Advantages and disadvantages of thermal expansion seamless steel pipe

Thermal expansion seamless steel pipes are widely used in various industries due to their ability to withstand extreme pressure and temperature conditions. However, the thermal expansion process introduces both benefits and limitations that affect the overall performance of the pipes. Understanding these aspects is crucial for selecting the right material for specific applications.

Advantages of Thermal Expansion Seamless Steel Pipe

Thermal expansion improves the internal structure and mechanical properties of steel pipes. The process refines the grain size, eliminates defects in the microstructure, and makes the pipe more compact. This enhances the overall strength and durability, particularly in the rolling direction, providing improved isotropic properties. Additionally, during the high-temperature, high-pressure expansion, any bubbles, cracks, or porosity formed during the casting process are welded, further increasing the pipe’s reliability and uniformity.

Disadvantages of Thermal Expansion Seamless Steel Pipe

- Delamination Due to Non-Metallic Inclusions
During thermal expansion, non-metallic inclusions such as sulfides, oxides, and silicates are pressed into thin layers within the pipe, which can lead to delamination. This weakens the tensile strength of the pipe, particularly in the thickness direction. Delamination can be problematic during welding, as the stress from weld shrinkage can cause interlaminar tearing. The strain from welding is often significantly higher than that caused by standard loading, making this a critical issue in structural applications.

- Residual Stress from Uneven Cooling
Residual stress occurs when the pipe cools unevenly after the thermal expansion process. This self-equilibrating internal stress, while not caused by external forces, exists in all cross-sectional areas of the pipe and can be more significant in pipes with larger sections. While residual stress is balanced internally, it can affect the pipe's behavior under load, potentially leading to deformation, reduced fatigue resistance, and other performance issues.