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Basic knowledge and function of high temperature annealing

The processing technology of steel is a technical activity. The processing of steel needs to be heat treated first. The following Haituo Electromechanical Xiaobian share the relevant technical knowledge about high temperature annealing in the heat treatment process. Let's take a look at the friends who want to master the steel processing technology. Let's go!

 


About annealing

Annealing is a metal heat treatment process in which the metal is slowly heated to a certain temperature for a sufficient period of time and then cooled at a suitable rate.

Annealing heat treatment is divided into complete annealing, incomplete annealing and stress relief annealing, diffusion annealing, spheroidizing annealing, and recrystallization annealing. The mechanical properties of the annealed material can be tested by tensile testing or by hardness testing. Many steels are supplied in an annealed heat treatment state. The hardness test of steel can be tested by Rockwell hardness tester. For thinner steel plates, steel strips and thin-walled steel pipes, surface Rockwell hardness tester can be used to test HRT hardness. Heating the steel to a certain temperature above or below the critical point Ac1, holding it for a period of time, and then slowly cooling it in a furnace or in a furnace or a medium with poor thermal conductivity to obtain a stable structure close to equilibrium. .

 



The role of high temperature annealing:

1 to improve or eliminate various structural defects and residual stress caused by steel in casting, forging, rolling and welding, to prevent deformation and cracking of the workpiece;

2 softening the workpiece for cutting processing;

3 refine the grains and improve the structure to improve the mechanical properties of the workpiece;

4 Prepare the organization for the final heat treatment (quenching, tempering).


Case description


What is the difference between the formation of spheroidizing annealing and high temperature tempering?

1. Different objects: high temperature tempering is generally used for quenching and tempering of low and medium carbon steel, as the last process of heat treatment; spheroidizing annealing is generally applied to the intermediate process of high carbon steel heat treatment, and the spheroidized structure with low hardness is obtained for subsequent machining.

2. Different processes: high temperature tempering is a treatment method of quenched martensite, in which granular cementite transforms through the ε-carbide of the flake to the cementite, and then aggregates and grows up. The carbide is small granular; spheroidizing annealing is a process of cooling or heat preservation after heating. The treatment is heated to a slightly higher temperature of A1, and then slowly cooled or kept near the temperature of AR1. Since the heating is undissolved carbide As a particle of non-uniform nucleation, its carbide growth is easier, and the difference in carbon content is larger than that of high-temperature tempering, and the carbide is generally coarser.



The above is the theoretical knowledge about the high-temperature annealing in the heat treatment process shared by Haituo Electromechanical Xiaobian. Everyone should be familiar with the above basic knowledge when learning technology.
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