S30V: What are your experiences with this steel?

i see. it seems like s30v is very very finegrained if its really astm 16 or 20. ive read somewhere the grainsize of powdermetal steel is about 3micron or so, dont remember where though or if its correct
 
Well, on the little excerpt that Landes has made available for his "Scheidenmodell" and of which he says, he picked a representable section, S90V shows a carbide grain sizes of about 2 microns with aggregates of carbides as large as 5 microns, but nothing larger. To put this into perspective, the same sheet shows O1 with a grainsize of about 0.7 microns and no aggregation. So the ASTM numbers seem a bit large but not completely out of proportion especially not on the low end and especially if you consider that the carbide volume of S30V is substantially smaller than that of S90V.
 
HoB said:
To put this into perspective, the same sheet shows O1 with a grainsize of about 0.7 microns and no aggregation.
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Grain size and carbide size are different, the grain size is the size of the crystal structure of the matrix, the carbide size is of the precipitates in the matrix. The grain size of O1 with standard heat treatment is about 9 on the shepard fracture test which according to Allen is the same as the ASTM G value, the carbide size is sub micron.

The carbides are formed in and around the grains and which are much larger. The reason that O1 and similar steels have such small carbides is that there is essentially no alloy carbide and cementite forms very tiny carbides. 1.2562 is basically a high wear version of O1 which has tungsten alloy carbides and they are in the microns and of very high volume. It is a very high wear cold work steel.

But again, what I am interested is not the theory of what the ideal steel looks like, it is the structure of the steel in the knives which have been prone to chipping. Was the grain size blown in the hardening, was there excessive secondary carbide precipitation, is the steel extensively microcracked, etc. .

-Cliff
 
Cliff Stamp said:
Grain size and carbide size are different, the grain size is the size of the crystal structure of the matrix, the carbide size is of the precipitates in the matrix. -Cliff
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Yes, I actually know that, but it's good you point that out. It seems that these terms are often used interchangeably. It seems a lot of people talk about grain size or "fine grained" steel, when they actually refer to the carbide size. It seem to me, that maximum grain size and minimum carbide size should be the ideal combination...which of course is not possible with a high carbide volume, since the carbide volume should limit maximum grain size (well except of course, if all the carbide is sitting around in large clumps).

Well, I think the ideal structure for a steel is important as reference point. I think what you really would want to compare is how the micro structure in the problematic blades is different from an ideal structure.
 
You generally want the minimum grain size as it increases strength and toughness, finer grain lowers hardenability but this is more for large parts which are air hardened and not the very slim cross section which is in knives. Carbides you generally want maximum dispersion to get maximum edge stability stability and consistency of structure and this will mean minimum size by default.

-Cliff
 
I think s30v is overrated. And hair poping sharp is NOT the proper edge to have on a knife.Itll NEVER stay that sharp. purly for showing off. and paper cutting is the worst thing for a blade. itll dull it quicker than sanyhting else. For a actual using knife, id get it poping sharp and then add a VERY slight alternate back bevel, like what one would do on a wood chisel, cuz then itll stay sharp much longer,and definatly WONT chip. I have had complwte success with this method. If yoy do this i can guarantee you the s30v will impress you. But ill say again, Nothing stays hair poping sharp for long. any custom maker will tell you this. you should be able to shave hair,of course.but theres a practical limit. I know, we all like to see how sharp we can get our knives,but if you just add a slight back bevel(say one or 2 very slight strokes at a shallower angle(careful not to press too hard,better to go lighter than harder,definatly. try it a few times,and youll get the hang of it.and that baby will stay sharp for a loooong time.a few strops here and there is all youll need. Anyhow, im so glad for this site. Take care yall, Ron
 
