115crv3?

[Aiden CC]

I recently decided to try out this steel, sometimes referred to as "silver steel," for some puukkos and I've had some problems with cracking. There isn't too much info (at least that I can find) about heat treating it, so I figured I would see if anyone has used it or has any insights. Here is the process based on what I have been able to find and my results so far:

 

-Forge to shape

-Normalize once "by eye" in the forge, air cool (well, technically in sand but just the tip to hold the blade upright)

-Grind to 60 grit (maybe this is too coarse? These knives are zero ground so I go back to 60 after ht anyways so it feels like a waste to go higher if it isn't necessary)

-5 Minutes at 1475 F, air cool

-5 Minutes at 1425 F, air cool 

-Austenize 10 minutes at 1475 F

-Interrupted quench with water and canola oil (6 blades, 1 cracked 1 warped and cracked in straightening during second temper, all had some "sori")

-Canola oil quench (1 blade, cracked but didn't open due to less distortion and only showed up during grinding)

-Temper 375 F twice for two hours

 

For reference, here's the steel's composition:

 

C:                  Mn:                Si:                   P:          S:          Cr:           Ni:    V:               Mo:    W:

1.10 - 1.25    0.20 - 0.40    0.15 - 0.30    <0.03    <0.03    0.5 - 0.8    -    0.07 - 0.12   -         -  

 

I ordered some Parks 50 to try, which may help as well. Thanks for looking and any insights/suggestions are appreciated!

[Gary LT]

Aiden, I also have wanted to try silver steel.  I used to use O1 in 9/16” round and would do round silver steel as well. (I realize it’s not the same stuff but as example)
But I would not grind at 60 grit, too rough, IMO, and certainly would not quench in water even interrupted, (but others might.) Using oil, canola should be warm, (at least 110F). I do full blade quench, (point first, at an angle) and never a crack or warp.

What temperature are you forging at and are you reheating often enough? I have a tendency to keep hammering…
Gary LT

Edited December 2, 2021 by Gary LT
Wording

[Jerrod Miller]

I would recommend grinding to a finer finish for better results during heat treat.  I would say a 220 minimum to be safe, but 120 may be enough.  You also have some decent carbide formers there, so I would recommend a normalization cycle going quite a bit hotter, like even 1600F.  And just hold onto the blade for the normalization.  It takes about a minute to cool from high temp to black.  Be patient and watch it while holding it.  I would then normalize again at a lower temp before grinding.  Then grind, normalize another time or 2, then harden.  I'd also start with a straight canola quench and see if that gets you the results you are looking for.  If not then you can move to something more aggressive (or less if needed).  And anything that has the potential for a pretty fair amount of retained austenite should get 2 complete tempers before starting to try correcting warps.  

[Doug Lester]

My sympathy on the crack.  Nothing breaks your heart like grinding you blade and thinking that it is coming along fine just to move up to a finer grit and seeing that the blade has cracked.  Not that has ever happened to me.

 

Doug

[Aiden CC]

Thanks everyone!

 

Gary, some of the blades were briefly at a welding heat when I forged welded a mild steel tip onto the tang, but I think I had pretty good temperature control after that. Last few heats were lower but only for straightening before normalizing. 

Here is the grain in the break. The dark section is oil that got into a crack in the quench, it's hard to see in the photo, but it isn't oxide from being open at temperature, it has a wet appearance and slowly spread over time.

 

Jerrod, I'll try out normalizing in a furnace instead of the forge to make sure I get a higher temperature and go up to a higher finish before hardening. Also I'll delay straightening until after a second temper. Does retained austenite act differently in the small volume fractions in high carbon martensitic steels than it does in something like TRIP/QP steels? It seems like it can increase ductility to a certain extent, right? 

 

Doug, that's quite true. I had another crack show up in the hand sanding stage for one of these after I had fit a handle etc which was quite unfortunate. 

 

I have a bit more of this steel on hand and some more on the way, so I hope to have some redemption with a second batch of these.

