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go to the website and ask. these folks make the machines and also do the deep cryo. some is based on customer complaints like: "the wire you cryo'd for me worked well. I needed some in a hurry, so I put it in LN overnite. It didn't work. Why?"
 
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Just read through this thread.

*If you don't sub-zero or cryo quench, it's best to use austenitizing temperatures on the lower end of things

*Always temper immediately after the quench or following subzero/cryo quench

*contiuous cool down is necessary for most knife steels to benefit from cold treatments

*high speed steels can benefit from cold treatments even if there has been some time elapsed after quench and temper

*AEB-L produces m7c3 chrome carbides, also called C2 or K2 carbides
AEB-L benefits from cold trestments

*Cold treatments do not increase toughness

*Cold treatments do help prevent stubborn burrs that form after sharpening, makes them easier to remove

*Longer tempering times can also eliminate some retained austenite with a slight drop in hardness

*All steels have an optimum heat treat which may or may not include cold treatments
 
When I was researching dewars a ways back I came across a few manufacture statements that said above the LN surface up to the foam plug was -300°. I don't find it hard believe with how slow LN boils off in these tanks. If the nitrogen gas above the liquids was as warm as your buddy says I think we would loose a lot more then we currently do. I will see if I can dig up the info I found about the temps inside dewars. If you think about it logically LN sits at -321° and if the gas above it was -160° that's a huge diffrence which would boil off the LN quite quickly. I'm sure there is a way to actually calculate the temp if you factor in the evaporation rate in these dewars.

I don't think the quote about dipping steel in LN being only 10% effictive is correct. If you have ever dipped a blade in LN you know it takes awhile for the LN to stop boiling. The LN does not wet the surface till the blade has cooled down to LN tempature. Thy are saying it's shrinking the outside of the steel becaus its cold and the core is still hot. I find this kinda misleading and a good way to sell big expensive cryo systems. Steel conducts heat much faster then nitrogen and as long as the steel thickness is not some super thick huge block I don't see this being a problem. On steel blades in the thickness we use your not going to freeze the out side and have a warm core.

D2 is one of the steels that gains a HUGE improvement from cryo treatment. It's also a steel that needs the modified heat treat to really shine. I use to be kinda meph about D2 till I started tweaking the heat treat and cryo treating the blades. It's amazing how something so simple can create such a drastic difference in performance. A2 is also a steel that was at one time thought to not need cryo but later discovered it gains a good bit of performance from it. I cryo everything, why not I have the tank and LN.
 
To add to the mix == The formation of martensite creates high stresses which is tempered to relieve them. Cryo doesn't form eta carbides .It's the tempering that does it ! The cryo tweaks the matrix forming places for the eta carbides to form. That happens along specific crystal plains .
 
mete said:
To add to the mix == The formation of martensite creates high stresses which is tempered to relieve them. Cryo doesn't form eta carbides .It's the tempering that does it ! The cryo tweaks the matrix forming places for the eta carbides to form. That happens along specific crystal plains .
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I recently learned this talking with Phil Wilson. I always assumed that the ETA carbides were formed on the way down but Phil explained that the trip down just sets the steel up and the carbides are actually formed on the way back up during tempering.
I have come to the conclusion that I will NEVER figure all this stuff out. LOL
 
Me too !! Apparently some have confused things and done a high temp ,900 F, after cryo ! That will certainly mess up the eta !
 
"Toughness" as it relates to knives is not always well understood by folks. "Toughness" as defined by joules of energy absorbed in a fracture impact does not correlate well to durability in rough use. In my experience, 3V is more durable in rough use with a HT that includes cryo. That's only one ingredient in the soup, but I'd be skeptical of a 3V recipe that skips cryo whether it increases "toughness" in a charpy v notch test or not.
 
Larrin said:
By saying that the paper "discusses it," you mean they are reporting that most research points to a reduction in toughness, correct?
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Is that what you read in that paper? The findings vary.
 
