SK5 Steel: Is it a Good Knife Steel?

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If you have ever looked for survival knives from brands such as Cold Steel or Ontario Knives, chances are high you have seen blades made of SK5 steel. Yes, this steel is widely used in making knives and other tools. This review explores the chemical composition, properties, and comparisons with different steel variants.

What is SK-5 Steel?

Cold Steel 49LCK Srk SK5, Boxed, One Size

SK5 is a Japanese low- to mid-range steel boasting high carbon. It is considered equivalent to the 1080 steel. The name comes from ‘Steel Kuogu,’ which means steel tool. Digit 5 represents the level of impurity. SK2 and SK4 are purer than SK5 but have fewer impurities than SK7.

Many brands have started using this steel, particularly for making utility knives. Even Cold Steel has replaced Carbon 5 steel with SK-5 for many knives.

Due to high carbon content, SK5 is considered high-carbon steel and is harder than most steel variants. Its hardness is not suitable for making tools such as machetes but is ideal for making tactical and survival knives in extreme outdoor surroundings.

Apart from knives, SK5 high-carbon steel is used to make various tools such as scalpel blades, razor blades, and long-edged tools because of its hardenability and affordable price.

Chemical Composition

SK5 is not a type of stainless steel, as its chromium content is too less than required for stainless steel. Many knife users believe that it is not worth buying an SK5 knife. However, it excels in a few other properties. Following are its ingredients:

  • 0.9% Carbon: For better hardness as well as the ability to keep wear or corrosion away
  • 0.3% Chromium: For great tensile strength, superb edge retention, and prevention of wear and corrosion
  • 0.25% Nickel: For a high level of toughness
  • 0.5% Manganese: For more hardness
  • 0.35% Silicon: For better strength
  • 0.25% Copper: For the prevention of oxidization
  • 0.03% Phosphorus: For more strength
  • 0.03% Sulfur: For better machinability

Steel Hardness

On the hardness Rockwell scale, SK5 has a rating of 65 HRC, due to which it is considered a very hard option, just as the D2 tool steel. This is because of the high content of carbon. However, depending on the heat treatment that a brand implemented, this rating is likely to differ from one brand to another.

Do not be surprised to come across an SK5 knife whose hardness level is just 55 HRC. This level is hard enough for most EDCs, as the edges are easier to sharpen and are less brittle. However, a hardness level of 65 HRC is required for making heavy-duty knives.

Steel Properties

Cold Steel 49LCK Srk SK-5, Boxed, One Size

The chemical mix determines the properties of any steel.

  • Decent Toughness: A harder steel is less tough and more brittle. So, all super-hard steels are brittle. The high level of hardness makes it less tough, but it has a decent level of toughness due to which it will not break or chip.
  • Superb Wear Resistance:  SK5 offers superb wear resistance and will last for very long. They are made to last, particularly if used with the unbreakable G10 handle.
  • Great Edge Retention: This is another remarkable property of this steel. You can expect excellent edge retention, which means the edge will not dull quickly and remain sharp for a long time. As a result, you will not spend time sharpening the edge again and again.
  • Okayish Corrosion Resistance: As SK5 is not stainless steel, it is not resistant to corrosion and rust. However, including a small amount of chromium makes it somewhat resistant to rust and corrosion. Therefore, nowadays, knife makers tend to finish their SK5 blades with an anti-corrosion coating.
  • Ease of Sharpening: This is another weak point of SK5 carbon steel. Being too hard with 65 HRC, it is challenging to sharpen the edge. Sharpening it will take more time and effort than any other softer steel. Therefore, we recommend using an advanced sharpening system. However, as it sustains a sharp edge for long, there is no need to resharpen it frequently.

Comparison with Other Knife Steel Options

The chemical composition of SK5 is quite similar to W2 and 1084, both being carbon steels. All three are good at toughness, edge retention, and corrosion resistance. They also belong to a similar price range.

SK5 versus 1095

These steel options are similar; they contain the same amount of carbon. However, 1095 is a bit harder, while SK5 is a bit tougher. Further, 1095 isn’t good at corrosion resistance as SK5. Hence it usually comes with a rustproof coating.

SK-5 versus SK-4

The latter one has more Carbon content than the former, hence slightly harder. Thus, SK4 is more resistant to wear and retains a sharp edge longer than SK5. However, sharpening an SK4 edge is more difficult. It is also less tough.

SK5 versus SK-7

SK5 is purer than SK7. It also contains more amount of carbon, which means better edge retention ability and wear resistance power. On the other hand, SK7 is less susceptible to chipping and is easier to sharpen.

SK5 versus VG10

The latter steel is quite hard, but the presence of Vanadium contributes to good toughness as well. Moreover, due to higher  Chromium content, it is more resistant to corrosion than SK5. On the other hand, it is not easy to sharpen a VG10 edge. Further, a VG10 knife is costlier.

SK5 versus O1

The latter steel has been in use since the 1940s. Its hardness rating can go up to 64 HRC, but it does not ensure better edge sustenance. Further, due to a high hardness level, toughness is less in O1.

So, is SK-5 a Good Knife Steel?

If you go for a reputable brand, you can quickly get an excellent SK5 steel knife with superb wear resistance as well as great edge retention. Such a knife will also be tough enough to keep chipping at bay.

The only thing you need to be wary of is corrosion and rust, mainly if you are using your knife in damp situations. So better go for one that comes with a rustproof coating.