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Best Knife Steel?
- Thread starter SpyderManBH
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I agree with your definitions, from an engineering point of view, I'm sure they are correct. I mentioned in a previous post about grain size, and how it affects a steels performance. If I'm understanding this correctly, hardness would not be the only thing corresponding to strength, regardless of hardness. Smaller grain size can increase a steels strength without increasing hardness, so hardness wouldn't necessairly predict the true strength. I feel like we're talking about the same thing, but defining it differentlyCould these engineering terms mean something entirely different in metallurgy? Crucible seems to define these thing differently, and that's what I'm confused by. Heck, they don't even mention the word strength throughout the entire article. The only hint I see pointing at strength, is in their explanation of toughness.
The kind of "strength" you're talking about is what happens after you hit the yield point. Before the yield point the internal structure of the steel isn't really a factor because hardened steel has spring - and can bend within a certain range and pop back without the any internal changes to the structure. Springs, for instance, do not take a set if they are used within their designed load range.
When you go past the yield point, that's where the actual structure of the steel comes into play, because you are now damaging the crystal. Brittle steel cracks at this point. Tough steel absorbs that damage with the least measurable damage.
So tough steel does not have a higher yield, it just acts like it does because of how it handles being pushed past yield. For a crude tool like a knife or a jackhammer, this is effectively additional strength. For a precision instrument, you've still gone past yield and the steel has changed shape and structure enough to be no longer useful. In that case the additional "strength" past yield wasn't useful.
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Thanks for the discussion guys. All these concepts I understand, but I had a hard time with the word-game Crucible seems to uses some of these definitions in a vague way, which to people that know what they're talking about, causes confusion. I've always had a hard time explaining things, that's why I studied mathematics in college, I just let the numbers do the talking lol
Crucible seems to uses some of these definitions in a vague way, which to people that know what they're talking about, causes confusion. I've always had a hard time explaining things, that's why I studied mathematics in college, I just let the numbers do the talking lolThis is a quote from what was posted earlier from Crucible: "Toughness ... is the relative resistance of a material to breakage". This is not very descriptive of what is really happening. And actually it is pretty hard to describe with words, easier to describe with an example so I'll try that. Plus consider that tool steels used in knives are a special case, behavior of most other steels is easier to understand. Everybody has probably played with wire coathangers- bending them in different shapes, trying to straighten them out, whatever. So pick up a wire coathanger and start bending it in your hands. Up to a point you can bend it and it will return to its original shape. Behond that point and it starts to take a permanent bend. This point is where stresses in the steel have reached its yield point. One property of most steels is its "yield strength". If you keep bending it, it deforms more. You can bend it a lot before it starts to crack so it has a high toughness. In the words of Crucible, it has a high resistance to breakage because it didn't break. This is how strength and toughness are 2 different things.
Now lets consider a higher strength steel, maybe the shaft of a small diameter screwdriver. If you had a piece of this steel similar in diameter to the coathanger wire, and you started trying to bend it, you would find that it takes a lot of force before you reach the point at which it starts to take a permanent bend. This means that its yield strength is much higher than the plain coathanger wire. If you keep bending it past this point you would find that it would not deform as much before it would break. So since this metal did not bend as far before fracturing you would say that it has less resistance to fracture, or lower toughness.
Both of these examples used bending to take a material to its yield point and then take it farther to its fracture point, giving a form of measurement of both properties. So a "bend fracture test" is a perfectly valid test.
If you could see a Charpy v-notch test in action you could easily understand the concept of toughness. It has been a long time since I watched this so I will give a description of the concept involved. Visualize a 3' or 4' long rod, hanging from a pivot below the ceiling. Now connect a small anvil to the bottom of this rod. Next on the bottom of the anvil weld on a small piece of a chisel with the sharp edge pointing to one side. On the floor below the anvil bolt down a very strong fixture, maybe a vise. Now cut a sample of steel bar about 1/2" square and a couple of inches long, and clamp it in the vise end to end. The vise is positioned where the chisel point at the bottom of the anvil is almost touching the steel bar. Now pull the anvil as far away from the steel bar as you can, then let go of it. It will swing down, hit the steel bar, and try to bend it or break it. A good ductile or tough steel will bend a lot before it lets go and the chisel point can go past. In the process it absorbs a lot of energy from the pendulum. The measure of toughness is the measure of how far the pendulum goes after hitting the sample. If the sample was brittle, it would quickly break and let the pendulum keep going.
