Kolstål för knivar och rakblad - Sollex blogg

Carbon steel

for knives and razor blades

Johan Falk

Carbon steel for knives and razor blades

The number one ingredient to produce high quality blades and razor blades is high-quality material. Sollex manufactures knives, industrial razor blades and tools in the following materials: carbon steel, stainless steel, Bi-metal, high-speed steel, tool steel, ceramic materials, solid tungsten carbide and cemented carbide.

Extensive knowledge and experience of production, hardening and grinding results in industrial razor blades with sharpness and durability. Sollex blades have real sharpness and durability due to high-quality materials, proven and quality-assured hardening and precision grinding.

Blades in carbon steel

Carbon steel is mainly an alloy of iron and carbon. In addition to carbon, smaller amounts of silicon and manganese are usually added to the alloy. The carbon content is usually 0.01% -0.8%, silicon below 0.3% and manganese below 0.8%. If the amount of carbon increases, the steel becomes harder and stronger but also less ductile (the steel's ability to be subjected to plastic deformation without cracking). The higher the carbon content, the worse the welding properties.

Carbon content in carbon steel

Blades are made of different carbon steels due to different characteristics. The cutting characteristics is directly related to the carbon steel used. Many people talk about carbon content. In practice, this means a carbon content between 0.5 and 1%. The "eutectic" point for high carbon content is 0.76% and everything above is called high carbon. Carbon content higher than 2.1% causes carbon to crystallize to iron carbide or cast iron. Excessively high carbon content is thus unusable for making knives and razor blades.

Optimal carbon steel for industrial razor blades

Sollex blades are, unless otherwise stated, made of carbon steel. We can manufacture blades and razor blades in a variety of carbon steels (or with a variety of DIN codes) but have a favorite steel with a very high carbon and chromium content. Adding chromium to the steel protects the steel from rust. The carbon steel used in Sollex blades is 95% made in Germany. Over the years, Germany has developed a particularly high level of competence and quality in the production of carbon steels with a high carbon and chromium content. Compared with cheaper steel German carbon steel performs better due to steel structure and the microstructure is more refined.

Hardening blades in carbon steel

The starting point for Sollex blades is a narrow cold-rolled carbon steel on a roll. We manufacture our carbon steel blades in Germany, where we have refined the technology and can ice-harden the carbon steel to perfection.

When Sollex blades are hardened, the steel is heated to a high temperature. Then it cools down quickly (ice hardening). Afterwards the steel is heated again to remove stress from the steel. The exact hardening temperatures we use to make Sollex blades are a well-kept secret. The important thing is that we always have the same process and temperatures over time. When Sollex carbon steel blades are hardened, they have a constant and even hardness for optimal cutting work. Sollex blades made in such carbon steel can be extremely sharpened or given long durability.

Production process blades in carbon steel

We start with high quality carbon steel from Germany. Step one is that the carbon steel is rolled. Then we punch out the shape of the blade. During normal production, 600 punches are made per minute, which gives 1200 blades. Step three is to harden the steel which in German we call ”Eishardening” (German for our hardening process). The steel is then reheated to remove stress from the steel. The next step is marking and in some cases we do a surface treatment to protect our blades from rust. For industrial razor blades, this process is called oxidation. But in some cases we also choose to paint the blades to protect the carbon steel from rust. Now to Sollex's specialist competence: precision grinding. This is followed by us doing a second polishing to remove all possible burr from the grinding. At this stage the blade is finished.

Rust on carbon steel blades

Carbon steel rusts. So the blade needs to be lubricated. Well-oiled blades, on the other hand, can avoid rust for many years. But sooner or later, all steels rust. What you as a user can do to protect your blades from rust is to keep them well oiled and protect them from being exposed to oxygen. In addition, store the carbon steel blades in a dry place in a tightly closed package where the carbon steel blades are exposed to as little oxygen as possible. In Sollex stock we keep many blades well-oiled and in vacuum. 

Read more about how to prevent corrosion of industrial knives and blades in our other blog post.

Characteristics and advantages of carbon steel

Why is carbon steel used? An advantage of carbon steel is that it is easy to grind. Another advantage is that a blade in carbon steel can be sharpened sharper compared to stainless steel. The properties of the steel are evaluated in the form of hardness, toughness, wear resistance and edge sharpness. The blade should be hard enough to cut through the material. But not too hard as the blade toughness is lost. In such case the steel cracks or breaks. The resistance and edge sharpness gives the blade its cutting properties and durability.

Steel hardness is measured on a scale called Rockwell C or paraphrased HRC. The harder a steel is, the sharper it can be grinded. But a cutting edge in hard steel is more sensitive to deformation as the risk of chips being knocked out from the edge. A cutting edge in lower hardness can not be as sharp but on the other hand more durable. Knife and razor blade steels with HRC between 56 and 58 are called medium hard. HRC from 62 to 65 is called extremely hard. Sollex blades in carbon steel are in this definition extremely hard.





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