CPM3V Properties

N

nullack

Joined
Nov 17, 2008
Messages
243
Gday folks,

So Acrid Saint suggested I experiment with CPM3V and I'd like to better understand its properties. Can someone please provide the following data as Im having troubles identifying the data:

1. Ultimate tensile strength at various hardness levels
2. Yield strength at various hardness levels
3. Typical grain size using the shephard standard
4. Fatigue strength at various hardness levels
5. Adhesive wear performance
6. Abrasive wear performance
7. Any corrosion tests using the salt spray standard or similar

I already have tempering / hardness and tempering / toughness.

Some Q's please:

8. Is carburising or decarbusing an issue with this material?
9. Will it through harden in all knife section sizes?
10. Is there any problem with normalising like what the ASM caution with on some tool steels?

Much appreciated thanks
 
Thanks Rusty but unfortunately that data sheet doesnt answer the stuff I dont know - the things I do know about hardness / toughness / tempering came from that datasheet.
 
I don't think any company ever did these kinds of tests. However, you can check out the DuraTech Pyrovan HC datasheets for some impact toughness numbers. It is a very similar steel to CPM 3V, just slightly less Cr.
 
nullack said:
Gday folks,

So Acrid Saint suggested I experiment with CPM3V and I'd like to better understand its properties. Can someone please provide the following data as Im having troubles identifying the data:

1. Ultimate tensile strength at various hardness levels
2. Yield strength at various hardness levels
3. Typical grain size using the shephard standard
4. Fatigue strength at various hardness levels
5. Adhesive wear performance
6. Abrasive wear performance
7. Any corrosion tests using the salt spray standard or similar

I already have tempering / hardness and tempering / toughness.

Some Q's please:

8. Is carburising or decarbusing an issue with this material?
9. Will it through harden in all knife section sizes?
10. Is there any problem with normalising like what the ASM caution with on some tool steels?

Much appreciated thanks
Click to expand...

Why would you NEED to know this information starting out... I'm all for being informed and knowing your steel. but with all due respect Nullack; I think, looking over your last few posts, your more concerned with numbers than actually getting down and dirty with it and actually KNOWING it. Take M.S. Burt Foster for example. he'll take a steel that piques his intrest and play with it. He'll keep a notebook. He'll anylize it, have others analyze it. he'll vary temps, very soak lengths, edge thicknesses, any and all aspects that will and can affect the performance, he'll manually try it. By the time he's done He KNOWS that steel like it was his own wife. Again this is with all due respect and not ment to tear you down. But just to maybe redirect some of that passion in to a more productive avenue then just debating the numbers.

Jason
 
I agree with Jason, it looks more like you compiled a list of every test you know of that hasn't been done on 3V. You'll be no closer to knowing if you want to use it.
 
nullack said:
Gday folks,

So Acrid Saint suggested I experiment with CPM3V and I'd like to better understand its properties. Can someone please provide the following data as Im having troubles identifying the data:

1. Ultimate tensile strength at various hardness levels
2. Yield strength at various hardness levels
3. Typical grain size using the shephard standard
4. Fatigue strength at various hardness levels
5. Adhesive wear performance
6. Abrasive wear performance
7. Any corrosion tests using the salt spray standard or similar

I already have tempering / hardness and tempering / toughness.

Some Q's please:

8. Is carburising or decarbusing an issue with this material?
9. Will it through harden in all knife section sizes?
10. Is there any problem with normalising like what the ASM caution with on some tool steels?

Much appreciated thanks
Click to expand...
3. Why the shephard standard? Why not ASTM?
4. What possible good would a fatigue test do for knives?
5. Adhesive wear is the primary test done by Crucible.
7. It's not a stainless steel, why would they do salt spray? It's going to have some corrosion resistance due to the high chromium, but nothing to write home about.
8. No.
9. Yes.
10. Normalizing isn't generally done on air hardening steels.
 
Its an absurd argument to not be concered about mechanical properties like yield strength. You can go and make knives out of 500 different steels and compare yield strength the hard way, or you could lookup those values and choose say the best 10 for prototypes.

You blokes that think that numbers are somehow not relevant have obviously never been involved with computational fluid dynamics or finite element analysis or any serious engineering design process. Many complex machines now go from FEA right into production, so the claim that numbers dont matter is frankly silly.

Im going to ask the manufacturer for the data.
 
The point that people are trying to make is that the numbers useful to knives are far less available. The numbers have to be used within context. Larrin made good points and asked useful questions - I'd suggest that you go back and read some of his posts before you assume that he has little understanding of the subject at hand. He probably had a better understanding of tool steels both in an industrial context and in a knifemaking context when he joined five years ago than you will ever achieve.
 
Larrin said:
3. Why the shephard standard? Why not ASTM?

4. What possible good would a fatigue test do for knives?
5. Adhesive wear is the primary test done by Crucible.
7. It's not a stainless steel, why would they do salt spray? It's going to have some corrosion resistance due to the high chromium, but nothing to write home about.
8. No.
9. Yes.
10. Normalizing isn't generally done on air hardening steels.
Click to expand...

