Not Just Tough

H

Hans Asmussen

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Nov 19, 2012
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Is there a list of steels that are harder than 5160 at at least the same toughness? I assume that both are properly heat treated.

(And please direct me to the proper forum, if this is the wrong one).
 
Are you meaning something that can be ran hard, but still be tough? Off the top of my head for tough steels...M2, M4, 3V, Z Wear.
 
I mean it literally. Hardness and toughness are well defined physical qualities, and 5160 is known to be pretty tough. I am looking for steels that have at least the same toughness, but are harder (Rockwell). I will check the ones you mentioned anyway.
 
You'll probably get a lot more feedback, but please remember that hardness and toughness are both functions of how the knife was manufactured, particularly the heat treating.
I'm going to go out on a limb and say that for a particular steel hardness and toughness are inversely related, which is to say that for two otherwise identical knives, the harder one will probably be less tough. In this context hardness is the ability to resist deformation and toughness is the ability to resist fracturing.
That said, some steels can be safely hardened more than others, and some steels are tougher than others. Ibute21's list is a pretty good starting place for steels that remain fairly tough even when run hard, at say HRC 60+.
 
I am not an expert but ibute21's question was correct. Hardness is mostly a product of heat treat, not intrinsic in the makeup of the steel. That being said, I think the choices he mentioned have a good reputation for toughness at high hardness.
 
I have already assumed that the steels are properly heat treated. And fairly tough is not enough. So, if it helps you assume the toughness of a correctly heat treated 5160 at 55 HRC and other steels at 60 HRC or more. The steel at 60 HRC or more should have at least the toughness of 5160 at 55 HRC. Are there such steels?
 
What are you looking to make that requires that much toughness and hardness?

Hans Asmussen said:
The steel at 60 HRC or more should have at least the toughness of 5160 at 55 HRC. Are there such steels?
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The short answer is, I doubt it. I've been wrong before, though.

It's a tough (no pun intended) question. The difference between 55 and 60Rc is pretty huge. Demanding the same or better impact toughness at a much higher hardness is going to be quite a challenge. I suspect you may be trying to drink whiskey from a bottle of wine.

Published data reports CPM-3V with a C-notch charpy test value of 85 ft-lbs at 58Rc, and 70 ft-lbs at 60Rc. That's pretty dang tough.

The same info on S-7 indicates 85 ft-lbs at it's maximum hardness of 59Rc, and a whopping 125 ft-lbs at 57Rc... that's crazy-tough, and still pretty hard.

I haven't used S7. I've heard of some folks who make swords and stuff with it; hopefully one of them will chime in. I cannot find any charpy tests figures for 5160 - which seems odd, it's a very well-known steel - so I can't really say how either 3V or S7 compares to it. I do know that 3v with appropriate geometry at 58 or even 60Rc will take about as much pounding as any sane human can dish out in anything resembling normal use.
 
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bld522 said:
Err . . . umm . . . INFI maybe? ;)
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This.

Some good steels already mentioned.

Also, basically look at what competition choppers are using on their competition knives. Those steels tend to be at the top end of hardness, and toughness, it seems to me.
 
You ahould specify your desired hardness range. 55 is pretty low for any cutlery, and 5160 can reach 65 as quenched, so there is 10 points of hardness to consider for tempering range.
 
I too cannot find any impact toughness values for 5160 at 55 Rc.
However, 5160 is very close in composition to L6. L6 at 57 Rc reaches ~90 J impact toughness. S7 reaches ~165 J at 57 Rc, CPM-3V reaches ~113 J at 58 Rc, and INFI supposedly reaches ~150 J at 60 Rc. 5160 is tough steel, no doubt, esp. at only 55 Rc., but at that level it won't keep a straight edge long and at higher hardness it is well surpassed.
 
Hans Asmussen said:
World domination. I am German, after all.

Do not read too much in my question, it is informative. Having said that, I found several answers helpful already, including yours.
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Fair enough, and thank you. It's certainly thought-provoking.

Bigfattyt said:
Also, basically look at what competition choppers are using on their competition knives. Those steels tend to be at the top end of hardness, and toughness, it seems to me.
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Interestingly, pure toughness doesn't seem to rank as highly among comp cutters as we might think. It seems that most winning competitors are using CPM-M4 for its edge-retention. M4 is not nearly on a level with 3V or 5160 in terms of toughness - but in that application it seems like the high carbide levels are what makes it shine (seems counter-intuitive, but there it is). These folks are winning with speed and accuracy, and demand really thin, hard, wear-resistant edges. Remember, they have to do stuff like cut and split drinking straws as well as cleave 2x4's. Pretty specialized and fascinating work.

That's largely why I asked what Hans was interested in designing/building. As always, steel selection will come after proper geometry for an intended use.

Incidentally, the only reason I didn't mention INFI earlier is that you can't just buy a bar and experiment with it. Surely it has a place in the conversation if you want to go with an existing knife.
 
james terrio said:
Fair enough, and thank you. It's certainly thought-provoking.