[Jerrod Miller]

Retained austenite can increase ductility, but after your first temper cycle some of that austenite has converted to un-tempered martensite, which is the problem that the second temper is there to solve.  

[Aiden CC]

That makes sense about straightening and the second temper, thanks Jerrod. It's possible I've gotten away with it in the past because I've mostly been doing minor adjustments to thinner knives, primarily in 80crv2. 

 

I had hoped to make a new batch of knives with this steel and try out the suggested changes, but it may have to wait a bit. If I remember I'll post the results here.

[David Weaver]

visiting this a few years later. I'm hoping to forge this rod to make chisels, round stock that is. 

 

There's only one source in the US that I could find that deals in one rod at a time, and I'm coming up with a real fight on my hands to get open air heat treatment numbers that come close to the book numbers. 

 

It's not my first rodeo (i can get aeb-l open air heat treated by eye to 61 after double temper, 52100 to 68/69 out of the quench with no visible growth - to make stitchers/gravers, and I've got a lot of 26c3 chisels tapered out of flat stock and hardened to 64 with a double 390F temper and better toughness than the oven stats - courtesy of larrin T testing some coupons for me). 

 

But I'm getting about 61 before temper out of this stuff, and even with a cutoff sample directly into water quench, I'm getting about the same. made my question my hardness tester for a bit. Pushing the limits on heat before quenching just blows up the grain (looks great, similar to the samples above with regular routine). 

 

if you ever figured out what this likes, I'd be glad to hear it. I was hoping for 62/63 after temper in chisels. the HT routine looks not too much different from 52100 - temp for oven purposes around 1500-1550 if quenching in oil and a little less for water. I'm stumped. 

[David Weaver]

did a gaggle of test pieces with different quenches yesterday and Quenched W1 and O1 in the same oil (O1 is obviously not similar), and everything came out on target. 

 

looking around, I've seen folks suggest working things into solution like you would do with 52100 and the same routine that brings 52100 to very high hardness still brings this to about 60 out of the quench. 

 

I'm beginning to wonder if the bars that I got aren't what they say they are, and as I don't have nital (I do have a metallurgical scope), the only easy way for me to make sure there is excess carbon in a plain steel is to hammer out a plane iron and then wear off some of the matrix to get an idea of the size and array of carbides, like this (52100). 

 

 

Bummer if the stock isn't what it says. I've had super luck making chisels out of 26c3 - 2 points harder than O1 for me and tougher according to larrin's notcher (not on his results, but my samples averaged around 12 ft lbs at 63.8). I was hoping this would fill the void of 26c3 not be available in round bars - it's so hand and eye heat treat friendly. 

Correct one thing above - larrin's charpy/toughness tester - I think he does not notch coupons. 

[David Weaver]

I think I may have figured out what's going on. Graphitization in the snapped samples seems to be an issue with 115crv3, but it is not observed in an old file forged into a test sample the same way (high heat, hand hammered).

 

Subsequent heats don't seem to do anything for this, and I have not yet cut a sliver off of the round bar to see if the steel itself is already like this before forging. 

 

this is the snapped sample from the file (brand unknown, but extremely high carbon and smokes like a train when grinding it if you're familiar with grinding steel high carbon enough that the grinding point looks almost like a flame). 

 

This is approximately 100x optical. Sort of my normal thing (i realize a lot of people don't care for hand and eye heat treatment, and that's OK). 

 

hardness out of the quench is 68, which is what I would expect. Sample 0.15" and three inches long tolerated a brine quench without issue, but I usually use parks and push heat quickly before quenching and get the same hardness and grain look (and it's a lot safer). I do not hold steel at temperature but rather do something that's more like induction hardening, which is in fact what I used for this. two normalization cycles after forging, then three grain refinement cycles cooling to black and then a heat to just past nonmagnetic and then a quick ramp up for seconds. If this sounds like something a martian would do rather than a sensible person who would just by a furnace, i get it. 

 

Anyway, 115crv3, same sized stock, identical forging process, identical follow up - and brine. 

