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m390, elmax, s90v : a little reality

Posted by CliffStamp 
m390, elmax, s90v : a little reality
December 04, 2012 06:33PM
Recently, for some odd reason, a lot of metallurgy has been ignored in the promotion of certain steels, m390 and elmax are the worst examples. These are mold steels, designed for high wear on abrasive materials where corrosion resistance is required. They are not designed for cutting tools, and more importantly they are not optimized for abrasion resistance and toughness as is often implied.

A little bit of history, when Crucible came out with S60V (440V) it set a very high standard for abrasion resistance for a stainless mold steel. However after a significant amount of research Crucible (and others) noted that if the carbide volume was maximized for MC type and the chromium rich carbides were minimized then a similar wear resistance could be obtained at a higher toughness.

This is because toughness is correlated to total carbide volume, but wear resistance is correlated to the hardness of the carbides. and thus MC carbides can produce a higher wear resistance and increase the toughness at the same time.

Now m390 and elmax do not do this, they instead use a very high amount of chromium vs the very high vanadium in S90v, what is the effect of this, they have a much LOWER wear resistance to toughness ratio. To be specific, at the same toughness at S90V they have about half the wear resistance, they are not in the same class.

This would be expected because m390 and elmax are similar S60V modified to lower the vanadium content. The only advantage they have over S90V (for high carbide steels) is that they have higher corrosion resistance - otherwise they are simply easier to manufacture and have an inferior wear/toughness ratio - again which they have to have by basic metallurgy.

Note as well, in regards to the low toughness of S60V, the toughness of elmax, m390, s90v etc. is not a tremendous amount increased over S60V. for perspective, the difference is LESS than the difference between D2 and A2. It is hardly the case that one of these can be an extremely tough steel and the other extremely brittle.

Thus if you want a steel which has a much lower wear resistance with slightly increased toughness over S60V, then m390 and elmax can be a solution -or- if you want a steel which has similar toughness, much less wear resistance but higher corrosion resistance than s90v, they can also be a solution.

A few references :

S60V sheet : [www.alphaknifesupply.com] and [www.crucibleservice.com]

S90V sheet : [www.crucible.com]

3V sheet : [www.zapp.com]

Research on plastic mold steels : [www.kau.se]
me2
Re: m390, elmax, s90v : a little reality
December 04, 2012 07:52PM
And I rather liked s60v, though I havent tried m390 or elmax.
Re: m390, elmax, s90v : a little reality
December 04, 2012 08:29PM
The history on S60V has seen a lot of revisionist alteration as well, claims now that it was difficult to harden - it has the same response as 440C, which is even stated in the original data sheet. A soak at 1950, oil/salt, gives 58 HRC after a low temper without extending the quench to cold, doing so gains 1-2 HRC points, again the same as it does in 440C.

The advantage of S60V due to the PM nature and more importantly the very high vanadium is that it can tolerate a higher soak and thus a 2050 soak, +oil/cold can give 62 HRC and an extremely high wear, very high corrosion resistance. However that requires a lot higher QC than most would have because as you increase temperature you have to have much less slop in the temperature/time and you absolutely have to use a forced quench and cold to prevent issues with precipitation in cooling and retained austenite.

The problem is that there is too much metallurgy=kryptonite in the knife industry. For those that used it as it was designed to be used, the performance was extremely positive, the most extreme would be Tom Mayo who used it in skinners for hunting guides and it was the highest performing blade he seen, quoting blades commonly lasting a season and literally dozens of animals. Now to be clear, the blades were extremely dull at the edge of the season, this isn't shaving, not even paper cutting, they were worn smooth.
Re: m390, elmax, s90v : a little reality
December 04, 2012 11:33PM
I thought I posted this here, but I guess I didn't.... confused smiley




Been wanting to do this for awhile, a direct straight edge retention comparison between these two steels. They are very close in performance, closer than some would believe. Both knives are CF Sprint run Military's sharpened to 400 grit Congress Moldmaster finish at 15 degrees per side. This leaves IMO the optimal edge finish for maximum edge retention and cutting efficiency.

The Test:

Slicing 5/8" Manila rope checking every 20 cuts for down force and cutting was continued until 20 LBS was reached. Starting force was 11 LBS for both knives and after 20 cuts both knives were at 14 LBS.