3. Simply that other data I have is in shephard but Ill take any info carpenter has
4. Fatigue is an issue for knives in low cycle high stress conditions. I actually did a FEA study to prove this to myself as that question came up in a previous thread.

5. I dont believe that knife tribology is limited to adhesive wear and Id like to gather other wear test data types for comparison.

7. Because its known that different non stainless steels exhibit different corrosion properties and while I know its not stainless, Id like to compare it against other non stainless materials.

10. The issue Ive seen presented is one of partial martensite formation with hardening and cracking problems, but I have not personally experienced these problems so far in my blades. I use normalising for increases in grain refinement, toughness, fatigue strength and machinability but it may not be all that relevant to an allready fine grain powder steel like this - I need to do more research before knowing that for sure.

I understand what your saying AcridSaint, but I also firmly believe that there are key mechanical properties like yield strength that are fundamentally important to a knifes performance. Strength is one of those. Obviously the dimensions of the blade need to be taken in context like you say, but you need to know the yield strength before you can figure the specific strength of the part.
 
I think it's best to do the tests ourselves, because manufacterer tests are done with much thicker dimensions than knife edges. The impact tests are "through the grain" and wear resistance is usually adhesive, not abrasive. We are only interested in abrasive wear resistance. Some of the tests would be hard to do, but I'm mainly just interested in knife edge toughness and wear resistance.

8. Decarburization shouldn't be an issue with 3V, because its medium carbon content is not too different from the equilibrium. Assuming 0.038% CO2 in the air and 2000F austenization, 3V is very slightly carburizing. Should be neutral at 2050F, but my calculations don't take into account the alloying.
 
I guess too with submitting samples for mechanical testing it canclearly establish if grain refinement can provide mechanical benefits or not to pm steels.
 
. Ultimate tensile strength at various hardness levels
2. Yield strength at various hardness levels
3. Typical grain size using the shephard standard
4. Fatigue strength at various hardness levels
5. Adhesive wear performance
6. Abrasive wear performance
7. Any corrosion tests using the salt spray standard or similar

I already have tempering / hardness and tempering / toughness.

Some Q's please:

8. Is carburising or decarbusing an issue with this material?
9. Will it through harden in all knife section sizes?
10. Is there any problem with normalising like what the ASM caution with on some tool steels?

Come on now let's stop arguing and just look at the questions.

Tensile strength of hardenable steels is directly related to hardness. Search for Rockwell hardness conversion charts and you will get approximate tensile strength numbers usually. 60 HRC is around 320K psi. Yield strength is related to hardness but has some fluctuation with ductility. 3V runs around 80-85% of tensile where a more brittle high speed can be 90-95% of tensile. When you visualize this think if a drill bit not bending much before it snaps. That means the tensile and yield are very close. PM steels have such fine grain the shepard test is a little awkward. Shepard didn't get to see the PM steels (shame). Fatigue is estimated at 1/2 tensile but increases slightly with good cleanliness and fine grain. Decreases with carbide volume and carbide size. 3V has good fatigue and should be on par with clean bearing steels. 3V has only about 5% carbide content so the adhesive wear and abrasive wear characteristics will be dependent on the hardness more. It's not designed for wear mostly toughness. Corrosion resistance is on par with the other 5-8 Chromium grades. Ok, but nothing near stainless. Carburizing the material will make it more brittle and probably crack it. It will decarb readily like any other high carbon grade. No problem with through hardening. Normalizing will over soak the material and cause too much alloy to be dissolved. It will grow the grain and make it behave out of sorts.

Hope this helps. This is as close as you will get to the manufacturer. I helped launch this grade about 13-14 years ago. Great material.
Ed Severson
 
Very informative, Ed. Do you know what is the maximum hardness that CPM 3V could obtain before toughness becomes lower than the S30V class of steels? I'm interested in toughness at high hardnesses.

Also, where can I find impact toughness data on AEB-L? Thanks.
 
Thanks Ed I sincerely appreciate the time you took to post the info.

So, yield tensile and compressive strenghts should be somewhere around the same ballpark as S5 as well as the working hardness. Corrosion resistance should be better than S5 and 52100. It has less toughness than S5 but it may exhibit better adhesive and or abrasive wear resistance.

I don't fully understand the consequences of normalizing this material so if someone could please explain that in more detail that would be great.
 
To be clear, do I understand correctly that Ed advises decarb is an issue needing attention (like some other materials such as s5) and that Larrins understanding of decarb not being an issue is incorrect?
 
nullack said:
To be clear, do I understand correctly that Ed advises decarb is an issue needing attention (like some other materials such as s5) and that Larrins understanding of decarb not being an issue is incorrect?
Click to expand...

That seems to be what he is saying. Not a big deal, stainless foil wrap and plate quench seems to be the standard treatment of this steel by custom makers.
 
You must log in or register to reply here.
Back
Top