The Complete Guide to Knife and Tool Steels
Over the course of this blog, we’ve looked a lot of knives and everything around them, such as locking functions, blade shapes, sheaths and so on. However, this post has taken a little longer due to the sheer enormity of the subject.
Steel is arguably the most important aspect of a knife. The metal is what cuts and slices, without it or without good quality your knife will quickly blunt and become unusable.
For the purposes of this article we will break down exactly what steel is. We will then look at terms ‘jargon’ you’ll often see associated with steels. Then we will look at some of the most popular and general types of blade steel, this will be followed with some comparison graphs to show the ratings of each steel. Finally then we will round off this post looking at more specialised steels such as Damascus, and the CPM process.
There is an awful lot of really useful information to get through here so lets, get this show on the road . . .
What is Steel?
“Steel is an alloy of iron and carbon containing less than 2% carbon and 1% manganese and small amounts of silicon, phosphorus, sulphur and oxygen” (https://www.worldsteel.org/faq/about-steel.html). There is a common misconception that steel is a singular thing. Well simply it’s not. There are thousands of different steel types, many of which have been invented or developed this side of the millennium making for continually strong and lighter metals.
Does steel rust?
Yes it can. If you leave it exposed to water, oxygen and even dirt, the steel will start to become covered in an iron oxide coating. There are ways of delaying and preventing this though. Stainless steel is one example; although this can still rust it takes a lot longer due to the inclusion of Chromium. Other methods of reducing rust are blade coatings, these prevent oxygen from coming into contact with the blade and causing a reaction which sees the formation of rust.
Five Key Terms
When looking at a blade you’ll see some or all of these terms mentioned. These five terms are the fundamental characteristics you will want to look for in your blade steel:
Some people know this as blade strength but hardness is the primary term. It essentially means that the harder the steel the less likely it is to deform/bend when stressed during use. It is generally measured using the Rockwell C scale (aka “HRC”).
Toughness is the steels ability to resist damage like cracks or chips when being used in heavy duty applications. This also defines the steel’s ability to flex without breaking. Therefore, this is very different to hardness, and in all likelihood (not always though) increased toughness means decreased hardness. However, whereas hardness has a standardized measurement there isn’t really one for toughness so it’s much harder to measure.
Wear resistance is the steel’s ability to withstand damage from both abrasive (scratches and scrapes) and adhesive wear (rubbing of the blade upon a surface). Abrasive wear comes from softer surfaces coming in contact with rougher ones. This leads to scratches and other scrapes forming on the blade. Adhesive wear occurs when debris is dislodged from one surface and attaches to the other. Wear resistance generally correlates with the steel’s hardness but is also heavily influenced by the specific chemistry of the steel. In steels of equal hardness, the steel with larger carbides (wear resistant particles) will typically resist wear better.
Corrosion resistance is the ability to resist corrosion, such as rust. We’ve already briefly mentioned some of the primary culprits of corrosion, but there are more. Therefore, you should look after your knife and clean it properly (luckily there is a post for that). Unfortunately though most of the time increased corrosion resistance means decreased edge retention and quality.
Edge Retention represents how long the blade will retain its sharpness while it is being used. Edge is really important to knife performance, but unfortunately much like ‘toughness’ it’s extremely hard to measure. This inaccuracy means every one disagrees as to what edge retention means, and how you decided whether it’s good or bad. The longer an edge resists being changed (deformed) the better you could say the edge retention is.
Which is best?
You tell us? People have so many preferences on what they want their knife to be able to do. Unfortunately there is no magic steel that is amazing at all five. Therefore, you have to make a decision about which is most important to you, whether is corrosion resistance or edge retention. Most people seem to struggle with the difference in hardness and toughness as some steels which are extremely hard can be easily chipped and visa versa. All steels even stainless will oxidise if left out in the air and in water, so always take that into consideration!
Popular Steel Types
Now some of you may complain your favourite steel may not be included below, but we’ve tried to include as many different types as possible. As a general rule we are going to start with the most premium and high end steels, then work our way down to the cheaper and ‘lower quality’ steels. We are determining this list based on the steel cost, but really there is no exact science to quality Vs quantity so bear with us. You’ll get the idea.
If you want top of the line Edge Retention and Wear Resistance then you want one of these ultra premium steels!
