Comparing 26c3 to 125cr1

[David Weaver]

This is sort of an offshoot of the thread about the toughness of W1, and then some following things I've seen (just how uniform some 52100 rod is and how not some others is - does it make much difference in a chisel? I'll have to figure that out when I get a chance to really use one with unsightly snapped samples and one with really clean and uniform stuff. Unsightly as in bright spots that look like undispersed alloying, not large grain). 

 

So, I've had great luck with 26c3 chisels. I can't beat them with anything else, but I can't get 26c3 thicker than 0.25" either, can't get it in rounds, and that limits the tang thickness on chisels to less than I'd like. Even if using flat stock and forging on a bolster, I have to decide if I'm going to get better at smithing so that I can bunch up the material at the tang to something more like 0.35" square from 0.25" bar, or just use thicker bar. 

 

125cr1 comes in a thicker bar. it's cheaper, too, but the cost difference isn't meaningful to me. I was hoping it would look as good in snapped samples of 26c3, but it doesn't. I have no evidence yet that it matters, but have observed better performance in something else (O1) when the sample is clean and neat. there is less small nicking in samples that look better - it's correlation at this point, not a conclusive statement that visually better samples make practically better tools. 

----------------

 

this is 125cr1 at about 40-50x optical. The actual material thickness is about 0.18"

 

For comparison, here is what 26c3 looks like at around 40-50x magnification (the little hand scope that I use is dishonestly rated, so their claims of magnification don't pan out - thus guessing). This is just a single quench - at one point, I would always single quench material without pushing the temperature very high to make sure that I could better it or at least not make it work with cycles. Now, I just cycle everything. the black stuff is just dirt. on the bottom. in the upper part of the sample, it may be in the steel itself. 

 

 

The same piece thermally cycled then and broken again. 

 

 

if I had access to unlimited charpy testing, I'd see if it makes a difference. I need to cycle the grain now after post forging normalization,anyway. 

 

Back to the 125cr1 - the splotches. what are they?

 

at higher magnification, they look like this. 

 

Some are bigger than others, but they look more like "painted" sand rather than solid bits in the steel. 

 

This is very similar to the difference I've seen in one 52100 sample vs. another. 

 

hardness of both is about the same 68-69 in parks 50 in thinner cross sections and 69 or 70 in brine with less variance if cross sections are as thick as these. 

 

if the edge of chisels made of both show the same amount of defects after some given uses, then I will care less. if 125cr1 roundly spanks W1 in harder woods like 26c3 does, then same thing. 

 

 

Edited October 13 by David Weaver

[David Weaver]

Sorry I don't have better pictures. i have a few scopes (one legitimate, and then a couple of the hand held types that are $15 or so). None is both high clarity at high magnification plus significant depth of field. 

 

The better (indian metallurgical scope, the kind you get off of ebay for $450) can take very good pictures, but the field or depth of focal length is very shallow. I'm guessing it's intended to view flat samples, and it's very good at that, just not taking an expanse of rough torn surface. 

 

I can get pictures of the individual bright areas under the better scope, though, if it's helpful. 

 

As a rank amateur, I'm assuming these are just alloying elements that weren't well dissolved. There's not much in 125cr1, and I'm guessing it's not the manganese as this hardened just fine through and through and snapped (untempered) like glass. Or put differently, if I had to bet at lloyds, I'd say chromium. I'll show to of 52100 in a separate post. 

 

[David Weaver]

Jantz round 52100 (after forging - picture looks the same with a sliver sawn off of the round rod without forging and just heat treated quickly)

 

 

same steel after forging, but lower magnification (don't have one at the same magnification). 

 

And a round bar of who-knows-what-52100 from ebay. I'm sure it's just someone cutting rods into short lengths. I went searching for others - didn't get to mcmaster yet - when seeing the splotches in the jantz round bar. 

 

 

This is clean stuff, though. Buderus flat stock from NJSB looks like this second clean sample, too. 

 

So far, round stock has a lower "clean snapped sample" rate than flat stock. 125cr1 is above is only the third sample of flat stock that I've seen (out of about 25? or 30?) that shows something other than uniformity. 

