S30V: Two questions...

[Buck268]

Well, I hate to post this cuz I know its been covered umpteen times, but no matter what I do (s30v +edge, s30v +grit, etc) I can't get the search to work, so I'm posting.

Anyways, lets start with the simplest question. How is the real-work stain resistance of s30v? I typically put a light coat of oil on my knife(ives) after a messy/wet day, but how necessary is this with CPMs30v?

Now a slightly more complex question. I've heard many complaints about the tendancy of s30v to chip along the edge with hard use. This sounds as if the steel would tend to hold a more refined and polished edge much longer. How does that play out in the real world? Under a 10x hand lens, it looks like spyderco put a very slight but decently polished micro bevel on my Native; I say this beause the grind lines on the main bevel are clearly visible and kinda disappear near the very edge. I tended to like a slightly toothy edge on my working knives as they do such a wide variety of tasks that having the microserrations is almost always worthwhile... But then, if they are just going to chip off on me I'd sooner touch up this knife on a much finer stone when the time comes, or maybe even spring for some 'real' strop compound and part ways with mothers polish...

 

[mete]

I never oil any stainless steel blade , just keep it clean and dry. Never had any problem ! I've never had chipping problems either but of course that depends on heat treatment [some factory HT has not been proper !] and type of hard use. You don't see highly polished S30V because it's so difficult with that 4 % V ! I assume it's fairly difficult then to polish an edge. I'm happy with micro-serrations on my knives and a quick touch up with a diamond rod does very well with S30V.

 

[Buck268]

Didn't know that about s30v being so difficult to polish, good info. Reason I asked about the rusting, was I've had many a blade develope rust pits to some degree... Everything from gerber's "surgical stainless" to good old AUS8. Usually they are very light and often will wipe away with some oil.

 

[gud4u]

Most stainless steels are 'stain resistant', not truly stainless.

My S30V Manix blade showed rust only once, when carried clipped in pocket on a 24-mile bicycle ride on a 90 degree afternoon - the knife was wet with sweat. That was surface rust, which was wiped away (same day) with no residual pitting. Generally, just keeping the blade dry should result in no rust problems.

I did some testing with the S30V Manix blade, consisting of high-pressure pointings of a (really hard) hickory rake handle. At final inclusive edge bevels of 25 degrees or less, I could induce edge-chipping. At a final edge bevel of 30 degrees inclusive, the edge held up fine.

Hope this helps!

 

[Walt-FL]

440-C is more stainless, even if Crucible says S30V is superior. You're well advised to apply an oil coat once in a while. Unfortunately there is no steel that does it all.

According to Crucible, S30V was actually designed to promote the formation of vanadium carbides which are harder and more effective than chromium carbides in providing wear resistance, but this comes at a price>chipping.
Your second question points out a well known problem with this type of martensitic stainless steel. During the melting process so called primary carbides develop due to the carbon content. These can not be broken down with normal heat treatment. During the forging process the carbides are crushed and spread out in the direction of the steel deformation. Finally, the steel has cloud-like carbide deposits. If these deposits are parallel to the edge, it does not impact edge stability, however, the blade is sensitive to lateral forces.
If it's gotta be Crucible why not try CPM154CM wich had great edge holding capabilities and better flexibility. No matter what the steel junkies say, unless you intend to build a jet engine even 440-C is OK. 50% of a steel's superiority is marketing.

 

[NickZac]

Well, I hate to post this cuz I know its been covered umpteen times, but no matter what I do (s30v +edge, s30v +grit, etc) I can't get the search to work, so I'm posting.

Anyways, lets start with the simplest question. How is the real-work stain resistance of s30v? I typically put a light coat of oil on my knife(ives) after a messy/wet day, but how necessary is this with CPMs30v?

Now a slightly more complex question. I've heard many complaints about the tendancy of s30v to chip along the edge with hard use. This sounds as if the steel would tend to hold a more refined and polished edge much longer. How does that play out in the real world? Under a 10x hand lens, it looks like spyderco put a very slight but decently polished micro bevel on my Native; I say this beause the grind lines on the main bevel are clearly visible and kinda disappear near the very edge. I tended to like a slightly toothy edge on my working knives as they do such a wide variety of tasks that having the microserrations is almost always worthwhile... But then, if they are just going to chip off on me I'd sooner touch up this knife on a much finer stone when the time comes, or maybe even spring for some 'real' strop compound and part ways with mothers polish...

A lot of people talk down on S30V...

1) S30V has excellent impact resistance for a stainless steel when hardened correctly. Do not let people tell you otherwise...it is the cutlery steel of the new millennium. The hardening is the key...440C has gotten a bad name because of cheap China folders despite the fact that 440C is an excellent all around steel. Any good steel can be ruined when hardened incorrectly. Almost every folder I have is CPM-S30V and I have opted for this steel over others because I find it to perform better in categories that are most relevant to knife usage. I have never chipped S30V, and I will use my blades hard. This is not to be confused with abuse...a knife's most basic function is to cut, slice and to a degree chop and hack. It is not designed to be used as a screwdriver, hammer, pry bar, throwing mate, kick toy, lawn dart buddy, etc. Testing knives to do this does not show a thing...just that they can indeed be used incorrectly and ultimately, any knife that is abused will fail.

