In the manufacturing process of petrochemical forgings, residual stress is often generated in the material due to the influence of heating, forging, cooling and other processes. These residual stresses may lead to deformation, cracking and other problems in the service of forgings, which seriously affect their service life and safety. Therefore, the removal of residual stress has become a key technical task in the manufacturing process of petrochemical forgings. This paper will introduce some common residual stress relief methods, and analyze their advantages and disadvantages, in order to provide useful reference for practical production.
The residual stress in petrochemical forgings mainly comes from the microstructure inhomogeneity inside the material and the temperature gradient during processing. During heating and cooling, the temperature changes on the surface and inside of the material are inconsistent, resulting in uneven tissue transformation, resulting in residual stress. The existence of residual stress will cause the shape and size of the forging to change, and even cause cracks, which will seriously affect the quality and performance of the forging.
Common methods for removing residual stress
Natural aging: The forging is placed in the natural environment for a long time, using the temperature change under natural conditions, so that the residual stress inside the material is gradually released. This method is simple and easy, but it takes a long time and the effect is not stable.
Artificial aging: accelerate the release of residual stress by artificially controlling the temperature and time of the forging. The commonly used methods are thermal aging and vibration aging. Thermal aging is to heat the forging to a certain temperature, and slowly cool it after holding it for a period of time to eliminate residual stress. Vibration aging is the use of vibration exciter to exert a certain frequency and amplitude of vibration on the forging, so that the residual stress inside the material can be released. Both of these methods can effectively eliminate residual stress in a short time, but require high equipment input and operating costs.
Mechanical treatment: Through mechanical processing or cold treatment and other methods to change the stress state of the surface of the material, so as to eliminate residual stress. For example, shot peening or rolling of forgings can introduce compressive stress on the surface that counteracts the tensile stress inside the material, thereby reducing residual stress. This method is suitable for the removal of local residual stress, and the effect is remarkable.
Chemical treatment: The use of chemical methods to change the structure and stress state of the material, so as to eliminate residual stress. For example, chemical corrosion or electrochemical treatment of forgings can remove the layer of residual stress on the surface of the material. This method has a good effect on eliminating deep residual stress, but the treatment conditions and time need to be strictly controlled to avoid adverse effects on material properties.
Composite treatment: the above methods are applied in combination to give full play to their respective advantages and improve the elimination effect of residual stress. For example, thermal aging treatment is performed first to remove most of the residual stress, followed by mechanical treatment or chemical treatment to remove local or deep residual stress. This method can obtain better treatment effect, but the operation is more complicated and the cost is higher.
The removal of residual stress in petrochemical forgings is an important technical task, which is related to the quality and performance of the forgings. This paper introduces several common residual stress relief methods and analyzes their advantages and disadvantages. In the actual production process, the appropriate method should be selected to eliminate the residual stress according to the material, structure and process requirements of the forging. In the future, with the continuous progress and innovation of science and technology, the residual stress elimination technology of petrochemical forgings will be continuously improved and improved to provide a strong guarantee for the sustainable development of the petrochemical industry.
