CPM M4 steel, or just M4 steel is a steel that is recently catching on in popularity. This high-alloy steel is quickly gaining traction because of how versatile it is. Many call M4 a high-speed steel. M4 is high-alloy steel as well, fortified with high amounts of vanadium and molybdenum.
In this article, we’ll get into everything you need to know about M4 steel, with a special focus on what sets it apart from other steels, and how it performs when molded into a knife. M4 has some exceptional properties due to its chemical composition, and can virtually do ‘everything’ as this steel doesn’t compromise on hardness, toughness, or wear resistance.
This knife can be virtually molded into any kind of knife or tool but performs exceptionally well in certain applications. Certain kinds of knives really help the M4 capabilities shine. We’ll also recommend some of the best M4 steel knives in the market, carefully chosen through our expert vetting process — so make sure you stick around for the end of this article!
What is M4 Steel?
M4 is a high-speed steel. In case you don’t know what high-speed steel is, it is a category of steels that have the power to cut through any substance with ease, especially when compared to other kinds of steel. M4 is a premium, high-end steel made by Crucible Particle Metallurgy.
M4 has been previously used as a cutting competition steel, but now has a large variety of applications, especially mechanical ones. M4 is also a popular choice for those wanting to make custom knives. One of the best features of the M4 steel is its incredible toughness for impact and wear resistance, along with high hardness and edge retention.
This premium steel isn’t just used for high-end knives, it’s also used for durable fittings, castings and broach inserts.
What is the Composition of M4 Steel?
As a high-carbon, high-alloy steel, M4 steel has a lot of different elements that come together to form its composition. Naturally, the distribution of elements in M4 is very different from stainless steel generally used to make entry-level knives. Understanding what all the different elements in M4 have to offer is a great way to understand knife steels as well, as you’ll be able to why M4 delivers so much performance and durability.
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We’ll also look at the role that each element plays in the final product of M4 steel. Each element has a specific purpose in adding properties to M4 steel.
- Carbon 1.42% – This is a very high amount of carbon. That’s why M4 is considered high-carbon steel. Anything above 0.50% is usually considered a high amount of carbon, so you can understand why M4 has such a high amount of carbide at 1.42%. Carbon definitely contributes to the hardness of the knife blade but also plays a role in edge retention.
- Chromium 4% – Chromium plays two very important roles when added to steel. Primarily, it contributes to the corrosion resistance of the knife. 4% is enough chromium content for the M4 steel to have stainless steel properties and resist rust. The second role of Chromium is to fortify the strength of the steel. Chromium is the second hardest steel in the world, and it definitely increases the hardness of whichever steel its added to.
- Molybdenum 5.25% – Molybdenum is extremely important for the hardness and internal strength of steel. 5.25% is a very high percentage of molybdenum and M4 steel definitely benefits from this addition. You can attribute the exceptional hardness and toughness of the M4 steel to its high amount of molybdenum.
- Vanadium 4% – Vanadium has a triple impact on the hardness, toughness, and wear resistance of the steel? How? Vanadium actually impacts the grain structure of the steel itself. The power of Vanadium is one of the reasons why it’s so common as an alloy.
- Tungsten 5.50% – This high percentage of tungsten is added to M4 steel in order to increase its melting temperature. Increasing the melting temperature improves the heat processes and treatments that are possible for M4 steel.
- Manganese 0.30% – Manganese contributes towards the machinability of M4 and makes it more brittle.
- Silicon 0.55% – Silicon is deoxidizing during the heating process of making M4 steel.
- Phosphorus 0.03% – 0.03% seems like a very tiny amount, and it is, but this is enough for phosphorus to work its magic. Phosphorus significantly works towards the internal strength and structural integrity of M4 steel.
As you can see, M4 is a high-carbon steel, with higher amounts of other alloying elements.
How Hard is M4 Steel?
M4 has really high amounts of carbon, which is why it’s known for being steel with, particularly high hardness. On the Rockwell Hardness Scale, the M4 steel scores 65. 65 HRC is definitely on the higher end of hardness when it comes to steel. With 65 HRC, you can use M4 steel for virtually any kind of application, and it is perfect for knives. This is why M4 is so excellent for bearings and mechanical parts.
M4 Steel can also be at 63.5 HRC, according to the data published by CPM (Crucible Particle Metallurgy) but this is still on the higher side.
What is the Heat Treatment of M4 Steel?
M4 undergoes multiple heat treatment processes to get it to the level of hardness that’s intended, as well as preserving the other properties as well. M4 is preheated to 1450-1550°F (788-843°C) before it undergoes any further heat treatment techniques.
Quenching also occurs for M4 steel. Quenching refers to a heat process where the steel is heated to a high-temperature point and then cooled down in a controlled setting in a liquid. This can either be saline water, regular water, or even oil. M4 can be quenched in gas as well, and this also gives desirable results in hardness and internal strength. If M4 is being quenched in gas, it should be rapidly heated to 1000°F (538°C). If being quenched in saline water, it should be brought to 1000-1100°F (538-593°C) and then equalized. Quenched in oil can handle slightly lower temperatures.
