Annealing treatment of seamless steel pipe

Annealing treatment of seamless steel pipe

Annealing treatment is an important heat treatment tool in the manufacturing process of seamless steel pipe, which is often used to improve the mechanical properties of steel pipe, eliminate internal stress and improve processing performance. Annealing can eliminate certain defects caused by hot working of steel, or prepare for later cutting and final heat treatment. The following is a detailed description of the seamless steel pipe annealing treatment.

Purpose of annealing treatment

1. Reduce hardness and improve plasticity
Annealing can soften the material, making it easier to subsequent molding or processing, while improving the toughness of the steel pipe and reducing the risk of fracture.
2. Uniform organizational structure
Annealing helps to refine grain, homogenize metal structure and improve mechanical properties of materials.
3. Remove internal stress
In the manufacturing and processing process, seamless steel pipes will produce internal stress, which may lead to deformation or cracking. Annealing can eliminate these stresses by slowly heating and cooling, improving the stability of the structure.
4. Improve corrosion resistance
By annealing, the residual stress and non-uniformity in the material can be reduced, the corrosion resistance can be enhanced, and the service life of the steel pipe can be extended.

Type of annealing process

1. Complete annealing
(1) Concept: Complete annealing is a heat treatment process for hypoeutectoid steel (carbon content of 0.3% to 0.6%). 
(2) Objective: refine grain, improve toughness and plasticity, reduce hardness, improve cutting ability, suitable for casting, welding, forging and rolling parts of medium carbon steel and medium carbon alloy steel.

2. Stress relief annealing
(1) Concept: In order to eliminate the stress caused by plastic deformation, welding, etc., and the residual stress in the casting, the annealing is called stress relief annealing.
(2) Purpose: to eliminate the residual stress in casting, forging, welding parts, cold stamping parts and machining parts, so that the size of steel parts is stable, reduce distortion and prevent cracking.

3. Spheroidizing annealing
(1) Concept: The annealing process of spheroidizing carbide in steel is called spheroidizing annealing.
(2) Objective: To spheroidize carbide particles and improve the cutting performance and plasticity of the material. Mainly used in hypereutectoid steel, cutting tools, measuring tools, molds and so on.

4. Diffusion annealing
(1) Concept: The alloy ingot or casting is heated to 150 ~ 200 ° C above Ac3, and slowly cooled for 10 ~ 15h to eliminate the uneven heat treatment process.

(2) Objective: To eliminate dendrite segregation during crystallization and homogenize the composition.

Advantages of annealing treatment

1. Improve processing performance
2. Extend service life
3. Improve material uniformity
4. Adapt to various application scenarios

Conclusion

Annealing of seamless steel pipes is an indispensable process that extends product life and reduces the risk of use by optimizing material properties. Whether it is to eliminate internal stress, improve plasticity or improve workability, annealing can significantly enhance the suitability of seamless steel pipes in complex industrial environments.