CPM S30V and hardning

[Popsickle]

Im going to go ahead and say that i dont think this comparisons of certain steels together are valid. S90V and S30V are clearly a similar material in every aspect but edge retention. You cant compare them to things like 3v, Zwear, and PD-1 because they are just different animals all together. I hate edge damage with a passion and even though i LOVE s90v, this is the reason why i will carry the above 3 high toughness steels i listed as they will not get that damage.

[chuck_roxas45]

Im going to go ahead and say that i dont think this comparisons of certain steels together are valid. S90V and S30V are clearly a similar material in every aspect but edge retention. You can compare them to things like 3v, Zwear, and PD-1 because they are just different animals all together. I hate edge damage with a passion and even though i LOVE s90v, this is the reason why i will carry the above 3 high toughness steels i listed as they will not get that damage.

I agree Josh. I do love S30V(that's why I carry it too) but as you mentioned, it seemed an entirely different animal than the "tough" steels. I guess it's a "right steel for the right job" kind of thing too.

[arty]

Blerv, my experience has been that M4 and 3V are much better suited to carving wooden plugs than s30v. I was really getting some micro chipping on s30v when I had to carve mahogany to make wood plugs in during construction. But then it's probably another "it depends" thing.

As "hardwoods" go, mahogany is pretty soft. Of course, poplar is even softer, but mahogany is nothing like oak or hard maple.

[chuck_roxas45]

As "hardwoods" go, mahogany is pretty soft. Of course, poplar is even softer, but mahogany is nothing like oak or hard maple.

Yep, but still that was my experience with the steels. Oh by the way, the wood was dirty with cement because these pieces were used to level the finishing on a wall.

[Cliff Stamp]

I'm curious, doesn't particulate metal technology reduce the carbide grain size regardless of the carbide volume?

Yes, this is ATS-34 :



and this is the PM version (RWL-34) :



However the edge stability, or ability to hold a high sharpness / low angle isn't significantly effected by the PM process. What Roman found is that all that happens instead of getting a small number of big carbide tear outs you get a larger number of smaller ones so the total damage ends up being the same. In order to significantly increase edge stability you have to :

-lower carbide volume

-increase martensite hardness

-reduce retained austenite

Based on carbide size then would a steel like M4 (due to toughness) or ZDP-189 (due to strength/hardness) be a wiser choice for really thin angles than S90v? Or are they just better for cutting things where carbide-tear-out isn't as likely? Light cuts, homogeneous materials, etc.

Depending on how they are hardened, yes, yes, yes and yes. ZDP-189 has similar CATRA to S90V (Spyderco). The main advantage to S90V is that the gross toughness (Charpy) is higher (carbide volume is smaller in S90V). But I don't see that as being a practical advantage in a knife as it still isn't so high that I would want a bowie made out of it.

ZDP-189 vs S90V is a rather interesting comparison and the reports on it are so highly contradictory with one group of people favoring ease of sharpening, edge durablity of ZDP and another saying the same about S90V. In short they are so similar that it is just random variation being seen and the only real significant difference is that ZDP can be almost 10 points harder.

But to really see the effect of that you have to run very low angles so that edge deformation is very telling. When you do that the harder steels tend to form crisp edges far easier. ZDP also has a unique composition being almost all Cr carbide so it may not have as much problems in sharpening as not all abrasives can actually cut the vanadium in S90V.

Blerv, my experience has been that M4 and 3V are much better suited to carving wooden plugs than s30v.

That is what you would expect, especially with 3V. How do you find the byrd steel which should do very well there as it is both hard and has a low carbide volume.

[chuck_roxas45]

That is what you would expect, especially with 3V. How do you find the byrd steel which should do very well there as it is both hard and has a low carbide volume.

I've gotta try that but with the tenacious and persistence which is what I've got in 8Cr13Mov.

[Zenith]

This is a good resource available one can print and fold and play with regarding carbide size and fine edges.

http://www.hypefreeblades.com/files/schneiden.pdf

Cliff.

Regarding CPM-M4.

It has some Manganese (Mn) in it, well, from what i can gather, have not searched for peer reviewed articles yet, but it is

- An important element, manganese aids the grain structure, and contributes to hardenability. Also strength & wear resistance. Improves the steel, deoxidizes and degasifies during the steel's manufacturing (hot working and rolling). Present in most cutlery steels. In larger quantities, increases hardness and brittleness.

How does it aid in grain structure?

[Blerv]

Thanks all . This is a hall of fame thread IMHO.

[Cliff Stamp]

How does it aid in grain structure?

There are a number of ways :

1) It lowers the the Ac1 temperature and thus reduces the temper required to produce austenite. A lower transformation temperature means lower kinetics for grain growth.

2) In increases the three phase field (ferrite + austenite + cementite) and grain growth is inhibited strongly in this phase

3) It produces a finer distribution of cementite in the initial structure (cementite is enriched with MnFe carbide which is resistant to Ostwald ripening)

4) In solid solution it has a solute drag effect and lowers the mobility of the grain boundaries.