2) S30V has excellent pitting resistance. It will develop surface rust, but it will not pit unless the knife is neglected badly. Surface rust wipes right off, pitting is much deeper. As with any steel except H1, I would recommend cleaning the blade and if you are not using it for food prep, coat it with TufGlide. I use my S30V Sebenza blades to prep food which means cutting lemons, tomatoes, oranges, cheese, meats, etc. The only thing I do is rinse the blade off and dry and I have never had an issue despite the fact that I have buffed this to a very high mirror polish.

 

[Buck268]

Great info, just what I was looking for in regards to both the stain-resistantness and the edge brittleness. gud4u, thanks for the numbers you found in your testing, I'll have to keep those in mind.

Walt, I'm a very budget-limited knife knut, and the Native was actually a little more than I was looking at getting; origianlly was going to get a Byrd Meadowlark with G10 scales (and would very likely been totally satisfied). In fact, once my current beater breaks (again; sent it into gerber for warrenty once) I'll probably do that, although I'm tempted to go back to the Sahara jr; who knows.

 

[thombrogan]

If you leave the edge coarser than 100 grit, it might rust. I thinned out an S30V blade with a 120 grit waterstone and it developed surface rust until I removed most of the deep scratches. Most of the time, S30V chipping comes from grinding the edge too thin or being too ambitious when cutting. If you don't make your edges so thick that your obliques tire from cutting or so thin that you could be paralyzed by curare and still cut ropes, you should be fine.

 

[knarfeng]

Buck268,

http://www.bladeforums.com/forums/showthread.php?p=4097720#post4097720

You might be interested in Jerry Hossom's comments on S30V chipping and its causes. Very enlightening. Actually the entire thread is a good exploration of the subject. But this particular response was especially good.
Mr. Hossom has made a lot of S30V blades (other steels too.) His answers go beyond theory and into the hands-on experience realm of a master knife maker.

 

[Cliff Stamp]

How is the real-work stain resistance of s30v?

Similar to the other high carbide stainless, low compared to something like 420HC.

I've heard many complaints about the tendancy of s30v to chip along the edge with hard use. This sounds as if the steel would tend to hold a more refined and polished edge much longer.

Generally not, S30V is a high carbide steel and thus optomized for a rougher finish. This works well, better cutting ability and edge retention when slicing than a higher polished edge.

-Cliff

 

[Irezumi]

My kershaw spec bump in s30v has a nice polished edge. Took about 5mins on the dmt fine stone. I have found it easier to polish the edge than the 154cm used in emerson knives (man that steel is hard!).

 

[Buck268]

Wow, the info just keeps coming. I really wish the search feature worked better, but I suspect using the query "s30v..." overloads it with results.

Jerry sure knows his stuff, though.


Cliff, did you read Jerry's post by any chance? Are you just saying a 10000 grit waterstone finish is excessive or that the 'recomended' 600 grit sandpaper finish is excessive? Either way, I'll likely be finishing up on a 9 micron dmt stone eventually, hopefully this works alright.

 

[Cliff Stamp]

Cliff, did you read Jerry's post by any chance?

Yes, it is mostly nonsense, actual materials FACTS are otherwise. For example stainless steel has an embrittlement region at 950F due to chromium carbide precipitation on grain boundries, it isn't tough there, that is where it is the most brittle. You also don't get a compromise of properties at 600 inbetween the low ang high tempers, the hardening responce is not so trivially linear. What you actually have to do in reality is to go hotter and temper above the 950F region and thus move the chromium precipitation off of the ground boundries. This was discussed in detail on swordforums with again actual published materials references. You of course still lose a significant amount of corrosion resistance and the only real reason you would do this would be because of problems with obtaining hardness at the low tempers (lack of cold, or forced austenite stabilization due to time delay between quench/temper).

In regards to other issues, the chipping seen with S30V is at times far above the edge bevel itself so the edge finish isn't the problem, though this is dependent on the manner of cutting. If you push cut with a coarse edge it will tend to go blunt faster, but this is never to the extent there are large chips, at least never in the 500+ blades I have personally extensively tested in that manner. This was also well documented by Mike Swaim on rec.knives where he showed that very coarse edges were MORE durable when slicing than highly polished edges. For some knives like the Extreme Judgement I have seen chipping when chopping woods when the finish was coarse, basically the teeth break off so you can feel an irregular spot, but this isn't what a lot of people are seeing with S30V, it isn't impact related at all. Back to actual facts, the heat treatment varies a lot, knives spec'ed at 60 HRC come out as low as 55 HRC and a lot of people are working with burnt edges so those are likely the two main reasons, and of course the fact that it was massively overhyped as having extreme toughness.

For high carbide steels like S30V I generally find that 600 DMT or more coarse works well for what I use them for, extended slicing. If I want fine push cutting edges then that isn't the steel I would use anyway, and you can't expect high performance out of it even with such a finish as the edge stability is low. This has been tested extensively by Landes and company on the german forums, who recently did a massive comparison and found that S30V was very low in this regard, even compared to steels like 420HC, and they used a number of different S30V blades.

-Cliff

 

[Broos]

I've had good experience with S30V with polished or rougher edges. I've been very satisfied with the sharpness of the polished edges. Also haven't had any chipping problems. Just keep it dry to maintain, though putting something oil or whatever on it won't hurt.