Because residual internal stress inside castings could reduce the quality of the cast iron plates, even further damage the plates, aging treatment should be taken to remove the residual internal stress when arranging production. Here are the methods we can consider:

 

1. Natural aging: Place the castings with residual stress in the open field and let the residual stress gradually disappear naturally after half a year or even more than a year. This method is called natural aging.

 

There is residual stress in the casting (machine tool casting), the metal lattice is distorted, and the atomic potential energy on the distorted lattice is high and unstable. Due to the long-term effect of natural climate, the slow energy exchange between the metal atoms continues, gradually Balance, so that the distorted lattice returns to normal, the casting is deformed, and the stress is relieved. Natural aging costs less, but the time is too long, and it is rarely used in modern production.

 

2. Artificial aging: artificial aging is also called thermal aging or internal stress elimination annealing, etc., the casting is heated to the temperature range of the elastic-plastic state of the alloy for a certain period of time to eliminate the residual stress, and then slowly cooled to avoid regenerating Residual Stress. The heat treatment process specifications of the castings such as heating, heat preservation and cooling should be determined according to the characteristics of the alloy properties, the structure of the castings and the original cooling conditions.

 

The general principle is: in the process of heating and cooling, strive to make the temperature of each part of the casting uniform, and avoid excessive temperature difference and additional stress that may cause casting deformation and cracks. Therefore, the heating and cooling speed should not be too high, but from the productivity and cost Considering that the rate of heating and cooling should not be too low, the best heat treatment specifications are generally determined by experimental methods in production.

 

3. Resonance aging Resonance aging is an advanced method that saves time and energy. Its principle is: under the action of the periodic external force of the exciter---exciting force, it resonates with the casting, so that the casting gains considerable Vibration energy. In the resonance process, the alternating stress and the residual stress are superimposed to produce local yield and cause plastic deformation. The residual stress in the casting (machine tool casting) gradually relaxes and disappears, thereby achieving the purpose of stabilizing the size of the casting.

 

Therefore, resonance aging has significant advantages: short time, low cost, low power, small device, easy operation, energy saving, no pollution, no oxide scale on the surface of the casting, and no damage to the dimensional accuracy of the casting.

 

In modern production industry, artificial aging is the most popular method today, because of its good effect and low cost, it is widely favored by the production industry.

 

 

 

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