which is the toughest stainless?

[Cliff Stamp]

Isn't 420 the toughest?

It will resist fracture very well, and bend a lot before cracking, however in large chopping knives you need a combination of strength and toughness. If the hardness and strength isn't there then the edge will just deform and or roll. The problem with stainless is that it is difficult to get both of these high at the same time, it is easily done with tool steels.

If you are just chopping wood, then this really isn't that stressful with a knife because knives in general are not that heavy or long and thus the impact stresses are *really* low in general compared to axes or parangs. I have spent hours with ATS-34 blades chopping woods, even the hardest types (dead wood limbing) with no effect.

The real issues comes when you cut through the wood and mash into something hard, the more brittle steels can then suffer massive cracks while the tougher steels will just dent and can take less damage and as well be easier to restore. In general though it is best to look past stainless, but if you have to pick one, get a low carbon/alloy content with a fine grain structure, not 440C/ATS-34/S30V.

-Cliff

 

[Nick Hyle]

I believe Gail Bradley used S30V for his "chopper" at the Guild show last year, and was quite competitive.

sal

I'm guessing Mr Bradley knows a thing or two about edge geometry that helped a bit.

But there are certainly makers who've shown that S30V CAN make a first rate big knife. My gut feel is that there is knowledge involved on the fine scale about working S30V that has not fully circulated through the community yet - ie some makers apparently are delivering S30V blades of whatever size with no chipping problems - many others are not. Heat treat, edge grinding, surface prep, voodoo, I don't know - but there seems to be something.

But that's just my impression.

 

[Nick Hyle]

In general though it is best to look past stainless, but if you have to pick one, get a low carbon/alloy content with a fine grain structure, not 440C/ATS-34/S30V.

So we're talking about something like the medium carbon stainless Sandviks? 12C27, 13C26?

 

[ghost squire]

use 1095

Errr... thats an odd choice for toughest isn't it? Compared to the other 10xx steels 1095 generally has the least ductility.

 

[HoB]

Well, there has been quite some progress with the heat treat of 1095 apparently. It may not be as tough as some other carbon steels, but treated right, it should be many times tougher than any stainless steel around. But you are right 5160, L6 and S7 should be tougher when heat treated accordingly.

Staying strictly with the original question, I would place my bet on 420J, but that is to me a pretty useless bladesteel. As actual choice I would pick S30V or laminated VG10 and would make sure the former is heat treated right. If necessary, I would remove the blade and sent it off to a specialist and have it heat treated. According to the specs, S30V has a pretty high toughness as far as stainless steel goes. But then again, I would simply not choose a stainless for a blade that needs maximum toughness.

 

[Cliff Stamp]

So we're talking about something like the medium carbon stainless Sandviks? 12C27, 13C26?

Yes, that is pretty much what I was thinking on, they should offer a decent toughness at a high hardness.

-Cliff

 

[flyingphonix]

I think he might mean which one would stand up best to heavy duty tasks like chopping, prying, etc (he said "big knife" and mentioned a camping knife). If that's what he means, I'd also be very interested in seeing which steel comes out on top.

if it is that mean,i suggest an ax\saw ...choose different tools,not just dirrerent knives.let the knife do the knife's job,i dont think there is a steel on top.

 

[M Wadel]

sandvik 12c27 only has .6%C and 13.5%Cr so will that make it tougher that 440c? http://www.smt.sandvik.com/sandvik/0140/internet/APPLICATIONS/SE03502.NSF/61daa3aae3283d03c12569ab004f4aaf/59fef9b00c2c86c1c1256b9600397772/$FILE/S-3820-ENG%2001.qxd.pdf

i see you can temper it at 500 or around 1000F go get the same hardness, will the 1000F temper make a tougher steel? edit: sorry disegard that just read that those high temps will make it brittle (above 840)

 