 

 

 

The only thing I see similar to this online is research pictures of graphitization, but there are several causes listed for it (heat of forging, problems in steel manufacture, and also can occur with steel in service at below critical temperatures. 

 

I can't get access to any of the articles to find out much. Strangely, this sample tests around 62/63 depending on where it's tested, and the sample did not break as easily as would be expected. 

 

My heats are relatively high for hand forging from rod, but not sparking or anything like that. Just hot enough to scale. 

 

I am a toolmaker and not a bladesmith, and wouldn't have thought to even look at this were it not for hardness being low. 

 

The first sample looks good to me - files >1% by a lot never make a matte gray appearance, but the carbides look nice and evenly distributed. 

 

I don't know for sure that the large bright spots are carbides in the second picture, but the snapped sample is outright ugly. I've never seen anything like this in other broken samples. 

 

 

 

 

 

 

 

 

 

 

[David Weaver]

following up on this one person conversation and solving problems. Before jumping to the conclusion that forging caused the problem with graphitization, i wanted to both heat treat a sample straight off of the annealed bar (just cut off, no forging, no extra heat treatment other than a set of normalization cycles, thermal cycles following that and a little bit pushed heat prior to quench). 

 

The underhardening continues - the sample that's just cut tests at 60. Forged bars of W1 (67), O1 (65) and an old file (68/69) all came out fine with the first two being quenched in parks50 (straight in, no movement after with O1, W1 in parks with movement to increase quench speed and the file was quenched in brine as parks 50 wasn't fast enough in .15 cross section. 

 

I have read elsewhere that 115crv3 should be a little deeper hardening than 26c3, but I'm not seeing it with my samples - not close. I get 68/69 out of 26c3 without any sign of grain growth. 

 

So, something is bogus here or there is just something about the alloy where it's not intended to be used for cross sections that I like (.09" to .15"). 

 

Seeing the graphitization in the bar without forging or much high temperature is a relief. the only difference is some of it is in banding/planes in the bar and the forging seems to have eliminated that in the samples I've looked it - it's dots. 

 

In the thinnest of cross sections (about .08"), I was able to get a test  hardness of 64 out of the quench, but a single half hour temper at 355F in a stable aluminum bar sandwich with an embedded thermocouple drops the hardness to 58.5. 

 

The solution to the problem is one I don't care for too much with four bars of this stuff on hand - there's almost nothing I could think of where it could be used in terms of knives or tools. 

 

two pictures of a sliver snapped just cut off of the bar, top flattened to hardness test, about .1" thick, finished finely and then heat treated. No high heat:

 

 

This is only the second time I've had steel where snapping it showed things I really don't want in steel. The last was 1095 that hardened OK, but was full of what looked like undissolved chromium (the 1095 in that case had a fraction of a % of added chromium even though I guess it's not in a 1095 melt in some cert sheets

 

 

that's a picture of the 1095 mentioned - it was just cut and heat treated to be used in a woodworking plane. Snapping other samples showed bright spots like this widely dispersed and a little too common. the dots are, of course, carbides. the smallest are about 1 micron - the picture in this case is very high magnification vs. the snapped samples. Less than 1 thousandth of an inch from the top to the bottom of the picture. This defect may not matter on a knife, but on a woodworking tool, there is a line left by the different edge area - something that can't be tolerated.

 

Case closed for the 115crv3 here - I have no access to a different sample. The company selling the 115crv3 in the US is German, but there's no other information about the bar other than the grinding standard as the bar is intended to be used as a bar, and not forged into something else.  

 

[Jerrod Miller]

From what a little bit of digging is showing me, you are getting pretty close to what you should expect.  62+ HRC as quenched (in water, presumably) is expected with proper heat treat.  I think you're definitely going to need to etch the sample if you really want to see what is going on.  It is really the only way you will be able to clearly see graphitization, carbides, martensite, and retained austenite.  The higher Cr and comparable Mn should definitely be making this a deeper hardening alloy than 26C3, but keep in mind that that does not mean it is going to be harder.  How are you hardness testing?  Are you sure you are getting through any decarb layer that may be present?  When you are heat treating, are you watching for decalescence and recalescence, or just going "a bit past non-magnetic"?  