Hardness as tested.

M390 - 61 HRC

S90V - 60 HRC

The Steels:

M390

C - 1.9%
Mo - 1.0%
Si - .70%
W - .60%
Cr - 20%
Mn - .30%
V - 4.0%

CPM S90V

C - 2.30%
Mo - 1.0%
Cr - 14.0%
V - 9.0%

M390

Cut aggressive with the edge finish and took some edge damage as expected as all steels have, it was still sharp enough to slice printer paper after testing.







CPM S90V

Very Aggressive with the edge finish and as with M390 it took some edge damage, but slightly less. Sharp enough to slice printer paper after testing.








Knives together.








Results:

Both knives performed extremely well as expected with S90V over M390 in the end by 21% or 460 to 380 cuts.

Very close as I expected it to be, under normal use most wouldn't be able to tell them apart depending on actual use unless they were pushed to the limit of edge retention. In that case the added Vanadium content of S90V at 9% over M390 at 4% would take over.
Re: m390, elmax, s90v : a little reality
December 05, 2012 02:10AM
Somehow I have a feeling that only a limited audience would accept this, even with the test results provided, on a larger forum.
It is interesting however that most often Elmax is seen in the rank of S30V, S35VN and 154CM
Re: m390, elmax, s90v : a little reality
December 05, 2012 12:55PM
Quote
styx
It is interesting however that most often Elmax is seen in the rank of S30V, S35VN and 154CM

That is because that is where it does rank according to the actual materials properties thus in general you would expect the majority of people to have that experience with the normal variance expected.

It isn't surprising that they would not be significantly different in Jim's work because of the precision of his measurements. If you are measuring sharpness on a scale by cutting the hemp then the most you can get is about +/- a pound. Even if the scale is more precise, the force can change by that much due to the hemp itself and even during a single cut it will vary by a lot more than a lbs. Normally you would take the peak force during a cut as the force measurement.

Given that your precision is thus a pound or so this means that your final stopping point of 20 lbs is actually the range from when the knife first started to hit 20 lbs until the moment all cuts were over 20 lbs. Because the cutting is done to a very low sharpness, about 10%, this is in the plateau region and would be much > 100 cuts, i.e. the steels would have to be VERY different to separate with such work.

Even this is a over estimate as you will also get variance from the hemp itself, the initial sharpness, the speed of the cutting, etc. and other issues, so a more realistic estimate is about twice that. If you do repeated trials and use a centering statistic you can reduce that, but given you are in the plateau your precision will always be very low.

To give you some perspective, even CATRA machines can not tell apart very small difference in steels because even the tolerance on the initial sharpness from the jig/machine alone can make a 10% difference.
Re: m390, elmax, s90v : a little reality
December 05, 2012 01:18PM
Quote
styx
Somehow I have a feeling that only a limited audience would accept this, even with the test results provided, on a larger forum.
It is interesting however that most often Elmax is seen in the rank of S30V, S35VN and 154CM

That's likely due to the finial hardness being kept in the 59-60 range so yes ELMAX, S30V, and S35VN will be close enough to each other given that.

The advantage of ELMAX really starts once it's taken over 60 HRC getting into that 61-62 HRC range, that's speaking about edge retention. There is a rather large difference in performance from that 59-60 range to 61-62 range, that's having tested knives in ELMAX from 58.5 HRC to 62 HRC... Tested hardness.

Also look at MOST of the knives available in ELMAX, they aren't exactly efficient cutters as thick as they tend to be at this point anyway, that also hurts the performance.



Edited 3 time(s). Last edit at 12/05/2012 02:03PM by Ankerson.
Re: m390, elmax, s90v : a little reality
December 05, 2012 02:24PM
Thanks for clarifying that.
And yes it's an unusual trend that "newer" steels in knives are quite thick. Maybe not enough testing and just not wanting to risk getting a lot of damage reports?
Re: m390, elmax, s90v : a little reality
December 05, 2012 03:01PM
Quote
styx
Thanks for clarifying that.
And yes it's an unusual trend that "newer" steels in knives are quite thick. Maybe not enough testing and just not wanting to risk getting a lot of damage reports?

