M390 Steel Review

Everything You Need to Know About M390 Steel

Are you confused over finding the best knife for you? M390 steel is one of the most hardened new steels on the market – and it might be just what you need to find your perfect cutting partner. Read on to find out all about M390 steel, and just what makes it that extra little bit special to us here at BladeOps.

A Brief Overview of M390 Steel

Where traditional steels rely on ingot casting methods to shape, the manufacturers at Bohler-Uddenholm developed a technique that ensures an excellent spreading of carbides. They call this the powder metallurgical process, and it goes some way to explaining exactly why M390 steel is so different. M390 was first developed as a more hardened, stronger, more wear-resistant metal that could be used in the development of tools that undergo high-stress. What we have found is that it makes a sturdy, hardened knife that is not quick to lose its edge.

Bohler themselves maintain that there are many benefits to using this type of steel. Some of these are as follows:

M390 steel is durable, more so than many other types of metal.

It performs very well when ground.

It is extremely tough and hardy, meaning it will last a long time.

M390 steel is very resistant to corrosive materials and rusting.

It can be polished to a mirror shine – not that important, but a high-quality blade should have an excellent finish, and it does make the end product more visibly appealing.

You can learn more about how traditional steel is made by visiting our Blade Steel Information page.

The Chemical Composition of M390

Sometimes known as the new 'super steel,' M390 performs well in most categories. This powdered steel is incredibly tough, hard wearing and corrosion resistant, as well as being great at keeping an edge. Many users report that after a months of hard outdoor use a knife cast in M390 steel barely needs a stropping. Although this gives us a little insight into how tough the material is, it doesn't tell us how it is made.

The unique method of manufacturing this steel allows the producer to use several different metals melted together so that they can get the benefits of each type. We sourced the chemical composition of M390 steel and found it to be as follows:

Carbon to 1.9%: Found in all steel types in differing quantities. Reduces toughness but increases hardness and wear.

Silicon to 0.7%: Adds to the hardness of steel and prevents air bubbles forming while it smelts.

Manganese to 0.3%: just enough to help tensile strength but not enough to lead to brittleness.

Chromium to 20%: Again, Chromium is found in all types of steel and is used to increase hardness, tensile strength, and corrosion resistance at the cost of toughness.

Molybdenum to 1%: A little of this helps keep that edge sharper than sharp, as well as making the steel stronger under high temperatures, allowing ease of molding; one of the industrial applications of M390.

Tungsten to 0.6%: Usually found wherever high amounts of Chromium are used. Tungsten increases the wear resistance of the knife, making up for the lack in the toughness of the Chromium.

Vanadium to 4%: Is used to produce fine-grained steel during heat treatment. Since powdered steel relies on the proper distribution of fine grains, Vanadium is a must. It makes for extra wear resistance and edge, too.

As you can see, the composition of M390 steel goes some way to explaining why it is so often chosen in the production of knives. Due to its hard-wearing nature, M390 steel knives are often favored by hunters and extreme outdoor use.

How is M390 Made?

First of all, a selection of the above alloys is placed in a furnace and smelted together. A variety of samples will be taken, and laboratory analyzed to make sure that the correct quantities are being used. If this is not so more alloy can be added to balance the mixture out. Once the steel mixture has the proper proportions, it is mixed with slag and then harmonized in an electromagnetic stir. It is subsequently atomized using nitrogen gas.

The next step is to remove the (now) powder particles which have been rapidly cooled by the gas. This rapid cooling has made the powder extremely fine grained. The powder is transposed into vats shaped as needed and put under 100 bar pressure once the container is sealed. A temperature of roughly 1100oc is applied to help the powder particles cling to each other. The heat and pressure are enough to close the gaps between the particles and make for a highly dense and therefore hardened steel.

It is estimated that the production of M390 steel in cylindrical vats will produce roughly 10% less whole product than traditional casting and pouring methods. That 10% has not been lost but has been condensed into the mixture to make for much denser steel. This powder manufacturing process is part of the reason that a knife cast in M390 steel will be more robust than most, and might even last you a lifetime.

How Does M390 Measure Up to Other Metals?

When it comes to choosing your ideal blade, there are a few categories you should bear in mind when buying. These include the hardness of the metal, the toughness or strength of the blade, both wear and corrosion resistance, edge retention and steel type. We have already established that M390 is tool steel, which puts it in the same category as D2, 52100, and A2 steel types. All of these have excellent edge retention and wear resistance, even although they may not be quite as hard as other steels. For more information on similar steels, see our previous article about knife steels.

