KnifeForums.com - Intelligent Discussion for the knife enthusiast
Recent Members
Welcome them to our community!
Recent Topics
Recent Hot Topics
Recent Pictures
thumb_1414779645-161120105616.jpg
thumb_1414702399-25630686-f518-4a89-b07f-7854227a9b2d.jpg
thumb_1414357834-101120105588.jpg
thumb_1413801278-100_7971.jpg_big.jpg
thumb_1413312384-Bocote1BF.jpg
thumb_1412800724-1.JPG
thumb_1412652956-24262_1251638018854_7628960_n_1_.jpg
thumb_1412562018-MVP_65b.jpg
thumb_1412353660-2.JPG
Current Quote
"The true test of character is not how much we know how to do, but how we behave when we don't know what to do.
"
~ -John Holt
213 Online Now
20 viewable users (
    ) and 0 hidden plus 193 guests are online now.
     Page 1 of 3 All123
    Username Post: Chromium content in kitchen knives        (Topic#786178)
    oceanman33
    Member
    *
    01-13-07 16:04.04 - Post#1129500    



    What is the ideal percentage of chromium content in a kitchen knife? Is too much chromium a bad thing?
     


    Amadio
    Master Member KnifeNut!
    *
    01-13-07 17:39.14 - Post#1129555    


        In response to oceanman33

    13% Chromium is the standard.
    "Someday I want to be rich. Some people get so rich they lose all respect for humanity.
    That's how rich I want to be."

    ~Rita Rudner


     
    Larrin
    Master Member KnifeNut!
    *
    01-13-07 17:46.10 - Post#1129559    


        In response to oceanman33

    • oceanman33 Said:
    What is the ideal percentage of chromium content in a kitchen knife? Is too much chromium a bad thing?


    It varies depending on the amount of carbon and other alloying elements. The more chromium you have, the more that is going in to solution (for corrosion resistance), but it's also more chromium that is forming carbides (very hard particles that add wear resistance but decrease toughness), chromium carbides are often especially large and segregated, mostly because of the large volume of them from all that carbon and chromium (i.e. 1% C and 18 % Cr in 440C). Just imagine, 12-20% of the steel isn't iron, but chromium. Just having chromium in solution also reduces toughness. There are a couple answers to the heavy banding, segregation, and large size of the carbides: 1) balanced composition, which includes the Swedish grades 12C27, 13C26, and AEB-L, and to some extent steels like AUS-6 or AUS-8; they all have a fairly low volume (2-6%) of very small carbides: .6 micron being the average size in AEB-L, with some as large as 1.2 microns. 2) The Powder metallurgy process, which usually deals with a high volume of carbide (12-25%), but makes that high volume of carbide uniformly dispersed and much smaller: average size of around 2-3 microns, with some as large as 8 microns in stainless steels, and a maximum size of around 5 microns with CPM-M4 or 3V (not stainless).

    440C and ATS-34 have carbides as large as 30 microns, VG-10 slightly smaller. D2, the reportedly "semi-stainless" steel, has huge carbides, with 50+ micron carbides just about everywhere you look, and it's not even stainless. It's all about the alloy balance, D2 has 1.5% carbon and 11% chromium.
     
    ken123
    Master Member KnifeNut!
    *
    01-13-07 18:06.07 - Post#1129575    


        In response to Larrin

    Welcome, oceanman33!

    Larrin, that's a pretty complex answer to someone's first post You're going to scare him off unless he's a metallurgist.

    It's my understanding that, somewhat arbitrarily, 13 % is the percentage where you start calling something stainless.

    People use stainless and/or carbon steel blades in a kitchen, a subject of endless debate here with no single answer. Carbon steel is much more likely to rust or develop a patina and requires more care, but there are excellent knives of both types. Stick around and read and search posts for topics and you could learn quite a lot about this question. After a while, you might want to come back to this post to understand what Larrin wrote. Larrin, you might want to include a glossary of terms

    ---
    Ken
    Facebook
    Nubatama Stones, Diamond/CBN Sprays
    Natural Stones
    Atomas

    Ken's Corner


     
    Larrin
    Master Member KnifeNut!
    *
    01-13-07 18:28.48 - Post#1129593    


        In response to ken123

    13% is an arbitrary number and it only matters how much chromium is in solution. Giving simple replies, while keeping confusion to a minimum, is where misinformation comes from, IMO. I gave up trying to speak English a long time ago. Do you want two paragraphs, or two pages? I'm a little lazy I guess.

    Carbides: I already covered, they're very, very hard "rocks" or particles that are formed from a chemical bond between carbon and iron or alloying elements (chromium, molybdenum, vanadium, etc.).

    Solution: I think this is pretty obvious, when chromium is in "solution" or if there is 12% chromium in the "matrix", than that is what is dissolved in the iron.

    Carbon makes steel hard, it is also what forms carbides. Chromium is a strong carbide former (it likes to form carbides), and while chromium is in solution it raises corrosion resistance. Generally, the more chromium, the greater the corrosion resistance. Almost none of the high carbon stainless steels actually have 13% chromium in solution, they usually have between 10.5-12.5% chromium in solution.

    Wear resistance: The ability to resist wear, or abrasion.

    Toughness: The ability to resist breakage or chipping.

    Strength: Almost directly related to hardness, the ability to resist deformation. Hardness also increases wear resistance. Carbides increase wear resistance because they are very hard. So, simply, if a blade has a rockwell hardness of 60 Rc, and has an evenly distributed carbide volume of 15%, it is essentially a steel that is 85% 60 Rc, and 15% 70+ Rc, depending on the type of carbide. Because those carbides are so hard, it reduces toughness, because generally the harder something is the more brittle it is.