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AVigil said:
Is that what you read in that paper? The findings vary.
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"It is commonly accepted that the reduction of retained austenite content decreases fracture toughness of ferrous materials [122].. Das et. al. [70] studied on Influence of sub-zero treatments on fracture toughness of AISI D2 steel they concluded that, In general, sub-zero treatments reduce fracture toughness of the selected steel as compared to that of the conventionally heat treated ones. However, the degree of reduction in fracture toughness varies with the types of sub-zero treatments; it is lowest for deep cryogenically treated specimens but highest for shallow cryogenically treated ones..
Similar observations related to reduction of toughness by deep cryogenic treatment over conventional heat treatment has been reported for 4340 steel by Zhirafar et al. [22], En31 steel by Harish et al. [88] and for D2 steel by Collins and Dormer [15], Wier-szyllowski et al. [90] and Rhyim et al. [89]. Only Cajner et al. [98] and Molinari et al. [33] have reported the effect of deep cryogenic treatment on the variation of fracture toughness, though estimated by non standard approaches. Cajner et al. [98]have reported marginal reduction of fracture toughness of PM S390 MC high speed steel, whereas in sharp contrast Molinari et al. [33]have reported considerable improvement in fracture toughness of AISI H13 steel by deep cryogenic treatment over conventional heat treatment.. Zhirafar et. al. [22] studied on the mechanical properties of 4340 steel they concluded that, by employing the cryogenic treatment showed slightly detrimental effects (14.3% decrease) on the impact energy toughness prior to tempering. The fracture features of steel subjected to the cryogenic treatment showed less shear lips compared to the conventionally treated ones, indicating less energy absorption. However, Senthilkumar et. al. [74] studied on 4140 steel and they concluded that, the toughness of the 4140 steel is not significantly influenced by SCT and DCT samples with respect to CHT samples. These results are agreement with the result obtained by Kollmer [99] also could not find any significant improvement in toughness while DCT on 4140 cold-rolled steel."
 
Larrin said:
"It is commonly accepted that the reduction of retained austenite content decreases fracture toughness of ferrous materials [122].. Das et. al. [70] studied on Influence of sub-zero treatments on fracture toughness of AISI D2 steel they concluded that, In general, sub-zero treatments reduce fracture toughness of the selected steel as compared to that of the conventionally heat treated ones. However, the degree of reduction in fracture toughness varies with the types of sub-zero treatments; it is lowest for deep cryogenically treated specimens but highest for shallow cryogenically treated ones..
Similar observations related to reduction of toughness by deep cryogenic treatment over conventional heat treatment has been reported for 4340 steel by Zhirafar et al. [22], En31 steel by Harish et al. [88] and for D2 steel by Collins and Dormer [15], Wier-szyllowski et al. [90] and Rhyim et al. [89]. Only Cajner et al. [98] and Molinari et al. [33] have reported the effect of deep cryogenic treatment on the variation of fracture toughness, though estimated by non standard approaches. Cajner et al. [98]have reported marginal reduction of fracture toughness of PM S390 MC high speed steel, whereas in sharp contrast Molinari et al. [33]have reported considerable improvement in fracture toughness of AISI H13 steel by deep cryogenic treatment over conventional heat treatment.. Zhirafar et. al. [22] studied on the mechanical properties of 4340 steel they concluded that, by employing the cryogenic treatment showed slightly detrimental effects (14.3% decrease) on the impact energy toughness prior to tempering. The fracture features of steel subjected to the cryogenic treatment showed less shear lips compared to the conventionally treated ones, indicating less energy absorption. However, Senthilkumar et. al. [74] studied on 4140 steel and they concluded that, the toughness of the 4140 steel is not significantly influenced by SCT and DCT samples with respect to CHT samples. These results are agreement with the result obtained by Kollmer [99] also could not find any significant improvement in toughness while DCT on 4140 cold-rolled steel."
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One paper you mark in red showed no difference. The other showed a "considerable improvement" when cryogenic processing was used, and the authors even say that is is in "sharp contrast" to the rest of the cited papers, which all showed a decrease in toughness. That is not what "the results vary" means. The whole point of these review papers is to see where the overall research is pointing, so that outlier papers don't receive all of the attention.
 
Like I said... "The findings vary"

You can not take research on different materials and methods and apply it across the board. More research needs to be done.

Cherry picking is not what the paper is about, reading the conclusion of the paper is always a good place to see what they think of the data they reviewed.
 
AVigil said:
Like I said... "The findings vary"

You can not take research on different materials and methods and apply it across the board. More research needs to be done.

Cherry picking is not what the paper is about, reading the conclusion of the paper is always a good place to see what they think of the data they reviewed.
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It's ironic that you are accusing me of cherry picking in this scenario.
 
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