Stress elimination process methods for mechanical valve castings
In the manufacturing process of mechanical valves, castings are an indispensable part. Castings are obtained through the casting process from the molten metal liquid, and the internal microstructure and external shape of the casting are closely related to the casting process, raw materials, and casting conditions. However, due to factors such as phase transformation inside the casting, cooling shrinkage, and casting stress, internal stresses may occur in the casting during the cooling process. These stresses are unevenly distributed within the casting and may cause defects such as cracks and deformation. In severe cases, they may even reduce the service performance of the casting. Therefore, it is crucial to eliminate internal stresses in castings and improve their mechanical properties to ensure the quality of the castings.
The stress relief process for mechanical valve castings mainly includes heat treatment, mechanical treatment, and the comprehensive process of heat treatment combined with mechanical treatment. The following will introduce these process methods separately.
1. Heat treatment process
The heat treatment process is a method to change the internal microstructure of the metal material by heating and cooling, thereby improving its mechanical properties. The heat treatment process mainly includes annealing, normalizing, quenching, and tempering. Among them, the annealing and normalizing processes can eliminate the residual stress inside the casting, improve the strength and hardness of the casting, and improve its plasticity and toughness; the quenching and tempering processes can improve the hardness and wear resistance of the casting, and can also eliminate the residual stress inside the casting, improve its mechanical properties. The temperature and time of the heat treatment process are key factors affecting the stress relief effect of the casting. It is necessary to determine the appropriate heat treatment process parameters according to the material and performance requirements of the casting through experiments.
2. Mechanical treatment process
The mechanical treatment process mainly includes mechanical vibration treatment and mechanical impact treatment. Mechanical vibration treatment is to produce periodic stress changes inside the casting through mechanical vibration, thereby eliminating the residual stress inside the casting. Mechanical impact treatment is to produce instantaneous stress changes inside the casting through mechanical impact, thereby eliminating the residual stress inside the casting. The vibration frequency and impact force of the mechanical vibration treatment and mechanical impact treatment process are key factors affecting the stress relief effect of the casting. It is necessary to determine the appropriate mechanical vibration treatment and mechanical impact treatment process parameters according to the material and performance requirements of the casting through experiments.
3. Comprehensive process of heat treatment combined with mechanical treatment
The comprehensive process of heat treatment combined with mechanical treatment combines the heat treatment and mechanical treatment processes to improve the mechanical properties of the casting. Heat treatment can eliminate the residual stress inside the casting, improve the strength and hardness of the casting, and improve its plasticity and toughness; mechanical treatment can eliminate the residual stress inside the casting, improve the hardness and wear resistance of the casting. The comprehensive process of heat treatment combined with mechanical treatment can eliminate the residual stress inside the casting at the same time, improve the mechanical properties of the casting, and is an effective stress relief process.
The stress relief process for mechanical valve castings is an important means to ensure casting quality. In the actual production process, it is necessary to select an appropriate stress relief process according to the material and performance requirements of the casting to improve the mechanical properties of the casting and ensure the quality of the casting. At the same time, it is also necessary to carry out appropriate heat treatment and mechanical treatment on the casting to eliminate the residual stress inside the casting and improve the mechanical properties of the casting.