What are the factors that affect the internal stress of heat treatment of shaft forgings?
2024-08-21
During the heat treatment of shaft forgings, three basic types of internal stresses may be generated. These internal stresses have an important impact on the performance and life of shaft forgings. In the actual production process, shaft forgings often produce two or three basic internal stresses at the same time, therefore, the residual stress after heat treatment is the result of the superposition of these basic internal stresses. In order to better understand this phenomenon, we need to explore the mechanism and influence factors of each basic internal stress.
First, consider the thermal stress caused by temperature changes during heat treatment. During the heating and cooling process, the temperature distribution of each part of the shaft forging is uneven, resulting in inconsistent volume changes, resulting in thermal stress. The magnitude and distribution of this stress is related to factors such as heating and cooling rates, temperature gradients, and material thermophysical properties.
Secondly, the phase transformation stress is generated due to the metal phase transformation during the heat treatment. During the phase transition, the volume and lattice structure of the material change, resulting in the generation of phase transition stress. The magnitude and distribution of this stress are closely related to the temperature of the phase transition point, the phase transition rate and the phase transition behavior of the material.
Finally, there is also a kind of tissue stress due to the non-uniformity of the tissue structure. Before heat treatment, the microstructure of the shaft forging already exists, and these inhomogeneities will cause tissue stress during heat treatment. The distribution of this stress is related to the homogeneity of the original tissue, changes during heat treatment, and the inherent properties of the material.
When these basic internal stresses are simultaneously generated and superimposed in the shaft forging, the situation becomes more complicated. The distribution of residual stress after superposition is quite complex, which is not only related to the specific parameters of heat treatment process such as heating temperature and cooling method, but also closely related to the geometry, material composition and manufacturing process of the shaft forging. Therefore, it is a challenging task to accurately predict and control the residual stress of shaft forgings after heat treatment.
In order to optimize the heat treatment process of shaft forgings and reduce the adverse effects of residual stress on performance, in-depth research and practice are needed. Through reasonable process design and optimization of parameters, the residual stress can be effectively controlled, thereby improving the service life and reliability of shaft forgings.
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