The material of the blade is an extremely important aspect of any knife. And there are many types of steel that are used for knife blades. Some are relatively soft steels, which can dull fairly quickly, but are easily re-sharpened. Other steels can be very hard and therefore can be polished to an extremely sharp edge, but can be easily chipped or broken if used improperly (for prying, for example).
In the world of knife steel, there is always a trade-off between strength (ductility or the ability to bend rather than break), toughness (ability to withstand impacts without deforming), edge retention, and corrosion resistance. Generally, as one characteristic increases, another will decrease.
For example, some of the strongest and hardest knives are only moderately sharp (comparatively speaking) and are very susceptible to rust. But with proper maintenance, they can offer a life of heavy use that would damage or destroy a knife made from a different type of steel.
The choice of blade steel will affect the proper use of the knife, its ease or difficulty of manufacture, and, of course, its price. Let’s take a brief look at some of the most popular blade steel options available.
Brief introduction to Blade steel
All steel is made of iron, with some carbon added. Various grades and types of steels are created by adding other “alloying” elements to the mix. “Stainless” steel, by definition, contains at least 13% chromium. “Non-stainless” steels are also known as carbon steels or alloy steels.
Despite its name and late-night television reputation, stainless steel is not stainless. Like all steel, it will also rust. The high level of chromium in stainless steel helps decrease corrosion, but cannot completely prevent it. Only proper maintenance and handling will keep your knife completely rust free. (And basically, that just means keeping it clean and dry, greasing it lightly every now and then, and not storing it in a sleeve. It’s that simple. Oh yeah: no dishwasher. Never.)
Generally speaking, there are three grades of steel that are used for knife blades: good, better, and better. Each type of steel has unique properties that make it best suited for specific designs and applications. And, of course, the choice of steel will affect the price of the knife.
Good sheet steel
Knives that use “good” steel blades should be considered entry-level and tend to be made of rust-resistant (not rust-free – see above) stainless steel. Typically made in Asia, these knives offer pretty good value for money. These blades are typically “softer” and therefore require more frequent sharpening to maintain good edge performance. But, because they are in fact ‘softer’, re-sharpening is quite easy. Some of the most popular stainless steel sheet materials in this class are 420, 440A, and 7Cr13MoV.
420 stainless steel has slightly less carbon than 440A. Many knife makers use 420 because it is inexpensive and resists corrosion quite well. 420 steel sharpens easily and is found in both knives and tools.
The relatively low cost and high corrosion resistance of 440A stainless steel make it ideal for kitchen cutlery. While it exhibits characteristics similar to the better quality AUS 6 steel, it is considerably less expensive to produce. 440A contains more carbon than 420 and is therefore a “harder” steel. This allows for better edge retention than a 420 blade, but is more difficult to re-sharpen.
7Cr13MoV is a good steel sheet, which has molybdenum (Mo) and vanadium (V) alloying elements added to the matrix. Molybdenum adds strength, toughness, and toughness to steel, while improving machinability. Vanadium adds strength, wear resistance, and toughness. Vanadium also provides resistance to corrosion, which is seen in the oxide coating on the blade.
Best sheet steel
Higher quality stainless steel blades contain higher chromium (Cr) content than their entry-level counterparts. Since the amount of chromium increases in the manufacturing process, these sheets are more expensive. Chromium provides greater edge holding ability, which means the blade will require less frequent sharpening. These better quality knives sharpen reasonably easily, but proper sharpening techniques are important. The combination of great value and performance makes these blades perfect for everyday use. Examples of these types of steel are AUS 6, AUS 8, 440C and 8Cr13MoV.
Both AUS 6 and AUS 8 are high quality Japanese chrome steels, providing a great balance of toughness, strength, edge retention and corrosion resistance, all at a moderate cost. These blade steels will measure a hardness of 56-58 on the Rockwell hardness scale (HRc). The carbon content of AUS 8 is close to 0.75%, which makes it very suitable as a blade steel. AUS 6 and AUS 8 are very popular with many knife makers because they are cost effective and good performance steels.
440C is a reasonably high quality cutlery steel, similar to the AUS series. However, 440C contains more carbon, which increases the hardness of the steel. Its toughness and relatively low cost make 440C stainless steel attractive to many knife makers for their mid-range blade series.
Chinese 8Cr13MoV stainless steel has a high performance / cost ratio. It is often compared to AUS 8. 8Cr13MoV is tempered to a hardness range of 56-58 on the Rockwell scale. This relatively high hardness can be attributed to the higher moly and vanadium content of the steel.
Best sheet steel
Both the United States and Japan make the best quality stainless steel for knife blades. Unfortunately, the higher chromium content in these blade steels comes at a premium price. The addition of elements such as vanadium and chromium offers superior sharpness and edge retention, as well as very high rust resistance. These steels are used for more demanding tasks such as hunting and fishing, tactical self-defense, and military applications. A sample of steels in this group would include CPM 154, CPM S30V, VG-10 and San-Mai steels.
US-made CPM 154 premium grade stainless steel originated for tough industrial applications. This steel combines the three main elements of carbon, chromium and molybdenum. CPM 154 provides excellent corrosion resistance with good toughness and edge quality. Well known for its overall performance as a knife blade steel, CPM 154 touts a hardness of 57-58 on the Rockwell scale.
CPM S30V, a powdered stainless steel, was developed by Crucible Metals Corporation (now Crucible Industries). Noted for its durability and resistance to corrosion, it is considered one of the best steels ever created. The chemistry of CPM S30V promotes the formation and balanced distribution of vanadium carbides throughout the steel. Vanadium carbides are harder and therefore provide better cutting edges than chromium carbides. Additionally, vanadium carbides provide a highly refined grain in the steel that contributes to sharpness. and hardness of its edge.
VG-10 is a high-end Japanese steel, manufactured by Taekfu Special Steel. Its matrix includes vanadium, a large amount of chromium, molybdenum, manganese, and cobalt. Vanadium contributes to wear resistance (edge ​​retention) and improves the corrosion resistance of chrome. Molybdenum adds additional toughness to steel. The general combination of elements results in a very strong and durable steel. As such, VG-10 is a renowned steel blade specially designed for high-quality cutlery. Blades made from VG-10 can be polished to a sharp edge and still offer extreme durability without becoming brittle. Blade hardness for VG-10 is around 60 on the Rockwell hardness scale.
San-Mai (Japanese for “three layers”) is a composite steel used in many of the high-end knives manufactured by Cold Steel. The core of the blade is a layer of VG-1 steel, sandwiched between the outer layers of 420J2 steel. San-Mai steel blades offer superior durability and excellent corrosion resistance, important to those who depend on their knives for hunting and fishing, as well as for tactical and military applications.
Different steels for different uses
As you can see, not all blade steels are the same. Some are harder than others, but will be more brittle or prone to chipping, while some may be stronger or have a better edge, but will be more difficult to sharpen once they have become dull.
A quality designer or fabricator will select the appropriate blade steel for a knife based on the properties of the steel, in accordance with the intended application of the knife. Think about the difference between your kitchen chef’s knife compared to a knife used for underwater diving or a knife used in a military or combat application.
Knowing a little about the characteristics of the different blade steels will help you make the right choice when it comes time to buy your next knife.