K390 is a high-end premium high-alloy steel with extremely high performance. This cold work steel has high hardness and is a popular reliable choice. The K390 is also used as a Police weapon in the United States.
Let’s find out how K390 is made, its chemical composition, and how it compares to other competitive steels in the market!
What is K390?
K390 is a high-alloy steel that’s been fortified with high quantities of Vanadium and Tungsten. K390 is cold-work steel that’s been manufactured by the German steel production brand Bohler-Uddeholm. K390 is made with unique MicroClean Technology. MicroClean Technology is also called Crucible Particle Metallurgy and is responsible for K390’s even grain distribution. This means that it is a very hard crystalline stainless steel that’s high in carbon and has been made with two phases of heat treatment.
Apart from being used for premium high-performing and durable knives, you’ll also find K390 being used in slitters, cutters, parts of screws and bolts, and even in the medical industry. It has great blanking properties making it the steel of choice for manufacturers across boards. It’s not often used in the food industry unless it has been coated with a non-stick or corrosion resistant coating since K390 does not naturally have corrosion resistance.
K390 has incredible machinability and internal strength. When made into a knife, it lasts for an exceptional amount of time thanks to its wear resistance and strong grain density.It was one of the more unique steels with high carbide quantity and fortified with vanadium for hardness and toughness. What makes K390 so unique is that despite being a high-alloy steel, there’s no compromise on toughness. The carbide distribution is even throughout the steel, lending to great toughness at the degree of hardness.
Composition of K390
Let’s look at all the different materials that come together in the composition of the premium high-alloy cold-work steel K390. It has a very unique blend of materials that contribute to the steel’s capabilities and properties.
- 2.47% Carbon – K390 has a lower content of carbon compared to other stainless steels. If it wasn’t fortified with other alloys, it would be very low on hardness with this quantity of carbon.
- 4.20% Chromium – The extremely high percentage of chromium is why K390 is so corrosion resistant. Chromium is the substance that’s put on metal parts as an external coating to ensure there’s no rust formation. You’ll also find chromium on non-stick kitchen appliances as a protective layer. But it’s not just the corrosion resistance that Chromium helps with. Chromium also contributes towards wear resistance, by increasing the tensile strength of the steel itself.
- 3.80% Molybdenum – Molybdenum has an important role in increasing the machinability of this steel. Machinability refers to how easy it is to shape and cut the steel. K390 has decent machinability because of the molybdenum content present in it.
- 0.40% Manganese – Manganese greatly increases K390’s strength, making it the perfect machinable steel for a variety of applications.
- 0.55% Silicon – Silicon deoxidizes steel, particularly in the smelting process. Additionally, silicon contributes to strength and flexibility.
- 9% Vanadium – Vanadium is one of the alloys that is added to K390 in order to fortify it and make it stronger. Vanadium particularly helps with increasing the toughness of the steel. With a very low percentage of carbon, K390 would have been very hard and brittle, and vanadium helps with strengthening it.
- 2% Cobalt – Cobalt is an interesting addition to K390 since not all steels have Cobalt added to them. In K390’s case, Cobalt improves the heat treatment conditions of this martensitic steel.
- 1% Tungsten – Tungsten also contributes towards corrosion resistance, just like Chromium. Additionally, Tungsten helps with wear resistance and by increasing the hardness of K390.
When we call K390 high-alloy steel, we’re referring to the added quantities of Vanadium, Cobalt, Molybdenum, and Tungsten. These added elements tend to be quite rare in steel, especially in low-carbon steel like K390. These unique elements are responsible for a very unique steel with impressive properties.
What is the Heat Treatment of K390?
K390 is cold-work powder steel, which means it undergoes two-fold heat treatment in tempering and quenching. Tempering refers to the high heating and cooling of the steel without any other mediums, while in quenching, the steel is heated and cooled through water or any other liquid such as saline water or oil. Both these processes contribute towards increasing the tensile strength of the steel and making it more resistant to different kinds of internal stresses.
The most common tempering temperature range for K390 is 400-750°F (200-400°C). This increases its strength and toughness while also increases corrosion resistance. Some manufacturers choose to increase this temperature for better stability, compression yield, but this can have an adverse effect on the corrosion resistance capabilities of K390. The maximum heat that it can be brought to in an effort to increase the tensile strength is 1025-1050° F (550-565°C).
The method that is typically followed for the tempering heat treatment is holding the cooling temperature for 2 hours before repeating the process three times for maximum results.
Quenching is typically done in a salt quench, or even in an interrupted oil quench. The temperature range in which this process is carried out is 250°F/min (140°C/min), at the minimum but can be increased even further. For a gas quench, a 4 bar quench is typically carried out.
Apart from tempering and quenching, K390 can also undergo annealing, austenitizing, and deep freezing.
K390 Steel Properties
We’ve spoken a lot about how K390 is a unique high-alloy steel. Let’s find out what’s so great about K390, and why its properties perform better than its competitors in the market. There’s a reason why K390 is considered a premium high-alloy steel and has such a wide range of applications.
K390 has a Rockwell hardness scale of 64. 64-65 HRC is a very high score and means that this steel is high in hardness without actually being brittle. There are a couple of factors that contribute towards K390 having high hardness: the high amount of carbon, fortifying of vanadium, and molybdenum.
This is more than enough hardness for a kitchen knife, and also works great for an outdoor survival knife.
