In the process of manufacturing thermal power forgings, residual stress is almost inevitable. These stresses are caused by the uneven deformation and cooling of the material during the manufacturing process. If these stresses are not effectively controlled, it may have an adverse effect on the performance and service life of the forging. Therefore, it is very important to analyze and control the residual stress in manufacturing thermal power forgings.
Residual stress analysis
Causes of residual stress
In the manufacturing process of thermal power forgings, residual stress is mainly caused by the following reasons:
(1) Uneven deformation: In the forging process, due to the uneven plastic deformation of the material, the deformation degree of the material in different parts is different, resulting in internal stress.
(2) Cooling process: After the forging is completed, the forging will produce thermal stress due to the temperature difference in different parts during the cooling process.
Distribution of residual stress
The distribution of residual stress in thermal power forgings is complicated, which is affected by many factors such as material properties, forging process and cooling conditions. In general, residual stress exists on the surface and inside of the forging, and stress concentration may occur in some parts.
Effect of residual stress
Residual stress has an important effect on the performance and service life of thermal power forgings. First, residual stress can cause forgings to deform or crack during service. Secondly, residual stress may also affect the fatigue life and corrosion resistance of forgings. Therefore, it is necessary to control the residual stress effectively.
In order to control the residual stress in the manufacture of thermal power forgings, the following methods can be adopted:
Improve the quality of raw materials: By optimizing the chemical composition and organizational structure of the material, improve the plasticity and toughness of the material, and reduce the deformation non-uniformity during the forging process.
Optimization of forging process: Through reasonable design of forging process, reduce the deformation of materials. For example, methods such as multi-directional forging or multi-stage forging can be used.
Add applied stress: Balance the residual stress inside by applying applied stress during or after forging. For example, methods such as heat treatment or mechanical loading can be used.
Control cooling conditions: Through reasonable control of cooling speed and temperature gradient, reduce the thermal stress generated in the cooling process. For example, methods such as slow cooling or isothermal cooling can be used.
Taking the turbine blade of a thermal power plant as an example, the blade produced a large residual stress during the manufacturing process. Through the analysis, it is found that these stresses are mainly caused by the uneven deformation and cooling of the material during the forging process. In order to control these stresses, the following methods are adopted:
Optimization of forging process: the use of multi-directional forging method to reduce the deformation of the material uneven.
Add external stress: After forging is completed, external stress is applied by heat treatment method to balance the internal residual stress.
Control cooling conditions: Slow cooling method is used to reduce the thermal stress generated during cooling.
Through the implementation of these measures, the residual stress in turbine blades is successfully controlled, and the performance and service life of turbine blades are improved.
The analysis and control of residual stress in manufacturing thermal power forgings is a very important work. By analyzing the causes and effects of residual stress, we can take targeted control methods, such as improving the quality of raw materials, optimizing the forging process, adding external stress and so on. In practical application, it is necessary to choose the appropriate control method according to the specific situation, and comprehensively consider the factors such as technical feasibility, economy and environmental friendliness. Through continuous optimization and improvement of control methods, the high efficiency, high quality and sustainable development of thermal power forging manufacturing can be achieved.
