In the API 5L PSL2 standard, the heat treatment state of pipeline steel plates is indicated by suffix letters, as follows:
Without letters: Indicates the rolled state, no additional heat treatment has been performed.
N (Normalized Rolled, Normalized Formed, Normalized): Normalizing is a heat treatment in which the steel is heated above the critical temperature and then air cooled. This cycle refines the grain structure, further improves strength, and improves the consistency of mechanical properties throughout the line. Normalized pipes are suitable for a wide range of applications due to their balanced strength and ductility.
Q (Tempering and Quenching): Quenching and treating involves rapidly cooling the steel from a high temperature (quenching), then heating to a lower temperature and cooling again (treating). The final product of the process is a tough, fine-grained microstructure with high strength. Quenched and tempered pipes are particularly useful in applications that require better mechanical properties and more resistance to stress than brittle fracture.
M (Thermomechanical Rolling or Forming): Thermomechanical processing combines controlled rolling and controlled cooling to achieve the desired microstructure and properties. This strategy can produce pipes with incredible strength, toughness and weldability. Thermomechanical processing is often used to produce high-strength steels with good low-temperature toughness for demanding applications in harsh environments.
The use of these suffix letters helps to distinguish pipes in different heat treatment states to ensure that they meet specific service requirements and environments.
Carbon Steel Line Pipe
