Annealing vs Normalizing: Difference Between CNC Machining

Last Updated on November 13, 2023 by assistant


In the field of CNC machining, understanding the various heat treatment processes can greatly affect the quality and performance of machined parts. During heat treatment, two techniques often used are annealing and normalizing. While both methods involve the heating and cooling of materials, they serve different purposes and offer different advantages. In this blog, we’ll take a closer look at the key differences between annealing and normalizing, illuminating their unique properties and applications.

What is annealing?

Annealing is a heat treatment process that involves heating a material to a specific temperature and then gradually cooling it to room temperature. The main purpose of annealing is to eliminate internal stress, improve plasticity, and enhance the machinability of the material. This process is commonly used on metals such as steel, copper, and aluminum.

What are the main characteristics of annealing?

1. Material softening: Annealing reduces the hardness of the material and increases the ductility of the material, making it easier to process and shape.

2. Recrystallization: The heating and slow cooling during annealing facilitate the formation of new strain-free grains in the material, eliminating any defects or irregularities.

3. Stress relief: By eliminating internal stress, annealing can minimize the risk of deformation or cracking during subsequent manufacturing processes.

4. Homogenization: Annealing ensures the uniformity of the material’s microstructure, thereby improving its overall mechanical properties.


What are the applications of annealing?

Machining: Annealing is often used in CNC machining to enhance the machinability of the material and reduce tool wear.

Restoring Ductility: Annealing can restore ductility to materials that have been cold-worked or made brittle by previous heat treatment.

What is Normalizing?

Normalizing is another heat treatment technique that involves heating a material to a temperature above its critical point and then allowing it to cool in still air. The main purpose of normalizing is to refine the material’s grain structure and achieve a more uniform distribution of properties throughout the material. This process is generally suitable for carbon steel and low alloy steel.

What are the main features of standardization?

a) Grain refinement: Normalizing promotes the formation of fine-grained structure, thereby improving the strength and toughness of the material.

b) Improved machinability: The refined grain structure produced by normalizing improves surface finish and reduces tool wear during machining.

c) Reduce internal stress: Similar to annealing, normalizing helps reduce the internal stress of the material and reduces the risk of deformation or failure.

What are the applications of normalizing?

#1 Pre-machining treatment: Normalizing is often used as a preliminary heat treatment step to optimize the machinability of the raw material before CNC machining.

#2 Structural parts: Normalizing is suitable for parts that require a balance of strength and ductility, such as gears, shafts, structural parts, etc.


What types of annealing are there?

Different types of annealing techniques are used in CNC machining, including full annealing, process annealing, and stress relief annealing. Each type of use is based on the material’s specific requirements and desired results.

What are the annealing temperatures and cooling rates?

The temperature at which annealing is performed depends on the material being processed. For example, steel is typically annealed in the temperature range of 800°C to 900°C (1472°F to 1652°F). The cooling rate during annealing is usually slow to achieve the desired softening and stress relief effects.

What equipment can be annealed?

Annealing can be performed using a variety of equipment, such as furnaces, kilns, or induction heaters. Equipment selection depends on factors such as material type, size, and throughput.

What effect does annealing have on material properties?

Annealing not only improves the machinability of the material but also affects other properties, such as hardness, ductility, conductivity, etc. It also reduces the presence of impurities and enhances the material’s response to subsequent heat treatment.

How is the normalizing temperature and cooling process performed?

Normalizing is heating a material above its critical point, usually in the range of 850°C to 950°C (1562°F to 1742°F), and then cooling it in still air. This cooling process is faster than annealing, resulting in a more refined grain structure.

What changes will occur in the microstructure caused by normalizing treatment?

Rapid cooling during normalizing creates a fine-grained microstructure that improves the material’s mechanical properties. It also helps eliminate any coarse-grained areas that may have formed during previous heat treatment or machining.

What effect does normalizing have on homogenization and stress relief?

Normalizing promotes a more even distribution of properties throughout the material, thereby reducing internal stresses. This makes the material more stable and less susceptible to deformation during subsequent processing or assembly operations.

What are the limitations of normalizing?

Normalizing is mainly suitable for steel materials and is less commonly used for non-ferrous metal materials. May not be effective for materials with complex or required alloy compositions.

In conclusion

In CNC machining, annealing and normalizing are essential heat treatment processes with unique advantages and applications. The main purpose of annealing is to improve machinability and eliminate internal stress while normalizing focuses on refining the grain structure and enhancing material properties.

In addition to this, it is also crucial to adhere to industry standards and quality control measures when performing annealing and normalizing. Therefore, it is very important to find a reliable CNC machining service provider. Ruitai has many years of machining experience in this area. The parts we produce ensure consistency, and reliability and meet customer requirements.

On the other hand, the choice of heat treatment process, including annealing and normalizing, depends on factors such as material type, required material properties, and the intended application of the machined part. If you have any specific questions or need more information, please feel free to contact us.