Sunday, July 1, 2012

An Approach to Choosing Blade Steels, Part 1

One of the most common, if not the most common, emails I get is about choosing gear and in particular choosing a blade steel.  I have been pretty vocal about my favorite choice--ZDP-189--but if you watch gear reviews on YouTube or read just about any forum you will hear the same refrain over and over--steel doesn't matter all that much.  Nutnfancy regularly recommends blades with AUS8 steel.  Lots and lots of folks like VG-10.  Additionally, some of the more exotic steels, like Elmax or ZDP-189, come at a hefty premium.  This might lead you to wonder whether these upgrades are really worth it or necessary.  I think they are and I am going to explain why here.  Then I will cover, in brief and simple terms, metallurgy. 

Why Buy Better

I think high end steels are worth the extra money, but probably for a different reason that most steel junkies do.  I am not a gear collector, I try to be a gear user.  Additionally, I try to be very judicious with my choices.  After three years of trying to find "McGizmo" and "Sebenza" substitutes (and spending about $1000 in the process), I realized that it was actually CHEAPER to just save up and buy the thing I wanted instead of getting on a treadmill of constant minor upgrades.  In the three year before I bought the Sebenza I had spent hundreds of dollars on knives that were not QUITE what I was looking for.




Each time I would like the knife, but still want something a little better.  It was a slow and steady march costing at least $500 towards buying a $330 knife.  Obviously that was an irrational way to go about doing things.  The same thing happened with the flashlight I wanted.  I even took a disastrous trip into the land of Arc6, which is, perhaps, the worst piece of gear I have ever owned.  I wanted something that was like the McGizmo, but cheaper.  In reality, saving and buying the McGizmo would have been the cheapest thing to do.

This is all a long way of saying that even if the performance upgrade is small, there is a real premium is getting exactly what you want and getting the best.  It cuts off the purchasing path that is ALWAYS super expensive--the upgrade treadmill.  Should you buy the VG-10 Dragonfly II or wait and save for the ZDP-189 version?  I found I was happier waiting.

I also found that sharpening and chasing away rust is really not fun.  I have gotten better at sharpening, but it is just not something I look forward to doing.  The newer steels out there are really low maintenance.  H1 is virtually rust proof.  ZDP-189 holds an edge forever and a day.  I like to use my tools, not primp over them, so again, for me, the upgrade in steels is worth it.  VG-10 will get the job done, no doubt, but for a little more money and patience, I can get exactly what I want AND have less maintenance.

So, for me, the higher end steels are worth it.  In the long run, they saved me money and they do actually work better.

This leads to the next question, one that has no answer, but will lead to an approach I find handy in analyzing and researching steels--What is the best steel?

This is kind of like asking "What is the best medicine?"  Like medicine, steel is job specific.  There are hundreds and probably thousands of steels out there and finding the best is not possible.  Finding the one that works best for a specific application is possible though and hopefully this series of articles will explain how to find that steel.

A Brief Metallurgy Primer

Steel is nothing more than iron and other elements.  The type and amount of other elements that are added change the properties of the steel to emphasize one trait over another depending on the application.

For example, as odd as this seems for us knife knuts, there are steels, called weathering steels, that are DESIGNED to rust.  COR-TEN, for example, is designed for outdoor structural use.  In this role, even galvanizing (which is a weather resistant zinc based coating) is not fool proof.  A few years ago, someone thought about the rust problem on these massive outdoor structures and how that rust can weaken the steel and cause huge problems.  The solution to the rust problem--rust.  COR-TEN and other steels are treated so that the exterior of the steel rusts very quickly, but superficially.  This rust coating is allowed to stay on and actually serves as a fantastic protective barrier for the internal steel structure.  So long as the internal steel remains unrusted, the structure's integrity remains intact.  It was a clever idea and a perfect example of why there is no such thing as "the best steel."

I have done a significant amount of research into steels over the past month or two and I have come to the conclusion that knife knuts need to be familiar with metallurgy but not experts in it.  Do you really care where the sugar in your cake came from so long as it is safe and delicious?  Me neither.  Do I really care about the crystal structure in steel if it works really well?  Nope.   So I will run through a BRIEF metallurgy summary and then get to the approach itself, followed by a run down of my favorite steels and their applications.

As I said before, steel is an alloy (a combination of elements) of iron.  Iron is the element everything else in a steel recipe depends on.  When you look at a steel chart and see all of the constitutive elements, you might notice that they NEVER add up to 100%.  That is because ALL steels, by definition, consist mostly of iron plus other things.  Iron is the missing percent on the steel chart and it is always the most abundant element in steel.   The other elements included do a few things.  Iron is actually pretty soft, so some elements are added to make it harder.  Carbon is the most frequently used element, but newer more corrosion resistance steels like H1 and Elmax use Nitrogen to harden the steel.  Other elements are designed to improve corrosion resistance, like Chromium.  The more chromium, the more corrosion resistant the steel is, though this of course depends on the amount of carbon present as well.  Still other elements are included to improve the steel's workability and its hardenability.  Vanadium can make the steel easier to work with in its semi-molten state and elements like Niobium will allow a steel to be heat treated and hardened to a much higher degree during processing.

Steel is made in two primary ways--the traditional heat based method and powder metallurgy. 

In the traditional method, iron is heated until it is a liquid and other elements are added.  The mix is then cast and cooled.  It is usually formed into ingots, but can be formed into bar stock or rods.  Once the mix is cooled and cast it is sold and a knife maker cuts and grinds it, then reheats it.  More on that in the second part of this series.