lookinfer said:
I think s30v is overrated. And hair poping sharp is NOT the proper edge to have on a knife.Itll NEVER stay that sharp. purly for showing off. and paper cutting is the worst thing for a blade. itll dull it quicker than sanyhting else. For a actual using knife, id get it poping sharp and then add a VERY slight alternate back bevel, like what one would do on a wood chisel, cuz then itll stay sharp much longer,and definatly WONT chip. I have had complwte success with this method. If yoy do this i can guarantee you the s30v will impress you. But ill say again, Nothing stays hair poping sharp for long. any custom maker will tell you this. you should be able to shave hair,of course.but theres a practical limit. I know, we all like to see how sharp we can get our knives,but if you just add a slight back bevel(say one or 2 very slight strokes at a shallower angle(careful not to press too hard,better to go lighter than harder,definatly. try it a few times,and youll get the hang of it.and that baby will stay sharp for a loooong time.a few strops here and there is all youll need. Anyhow, im so glad for this site. Take care yall, Ron
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My D2 knives stay hair popping sharp, even after cutting two dozen magazines into quarters. :confused:
 
Cliff Stamp said:
You generally want the minimum grain size as it increases strength and toughness

-Cliff
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I don't see how smaller grain size (not carbides) would increase strength, thoughness yes, but strength, no. I don't deal with steel, only with molecular solids and grain boundaries are always weaker than the intra-grain structure and I would expect the same to hold true for steels aswell. They might offer additional slip-planes (in particular multi-directional slip possibilities) which would increase toughness, but this toughness should not apply to the edge. So, really I hadn't thought this through in my previous post. I would expect large grain size ideal for maxium edge strength, but small grain size ideal for bulk toughness. This is now mainly talking about the martensite grain structure.
 
The grain boundries act as obstacles to slip processes such as gliding dislocations so they increase strength. There is no actual limit to grain size, if you held a steel at temperature during austenization the grains would continue to grow as the larger ones consumed the smaller ones and eventually you would have basically one big grain. You actually alloy steels to prevent this, the small amount of vanadium in many cutlery steels for example (AUS series) is to keep the austenite grain small because the small vanadium carbide will pin the grains and keep them from growing. This is why the fracture grain size for F2 is less than 1095. There is nothing stopping you from ideally getting the sme grain size in 1095 but there is nothing in the steel to keep the grain size small unlike F2 which has tungsten to pin the grains which is why F2 is 10 and 1095 is 9. The big problem with grain boundries is keeping them free of carbide and impurity segregation, those are the reason for the two main embrittlement regions in steels.

-Cliff
 
M Wadel said:
knarfeng

afaik the metal is pressed to 100% density before sintering or while they sinter it (or atleast should be)
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Yes sir, I know that it should be at 100% density with the particles fully coalesced. My question was, "Are we sure that it is and they are?"

Wonderful thing about forums such as this. You get a chance to correlate more data than any one user has access to. So we hear about Sebenzas that chip, and Sebenzas that don't. Natives that chip and Natives that don't. When I read that companies like Spyderco, Benchmade, and CRK each produce knives with both chipping and non-chipping blades, I start thinking about factors outside of the heat treat that might account for chipping. Because these are top line companies. Once Spyderco has a heat treat process that produces chip free S30V Natives, all their Natives should be chip free. Finding the process parameters is a bit of an art. Maintaining a process is just good engineering. But all their Natives do not appear to be chip free. So one wonders what might be the cause outside of the heat treat. Issues with the HIP process is one possibility that comes to mind.

Done now.
 
I have a spyderco paramilitary and two Simonich mid techs in S30V. SO far they have been easy to sharpen and all three have held their edges. I have not used them too hard but so far I am very happy with the performance of this steel
 
Cliff Stamp said:
The grain boundries act as obstacles to slip processes such as gliding dislocations so they increase strength. There is no actual limit to grain size, if you held a steel at temperature during austenization the grains would continue to grow as the larger ones consumed the smaller ones and eventually you would have basically one big grain. You actually alloy steels to prevent this, the small amount of vanadium in many cutlery steels for example (AUS series) is to keep the austenite grain small because the small vanadium carbide will pin the grains and keep them from growing. This is why the fracture grain size for F2 is less than 1095. There is nothing stopping you from ideally getting the sme grain size in 1095 but there is nothing in the steel to keep the grain size small unlike F2 which has tungsten to pin the grains which is why F2 is 10 and 1095 is 9. The big problem with grain boundries is keeping them free of carbide and impurity segregation, those are the reason for the two main embrittlement regions in steels.

