CTS-204P question.

[gull wing]

I know it's been done before, but could you please list a Carpenter vs Crucible/ Japanese steel comparison.

[Donut]

Carpenter's 204P is similar to Bohler's M390, the grain structure is supposed to be a little finer than M390.

[Cliff Stamp]

It is the same steel by two different manufacturers.

The interesting thing about that steel, and it being popular is that its composition is in the same class as S60V which was one of the earlier vanadium rich steels. The patent information in later steels, and well established in the literature, is that combination of high carbon/chromium leads to an inferior steel because the chromium carbides are very soft compared to vanadium and thus contribute less to wear resistance (which is mainly dependent on carbide type/hardness) but have the same detrimental effect on toughness (as that is mainly dependent on carbide volume).

If you take these steels, take out the Vanadium and the carbon it carbides with you are left with the same steel as S60V with just 3% more chromium. The steel would thus be expected to have compared to S60V :

-lower hardening response (this can be seen in the tempering data)
-improved corrosion resistance
-reduced impact toughness
-reduced edge stability (but likely not significant as is small)
-reduced wear resistance

Considering the problems with S60V, and #1 and #3, it is odd to be excited about this steel as I don't remember any problems with corrosion resistance generally being reported with S60V.

[chuck_roxas45]

Wouldn't a tougher S60V be something to be excited about?

[Donut]

It sounds like he says it isn't as tough as S60V. Really, I haven't heard of anyone complaining about chippy M390.

I'm fairly impressed with M390, it seems like a reasonable steel.

Cliff, could the differences we are seeing when comparing the compositions and the reality have to do with particle and carbide size? I guess you could argue that we don't have consistent testing or consistent steel or consistent heat treating. :)

[Cliff Stamp]

If anything the impact toughness would be a little lower due to the large increase in chromium and chromium carbides. But all of these high carbide steels have very low impact toughness. The difference between them is so small that it could not be used to significantly effect choices in cutlery. They are so brittle that they are not even measured with the same impact toughness steels that the actual tough steels are measured. And even then, being able to gain toughness at the cost of wear resistance and hardenability is pretty standard, simply reduce the carbon content of S30V directly and you would achieve that (it would also become more corrosion resistant).

[DCDesigns]

Carpenter's 204P is similar to Bohler's M390, the grain structure is supposed to be a little finer than M390.

I think he already probably knows that. I believe he was looking for a composition chart...

[razorsharp]

Id just like to add that m390 has been very VERY good from my uses. Cutting up thick tin and aluminium and I got MINOR edge damage (few areas of flatness and carbide tearout ) I have cut up 2 meters of stereo wire into 5mm pieces and could slice paper with no hitches, ,. The only thing that did something bad to the edge was when I attempted a cut through a thin guitar string (size 13 E string) - the edge compressed and didn't chip out. This leads me to believe its pretty dang tough. What they forget to add in the data sheet is the extract of pixies

[chuck_roxas45]

Id just like to add that m390 has been very VERY good from my uses. Cutting up thick tin and aluminium and I got MINOR edge damage (few areas of flatness and carbide tearout ) I have cut up 2 meters of stereo wire into 5mm pieces and could slice paper with no hitches, ,. The only thing that did something bad to the edge was when I attempted a cut through a thin guitar string (size 13 E string) - the edge compressed and didn't chip out. This leads me to believe its pretty dang tough. What they forget to add in the data sheet is the extract of pixies

When it comes to super steel performance, the inconsistent heat treat bogeyman will always raise it's head. As Cliff said in another thread, it could be the placebo effect. :p

I too, am a victim of inconsistent heat treat, my M390 para and millie don't seem chippy at all. They do quite well by me. I really like this placebo effect. :D

[Brock O Lee]

Here is a study I found interesting. It compares the properties of M390, CPM420V (S90V), Elmax and a few other powder metallurgy steels (these steels are all used in the plastic mould industry).

Tempering temperature vs hardness can be seen in figure 3.

Wear resistance and toughness comparisons can be seen towards the end of the paper in figures 7, 8 and 9.

