CPM M-4 Tool Steel
CPM M-4 Tool Steel is a high vanadium special purpose high-speed steel exhibiting better wear resistance and toughness than M-2 or M-3 in cold work punches, die inserts and cutting applications, but these reasons are why it is widely used in competition cutting blades and custom knives.
A brutally tough steel, CPM M-4 bears a fair warning it is hard to work within a hardened and tempered state. While it may eat up belts grinding it after hardening, its superior edge retention and general toughness make it near impossible to ignore and worth the trouble.
However, if you are used to tough to grind and polish steels, you will be more than ready to try your hand with M-4 and will undoubtedly find yourself grinning the first time you test its edge.
Is CPM M-4 steel stainless? The answer is No, it’s not stainless steel. To be considered stainless steel the CPM M-4 must have a minimum of 12% of chromium in it. Therefore it’s a tool steel. It can be considered carbon steel since it has high carbon (more than 1% of carbon in the chemical composition).
CPM M4 Tool Steel Chemical composition
1.42% of Carbon: It improves hardness and wear/corrosion resistance, but a high amount of it decreases strength.
4% of Chromium: For tensile strength and Edge retention, and enhances corrosion resistance and wear resistance.
5.25% of Molybdenum: Increase Machinability and strength.
0.3% of Manganese: Increases hardness and brittleness.
0.55% Silicon: Improves Strength.
0.03% of Phosphorus: Increases strength.
0.06% of Sulfur: Increases machinability.
4% of Vanadium: Improves wear resistance and hardenability.
5.5% Tungsten: Improves wear resistance and hardness.
As you can see, the combination of the CPM M-4 Steel includes Chromium, Molybdenum, and Vanadium, which gives it a mix of toughness, wear-resistance, and corrosion resistance.
What are the CPM M-4 tool steel properties
According to It chemical composition and hardness, the CPM M-4 offers the following properties:
Edge Retention: with a hardness of 65HRC, the CPM M-4 offers an exceptionally edge retention, one of the best in tool steels even in carbon steels.
Corrosion Resistance: The CPM M-4 corrosion resistance isn’t the best as the edge retention; with 4% of chromium, it offers decent corrosion resistance.
Wear Resistance: being high in Vanadium and Molybdenum, the CPM M-4 has excellent wear resistance.
Sharpness: The harder the steel, the harder to sharpen it, this rule applies to all steels, if steel offers an excellent wear resistance then it will be hard to sharpen.
Machinability: With the increased Sulfur (0.06%) it offers good machinability, with no effects on the toughness.
Toughness: This is why the CPM M-4 is considered high-end steel, it offers a great toughness while being hard steel, the rule is simple: the harder the steel, the lower it’s toughness, but it’s not the case for the CPM M-4, it’s combination has higher hardness and toughness in exchange of corrosion resistance.
Is CPM M-4 steel good for knives?
Of course, it is, If you’re looking for a balance between hardness, toughness, wear resistance and corrosion resistance, the CPM M-4 steel would be a great choice for your knife, the rule of all steels is the “Hardness, Toughness, Corrosion Resistance, You only get two of the three,” well magically the CPM M-4 offers the three in a balanced way, Even if the corrosion resistance isn’t excellent as the hardness/toughness, but still it’s good enough compared to other steels.
For CPM M-4 Heat Treatment Recipe follow this link:
CPM M-4 TOOL BLADE STEEL - HEAT TREATMENT RECIPE