Spyderco Forums

Cliff Stamp wrote:The last is one of the common arguments for differential hardening which achieves the same thing in a different manner. Draw the spine and the blade will be much harder to break but easier to damage.

As an example I commonly get fillet knives to sharpen and they almost always have bent/warped blades. One of the main reasons for this is that the steels are very soft 3-5Cr13 class steels with a less than ideal HT which leaves them soft, and gummy (retained austenite and likely ferrite).

If those blades were instead solid S90V at 95% martensite (or similar class steels) then there would be less of them bent but some of them would be broken. In general the ones from the skilled guys would be fine the less skilled guys could break them from sloppy technique.

I think I see where you're coming from, Cliff. A longer, very thin blade. I have trouble imagining anything I would do to my Caly 3.5 that would risk bending or breaking it (aside from the tip if I dropped it on tile ) but thinking of my Roselli Minnow, I suppose it's conceivable... Still feels more like abuse than use but I'm starting to see.

Thanks brother!

Ken

Cliff Stamp wrote:If those blades were instead solid S90V at 95% martensite (or similar class steels) then there would be less of them bent but some of them would be broken. In general the ones from the skilled guys would be fine the less skilled guys could break them from sloppy technique.

This is a crude explanation from a stress analysis standpoint:

Consider a common steel such as structural steel, car fender, etc. This stuff is not very hard or strong, but it is very ductile. Apply stress to it and at some point you reach the yield point and the material starts yielding. If you were trying to bend a piece of it suddenly it would start deforming and when you took away the force it would be permanently bent. It will start this bending at a relatively low amount of stress. Monkeying around with a knife blade made of low strength ductile material and you will end up with a blade that is bent.

Now consider a heat treated steel that might be used in a knife blade. It is hard but not ductile. Start applying bending stress to it and it will take a lot of force, instead of reaching a yield plateau it will keep going until it reaches its ultimate limit and it fractures. Monkey around with a knife blade made of this material and it will at some point just break. It will take more force to break it than it would take for the less strong but more ductile knife to bend. When you see the more ductile knife start to bend you know to stop pushing on it. With the stronger and less ductile knife you have no warning to stop, it just suddenly breaks.

I know a lot more about structural engineering than I do about knife metallurgy but this is my understanding of how it works.

I have no hope of contributing to the conversation from a technical standpoint, but I enjoy reading about the potential! Thank you.

bdblue wrote:This is a crude explanation from a stress analysis standpoint:

Not crude at all. Very well explained.

bdblue wrote:Consider a common steel such as structural steel, car fender, etc. This stuff is not very hard or strong, but it is very ductile. Apply stress to it and at some point you reach the yield point and the material starts yielding. If you were trying to bend a piece of it suddenly it would start deforming and when you took away the force it would be permanently bent. It will start this bending at a relatively low amount of stress. Monkeying around with a knife blade made of low strength ductile material and you will end up with a blade that is bent.

Now consider a heat treated steel that might be used in a knife blade. It is hard but not ductile. Start applying bending stress to it and it will take a lot of force, instead of reaching a yield plateau it will keep going until it reaches its ultimate limit and it fractures. Monkey around with a knife blade made of this material and it will at some point just break. It will take more force to break it than it would take for the less strong but more ductile knife to bend. When you see the more ductile knife start to bend you know to stop pushing on it. With the stronger and less ductile knife you have no warning to stop, it just suddenly breaks.

Of course there are many stages between these two extremes depending on both load type and material. Most material under load will deform elasticly, then plasticly then fail. Even in the case of your ductile steel, sheer with sufficient, instant force and it will just break. Sure, under a microscope, you'll see it deformed more than your second steel but the person watching the impact would not have noticed any difference. Apply a very slow bending force to your more brittle steel and it will likely deform... some, before failing

But I guess all those "extremes" are where I was loosing Cliff's explanation as I just can't see anything I'm going to do to a Caly 3 that will bend OR break it. I'm not saying either can't be done. Just that it's not in the realm of my knife use. But when he turned the discussion to a very thin (the example I own is .038") blade of sufficient length (this one is ~5") I began to see where the discussion applied (to me) This particular blade is a very high carbon (1.5%-2%) running in the mid 60s. It holds a great edge, but I am aware not to add any (many?) lateral stresses.

Now other folks use their knives rougher than I do, for sure, and the discussion may apply to some's regular use for a Caly 3. Just not mine.

This discussion is terrific and regardless of how I use my knives, I like to know they are more than up to the tasks I ask of them.

Ken

kbuzbee wrote:Most material under load will deform elasticly, then plasticly then fail.

All steels, even as quenched still have the elastic and plastic regions. If you look at the stress/stain curve you will see the following three distinct regions :

1) initial linear
2) sharp non-linear point
3) linear with a dramatic difference in slope

The first part is the initial elastic region, the second part is where the material starts to bend plastically (has taken a set) the third part is where it keeps bending plastically until it breaks and the curve terminates.



The part that most people get wrong is that the actual resistance of the steel to bending (the slope of the curve) is actually the same in the elastic region regardless of how the steel is hardened. All that happens is that the yield point is changed.