PM PLASTIC MOULD STEELS–WEAR RESISTANT AND CORROSION RESISTANT MARTENSITIC CHROMIUM STEELS

[Ankerson]

Considering the problems with S60V, and #1 and #3, it is odd to be excited about this steel as I don't remember any problems with corrosion resistance generally being reported with S60V.

I wouldn't go that far, S60V can't take the high hardness range that M390 and 20CV (62-63) can without having chipping issues. It had to be kept under 60 HRC (58 or so) so that really hurt the potential of the steels performance. If it didn't have those problems it could have really shown with that 5.5% Vanadium content especially at high hardness range in the 62-63 range.

S60V was a good idea that just didn't work out well for knife blades or should I say as well as it could have based on the alloy content.

M390 isn't chippy at all, even at high hardness and ground thin based on my testing on a variety of knives in different hardness ranges.

Getting ready to run yet another M390 knife though my testing process here really soon, CF Military.

[Cliff Stamp]

I wouldn't go that far, S60V can't take the high hardness range that M390 and 20CV (62-63) can without having chipping issues.

Jim,

The difference in those steels is a reduction in Vanadium of 1.5% and an increase in Chromium of 3%. That isn't a recipe for a drastic increase in the ability of a sharpened edge to resist chipping, in fact from the patent information directly and known metallurgy it is the exact opposite. This is why Chromium carbide volume is reduced to improve edge stability and toughness and there is a growing trend towards MC carbide volume (not just in stainless).

If there is a difference in experience between those two steels then it can't be attributed to the steel directly and inherent properties as there is no magic when it comes to how such alloy influences the properties, it is in fact spelled out in the patent information directly. One of the largest differences could simply be that the P/M process then and now has improved to the point that void and inclusion frequency/size is significantly less as direct statistics on compaction levels was very hard to obtain early on and no one really liked to address that concern.

Look at the state of the knife industry when S60V was used and look at the state now. At that time when it was still CPM-440V how much involved were discussions on steels with metallurgists from the industry? On the forums and when makers in general discuss steels what was the level of technical understanding or even just in discussions? There was a time when Paul Bos (and everyone else) used to use the high temper for ATS-34 and claimed it made a tougher knife (it was used simply because it avoided the need for cryogenics). This was not that long ago and it was only because people like Jim March pushed that the materials data clearly showed this was inferior for knives that there was a gradual switch to the low temper and cold quenches.

The part that I find curious about the promotion of those steels is that it directly contradicts the arguments used to promote other steels from the same manufacturers (i.e. the MC carbide issue). You can not argue on one hand that minimizing the large chromium carbide in favor of MC carbide improves edge strength/toughness and also say the opposite for another steel. This move S60V -> M390 is another example of reduction in wear for gain in grinding/machining which while no argument is valuable isn't exactly well reflected in the promotion, similar to S30V -> S35VN.

[Ankerson]

Jim,

The difference in those steels is a reduction in Vanadium of 1.5% and an increase in Chromium of 3%. That isn't a recipe for a drastic increase in the ability of a sharpened edge to resist chipping, in fact from the patent information directly and known metallurgy it is the exact opposite. This is why Chromium carbide volume is reduced to improve edge stability and toughness and there is a growing trend towards MC carbide volume (not just in stainless).

If there is a difference in experience between those two steels then it can't be attributed to the steel directly and inherent properties as there is no magic when it comes to how such alloy influences the properties, it is in fact spelled out in the patent information directly. One of the largest differences could simply be that the P/M process then and now has improved to the point that void and inclusion frequency/size is significantly less as direct statistics on compaction levels was very hard to obtain early on and no one really liked to address that concern.

Look at the state of the knife industry when S60V was used and look at the state now. At that time when it was still CPM-440V how much involved were discussions on steels with metallurgists from the industry? On the forums and when makers in general discuss steels what was the level of technical understanding or even just in discussions? There was a time when Paul Bos (and everyone else) used to use the high temper for ATS-34 and claimed it made a tougher knife (it was used simply because it avoided the need for cryogenics). This was not that long ago and it was only because people like Jim March pushed that the materials data clearly showed this was inferior for knives that there was a gradual switch to the low temper and cold quenches.

