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Carbides in Plane Irons

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D_W

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I make tools. I make other things, but I make more tools than the average person and have come to curiosity about not just making this or that spec, but in feel and use, something that will work really well and invite being used.

Over time, I've learned that I will give up edge life for uniformity because I sharpen fast. Uniformity is a pretty simple concept - the more "same" the edge is across its width, the more "same" the surface it leaves will be and the more "same" it will work each time. Uniformity seems to come most easily with faster abrading steels - I think the reason is two fold - they have very small particles in them, even when there are some carbides, and the steels with fine particles tolerate being driven to high hardness. Separately, even with all other things neutral (like hardness), the steel with the smaller particles and some strength will move or break less at the very tip.

In looking at edge uniformity, I discovered something that I used to think was particles *leaving* the matrix -and that is the carbides. What shows up as dots or matte surface at lower magnification in certain steels is actually almost certainly the carbides remaining in the matrix as the matrix wears around them.

So, I figured I'd take some pictures. There are websites like "knifesteelnerds" that show micrographs of various steels, so you can scale the pictures and make sure your own blades don't have carbide coarsening (not a good thing). So far, I've had pretty good "luck" at heat treatment (experience and experimenting and the desire to do that).

So, I'll show the edge pictures at 300x magnification (the pictures themselves are about .01" tall, or slightly less in actual height, or how do you say it - you could fit something in them that's .0095" tall and it would touch the top and bottom of the picture. You will have not heard of some of these steels, but that's OK. What I'm aiming to learn from these is what they look like vs. how they feel and vs. what they'll take for a shaving. There are some steels like 52100 that would seemingly be a good woodworking steel, but it never shows up in woodworking tools and to my knowledge, never has.

Just to be clear, these don't show up when you sharpen, they only show up after some wear, and I believe most are a little closer to round, but the matrix survives behind them to make what looks like tubes as the carbides bust their way through wood. Micrographs of the steels show their actual orientation, and most of the irons that I make are from rolled material, which orients the carbides in the longer direction if are anything other than round (but they are not long straws like these pictures seem to show).

So, 1084 - just above the eutectoid limit. there may be some vintage plane irons that are made of something similar - iron and carbon and almost nothing else. The eutectoid limit is where the carbon in the steel will not be in surplus at a critical temperature, thus what you end up with is a hard matrix and no visible free carbon forming iron carbides.

1084 Carbide.jpg


52100 (1% carbon, a little of other stuff, including 1.5% chromium, but not too much alloying - probably lower alloy volume than O1)

52100 - carbide from ultra sharp.jpg


Chinese HSS (The irons with the brazing that you see on ebay or chinese sites). This iron is ultra hard (in this group of four ordered, one was sent south to another forum user who wanted to know what was in them, and the alloying is just short of M2 - but the carbides aren't big or erratic, and the brother to this iron tested 65.8 hardness as the average of three strikes. That actually makes it a better iron as it handles that hardness well (higher strength, lower toughness). In the Chinese tool tradition, the listing said the hardness target was 61 on the c scale. Sometimes the errors are good. I've had others of these that are harder yet and they're too hard to hold an edge reliably, and the average individual would never get them flattened.

More alloying and more carbides than 52100 above - look like they're in layers, and the edge looks less uniform, but whatever shape it wears in, it's actually sharper (it may wear flatter and less round - that's not something I can see from straight overhead).
china carbide.jpg


CTS-XHP (an iron that I made, but most likely the same steel as V11). LOTS of carbides - mostly chromium (which is soft as far as carbides go, but slick. Still harder than iron carbides, so good wear. The edge also looks like uneven layers, but XHP is really smooth and easy through wood - not sure why, but less effort planing. Punishes you if you nick it by being slow honing and hot grinding whereas the simpler steels grind cool and hone faster.

