Why do pressure vessels need to be heat treated after welding?

The safety of pressure vessels first depends on the selection of materials, and the performance of metal materials is not only related to their chemical composition and metallographic structure, but also closely related to the heat treatment state. Heat treatment is an important process to improve the performance of metal materials and their products. GB150 clearly stipulates the heat treatment status of various pressure vessel steel plates during their use. Such as: hot rolling state, normalizing state, tempering state, normalizing + high temperature tempering state, quenching and tempering state, solid solution state and stabilized state. The quality of the heat treatment of pressure vessels will directly affect the quality of the product.
The design of pressure vessels is based on the given working conditions and process dimensions, taking into account the requirements for manufacturing, installation and maintenance, and conducts load analysis and stress analysis on the correct selection of materials for each component of the pressure vessel. Choose a reasonable structural type and determine the strength and dimensions that are both safe, reliable, economical and reasonable. It usually works continuously for a long time under harsh operating conditions. The failure of a pressure vessel or even the damage of a part often leads to the shutdown of the entire device, which may pose a threat to the safety of property and personnel. Therefore, the long-term safety of the pressure vessel must be ensured. Operation is of great significance to process industrial production such as petrochemicals.