Why does turbulence occur in precision casting

As an advanced manufacturing technology, precision casting involves multiple processes such as the injection of high-temperature molten metal, mold filling, cooling, and solidification. In these stages, turbulence is a common and important issue that needs to be taken seriously. The phenomenon of turbulent flow not only affects the forming quality of castings, but may also lead to defects or even scrap of castings. Therefore, a deep understanding of the causes of turbulent flow in precision casting is of great significance for improving casting quality and optimizing casting processes.

1、 The definition and impact of turbulent flow phenomenon

The turbulent flow phenomenon refers to the non-uniform, unstable, and irregular flow state of molten metal in the mold during precision casting. This flow state can lead to uneven distribution of molten metal in the mold, resulting in defects in the casting during solidification, such as shrinkage, porosity, inclusions, etc. The phenomenon of turbulent flow may also cause an increase in surface roughness of castings, reducing their accuracy and performance.

2、 The causes of turbulent flow phenomenon in precision casting

Unreasonable mold design
Mold design is a crucial step in the precision casting process, and factors such as the structure, size, and gate position of the mold directly affect the flow state of the molten metal. If the mold design is unreasonable, such as improper gate position, unreasonable runner design, etc., it is easy to cause turbulent flow of molten metal in the mold.

Improper temperature control of molten metal
The temperature of molten metal is an important factor affecting its flowability. If the temperature of the molten metal is too high, its fluidity will increase, but it may cause the molten metal to flow too quickly in the mold, resulting in turbulent flow; If the temperature is too low, the fluidity of the molten metal will weaken, which may lead to insufficient filling or the formation of a cold shut. Therefore, reasonable control of the temperature of the molten metal is the key to preventing turbulence.

Improper control of injection speed and pressure
In precision casting, injection speed and pressure are important factors affecting the flow state of molten metal. If the injection speed is too fast or the pressure is too high, the flow rate of the metal liquid in the mold will increase, which is prone to the phenomenon of turbulent flow; On the contrary, if the injection speed is too slow or the pressure is too low, it may lead to insufficient filling of the metal liquid and affect the quality of the casting.

Uneven distribution of mold temperature
The uneven distribution of mold temperature is also an important reason for the phenomenon of turbulent flow. During the casting process, the mold temperature has a significant impact on the fluidity and solidification rate of the molten metal. If the temperature distribution of the mold is uneven, it may lead to resistance differences in different areas when the metal liquid flows inside the mold, resulting in turbulent flow phenomenon.

Gas entrapment and poor exhaust
During the process of injecting molten metal into the mold, if the gas is not discharged in a timely manner, or if the design of the mold exhaust system is unreasonable, it may cause the gas to be drawn into the molten metal, forming bubbles or pores. These bubbles or pores may cause interference during the flow of molten metal, leading to the occurrence of turbulence.

3、 Measures to solve the turbulent flow phenomenon in precision casting

Optimize mold design
To address the issue of unreasonable mold design, measures such as improving mold structure, optimizing runner design, and adjusting gate position should be taken to reduce the occurrence of turbulent flow. Meanwhile, the selection of mold materials and surface treatment are also important factors that affect the flow of molten metal and should be fully considered.

Accurate control of molten metal temperature
In order to maintain the stability of the molten metal temperature, advanced temperature control equipment and technology should be used to ensure that the metal liquid reaches the optimal flow state before injection into the mold. At the same time, adjust the temperature range of the molten metal reasonably according to different casting materials and process requirements.

Reasonably control injection speed and pressure
During the casting process, injection speed and pressure parameters should be reasonably set based on the structure and size of the casting. By precisely controlling the injection speed and pressure, it is possible to ensure that the molten metal flows uniformly and stably within the mold, reducing the occurrence of turbulence.

Improve mold temperature distribution
To improve the problem of uneven temperature distribution in the mold, measures such as preheating the mold and optimizing the design of the cooling system can be taken. By improving the uniformity of mold temperature, the resistance difference experienced by the molten metal during the flow process can be reduced, thereby reducing the phenomenon of turbulent flow.

Optimize exhaust system
To address the issues of gas entrapment and poor exhaust, the exhaust system design of the mold should be optimized to ensure timely gas discharge during the metal liquid injection process. At the same time, strengthen the sealing of the mold to prevent external gas from entering the interior of the mold.

4、 Conclusion

In summary, there are various reasons for the occurrence of turbulence in precision casting, including mold design, temperature control of molten metal, injection speed and pressure control, mold temperature distribution, and gas entrainment and exhaust. To solve this problem, we need to take comprehensive measures from multiple perspectives to optimize the casting process and improve the quality of castings. Through continuous research and practice, we believe that the occurrence of turbulent flow can be effectively reduced, promoting the development and application of precision casting technology.

Post time: Mar-27-2024