xhp.jpg


26c3 - a 1.25% carbon steel relatively similar to japanese white 1 (I though this would look super fine, but the surplus carbon does actually make a lot of visible carbides. It's a strong steel though, but not wear resistant - the edge uniformity is pretty hard to beat and so far it doesn't nick that easily). I expect edge life is a little less even than O1 as there's nothing in it but iron (O1 has tungsten and some other bits), and a small amount of chromium and manganese (but the latter two are in small amounts and are bound in the carbon - not free carbides like chromium carbides in 52100 and V11). This is a steel that beginners probably wouldn't love except it gets sharp - really sharp - on anything. I don't think beginners like steels that have low abrasion resistance, though (I didn't). That said, this is an easy steel for learning freehand sharpening because it doesn't hold much of a burr, nicks ground out reasonably fast, but the hardness makes for a very keen edge. Complaints about edge life are usually solved by using a cap iron and increasing shaving thickness for most of the time a plane is in use.

26c3 carbide 300x.jpg
 

dannyr

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I make tools. I make other things, but I make more tools than the average person and have come to curiosity about not just making this or that spec, but in feel and use, something that will work really well and invite being used.

Over time, I've learned that I will give up edge life for uniformity because I sharpen fast. Uniformity is a pretty simple concept - the more "same" the edge is across its width, the more "same" the surface it leaves will be and the more "same" it will work each time. Uniformity seems to come most easily with faster abrading steels - I think the reason is two fold - they have very small particles in them, even when there are some carbides, and the steels with fine particles tolerate being driven to high hardness. Separately, even with all other things neutral (like hardness), the steel with the smaller particles and some strength will move or break less at the very tip.

In looking at edge uniformity, I discovered something that I used to think was particles *leaving* the matrix -and that is the carbides. What shows up as dots or matte surface at lower magnification in certain steels is actually almost certainly the carbides remaining in the matrix as the matrix wears around them.

So, I figured I'd take some pictures. There are websites like "knifesteelnerds" that show micrographs of various steels, so you can scale the pictures and make sure your own blades don't have carbide coarsening (not a good thing). So far, I've had pretty good "luck" at heat treatment (experience and experimenting and the desire to do that).

So, I'll show the edge pictures at 300x magnification (the pictures themselves are about .01" tall, or slightly less in actual height, or how do you say it - you could fit something in them that's .0095" tall and it would touch the top and bottom of the picture. You will have not heard of some of these steels, but that's OK. What I'm aiming to learn from these is what they look like vs. how they feel and vs. what they'll take for a shaving. There are some steels like 52100 that would seemingly be a good woodworking steel, but it never shows up in woodworking tools and to my knowledge, never has.

Just to be clear, these don't show up when you sharpen, they only show up after some wear, and I believe most are a little closer to round, but the matrix survives behind them to make what looks like tubes as the carbides bust their way through wood. Micrographs of the steels show their actual orientation, and most of the irons that I make are from rolled material, which orients the carbides in the longer direction if are anything other than round (but they are not long straws like these pictures seem to show).

So, 1084 - just above the eutectoid limit. there may be some vintage plane irons that are made of something similar - iron and carbon and almost nothing else. The eutectoid limit is where the carbon in the steel will not be in surplus at a critical temperature, thus what you end up with is a hard matrix and no visible free carbon forming iron carbides.

View attachment 119816

52100 (1% carbon, a little of other stuff, including 1.5% chromium, but not too much alloying - probably lower alloy volume than O1)

View attachment 119817

Chinese HSS (The irons with the brazing that you see on ebay or chinese sites). This iron is ultra hard (in this group of four ordered, one was sent south to another forum user who wanted to know what was in them, and the alloying is just short of M2 - but the carbides aren't big or erratic, and the brother to this iron tested 65.8 hardness as the average of three strikes. That actually makes it a better iron as it handles that hardness well (higher strength, lower toughness). In the Chinese tool tradition, the listing said the hardness target was 61 on the c scale. Sometimes the errors are good. I've had others of these that are harder yet and they're too hard to hold an edge reliably, and the average individual would never get them flattened.

