The purpose of seamless pipe annealing

The purpose of seamless pipe annealing

General principles of annealing:

When the steel pipe is heated, recovery and recrystallization processes will occur. The driving force is the cold deformation energy storage, that is, the free energy increase after cold deformation. When heated, the metal's organizational structure will transform to an equilibrium state. The heat treatment that transforms a cold-deformed metal into an equilibrium state is called annealing.

When the annealing temperature is low and the annealing time is short, the main process that occurs in cold deformed metal is recovery.

Starting from a certain temperature, the cold deformation microstructure changes significantly, and new grains can be observed under an optical microscope with a moderate magnification. This phenomenon is called recrystallization.

After the recrystallized grains are formed, if the holding time is continued to be extended or the heating temperature is increased, the recrystallized grains will become coarser.

The purpose of seamless pipe annealing

1. Eliminate internal stress of seamless pipes

In the process of producing seamless pipes, due to the influence of forging, extrusion, perforation and other processes, a certain amount of stress will accumulate inside the seamless pipes. If left untreated, these stresses will cause the strength and toughness of seamless pipes to decrease, and may even cause problems such as cracks and deformation. Seamless pipe annealing can make the internal temperature of the pipe uniform, achieve a relaxation effect, eliminate internal stress, thereby improving the quality of seamless pipes.

2. Improve mechanical properties

Seamless pipe annealing is a heat treatment process that improves the mechanical properties of seamless pipes through the process of heating and rapid cooling at a certain temperature. Through annealing, the crystal structure of the seamless pipe is rearranged, the grain size becomes larger, and carbides and non-metallic inclusions are dispersed. These changes can improve the mechanical properties such as hardness, toughness and strength of seamless pipes, improve the service life and stability of seamless pipes, and reduce the possibility of failure problems.

3. Improve corrosion resistance

Seamless pipes are easily corroded by the external environment during use, affecting their service life and function. Seamless pipe annealing can improve the corrosion resistance of seamless pipes to a certain extent. This is because annealing can restore the pipe surface to its original uniform state, eliminate internal stress and defects on the surface, improve its surface quality, and thus improve the corrosion resistance of seamless pipes.

To sum up, seamless pipe annealing is an important heat treatment process, which can eliminate the internal stress of seamless pipes, improve mechanical properties and improve corrosion resistance. These advantages help improve the quality and service life of seamless pipes.