..edit..I found a picture of the buderus. 

 

I have the last picture because I was excited at the time to have finally gotten 52100 to high hardness out of the quench (68 here, but I've seen 69 out of brine quenched 52100 from the same bar)....without bloating the grain that is. 

 

I have some work to do to see if there are any spotted difference in use. I like the jantz-stock finished chisels just fine. they're high hardness and I see very little indication of fault at the edge so far. 

 

So, I think this lack of dispersion, if that's what it is, doesn't really have much effect on woodworking tools and probably wouldn't on knives. 

and a previously shown picture from the indian metallurgical scope at high magnification. 

 

This, too, is from the jantz material with the bright marks. I'm fairly sure I posted this elsewhere on here, but it does show a good clearer view of the bright spot. 

[Jerrod Miller]

1 hour ago, David Weaver said:

I'm assuming these are just alloying elements that weren't well dissolved.

Nope.  This is just light reflecting back into the lens off the shiny parts that just so happen to have a bunch of small areas clos together at the same (or close enough to it) angle to all reflect together.  

[David Weaver]

so more a geometry/orientation of breaking thing?

 

here is a picture of 1095 at the edge of a plane iron, though the splotches in this steel were more solid looking. 

 

 

In order to get a picture like this, though, I have to make a plane iron, and then use it in a plane with a chipbreaker, which rubs the wood in a "scoop" shape and wears the edge the way it's shown here. I would estimate the wear shown here is only several thousandths of an inch. In this case, the shiny part also wore at a different rate than the rest of the steel. It's slightly further out at the edge and marked work. This bar stock was from AKS, and thus (unless something changed), the company making it isn't known. 

 

I never got a similar picture of this on the better scope - it doesn't just look like the others where it looks like "painted" grains, but rather like filled. 

 

I'm not sure it's just a geometric break pattern on the rods, though - anything is possible, but it's not variable. As in, if I snap more stock from the jantz rod, it will show the same thing every time. If I snap starrett O1, it will never show that. 

 

here's an example where I think the reflection is shearing or something at edges - apologies for the wordy picture. I put these three together just to send to a few people who were involved with brainstorming when I first started doing low temperature cycles. None of them heat treat, but one of them had read verhoeven for leisure just because he was interested in steel in general in tools and knives. The broken buderus sample in the middle shows those marks only at the edges of breaks, though. I'ts otherwise uniform. We were curious about the hock O1 irons (these are common in woodworking) because they look like they're either laser cut or blanked or something, and they are dirt cheap for anything made in the western world given their quality (wholesale for something like $25 per and retail for about $40). 

I suppose I could test my theory by viewing the bright splotch samples at an angle, but can say from the metallurgical pictures, the reflections do not change position when going from one scope to the next. The cheap scope pictures are never actually straight on, so the metallurgical scope and the cheap scopes are viewing at different angles. 

[Jerrod Miller]

I was just referring to these sections:  

 

Not this type of splotches:  

 

39 minutes ago, David Weaver said:

so more a geometry/orientation of breaking thing?

Exactly.  

 

It sounds to me like you desperately need to start polishing (and preferably etching) your samples and looking at them on the metallurgical microscope to learn what you are wanting to learn.  Those are only intended to be used with polished samples anyway.  

[David Weaver]

yes, I'm being lazy and still haven't purchased nital. Let's assume this is not a carbide but undissolved elements, presuming that's possible, would that show up on a polished sample? I'm aware that you can highlight carbides and show grain boundaries. I'm sort of at a halt with this one because visually, there's not enough there to really know what this is for sure. Other than to mention that the bars are like vegas. 

 

As in, if these things appear in one bar, they stay in that bar, so to speak, and I don't see it seemingly at random from one bar to the next. But if it's as you say, it's possible that one of the bars breaks in a different way than the others. 

 

Because chisels fail with very small chipping (if they're good enough to gradually show only small defects after heavy use), it's not really possible either to say "aha, there's a defect that occurs at a bright smudge". More, do I see any higher defect rate at same hardness. 

