Ranking of Steels in Categories based on Edge Retention cutting 5/8" rope

With my experience with the listed steels, I'd say that the mt19 is better than elmax, 154cm, and s30v so in my mind it's at least a solid category 4 and likely above. Those are just my non-scientific thoughts. I have only used it at a 14k grit polished edge so I don't know how it will handle 400 grit.
 
bodog said:
With my experience with the listed steels, I'd say that the mt19 is better than elmax, 154cm, and s30v so in my mind it's at least a solid category 4 and likely above. Those are just my non-scientific thoughts. I have only used it at a 14k grit polished edge so I don't know how it will handle 400 grit.
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Probably better than Elmax MT which was my WORST purchase ever. Elmax at 58.5HRC it is just plain nonsense.

Ankerson has demonstrated that Elmax at 60 is int Gr4 already, and IMHO at 61 would be in Gr3 probably.
At = Or >62 would be, per my experience in Gr2 or even 1.
IMHO it is quite unfeasible asking from a 12% Cr7C3 (D2 or alike) steel to deliver just as a 16%Cr7C3 2%VC (if the latter is PROPERLY HTd).
 
I dont see how a 1.5 point difference in hardness is that critical (60-58.5). The hardness is indicative of some other cause; a symptom if you will.
 
me2 said:
I dont see how a 1.5 point difference in hardness is that critical (60-58.5). The hardness is indicative of some other cause; a symptom if you will.
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It can make a big difference depending on the HT, both in Compression strength and at the higher tempering temps pulling more chromium into the matrix....

Both can make a large difference in performance.
 
nccole said:
Isn't the Rockwell C scale exponential?
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As a whole yes. However, the range of the scale used for knives is very nearly linear.

I was mainly referring to the notion that 58.5 was nonsense, however I see that Daberti is in Italy and there may be a translation issue, and in any case my reading of his statements was probably too literal. I just didn't see a jump from fairly bad to pretty good with just 1.5 points difference.

What is the difference between say 60 and 58 in terms of compressive strength? How narrow are the categories in terms of cut-off from one to the next higher or lower?
 
Oh, and just to be a picky SOB, higher tempering temperatures in stainless steels pull chromium out of the matrix, not into the matrix. I am curious about how that would make a large difference in performance?
 
me2 said:
As a whole yes. However, the range of the scale used for knives is very nearly linear.

I was mainly referring to the notion that 58.5 was nonsense, however I see that Daberti is in Italy and there may be a translation issue, and in any case my reading of his statements was probably too literal. I just didn't see a jump from fairly bad to pretty good with just 1.5 points difference.

What is the difference between say 60 and 58 in terms of compressive strength? How narrow are the categories in terms of cut-off from one to the next higher or lower?
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58.5 against lets say 61 it IS definitely a nonsense.
There is something that would clarify many concepts about heat Treatment: "Metallurgy of Steel for Bladesmiths & Others who Heat Treat and Forge Steel",John D. Verhoeven, Emeritus Professor, Iowa State University

Anyway, here we go. I've already posted here a link to Elmax datasheet.
It is nonsense to HT highly alloyed (high Cr, V, Moly, W, Nb Hypereutoctoid steels to 58.5 or even under 60 because:
1)Temperatures will be in a range where retained austenite will be pretty high. Many knifemakers know this and think it to be the best cost effective way of improving toughness for a given steel, but this way the edge will be gummy and prone to "wire edge issue".
The steel Matrix will be less capable of "trapping" effectively big primary carbides (D2 is an example of such carbides) and microchipping will be there every time a carbide of this kind will be on the very cutting edge. (a deep cryo will minimize retained austenite and thus increase HRC)

2)Austenization temperatures will be not optimal for "Particle Drag" and "Solute Drag" to deliver their best, which help avoiding austenite grain growth and thus toughness as well.

