Edge retention

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Of the cutting edge is meant the resistance of the cutting edge of a knife or other cutting tool to wear by mechanical, thermal and chemical influences. Edge retention describes how long a blade remains sharp over a certain period of use and under certain conditions of use.

Influencing variables

The aspect of the edge retention of a knife blade is a much discussed topic. Almost every time you buy a knife, the question of this property is raised. From a technical point of view, the fundamental influencing factors that have a decisive influence on the edge retention of a blade are linked in a variety of ways and in a complex manner.

The edge retention of blades made of different materials depends on the one hand on the material and its mechanical-chemical properties, the type of cut, i.e. whether z. B. a pulling cut or pressing cut is present, and the cut material to be cut (e.g. meat, vegetables, wood, leather) that is to be cut.

In the case of hand knives, i.e. knives for everyday use, the behavior of the user himself should be mentioned above all, which is decisive for the edge retention of a blade . If handled improperly or in a different way, for example when cans are opened or cut on ceramic plates, a cutting edge wears out quickly or is even destroyed.

Another crucial aspect is in steel materials of the heat treatment to. If this is done improperly, even the best alloys will not be able to offer good edge retention.

Finally, the edge retention depends on the geometry of the cutting edge (cutting edge angle, absence of burrs) itself. With suitable materials, thin cutting edges and acute angles on the cutting edge guarantee high cutting ability and edge retention at a high level of sharpness and quality.

However, if the steel is unsuitable for cutting edge geometries that are easy to cut, such as the very highly alloyed, wear-resistant powder metallurgical steels or ceramics, then a blade loses its cutting ability particularly quickly.

Influence of the materials

From the point of view of materials engineering, the following relationships are known: Classic single-alloy steels such as carbon steels (German material number / AISI e.g. 1.2842 = 02; 1.2510 = O1; 100Cr6 = 52100) with low levels of other alloying elements ( chromium , vanadium , tungsten , Manganese , niobium ) are more wear-resistant and highly alloyed materials, especially in the pressing cut, such as B. the modern powder metallurgical steels, far superior.

Blades made of the simpler carbon steels usually have a higher toughness and stability of the cutting edge with higher hardness values. In addition, the carbide compounds, which are almost always present in such steels, are much smaller in size and fewer in number than the carbides in higher-alloyed and therefore more wear-resistant steels. In short, the simple alloy steel is "fine-grained". The cutting edge can therefore be ground thinner, finer and at a more acute angle on the cutting edge. Compared to blades made of higher alloyed materials, this leads to a significantly better cutting ability and higher sharpness. The carbon steel blades are also easier to sharpen. The disadvantage is the susceptibility to corrosion , but this is limited if handled correctly. Usually only a gray patina forms, but it is completely harmless. For basic care, it is therefore best to wipe the knives with a damp cloth, then with a dry cloth. Furthermore, the following applies: “No dishwasher!” And only brief contact with washing-up water, otherwise there is a risk that the cutting edge will quickly lose its sharpness due to corrosion on the cutting edge.

Wear-resistant materials (German material number / AISI e.g. 1.2379 = D2; 1.4125 = 440C; CPM S30V ; etc.) are more suitable for the pulling cut due to their mostly coarse material structure (many or large and coarse carbides), its quality level is significantly less than that of the pressing cut. Nevertheless, these materials can of course be used for knives and are also used. A typical and also useful field of application are the classic hunting knives . Animal skins, which are often heavily soiled with sand and soil, have a very abrasive effect on the cutting edge of blades. The large number of carbides helps to maintain a moderately sharp but long-lasting open cutting edge in the pulling cut.

The mechanism here is that the highly alloyed materials offer a rather “open”, rough cutting edge due to the increasing number of fragments of fine particles on the cutting edge. After a short time, the cutting edge resembles a microsaw, which then stabilizes at a moderate level of sharpness and quality. Many users consider this level to be sufficient; This also explains the feeling of long edge retention of blades made of high-alloy materials. An additional disadvantage of these materials is that blades made from them are relatively difficult to sharpen and only accept rough edges with rough angles in a stable manner.

literature

  • Roman Landes: Knife Blades and Steel: Technological Consideration of Knife Edges. Wieland, 2nd edition, ISBN 3-938711-04-3