S30V questions (Cliff Stamp u r welcome to post)

O'boy! Some good info in this thread. I'm a little confused about the heat treat part. I had thought that one of the benifits of S30V was that it was easier to heat treat than S90 or S60.
 
There may be a number of reasons for Chris Reeves using a lower hardness on his S30V. There is a little toughness gain at Rc57-58 compared with Rc59-60, but not much. Below Rc57 I understand it's not as tough. Sharpening would be easier at the lower Rc. There are lots of tradeoffs in that equation, including preferred edge geometry.

Rust is an iron carbide issue, and with nitrogen replacing some of the carbon associated with the iron, rust is reduced. That's one reasons S30V is more corrosion resistant than 440C even though it has 3-4% less chromium. Still more of the measured carbon is associated with the vanadium so the amount of iron carbides is reduced further.

I'm not sure Vanadium is added to the melt as metallic vanadium or as vanadium carbide. The former is very expensive. Your take on retaining free chromium is on the mark though, and that along with some reduction in iron carbides contributes to the corrosion resistance.
 
easyrider

I know BM has S30V in the switchback but I meant that it has yet to use the steel in its other major models the way Spyderco has done. Other companies such as Emerson seem to be doing this as well.

The 710 and 806 at least should get the S30V treatment
 
The Stratcor site link from rdangerers post above provides some insight. They produce VNC alloys that also contain Al and Si as steel additives. That may be an easy way to get alloyed Vanadium CarboNitrides in the mix. The photomicrogarphs suggest that above a threshold percentage of N in the mix, much smaller CarboNitrides form. Possibly the N at these levels is acting as a dispersant, causing finer-grained crystals to form.
I will be watching to see what the ultimate explanation is. I'm sure it will all come out in the wash eventually.
In the meantime, S30v is still the best steel for my money.
 
Apparently there is a great deal in steel with which Nitrogen reacts.

I first heard of it with "Cronidor 30" which was making stel for NASA using a .5 Nitrogen content. They made extraordinary claims for their material.

I'd been speaking with Crucible about making a custom nigh Nitrogen steel for Spyderco. It was then that I was told about S30V, Nitrogen and the patent explanation and asked to keep in private for a while.

I can tell you that Crucible is still working with and improving their powdered metals. They've got some passionate folks leading the program and I believe they will come up with better and better steels.


There is a book that a friend of mine turned me on to. Some of it is over my head, but there is much info;

"High Nitrogen Steels"

Structure, Properties, Manufacture, Applications

by V.G. Gavriljuk & H. Berns

Published by Springer in 1999

sal
 
Originally posted by Sal Glesser
"High Nitrogen Steels", Structure, Properties, Manufacture, Applications, by V.G. Gavriljuk & H. Berns, Published by Springer in 1999. sal
Click to expand...
Good lead Sal.

This book can be yours for $109 with free shipping at Amazon, or about $63+ shipping used right now.

I'd like to have this book. Alas, the work & cost of renovating my house are beckoning me to step away from the computer and my knife hobby about now... (I do happen to be using my Spyderco Military to cut R-13 insulation batts to length, to keep with the knife content... ).

Thanks for an interesting thread so far guys.
 
To be clear, Chris Reeve targeted his BG-42 for the Sebbie at Rc60.

He's dropped his target for S30V to Rc58-59.
 
You have all done an outstanding job of making me feel like I know nothing. Thanks guys, great info here. Glad to see the big names jumping in to clarify things. :)
-Kevin
 
Using the right steel is a very important step.


Heat treating it right is the MOST important step.
 
Sal, that is some fascinating stuff on S30V and nitrogen. Would anybody happen to know if Crucible is updating (or has modified) their recipe for 3V to take advantage of nitrogen? Improved corrosion resistance for 3V would make it frighteningly good :eek: :D .
 
It's long been my guess that the N was already there in 3V. They get a lot of hardness out of 0.8% carbon, especially with the 3% vanadium and 7.5% chromium using a good bit of that. They may have wanted 3V to be somewhat rust-resistant. 7.5% is an odd number for chrome, since 4.5% would likely have sufficed for air hardening purposes. The added 3% must be there for a reason.

My experience with 3V is that just a little oil keeps rust at bay. Tuf-Cloth doesn't really help much, because that stays entirely on the surface, and 3V rust seems to form in microvoids just at the surface, usually just in a few small spots on the entire blade, but below even tiny spots are holes. That's what leads me to believe there are microvoids, where the rust begins. A finely finished 3V blade or edge surface doesn't seem to rust readily at all. I use Birchwood Casey's Synthetic Gun oil which is a very thin teflon-containing oil and don't have much problem. I think the light oil displaces any moisture in the voids and solves the problem. I've also begun having some of my 3V blades Bodycoted with Tungsten DLC and that resolves the matter entirely of course.
 
How does S30V stand up in a large chopping knife? (Properly heat treated of course)
 
you should have read the article in Blade a few months ago which featured Rob Simonich's S30V knives on the front cover..then you wouldnt be asking that question. It holds up as good as a forged knife from one of the nations premier knife pounders.
 
Interesting insight, Jerry. I don't own any 3V knives but I'd like to change that very soon. Do you think these microvoids are a product of the CPM process or are somehow specific to 3V? Would a more traditional blade coating such as baked-on expoxy fill those microvoids to prevent rust, even if the coating is worn down to the steel?
 
Crucible claims there are no microvoids, but I think the CPM process would be hard to pull off without a couple microvoids in the final product. The reason I think this is a plausible explanation is because of the way the rust appears. In a large, maybe 9" blade, you might see 3-4 spots on each side, and they tend to be clustered. If there was something more general to the steel, specifically in its composition, I would expect the rust to be more widely distributed. Also, those holes under the rust spots suggest the corrosion has been going on for some time before the rust becomes visible on the surface. That said about 3V, I've seen absolutely no evidence of this kind of rusting on S30V.

I think pretty much any coating would protect the steel. The likelihood of an all over coating missing the few spots where corrosion is likely to occur is fairly slim. Frankly this is a VERY small problem in a steel that is otherwise as good as it gets for knives, IMHO. 3V has 5 times the lateral toughness of S30V, but that doesn't take much away from S30V which is 2.5 times tougher than the next best stainless knife steels. I have had Rc61 3V blades bent to 90 degrees without breaking. I've abused S30V blades in ways that have broken other steels. In practical use, I doubt most users could tell the difference. You really have to work at making either one of these fail.
 
Jerry,

Just wanted to thank you and the others for a most enlightening thread. Makes for some interesting reading and the technical aspect is intriguing. I have stayed away from S-30V for a chopper, maybe I should reconsider. ;)
 
Yep, very interesting.

Mr Hossom: That 3V flex is very impressive. How far does S30V flex before failure?
 
Andrew, although I havent broken a S30-V knife by flexing it I would hazard a guess that 3-V will flex quite a bit farther than S30-V given two identical knives properly heat treated. S30-V is a very stiff seel however and it would be fun to make some identical knives of various steels and and measure the stiffness. Some knives I have tried touted as being very tough actually flexed and bent easily.

I feel S30-V is the best balanced stainless steel on the market at this time in the three areas I look at when steel shopping. Wear resistance, toughness and corrosion resistance. There are stainless steels out there that will do any one of those three things better than S30-V but S30-V does them all very very well.
 
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