Primary Facts about Heat Treating Carbon Steels

23 March 2023

Metals, in general, are materials that can be prepared, polished, or fractured to showcase a lustrous appearance. They can also be processed further to alter their physical properties such as strength, ductility, malleability, and conductivity to electricity and heat.

Many types of metals can be maximised by various industries. One of these metals is carbon steel. Carbon steel, also called mild steel, is a steel integrated with carbon, iron, and other elements. It is often used in buildings, bridges, shafts, rails, pipelines, cars, fridges, and washing machines. It can even be utilised in making blades, cutting tools, punches, and dies.

But before industries can utilise carbon steels in making various parts and products, these materials should undergo heat treatment techniques first.

The Basics of Heat Treatment

Heat treatment manipulates the molecular structure of a metal and changes its properties. This process can either increase or decrease the ductility, toughness, hardness, and yield strength of metal without changing its electrical and thermal conductivity. Generally, heat treatment has four states. These states are annealing, normalising, hardening, and tempering.

Annealing is responsible for altering the physical and chemical properties of a metal. It ensures that the ductility of a material will increase while its hardness is reduced to make it more workable. Normalising, alternatively, removes impurities and improves the ductility and toughness of a metal workpiece. It is done by heating the material between 750-980°C.

Hardening is another heat treatment state that metals can undergo. It also involves heating the material to a high temperature, holding it at a certain temperature for one hour per inch of thickness, and cooling the material quickly. Its goal is to make the material boast a harder, stronger structure. Tempering, ultimately, enhances the toughness of metals so they can hold up during subsequent processing. It is done by heating the metals to a high temperature below their melting point and cooling them in the air.

Heat Treating Carbon Steels

Carbon steels, fortunately, are easy to process as their molecular structure is crystalline. Hence, they can undergo a heat treatment process to alter their properties. These metals can be exposed to various ranges of specific temperatures for a specific amount of time. Once exposed to various temperatures, their structure is expected to change, altering their shape or phase.

As experts hold or soak the carbon steels in hot and cool temperatures, the shape of their crystalline structure will further change.

Now, carbon steels can contain several phases, exhibiting their own set of properties. These phases include austenite, ferrite, cementite, banite, martensite, and pearlite. These phases can make carbon steels softer, harder, or tougher, making them highly recommended for a wide range of industrial applications.

But to make heat treatment successful, carbon steels should be oil quenched. Using water, after all, may only produce cracks in the workpieces. It is also important to take note that their carbon content can dictate the speed of their quench. The lower the carbon, the faster and more aggressive their quench must be. To know more about heat-treating carbon steels, you can contact us at Alpha Detroit Heat Treatment.

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