I think it's the types of knives in general they tend to be used in, except for M390, they tend to be on the thinner side.

We will have to see what happens as time goes on, hopefully the blades will get thinner or should I say the grinds.
Re: m390, elmax, s90v : a little reality
December 05, 2012 06:50PM
Quote
Ankerson

The advantage of ELMAX really starts once it's taken over 60 HRC getting into that 61-62 HRC range, that's speaking about edge retention. There is a rather large difference in performance from that 59-60 range to 61-62 range, that's having tested knives in ELMAX from 58.5 HRC to 62 HRC.

Jim there is no significant difference in materials properties in Elmax in that range, neither in resistance to deformation/rolling, nor in wear, there could be no significant difference in edge retention which is thus dependent on those properties. This is born out by the fact that CATRA data is available on exactly that and the difference is so small that a CATRA machine can barely detect a difference. Are you really saying that any normal person using two knives can detect a difference which of a range comparable to the limits of a CATRA machine and further that is a "rather large difference". Note as well that the CATRA results are only able to be detected again when the sharpness is extremely low and the force and/or length of blade being used to make the cut is 10X that of a sharp blade.
Re: m390, elmax, s90v : a little reality
December 06, 2012 02:49AM
Quote
CliffStamp
Jim there is no significant difference in materials properties in Elmax in that range, neither in resistance to deformation/rolling, nor in wear, there could be no significant difference in edge retention which is thus dependent on those properties.
What are your sources?
(honest question, I've done a quick search and haven't found much except the Uddeholm fact sheet which has limited data regarding 60+ hardness).
Re: m390, elmax, s90v : a little reality
December 06, 2012 02:19PM
Cliff

Would you take into consideration buying yourself a Blue M390 Paramilitary2 from BentoBoxShop ? as its coming out again. I think you are wrong, and that M390 wouldnt have half the wear. I know its less wear resistant, but I would think only by 25-15 % . I reckon the steel will surprise you. It takes a kickass aggressive edge, its a really nice performer.

I have found m390 to hold an edge longer than my S30v and Superblue. Now elmax compares to s30v at lower hardnesses of 59-60 and should be similar to Superblue at 61-62 , looking at Jim's data.

I haven't got any S90v yet, but once I do, ill be comparing the steels, though it might be an unfair test,what ever S90V knife I get would have to be thin behind the edge or reground as thin as my reground Para to be a good comparison. Id be testing a 10/side edge with a 600 grit microbevel a 15 degrees. I should be able to afford something in S90V when I have a job. (Making full time pay , not paying rent- ill have a fair amount of spare money)
Re: m390, elmax, s90v : a little reality
December 06, 2012 03:04PM
Quote
bubo
What are your sources?

It can be calculated from the information in the original patents from Crucible where they show how abrasive wear resistance is correlated to MC carbide volume. It is directly measured in the paper reference in the original post.

Quote
rs-Travis
I think you are wrong, and that M390 wouldnt have half the wear. I know its less wear resistant, but I would think only by 25-15 % .

These are measured quantities, in general when I talk about aspects of steel and especially when I am quantitative this is all based on known values, it isn't my opinion, it is always supported by published data or known theory or both, and then correlated as well to work I have done and the work of others. You don't need to take my word for it of course, just read the sources given in the above.

I am going to get Kyley to make an Elmax kitchen knife next year, assuming he is interested in the project.

Quote

I should be able to afford something in S90V when I have a job.

Just make one, getting the steel won't cost you anything, then it is just your time the cost to HT, $20-$40 depending on batch tolerances.
Re: m390, elmax, s90v : a little reality
December 06, 2012 07:33PM
Quote

I am going to get Kyley to make an Elmax kitchen knife next year, assuming he is interested in the project.
That would be cool.

Quote

Just make one, getting the steel won't cost you anything, then it is just your time the cost to HT, $20-$40 depending on batch tolerances.