3)Aust. Temps will be roughly 1050°C and when Moly >0.8% and Cr >14 Cr23C6 weaker carbides will form in addition to harder Cr7C3 carbides. Getting rid of M23C6 carbides would improve Cr in solid solution (stain resistance) and C available for hardness.

So, in the end, you took me literally and I confirm you took me well :)
As I explained more than once in this thread, HRC alone will tell you how much of compression strength you will get. But with some metallurgical knowledge and informative datasheets you will be told aust./tempering temps, and make your own whole picture.
 
daberti said:
There is something that would clarify many concepts about heat Treatment ,,,[snip] ...

As I explained more than once in this thread, HRC alone will tell you how much of compression strength you will get. But with some metallurgical knowledge and informative datasheets you will be told aust./tempering temps, and make your own whole picture.
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:thumbup::cool: Why i love following this thread - so much awesome information pops up along the way and I'm sure to notice it without having to stumble around the forum looking.


I am looking forward to Jim's test results on the wonky S110V blades discussed in the other thread as well.
 
That was my point, though it should have been made with much less subtlety. There is more than one way to the same hardness, and not all are equal. The difference in hardness is just a symptom of the real issue that is causing the same steel at 58.5 to behave differently enough to be in a different category than when at 60. Unless some sort of microstructural threshold is crossed, which can happen, I still don't think just increasing the tempering temperature 25-30 degrees for that 1.5 HRc drop will make that big a difference, assuming everything else was the same (hardening, quenching, cryo, etc.).
 
me2 said:
That was my point, though it should have been made with much less subtlety. There is more than one way to the same hardness, and not all are equal. The difference in hardness is just a symptom of the real issue that is causing the same steel at 58.5 to behave differently enough to be in a different category than when at 60. Unless some sort of microstructural threshold is crossed, which can happen, I still don't think just increasing the tempering temperature 25-30 degrees for that 1.5 HRc drop will make that big a difference, assuming everything else was the same (hardening, quenching, cryo, etc.).
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It will make a difference in modern super-alloyed steels.
Lets make a comparison: I had a powerful hot-hatch with stock tyres which could by no means be driven properly. I had fully settable coilover springs and bumpers...I was getting nearly mad.
So I put on it track tyres homologated for Street driving as well. But these tyres required a bit (just a bit) of warm up. My daily commuting nearby Lake Como allows me to do proper warm up, with lotta winding roads.
Having a supersteel means Handling it for what it asks for.

Answering to your SH thoughts.
Lets get back to the D2 alternative Ankie is testing.
D2 has V and Moly just under 1%, C at 1.55%. Too less for a decent rewarding secondary hardening. We would be at a loss in hardness and toughness.
Now get Elmax: just same hardness (63) as if cryoed, but 43J of toughness. 0.15% more C, 2.2% more V and roughly same Moly. 6% more Cr.

Now my question for those who think that SH takes away so much Cr to stain resistance is: to reach such an high hardness we need quite some free carbon, right? If we can so C will not be tied up with so many secondary carbides (either Cr or V based), right? So where is the clue? At least in stainless steels by high austeniting (1080C and above) we've already dissolved a good amount of Cr based carbides so to speak.
If it 'd have been 1060°C it would be another story to be told. Just 20°C mate

Last but not least: SH minimizes Retained Austenite. Not everybody in the world is allowed to keep deep cryo equipment, so SH is quite important.
 
The increase from secondary hardening comes from 2 sources. First, as you said, the retained austenite is converted to martensite and then tempered during following tempering treatments. Second, the precipitation of carbides contributes to hardness. Those carbides, in stainless steels, are often chromium carbides and their precipitation will reduce the amount of chromium for corrosion resistance, while at the same time increasing hardness.

