Let's Talk About Steel

[rawcustom]

Before I begin I'll give a brief background of myself. I've been a knifemaker practically all of my life, and have had the opportunity to work with and talk with some of the bigger names over the years. I have made knives, tested knives, sharpened knives, read about knives, and done enough studies and research in metallurgy that I should have probably declared that as my major back in college. That being said I find plenty of misconceptions strewn about for the average consumer who is looking to purchase a knife. Some ideas, right or wrong, are held onto tight and I realize some people can get worked up to hear something contrary to their held ideas. So if you can't read a view contrary to your own without getting upset, than please don't proceed reading. Just consider that I've done my homework and have born out theory through experience for some time on this. 

Since this topic could go on for an extreme length I will limit this particular discussion to one of my favorite misconstrued topics: Stainless vs High Carbon steel

To start with, the term “stainless” only defines chromium content in steel, with a steel containing 13-14% or more chromium being considered “stainless”. By this same criteria we have everything with less chromium considered “non-stainless”.

The term “high-carbon” references a steel that has 0.3% or more carbon content. Realize that most any suitable high-carbon knife steel will be at least 0.8% carbon. So you can use “high-carbon” steel that is in fact totally unsuited for knife making, a great example is the HC stamped RR spike.

So a steel can be high-carbon stainless, or high-carbon non-stainless, or low-carbon stainless, or low-carbon non-stainless. The most important fact is that by these labels alone you cannot determine a knife’s performance.

Think of it this way, the ingredients in the steel is sort of like putting in your ingredients for some breakfast muffins. The purity of your ingredients, the ratio of your ingredient, and your consistency in always adding the same amount each time are all critical to your end result. However, your ingredients are what I call the potential, not the realization. The next step is how the ingredients are mixed, and lastly how they are cooked. Steel is very similar that the mixing and forming of the alloy is crucial to the grain and performance, and the heat treat (cooking) must be exact to complete the realization of the added ingredients and mixing. So a steel with all the right ingredients means little if it were processed crudely and/or heat treated incorrectly. Conversely a steel with substandard ingredients mixed exacting and heat treated correctly will outperform a steel that had better ingredients (potential) but failed on realization.

So why all the trash talk on “stainless” you may ask? I think this traces back to the fact that many, many cheap knives are using substandard stainless steel, not a knife grade steel. They also put little investment into the heat treatment and may be dealing with a foundry that runs very loose specs on its formulation, and is likely using older mixing and casting methods. So they essentially start with poor ingredients, put little effort into mixing, and are trying to flash cook them or may skip that step entirely. They still can label it “stainless” and the uneducated consumer thinks stainless = knife steel. Stainless knife grade steels require a very drawn-out, multi-step heat treatment, that must be exacting for success. 

So why all the hype over “high-carbon” you may ask? Well for starters most people marketing high-carbon are dealing with simple steels. Remember steel is only iron + carbon. More alloys can be added of course, but that is all it takes to be a steel, and is commonly called a simple steel. High carbon simple steel is much cheaper than it’s stainless or alloyed counterpart. It also can be produced as decent quality with less technology than an alloyed/stainless steel. Lastly, it has a much simplified and easy heat treatment process compared to stainless. So with limited ingredients, they mix with less effort, and the cooking process is more like a toaster, very simple and fool proof.

In short, the high-carbon simple steels are much easier to achieve realization from than a high-carbon stainless steel, or a high-carbon high-alloyed steel. This is why you will find more simple steel knives that are effective even at low price points than you will with stainless or alloyed knives. However, they are no match in performance in any respect to a properly alloyed or stainless high-carbon knife steel with an appropriate heat treat. They can be out-performed in edge retention, toughness, corrosion resistance, you name it, except price.

Anyway I hope this is useful for those wishing to learn more. I could go on and on and on, so if the response is positive maybe I will continue with my second favorite myth out there.  