[David Weaver]

I'm hardness testing with a portable diamond cone hardness tester. it's been reliable through a couple of hundred samples, and hits calibration without issue. the response to tempering is unusual (64 hardness drops to mid high 50s, and if you do some diamond dent testing, you'll know what I mean when I say the dent size tells the same story - it's unusually large after a 350F temper). 

 

As far as hardening, I'm giving this a similar treatment to 26c3, which is to get the steel to nonmagnetic and then give it a quick ramp past and quench, though I held it at nonmagnetic with intermittent heat for ten minutes and as expected. Since I work typically with things that don't need a furnace soak to match book spec (if done correctly), I've got to work up a method to hit book (or sometimes slightly harder) quench hardness and temper results, and get decent toughness. it's never been difficult to find the sweet spot if snapping samples and examining what's going on (larrin tested my O1 samples at book, 26c3 is upper book range for hardness and better toughness than book by a wide margin).

 

So, here's the deal with the quench hardness. Thin cross section, proper heat gets 58-60. A very thin cross section pushing the limit and using brine will get 64 but with a 350F temper (single and not long duration) the 64 is gone. The sample still breaks without issue - if you've ever snapped 52100 without it being high hardness out of the quench, you'll gather what I mean by that - it's a booger even fully untempered if it's only 61 or 62 out of the quench, but if you push it to its upper limits to make something like an engraving tool, it behaves in the break more like a 26c3-like steel.

 

Listing for the steel in this case suggested hardness up to 64. Hardness and tempering charts suggest 64-66 with relatively little loss of hardness in a 200C temper. I've mentioned the problems to the seller to see if they'll perhaps leak that maybe it's not what it's listed to be. 

 

I can identify carbides with the pictures above - you can see them in snapped samples, but the plane iron test shown above is more reliable as the wood will wear the matrix around the carbides without breaking the carbides themselves, at least until you get to about 1 micron size carbides. When I scale the photos against precision wire, I don't find anything smaller than that, which suggests 1 micron is about the smallest a carbide will create a shadow. You can see the graphitization in the snapped samples, but you are correct about austenite and martensite. I don't have a means to test that. 

 

it's maybe not obvious what the last picture is, but that edge starts out flat. The mechanics of the hand plane push the wood that's severed down into the tip of the iron and wear off a strip that's scoop shaped a few thousandths of an inch long. it's a superb test, but it does require an iron that will plane wood. For reference of what you'd compare to a micrograph, here is a worn edge of 1084 

 

and one of CTS XHP 

 

this might be a little unconventional, but I have the means to do this and hardness testing, or snapping, and lost my ability to get freebie XRF services with the retirement of a friend. Haven't ever delved into retained austenite. I'm a hobbyist. I'll give you an idea of what I expect out of 26c3 in the next post, which will illuminate why this very superficial surface on the 115crv3 is unexpected. 

[David Weaver]

This is what I would typically make - chisels:

 

 

these are 26c3, they're hardened and tempered in a straight taper, and then ground to final size, which removes a good bit of surface material. I've never had the first half of a chisel test lower than 63 after a 400F double temper and never higher than 64 (neither top nor bottom regardless of the amount removed grinding). I think 26c3 is a dream to work with if the cross section allows good through hardening in parks. it's very tolerant of hand and eye heat treatment. the second half of the chisel toward the tang thickens and is not heated to the same level and progressively transitions down to only partially hardened below the bolster. This is also a dreamy thing for chisels - they are stiff, but they will not break easily. 

 

if I could get 26c3 in round bar to be able to forge the bolster integrally rather than fitting and forge welding it in place before filing it, then there would be no post here. that's how I got here. Making the sometimes mistake that since i've never had any issue that wasn't pretty easily solved that 115crv3 would be an easy substitute. 