-Cliff
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Thanks, Cliff, I see. I did some reading and found that my assumption that metals would be similar in this regard to molecular solids was very wrong...:o. Due to the nature of metals, slip processes along glide planes are far easier than in molecular solids, so while in the former grain boundarys reduce slip, in the latter they facilitate slip (they slip along the grain boundaries and slipbends easier or at least as easy as along the glide planes. As an extreme example like ice under pressure you can deform a snowball pretty easily, but a single-crystalline ice cube is pretty difficult to deform). You know now that you have reminded me, I remember having read that somewhere before, but sometimes I mix up work and pleasure :(....
Good thread, learned a lot!
 
New Lone Wolf Harsey Double Action arrived on Friday. Fantastic knife. Sharpened it at 40 degrees just the smooth the edge. Everything seemed fine until today. Pretty good size chip showed up about an inch from the tip. All I've done with it so far is "play" with it while watching TV.

I'm starting to have my doubts if S30V is worth the hassle. Is chipping just something that one has to put up with or will the problem ever be solved? And if one wants to buy an nice high end knife, so many use S30V that there isn't really much of a choice.

Cliff (and many others) have a fantastic amount of if metallurgy knowledge and it's very much appreciated. I just wish some of the steel manufactures would join in. I saw Crucible said a few words but that's about it. Chipping of S30V seems to have become a huge problem. It's a real drag to buy a knife that retails for over $300, only of have what is supposed some of the best blade steel around, start chipping.

To knife manufactures: either get the problem fixed of give us more choices. I'd like to be able to buy a BM Ruckus (for example) in D2, if I desired. I've never had any problems with that steel and I think it holds an edge as good as S30V.

Regards and thanks
 
bladeprince said:
And if one wants to buy an nice high end knife, so many use S30V that there isn't really much of a choice.
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Most custom makers will use a variety of steels, even in production knives there are M2, D2, ZDP-189, VG-10, etc. . What is the shape of the damage on the blade? Is it possible that someone else was using it?

I just wish some of the steel manufactures would join in.
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Generally if you want this type of information you are better off contacting the manufacturers directly, especially in a private medium like email/phone. Issuing a public statement about possible defect issues is fairly rare and not likely to be done in a highly dynamic medium.

The main reason the problem persists is because when people do note failures there is a rush of defensive posting which assuses people of BS. This of course is a huge double standard because the same people will not apply such reasoning to the massive amount of hype used in the promotion of steels which is often never even based on any use.

There is also always the skewed arguements that people are making too much of it because most people are positive even thought there are multiple reports of multiple defects from different brands, defects on knives replaced for being defects, etc. . . If there was a brand of tires which had a 5% serious defect rate due to a systematic error would people defend them because the vast majority was fine or would they expect a recall.

How many knife makers wrote off a steel or steel manufacturer because of problems. Are such makers critized. Hardly. Do they keep trying over and over or do they simply look for another material. You have to give the same level of respect to the consumer and obviously expect them to come to the same conclusion.

Imagine a knife maker who buys ATS-34 and 3 out of 5 batches he buys fails to heat treat properly or finish because it wasn't delivered in the correct condition or the purity was low. He even returns a full order and the replacement is defective in the same way. You really think he will keep ordering.

-Cliff
 
Cliff Stamp said:
Most custom makers will use a variety of steels, even in production knives there are M2, D2, ZDP-189, VG-10, etc. . What is the shape of the damage on the blade? Is it possible that someone else was using it?
-Cliff
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No, just my wife and myself and she wouldn't even think of touching them, even to do her dusting.

The shape of the chip was a very small semi-circle. I'd guess about 25-30 degrees and about a 32nd" deep.

Gary
 
Can you check it under magnification and see if there is any deformation or was it a clean break.

-Cliff
 
Cliff
I just wanted to thank you for your work and your input. I have read your reviews extensively and I have learned much of what I know about knives from you. I never buy a knife or consider a new steel without consulting your work. It is a pleasure to be able to say thanks
 
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