HT would have to be in USA, unless a place does it here. I know one place SSM has HT services. but I dont think they would do S90V. Which means the knife would be sent to USA at the cost of 12USD, and will cost 17 coming back, plus costs of belts, materials, HT... gets pricey eh? haha. Thats a reason knife making hasnt been on my side. But that is a good idea.
Re: m390, elmax, s90v : a little reality
December 06, 2012 08:09PM
Use Kyley's source, I can't imagine that is in the US. S90V isn't overly demanding to HT, far easier than any HSS for example which any professional HT service can do easily. There is a lot made about the difficultly of hardening these steels but it is just marketing. s90V can be austenized at 2050F, oil quench + cryo and reach 60+ HRC. In comparison M2 austenizes as 2250 F, extremely demanding on furnaces.
Re: m390, elmax, s90v : a little reality
December 06, 2012 11:33PM
Quote
bubo
Quote
CliffStamp
Jim there is no significant difference in materials properties in Elmax in that range, neither in resistance to deformation/rolling, nor in wear, there could be no significant difference in edge retention which is thus dependent on those properties.
What are your sources?
(honest question, I've done a quick search and haven't found much except the Uddeholm fact sheet which has limited data regarding 60+ hardness).


CATRA results.

[www.bucorp.com]
Re: m390, elmax, s90v : a little reality
December 07, 2012 05:00PM
Jim, that CATRA data does not show a significant difference, it is a marketing table, not a materials resource. I have posted raw CATRA data before, you can get 10% of a difference in 60 cycle CATRA runs on the same blade simply due to the inherent variation in the testing methods even when the blades, sharpening, etc. are all machine ground/sharpened to precise tolerances.
Re: m390, elmax, s90v : a little reality
February 07, 2013 03:58PM
How come M390 gets such great reviews then? I have not used it but it seems to be significantly better than S30V. The problem is, noone says by how much!
Re: m390, elmax, s90v : a little reality
February 07, 2013 04:51PM
Because people are forming conclusions with proper methods and preconceived notions are dominating.

If you want to see a non-knife example of the same type of logic/reasoning then spend sometimes on BodyBuilding forums and read the arguments about nutrition, supplements, etc. .

A friend of mine, intelligent person, is convinced that green tea makes her constipated because one time she drank green tea and the next day she was constipated so she avoids it like the plague, sounds silly, but it is the same thing.



Here are a couple of threads :

-[www.spyderco.com]

-[www.spyderco.com]
Re: m390, elmax, s90v : a little reality
February 07, 2013 05:01PM
I'd like to add M4 to this discussion. The following YT video is interesting. My understanding of what the author of the video is saying, is that M4 has better edge retention (on a practical level) than some of these other powdered steels because it has greater toughness. Please correct me if I am wrong.



cKc
Re: m390, elmax, s90v : a little reality
February 11, 2013 03:19AM
Quote
CliffStamp

I am going to get Kyley to make an Elmax kitchen knife next year, assuming he is interested in the project.

how about one of my 5" or 6" chef knives? grinning smiley very versatile and not quite such a bastard to grind. I'm going to sell my 9.5" aebl blade soon..

I have just jerry rigged an elmax folding blade and bolted a fix handle on for sending out for testing..

it was going to go to smokeeater, but Bruce said he would sent SE a test knife.. I'm happy to ship the folder blade to you to try as I believe the heat-treat is different from many. This was dont with Cryo, triple temper, and tempered at the 500c range to 60rc.

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[data.gearbastion.com]
KnivesAndStuff (YoutTube)
Re: m390, elmax, s90v : a little reality
February 11, 2013 12:42PM
If you are selling the 9.5" AEBL, then let me know the cost on both of them.
cKc
Re: m390, elmax, s90v : a little reality
February 12, 2013 04:30PM
Quote
CliffStamp
Use Kyley's source, I can't imagine that is in the US. S90V isn't overly demanding to HT, far easier than any HSS for example which any professional HT service can do easily. There is a lot made about the difficultly of hardening these steels but it is just marketing. s90V can be austenized at 2050F, oil quench + cryo and reach 60+ HRC. In comparison M2 austenizes as 2250 F, extremely demanding on furnaces.

Quality Heat-treat can heat-treat it.. but it wont be cheaper than shipping to USA if Travis only wants one knife done. They are an industrial heat-treater, so they do everything by volume with a minimum volume cost of 10kg.. so the heat-treat on S90V would be about $180+gst

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[data.gearbastion.com]
KnivesAndStuff (YoutTube)
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