What is knife steel?

When is steel knife steel?

Knife steel is, as the name suggests, steel from the knife are manufactured. Not every steel can be used to make knives, so knife steel must have special properties. Special requirements are placed on a knife blade, such as edge retention, cutting ability and sharpenability. In order for these requirements to be met, the steel to be used must have certain properties. The most important are hardenability, strength and, for private use, also corrosion resistance.

That is what is meant by hardenability

• Hardenability means how well the steel can be hardened. Knife steel must have good hardenability, otherwise the blade will not be strong. The hardness is given in HRC, where HR stands for "Rockwell hardness", which means something like "Rockwell hardness". In order to find out the HR, an attempt is made to penetrate as deeply into the material as possible with a test body. The C indicates which test specimen was used. The categories of the test specimens go in descending order from A-H as well as K, N and T. The steel for a blade must have at least a HRC of 55, ideally 60-65 HRC.
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• How well a steel can be hardened depends on the carbon content, but also on the types of metal used in the steel. So that steel can be hardened, it should have at least 0.2% carbon content. Does the steel have too much carbon, e.g. B. 0.6%, there may be cracks or breaks when quenching the hot steel. Certain types of metal in steel can even completely prevent hardening, such as too high a nickel content.

What is strength about?

• The strength of a knife is important in order for it to have good cut resistance. It indicates how elastic and tough a blade is. A high level of strength is achieved when the hardening creates a fine structure. Microstructure simply means the microstructure of the steel, which can be changed by heating and cooling during forging.

• In this case, the structure consists of the hardening structure (martensite) and the fine grain. Roughly speaking, the hardening structure determines how hard the blade is and the fine grain how elastic it is. A blade steel is optimal if it is heated, compressed (e.g. B. with hammer blows) and cooling down again, a good hardening structure is obtained. At the same time, these processes produce carbides, which determine the fine grain size. Carbides are compounds with carbon that combine with other elements of steel. This is why the carbon content in steel is so crucial.


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That is why steel has to be corrosion-resistant

• The corrosion resistance of the steel is important for light everyday use. So that you can use a knife e.g. B. Can be cleaned in the dishwasher, it must have corrosion protection. This is achieved by using a steel to which chromium and molybdenum have been added. It is important that the steel still contains at least 12% chromium after the forging process, otherwise there is no protection against corrosion.

• The disadvantage of rust protection is that a steel with added chromium and molybdenum in large quantities is not well suited for hardening. The microstructure of the steel becomes too coarse and neither an optimal hardness nor a good strength can be achieved. Therefore, knives with rust protection are usually only made for private households. In professional kitchens you will mostly find knives without corrosion protection, as they are simply sharper and harder. The disadvantage of these high quality knives is the maintenance they require.