The CPM S90V Steel is a very high Carbon steel as you’d expect. The main reason that it is as good as it is though is due to the high quantity of Vanadium present in the steel. However, the downside is that the price is very, very steep. Some knives that include this steel are the Benchmade Osbourne 940 and the Spyderco Wilson South Fork Fixed Blade.
The Bohler M390 ‘Microclean’ is one new steels we mentioned at the start which are fast becoming stronger and lighter all the time. The combination of alloys makes for a steel that has exceptional wear resistance, high hardness as well as being very corrosion resistant. The process for making this knife is third generation powder metal technologies, allowing for the blending of chromium, molybdenum, vanadium and tungsten, which all adds to create this super alloy. The Benchmade Barrage Mini 586 and the Linder M390 Karelia Hunter are both examples of knives which use this steel.
For a ‘super steel’ ZDP-189 is a material that won’t necessarily break the bank. Two popular brands that use it are William Henry and Spyderco. This steel like M390 contains huge quantities of carbon and chromium that result in extreme hardness. ZDP-189 averages around 64 HRC but some knife makers are able to achieve upwards of 66 HRC. Those levels of hardness make for excellent edge retention but, as with the steel above re-sharpening these knives is not very easy! The reason this falls slightly behind the two seen so far is that it hasn’t got the same levels of corrosion resistance unfortunately, but still a phenomenal blade steel.
Another ultra premium steel from the guys at Bohler-Uddeholm is the Elmax SuperClean which is a high chromium-vanadium-molybdenum alloyed powdered steel with extremely high wear and corrosion resistance. Although Elmax is a stainless steel, you get superb edge holding and relatively easy sharpening while maintaining a good level of corrosion resistance. A very good all round steel! There are some really great knives using this steel such as the Spyderco Lion Spy and the Lion Steel TiSpine.
This is a pretty uncommon type of steel at the moment, but we only see it becoming more popular. CTS-XHP is a relatively new steel from US based company Carpenter which has very good edge retention and Rockwell hardness rating of 61 HRC. Like some of the other ultra premium steels we’ve looked at, this is also a powder based metal. It has a slightly better edge retention than S30V, but in order to re-sharpen the blade, more effort is needed. The final good point about CTS-XHP is that it has a reasonable corrosion resistance. The Cold Steel Code 4 Spear Point is one of knives that use this metal.
CPM M4 is one of Crucible’s top tool steels. Like every other steel made by Crucible, it was created using their patented Particle Metallurgy Process. What does this mean? Essentially it creates a very stable and workable metal which make it much easier to tool. The ‘M’ in M4 stands for Molybdenum. This gives the steel great wear resistance and high toughness. However, it does have low levels of chromium; therefore, it’s considered a carbon steel and will require regular care. On a final note though, it does also have a high hardness rating of about 62 HRC. Probably one of the most popular knives with this steel is the Spyderco Bradley Folder.
This steel is an upgrade from the S30V version we talk about in a bit. This steel entered the marketing 2009 as part of a collaboration between Crucible and Knife maker Chris Reeve. This steel has incredible toughness, edge retention and corrosion resistance, which was achieved by using a very fine grain structure and adding small quantities of niobium. Maserin and Kizer are two knife brands that like to use this steel in their products.
This steel is often simply referred to as S30V, and has excellent edge retention and resists rust effortlessly. Although the S35VN is an improvement on this steel, take absolutely nothing away from the qualities that this steel possesses. For the price you get a whole lot of steel. It has a brilliant balance of edge retention, hardness and toughness. That’s probably why you see companies like Spyderco constantly bringing out new models with this steel, including the Paramilitary II.
High End Steels
As well as in knives, this steel is very popular in high end multi-tools. It’s a hard steel, and has very good toughness coupled with a good corrosion resistance and good edge retention. Because of its hardness some people will find this steel reasonably difficult to sharpen, but it’s not impossible. We often see Benchmade coming out with lots of knives using this steel, so you know that it’s going to be very good quality!
This is a Japanese steel, and it’s very good! Many people see it as the Japanese version on 154CM (which is American) and in general represents a high quality steel which has become very popular with knife makers. ATS-34 has many of the same qualities as 154CM, but it does have a slightly lower corrosion resistance. We see lots of custom knife makers using this steel.