 

W1 hardens fine. 

 

I understand that the quick heat higher than what a furnace schedule would be is unconventional, but when I bounced it off of larrin, he mentioned that induction heating industrially does the same thing. I came to it by, unsurprisingly, testing samples and finding that without the soak, just going to nonmagnetic for a brief period is substandard. hardness is key in chisels, and toughness is secondary, but it has to be "enough". Much different than the knife world where toughness is king and hardness is perhaps secondary (but you expect both to be dead nuts on something that isn't low cost production). 

 

Thanks for the reply, by the way. Though I've sort of drowned the topic in detail in getting to the conclusion, I learned something along the way - i was always afraid of the distortion that a brine quench would introduce, but it will be viable on some types of chisels. 

[Alan Longmire]

I suspect any of the CrV series is not going to be great for plane irons and chisels, and it's the chromium carbides that are the problem.  Unless you're starting with a PM steel OR something like AEB-L / 27c13 that naturally have tiny carbides, you're going to need a longer soak to dissolve those chromium carbides you get with any hypereutectoid steel.  Larrin talks about that in great detail, how higher carbon doesn't always equal better when you add chromium to the mix.  It'll be extremely wear-resistant, but the edge is going to be full of big clunky carbides.

 

I totally get why you want a round bar starting stock, I do integral skinners that require that as well, and it annoys me that the only hardenable stainless I can get (easily, anyway) in 1/2" round is 440C.  But I do have a furnace, and I'm not afraid to use it.   Given your HT setup I think you'd be best served by using the steels you know work well for you.  

[Jerrod Miller]

2 hours ago, David Weaver said:

I can identify carbides with the pictures above - you can see them in snapped samples

Bright (white) indications in a snapped surface are not always carbides.  They can be flat planes that are reflecting light.  A polish and etch is the best way to see carbides.  

 

2 hours ago, David Weaver said:

You can see the graphitization in the snapped samples

Similarly, you do not show any pictures of anything that I would say are definitively graphitization.  

 

2 hours ago, David Weaver said:

As far as hardening, I'm giving this a similar treatment to 26c3, which is to get the steel to nonmagnetic and then give it a quick ramp past and quench, though I held it at nonmagnetic with intermittent heat for ten minutes and as expected.

This doesn't really say what is going on.  Non-magnetic means about 1415F.  "A quick ramp past" is completely undefined.  How hot are you getting, how long does it take to get there, and is there any holding time (even a few seconds)?  

 

51 minutes ago, Alan Longmire said:

it's the chromium carbides that are the problem

As Larrin states in this article:  "The chromium doesn’t lead to the formation of chromium carbides but may help a little with keeping the carbides small."  

 

Very high carbon steels like this can be quite tricky on heat treat, and not just the final heat treatment.  Iron carbides dissolve pretty readily at critical temperature, and really fast when you go further above critical.  Chrome carbides take a bit more time and heat to dissolve.  WC, VC, NbC and the like take even more.  Small amounts of chrome generally stay in the steel matrix as substitutional atoms.  Of course, there will always be some that find some carbon atoms and form carbides, but most won't at this level.  This is why the TTT diagram will shift with the Cr additions.  If they are tied up in carbides, they are no longer part of the steel and thus will not impact the TTT.  Depending on what gets put into solution during austenitization, your results can be significantly different at the end.  Iron and Chrome carbides generally tie up multiple metal atoms along with multiple carbon atoms.  This is why they tend to be larger carbides, it is (relatively) hard for them to start, but easier to grow.  Especially when we look at things like "chrome carbides" that are M7C3, we will rarely find Cr7C3, there will typically be a good deal of Fe instead of Cr (e.g. Cr3Fe4C3).  Unless you are going to throw the sample in an SEM or some such, you won't know that they really are.  The carbide chemistry is generally driven by the Cr:C ratio.  The others (VC, WC, etc.) are one-to-one metal atom to carbon atom, so they form more readily and thus present as smaller and more dispersed carbides.  They also form at higher temps, so they crab up more of the free C and are less likely to end up as substitutional atoms in the matrix.  

