In modern steel casting industry, refractory plug brick is one of the indispensable key components. It plays a vital role in the casting process, ensuring the smooth casting process and the stability of product quality. This paper will introduce the definition, function, characteristics, manufacturing and application of refractory plug brick in detail.

I. Definition and structure of plug brick

Stopper head brick is a kind of refractory product used to control the flow of molten steel, which is usually installed at the bottom of the stopper rod and closely matched with the nozzle brick. Its main function is to control the flow and direction of molten steel in the casting process and ensure that molten steel can flow into the crystallizer smoothly and evenly. The structural design of plug brick is usually cylindrical or conical, which has high strength and wear resistance and can withstand the erosion and erosion of high temperature molten steel.

II. Functions of plug bricks

Control of molten steel flow: Close cooperation between plug brick and nozzle brick is the key to realize molten steel flow control. By adjusting the position of the plug brick, the flow of molten steel can be accurately controlled, thus meeting the requirements of different casting processes. For example, in the process of continuous casting, the plug brick can quickly respond to the instructions of the operator, realize the rapid opening and closing of molten steel and the flow adjustment, and ensure the quality and dimensional accuracy of the billet.

Prevent molten steel from leaking: In the non-pouring state, it is necessary to maintain good sealing between the plug brick and the nozzle brick to prevent molten steel from leaking from the gap. This not only helps to improve production efficiency, but also avoids safety accidents and equipment damage caused by molten steel leakage.

Protect the plug rod: The wear resistance and erosion resistance of the plug brick can effectively protect the plug rod from direct erosion by high-temperature molten steel and slag, prolong the service life of the plug rod and reduce the production cost.

III. Characteristics of plug bricks

High fire resistance: plug bricks need to work in high temperature environment for a long time, so they must have high fire resistance. Its main component is usually alumina (Al₂O₃), the content of which is between 40% and 75%, which can withstand the high temperature above 1600℃ and ensure that it will not be softened or deformed due to high temperature in the casting process.

Good thermal shock resistance: during the casting process, the plug brick will be frequently subjected to sharp changes in temperature, such as from high-temperature molten steel to relatively low ambient temperature. Therefore, the plug brick needs to have good thermal shock resistance, which can maintain the structural integrity during the rapid cooling and heating cycle and avoid cracking or peeling caused by thermal stress.

Excellent wear resistance and corrosion resistance: molten steel will have a strong scouring effect on plug bricks during flowing, and slag will also cause chemical erosion on plug bricks. The wear resistance and erosion resistance of plug brick can effectively resist these destructive forces, prolong its service life, reduce the replacement frequency and improve production efficiency.

No pollution to molten steel: the plug brick should not pollute the molten steel when it comes into contact with molten steel. Therefore, its material must have good chemical stability and will not react with molten steel to ensure the purity and quality of molten steel.

IV. Manufacturing of plug bricks

The production and manufacture of plug bricks is a complex process, which needs to be strictly controlled by many links to ensure the quality and performance of products.

Selection of raw materials: high-quality raw materials are the basis for producing high-performance plug bricks. High-purity refractories such as alumina, corundum and mullite are usually selected as the main raw materials, which have high melting point, high hardness and good corrosion resistance. At the same time, appropriate additives, such as silicon carbide and silicon nitride, will be added to improve the performance of the plug brick.

Forming technology: the forming technology of plug brick mainly includes pressing forming and pouring forming. Compression molding is to put the mixed raw materials into a mold and press molding under high pressure. The molded green body has high density and good strength, but its shape is relatively simple. Pouring molding is to mix raw materials with binder and pour them into the mold for pouring molding. The molded green body has high shape complexity, but the density is relatively low. According to the shape and performance requirements of the plug brick, the appropriate molding process is selected.

Sintering process: Sintering is a key link in the production process of plug bricks. Through high-temperature sintering, various components in raw materials react chemically to form a dense ceramic structure, which improves the strength and fire resistance of plug bricks. The firing temperature is generally between 1400℃ and 1600℃, and the firing time depends on the specific requirements of the product. In the firing process, it is necessary to strictly control the temperature and atmosphere to ensure the quality and performance of the products.

Quality inspection: The produced plug bricks need to undergo strict quality inspection, including appearance inspection, size measurement, chemical composition analysis and physical performance test. Appearance inspection mainly checks whether there are cracks and defects on the surface of the plug brick; The dimension measurement ensures that the dimension accuracy of the plug brick meets the design requirements; Chemical composition analysis and physical performance test are used to evaluate the fire resistance, thermal shock resistance, wear resistance and other performance indexes of plug bricks. Only through strict quality inspection can the reliability and stability of plug bricks be ensured in practical application.

V. Application of plug brick

Plug bricks are widely used in steel casting industry, especially in the process of continuous casting and die casting. In the process of continuous casting, plug bricks and nozzle bricks are used together to control the flow and direction of molten steel and realize continuous and stable casting process. By accurately controlling the flow rate of molten steel, the quality and dimensional accuracy of billet can be improved and the rejection rate can be reduced. In the process of die casting, the plug brick is used to control the pouring speed and pouring time of molten steel, so as to ensure that molten steel can fill the mold evenly and avoid defects such as insufficient pouring and cold insulation. In addition, plug bricks can be customized according to different casting processes and steel grade requirements to meet the needs of various special applications.

VI. Development Trend of Plug Brick

With the continuous development of iron and steel industry, higher requirements are put forward for the performance and quality of plug bricks. In the future, the development of plug bricks will show the following trends:

High-performance: With the continuous optimization of steel production technology, the requirements for fire resistance, thermal shock resistance, wear resistance and erosion resistance of plug bricks will be higher and higher. Research and development of new refractory materials and production technology with higher performance will become the key direction of plug brick development.

Intelligence: Under the background of intelligent manufacturing, the production and use of plug bricks will gradually realize intelligence. For example, by embedding sensors in the plug brick, the working state and performance changes can be monitored in real time, and the accurate control and fault early warning of the casting process can be realized.

Environmental protection: Under the increasingly strict environmental protection policy, the production process of plug bricks will pay more attention to energy saving, emission reduction and resource recycling. Developing low energy consumption, low pollution production technology and recyclable refractories will become the future development trend.

Customization: Different iron and steel enterprises have different production processes and equipment, and have different requirements on the size, shape and performance of plug bricks. Therefore, customized production will become an important development direction of the plug brick market to meet the individual needs of different customers.

VII. Conclusion

Refractory plug brick plays an important role in iron and steel casting industry, and its performance and quality directly affect the stability of casting process and the quality of billet. By continuously optimizing the production process and performance of plug bricks, the efficiency and quality of steel production can be improved and the production cost can be reduced. In the future, with the continuous development and technological innovation of the steel industry, plug bricks will develop in the direction of high performance, intelligence, environmental protection and customization, which will provide strong support for the sustainable development of the steel industry.