Why Use Carbon Steel?

Dude, you've got to cut down on all the jibberish. Real world heat treating should be followed by practical use and experiments.

Hoss
 
i like reading bluntcuts technical posts, but yah i cant say I can really follow it, I try to though :)
 
Sorry OP - for my OT.

Most likely, I targeted for a 65rc, so I can test thinner edge geometry (0.02" BET and straight 13-15dps) against hard knotty seasoned woods. 3rd parties hardness readings probably be better/real than my videos. Flat spots hardness reading on a completed chopper usually a point or 2 lower than edge area.

When ht is successful (cooling is a challenge for 0.350" cross section of a shallow hardening W2 steel). In my W2 chopper video, I will include a dizzy 1 minute dragging the camera between of hardness testing and chopping area.

Shaw Blades said:
I would like to see videos of the 66 RC W2 chopper, with a rockwell test in the same scene.
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DevinT said:
Real world heat treating should be followed by practical use and experiments.

Hoss
Click to expand...

^ this :thumbup:

One thing I've learned is the heat treats specified by the steel makers aren't optimized for our application. Also, there is a lot going on that you can't measure with a hardness test. The only real way to optimize a heat treat and validate your work is practical use and experiments.

During development it's helpful to minimize variables and maximize the "signal to noise ratio" by tightly controlling the geometry of test pieces (no guessing at edge angles, 2 degrees makes a big difference in the outcome), standardizing on cut tests, the use of cut test standards, and doing things like grind edges wet to remove heat as a potential variable etc. When you boil it down and control every variable you can dial in a heat treat. But beyond a certain point it requires real work to do this, not theory. At the end of the day you might have something that is different than other people do it.* You might not even be able to explain why all of it works. But ultimately it boils down to real work and real R&D. Practical use and experiments. Otherwise, if you haven't done your homework your opinion is just an opinion :thumbup:


*edit to add: My copy of Tool Steels 5th edition is an important addition to the 4th edition that many of us have. The fact that so much information changed in recent years shows that a lot of this stuff is still not figured out. If the PHD metallurgists in industry are still figuring it out, there is still a lot out there to figure out. It isn't a mature science yet and you can do something for your application that isn't in the literature.
 
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I doubt that knife makers are the only people using a number of these steels for things other than those purposes for which they were originally developed, but we just so it so wantonly. :D
Nathan the Machinist said:
^ this :thumbup:

One thing I've learned is the heat treats specified by the steel makers aren't optimized for our application. Also, there is a lot going on that you can't measure with a hardness test. The only real way to optimize a heat treat and validate your work is practical use and experiments.

During development it's helpful to minimize variables and maximize the "signal to noise ratio" by tightly controlling the geometry of test pieces (no guessing at edge angles, 2 degrees makes a big difference in the outcome), standardizing on cut tests, the use of cut test standards, and doing things like grind edges wet to remove heat as a potential variable etc. When you boil it down and control every variable you can dial in a heat treat. But beyond a certain point it requires real work to do this, not theory. At the end of the day you might have something that is different than other people do it.* You might not even be able to explain why all of it works. But ultimately it boils down to real work and real R&D. Practical use and experiments. Otherwise, if you haven't done your homework your opinion is just an opinion :thumbup:


*edit to add: My copy of Tool Steels 5th edition is an important addition to the 4th edition that many of us have. The fact that so much information changed in recent years shows that a lot of this stuff is still not figured out. If the PHD metallurgists in industry are still figuring it out, there is still a lot out there to figure out. It isn't a mature science yet and you can do something for your application that isn't in the literature.
Click to expand...
 
bluntcut said:
Please allow me to hand-waving about matrix strength using informal emperical data. HRC is useful in a sense of repeatable average composite indicator for compressive strength - good enough for this discussion (I think).

Let's look at some steels.

Ht for max HRC. Where HRC is a composite indicator of strength (Matrix + Particle strengthening + ignoring grain angle alignment/dislocation)

1084 (less than 0.5 carbide volume %) - 67rc
W2 (~3 cv%) - 68rc
AEB-L (~ 2.6 cv%) - 65rc
3V (~ 2.7 cv%) - 63.5rc

Since 1084 and W2 both have less than 1% mass of elements beside (Fe & C), therefore W2 1 extra rc came from Particle/Fe3C strengthening. Ultra high carbon low alloy steel could yield up to 72rc, which can easily attributed to strenghtening from high cv%.

