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Heat Treating Overview

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If you are working in a shop of facility as a machinist, you will no doubt be handling steel and other types of metal. This is especially true if you are a tool and die maker. The idea is to take the metal and put it in a machine to harden the metal to a certain texture and toughness. This whole procedure is known as heat treating. Many different types of materials can be heat treated including glass. Heat treatment includes using various techniques to get the process completed. These techniques include:

• Annealing (Metallurgy): This is a type heat treatment wherein the microstructure of the material is altered, thereby changing its properties so it becomes harder and stronger. Annealing occurs in two phases such as the recovery phase and recrystallization:
o Recovery Phase – This results when the metal becomes softened by removing all defective crystals.
o Recrystallization – This is where new grains nucleate and grow to replace deformed materials.
• Case hardening: This is also referred to as surface hardening. It is the process of hardening the surface of steel, but leaving the interior untouched. This way the item is made of two different types of steel. It helps to prevent wear resistance of the part.
• Precipitation hardening: Another name most common for this is age hardening. This is a heat treatment method used to strengthen materials like aluminum ands titanium. The process works by raising the temperature of the material to a point where the particles are affected, thereby changing the materials in such a way that it hardens.
• Tempering: Tempering is a type of heat treatment that works to toughen metals and alloys. For example, steel blades are hardened by rapidly cooling (quenching). However in many conditions, rapid cooling can cause problems so tempering has to be used to reduce this affect. In many cases, both tempering and quenching are used together to accomplish the goal of hardening the material.
• Quenching: This was stated above with tempering. Basically, quenching cools the metal down rapidly but only for a narrow period of time. For example, it can be used in certain materials like plastic to make it hard.

Next Page: What is Heat Treatment and How Is It Done?

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