A point of confusion is that this is an impact test. It is an old test and though crude it is a simple test of the toughness of steel. But just because it is an impact test do not be confused that "toughness" is only an impact property. It applies for static loading also- stick the end of your knife in between 2 things and try to pry them apart. You are not applying an impact load but the toughness of the steel is still important here.
There are numerous videos on youtube of charpy testing:
https://www.youtube.com/watch?v=tpGhqQvftAo
I'm sure if you were looking up steels, you would have found that there is no "best" steel out there since opinions vary so much. There are better steels for certain tasks. Its about as ambiguous of a question as "what knife should I buy" without giving a budget.
For woods blades, 52100, 1095, 1080, 5160, and O1 are all good to go in my book. Hold a edge fairly well, easy enough to sharpen. D2 was a bit underwhelming for me. I have a 3V on the way that I'm dying to try out.
I've tried some of the super steels. Never got overly enamored. 154CM/ATS34 and S30V seem to do me just fine. Great corrosion resistance, hold a edge very well for my EDC tasks (which aren't that demanding on a blade)
For woods blades, 52100, 1095, 1080, 5160, and O1 are all good to go in my book. Hold a edge fairly well, easy enough to sharpen. D2 was a bit underwhelming for me. I have a 3V on the way that I'm dying to try out.
I've tried some of the super steels. Never got overly enamored. 154CM/ATS34 and S30V seem to do me just fine. Great corrosion resistance, hold a edge very well for my EDC tasks (which aren't that demanding on a blade)
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Sorry for not responding quickly guys.
I'm looking for a fixed blade for outdoor activities, nothing particular, i want something that is going to be able to handle multiple tasks.
Ill use it for skinning animals, basic cutting, cutting tinder and other thing like those.
I'm looking for a fixed blade for outdoor activities, nothing particular, i want something that is going to be able to handle multiple tasks.
Ill use it for skinning animals, basic cutting, cutting tinder and other thing like those.
- Joined
- Apr 22, 2015
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Thank you for the advice, Ill be sure to keep questions more specific in future posts.
I would be more concerned with blade geometry (hollow, flat, sabre, convex) and blade shape/length than with steel.
In particular, I find that meat processing, food processing and wood processing all do better with different blade grinds; hollow, flat and convex/sabre respectively.
If I had to pick one knife to do all that you described, I would take my old modified H-15. It handles meat processing OK (not as well as others, but OK), is thin enough to handle food processing and works wood well due to the sabre grind.
If you feel like you just stepped outside into a hurricane, just get a Mora Companion (not the HD version, just the basic one) in stainless. It will handle everything you've described and after using it for a year (keep it in the kitchen and use it daily) you'll have a better handle on preferences. Another inexpensive experiment knife is the Buck Bucklite Max fixed blade. The more is a thin scandi (similar to a sabre) and favors wood working and the Buck is hollow ground and favors hunting. Both have really good (enough) steel.
Your opinion after a year's use of both will be more important than pages of noise on the forum.
Schrade H-15 Modified by Pinnah, on Flickr
RamZar
Gold Member
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- 11,630
Knife Steel Properties courtesy of Crucible:
Hardness is a measure of a steels resistance to deformation. Hardness in knife steels is most commonly measured using the Rockwell C test. Hardened knife steels are generally about 58/62 HRC (hardness Rockwell C), depending on the grade. Most are typically about 58/60 HRC, although some are occasionally used up to about 62 HRC.
Knife edges which plastically deform in service possess insufficient hardness. Permanent bending of the blade or permanent deflection of the cutting edge indicates insufficient hardness. Because a steels resistance to permanent deflection is directly related to the hardness, not the grade, corrective actions for deformation may include increasing hardness, or decreasing operating loads by increasing blade thickness. Changing grades will not help a deformation problem, unless the new grade is capable of higher hardness.