Let's take a closer look at how M390 measures up in each category.

M390 Steel and Hardness

Bohler put the hardness of this tool steel at between 60 and 62 HRC. This hardness makes for medium-hard steel on the Rockwell Scale. Typically, a knife of a lower rating is softer and easier to sharpen but does not keep a sharp edge for long. A higher number on the Rockwell scale makes for a knife with better wear resistance that is harder to grind to a sharp edge.

M390 steel combines the best of both worlds, creating a harder blade that is easily grindable and very tough. These characteristics make it perfect for outdoorsmen, such as hunters and fishermen.

M390 Steel and Toughness

M390 Steel has decent toughness and a focus towards tensile strength, although it is not one of the things that make the steel so unique. According to Bohler themselves their steel scores only 2 out of five stars in terms of toughness. To make up for the toughness factor, they have focused on hardness, grindability, and corrosion and wear resistance. A knife cast in M390 steel might not be the toughest, but it will last you for a very long time, keep its edge and will need less work to maintain.

While this small lack in the toughness department makes this steel better for making screws and parts resistant to vibration in the construction industry; it does better in knife making. A knife is unlikely to be put under constant high stress like that of industrial machinery. Because Bohler knew there was a lack, they added metals into the composition that upgrade the tensile strength of the steel, meaning that it might not be hard enough to cut into concrete – but at least it won't break if you try.

M390 Steel and Wear Resistance

Bohler gives five out of five stars to their M390 steel as a tribute to the wear resistance. This metal is extremely high in wear resistance, to the point that it is one of the most durable tools you can buy. Because of the alloys used in the composition (namely the high quantity of Chromium) makes for an extremely long lasting metal. It is also more vibration resistant than other types of steel, making it perfect for manufacturing industrial strength screws (vibrations are unlikely to knock them free).

M390 and Corrosion Resistance

Bohler has their own chart for this that you can view through their web page. It shows that M390 steel is incredibly resistant to corrosion, consistently and at a variety of temperatures. We wouldn't recommend heating your good knife – but if you need to heat an M390 steel knife, it shouldn't break. Again, the Chromium is cited as the reason for the rust resistance of this metal. Consumers using M390 steel knives in wet conditions have found no spotting on their blades. Those who work in the ocean will tend to choose a metal that is specifically corrosion resistant instead.

So how does M390 steel compare to others in terms of corrosion resistance? Pretty well actually, but you can read more about it on the Spyderco Forum.

Edge Retention of M390 Steel

Although edge retention is not one of the main features trumpeted by the manufacturer; grindibility is. For steel of this particular hardness, M390 ought to be harder to grind than it is, but the composition and careful consideration of materials used has managed to combat this problem and produce a knife that does sharpen reasonably well.

Some consumers have reported that the M390 does hold a sharp edge for a while; others have said the opposite. What we do know is that it is easier to grind than other knives of similar steels – so if it does blunt, it will take less time to sharpen again. A good knife and an inferior knife will all need to be sharpened; the key is in how for how long it keeps the edge. The M390 steel knife will save you lots of elbow grease by comparison to other steel types. 

M390 Steel Type

As we previously covered, M390 is technically tool steel. This class means that it has been crafted with a focus towards hard use and wear and tear. It also scores highly in corrosion resistance, saying that it ought to be a knife that will last you for a long, long time.

Key Features of M390 At A Glance

At a glance, the key features of this steel type with regards to knife production are as follows:

Hard wearing, built to last knife that will last you many years if properly maintained.

Easy to grind, meaning you spend less time and energy sharpening it.

Extremely corrosion resistant in fresh water, rain or other elements. We would not recommend it for ocean use.

Will polish up to a mirror shine; if you want a knife for display purposes, M390 won't let you down.

Resistant to vibrations and mechanical shocks.

Cons of an M390 Knife:

It may spot or rust if used consistently in salt water without proper care or treatment.

Water resistance has been described as 'good enough.'

Our Recommendations for Using M390 Steel Knives

Here at Blade Ops, we sell a whole range of knives for your convenience – some of them featuring the sought after M390 steel knives of which we have been speaking. We would suggest that these knives make excellent outdoor tools to be used in the wilderness, as survival knives, for hunters and gatherers and all other types of outdoor activity for which you might need a knife. We also suggest that the mirror shine that many knives made with M390 feature, means these knives are excellent showpieces for any private collection.