The part that I find curious about the promotion of those steels is that it directly contradicts the arguments used to promote other steels from the same manufacturers (i.e. the MC carbide issue). You can not argue on one hand that minimizing the large chromium carbide in favor of MC carbide improves edge strength/toughness and also say the opposite for another steel. This move S60V -> M390 is another example of reduction in wear for gain in grinding/machining which while no argument is valuable isn't exactly well reflected in the promotion, similar to S30V -> S35VN.

Cliff,

I tested another blade in S60V not long ago, a newer knife made not long ago and it still had the same old issues of chipping... At 59-60 HRC....

While S90V, S110V, 10V, M390, K294 all with much higher carbide volumes and much higher hardness (except S90V at 60) didn't have these issues, and in a number of knives.

Sometimes things just don't workout, S60V was just one of those times that it didn't work as expected.

That's not to say if they tweaked the Alloy content of S60V some that it wouldn't work....

[Sequimite]

Cliff,

I tested another blade in S60V not long ago, a newer knife made not long ago and it still had the same old issues of chipping... At 59-60 HRC....

While S90V, S110V, 10V, M390, K294 all with much higher carbide volumes and much higher hardness (except S90V at 60) didn't have these issues, and in a number of knives.

Sometimes things just don't workout, S60V was just one of those times that it didn't work as expected.

That's not to say if they tweaked the Alloy content of S60V some that it wouldn't work....

Empirical results trump theory.

[cckw]

I'm going to post something I have been wondering because it fits here well enough, no need for a new thread: what is the functional difference between M390 and Elmax ?

[Spook410]

It would seem that in the end, the science of metallurgy and test results have to match.

The Plastic Mould Steels report posted above concludes: "Considering the combination of all desirable properties of stainless tool steels, M390 shows the best overall performance." This was with Elmax and CPM420V in the running. It's hard not to be enthusiastic about a knife sitting in my pocket constructed of this material.

[Cliff Stamp]

I tested another blade in S60V not long ago, a newer knife made not long ago and it still had the same old issues of chipping... At 59-60 HRC.

Jim, I used a number of S30V knives which had chipping issues, and I can list a long list of other steels to report similar on, this doesn't mean I can then generalize about the steel or ignore basic metallurgy.

Who made the S60V knife, where did they get the stock, how was it rolled/normalized, how did they harden it, how did they sharpen it before you used it, etc. etc. .

Lots of makers used S60V without issues with durability, the only complaint that guys like Mayo had was that it was so hard to work.

There is no metallurgical data I have seen, which supports m390 being inherently durable as compared to S60V, and the actual argument/data from the manufacturers themselves in the patents actually as noted go the other way.

While you can not in theory ignore experiment, you also can not take an experiment and casually ignore theory without considering all the other possible factors which can cause the conflict.

[Ankerson]

Jim, I used a number of S30V knives which had chipping issues, and I can list a long list of other steels to report similar on, this doesn't mean I can then generalize about the steel or ignore basic metallurgy.

Who made the S60V knife, where did they get the stock, how was it rolled/normalized, how did they harden it, how did they sharpen it before you used it, etc. etc. .

Lots of makers used S60V without issues with durability, the only complaint that guys like Mayo had was that it was so hard to work.

There is no metallurgical data I have seen, which supports m390 being inherently durable as compared to S60V, and the actual argument/data from the manufacturers themselves in the patents actually as noted go the other way.

While you can not in theory ignore experiment, you also can not take an experiment and casually ignore theory without considering all the other possible factors which can cause the conflict.

I got a hold of some bad S30V also that the edge just fell apart so I know what you are saying.

Never saw a S60V blade that was worth a darn, either too soft or too hard, HT messed up etc.

That last one was a Slip Joint, was pretty good, but couldn't take 15 DPS without chipping out so I told the owner to use 20 DPS as it was pretty thin ground.