Material Elements, Compositions and Properties of
Forged Steel for Barber and Styling Scissors

When you take iron and add a specific amount of carbon, you can then harden the iron. In other words, steel is hard enable carbonated iron. The degree of hard inability depends on the amount of carbon added to the mix.

In a simplified explanation, iron forms into a crystalline structure that looks like a bunch of cubes (cells) stacked on top of each other. During the heat treatment of a steel, when the temperature is above 1340 degrees Fahrenheit, there is an iron atom at each corner of the cube and one in the middle of each side of the cube. This type of iron structure is known as a face-centered crystal or AUSTENITE IRON. In the face-centered cubic lattice, a relatively large interstice, or "hole", exists in the center of the cube or cell. When carbon is present in the Austenite iron, the extremely small carbon atom slips into the hole of this iron cell. Then when the steel is quenched (cooled rapidly in oil or water) to room temperature, the iron crystal cell shifts it's structure to a more stable body centered crystal, also known as FERRITE IRON.

In Ferrite Iron, there is an iron atom at each corner of the cube and one in the middle of the box. Unfortunately, the carbon is too big to fit comfortably into the open spaces left in the center of the box and is forced out into one of the small interstices (holes) left between the Iron atoms. Now the iron structure is always under tension, because the carbon atoms are trapped as an atomic dispersion in its interstices, and thus the iron lattice becomes hard and brittle. This is similar to a fully filled balloon under tension being harder than a half filled balloon, which is tougher and softer.

Because of the small amount of space available, even for the small carbon atom, the solubility of carbon in Ferrite (room temperature structure) is very low (less than 1 carbon per 1000 iron atoms). At high temperatures, the maximum solubility of carbon in Austenite iron is only 2.11%. So by definition, steels contain less than 1.2% carbon, so that the carbon can dissolve completely in Austenite at high temperatures

Material Elements, Compositions and Properties

What make steel hard?

To hard the steel we add a specific amount of carbon. The more carbon u adds the harder steel gets.

For interpretation, iron is a bunch of cubes stacked on top of each other as crystalline structure. Face-centered crystal or AUSTENITE IRON happened when the heat treatment is above 1340 degrees Fahrenheit, which means an iron atom at each corner of the cube and one in the middle of each side of the cube. And a large gap exists in the center of the cube. The extremely small carbon atom slips into the hole of this iron cell when carbon is present. FERRITE IRON is made when the iron crystal cell shifts its structure to a more stable body centered crystal while cooling the steel in to room temperature in water or oil.

The carbon is too big to fit comfortably into the open spaces left in the center of iron lattice in Ferrite Iron because there is an iron atom at each corner of the cube and one in the middle of the lattice. The carbon atoms are trapped as an atomic dispersion in its interstices so the iron structure is always under tension although it's hard and brittle.

Less than 1 carbon per 1000 iron atoms in room temperature structure, the maximum solubility of carbon in Austenite iron is only 2.11% in higher temperature. so the carbon can dissolve completely.