What is steel normalizing? Normalization is a heat treatment method, mainly used to improve the toughness of steel. By heating steel members to After keeping the temperature above Ac3 for a period of time, the crystal grains of the steel will be refined in a fast cooling process, thus improving the strength and obviously increasing the toughness. Normalizing treatment can significantly reduce the cracking tendency of components, and greatly improve the comprehensive mechanical properties and cutting properties of low-alloy steel plates, forgings and castings.

1、 Definition of normalizing

Normalizing is a heat treatment process that the workpiece is heated and austenitized, and then cooled in static air or protective atmosphere for a certain time to make it become pearlite.

2、 Normalizing process

The normalizing temperature range is 30-50 ℃ above Ac3 temperature. After holding for a period of time, take the workpiece out of the furnace and cool it in the air or by spraying, spraying or blowing. The cooling rate of normalizing is slightly faster than that of annealing, which makes the structure of steel thinner, thus improving the mechanical properties. Compared with annealing, the production efficiency of normalizing is higher, so normalizing is often used instead of annealing in production. For important forgings with complex shapes, high temperature tempering is usually required to eliminate the stress caused by normalizing cooling and improve toughness and plasticity.

3、 Purpose of normalizing

1. Remove the stress inside the material.

2. Adjust the hardness of the material (usually increase), slightly reduce the plasticity, and prepare for subsequent processing. Similar to annealing, but aimed at improving efficiency and reducing cost.

4、 Application range of normalizing

1. For low-carbon steel, the hardness after normalizing is slightly higher than that after annealing, and it has good toughness, which is suitable for pretreatment of cutting.

2. Medium carbon steel can be normalized instead of quenching and tempering treatment, and can also be used as pretreatment before surface quenching by induction heating.

3. Normalization of tool steel, bearing steel and carburized steel can eliminate or inhibit the formation of network carbide, so as to obtain a good structure for spheroidizing annealing.

4. For steel castings, normalizing treatment can refine as cast structure and improve cutting performance.

5. Normalizing is applicable to the final heat treatment of large forgings to avoid the tendency of cracking.

6. Normalizing can improve the hardness, strength and wear resistance of nodular cast iron. It is suitable for manufacturing important parts, such as crankshafts and connecting rods of automobiles, tractors and diesel engines.

7. For hypereutectoid steel, the network secondary cementite can be eliminated by once normalizing treatment to ensure that all cementite is spheroidized during spheroidizing annealing.

5、 Difference between normalizing and annealing

1. The cooling rate of normalizing is faster than that of annealing, and the pearlite structure obtained has smaller lamellar spacing and thinner structure, so it is also called normalization treatment. For example, for steels with carbon content less than 0.4%, normalizing can be used instead of full annealing.

2. Compared with full annealing, normalizing can obtain higher strength and hardness.

3. Normalizing is widely used because of its short production cycle, high equipment utilization, energy saving and low cost.

6、 Advantages and benefits of normalizing

1. Enhance strength and hardness.

2. Improve toughness and reduce the risk of cracking.

3. Improve cutting performance and enhance machining efficiency.

4. Improve stability and consistency.

5. Simplify process and save cost.

6. Expand the scope of application.