Keep it simple, let ~2.5cv% = 1rc particle strenghtening. Thus matrix strength of

1084 - 67rc
W2 - 67rc
aebl - 64rc
3V - 62.5rc

Cleary there are MATRIX strength differences between low alloy and high alloy steels. When cutting activities interact with steel matrix and where strength is an advantage, qed stronger is better. e.g. push cutting where carbide/hard-particle are not completely shielded the edge, so matrix strength is important.

Continue looking at strength (not toughness)...
Why 3V is 1.5rc lower than aebl? Well

1. Most likely due to high % of RA. Mo is a phase stabilizer - in this case, increase the temperature of carbon precipitation and diffusion.
2. or inappropriate ht, didn't put enough carbon in solution.

Whichever way, 3V's matrix is the least strong among listed steels.

Wow, sound like we all should use low alloy high carbon steels ;) Well, unfortunately ht outcome of these steels ended up poorly - combination of large grain; weak grain boundaries; high % of plate martensite; large particles. 1084 or below reduces the magnitude of listed problems. Good thing: Aldo's 1084 with added elements grain refinement help minimize some of the listed problems.

Steels: D2, 3V, Infi, Vanadis4e, Elmax, s110v,... throw in wear resistant and corrosion resistant and elements to stabilize phases + pin grain at cost of matrix strength.

Toughness is strength working in conjunction with energy absorption+dispersion volume&speed&direction and much more...
Click to expand...

WOW, 1095 and W2 at 67HRC?

People seems to use the the word strength in wrong meaning... everyone know there are 3 type of strength, shear, tensile and compressive.

Rockwell hardness is not directly translet into any type of strength... yes hardness does have a role but there are also other properties like yield elastic limit, elastic modulus, shear modulus... and many more... it just not that simple as your summarize.

Good example is diamond, extremely fine grain as material can dream yet one of the hardest material on earth, but we know it not very strong stuff...
 
Nathan the Machinist said:
^ this :thumbup:

One thing I've learned is the heat treats specified by the steel makers aren't optimized for our application. Also, there is a lot going on that you can't measure with a hardness test. The only real way to optimize a heat treat and validate your work is practical use and experiments.

During development it's helpful to minimize variables and maximize the "signal to noise ratio" by tightly controlling the geometry of test pieces (no guessing at edge angles, 2 degrees makes a big difference in the outcome), standardizing on cut tests, the use of cut test standards, and doing things like grind edges wet to remove heat as a potential variable etc. When you boil it down and control every variable you can dial in a heat treat. But beyond a certain point it requires real work to do this, not theory. At the end of the day you might have something that is different than other people do it.* You might not even be able to explain why all of it works. But ultimately it boils down to real work and real R&D. Practical use and experiments. Otherwise, if you haven't done your homework your opinion is just an opinion :thumbup:


*edit to add: My copy of Tool Steels 5th edition is an important addition to the 4th edition that many of us have. The fact that so much information changed in recent years shows that a lot of this stuff is still not figured out. If the PHD metallurgists in industry are still figuring it out, there is still a lot out there to figure out. It isn't a mature science yet and you can do something for your application that isn't in the literature.
Click to expand...

This is an excellent answer. I try to stick to a few types of knives and use very similar geometries that work with the heat treat and geometry. In those applications I know how my blades perform. I've been making knives for a few years now, and there simply hasn't been enough time to learn dozens of designs and heat treats.

To make this relate to the OP, the use of carbon or stainless is a relevant, but not the most important factor in making a good blade. Refining heat treat and geometry for the steel and application will result in a better blade than some super steel with lousy heat treat or lousy geometry. The best advice anyone can give is to learn the steel, listen to those who learn about heat treat, experiment a bit, and test your results. Keep refining, and when you have a great process, keep repeating it.
 
Quite a few makers can ht 1095 & W2 to 67rc and 68rc for W2 (sometime). So yes.

Welcome to search for my older posts about HRC. Please notice the word 'composite' from my statement and well. Discussion can get bog down with definition and semantics. It's more productive to focus on actual deduction and points and possibilities - better just express whys & why-nots. Much more fun to yak about ideas/concepts and obviously have a blast to specifically poke holes in presented ideas/conjectures/whatever.

