Why is Steel Heat Treated?

A technique called carbonization was discovered after the industrial revolution and is frequently used today. It is a heat treatment technique used to increase the surface properties of metals. In this technique, the metal is kept (kept) in a carbon-rich environment at a temperature where carbon elements can pass through the surface of the metal with the help of diffusion. Processing time varies depending on the desired effective hardness depth. Due to the nature of the diffusion process, carbon concentration decreases parabolically from the surface to the depth. Here, the effective hardness depth is the surface depth at which the desired minimum hardness value is achieved.
To provide a carbon-rich heating environment, carbon-rich gases are introduced into the atmosphere-controlled furnaces. An older technology is to harden the metal in molten industrial salts containing carbon.

As the hardness of the material increases, its wear resistance also increases, but at the same time, the material becomes more brittle and its durability decreases. That is, heat treatment improves some mechanical properties and worsens others. In this sense, it is essential to find the most suitable point for the usage area. During heat treatment; The desired quality material is produced by creating the most suitable conditions by controlling temperature, time and atmosphere simultaneously.

Steel and Iron

When it comes to steel and iron, one of the most important differences that determine their usage areas is the material’s ability to stretch. Iron and carbon are used in steel alloy. The raw form of iron is quite soft. When you drop a piece of raw iron from a low place, you will see it break. It is the carbon contained in steel that gives raw iron durability and hardness. 2% carbon is sufficient to increase the durability of raw iron. This ratio may change if steels with different durability and hardness are desired to be produced. For example, stainless steels require at least 11% carbon.

The carbon content of steel is not enough to prevent brittleness. Porcelains are also hard; but it is also quite fragile. The factor that increases the durability of steel by reducing its brittleness is its flexibility. Thanks to its flexibility, steel can be used for a long time without breaking. The element that gives steel its flexibility is heat treatment. Flexible steels are obtained through heat treatments applied during steel production. The fact that steel can stretch is also an important difference between it and iron. Flexibility can be a distinguishing feature when deciding whether to use iron or steel in an area. The flexibility feature makes steel more resistant to impacts. Flexibility is needed to absorb certain amounts of impact.