I can't help but think we are talking about 2 different things. Just raising the tempering temperature 25-30 degrees for a reduction of 1.5 points won't make a huge difference. Raising the austenization temperature the same amount can make such a difference, particularly with regard to retained austenite and how to get rid of it. You are also correct in terms of use of high tempering temperatures to reduce RA. Not everyone has access to cryogenic/cold treatments and some alloys are complex enough that cryogenic treatment won't be fully effective in removing/minimizing RA, so a high temper is needed. I don't know if the secondary hardening is really the intent, but the high temperatures for decomposition of RA may just coincide with the secondary hardening. If you can deal with the loss of toughness and corrosion resistance and/or don't have access to the cold/cryo, then high tempers are an option.
 
me2 said:
The increase from secondary hardening comes from 2 sources. First, as you said, the retained austenite is converted to martensite and then tempered during following tempering treatments. Second, the precipitation of carbides contributes to hardness. Those carbides, in stainless steels, are often chromium carbides and their precipitation will reduce the amount of chromium for corrosion resistance, while at the same time increasing hardness.

I can't help but think we are talking about 2 different things. Just raising the tempering temperature 25-30 degrees for a reduction of 1.5 points won't make a huge difference. Raising the austenization temperature the same amount can make such a difference, particularly with regard to retained austenite and how to get rid of it. You are also correct in terms of use of high tempering temperatures to reduce RA. Not everyone has access to cryogenic/cold treatments and some alloys are complex enough that cryogenic treatment won't be fully effective in removing/minimizing RA, so a high temper is needed. I don't know if the secondary hardening is really the intent, but the high temperatures for decomposition of RA may just coincide with the secondary hardening. If you can deal with the loss of toughness and corrosion resistance and/or don't have access to the cold/cryo, then high tempers are an option.
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I was talking about austenitizing temperature i.e. 1080°C vs 1060°C. 20°C differences in tempering are mainly trascurable.
Tempering at high temperatures really helps with RA, it is documented for Elmax, M390, even Vanadis 4E.
As a rule of thumb SH is rewarding in SS when C >1.6 AND Moly is at least 1%, V 3% (Nb, W are gladly welcome as well).
It is true that some Cr will be tied up in secondary Cr carbides, but V, W, Nb will limit this.
The precipitation of these carbides also leads to the dissolution of cementite (Fe3C) which itself it is a source of brittleness in the Martensite Matrix. This is possibly why S90V/comparable grade PM steels perform very well after SH: i.e. greatly reduced microchipping.
"Secondary hardening is caused by the formation of clusters of atoms of alloying elements and carbon (a maximum hardness often corresponds to the clusters) and the replacement of
relatively coarse particles of cementite by much more disperse precipitates of special carbides (TiC, VC, Mo2C, W2C). When these particles coagulate, hardness decreases.
The chromium additive causes a small secondary hardening. This is connected with a rapid coagulation of the Cr7C3 carbide at 550C (10208F) as opposed to Mo2C and especially W2C. During secondary hardening an increase in the yield stress is accompanied by an increase in toughness owing to dissolution of coarse cementite particles..........Secondary hardening is a result of the transformation of RA to martensite on cooling from the tempering temperature, and of precipitation of an ultrafine dispersion of alloy carbides.
Tungsten, vanadium , chromium, and molybdenum that are the strong carbide-forming elements are most commonly used to achieve secondary hardening.
To take advantage of their precipitation characteristics, they must be dissolved in austenite during the austenitizing treatment in order to be incorporated into the martensite formed during quenching with sufficient supersaturation for secondary hardening during tempering."
Source: Engineering - Steel Heat Treatment Handbook - Metallurgy And Technologies, 2Nd Edition - (George E Totten) Taylor & Francis Crc Press 2007
 
I'm curious to see the difference between PSF 27 and ingot D2 in Jim's type of testing. Not sure of the mules behind the edge thickness but as we know, it will effect the performance greatly .I hope it's in the 61 HRC range!
 
waterstoneblades said:
I'm curious to see the difference between PSF 27 and ingot D2 in Jim's type of testing. Not sure of the mules behind the edge thickness but as we know, it will effect the performance greatly .I hope it's in the 61 HRC range!
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It will be up today, cutting with it and that S110V Manix 2 I was sent...
 
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