Dumb Question about Stainless Steels

Happy Camper

Happy Camper

Joined
Jan 8, 2000
Messages
311
Ok, I know it's a stupid and probably tiresome question to many, but I am trying to get a relative scale of the most significant stainless steels applicable to knifemaking and how they relate to each other - A trade-off list, if you will.

I've been following threads here for quite some time, and I've used the search engine to try and find answers to my questions. I've even emailed a knowledgeable member with questions, but he never bothered to respond.

I'm not an idiot, and I'm not asking "what is the best stainless steel that does everything better than 1080," or that kind of thing. I know a strength in one aspect results only from a compromise in one or more others.

MY PREMISE:
Surely, out of the vast varieties of stainless steels available, there are a handful that stand out as being superior in at least one specific way, be it toughness, wear resistance, or such.

MY PURPOSE:
I am planning on moving up from my main staple of production knives to custom knives and since I have my choice in steel, I would like to make a halfway intelligent decision based upon what I plan to ask my particular knife of choice to do.

I have a primitive list of steels based upon what I've followed here over the years, and the areas of overlap outweigh the areas of disagreement. However, most threads seem to quickly loose content due to bickering and my list is extremely incomplete.

Replies would be most welcome, or if you prefer you can email me.

Thank you

====edit=============
The member I had emailed responded to my questions and in tremendous detail
 
I'd like to throw out some impressions, based on what I've read and personal experience, and see what our resident experts have to say in comparing them, if that's okay:

1.) Best "edge holding" in terms of wear resistance -- CPM S90V

2.) "Toughest" in terms of impact/shock/torque resistance -- CPM S30V, based on early testing.

3.) "Strongest" in terms of which remains most durable while taking on the most efficient cutting geometry--thinnest edge/most acute bevel angle--my impression of the best in this class is still S90V, but I don't know what S30V might be capable of in the higher Rc hardness ranges.

4.) If we added a category for most stain/corrosion/rust resistance, without precipitous loss in edge holding or toughness, I'd include the cobalt-based Haynes alloys. Of these, Stellite 6K seems to be the most useful for knife blades in terms of strength and edge holding.

So...

S90V for absolute best edge holding/wear resistance;

S30V if you need something tougher for higher impact and/or torque resistance, and still retaining high edge holding;

Stellite 6K if you need it absolutely corrosion proof, with best edge holding for this category.

A couple of further thoughts: My impression of a "tough" blade material boils down to meaning that the edge is resistant to breaking, cracking, or chipping, and will finally fail by "rolling" or indenting, rather than cracking or chipping out. My impression of a "strong" blade material is the other side of that coin--the material is resistant to deformation by denting, bending, or "rolling", and will finally tend to crack or chip rather than bending, rolling or denting. In a given steel, the toughness/strength balance is usually adjustable through the heat treating process, depending on the uses for which the blade is designed.

Hope this is in line with starting the discussion you anticipated.

Thanks.

-w
 
Thoughtful post, Happy, and I think Will has given you a good answer. You obviously understand that what you require a knife to do has a lot to do with the steel you select. Here are some of my thoughts, keeping to steels I have some experience with:

Listed in basically worst-to-best (personal preference order):

I don't like 440C. A lot of people say "It's a fine steel." But there are many better choices out there; why go with a good steel when you can get a great one? The only time I would go with 440C would be with a user meant for salt-water, or with a display piece.

Similar to 440C, but I like it better, is Sandvik 12C27 (I think that's the number). It doesn't hold an edge quite as well as 440C, but it seems to take a better edge, and is at least as corrosion resistant.

I don't like ATS-34. Why? In my experience, it is not very stainless and I have trouble getting a really good edge on it.

I like 154CM better; this may be because of its superior quality, though it is basically similar in makeup to ATS-34. I find it doesn't rust as readily, and I can put a "sharper" edge on it.

CPM440V: This is the only one of the stainless CPM steels I have personal experience with. I think it is pretty much a direct improvement on ATS-34 in every respect, except perhaps toughness.

VG-10, I feel, is one of the "uber-stainless" steels. It takes a hair-popping edge, is relatively tough, and is quite stain-resistant.

I don't have a whole lot of experience with BG-42, but the little I have is positive in terms of toughness, sharpness, and stain resistance. It is used in Sebenzas, and you can bet this was a decision that was carefully considered.

In the realm of semi-stainless, I like D2 and D2M a lot. I feel they are hardly (if any) less corrosion-resistant than ATS-34, while taking and holding a better edge. I haven't done destructive testing with either of these steels, so I don't have firsthand experience, but I believe D2 is a tougher steel.

All of these work best when properly utilized. Heat treat can make or break (literally) a blade. I hate Benchmade's ATS-34, but Strider's works well for me. The difference? I think it is Paul Bos's heat treat. All my old Benchmades and my Strider do tend to rust easily for a "stainless steel." Much easier than my D2 Blackwood LiteWave, or my D2M Ralph Mad Max.
 
