Stainless Steels vs. Carbon Steels

Johno, your last paragraph is common knowledge and nothing new. That was like saying the sky is blue.

As for mod. of elast. I hope you read what I posted on it and what roger stated afterwards, which is more correct than that quoted paragraph. IT DOES VARY if only slightly, but it does VARY. Since the STRESS/STRAIN curves of most STEELS are similar, their slope will also be similar. However, the actuall values will be different meaning that the Stress and strain will vary, hence, the percent elongation will vary and NOT be the same. Yes, the difference is small usually between 2-5% difference in elongation.

Now to the real issue. The question I posted above for both you and roger. I just want to make sure, that it is what you believe, so that I understand were you are comming from.


_________________

Those who read from a doctors book can only pretend but will never really understand.
 
Cobalt said: "The point is that even though you can bend the softer steel further, you may not have enough strength to ever get the stronger steel to bend to the 45 degrees." and "Roger, you're wrong, all steels with the same dimensions, do not bend the same amount. Take 3 blades made from completely different steels and do you really think that they will all bend the same amount."

You were trying to make the case that there were large differences in the modulus of elasticity between different steels, which isn't the case, and seemed to be confusing the modulus of elasticity with plastic deformation and yield strength. Elongation in the elastic region also by definition varies a small amount if the modulud of elasticity varies a small amount, and again doesn't explain the mechanical properties that you were describing earlier. Again, Roger had it right.

 
To answer Nimrod's original question:

I would definitely want a "stainless" pocket knife.

I would buy and use fixed blades depending on the use and performance needed.

Right now I'm looking at Schott's Camp Knife in 3V, stainless or not.

As for material properties and best blade choices...
I've always heard you can have only 2 of the following; toughness, hardness, or corrosion resistance.
It seems we're getting closer to having all at once. I am glad the companies are pursuing new alloys and heat treatments. If nothing else, it gives us all an excuse to get another knife!

wayne
 
Hi
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Originally posted by Cobalt:
...their 3V is no different than O-1.
Click to expand...
Just because of my curiosity, since I've never had a blade made of 3V & I am interested in this one, so is it similar?
Alloy compositions are quite different, so I was wondering.
O-1 - C-.80-1.0; Mn-1.0-1.65; Cr-.40-.60; Mo-.60; V-.20; W-.40-.60;
CPM 3V - C-0.80; Cr-7.50; V-2.75; Mo-1.30;
Except carbon everything else differs significantly?

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Have Fun,
Alligator

[This message has been edited by Gator97 (edited 05-17-2000).]
 
Originally posted by Cobalt:
Roger, since you think that the hardness factor makes a steel elongate more. I want to make sure I am not misunderstanding what you are saying. Is the following what you mean: Take two pieces of 1095 steel , one hardened to Rc of 61 throughout and the other hardened to an Rc of 56 throughout. The Rc of 61 steel will elongate further under equal stress than the Rc 56 steel. Is this what you are trying to say? and if so, I would like to know where you got the information from since I have never heard of that before. I will learn something new today
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Click to expand...

No, that is not what I am saying. They will both elongate the same under the same force. I think I said this to begin with. I would rather not talk about hardness but about carbon content in the matrix. Steel with a higher carbon content will take more force to break. So if two knives were other wise the same except for carbon content and were made to elogate the one with less carbon would yield first. At this point the one with more carbon which has not yielded will have elongated equally. If you continue to add force it will elongate further in the elastic range. Does this make sense?



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Roger Blake
 
Roger quote;"Harder steels will bend further and go to higher stresses but tend to
break with less deformation, hence they are less tough. Still they make
better knives"

"The harder steels can take more stress so they will stay in the elastic range longer so they can elongate further. "

Then you say:" I would rather not
talk about hardness but about carbon content in the matrix. Steel with a
higher carbon content will take more force to break."

It seemed to me that hardness was what you were talking about not anything else. But since you have changed tracks to Carbon content instead, I agree on what you said about carbon content.

