Although the three major components of continuous casting serve different functions, their raw materials and production processes are largely identical. These components refer to the three functional refractory materials used in the continuous casting process: stopper rods, long nozzles, and submerged nozzles. With the exception of a small portion of submerged nozzles made from fused quartz, the vast majority of these components are composed of aluminum-carbon materials. Consequently, the primary production raw materials can be categorized into main components, graphite materials, additives, and binders. Given the significant impact of raw materials on product performance, strict requirements are imposed on the particle size, purity, and structure of materials used in manufacturing these three major components.

Primary raw materials

Primary raw materials primarily include various corundum materials, fused magnesia, spinel, fused zirconia, fused quartz, and fused mullite. The selection of primary raw materials depends on the specific product and location within the furnace. Typically, the core components utilize corundum or high-alumina materials. The slag line section employs partially stabilized fused zirconia. For the stopper head and nozzle bowl, materials like corundum, fused magnesia, or spinel are selected based on the steel grade being cast. Quartz and mullite are incorporated to enhance thermal shock stability. Aggregate particle size is generally required to be below 1 mm.

Graphite raw materials

The extensive use of graphite in the “three major components” of continuous casting equipment is to impart high thermal shock resistance and erosion resistance to the products. However, the drawback of using graphite is that it makes the products prone to oxidation. Therefore, to prevent graphite oxidation and enhance the products’ erosion resistance, high-purity flake graphite is often employed.

Additives

To enhance the performance of continuous casting “three major components,” modifying additives such as antioxidants are often incorporated into the mixture. Commonly used antioxidants include metallic aluminum powder, silicon powder, silicon carbide, boron carbide, Al-Si and Al-Mg alloy powders, etc. The incorporation of additives sometimes leverages the generation of non-oxides during heat treatment, such as SiC, Si₃N₄, or AlN, to enhance material properties. Alternatively, they may oxidize prior to graphite during use, reducing CO back to C to inhibit carbon consumption in the product. Or they may form C and oxides to increase the refractory’s density, create a protective layer, promote graphite crystallization, and enhance the product’s high-temperature strength.

Organic binder

The binders used in the “three major components” of continuous casting are all resins, including phenolic resins and furfural-phenolic resins. These resins form carbon bonds after heat treatment, imparting high strength to the cast products. Therefore, the resins must possess high residual carbon content, suitable viscosity, and stable performance. The typical resin addition rate ranges from 5% to 10%.

The production process is as follows: Blank preparation → Isostatic pressing → Drying and heat treatment → Forming → X-ray inspection → Surface anti-oxidation coating → Packaging and storage.

(1) The preparation of green bodies involves processes such as batching, mixing, pelletizing, and drying. Batching entails accurately measuring raw materials according to predetermined mass percentages; mixing and pelletizing involve blending the batch-prepared materials, adding binders, and forming pellets using a pelletizer, followed by drying the pellets to meet molding requirements. Common mixing and pelletizing equipment includes high-speed mixers. During feeding, aggregates, resins, graphite, and pre-mixed powders are added first. These high-speed mixers also perform pelletizing functions. Drying equipment can utilize conventional refractory drying systems or fluidized bed dryers, typically operating at temperatures not exceeding 80°C.

(2) Molding: Place pellets from Step 1 into a composite rubber mold with a steel core. During loading, ensure materials are added separately from different sections. After sealing, use an isostatic press to form the product while selecting appropriate pressure, pressure ramp, holding, and release curves.

(3) Drying and Heat Treatment: Volatile components are removed through drying, followed by calcination in an oxygen-free environment. This decomposes and carbonizes the resin, forming carbon bonds that impart high bonding strength to the material. Heat treatment is typically conducted in shuttle kilns at temperatures ranging from 1000 to 1250°C.

(4) X-ray Inspection: Continuous casting “three major components” must be free of any internal damage during operation. Non-destructive testing is required, employing X-ray flaw detectors.

(5) Machining and Surface Coating: Isostatic pressing cannot achieve the required dimensional accuracy, particularly for mating surfaces. Machining is necessary for partial or full dimensional correction of the “three major components.” Additionally, to prevent oxidation during on-site baking and use, protective coatings must be applied to the product surfaces. The formulated coatings must melt into glaze at relatively low temperatures (600–750°C), spread evenly over the product surface, and maintain viscosity without significant variation across a wide temperature range to effectively shield the graphite from oxidation.