 

Regardless of what it is, the chisel test is the critical test. If nothing is affected at the edge in heavy use, then this is just a curiosity. The bright spot on the 1095 plane iron is something I didn't know was there. I saw a strange dull line on wood where I expected just an uninterrupted bright surface. the dull line sent me looking for nicking in the iron and instead, I found that long bright spot. Actually, I should say I expected a deflection. Nicking leaves a very characteristic little ridge that you can typically feel with a fingernail. 

 

 

[Jerrod Miller]

10 minutes ago, David Weaver said:

Let's assume this is not a carbide but undissolved elements, presuming that's possible, would that show up on a polished sample?

That is a bad assumption, because it doesn't work like that.  If something doesn't melt into the bath when making steel, it stays looking like a rock.  When we add elements to steel, it looks like this: 

Ferromanganese  

https://en.wikipedia.org/wiki/Ferromanganese#/media/File:Ferromanganèse_métal.jpg

 

Ferrochromium

https://en.wikipedia.org/wiki/Ferrochrome#/media/File:Ferrochrome.JPG

 

If that doesn't melt down, you will have a very bad and obvious inclusion, not a little shiny section.  Anyone making anywhere near decent steel (and even placing making quite bad steel) will not have this happen.  The entire bath is generally taken a few hundred degrees above melting point, and it is often held at hot enough temperatures while chemistries are verified and such that this just doesn't happen.  

 

What may happen is alloy segregation, where alloying elements are not evenly distributed in a sample.  This can be caused by segregation during solidification, or from things like dissolving carbides (either primary carbides from solidification, or those present in powder metallurgy) and not giving sufficient time and temp to even out via diffusion.    The elements are still dissolved in that they are part of the matrix.  They just aren't evenly dispersed.  

 

Polishing alone isn't likely to tell you what you want to know.  Etching is needed.  

[David Weaver]

>>the elements are still dissolved in that they are part of the matrix.  They just aren't evenly dispersed.  <<

 

This is what I'm trying to convey. I am working by observation and not education, so I didn't know how to describe it. A slither of chromium going through the steel in a "droplet" does seem unlikely, which is why I used the word "assume". I'm also assuming that if there was chromium like that, it would find a buddy either chemically or through dispersion and even if not uniformly distributed, mate with that buddy. 

 

Or to put it differently, I think the spot in the plane iron was poorly dispersed (undissolved isn't the right word, but that's what I used above I think - the stuff dissolves, but doesn't diffuse evenly into the matrix). 

 

So even if that were the case and visually something like this would occur, I have no reason at this point to believe it's going to be as drastic as the much more blatant smudge on the plane iron. Even that one doesn't result in voids, it just spoils a plane iron's ability to do even work. The iron is usable, but not for a demanding user wanting smooth with the iron and not sand or something later. 

 

What I'm leaning toward other than for 125cr1 is using steel that looks the best in the snapped samples, though. Not because I have a reason to do it, but because I don't have a reason not to. 

 

Testing chisels in actual use is easy, though, and I'll know the answer to this soon enough. And hopefully in the not too distant future, have some snapped samples of white #1. 

 

I have seen these smudges only in steels with chromium added, but not in all with chromium, obviously. 

[David Weaver]

going back to the picture of the plane iron, even though I think the composition of the steel outside of the carbides is different there, the carbides showing up as tadpoles (a round carbide leaves sort of a comet pattern as it protects the matrix behind it) don't look much different. In the 1095 in that case, the blotches show up in large bold spots like that seemingly at random. 

 

I could hammer 52100 here into a plane iron or hammer out some of the 125cr1 into a plane iron and do this, but I'm not sure if I want to go to that much effort yet. It's not that hard, but it would waste about an hour just to see if those spots would show up in a wear bevel. And 1.25% carbon isn't a steel that would have widespread appeal in a plane iron because this and 26c3 will have pretty much no abrasion resistance beyond any other plain steel. 

Thanks for the responses, by the way.