Sharpness is a main feature of a knife but does its quality depend only on our superior sharpening skills? No. Steel itself determines the quality characteristics of the blade; elasticity, toughness and corrosion resistance. While choosing a knife of any purpose, it is important to consider the material of the blade, so it is important to know what properties the steel grade has.

Steel is a mix of iron and carbon. Let’s see what is the difference between carbon and alloy steels.

Carbon steel

- High-carbon steels with carbon level starting from 1% and ranges from 1.5%  to 2%

- Medium carbon steels with carbon level starting from 0.7% and ranges from 0.7% to 0.9%

These steels can be easily heat treated, have a wide thermal range of heating. Could be easily machined and sharpened in a non-hardened state (filing, drilling, grinding). Carbon steel blades due to the fine-grained structure of iron carbides can be very sharp. But with all the advantages also there are some weak points. The steel does not have corrosion resistance. The rust appearance can be prevented by polishing and thorough care, but even this is not enough to prevent the formation of plaque and stains during the contact with acids.

Alloy steels

Alloying - the addition of impurities to the composition of materials to change the physical and / or chemical properties of the knife.

The most versatile material for making knives is alloy tool steel. It has a resistance to corrosion (with a chromium content above 1 3%) hardness and the ability to maintain cutting qualities.

Let’s see what alloying elements should be added to iron and what properties can it give?

- Carbon gives the steel rigidity and, together with iron and other elements, forms carbides - extremely hard metal-carbon compounds.

- Manganese gives the material of the blades a granular structure, which maintains strength of the knife or tool made of steel.

- Silicon, as well as manganese, is used during forging to give strength to the blade.

- Vanadium, like tantalum, nickel, molybdenum, cobalt and tungsten, increases the wear resistance and stiffness of steel.

All alloyed quality steels are marked with numbers and letters, the two-digit numbers given at the beginning of the grade indicate the average carbon content in hundredths of a percent, the letters to the right of the numbers indicate the alloying element.

The absence of numbers after letters indicating alloying elements indicates a content of less than 1-1.5%

For example: 9Cr18MoV - contains 0.9-0.95% carbon, 18% chromium, molybdenum 0.1-0.2%, vanadium - 0.1-0.2%

But the name of steel does not always contain a manufacturing formula, for example: Elmax - ultra-pure, chromium-molybdenum-vanadium powder stainless tool steel manufactured by Böhler - Uddeholm AG (Böhler Uddeholm AG).

Bulat

To understand what kind of steel it is, it is necessary to consider all aspects of this special production. The material is an alloy of iron and carbon, the content of the latter is about 2%, which allows the product to maintain the elasticity of steel with a hardness comparable to the characteristics of cast iron. There are several types of bulat steel. 

Let’s consider three of them created by Igor Yuryevich Pampuha.

Carbon bulat - this bulat steel is closer to the rest of the bulat steel than the classic ancient Asian bulat steel. Carbon bulat is still the most unpredictable in drawing. Blade of such steel will hold sharpening well, but will require care, because it shows poor corrosion resistance.

Stainless steel bulat - a knife from stainless steel bulat, it is an elite hunting knife. By the density of the metal, this is the most dense bulat. It is very difficult to forge.The stainless bar of bulat steel gives two times less blades than alloyed. Even in the tempered state, stainless steel bulat is practically impossible to drill, even with carbide drills. The percentage of alloying elements in stainless bulat steel is greater than in other bulat steel; the percentage of carbon in stainless bulat steel is also higher. Stainless steel bulat is not in the full-term stainless steel. The blade is practically not afraid of water, but blood, dirt and products containing acid, during prolonged contact with the blade, can leave marks on it in the form of dark spots or a slight rust deposit. We also do not recommend storing the knife for a long time in a wet sheats- black dots may appear on the blade. The blade of stainless bulat steel holds sharpening perfectly.

Two-phase bulat steel - obtained by increasing the cooling time. In this mode, carbon is distributed evenly over the bar, grain crystallization increases, the structure becomes larger. Alloying elements in this mode are connected, there is a complete diffusion of the metal between the elements that do not have time to mix due to temperature and cooling time ("different metal") whose macrostructure resembles the "Milky Way". Bulat steel is obtained with a more pronounced granular structure of diverse nature, which gives an increased aggressive cut on the cutting edge and a more viscous matrix in the body of the blade, which contributes to the ductility and viscosity of the metal. With proper forging and heat treatment, such metal obtains hardness of 63-64HRC with a high viscous matrix and increased wear resistance of the cutting edge.

It is worth saying that bulat steel remains one of the best materials for making blades, such products, in addition to qualitative properties, have decent aesthetic qualities.

Also we should say some words about the difference between Bulat and Damask steel. The main differences between that two alloys are shown in the chart below

  Main differences between Bulat and Damask steel

 

Bulat steel

Damask steel

Technology

Welding

Forging

Pattern

Chaotic (appears during crystallization)

Strict geometric (due to the skill of the Blacksmith, appears during forging)

Elasticity

Very high

Differs, depends of the materials

Compound

Iron, carbon (+/-1,9)

Steel with different carbon content--

Choosing the material knife made of, you should consider its purpose. For example the souvenir knife can be made of damask steel, but the EDC knife should be made from the steel with high resistance to mechanical and other influences.







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