In the aftermath of June 9th, numerous domestic foundry companies began adopting resin sand casting production lines to enhance product quality. To further improve the surface finish of castings, most resin sand molding and graphite coating lines now utilize water-based graphite coatings. The surface drying furnace plays a crucial role in this process, as it dries the sand surface without heating the entire workpiece, thus accelerating heat exchange on the sand surface while minimizing internal temperature rise—making it an energy-efficient solution.
Within the working range, the temperature difference remains within ±3°C, ensuring consistent performance. The furnace temperature is carefully controlled along the enclosure’s temperature, with a tolerance of ±5°C. This prevents overheating and potential damage to the sand mold, preserving its structural integrity. There are two main types of sand type dry furnaces: chamber type and pass type, each utilizing different energy sources such as gas or fuel. When shutting down variable frequency furnaces, it's essential to clean out any molten iron and residue from the furnace mouth and lining to maintain efficiency.
A large axial fan is used to blow cold air down the side of the furnace wall and expel hot air through the taphole, reducing oxidation lines and cracks on the furnace wall, thereby extending the lining’s lifespan. The cast iron trough of the inverter furnace is made using castable materials, allowing for over 38 heats with minimal maintenance. Through continuous improvements in shutdown procedures, the furnace lining has achieved a service life of 260 cycles.
The internal water circulation system of the electric furnace uses copper or stainless steel pipes, ensuring high-quality water flow. After installation, the waterway must be thoroughly cleaned. Before the first use of the electric furnace, a low-temperature drying method should be applied. A hot air heating circulation system is implemented, featuring equal pressure air supply boxes and matrix-shaped speed nozzles that enhance heat exchange and promote rapid, energy-efficient heating.
Chemical self-hardening sand molding has very low moisture content. After applying a water-based coating, the sand absorbs some of the moisture, allowing the coating to adhere properly. The moisture evaporates at elevated temperatures, meeting the requirements of the casting process. The hot air drying process for sand shovels and sand squeezing differs significantly. While the former only needs to evaporate the paint, the latter involves drying the sand itself to a much greater depth, which can lead to energy savings and improved yield.
The sintering process for the electric furnace lining is determined by the maximum operating temperature and the characteristics of the lining material, adjusting according to the moisture content. The electric furnace tapping trough constructed with castables offers excellent slag resistance and long service life, reducing cleaning and maintenance efforts. Quenching during shutdown helps prevent cracking in the lining, enhancing durability.
The principles and structure of the drying oven require precise control of hot air parameters. The sand surface dries faster than the sand type due to higher heat transfer rates, leading to quick evaporation of surface moisture and minimal heat loss. Hot air temperature, speed, and duration are key factors, limited by the properties of the sand binder. Higher temperatures accelerate drying but increase the risk of heat damage.
To achieve uniform hot air flow, the furnace system includes a nozzle matrix and an annular return air duct. The electric heater and induced draft fan work together to circulate heated air, maintaining optimal conditions for drying. The hot air jet directly acts on the sand surface, rapidly absorbing heat and evaporating moisture. Temperature control in the drying furnace focuses on the supply air temperature of the hot air circulation system, ensuring it does not exceed the allowable limits for resin sand.
Artificial intelligence regulators offer advanced control features, including multiple functional modules, programmable settings, and adaptive tuning. These regulators improve control accuracy, response speed, and system stability. They also allow for flexible adjustments and seamless integration with automated systems. Using thyristor power regulators instead of contactors improves temperature control accuracy, reduces noise, and extends equipment life.
Interlocking mechanisms ensure safe operation between the drying furnace, electric boiler, and heater. The induced draft fan must run correctly before the heater is activated, preventing overheating and ensuring proper airflow. Electrical connections and safety protocols are critical to avoid damage and ensure reliable performance.
Overall, the implementation of advanced drying technologies, intelligent control systems, and optimized furnace designs has significantly improved the efficiency, quality, and reliability of the casting process. These innovations not only reduce energy consumption and maintenance costs but also contribute to sustainable and high-performance manufacturing.
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