D2 is probably one of the first really common steels we have looked at so far. Because of its low chromium % it’s technically not a stainless steel, however, it’s not so low to be classed as a carbon steel. Therefore it’s often referred to as ‘semi-stainless’. D2 is a very hard steel and has very good edge retention, but it doesn’t have a high toughness, this means it’s very hard to sharpen, and takes a lot of time and practice to master. Loads of different knife and tool companies’ use this steel and for good reason.
This is another steel you’ll see highly championed by the likes of Spyderco. This is a very similar steel to both ATS-34 and 154CM. The main difference though is that it contains vanadium The VG-10 steel is very similar to 154CM and ATS-34 with slightly more chromium but also contains vanadium which notably increases the strength of the blade steel. Like ATS-34 this is a Japanese steel which has really started gaining popularity across the world. The only downside is that it can get brittle.
H1 steel comes from Japan’s Myodo Metals and has to be one of the worlds most corrosion resistant metals! Unfortunately because of the way alloys work to have such good corrosion resistance you lose out on edge retention, however due to the inclusion of nitrogen in the make-up of H1 steel edge retention isn’t that poor. Therefore, realistically this knife is perfect for divers and people who need a knife for use in water. The final thing to note is that due to the specialist nature of this steel it’s usually at a premium price. Fallkniven make some very good knives with this steel!
The Bohler N690 is a widely popular blade steel, made by a massive range of companies. It’s a very good steel and you can find some very nice knives with this steel at a reasonable price. It has a HRC rating of 60, making it one of the harder steels in this band, yet it still also retains good corrosion resistance due to the levels of chromium in its composition.
N680 steel contains about 0.20% nitrogen and over 17% chromium making it extremely corrosion resistant. A bit like the H1 steel this is ideal for people who will likely use their knife in water a lot. Benchmade have made a few good diving knives with this steel. However, unlike H1 it has a better edge retention and it’s also cheaper, therefore more accessible for most people.
Upper Mid Range
This is a carbon steel with a high carbon % (0.95) but has a lower level of manganese. This means that this steel in particular has good wear resistance, and holds and edge very well and easily re-sharpened. But, it has low toughness. Something to note is that the corrosion resistance of this knife isn’t particularly high; therefore, you’ll probably notice it’s usually coated in order to help prevent rusting.
This is probably one of the most popular types of stainless steel used in pocket knives. It’s not too expensive and generally a very good all-rounder type of blade. It’s reasonably tough and wear resistant but it really excels at stain resistance. It also has high levels of carbon and chromium, and can be easily sharpened.
AUS-8 steel is Japanese-made steel, and like the 440C is highly resistant to rust and corrosion. AUS-8 has a relatively low level of carbon so unfortunately it doesn’t hold its edge particularly well, but that being said it’s really easy to sharpen.
This is a vacuum-melted stainless steel from US based company Carpenter. In this bracket of steel, you’ll find that CTS-BD1 is very good at holding its edge. Some people therefore see it as slightly better than AUS-8 and 8Cr13MoV. This steel also has high levels of chromium allowing it to achieve better corrosion resistance. Due to it being a fine grain steel with small carbides, it will hold an edge pretty well.
This steel is very much comparable to AUS-8 but containing slightly higher carbon content, which makes it slightly less corrosion resistant, but retains a good edge. Like 440C this is an extremely popular blade steel and for good reason. Kershaw, Spyderco and Schrade are among some of the popular users of this steel..
The 14C28N stainless steel from Swedish manufacturer Sandvik is considered an upgrade to their 13C26 steel (described below). 14C28N steel is as a result of a more corrosion resistant version of the 13C26 steel. You’ll find slightly more chromium and less carbon in the 14C28N but the real secret is the addition of Nitrogen which promotes corrosion resistance. Overall it’s a very impressive mid-range steel that can be made very sharp, and the reduction is carbon does mean re-sharpening is also easier.
Lower Mid Range
There are a few different steels in the 420 range. The HC is this title stands for High Carbon. The reason for this is that increased carbon means increased hardness. Although generally not the best steel, certain manufacturing processes where they use quality heat treatments result in better edge retention and corrosion resistance. There are some really nice knives and tools out there from companies like Buck and Leatherman.