After preheating, M4 steel can be austenitized between 2200-2250°F (1204-1232°C) in a furnace.
What are M4 Properties?
Now that we’ve looked at the chemical composition of M4 steel and the role each element plays, it’s time to dive into the actual capabilities of M4 steel.
As high-carbon high-alloy steel, the M4 greatly differs from regular stainless steel options.
You should always pay attention to the properties of steel if you’re planning to buy a knife that’s made from it. That’s because certain properties might be more important to you than others, and you might be willing to compromise on some weaknesses of the steel while others are a dealbreaker.
Let’s look at what the M4 can offer in terms of its properties, and how this affects a knife that’s built from it.
M4 has really high hardness for a steel. The HRC rating can range anywhere from 63-65 depending on the manufacturer and heat processes that were followed during the production of M4 Hardness. Having such a high hardness in the knife means that it’s on the brittle side and also retains a lot of strength in a knife.
Not only does M4 have high hardness, it also has great wear resistance against external situations and will last you a very long time.
Most of the time, hardness and toughness are inversely proportional. A high-hardness steel usually has low toughness, but not in the case of M4. The M4 actually has quite decent toughness and this makes it quite resilient in a knife. Having good toughness means that the knife won’t easily break when it comes in contact with harder substances.
A common problem with knives that aren’t tough enough is that the tip tends to chip off. That won’t be the case with the M4 knife.
M4 Edge Retention
M4 Steel has some of the best edge retentions that are possible in a knife. Due to the high amounts of carbon, a knife made out of M4 steel will have to be sharpened very rarely. The steel is so hard that there are very few dulling substances that the blade can come in contact with. While your kitchen knife made from M4 steel will likely damage a wooden cutting board, you won’t have to deal with sharpening your knife every time you use it.
M4 Ease of Sharpening
Unfortunately, you can’t have both high edge retention and ease of sharpening in steel. Due to its high hardness and high carbon content, its very difficult to sharpen a knife made out of M4 steel. Sharpening might take some time and effort.
The good news is that you won’t have to perform this task too often — once you sharpen your M4 knives, they remain sharp for a prolonged period of time.
M4 Corrosion Resistance
Corrosion Resistance properties come from Chromium. In the case of M4, the chromium content is too low for any incredible corrosion resistance properties. While M4 steel is stainless steel, don’t count on it to perform the corrosion resistance features for you. Knives made out of M4 are at risk of rust and corrosion which tends to happen often. However, with the proper care, you can ensure your M4 knife never catches rust.
Is M4 Good for Knives?
M4 is a great steel for Knives. Its exceptional hardness that doesn’t compromise on toughness, as well as great edge retention all make it a great reliable material for knife making. However, M4 works better for certain kinds of knives over others. M4 is great for bigger outdoor/survival knives or kitchen cleavers.
You would definitely have to take more care of your M4 knife compared to average knives due to its low corrosion resistance and ease of sharpening, but the performance of the knife is worth it!
Is M4 a Stainless Steel?
Yes, M4 is not a stainless steel due to the decent chromium content. You would have to take extra care of an M4 knife to ensure that it doesn’t catch rust or corrosion.
How Does M4 Compare to Other Steels?
M4 is a great knife if you’re big on hardness, toughness, and edge retention. However, in order to determine if it’s the best steel for the kind of knife you have in mind: you have to take a look at the other steel options. We’ve rounded up the three most similar steels to M4 in terms of price and properties in order for you to make an informed decision about which performs the best.
M4 Steel vs. 440C Steel
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The main differentiator between the 440C and the M4 Steel is corrosion resistance. Since 440c is stainless steel, it can offer much better corrosion resistance. However, M4 has better hardness, toughness, and edge retention.
M4 Steel vs. S30v
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Both these steels are high-carbon high-alloys that offer good toughness, but M4 has much better edge retention. The S30V has better corrosion resistance than the M4. It’s also easier to sharpen the S30V.
M4 vs. Maxamet Steel
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Maxamet Steel and M4 steel are both regular steels, and are not considered to be stainless steels. Maxamet steel has the advantage with edge retention over M4, while M4 scores much higher on toughness and hardness both.
M4 is great steel of choice for knives, despite not being stainless steel. We’re of the opinion that low corrosion resistance is not a big hindering factor. As long as the knife is kept clean and dry, you shouldn’t run into any kinds of issues with rust. Try to oil your knife once in a while to provide a protective layer against corrosion.
The high level of hardness and toughness that you get with this steel is possibly unmatched. Considering that you won’t have to bother sharpening an M4 knife often thanks to its great edge resistance is the cherry on top!
If you’ve been on the lookout for a steel that will make a high-quality knife to last you years: look no further. M4 steel is great value for money with incredible performance and capabilities as an outdoor/survival knife or kitchen cleaver.