 

@David Weaver If you would like to and can send me a sample that is at least 1" diameter and 1" thick, I can run it on my spectrometer and see how close it looks.  We don't make any alloys that are especially close to 115CrV3, thus I don't have a calibration standard especially close to that; but we do a fair few things and my spectrometer is less than a year old, so I think I could get a fairly accurate reading.  Send me a PM if you want to set something up.  

[Alan Longmire]

I was thinking the extra chromium in 115CrV3 (0.8%) would be more problematic as compared to the 0.3% in 26c3, but I certainly bow to your experience!  I need to re-read some things...

[Jerrod Miller]

With 0.8% being the maximum, I think it is safe to assume we will generally be closer to 0.65-0.65.  And you definitely will start to see some Cr carbide, just not lots of it.  It will definitely help having that much more carbon in there for the Cr to find and bond with.  There will not be a lot, and what is there will be small.  My go-to calculator for this is designed for high chrome white iron, so it isn't accurate for steels (it predicts a slightly negative carbide volume fraction).  It also predicts that the Cr carbides will all be Cr2Fe5C3 (the formulas used do not go below that ratio, and I am not really sure if Cr1Fe6C3 can even exist outside of lab environments).  That being said, when Cr is less than about 2%, pretty much all you are going to get is (Fe,Cr)3C.  Being in the commercial casting field, we tend to not pour steels that would be good for blades (but there are a few exceptions to that).  As such, I have mostly seen things with either much lower or much higher carbon content.  I have a few chunks of tool steel on my desk right now waiting for their turn under the scope (fracture analysis, not micros).  At more than 3% Cr the only carbides I see in the quenched and tempered (air hardening) state of this alloy are few and all near-micron in size (can't see them until 500x).  I just looked up a picture from ASM of 5160, and boy howdy are those carbides tiny, even at 1000x!  Great sizes to pin grain boundaries a little, not so big as to do much else.  When carbides are that small they get ripped out of the matrix as the martensite is worn away around them before they can really be noticeable (my eye can't detect sub-micron scratches very easily).  

[David Weaver]

On 9/8/2023 at 4:03 PM, Alan Longmire said:

I was thinking the extra chromium in 115CrV3 (0.8%) would be more problematic as compared to the 0.3% in 26c3, but I certainly bow to your experience!  I need to re-read some things...

 

I've read a little further about the DIN cold work steels with surplus carbon. Above and beyond silver steel, the steels can be graphitized on purpose (are or can, not sure which is most appropriate here). I am still on the prowl for 1.25% carbon steels, but ad copy from a local metal supplier suggested a 1.5% carbon steel that's graphitized so that the steel can have some self-lubricating properties. I don't have any clue if that was the problem with my sample - it seemed more flat out just not hardenable, but it does illustrate some potential danger for us making blades. If we see a 1.4% steel and assume that we can really heavily forge it and still have surplus carbon left, there's a non-zero chance that the processing did not anticipate what we're doing, but rather self-lubricating rods for drive systems. 

 

This also answers some prior questions that people like me would've had when buying steel from knife suppliers - like there are W1 and O1, but many others of the series that we don't see much of. O6 with the hardenability and high carbon content seems like asking for trouble with toughness, but the ad copy says "The tiny graphite carbon particles are distributed evenly throughout the tool steel essentially create _____". The text goes on to say the same thing, that they provide self lubricating qualities. I think for any practical purposes, graphite is a stable enough state that it's not going to contribute to the cause we want with blades. 

 

One other side thing that I've figured out - 52100 is kind of hard to get right (to me, that's really pushing the upper limits of hardness without bloating the grain - that's what makes a good chisel), but I've handled that at this point, too, and can get 64 hardness after 400F double temper without issue. Thus, It just sort of seemed like the 0.8% chromium in 115crv3 would be somewhere between and no big deal. In the end, I relayed what I did and what I was seeing and the supplier gave me a refund. But if I find it elsewhere, i'm game for another shot at it. 

