Construction of knife blades

Blade Construction

Mono steel

Until 20 years ago, the vast majority of knives sold to home users were mono-steel, which means the entire blade was made of one type of steel. Even today most kitchen knives are still mono steel. But especially at the upper end of the market, blades made of more than one material are becoming increasingly popular.

Forged Damascus

Damascus blades are an ancient form of production, stemming from the necessity to combine both hardness and flexibility in swords. Thus two different steels where forged together, with the side effect of a pattern resulting from the different layers of steel in one blade.

In today’s world, producing blades that are both hard and flexible will be done by formulating steel with different alloys. This has rendered true Damascus blades obsolete, due to a lack of functional benefits against extremely high production cost.

Today, truly forged Damascus knives, where different layers of steel are stacked upon each other, with a process of forging and multiple folds, are still made by custom knife artisans or as limited editions by brand manufacturers. Due to the very time consuming production process, such knives are usually very expensive, well over $1000.

A forged Damascus knife can be distinguished from other kind of Damascus patterns by the pattern going through the cutting edge, and in some cases even extending to the bolster (forged with integral bolster).

Layered steel with Damascus look

Since historic blades in Museums had Damascus looks, and some artisans continued producing knife blades in ancient techniques, Japanese knife manufacturers got the idea of mass-producing knives with layered steel and the look of Damascus blades. There is a debate of whether such knives can be called “Damascus”. If Damascus is defined as a blade made of layered steel, those can be called Damascus. If Damascus is considered as real forged Damascus, then those are just “Damascus look”.

The layered steel is produced in steel mills, by stacking sheets of different material on top of each other, inseparably bonding them through the application of heat and pressure, hot and cold rolling them to the desired material thickness and cutting them into the desired shape. Below an illustration of the process:

Core + side material

Welding on the sides

Annealing

Acid + shot blast cleaning

Hot

rolling

Annealing

Acid + shot blast cleaning

Cold

rolling

Cutting +

Inspection

This is how a 67-layer material as supplied by the steel factory would look in a cross-section:

Core steel

Side layers

(33 each side)

In a knife factory, the material is then further processed in the following way to expose a Damascus pattern:

The layered steel is punched by a mold with indentations, thus producing ripples in the layered steel.

The steel blank is ground into a V-shape, thus exposing the layers of the steel. Without punching, the layers would show as straight lines. With punching, patterns can be produced on the blade.

3a:

Mirror finish Damascus: The entire blade is mirror finished from tip to bolster. The blade then is high-pressure shot-blasted with very fine sand beads from a pistol, which create tiny indentations on the softer layers of the material, producing a matte finish. The harder material is not affected by the sand beads and keeps a mirror finish, thus producing a contrast between shiny and matt.

3b:

Etched Damascus: The blade is dipped into an etching liquid. This liquid reacts stronger with one of the 2 blade materials than with the other, producing a contrast.

drawing of layered material in damascus steel after blade punching showing ripples in steel

All layered steels have one thing in common: they have one core material in the center, which is a knife steel. This is the layer that defines the cutting performance of the knife. Although the outer layers are largely for appearance and have no role in actual cutting, they do have a function in covering the sides of the blade. Since the outer layers are usually made of low or no-carbon steel, they are rather resistant to corrosion. In combination with a high-carbon, corrosion prone core steel, the outer layers protect the blade from staining.

Layered Damascus look steel today comes in many configurations, from 33 layers to 133, and with different material combinations that produce different contrasts and different designs.

3-layer steel

In a 3-layer set-up, layers of inexpensive, softer, corrosion resistant steel are wrapped around a core of expensive, hard or corrosive steel, for the following purposes:

Protecting a corrosive core material
Sandwiching a hard and brittle core material and prevent the blade from braking
Reducing material cost
Reducing production cost (softer material is easier to grind)

Other than multi-layered Damascus steel, 3-layer steel is produced solely for functional purposes and is most often used in combination with a core of powder steel or carbon steel.

Mono steel with Damascus look

As layered Damascus steel is expensive in both material and production cost, there is an increasing amount of knives in the market with a “fake” Damascus look. Those knives are made of a mono steel blade, with a pattern that is created by lasering or etching. This is a cheap production step, so that the cost of such knives is similar to that of mono steel knives and much cheaper than knives with true multi-layer steel.

One way to distinguish “fake” Damascus from real multi-layered steel is the pattern. If the pattern is very regular on the different blades, it’s fake, since it’s impossible to produce such regularity in patterns with real multi-layer steel.