I have also accumulated impressions from what I consider to be reliable sources concerning edge holding on some of the more popular "high end" steels, and would enjoy hearing any contrasting or corroborating opinions:

ATS34/154CM - Baseline

BG42 - 6% to 10% improvement in edge holding over ATS34 (Robert Loveless in a Blade Magazine article a couple years ago)

S30V - 15-25% over BG42 (from a well-connected knifemaker who has been working with S30V since February of this year, but declines to be quoted publicly. Can't imagine why! :))

S90V - up to 50% over BG42 (Phil Wilson, qualifying that statement by saying that relative wear resistance is highly dependent on heat treat and Rc hardness -- actually, that should go without saying in any such discussion, come to think of it)

Also, Deloro Stellite, in their product literature, cites Kelloggs cereal company as having experienced a 90% increase in blade life going from 440C to Stellite 6K for their scraper blades (blades used to scrape cereal flakes from a drum). I don't know how that might translate to knife edge geometry.

-w
 
Thanks folks! This is EXACTLY the type of discussion I was looking for! I hadn't gotten to it yet, but I'm glad D2 and other "semi stainless" steels were mentioned, for I wondered if as a general rule the less stainless the better the performance.

I previously had minimal correspondence with two custom knifemakers, but I didn't really pose the in depth stainless question to them. I could have chosen a knife maker and gone with their selection of steel, but that's what I've already been forced to do with production knives so I wanted to weigh the differences and make the decision myself this time. -Not that I wouldn't respect their opinion if they told me I was off my rocker for the choice of steel I come up with! LOL Experience does weigh a whole lot more than book knowledge, so I suppose in the end my final decision will weigh upon the knife maker anyway.

But how I do love the learning!
 
Will York :

I have also accumulated impressions from what I consider to be reliable sources concerning edge holding on some of the more popular "high end" steels ...
Click to expand...

Will, in the above does 10% better edge holding mean that you can cut 10% more material before getting the same level of blunting? Or that after cutting the same amount of material that one blade is 10% sharper than the other? These two statements are very different. As well, what materials were used as blunting stock? Blunting takes place by corrosion, deformation, wear, impaction and fracture, to which degree these factors influences edge retention is very different for different materials.

For example, while cutting hemp rope blunting happens by nearly 100% deformation, and thus is strongly determined by hardness as that is the primary factor in strength which controls the resistance to deformation. However, performance ratios based on these cutting tests do not in any way hold for different materials as they will be influenced by a different weighting of the above properties. In short, I don't think "ZZ% better edge retention" is a meaningful statement, and yes, I realize that I have said similar things in the past. However after reducing piles of rope, cardboard, and wood to bits, as well as wire, rubber tubing, carpet and many others, I have come to the conclusion that edge retention is a very vast subject indeed and blade performance can vary all over the place depending on what you cut and just as importantly how.

As another example, I have used several 1095 blades at 58-60 Rc and they work very well in chopping. The edge lasts a long time, and resharpens quickly as little material has been worn or fractured away. This is due to the high toughness and ductility even at the high hardness and the fact that wood is not abrasive. The edge resists indendation and excessive deformation, and the burr formed will not fracture even under repeated impacts. It will also cut rope and whittle wood for a very long time for the same reasons. Pump 1095 up to 63-65 RC and this aspect of edge retention goes up significantly, which is why Japan woodworking tools are in this range. However compare the same blade to a alloy tool steel on a very abrasive material and the 1095 one falls out almost right away because of the very low wear resistance. So does 1095 have good edge retention or not? I think the question has to be a lot more specific? I think you can easily answer for example "Does ZZZ have good edge retention for a camp bowie", but the answer to this is not the same as "Does ZZZ have good edge retention for a fillet blade" even though in both cases you are asking about the edge retention of steel ZZZ.

For example, take a S90V and S30V blade at the same RC (62/63), the edge retention should test nearly identical on hemp rope showing equal Class I edge retention which takes place by deformation and thus is strongly dependent on hardness. However on a very gritty material S90 will have a clear advantage as this is Class II edge retention which takes place by abrasion and thus is strongly dependent on wear resistance. Yet on chopping class work S30V will have a clear advantage as this is Class III edge retention and requires a high impact toughness and ductility to prevent fracture (it also needs a high hardness to prevent excessive deformation). Thus which has better edge retention - both and neither. It would be interesting to run S90V at 59 Rc and S30V at say 62/63 Rc and see how the performance runs over the above three broad classes as compared to the both at 62/63 Rc.

-Cliff
 
Originally posted by Cliff Stamp
Will, in the above does 10% better edge holding mean that you can cut 10% more material before getting the same level of blunting? Or that after cutting the same amount of material that one blade is 10% sharper than the other.
Click to expand...