Interestingly, pure toughness doesn't seem to rank as highly among comp cutters as we might think. It seems that most winning competitors are using CPM-M4 for its edge-retention. M4 is not nearly on a level with 3V or 5160 in terms of toughness - but in that application it seems like the high carbide levels are what makes it shine (seems counter-intuitive, but there it is). These folks are winning with speed and accuracy, and demand really thin, hard, wear-resistant edges. Remember, they have to do stuff like cut and split drinking straws as well as cleave 2x4's. Pretty specialized and fascinating work.

That's largely why I asked what Hans was interested in designing/building. As always, steel selection will come after proper geometry for an intended use.

Incidentally, the only reason I didn't mention INFI earlier is that you can't just buy a bar and experiment with it. Surely it has a place in the conversation if you want to go with an existing knife.
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I agree, that the comp choppers have a focus biased toward edge retention, and resistance to deformation at thin angles and grinds. The two are not necessarily the same consideration either. Those choppers, true competition choppers, are not built for prying or lateral stress or side loads. Thick spines, but really thin edges. Just thick enough not to fail. But there does seem to be some toughness in the steels at such high hardness and thin edges, to not be blowing edges out.

For "normal" use, those same steels with a couple points dropped in RC, and a bit more material behind the edge should prove great ever day choppers. Just like competition axes, I would not get one as my beater, to baton through knots or pry or anything.


I would like to see Busse re release more high hardness infi. The original Battle Mistresses were run a few points higher on the RC scale, and performed excellent. (I had a thin higher hardness small Busse, the BAD that did very well).

I have owned 3 of their large choppers, and a double handful of the medium and small knives.They are tough thick or thin. You give up some in edge retention though.

There is a list of steels I would like to try in similar application, but my funds have a limit!

I am also not a steel snob. Give me a well heat treated chopper in 10xx or some tool steel, and I will be just fine too.


The S7 that Scrapyard uses in their line (they call it SR77) has shown to be remarkably tough as well. I would probably put it above the Infi in the same dimensions. I think you give up some edge retention (though not a lot from reports), and much more on corrosion resistance.
 
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Bigfattyt said:
I agree, that the comp choppers have a focus biased toward edge retention, and resistance to deformation at thin angles and grinds. The two are not necessarily the same consideration either. Those choppers, true competition choppers, are not built for prying or lateral stress or side loads. Thick spines, but really thin edges. Just thick enough not to fail.
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Yes, that's exactly how it's been explained to me. :thumbup:

Bigfattyt said:
But there does seem to be some toughness in the steels at such high hardness and thin edges, to not be blowing edges out.
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Pretty interesting stuff, indeed. Now, for a less-specialized knife that will likely be used in less-than-ideal conditions (and for more than a couple minutes at a time), I'd trade off some of that wear-resistance for greater toughness any day. I have a remarkable talent for poorly-executed glancing blows, and finding the knots/grit etc in anything I chop :D
 
chiral.grolim said:
I too cannot find any impact toughness values for 5160 at 55 Rc.
However, 5160 is very close in composition to L6. L6 at 57 Rc reaches ~90 J impact toughness. S7 reaches ~165 J at 57 Rc, CPM-3V reaches ~113 J at 58 Rc, and INFI supposedly reaches ~150 J at 60 Rc. 5160 is tough steel, no doubt, esp. at only 55 Rc., but at that level it won't keep a straight edge long and at higher hardness it is well surpassed.
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where do you get that "INFI supposedly reaches ~150 J at 60 Rc"?
 
L6 is close to 5160 and it's used in some very high-end swords over a yard long, not to mention 5160 itself is used in some of the best production axes in the world, run in the low 50's-RC. That's pretty good recommendation for the stuff as some of the toughest cutlery steel around that is still moderately priced.

I have to say though, that in my experience, a "correct" HT doesn't exist any more than a "correct" knife, though either may be true for a very specific task. In any knife, the HT used is designed to balance toughness and hardness according to the maker or customer's experience and opinion. D2 at max hardness (~64-66RC?) may chip more easily than D2 at 58-60RC, so that trade is made by most production companies. However, custom makers may run D2 a couple of points in either direction depending on the particular design and intended use. 5160 ran at max hardness won't hold a candle to 1095 ran near 50RC, though the latter may only be suitable for a butter knife.

That being said, CPM 3V is the obvious answer for a more common knife steel that maintains great toughness at high (~60RC) hardness. 52100 or Swamprat's SR-101 may be a good choice in straight carbon, as it to is very similar in composition to 5160. However, it may give up a bit of toughness for better wear resistance. Plain carbon also brings up 1084 down to 1050, which are tougher the lower you go down. Note, however; I don't know at what point in any they outstrip 5160. I've never really seen the lower carbon steels in use on knives, only on swords and axes. Lastly, some makers may use some steels that are more generally only seen as industrial steels. S-7 for example has about 3x the toughness as L6 or 5160 at 58RC, though it's just over half as wear resistant. A greater trade off is made with H-13, another tool steel, though it's usually run under 50RC with wear resistance half again that of S-7, making it impractical for knives.

In short, for anything shorter than 10 inches 3V seems to be the best widely available balance of 5160+ toughness and high wear resistance (around that of S30V and D2) in my opinion, along with INFI if you're considering a Busse.
 
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