 

 

[David Weaver]

On 9/8/2023 at 1:53 PM, Jerrod Miller said:

@David Weaver If you would like to and can send me a sample that is at least 1" diameter and 1" thick, I can run it on my spectrometer and see how close it looks.  We don't make any alloys that are especially close to 115CrV3, thus I don't have a calibration standard especially close to that; but we do a fair few things and my spectrometer is less than a year old, so I think I could get a fairly accurate reading.  Send me a PM if you want to set something up.  

 

I have 20mm rod, unfortunately, so nothing that will make a 1" thickness. I'm supposing some things when I talk about heat treatment - like what is probably large grain and what probably isn't, I've got a pretty good handle on that from seeing large grain in snapped samples. Not that it's perfectly uniform. 

 

Snapping samples of round rod has also clued me in that not everything is perfect  -this is what I see in a forged 52100 sample, and then to confirm it wasn't me creating that, I cut a segment off of the round bar and just quickly heated it and quenched, and it's the same. 

 

I don't have the ability to do any better analysis than looking, but the bright bits were initially concerning. A better scope (visual, so limited depth of view) shows this, but I never use the second scope like this so other than seeing that it's not one big bright flat ingot, I can't discern much else from this. 

 

This snap double 400F tempered at 64 hardness. The snap sliced off of the rod, I didn't temper, but ground a flat on the outside to hardness test showed about the same quench hardness. 

 

This steel look bad snapped, but chisel made from it is good. That's my end use, and there could very well be issues that are flaws for something else, but I scope the edge of a chisel compared to a large number of others (vintage and new) and go from there. 

 

the only other thing within my means is perhaps getting nital and etching a few samples to see if I can get a general idea on grain size. 

 

Everything else is way over my head - but fortunately. I swore at the outset of making tools that I'd never go past just buying a brand that works well and look at it no further!

 

Large grain under this cheap hand scope (grayish picture above) at half the magnification of above looks like this - for scale, this is around 3/16" thick - the grain is enormous. Since I am heat treating by hand, I have to find the point where this occurs to be able to avoid it:

 

A couple of years ago, I had access to free XRF, but lost that when a friend of a friend retired. I'm assuming XRF could provide composition information that may explain the low hardenability of CrV3. Does the spectrometer do something significantly different than XRF?

 

[David Weaver]

On 9/8/2023 at 8:16 PM, Jerrod Miller said:

 Great sizes to pin grain boundaries a little, not so big as to do much else.  When carbides are that small they get ripped out of the matrix as the martensite is worn away around them before they can really be noticeable (my eye can't detect sub-micron scratches very easily).  

 

By the way, I appreciate the discussion and at first quick read I was surprised to see you mention a material with 3% chromium and only micron sized carbides....

 

...and then I realized that you're not talking about a 1% carbon steel where those would have something to fight for. 

 

A2 comes to mind with a little bit more chromium and sometimes seemingly dispersed large carbides. I stay away from them. 

 

As far as chisels go, I can see the dome of material around a worn blade as you can see above - down to what may be about 1 micron carbides. But on chisels, I have no way to create that visually because chisels just don't get the abrasive wear that I can create with a plane blade. If I see no carbides visually on a plane blade (which is about the case for magnacut and AEB-L), then that lets me know they're tiny. the other benefit of the tiny tiny carbides is you can inappropriately sharpen a blade without much consequence - as in, if magnacut has 1 micron carbides of whatever they are, vanadium or niobium, and you sharpen with alumina, it's hard to tell that there's much of a problem. if you sharpen 10V with alumina, the picture looks terrible - at high magnification, it looks like sand because there's a war that the carbides are sort of winning (they get broken out and leave a torn look, but they aren't cut neatly). 

 

With submicron diamonds, you can, of course, eliminate the ability to see any of them. 