Cliff--

I don't know what Bob Loveless meant by 6-10% better edge holding, but my impression of that general statement is that you can go through 6-10% more material with the same level of blunting. Same for the impression on S30V over BG42, which was based on cutting corrugated cardboard, I believe. In the case of the S90V rating, you know Phil Wilson's rope-cutting tests as well as anyone.

From your recent work, it's clear that different kinds of subject materials and different types of cutting require different combinations of properties in a blade. The class system you use above is a good way to index blades for specific use, and I appreciate your comparative analysis on the S90V and S30V in each class.

There were two reasons why I threw out the above percentages. The first reason was that the people who formed those opinions seem to me to be people who are serious and knowledgeable about assessing blade steels. And secondly, as I said, I was hoping contrasting or clarifying opinions/experience might surface. Are there any other "stainless" category blade materials you would rank above the ones I mentioned, in any area of performance?

Anyone?

-Will
 
I hadn't gotten to it yet, but I'm glad D2 and other "semi stainless" steels were mentioned, for I wondered if as a general rule the less stainless the better the performance.
Click to expand...

I don't think that a less stainless steel is necessarily a poorer performer. D2 (my current favorite) will outperform the less-stainless 1095 in a wide variety of edge-retention situations (not sure about chopping; would probably depend on hardness), in addition to being closer to stainless. But in a steel optimized for corrosion resistance, other qualities will generally suffer. Just as a steel meant to work well with low-stress edge holding probably wouldn't make a great sharpened pry-bar.

Cliff brings up an important point: there is no "best" steel, just better ones, and what they are better at depends on what you plan to do with them.

If you don't mind my asking, Happy, was there a reason you wanted to confine your search to only stainless steels? I personally obtain better results from non-stainless steels, and with the advent of "Generation II" coatings like boron carbide that combine corrosion and extreme wear resistance, I think there is really no functional disadvantage to high-carbon or tool-steels, except in environments so corrosive as to rapidly degrade the edge (salt-water diving, for example). If this is too off-topic, feel free to contact me via email, otherwise I'd like to hear your reasoning here.
 
Will :

Deloro Stellite, in their product literature, cites Kelloggs cereal company as having experienced a 90% increase in blade life going from 440C to Stellite 6K for their scraper blades (blades used to scrape cereal flakes from a drum). I don't know how that might translate to knife edge geometry.
Click to expand...

Scraper blades are lifetime dependent on wear, because the edges have very high cross sections and the manner in which they are used, they don't need to be concerned about deformation and thus the low RC and strength of the material is not a critical concern as you will see is performance based pretty much 100% on wear resistance. However edge holding in general for knife blades is not as nearly dependent on wear resistance, unless of course you are willing to run your edges really blunt and are doing a lot of scraping and heavy cutting in very gritty materials.

Are there any other "stainless" category blade materials you would rank above the ones I mentioned, in any area of performance?
Click to expand...

BG-42 can be run at 63/64 RC and in that range will stand along side CPM-S90V at 62/63 RC in Class I edge retention but should fall behind it rapidly in Class II, and to a lesser extent in Class III, which type of work neither will handle well anyway.

For pure Class III work, S30V stands out. I would be interested however in comparing it to S90V at a lower hardness (to get the necessary toughness), and see how much Class I performance was lost by the hardness drop, and how much Class III performance was gained, Class II ratings should not significantly changed.

In general AISI 420HC is probably the baseline for tough use stainless as it has a very high toughness and ductility for a stainless steel. I would be curious if S30V was greater actually, it shouldn't if it was a normal steel, but the CPM process produces inherently tougher and more ductile steels. The problem with such steels like AISI 420HC is that you give up a lot of Class I edge retention to do well in Class III, S30V should handle both very well.

Happy Camper :

if as a general rule the less stainless the better the performance.
Click to expand...

Yes, in all areas outside of corrosion resistance. The critical factor being all-else-equal which makes the answer somewhat complicated. For example a high alloy stainless like ATS-34 has better Class I and Class II edge retention than 1095 as Burke noted, however it falls behind a high alloy non-stainless steel like M2 in those same classes. As well, the non-stainless steels will be tougher and more ductile at the same hardness levels, which in general means that you can use them rougher, grind them thinner, or run them harder - or a combination of all three.

-Cliff
 
Ulp!... pretty high falluting discussion goin' on here, and I wouldn't disagree with anything stated. The best performing stainless steel I have encountered (and my experience is limited -- I don't have any BG-42 or ATS-34 blades, just AUS8, SAK blades and one VG-10) has to be VG-10. My Fallkniven F1 takes and holdss a terrific edge and seems to cut better than any other stainless blade I've tried. Don't know of any custom makers using it, though.
 
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