Toughness (impact resistance), as considered for high hardness knife steels, is the relative resistance of a material to breakage, chipping, or cracking under impact or stress. Toughness may be thought of as the opposite of brittleness. Toughness testing is not as standardized as hardness testing. It may be difficult to correlate the results of different test methods. Common toughness tests include various impact tests and bend fracture tests.
In service, wear failures are usually preferable to toughness failures (breakage). Breakage failures can be unpredictable, catastrophic, and even a safety concern. Conversely, wear failures are usually gradual, and can be anticipated and planned for. Toughness failures may be the result of inadequate material toughness, or a number of other factors, including heat treatment, fabrication (grinding abuse), or a multitude of usage issues. Toughness data is useful to predict which steels may be more or less prone to chipping or breakage than other steels, but toughness data cannot alone predict the performance life of a knife.
Wear Resistance is the ability of material to resist being abraded or eroded by contact with work material, or outside influences (dirt, grit, bone, etc.) Wear resistance is provided by both the hardness level and the chemistry of the knife blade. Wear tests are quite specific to the circumstances creating the wear and the application of the knife. Most wear tests involve creating a moving contact between the surface of a sample and some destructive medium. There are 2 basic types of wear damage in knives, abrasive and adhesive. Wear involving erosion or rounding of edges is called abrasive wear. Abrasive wear does not require high pressures. Abrasive wear testing may involve sand, sandpaper, or various slurries or powders. Wear from intimate contact between two relatively smooth surfaces, such as steel on steel, carbide on steel, etc., is called adhesive wear. Adhesive wear may involve actual tearing of the material at points of high pressure contact due to friction.
Corrosion Resistance is a measure of a knife steels resistance to attack in high humidity, damp, or salt environments. This resistance is established by the addition of chromium to the composition. Developing corrosion resistance in a heat treatable, wear resistant steel is a challenge that has been met with numerous specialty CPM alloys. Relative resistance is often measured in salt spray and water spray environments.
Knife edges which plastically deform in service possess insufficient hardness. Permanent bending of the blade or permanent deflection of the cutting edge indicates insufficient hardness. Because a steels resistance to permanent deflection is directly related to the hardness, not the grade, corrective actions for deformation may include increasing hardness, or decreasing operating loads by increasing blade thickness. Changing grades will not help a deformation problem, unless the new grade is capable of higher hardness.
Toughness (impact resistance), as considered for high hardness knife steels, is the relative resistance of a material to breakage, chipping, or cracking under impact or stress. Toughness may be thought of as the opposite of brittleness. Toughness testing is not as standardized as hardness testing. It may be difficult to correlate the results of different test methods. Common toughness tests include various impact tests and bend fracture tests.
In service, wear failures are usually preferable to toughness failures (breakage). Breakage failures can be unpredictable, catastrophic, and even a safety concern. Conversely, wear failures are usually gradual, and can be anticipated and planned for. Toughness failures may be the result of inadequate material toughness, or a number of other factors, including heat treatment, fabrication (grinding abuse), or a multitude of usage issues. Toughness data is useful to predict which steels may be more or less prone to chipping or breakage than other steels, but toughness data cannot alone predict the performance life of a knife.
Wear Resistance is the ability of material to resist being abraded or eroded by contact with work material, or outside influences (dirt, grit, bone, etc.) Wear resistance is provided by both the hardness level and the chemistry of the knife blade. Wear tests are quite specific to the circumstances creating the wear and the application of the knife. Most wear tests involve creating a moving contact between the surface of a sample and some destructive medium. There are 2 basic types of wear damage in knives, abrasive and adhesive. Wear involving erosion or rounding of edges is called abrasive wear. Abrasive wear does not require high pressures. Abrasive wear testing may involve sand, sandpaper, or various slurries or powders. Wear from intimate contact between two relatively smooth surfaces, such as steel on steel, carbide on steel, etc., is called adhesive wear. Adhesive wear may involve actual tearing of the material at points of high pressure contact due to friction.
Corrosion Resistance is a measure of a knife steels resistance to attack in high humidity, damp, or salt environments. This resistance is established by the addition of chromium to the composition. Developing corrosion resistance in a heat treatable, wear resistant steel is a challenge that has been met with numerous specialty CPM alloys. Relative resistance is often measured in salt spray and water spray environments.