    Anything else that's confusing?

    Edit: oceanman33? That doesn't sound like a metallurgist to you? Of course, I've never seen a metallurgist who had a screen name that looked like a metallurgist, certainly not ilikemetals, or thermodynamicsrox, or chromiumcontent.

    Edited by Larrin on 01-13-07 18:34.38. Reason for edit: No reason given.
     
    bnovy
    Journeyman KnifeNut!
    *
    01-13-07 19:22.43 - Post#1129618    


        In response to Larrin

    • Larrin Said:
    Anything else that's confusing?



    Yes. This was great, by the way, but as long as you're on a roll I figure I might as well ask.

    Somewhere out here is a great post in which someone makes an interesting analogy to nuts in a cookie, or something like that, and I don't believe anyone ever added to it.

    The idea was that the carbides are the nuts, and the dough is what holds them in place. Now, if we're talking about carbides that are often more than a micron in diameter, perhaps tens of microns, then when we try to sharpen stuff with sub-micron grits, we end up trying to shave down the carbide nuts themselves.

    Perhaps if we do that too aggresively, or they aren't held firmly in place, or the remaining bits get too small, then they just fall out. So not only do you get dropouts in the edge of the blade, but you also have little bits of metal on the surface of your stone (assuming you're using a stone), that proceed to mess up the rest of your work.

    I would really like to hear more about the tradeoffs between hardness and size of the carbides, versus the surrounding material that supports them (is this the "matrix", or is that something different?).

    Ah, here's the post I was thinking of.

    Thanks.
    -Bob
     
    nikoz
    Master Member KnifeNut!
    *
    01-13-07 20:04.55 - Post#1129635    


        In response to Larrin

    Larrin,

    Please keep posting in what you call "non English". When it's important to me, what I don't understand, I refer to other sources for clarification or I'll even bother you for detail.

    You have added more to my understanding of the composition of knife steel than any other contributor here. Yuzuha, when she jumps in, provides the necessary analogies to aid my comprehension. It's gotten to the point, that I'm understanding the original premise without the "English" aids.

    Please keep it up. The new guys who are really passionate to learn on the subject, can dip into the archives & bring themselves up to speed.
    Nick

    Questions, questions, always questions.



     
    ken123
    Master Member KnifeNut!
    *
    01-13-07 22:33.21 - Post#1129670    


        In response to nikoz

    Larrin, while you're on a roll, you might also do a little riff on the nomenclature of the steels you mentioned in the post. I really enjoy you're posts, so keep 'em coming. I just wanted to get 'the new guy's' question answered so he could benefit from your knowledge without too much research. Please take my comments in a lighthearted way. I know I'm guilty of this myself sometimes and Nick has called me on it too.

    ---Ken
    Facebook
    Nubatama Stones, Diamond/CBN Sprays
    Natural Stones
    Atomas

    Ken's Corner


     
    Larrin
    Master Member KnifeNut!
    *
    01-14-07 04:06.52 - Post#1129755    


        In response to ken123

    Well there's a book written that is all about how carbides affect sharpness, unfortunately it's written in German. It is a difficult subject to research. I am fairly sure that when you are sharpening with an abrasive softer than the carbides that it is basically impossible to abrade them (i.e. Waterstone is softer than Vanadium carbide). If it is impossible to abrade them they could only fall out if they are larger than the edge. Waterstones are harder than chromium carbide and iron carbide, so they should sharpen carbides in VG-10, white steel, etc., though I think they're softer than tungsten carbide (Blue Steel), and vanadium carbide (S30V). Then the other question is, if you are sharpening with diamond, then you should be able to abrade the carbides, no matter what the size? Right? Well, that's a good question there. I don't understand compressive forces and other complicated factors but I think if you try to grind away at large carbides they may just be falling out, too. I have heard the argument that: "I can get my D2 knife just as scary sharp as anything else!" Well, a steel with no carbides can be just as sharp as one without. However, I have also heard the opposite argument, that they couldn't get their D2 knife very sharp, or at least that it was extremely difficult.

    But then after all the worry about whether we can sharpen the actual carbides or not. When you do get an extremely sharp edge with a large carbide steel (i.e. D2), it loses its scary sharp edge very quickly compared to one with very small carbides (White steel), but once you get to a certain point of dullness (but not really that dull), the D2 will start to hold its edge longer than White steel. I've observed it, and that's what the German Roman Landes postulated, or maybe he observed it as well, translating German is slow going. He does have some nice pictures showing large carbides and the wear patterns on thin edges with different carbide sizes. If the angle of the knife edge is large enough; however, the larger carbide steels won't be as affected by the initial dulling. Push cutting/chopping, according to Roman Landes, is more affected by larger carbides than slicing. He says that slicing is benefited by the high wear resistance of those large carbides.

    Edit: The pictures of wear patterns aren't "real", but drawn.

    Edited by Larrin on 01-14-07 04:11.39. Reason for edit: No reason given.
     
    RMgX
    Master Member KnifeNut!
    *
    01-14-07 07:44.53 - Post#1129924    


        In response to Larrin

    So are the percentages on steels, of carbon and chromium volume percentages? or are the weight percentages or molar percententages?
     


     Page 1 of 3 All123
    Icon Legend Permissions & Sharing Options Topic Options
    Print Topic


    1324 Views
    KnifeForums.com - Intelligent Discussion for the knife enthusiast
    KnifePromotions

    arenaro@verizon.net

    FusionBB™ Version 3.2 | ©2003-2014 InteractivePHP, Inc.
    Execution time: 0.252 seconds.   Total Queries: 168   Zlib Compression is on.
    All times are (GMT-12.0). Current time is 11:09.12
    Top