Because of its excellent corrosion resistance, strength and aesthetics, stainless steel pipes are widely used in chemical industry, food processing, building decoration, medical equipment and other fields. However, in the process of cold processing (such as cold rolling, cold drawing, welding), the internal stainless steel pipe is prone to residual stress, work hardening or uneven microstructure, which may lead to deformation, cracking or decreased corrosion resistance. As a key heat treatment process, annealing can effectively solve these problems, restore material properties and improve finished product quality.

Effect and principle of annealing
Residual stress relief
There is residual stress inside stainless steel pipes after cold working or welding, and annealing releases the stress through heating and slow cooling to prevent deformation or cracking in subsequent use.

Improved workability
Annealing can reduce the hardness of the material, improve the ductility, and facilitate further processing (such as bending, flaring).

Optimize microstructure
By recrystallization or carbide dissolution, fine grain, uniform structure, improve corrosion resistance and mechanical properties.

Restore corrosion resistance
Cold working may lead to the destruction of passivation film on stainless steel surface, and annealing can promote the regeneration of passivation film and enhance the corrosion resistance.

Principle of annealing:
Annealing By heating the stainless steel tube above the critical temperature (such as austenitizing temperature), holding for a certain period of time and slowly cooling, so that the atom diffusion recombination, eliminate lattice distortion, and achieve organizational homogenization.

In stainless steel annealing, the pipe will be heated to 1050℃, the role is to eliminate work hardening, restore plasticity; Eliminate residual stress and prevent deformation; Dissolve carbide, improve corrosion resistance; Refine grain and improve ductility.

Application scenario of annealing process
Repair after cold processing: the stainless steel pipe after cold drawing and cold rolling needs to be annealed to restore plasticity.
Post-welding treatment: eliminate residual stress in the weld area to prevent stress corrosion cracking.
Precision tube preparation: Tubes for medical instruments and instruments need to be annealed to ensure dimensional stability.
Corrosion resistance upgrade: chemical pipeline annealing passivation treatment, extend the service life.

The stainless steel pipe annealing equipment developed by Hangao Technology occupies a leading position in the industry, leads the development direction and trend of the industry, and has won the trust and support of our customers.

Related: stainless steel pipe production line, high-speed welded steel pipe production line

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