[Art]

I can get on board with a lot of it, but I draw the line at the often used term "knife steel".  There ain't no such animal: unless you allow any steel someone made a knife out of to reside in this "category".  So many things are made of steel, that steel with out some definitive designation is just steel.  Even if you go with only steels above the eutectic (say about .77C), only a very small percentage is used for knives.  Any reasonable tool steel at close to the eutectic or above can make a darned respectable knife, if properly treated.  The other consideration when selecting a steel is what the purpose of the knife will be.  An knapped obsidian knife may possibly be one of the sharpest knives obtainable, but is kind of worthless if you want to chop or pry on something.  Osborne has been using the same 1065 or so for as long as I can remember, and their knives are really first class (for the price and availability).  I've seen a boat load of these (and own more than a few) that all act and react pretty much the same.  Knives that can obtain at least HRc 55 or so will make a good knife although I like them a little harder.  Every steel used for a knife is going to be a tradeoff, no one steel is good enough, cheap enough, and easy enough to work (including heat treatment), to make it an "industry standard" and become a or the "knife steel".

Art

[bikermutt07]

I'm interested in learning more. Ramble on, please.

[rawcustom]

You are right Art "knife steel" is not an official term, much like "sniper rifle" doesn't imply anything other than a rifle a sniper has used. In my use of it I am referring to a steel intended for knife use that is generally a high carbon (0.7%+) that has a few extra alloys, the most common is chromium, but often include molybdenum, vanadium, tungsten, etc. You are also correct that application has a lot to do with choice of steel selection, it also has a lot to with HRc settings as much as the chosen steel itself. Depending on the knife I could use the same alloy at 58rc or 62rc. Some alloys can handle higher HRc better than others. Some have to have HRc considered with edge geometry to work, but alas the position of this post is to educate people beyond stainless and high-carbon advertising common to the craft. 

So to avoid confusion I'm not inventing a knife steel by using the term, I'm just using it to better classify steels that are appropriate for knife making since the terms stainless and high-carbon have very little reflection on a steel suitability for knifemaking. 

 

Also you're proving my point with the Osborne 1065 steel. It's a simple steel that cheap and easy to work with and get a good heat treat. This means consistency, adequate performance, and lower cost. 

Edited June 2, 2016 by rawcustom
addition

[Martyn]

3 hours ago, rawcustom said:

...This is why you will find more simple steel knives that are effective even at low price points than you will with stainless or alloyed knives. However, they are no match in performance in any respect to a properly alloyed or stainless high-carbon knife steel with an appropriate heat treat. They can be out-performed in edge retention, toughness, corrosion resistance, you name it....

I would disagree with the toughness part. You're right, kniofe steels are not steels specifically used for knives - with the possible exception of some of the crucible formulas. Generally, steel is steel and whatever formula is used as appropriate for the application. It's not just cost that makes carbon steel a better choice for structural applications, it's tougher. Adding chrome to make steel stain reduced, is primarily cosmetic (except perhaps for divers knives and domestic cutlery/food prep). That cosmetic benefit comes at a price and everything after that, vanadium or whatever, is about trying to buy back some toughness, which you never quite get.

I would also argue that extended edge retention isnt necessarily a benefit. It's a function of wear resistance and increased wear resistance also means harder to sharpen. If your plan is to never sharpen your tool, then high wear resistance is a benefit. But if you like your edges as keen as possible, then it's just extra work. If stainless always out-performs carbon, ask yourself why we never see it in stress-critical structural applications, mission critical springs etc and why the very best carpenters tools are always carbon steel?

Edited June 2, 2016 by Martyn

[rawcustom]

7 minutes ago, Martyn said:

I would disagree with the toughness part.

I think you are confusing strength for toughness. But again you would be wrong. Toughness as in impact strength can be greatly increased with alloy elements beyond iron and carbon, strength as well. Chromium is just one of many alloys, that can be added to a steel. 