In the second method, powder metallurgy, steel is made again by mixing iron and other elements, but this time instead of casting it, the steel maker takes care to make the combinations VERY pure on a small scale.  Instead of making big bars or ignots, the maker uses advanced methods and machines to make this mix into a powder.  The powder is then heated and placed under pressure.  The powder does not need to melt to make steel though as the pressure forces the powder to bond in a process called sintering.  Think of sintering like the process that ice cubes undergo in your glass.  They stick and bond together even though they don't actually melt into a liquid.  Their low melting point and the pressure caused by their weight is enough to bond them together even if they don't melt entirely.  Once sintered, the steel is then heated a bit and pressed into shapes with very high pressure machines.  It can also be heated and then mold injected like blow molded plastic (those fit to shape tool containers you have are blow molded plastic).

Powder metallurgy has quite a few advantages over the old method.  First, because the initial mixed steel is in powder form the structures and bonds of the elements within the powder can be more readily controlled and of a higher purity.  The more stable the structures and the higher the purity, the better the steel, at least for cutlery purposes.  Second, because the steel does not actually melt you can include elements that add performance that could not be added to steel using traditional melt and cast methods.  For example, tungsten, which adds hardness, can be included in powder steels much easier than melted steels.  The melting point of tungsten is incredibly high so the energy needed to melt it in a traditional steel is just amazing.  But with powder steels and sintering, tungsten can be added much easier.  Third, because of the precision machines that are used in powder steel, it can be batched out more easily by machines.  Then there is the injection steel process, which is interesting, but rarely used in cutlery (of course those steel junkies over at Spyderco, which generally has the widest range and highest quality steels of the major manufacturers, have used it in a few blades, like the Spyderco S).

My Rant about "Damascus" Steel

Here is a brief aside about Damascended steels, misleadingly called Damascus steels.  In short, true Damascus steel is exceedingly difficult to make because it requires materials that either do not exist any more (wootz) or a high tech lab.  The gift of true damascus steel was provided by a structure called carbon nanotubes.  In the middle ages they had no idea what carbon nanotubes were, but they knew that the steel made with wootz was very tough and still very hard (because of the carbon nanotubes).  Modern powder metal steels are better than middle ages damascus, but this is a pretty recent thing.  Additionally, some have theorized that those working on TRUE damascus steel can use the carbon nanotube structure and modern metallurgy methods to make even stronger steels than we have now, but this is something that is probably years away.

What knife collectors call damascus steel has none of the impressive properties of true damascus steel because it lacks the carbon nanotube structure.  What is called damascus steel nowadays is really modern steels mixed with different colored metals and then layered and folded to produce a pattern.  It does bear a passing resemblance to real damascus steel, but that's about it.  But thinking that it is designed for performance is incorrect.  It is designed for looks and that's it.  Saying that our current damascus steel is high performance because it looks like the middle age's damascus steel is like saying that your Hot Wheels is fast because it LOOKS like a Porsche.  And then there is the look.  I hated it.  I think it looks busy, messy, and ugly.  Plus the off colored metals in damascus steel tend to cause rust.  Finally it is insanely overpriced.  So let's see: 1) fraudulent name; 2) increased price; 3) ugly appearance; and 4) poor corrosion resistance; yep it is a waste.  SKIP MODERN DAMASCUS STEELS.

Next up I will detail a little but more about the relationship between elements and properties and then do a little primer on the Rockwell scale.  


  1. Awesome crash course. Look forward to the next installment.

  2. Great work Tony! I personally believe that steel DOES matter! The important thing to remember though is that the expensive steel is not always the best for the job. After all, even you would recommend ZDP - 189 for a heavy-duty outdoor work knife, cheap old AUS8 would work better there.
    Idaho Gunslinger

  3. This blog continues to be the most visited for me because of its perfectly balanced yet broad scope of content. This was a great post and one that helps put some knife terminology in context. Thanks!

  4. Yeah, it's all about knife size and role. AUS-8 on a larger, outdoor/tactical folder like the Ontario RAT-1 is great. Trading some hardness for toughness and field sharpenability is a good trade, as long as your steel can still take a good edge.

    But AUS-8 on a small EDC folder or gent's knife is a drag! There, I am ready to drink the high-Rockwell Kool-Aid. You want a hard steel with good edge retention for your small knife. You'll never chop with it, so toughness/chip resistance is less important. But you'll often use it to cut tough or fibrous materials (paper, cardboard, etc.) and since it's a small edge, you don't have as much "room" to spread the work and abrasion over. High edge retention is a huge convenience on a small EDC blade.

  5. Love this primer Anthony. I love the readability of it. My only add will probably be covered in your future posts. The type of steel is important. Also critical is how knives are sharpened. Most inexperienced home sharpeners don't properly manage their edge angles (using a simple marker on the edge can greatly assist with this) and they over polish them causing sharp knives that don't cut well. I do hope you consider the importance of good sharpening techniques as a key component to choosing steel.

  6. Tony, love this. I discovered your blog about 2 months ago, and have been very impressed. I just "joined" today. I want to thank you for the insight, passion, and good sense you put behind your commentary and reviews. I have learned a LOT. As a happy byproduct(or sad, depending on one's point of view), you are costing me a lot of money! I already had a small collection of kinves, and on your recommendation, I have recently purchased a Spyderco Dragonfly 2/ZDP-189 and today recieved my requested birthday gift, a Small Sebenza (O Rapture! O Bliss!), which will alternate with the Spyderco as my EDC knife. Even better (or worse), you've gotten me to dip my toe into the flashlight pool, and so my other present was an HDS EDC Executive 120.