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1、 Introduction

With the continuous development of modern industry, the requirements for the quality and performance of metal materials are becoming increasingly high. As an important link in the production of steel and non-ferrous metals, the development level of continuous casting technology directly affects the quality and production efficiency of metal materials. Vacuum continuous casting technology is based on traditional continuous casting technology, which places the mold in a vacuum environment for casting. It has significant advantages such as reducing gas content in the molten metal, reducing inclusions, and improving the quality of the casting billet. Accurately controlling the metal flow in a vacuum environment is the key to achieving high-quality vacuum continuous casting.

2、 Overview of Vacuum Continuous Casting Technology

（1） The principle of vacuum continuous casting

Vacuum continuous casting is the process of injecting molten metal into a crystallizer in a vacuum environment and forming a cast billet through cooling and solidification. In a vacuum environment, the solubility of gases in the molten metal decreases, making it easier for gases to escape, thereby reducing defects such as porosity in the cast billet. At the same time, a vacuum environment can also reduce the contact between molten metal and air, and decrease the generation of oxidation and inclusions.

（2） Characteristics of vacuum continuous casting

Improving the quality of castings: reducing defects such as pores and inclusions, and enhancing the density and purity of castings.

Improving the solidification structure of metals: beneficial for refining grain size and enhancing the mechanical properties of metals.

Reduce production costs: Reduce subsequent processing steps and improve production efficiency.

3、 The Influence of Vacuum Environment on Metal Liquid Flow

（1） Decreased gas solubility

In a vacuum environment, the solubility of gases in molten metal is significantly reduced, making it easier for gases to escape and form bubbles. If bubbles cannot be expelled in a timely manner, defects such as air holes will form in the casting, affecting the quality of the casting.

（2） Surface tension variation

The vacuum environment will change the surface tension of the metal liquid, affecting the flow state and solidification process of the metal liquid in the crystallizer. The change in surface tension may lead to a change in the wettability of the molten metal, affecting the contact state between the cast billet and the crystallizer wall.

（3） Reduced flow resistance

In a vacuum environment, the resistance of air to the flow of molten metal decreases, and the velocity of the molten metal increases. This requires more precise control of the metal flow to prevent phenomena such as turbulence and splashing.

4、 Key equipment and technical means for precise control of metal flow in vacuum continuous casting machine

（1） Crystallizer

The function of crystallizer

Crystallizer is the core component of vacuum continuous casting machine, whose main function is to cool and solidify the molten metal in it to form a cast billet. The shape and size of the crystallizer directly affect the quality and dimensional accuracy of the cast billet.

Design requirements for crystallizer

In order to achieve precise control of metal flow, the design of the crystallizer should meet the following requirements:

(1) Good thermal conductivity: able to quickly transfer the heat of the molten metal, ensuring the cooling speed of the cast billet.

(2) Appropriate taper: The taper of the crystallizer should be designed based on the shrinkage characteristics of the casting to ensure good contact between the casting and the crystallizer wall, and to prevent phenomena such as pulling and leakage.

(3) Stable liquid level control: By precise liquid level detection and control devices, the stability of the metal liquid level in the crystallizer is maintained, ensuring the uniformity of the casting quality.

（2） Stick system

The function of the plug

A stopper is an important device used to control the flow rate and velocity of molten metal into the crystallizer. By adjusting the position of the stopper, the size and speed of the metal flow can be precisely controlled.

Control principle of plunger system

The plug rod system usually consists of a plug rod, a drive mechanism, and a control system. The control system adjusts the position of the plug rod through the driving mechanism based on process requirements and liquid level detection signals, achieving precise control of the metal liquid flow.

（3） Electromagnetic stirring

The principle of electromagnetic stirring

Electromagnetic stirring is the use of the principle of electromagnetic induction to generate a rotating magnetic field in liquid metal, causing stirring motion in the liquid metal. Electromagnetic stirring can improve the flow state of molten metal, promote the floating of inclusions and the escape of gases, and improve the quality of castings.

Types and Applications of Electromagnetic Stirring

Electromagnetic stirring is divided into different types such as crystallizer electromagnetic stirring, secondary cooling zone electromagnetic stirring, and solidification end electromagnetic stirring. According to different process requirements and casting quality requirements, suitable types of electromagnetic stirring can be selected for application.

（4） Liquid level detection and control system

Method of liquid level detection

Liquid level detection is one of the key links to achieve precise control of metal liquid flow. The commonly used liquid level detection methods include radioactive isotope detection, ultrasonic detection, laser detection, etc. These detection methods have the advantages of high accuracy and fast response speed, and can monitor the changes in the liquid metal level in the crystallizer in real time.

Composition and working principle of liquid level control system

The liquid level control system usually consists of liquid level sensors, controllers, and actuators. The liquid level sensor transmits the detected liquid level signal to the controller. The controller adjusts the position of the plunger or other control parameters through the actuator according to the process requirements and set values, achieving stable control of the metal liquid level.

5、 Process optimization of precise control of metal flow in vacuum continuous casting machine

（1） Optimize pouring parameters

Pouring temperature: Reasonable control of pouring temperature can ensure the fluidity and filling ability of the metal liquid, while avoiding excessive temperature that may cause oxidation and suction of the metal liquid.

Pouring speed: Choose the appropriate pouring speed based on the size and quality requirements of the casting billet. Excessive pouring speed may cause unstable metal flow, resulting in turbulence and splashing; A too slow pouring speed will affect production efficiency.

（2） Improve the cooling system of the crystallizer

Control of cooling water flow rate and flow rate: Based on the solidification characteristics and quality requirements of the casting billet, the cooling water flow rate and flow rate of the crystallizer should be reasonably controlled to ensure the cooling speed and uniformity of the casting billet.

Selection of cooling methods: Different cooling methods such as water cooling and aerosol cooling can be used, and the selection and optimization can be based on specific situations.

（3） Collaborative control of electromagnetic stirring and plug rod system

Optimization of electromagnetic stirring parameters: Based on the quality requirements and process characteristics of the casting blank, optimize the frequency, intensity, and stirring method of electromagnetic stirring to fully utilize its function.

Collaborative control of plug system and electromagnetic stirring: Through a reasonable control strategy, the collaborative work of plug system and electromagnetic stirring can be achieved to improve the stability of metal flow and the quality of castings.

6、 Conclusion

The precise control of metal flow in a vacuum environment by a vacuum continuous casting machine is the key to achieving high-quality billet production. Through the application of key equipment and technical means such as crystallizers, stopper systems, electromagnetic stirring, liquid level detection and control systems, as well as process optimization, precise control of metal flow can be effectively achieved. In the future, with the development of intelligent technology and the application of new materials, vacuum continuous casting technology will continue to innovate and improve, providing more reliable and efficient technical support for the production of metal materials. At the same time, we also need to face challenges such as high technical difficulty, high cost, and talent shortage, and promote the development and application of vacuum continuous casting technology through continuous efforts and innovation.