 

Not sure if anyone wonders at what point you see grain enlargement and have a problem with woodworking tools, but the answer is immediately. The 1084 shown in the picture isn't usable for anything. It might slice vegetables or something, but in even something smooth like planing, bits of the edge will leave and leave ridges all over the work immediately. 

 

I haven't yet found a steel that can't be manipulated the way I'm working if it can be well hardened without bloating the grain. This 115crv3 bar is the first sample that I've used of anything that hardens so superficially if at all and then loses the ability to show a tempered hardness that makes sense (shallowness presumably causing that?). 

Edited September 21 by David Weaver

[Jerrod Miller]

3 hours ago, David Weaver said:

A couple of years ago, I had access to free XRF, but lost that when a friend of a friend retired. I'm assuming XRF could provide composition information that may explain the low hardenability of CrV3. Does the spectrometer do something significantly different than XRF?

Hand held (assuming that is what your friend had access to) XRF units are completely worthless for our needs.  They do not read lighter elements, like Si or Al and above; so no carbon.  Everything else that they do read are not overly accurate.  They are good for determining the difference between 41XX and mild, for example, in the scrap yard or machine shop.  Optical Emission Spectrometry (OES) gives much more accurate and precise readings for any element that the machine is set-up and calibrated for.  For example, in these alloys I would be able to tell you the carbon to the first decimal point for certain, but the second would have a bit of variance since we do not make these alloys and thus don't calibrate them.  With something like 1025, or 4330 that would move out one more decimal.  Other things like Mn, Si, Cr, Ni, V, and Mo would be pretty good at 2 decimal places, and P and S get out to 3.  

 

 

[David Weaver]

thanks for the explanation. We have typically the favor (or offer) of XRF to find out what completely unknown metals are - like when testing an imported (sold as "high speed steel" but no clue which) chisel or plane, or when Lee Valley introduced tools with the name of the steel veiled behind branding, it wasn't hard to figure out that it was almost certainly XHP. Which in the woodworking world should've been boasted about in the first place. 

 

As you say, we cannot get information on carbon - but there's usually enough in the XRF to get an idea of what the alloy is. 

 

Your mention of the light elements may help me figure out how to get analysis done somewhere later, though - I'd like to know what the carbon levels are in some of the tools made in the 1800s because they have a combination of hardness, edge stability but lack of visible carbides in a worn matrix that we don't really find now. 

[Alan Longmire]

1 hour ago, David Weaver said:

made in the 1800s

 

A lot of those are going to be cast steel, as in made from crucible steel and forged, not cast into shape.  This is going to be most similar to plain old W1 or 1095, but with wildly variable carbon from piece to piece.  Individual blades will be uniform, of course.  It's just clean straight carbon steel, low manganese, nothing else in there.  

[David Weaver]

I'd like to find out the actual case for the carbon - but also exactly what was in it to make it hardenable, though it probably does vary from one maker to the next. 

I've made a few things out of 1084, 1095, W1 an W2 and it's all not quite the same. I wonder how much of it is, as you say, the forging, and how much of it may be the heat treatment process, like with quench speed. 

 

I know early on, ore had a great deal of influence on the steel (french, swedish, etc), but don't know when that changed. 

 

What drives this is if I am using a taper plane iron from the late 1800s and some that I've made and some commercial, which are always a current variety of chrome vanadium or O1 (XHP and A2 are also used, but i don't generally use them), the 1800s irons are the last to nick if the wood is not agreeable. But they show no visible carbides in a wear pattern and often test 61-63 hardness. I get a pretty fruitful array of carbides from 1095, W1 and W1, and very little ones that are still only just visible in 1084, except if I forge the plane irons from a round bar, there is less carbide volume than if making them from bar. 

 

Do you know what the general answer is to when shops started controlling alloying? I would be surprised if the carbon in any of my irons (I have a lot) varies by more than 0.1%, and the first iron - age wise - that starts to show visible carbides is an early 1900s stanley iron when something like W1 was probably in use. 

 

it's possible I'll find out that I can't match ward and payne or some firm like that with these characteristics because they were just far better at it than I'll ever be!