More alloying and more carbides than 52100 above - look like they're in layers, and the edge looks less uniform, but whatever shape it wears in, it's actually sharper (it may wear flatter and less round - that's not something I can see from straight overhead).
View attachment 119818

CTS-XHP (an iron that I made, but most likely the same steel as V11). LOTS of carbides - mostly chromium (which is soft as far as carbides go, but slick. Still harder than iron carbides, so good wear. The edge also looks like uneven layers, but XHP is really smooth and easy through wood - not sure why, but less effort planing. Punishes you if you nick it by being slow honing and hot grinding whereas the simpler steels grind cool and hone faster.

View attachment 119819

26c3 - a 1.25% carbon steel relatively similar to japanese white 1 (I though this would look super fine, but the surplus carbon does actually make a lot of visible carbides. It's a strong steel though, but not wear resistant - the edge uniformity is pretty hard to beat and so far it doesn't nick that easily). I expect edge life is a little less even than O1 as there's nothing in it but iron (O1 has tungsten and some other bits), and a small amount of chromium and manganese (but the latter two are in small amounts and are bound in the carbon - not free carbides like chromium carbides in 52100 and V11). This is a steel that beginners probably wouldn't love except it gets sharp - really sharp - on anything. I don't think beginners like steels that have low abrasion resistance, though (I didn't). That said, this is an easy steel for learning freehand sharpening because it doesn't hold much of a burr, nicks ground out reasonably fast, but the hardness makes for a very keen edge. Complaints about edge life are usually solved by using a cap iron and increasing shaving thickness for most of the time a plane is in use.

View attachment 119820
in summary, do you still think the dots are particles, not pullout?

still look like holes to me, but know it can be deceptive
 

D_W

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They are little dots sticking up - they cast a shadow off of their front ends, and I have a bit of a cheat - someone else has a picture taken head on with a much more expensive microscope and they're clearly little dots sticking up.

The black shade off of the tips of them is a shadow - the light is over the center of the picture and the bevel after it's worn a little bit runs itself downhill.

To some extent, the more carbide volume you have, the greater the wear resistance, but carbides are differing hardness so if you had vanadium carbides in the volume that you have chromium in XHP, you'd have an iron almost impossible to sharpen, but if it could hold an edge, it'd be monstrously long wearing.

10V steel has lower carbide volume, but I've not looked at how high the hardness can be (anything that doesn't temper back to 61 or so will not do great with the fine edge, but once that's gone, would still wear slowly). It becomes a complicated conversation if it gets too deep, and some things aren't that meaningful to us. I haven't been able to find any use for the toughness measure that's typically used for knife steels other than that if something is ultra tough, that means we can make it harder for woodworking and it'll still be tough enough.

52100 is a bit of a puzzler because it's hard *and* tough (whereas O1 can get hard, but it's not a tough steel). O1 seems to be easier through the cut and so far, it makes a better chisel. They last equally long planing wood.
 

D_W

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Stanley sweetheart iron (and it's a sweetheart of an iron - I'd guess 60 hardness based on washita feedback. A little surplus carbon or something in it (so it's not 1075 steel or anything - maybe someone will XRF one of the irons sometime - maybe I"ll do it.).

stanley sweetheart.jpg


Hock O1 - high hardness. Hock says their O1 is 0.95% carbon (O1 has some tolerance, but whether it's 0.9% carbon or 1.05% probably doesn't make any difference any of us would notice)

Very very little visible in terms of carbides. planing further to see if they'd reveal themselves showed little more - any little dots are no more than a micron, and they are few. Very uniform, very well done on heat treat.

I have a house made starrett O1 iron in the toaster oven right now (tempering - as in, I'm making it out of starrett O1, which is what I keep around) to see what they're doing - if it's just O1 and O1 is always this uniform, or if maybe they do something to get all of the carbon in solution and then quench.

hock 01 more wear.jpg
 

D_W

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For a long time, I've run around saying I can make a match for a hock iron. After seeing all of the big carbides in my irons and not much in hocks, I thought I'd better make an iron (i've given away my other O1 irons - it's easy to give something away like a door prize when you can make another one in less than an hour).

