During the production of stainless steel electrolytic tubes, processes such as cutting, bending, and welding can easily generate residual stress inside the pipe. If this stress is not eliminated in time, it will gradually release during subsequent processing or use, leading to pipe deformation, cracking, and even stress corrosion cracking, seriously affecting the safety and reliability of the pipeline system. Therefore, eliminating internal stress is a critical step in the production of stainless steel electrolytic tubes and must be achieved through scientifically sound processes.
Natural aging is a traditional and simple stress relief method. Its principle is to place the processed stainless steel electrolytic tube in a natural environment, utilizing the time effect to slowly release the internal stress. This method requires no additional equipment and has low cost, but the processing cycle is long, usually requiring months or even years, and the effect is greatly affected by environmental factors such as temperature and humidity, making it difficult to meet the needs of large-scale industrial production. Therefore, natural aging is more suitable for applications with low production cycle requirements and low stress levels.
Thermal aging is currently the most widely used stress relief method. The core of thermal aging is to enhance the atomic mobility within the pipe and rearrange the grains through controlled process parameters such as heating, heat preservation, and cooling, thereby eliminating or reducing residual stress. In practice, the stainless steel electrolytic tube needs to be heated to a specific temperature range, typically within the tempering temperature range of stainless steel pipes, and held for a certain period to allow for full stress release. It is then slowly cooled to avoid creating new stress due to sudden temperature changes. Thermal aging is highly effective in reducing residual stress in the pipe, improving dimensional stability and mechanical properties, and is particularly suitable for the production of stainless steel electrolytic tubes with high precision requirements.
Vibration aging is an emerging stress relief technology. Its principle is to apply periodic alternating stress to the pipe using vibration equipment, causing minute plastic deformation and promoting the relaxation and redistribution of internal residual stress. Compared to thermal aging, vibration aging has advantages such as shorter processing time, lower energy consumption, and no oxidation problems, and it does not change the material and properties of the pipe. However, the effectiveness of vibration aging is greatly affected by factors such as the shape and size of the pipe and vibration parameters, requiring operation and parameter adjustment by professional technicians to ensure the treatment effect. Despite this, vibration aging is gradually being adopted in the production of stainless steel electrolytic tubes due to its high efficiency and environmental friendliness.
Mechanical tension or compression methods are suitable for stainless steel electrolytic tubes of specific shapes. External force is applied to the tube using tension or compression equipment, causing plastic deformation and thus altering the internal stress state. This method allows for precise control of stress relief and is suitable for applications requiring high dimensional accuracy. However, mechanical tension or compression requires specialized equipment and fixtures, making the process relatively complex. Furthermore, for tubes with complex shapes or thin walls, stress concentration can lead to deformation or damage, thus limiting its application.
Solution treatment is an indispensable process in the production of stainless steel electrolytic tubes. Its principle is to fully dissolve carbides at high temperatures, followed by rapid cooling, fixing the low-stress structure and preventing stress re-accumulation. Solution treatment not only eliminates internal stresses generated during cold working and welding but also improves the uniformity of the tube's microstructure, enhancing corrosion resistance and processing performance. For stainless steel pipes requiring pickling, passivation, and electropolishing, solution treatment is a necessary preliminary step to ensure uniform surface structure, form a complete passivation film, and further enhance corrosion resistance.
In actual production, stress relief methods for stainless steel electrolytic tubes must be selected comprehensively based on factors such as pipe material, specifications, processing technology, and usage requirements. For pipes with high stress levels and strict precision requirements, a combination of thermal aging and solution treatment can be used; for regularly shaped pipes produced in large batches, vibration aging is more advantageous; while mechanical tension or compression methods are suitable for stress adjustment in specific scenarios. Through a scientifically sound combination of processes, internal stress in stainless steel electrolytic tubes can be effectively eliminated, preventing deformation during use and ensuring the long-term stable operation of the pipeline system.