K390 is not extremely high on toughness, but it’s still pretty decent compared to other steels with comparable properties. Since it’s high on hardness and corrosion resistance, you’d expect it to be very low on toughness (which is the case with other steels) but the toughness is still decent in the K390.
The toughness of K390 is enough for it to work as a sturdy outdoor knife. You can use K390 knives as survival knives or even hunting knives, and they can definitely stand up to tougher substances like wood or animal carcasses.
K390 Edge Retention
Edge retention is a really important property of steel, particularly when you’re considering if it will be a good material for knives. No one wants to be constantly sharpening their knives after every use. The K390 is possibly the best edge retention out of other knives in the market. That’s because it has a high percentage of Vanadium, which plays an important role in hardness and edge retention. You won’t have to keep sharpening a knife that’s made out of K390, making it a great choice for outdoor knives.
K390 Corrosion Resistance
K390 is not a corrosion resistant knife. That’s because it has very low amounts of chromium and is not considered to be a stainless steel either. Chromium is responsible for corrosion resistance as it provides a protective barrier against the formation of rust in steel. Even though K390 has chromium, the amount is too low for corrosion resistance, and it only contributes to hardness in K390 steel.
If you’re buying a K390 steel knife, you’ll likely find one with a protective anti-rust coating that the manufacturer has forged. If the knife doesn’t have corrosion protection, don’t worry! You can still take some simple measures to ensure that your knife doesn’t catch any rust.
Always keep it clean and dry try to avoid any contact with moisture. If you live in a humid weather conditions, oil your knife with some mineral oil. It should be food-grade oil if you plan to use it as a kitchen knife.
K390 Ease of Sharpening
Honestly, you won’t spend much time worrying about how and when to sharpen your K390 knife since it has such great edge retention. You might have to sharpen it once in a blue moon, for specific requirements that need your knife extra sharp. Since the K390 is so hard, it’s also quite difficult to sharpen.
This is the only possible caveat of owning a K390 knife — but with the right knife sharpening tools, you can still get the job done. If it’s any reassurance, you’ll spend very little time trying to sharpen your K390 knife at all!
Is K390 Good for Knives?
It’s clear that K390 is an excellent choice for knives, with high hardness, exceptional corrosion resistance, long edge retention, and decent toughness. This is the kind of knife that needs minimal care and is worth the investment since it stays in much the same shape and condition from the day you purchased it. It’s particularly great for outdoor adventures where you can’t carry sharpening tools with you.
Does K390 Form Rust?
K390 is prone to forming rust and corrosion if not taken care of since it is not a stainless steel. Opt for a knife with an extra external coating of anti-rust when possible. Otherwise, it’s a good idea to take care of your knives all the same. We recommend keeping your knives clean and dry, and never soaking them in water unnecessarily. This will ensure that your K390 knife stays in brand new condition and remains rust-free forever.
How Does K390 Compare to Other Steels?
K390 is a premium high-alloy steel and is a great choice for someone looking for an extremely durable and reliable knife to last them a long time. Since it isn’t exactly considered a budget knife, you might want to check out K390’s competitors before you finalize your decision.
Here we’ve rounded up the closest competitors to K390 so that you can see how it compares and holds up to different steels in terms of five different properties: Edge Retention, Ease of Sharpening, Corrosion Resistance, Toughness, and Hardness.
K390 vs. S90V
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K390 and S90V are very close competitors, while also being very similar in their properties. The main difference is that you get higher hardness with K390, but higher toughness with S90V.
K390 vs. S30V
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S30V has less Hardness than the K390, making it easier to sharpen, and with lesser edge retention. However, K390 is still superior in terms of hardness.
K390 vs Maxamet Steel
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Maxamet Steel is another premium steel with great hardness and edge retention, making it a great outdoor knife. However, Maxamet Steel is not stainless steel and clearly has very poor corrosion resistance, making it prone to rust. They’re both very hard steels with low toughness, and difficult to sharpen.
Best K390 Knives in the Market
Now that we’ve established that K390 is a great premium steel perfect for knives, let’s get into which knives you should purchase! We all know that great material is only half the ball game of a good knife — it’s also important to look at the blade geometry and build. A poorly designed knife can compromise on the great properties of premium steel, and the opposite is true as well. That’s why it’s so important to choose a knife that has both — premium steel and great design.
Since K390 is a premium high-end steel with high quality, you won’t find lots of budget knives made out of it. A K390 is a knife that will last you a really long time, so it’s worth putting in the effort to choose your investment.
Best K390 Pocket Knife
K390 is a great material for pocket knives, and we find that Spyderco’s Spyderco Delica 4 Lightweight Folding Knife with K390 Premium Steel Blade and Durable Blue is one of the best pocket knives in the market.
With a 2.95” inch blade and easy-to-grip blue fiberglass handle, this knife has a Paramilitary-inspired design and can easily be flipped and closed open with one hand.
We especially like how lightweight this pocket knife is, it’s not going to weigh down your pants in your pocket! This knife will be a trusty companion in all of your outdoor adventures and is easy to carry as well.
Best K390 Budget Knife
It’s difficult to find a budget knife made out of premium K390 steel, so this Spyderco Penknife is an absolute steal. This Spyderco UK penknife has a lightweight blade with open-back construction that measures 2.95”.
The construction deserves a special mention — the flat bevels really reduce drag during the cutting experience, making this knife a wonder to behold!
If you’re looking for a trusty outdoor or survival knife to accompany you on all of your escapades, it makes sense to invest in a knife made from K390. You’ll enjoy the incredible edge retention, as well as no compromises on toughness and sturdiness!