[M Wadel]

what ive learned today.. been reading alot about steel now and ive come to the conclusion that some of the toughest stainless suitable for knives (or atleast they will be good for this, tough and stainless) are Marss500/12c27M, 12c27, AEB-L/13c26 in that order. supposedly the carbides in these steels are K2 carbides that are much harder than the K1 found in 154cm/440c etc. they are not powdersteels but very fine. the carbide size (or was it grainsize) is around 0,8micron (AEB-L) "powdersteel" around 2-3micron and 440C 50micron. i think 13c26/AEB-L and 12c27 is what im getting, theyre not that expensive either the AEB-L is around 9,50€/kg

 

[Cliff Stamp]

Generally you lose impact toughness at the higher tempers due to carbide precipitation, you also lose corrosion resistance as well. However there can still be benefits and some knives will benefit from steels hardened in that manner, it depends on what you are trying to achieve. However for a big chopper type knife you would generally avoid secondary hardening. AEB-L and other similar stainless look to have excellent potential, unfortunately though they are all being unhardened which is why many people rank them similar to 440A as "dive knife" steels.

-Cliff

 

[Redguy]

Are there any significant difference between the toughness of higher carbon stainless steels? Is VG10 or 440C for example really tougher or less tough than S30V or 154CM at their usual hardness?

 

[M Wadel]

IIRC the higher the steel is alloyed the more brittle it gets. i think its some boundary at around ,7-,8C where toughness goes downhill (for plain carbon steel) but it gets harder. it probably depends on what the steel is alloyed with, some elements/combination of elements/different proportions of elements will make the steel tough. also powder steel will be tougher ive read. V and Nb vill make a finer grained steel so i suppose a tiny bit will promote toughness. i think the vg10 is the toughest of those it has a tiny bit of V (much less than s30v and bg42) in it 154cm has none. there is more carbon in s30v and bg42 and about the same as 154cm, 440c has atleast twice the Si and Mn as the others. dont know how the Mo is affecting the toughness here. hope this is accurate

 

[HoB]

Well, really the problem in comparing stainless to non-stainless steels is that you don't really know where the carbon is, by looking at the composition. In non-stainless steels. There are only 1 or 2 carbide formers so the carbon content gives you some idea of the properties of the martensite. In a highly alloyed steel, the carbon could be tied up in god knows what carbides. So the hardening can be a result of carbide precipitation or martensite conversion which in turn will influence the properties and of course the different types of carbides and the carbide size will also play a role. So while in low alloy steels the rule of thumb (less carbon -> increased toughness) is pretty good, it doesn't seem to really hold in those highly alloyed steels.

 

[M Wadel]

yeah you could very well be right. does anybody know how large the different carbides in steel are?

 

[HARDMETAL]

in wood industry,usually, use t1(18% w) ,m2(4to 5 % w),d2,as plannr knife for hard wood.if only consider the tough t1 is the best .d2 seriously not classified stainless steel ,but as high content of cr,it is stainless.
i think s30v is good , but the same as some members opinion ,fallkniven , lam vg10 is a choice for reasonable price.
420j is very soft, for camping knives .those china made knives made of similar steels .

 

[Cliff Stamp]

The size of carbides depends on how they are formed, the largest carbides are the primary ones formed during the initial steel cooling, few blades have these remaining as they are usually broken up by forging/heat treating, Boye's dendretic steels are the exception. The largest carbides normally seen in steels are the ones found in D2 which can be as large as 50 microns, the ones that form in secondary hardening in high speed steels are nanometers in size (1000 nanometers in a micron). Cementite, which is iron carbide, is a micron or less in size at its finest. As you temper to higher temperatures, cementite will coarsen and get larger. Many of the alloy carbides will aggregate together, moly and chromium will combine in carbides for example. There is also the grain size of the steel which is different from the size of the carbides. The steel when it transforms from one structure to another does so in bits, called grains, and the boundries of these grains are weak spots for fracture because carbides can sheet there and impurities can gather as well.

-Cliff