Metallurgy is a large field like many others, so naturally there are many folks with in depth knowledge/skills but it would be extraordinary rare for one with depth and breadth for the entire field. Without a doubt, there are lots more metallurgy yet to be discover & learn. From rational deduction, we can see compromises. From there, we can ask ourselves, are those really compromises or solutions yet to explore+discover. In specific, can 3V have hrc similar to aebl? why and why-not. Are there ways around given composition, which physical chem make it a challenge to over-come or just accept *as-it*.

If I had chosen *as-it*, Super Quench wouldn't be an available tool at my disposal.

shqxk said:
WOW, 1095 and W2 at 67HRC?

People seems to use the the word strength in wrong meaning... everyone know there are 3 type of strength, shear, tensile and compressive.

Rockwell hardness is not directly translet into any type of strength... yes hardness does have a role but there are also other properties like yield elastic limit, elastic modulus, shear modulus... and many more... it just not that simple as your summarize.

Good example is diamond, extremely fine grain as material can dream yet one of the hardest material on earth, but we know it not very strong stuff...
Click to expand...
 
bluntcut said:
In specific, can 3V have hrc similar to aebl? .
Click to expand...

Yeah. In fact I doubt AEB-L hits 65

4.jpg~original


^ that's not even a high aus temp because the application calls for a lath martensite. And that's after a low temper too. It's a function of a high conversion %, avoiding all those messy structures that lead to poor edge stability. 3V will never have the fine edge stability potential of W2, nor will any other complex steel, but you can get pretty darn close. But not with the book HT.

One has to be careful comparing steels though because unless they were all optimized you might be comparing apples to oranges.
 
I started out using W2 and decided to switch to stainless shortly after. The decision was based largely on sharpening hunting knives for people and seeing them come in with blood, hair etc still visible on the blade the next fall. I thought to myself why make a perfectly good knife and sell it to someone who will not take care of it and then bad mouth me and my product when it rusts, when in fact it is their fault. It did not make sense to me.
 
Just took this picture of my aebl paring blade at tempered (not AQ) hardness. Recalling this thread - http://www.bladeforums.com/forums/s...-quot-paring-boning-knife?highlight=aebl+64rc
I stopped update this thread because lacked of interactions. I made a large batch of paring blades with AQ hardness 65rc, some hits 65.5rc (reading is average of 3 readings in 3 different places on the blade - tang, mid, tip). I tempered down to 64rc before post-ht grind the blade.

uLe1nuy.jpg


I agree that care must be taken when comparing steels and their designed for intended applications. However in this case, I just focus on matrix hardness. After all, matrix is the foundation (major component) of cutting tools.

Nathan the Machinist said:
Yeah. In fact I doubt AEB-L hits 65

4.jpg~original


^ that's not even a high aus temp because the application calls for a lath martensite. And that's after a low temper too. It's a function of a high conversion %, avoiding all those messy structures that lead to poor edge stability. 3V will never have the fine edge stability potential of W2, nor will any other complex steel, but you can get pretty darn close. But not with the book HT.

One has to be careful comparing steels though because unless they were all optimized you might be comparing apples to oranges.
Click to expand...
 
It make corrosion resistant sense to me too :thumbup:

Yup, if corrosion resistant is 1st or 2nd on the requirement list, use high cr steels. Coated low&mid cr steels can protect most surface but the edge and exposed surfaces due to wear/scratches. But if toughness is 1st and corrosion resistant is 2nd (or vice versa), well mid cr (3v, pd1, etc..) provides a happy balance for 1 & 2.

If user specs call for ultra high toughness+strength+corrosion resistant blade, there are makers in the center every galaxy would be happy to make/sell 'em some. Bring back some for me too :p

Lo/Rez said:
I started out using W2 and decided to switch to stainless shortly after. The decision was based largely on sharpening hunting knives for people and seeing them come in with blood, hair etc still visible on the blade the next fall. I thought to myself why make a perfectly good knife and sell it to someone who will not take care of it and then bad mouth me and my product when it rusts, when in fact it is their fault. It did not make sense to me.
Click to expand...
 
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