Johno, you are not reading what I am saying.
Cobalt said:" all the modulous
of elasticity is, is the slope of the stress/strain diagram of a steel.
Since most steels behave the same way, the slopes will be similar, but
not exactly the same. They do differ, there is no doubt about that. ". When I said the slope is similar, that means that the value is close, not a big difference like you stated I was saying. You actually stated that the modulous does not differ at all and I would bet that the modulous will differ slightly between carbon and stainless steels. I said SLIGHTLY since it is a slope.
 
This is the statement I took issue with from my first post. I am quoting you here-

"You also have to take into consideration bend strengths. What good is a steel that can flex 180 degrees when it's bend stregth is 4 times lower than a steel that only flexes 45 degrees. The point is that even though you can bend the softer steel further, you may not have enough strength to ever get the stronger steel to bend to the 45 degrees."

I just take issue with this. Since steels have about the same elasticity it bends the same under the same force.

Also lower carbon has a good corellation with toughness.

Just my opinions, take it easy.



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Roger Blake
 
Roger, good, now we have another point. You seem to think all steels will behave the same. Well, go see how a well forged carbon steel blade from one of the bladesmiths bends. I think that these knives have to be able to bend to 90 degrees. We are talking about basic O-1 or 1095 here going to 90 degrees in a flat ground 3/16 or 1/4 inch blade. Yet if you try to take an ontario 1095 1/4 steel survival machete that far it will snap in two, as will a mad dog tusk in O-1. YOU CANNOT SAY that all steels behave the same.

If all steels regardless of processing have the same elasticity(and they don't) then why does the above example occur?
 
"If you stew cranberries like applesauce, it tastes more like plums than rhubarb does"
-Groucho Marx

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"Well before these arguments are resolved, Science will have replaced steel with an alternative material." Annonynous
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Jerry Hossom
www.hossom.com

[This message has been edited by GaKnife (edited 05-18-2000).]

[This message has been edited by GaKnife (edited 05-18-2000).]
 
Cobalt said: "You seem to think all steels will behave the same.......If all steels regardless of processing have the same elasticity(and they don't) then why does the above example occur?"

Roger didn't say that all steels will behave the same and neither did I, but we did say that you were confusing which mechanical property explains what you were describing, and how those properties vary with type and processing of steels.
Elastic properties could be described as those which don't produce permanent changes to the test piece, such as not bending a piece of metal so far it gets bent or breaks. Plastic deformation is where a permanent change has been made in the test piece in the form of the metal flowing, such as putting a bend in it. Brittle failure is where the piece will snap or break instead of bending. Increasing yield strength will allow a test piece to take more load and remain elastic, but increasing it to high levels tends to produce a change in failure mode from plastic deformation to brittle failure. The elasticity, or tensile modulus of elasticity which is what we've been discussing, varies perhaps 5% or so among different steels, low carbon vs stainless vs tool steels and soft to hard. The yield strength for different steels varies over a factor of 10, and 'brittleness' as measured with something like the Charpy (speling ?) notch test even more.

In general at the hardness levels used in knives the stainless steels tend to be more brittle than the carbon steels.

 
Not to beat a dead horse here, but does anyone feel that this technical discourse has challenged the veracity of Will York's original contention that CPM 3V is the best carbon steel and CPM 420V is the best stainless steel?

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Semper Fi
 
Bronco--

I'd like to see my hypothesis challenged--VERY MUCH! In fact, I think 10V may be a more aggressive cutter as far as slicing action goes than 3V, because of the higher volume of vanadium carbides, and may be more wear resistant. The reason I put 3V at the head of my list is, as I said, it is tougher at higher hardness than anything else to date that I know of--haven't seen specs on INFI. That means 3V can be shaped to a thinner working edge than anything else I know of, at like strength--or a stronger edge at like thickness/bevel angle.
Ed Schott demonstrates what a thin edge can do, in his primary grind with 3V, to a degree I have not seen matched. But I've not yet tried anything in 10V with a primary grind only (no secondary edge bevel) in Ed's range of 12 degrees included edge angle. And then, there's still 15V and INFI out there to spice up the mix.
Who knows? Exciting stuff, though. Bottom line: I don't care whose prediction turns out to be right--I just want to know! (BTW, anyone who hasn't push-cut through a 1/2" sisal rope with one of Ed's blades really ought to try it sometime. It's a revelation.)
In the long run, I'm betting Jerry Hossom has it about right. If a dedicated effort were launched by the metals industries to find a better knife blade material, as our vernacular might define it, I think we'd see stuff that puts carbon steel in the shade--and I include high-chromium ("stainless") steels in that mix.