This 440A steel is not a million miles from the 420HC version we’ve just looked at, but it does have some important differences: It has lower levels of Chromium (great for edge retention and wear resistance). However, that means it loses some of its corrosion resistance properties.
This is another steel from Sandvik, which was originally developed for razor blades. It has a similar composition to 440A steel, with a higher carbon to chromium ratio making it generally a little harder and wearable, but at a cost of less corrosion resistance. Really though, there isn’t a whole lot of difference between them.
420 & 420J
The 420 steel is on the lower end of the quality spectrum but still perfectly fine for general use applications. It’s low carbon content (usually under 0.5%) steel which makes for a softer blade and as a result will tend to lose its edge quicker than most other steels. The benefits you get from this steel are the flexibility of the metal and the stain resistance, but it is not particularly resistant to wear and tear. Knives made from this type of steel are generally low priced, mass produced items.
This is the Japanese version of the 420 steel range. It has a very similar make-up to the 420 series with a very low carbon %. It’s a low priced and mass produced item. Not a bad steel, but there are much better ones if you have the money.
Knife Steel Performance Charts
Here are some rankings for edge retention, Rockwell hardness, wear resistance and corrosion resistance.
More Metal Knowledge
What exactly is a CPM Steel?
CPM stands for Crucible Particle Metallurgy which is a process for manufacturing high quality tool steels by Crucible Industries (American manufacturer). They are the sole producer of CPM steels which are formed by pouring the molten metal through a small nozzle where high pressure gas bursts the liquid stream into a spray of tiny droplets. These droplets are cooled, solidified into a powder form and then ‘Hot Isostatically Pressed’ (HIP) where the powder is bonded and compacted. The trick here is that the HIP process ensures each of the fine particles have a uniform composition without any alloy segregation. All of this results in a steel that has improved toughness, wear resistance and can be ground and heat treated with maximum effect.
What is powder metallurgy?
Well you can probably guess from the name that it involves powdered metals. These are created by mixing elemental or alloy powders and compacting the mixture in a die. The resultant shapes are then heated or “sintered” in a controlled atmosphere furnace to bond the particles metallurgically. The high precision forming capability of powder metallurgy generates components with near net shape, intricate features and good dimensional precision pieces are often finished without the need of machining.
This modern process enables manufacturers to make products that are more consistent and predictable in their behaviour across a wide range of applications. In addition the powder metallurgy has a high degree of flexibility allowing the tailoring of the physical characteristics of a product to suit your specific property and performance requirements. This means that different levels and combinations of elements can now be made to make better and better steels.
What does ‘laminated steel’ mean?
Laminated steel is a term you’ll often hear associated with knife blades. In basic terms it’s a metal made of different types of steel (in layers) rather than a single sheet of metal. The reason this is done is to get the benefits of other types of steel, without compromising the make-up of the main steel. As an example the Fallkniven F1 is one of the most popular knives with a laminated blade. It has a laminated VG10 blade. The reason for this is that it increases the toughness of the blade and can increase strength by as much as 25%. This makes the knife much better for hard-use tasks.
What about Damascus steel?
Damascus steel originates from the Middle East (now manufactured globally). It also isn’t a new steel, it’s one that’s been used for thousands of years. It’s distinctive and recognisable swirling marks rubbing through the metal. This is due to the welding of two different steels together. These days you only really find it on top of the range lines mostly due to its aesthetic appeal over any actually qualities the steel possesses. Because of its cost it has become a big favourite of knife collectors.
Stainless or Carbon Steel?
It depends. Higher carbon generally means lower corrosion resistance. If you are likely to be using your blade in humid, damp, wet or rainy environments then consider stainless. If you are a fair weather user, who like to get some heavy duty work done with the knife then carbon is where you should look.
On a final note: To qualify as a true stainless steel there must be at least 14% chromium.
This article has simplified the maze of knife steels somewhat, but don’t assume that because it’s high end instead of mid-range that it is better. Different manufacturing and treating processes even on the same steels give different outcomes.
Also as important as blade steel is, it isn’t the be all and end all. If you don’t like the handle or the shape or any other part of the knife then blade steel becomes less of a big deal. Hopefully though, you now have a much better idea of what each type of steel actually does and what sort of benefits and drawbacks each one has.
Citation: This article is based upon an original article from Best Pocket Knife Today, available here.