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The Basics of Knife Steels: Part 2
Adding more carbon to iron makes steel
The addition of carbon to iron is what makes it steel. Steelmakers can alloy up to 2% carbon with iron, and there are surprising differences as fractions of a percent of carbon are added to the mix. Steel that has up to .34% carbon (that is, approximately one-third of one percent) is considered low-carbon steel. To harden these steels, additional carbon must be added, and the most common method is the case-hardening process. When a steel has .35% of carbon in its mix, it is considered a high-carbon steel. The more carbon, the harder and more abrasion-resistant the steel becomes.
One common knife steel is 1095, as seen in this Ka-Bar knife. The number 1095 means the steel contains .95% carbon. Such steel sharpens to a very fine edge and has good resistance to abrasion when the steel has been properly hardened after the knife blade is manufactured.
Another steel that took the world by storm several years ago is D-2. This steel is so tough that it is used to make dies from which other steel objects are manufactured. You can hit this steel with hammer blows, yet it retains its crisp, sharp shape. Consequently, it also holds an edge longer than most other steels. One other interesting aspect of D-2 is that it has a high chromium content that almost makes it stainless. Several knife manufacturers lump D-2 in with their stainless steels because of this. We carry several D-2 knives, and one good example is this Muskrat Knife made by Knives of Alaska.
Blades made from something other than steel
Let's talk about something other than steel that can be used to make a good blade.
Sintering is a process of heating metal powders to very high heat, then compressing them rapidly. The powders weld to one another without becoming a solid object. To look at the finished product, you can't tell that it's not a solid piece of metal. The advantage is that complex shapes can be formed more readily using materials that are extremely difficult to machine.
Titanium is a lightweight metal that has incredible strength, but it cannot be hardened using normal methods. However, the Japanese have recently discovered a way to incorporate titanium into superior knife blades. One good example of a titanium blade is Boker's Zeta Knife. Its blade is Cera-Titan, a proprietary method that adds small amounts of silver and very hard ceramic to the titanium in order to produce a knife that can hold a very sharp edge a long time. Blades made of Cera-Titan are 40% lighter than if they had been made of steel. They're also more flexible and will not rust.
Some knife blades are made completely of ceramic. Boker's Delta Knife, which I mentioned in a previous blog about knife handle materials, is a prime example. This is not the same ceramic used for pottery. In fact, the ceramic used in Boker's knife is actually zircon-oxide. You might recognize its common name - "zirconia." It's almost as hard as a diamond, is wear-resistant and stays sharper longer than steel. It's also stainless and won't rust.
Copyright 2005-2006 by Cheaper Than Dirt. Reprinted with permission
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