So I made one last night, tested this morning (ignore the difference in light - for whatever reason, mine's a bit more reflective, maybe due to the lack of coarse scratches behind the edge - they're effectively the same).

There are things you can do to get more carbon in solution and not have it forming carbides, and they wouldn't cause problems in a forge, but they will cause problems in a commercial heat treat furnace because you don't just snap temp up quickly in a furnace like you can with a forge (they could very well salt bath heat treat them, though).

At any rate, nothing to solve - O1 just doesn't make any big carbides in terms of shapes that will show up in a visual sense.

house O1.jpg


(yes, I just cut and paste the scale in while having the original scaled image open elsewhere to make sure the 20 micron bar is the same size). It's not critical if we're seeing grains of 1 or 1.4 microns or whatever, but the difference between 2 and 10 or 2 and 5 is more useful.

O1 remains king of steels for garage heat treaters who don't want to buy a furnace (I don't want to buy one) or wait for a furnace to do thermal cycling when you can do a shortened version of pre-quench cycling in a forge in about 6 minutes with nothing more expensive than propane. It would literally cost more in electricity for me to use a HT oven than propane in the forge (though the amount is a fraction of a dollar either way).

Before final flattening and grinding the bevel (I bevel them before HT to induce just a tiny bit of warp on the flat side to make them hollow in the middle. Sometimes it helps, sometimes it doesn't do much, but it also makes less hardened steel to finish cutting later).

At some point, I will make a real-time video of making an iron like this. You can do nifty little things like making the slot only a couple of thousandths wider than the wheel on the plane that the iron is for and the lateral adjustment will be divine. You're filing, anyway, and filing to thousandths is sort of a routine thing.

Good O1 steel isn't cheap right now, though, but it is pre-ground and you can just follow the rules and make an iron and have no issue with decarb - this is the first edge on this iron, it's got no bad behavior. Total steel and consumables used for me are about $20 here. For others above, like 26c3, it's half that, and for 1095 or something of that sort, it's even less (1084 may be closer to $5), but they are usually rolled and not surface ground so there may be 10 minutes more work with them and they won't be quite as pretty without you getting after them with fine sandpaper.

Last note - it's tempered to 360F to make sure that it stays hard (right around 400F is probably a little more typical) and matches the hard temper that hock's irons have. I think his are probably tempered at 350F or in that neighborhood - I've never followed to see if he's specified that, but it doesn't matter. I can tell it's something like 325-350F. (the hock that I traced for the slot is below. There are some aesthetics with the hock that I don't care for at all, but most people won't have any regard for that kind of pickiness, and that's perfectly fine). He's got to do something that makes business sense in terms of production speed, and I don't.
20211018_081617.jpg
 

baldkev

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Hi david, do you have lidl over in america? I noticed a thread a while back where everyone seemed to agree the lidl cheapo chisels were fantastic. I guess they would have more chromium in them ( cheaper ones often look shiniest somehow ) anyways, they must presumably be using cheap steel to produce them for the money
 

D_W

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we have aldi - I have a set of chisels that aldi was selling and would guess that they're probably cr60v.

That's a 0.6% carbon steel. I also have a gaggle of harbor freight sets that I suspect are the same thing, but it's possible that some of the sets would've been made with the same chrome vanadium rod but with 1% carbon or 0.9% carbon or something. The price for that vs. 0.6% carbon would be pennies different per chisel and the result between the two with the same quick induction hardening process would be very different.

Someone here in the US had one of the aldi chisels struck and it measured low 60s in hardness, and the ones I have definitely aren't that hard. AT the same time, other aldi chisel buyers here have talked of their chisels being soft. I doubt that the difference between the sets is quality (They're just done in an automated process), but rather that it's using different drill rod at different times.

But that's just a guess as to why some folks think the aldi chisels are great and hold a great edge, and others (like mine) will only really hold their edge well with the help of a buffer. But they do hold a buffed edge fine.
 
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