Blade material is an extremely important aspect of any knife. And there are many types of steel used for knife blades. Some are relatively soft steels, which can dull quite quickly but can be easily resharpened. Other steels can be very hard and therefore can be ground to an extremely sharp edge, but can be easily chipped or broken if used inappropriately (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), hardness (ability to withstand impact without warping), edge retention and corrosion resistance. . Generally, as one characteristic increases, another decreases.
For example, some of the strongest and hardest knives are only moderately sharp (in comparative terms) and are very susceptible to rust. But with proper maintenance, they can offer a lifetime of heavy use that would damage or destroy a knife made from another 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 sheet steel options available.
A brief introduction about Blade Steel
All steel is made up of iron, with some added carbon. 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 its reputation on late-night television, stainless steel is not stainless. Like all steel, it also rusts. 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, lightly oiling it from time to time, and not putting it in a bag. Simple as that. Oh yeah: no dishwasher. Ever.)
Very generally speaking, there are three grades of steel used for knife blades: good, better, and best. Each type of steel has unique properties that make it more suitable 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 stainless steel (not rust free, see above). Typically made in Asia, these knives offer pretty good value for money. These blades tend to be ‘softer’ and therefore require more frequent sharpening to maintain good cutting edge performance. But, because they are in fact ‘softer’, resharpening them 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 fairly well. 420 steel sharpens easily and is found in both knives and tools.
The relative low cost and high corrosion resistance of 440A stainless steel make it ideal for kitchen cutlery. While it exhibits similar characteristics to better grade 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 blade made from 420, but is more difficult to resharpen.
7Cr13MoV is a good blade steel, having the alloying elements molybdenum (Mo) and vanadium (V) added to the matrix. Molybdenum adds strength, hardness, and toughness to steel, while improving its machinability. Vanadium adds strength, wear resistance, and toughness. Vanadium also provides corrosion resistance, which is seen in the oxide coating on the blade.
best sheet steel
Better quality stainless steel blades contain a higher Chromium (Cr) content than their entry level counterparts. Since the amount of chrome increases in the manufacturing process, these blades are more expensive. Chrome provides greater edge holding power, which means the blade will require less frequent sharpening. These better quality knives sharpen fairly easily, but it is important to use proper sharpening techniques. 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-grade Japanese chrome steels, providing an excellent 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 manufacturers because they are cost effective and perform well.
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 hardness and relative low cost make 440C stainless steel attractive to many knife manufacturers for their mid-range knife series.
Chinese 8Cr13MoV stainless steel has a high performance-to-cost ratio. It is often compared to AUS 8. 8Cr13MoV tempers to a hardness range of 56-58 on the Rockwell scale. This relatively high hardness can be attributed to the higher molybdenum 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 sheet steels comes at a higher price. The addition of elements such as vanadium and chrome offers increased sharpness and edge retention, as well as very high resistance to oxidation. 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.
American-made CPM 154 premium stainless steel originated for demanding 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. Known for its general performance as a knife blade steel, CPM 154 touts a hardness of 57-58 on the Rockwell scale.
CPM S30V, a powder fabricated 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 chrome carbides. Additionally, vanadium carbides provide a highly refined grain in the steel that contributes to sharpness. Y edge hardness.
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 hardness to steel. The overall combination of elements results in a very strong and durable steel. As such, VG-10 is a renowned blade steel specially designed for high quality cutlery. Blades made from VG-10 can be ground to a razor-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 made by Cold Steel. The core of the blade is a layer of VG-1 steel, sandwiched between outer layers of 420J2 steel. San-Mai steel blades offer superior durability and excellent corrosion resistance, important for those who rely on their knives for hunting and fishing, as well as 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 dull.
A quality designer or fabricator will select the appropriate blade steel for a knife based on the properties of the steel, according to the knife’s intended application. Think of the difference between the chef’s knife in your kitchen versus a knife used for diving underwater, or a knife used in a military or combat application.
Knowing a little about the characteristics of different blade steels will help you make the right decision when it comes time to purchase your next knife.