The critical part is just how long the plastic region is for the high tempers which means accidental breaks are going to be unlikely because the bend in the knife would be noticed but the max strength temper has only about a third of that plastic ability.

kbuzbee wrote: BTW - I'm loving this thread, my own confusion not withstanding. Just sitting in on a discussion between Jim, Ed, Phil and Cliff is the stuff of dreams

Ken

This is a completely new steel AND I haven't seen it yet so it's more of a conversation between Ed and Phil really since they are the only ones in the thread who have it in hand and worked with it.

All I know about it is what I have been told so far so this is a learning experience.

This is ground breaking none the less. :)

Ankerson wrote:This is a completely new steel AND I haven't seen it yet so it's more of a conversation between Ed and Phil really since they are the only ones in the thread who have it in hand and worked with it.

All I know about it is what I have been told so far so this is a learning experience.

This is ground breaking none the less. :)

Exactly!

There has to be a first run of something that opens minds to other options. Rarely the first one is "the best" but this definitely sounds like a noble effort! On the pioneering aspect for domestic foundries this is a pretty great thing.

Blerv wrote:Exactly!

There has to be a first run of something that opens minds to other options. Rarely the first one is "the best" but this definitely sounds like a noble effort! On the pioneering aspect for domestic foundries this is a pretty great thing.

This is nothing short of history in the making I believe. :D

After dumping good steel - CPM S60V and run this CPM S30V scam, Crucible desperate to make at least some steel which can compete modern steels from Carpenter, Bohler or Hitach. So far their best effort CPM M4 - far behind competitors. They try to use PM technology on old steels like 154CM, D2 or M4, now they try to stuck them to make laminate...

Well SPM S90V steel is not their best so putting it inside CPM 154 will not make it performs better - it is still far behind Carpenter. This is just another pathetic attempt to do al least something.

They need to have better metallurgists and use modern technology. Even same CPM S30V made by Carpenter (CTS BD30) is way better then any Crucible steel.

Why do not they just restore CPM S60V which was only one good thing they did to Knife Industry and which they dump for some strange reason.

Here are the photos of the test Knife, Phil asked me to post them up. :)

ChapmanPreferred wrote:I have no hope of contributing to the conversation from a technical standpoint, but I enjoy reading about the potential! Thank you.

My thoughts exactly.

I'm getting me some popcorn!

So far their best effort CPM M4

Vassili,

Last you wrote here about current steels you stated Cruwear was on top in your test. Has it changed or are you talking about overall performance and not the specialized testing you have done?

I feel like I have to post this here even I am boycotting Spyderco for inappropriate comment Sal made earlier. Considering that, I still should not hide the fact that this new Cruwear Mule fixed (and seems like tested properly before going to market) show best result in my edge retention testing. Seems that finally Crucible was able to make real super steel which can beat Japanese ZDP-189.

Thanks, and yes I still like Cruwear as close to a favorite steel as I can come up with.

Joe

Very enjoyable to be a fly on the wall :) Happy to see Nozh2002 posting :) :)

Learning is a beautiful thing. Understand the concepts and graph and look forward to the results of real world testing via Mr Ankerson. Very sweet looking test knife :D

The Mastiff wrote:Vassili,

Last you wrote here about current steels you stated Cruwear was on top in your test. Has it changed or are you talking about overall performance and not the specialized testing you have done?


Thanks, and yes I still like Cruwear as close to a favorite steel as I can come up with.

Joe

I am not quite convinced that this was made by Crucible and was not outsourced.

Those were shipped not from Colorado but from Florida and this made me thing that there is something not quite Crucible about that steel.

When I see more knives made with that steel, then it will be clear, but so far it looks strange. Why made in US steel and made in US knife by Spyderco from Colorado will be shipped to Florida and then all over US?

I can understand that knives made in Europe better be distributed from some location close to harbor.

Will see I would be happy if I see more knives with Cruwear blade, but instead somehow we have this nonsense laminate.

CPM S90V has exceptional abrasive resistance but not very good edge holding so what the point - this combination make in result pretty expensive average performing knife. Why?

Laminating it in CPM 154 which performs almost as good as CPM S90V make no sense too - it will be easy to polish but yet expensive average performing knife.

So if they really can - they better produce Cruwear (or CPM S60V). Otherwise I do not see how they will be able to compete now days. Everybody know about the way CPM S30V was pushed and no one will be tricked same way (look how they try to push CPM M4, without too much success, and destroying good knife competition as a side effect, which is now just cutting circus) again as well as there are lot of really good steels from many different manufacturers who do better even with same composition Crucible does (like CTS BD30).

What are CPM S90V's shortcomings in edge holding?

nozh2002 wrote:After dumping good steel - CPM S60V and run this CPM S30V scam, Crucible desperate to make at least some steel which can compete modern steels from Carpenter, Bohler or Hitach. So far their best effort CPM M4 - far behind competitors. They try to use PM technology on old steels like 154CM, D2 or M4, now they try to stuck them to make laminate...

Well SPM S90V steel is not their best so putting it inside CPM 154 will not make it performs better - it is still far behind Carpenter. This is just another pathetic attempt to do al least something.

They need to have better metallurgists and use modern technology. Even same CPM S30V made by Carpenter (CTS BD30) is way better then any Crucible steel.

Why do not they just restore CPM S60V which was only one good thing they did to Knife Industry and which they dump for some strange reason.

lolwut

Outsourced by a foundry? Do they make the tinfoil hats locally?

Vassili, they have announced a Cruwear military sprint sometime later this year.

Joe

disgruntled crucible employee? J/K