Edge retention is sharpening resistance. I guess you could argue the point of a good knife sharpens quick/ dulls quick, and that we'll just have to disagree. Well carbon steel doesn't really specify anything. Remember I quoted simple carbon steel which is just iron and carbon. Price point and tradition are strong followings. Many can assume a steel works "good enough" for it's intended purpose that they don't feel a need to upgrade. They have been making carpenter tools for the last few thousand years. Modern high alloy powder metallurgy steels haven't been on the scene more than about the last 50. Also Chromium is more than cosmetic, and corrosion resistance is an important attribute to many applications of steel. And check the components of stress critical, again they aren't simple carbon, and again I wasn't commenting on strength, as that implies structural properties more common to bridges than knives. 

[Martyn]

2 minutes ago, rawcustom said:

I think you are confusing strength for toughness.

I don't think so. Strength is about a materials ability to resist force, toughness is impact resistance, but crucially also about how far a metal can deform without fracturing.

 

5 minutes ago, rawcustom said:

I guess you could argue the point of a good knife sharpens quick/ dulls quick

I didn't say that. But I would argue that for a knife to be a good knife, you do need to be able to work the metal with reasonable ease. The fact is, the better the edge retention, the harder the knife is to maintain - it's directly proportionate. I do like stainless BTW, I've several folders in s30v, my first was a Sebenza about 12 years ago. But there it is, stainless is great for folders. Knives that have moving parts that you dont want to rust, knives that get carried in salty, sweaty pockets and used for all sorts of applications, by people who generally cant be bothered to sharpen them or maintain them (that incudes me). But fixed blade knives are easier to maintain, they have no moving parts and the typically larger size, means they are often used in higher impact and bend/stress activities, which makes carbon a more suitable choice. Similarly, precision tools are only precise if they are razor sharp all of the time. Given that is your mission, why would you pick a steel that is harder to sharpen? A chisel made from s30v would be horrible.

[rawcustom]

 

15 minutes ago, Martyn said:

means they are often used in higher impact and bend/stress activities, which makes carbon a more suitable choice

Long held beliefs.

You are arguing for "carbon" steel being better at impact and stress than an alloyed steel. Please list which "carbon" steel this is.

I would also like to know which "carbon" critical structure steel is you are referring to that has higher strength and toughness?

[Martyn]

4 minutes ago, rawcustom said:

 

Long held beliefs.

You are arguing for "carbon" steel being better at impact and stress than an alloyed steel. Please list which "carbon" steel this is.

I would also like to know which "carbon" critical structure steel is you are referring to that has higher strength and toughness?

Proper heat treatment being a given,  I would argue that 1080 is tougher than anything with more than 12% chrome.

[Art]

I hate to say it, but hype and marketing has more to do with steel used in a knife than suitability of purpose.  Especially knives made by production knifemakers, or should we call them knife manufacturers.  The whole idea of a custom knife is CUSTOM.  Benchmade knives very seldom see a bench.  This pretty much goes for any maker/manufacturer making over 500 total knives a year.  The only reason I offer a count so high is that some guys (and gals I guess) can average 2 knives a day.  But really, anyone who has their blanks profiled by CNC machinery the likes of a water jet, is not a real custom maker.  If the maker takes a piece of steel, marks a profile on it (with custom design for user features or desires), and takes it over to the Burr-King or Bader and grinds away everything that doesn't look like a knife, they are a Custom Maker.  Manufacturers look for different steels to set them apart from other manufacturers and to attain the marketing hype of using a steel that is used by a particular custom maker.  While the steels used by manufacturers tend to vary over a short period of time, a custom maker might be using a steel he has been using since the '80s or '90s (I'm old).  I don't have any problems with custom knives made of 440C or 1085, or O-1, or D-2, or BG-42, or ATS-34, or 154CM (the old stuff).  Those same steels from a manufacturer....meh.  You should want to know where your food comes from and generally how it was handled; the same goes for the steel in your knife.

Art