I will make a prediction: A hands down winner from the above-mentioned steels will be determined via defendable, comparative, head-to-head testing in the forseeable future--and if by no one sooner, then eventually by Cliff Stamp. That man can tell you what a blade will do, and he's looking at all of the above not only in existing formats, but eventually in blade geometries of his own design. That is, once he's determined the functional limits of edge geometry in currently available blade materials. I'm telling you, boys, he's working it out. Some eyes are going to open.

--Will



[This message has been edited by WILL YORK (edited 05-18-2000).]
 
Johno:"tensile modulus of elasticity which is what we've been discussing,
varies perhaps 5% or so among different steels, low carbon vs stainless
vs tool steels and soft to hard. The yield strength for different steels
varies over a factor of 10, and 'brittleness' as measured with something
like the Charpy (speling ?) notch test even more. "

There is no doubt that you guys were confusing the issue not me. Johno, you are now saying that the elastic modulous does differ. That is because you just read it in a book, and said oh crap he is right, they do differ, which is what I was saying all along. % elongation also differs, even though you both stated several times it doesn't. Some steels have elongation values of 40% some have values of 20%. The point is that they don't all have the same elongation like YOU BOTH STATED AND ARGUED OVER AND OVER.

Read all the past posts and quit changing the subjects when it suits you. I feel like I'm talking to the Democratic party caucasus. They only hear what they want to hear. If you want to discuss this further email me and I can set you straight., this is getting pretty boring.
 
Anybody interested in turning this dicussion back to knives from metal bars? Knives aren't metal bars. Knives are sometimes differentially heat treated. Knives can have spines that are .25", and edges that are .025". They can be hollow ground or flat ground, can have thick or thin edges. Knives historically make poor and ridiculously expensive screwdrivers, hatchets, or chisels. There are specialized knives that are made to cut just about everything, but the ordinary pocket or belt knife is made to cut the non-metalic things we find in our everyday environment, at the most elemental level, to turn plants and animals into shelter, food, and clothing. The best knife for that is one that cuts really well, and stays sharp a long time in that environment.

So, back to the original question, what's better, a stainless steel knife, or a carbon steel knife? A few years ago, we used to debate this constantly on rec.knives. We knew exactly what a carbon steel and a stainless steel were back then. A carbon steel was one that rusted in the desert, and a stainless steel was one that always stayed shiny, but never stayed sharp. I think there was some degree of consensus at that time that a stainless steel was one with 13% Chromium, or more, and everything else was a carbon steel by default. I think it was more or less proved, back then, by weight of argument, that if you could keep them from rusting, carbon steel knives were better. You could get a finer edge on them, they were easier to sharpen, and they held an edge longer. Stainless steels didn't hold an edge as well, wouldn't take as good an edge to begin with, but the edge wouldn't disappear in a weeks time from corrosion, and they always looked good.

Things have changed a lot since then. ATS-34 was the HOT new steel then, and if you heat treated it right, it would hold an edge about as well as anything. It does. You couldn't let it soak all day in the sea water catch box with the fish like the stainless knives we used to use on the fishing boat though. Now, CPM440V will hold an edge seemingly forever. It is a lot less clear that "carbon" steel knives are better than stainless steel knives. Stainless steel knives are still stainless though, or at least much less likely to rust.

Last time I talked to him, Steve Mullin of Pack River knives was offering both O-1/1084 Damascus and CPM440V blades on his hunting knives. He said the carbon damascus knives were for the guys who liked to keep a razor edge, and didn't mind touching it up a couple times while skinning a deer. The CPM440V blades were for those who like to sharpen their knives before the first hunt of the year and then forget about them until next year. So it is just a matter of knowing which sort of hunter you are.
 
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