If you have previous life experiences in using survival knives from famous brands like Ontario Knives and Cold steel, then you have already seen how the SK5 steel performs. This steel is widely chosen by manufacturers for the making of knives and various tools. We will be going in-depth regarding its chemical composition, steel properties and comparisons with other steels to get to know what makes it good knife steel.


What is SK-5 Steel?

SK5 steel is manufactured in Japan but has a low to medium range with high carbon in its chemical composition. The ‘SK’ in the steel stands for Steel Kuogu which is the Japanese translation of steel tool. The numeral ‘5’ signifies the impurity level. The lower the numeral the lesser the impurity level. Such as you will find SK2 the least impure in the SK series.


Brands like Cold Steel use SK5 steel for the manufacturing of utility knives. Previously Cold Steel was known to use carbon five steel which now they have replaced and started using SK5. Due to its high carbon percentage SK5 is categorised as high-carbon steel. The hardness of SK5 makes it adequate for the manufacturing of survival and tactical knives that will endure pressure outdoors. But the hardness is not right for the manufacturing of machetes.


The versatility of SK5 does not just end with knives. The steel is also used for the making of scalpel blades, razor blades and tools that have long edges. The hardenability and reasonable price also make manufacturing these easy.


Chemical Composition: 

SK5 is not stainless steel since the chromium percentage does not match the required threshold. Take a look at the function of other elements in their chemical composition.

  • 0.9% of Carbon: Works for improving the hardness and capacity of the steel to resist corrosion and wear.
  • 0.3% of Chromium: Increases edge retention and tensile strength. Prevents coronavirus and wear.
  • 0.25% of Nickel: Increases toughness level.
  • 0.5% of Manganese: Increases hardness level.
  • 0.35% of Silicon: Improves steel strength.
  • 0.25% of Copper: Prevents oxidation.
  • 0.03% of Phosphorus: Adds strength.
  • 0.03% of Sulphur: Improves machinability.


Steel Hardness: 

According to the Rockwell C scale, the hardness rating of SK5 steel is about 65 HRC. The hardness is considered high as it is above 61 HRC. The presence of a high percentage of carbon makes the steel have immense hardness. But depending on the heat treatment provided to the steel the hardness level can vary.


You will come across some SK5 knives that have a hardness level of around 55 HRC. The hardness level is enough for EDC knives which gives an advantage as well for easy sharpening of the edge. But when the matter is about making heavy-duty knives, the hardness rating of the steel has to be about 65 HRC.


Steel Properties:

  • Decent Toughness: With increasing hardness, the toughness lowers and also the brittleness of steel increases. You will see all the super steels with great hardness are brittle. Yet, SK5 does have a decent amount of toughness to resist breaking and chipping.
  • Superb Wear Resistance: SK5 has extreme wear resistance due to the high level of hardness. The wear resistance allows SK5 to endure heavy duty regularly which is why it is used for the manufacturing of survival knives.
  • Great Edge Retention: This is the second-best property of SK5 steel. Due to great edge retention capability, the SK5 steel edge does not lose its sharpness even after heavy duty. You will not need to spend a lot of time and effort re-sharpening the edge.
  • Okayish Corrosion Resistance: SK5 is not stainless steel, hence it is weak at keeping corrosion and rust at bay. Yet, you will witness some performance in corrosion resistance due to the presence of some amount of chromium. Some manufacturers use an anti-corrosion layer on the surface of the steel to help improve corrosion resistance.
  • Ease of Sharpening: Sharpening the edge of SK five steel is challenging because of the 65 HRC hardness rating. You will require to use advanced sharpeners that tend to have an expensive price. But you will not require sharpening frequently due to superb edge retention.


Comparison with Other Knife Steel Options: 

SK5 vs 1095

Both of these steels deliver similar performance. The carbon percentage in both of these steels are also similar resulting in the same hardness level. But SK5 beats 1095 in toughness and corrosion resistance.


SK-5 vs SK-4

SK4 has a greater carbon percentage than SK five which also means it is the harder one. Due to increased hardness SK4 is better at edge retention and wear resistance than SK5. But SK5 has greater toughness and is easier to sharpen.


SK5 vs SK-7

SK5 has more purity than SK7 and has a greater amount of carbon, which makes SK5 better at edge retention and wear resistance compared to SK7. On the other hand, SK7 stands out in toughness level, ease of sharpening and resistance chipping.


SK5 vs VG10

VG10 has a greater hardness and better toughness as well due to the presence of vanadium when compared to SK5. The chromium percentage is also higher in VG10 making it better at corrosion resistance than SK5. SK5 is the easier one to sharpen and is also more affordable than VG10.


SK5 vs O1

Both of the steels have similar hardness ratings but SK5 is seen performing better at edge retention than O1.


So, is SK-5 a Good Knife Steel?

Indeed SK5 is a good knife steel. You will easily get knives made out of it from well-known brands. Manufacturers opt for this steel due to the excellent features of the steel that includes edge retention and wear resistance. The only fact to keep in mind is the poor capability of the steel to resist corrosion. It is better to keep moisture away from its surface and maintain it well.



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