China Henan Rongsheng Xinwei New Materials Research Institute Co., Ltd Company News

When purchasing refractory materials for glass melting furnaces, in addition to the high-temperature performance discussed earlier, their physical properties are also crucial. The physical properties of the product are closely related to its actual service life, and specific items to consider include:   1.Microstructure: Porosity: Refractory materials typically contain various sizes and shapes of pores. Porosity is often categorized into open pores (or visible pores), connected pores, and closed pores. Porosity rate reflects the density of refractory materials, indicating the percentage of pore volume in the total volume of the brick. Lower porosity rates generally correspond to better erosion resistance and higher structural strength.   Bulk Density: This refers to the mass of refractory material per unit volume, including pores. It directly reflects the density of the refractory product and is a significant indicator of its quality. Higher bulk densities usually indicate lower porosity rates and better performance in terms of strength and resistance to high temperatures.   True Density: True density represents the ratio of the mass of porous materials to their true volume (excluding pores). It's related to the chemical mineral composition of refractory materials and is independent of porosity and density. 2.Thermal Properties: Thermal Expansion: Refractory materials expand with increasing temperature. Thermal expansion properties are usually expressed using coefficients of linear or volumetric expansion. It's crucial to consider these properties when designing furnace structures to accommodate thermal expansion and prevent damage.   Thermal Conductivity: This property measures the ability of refractory materials to conduct heat and is represented by thermal conductivity. It depends on the material's chemical composition and microstructure.   Heat Capacity: Heat capacity, also known as specific heat capacity, refers to the amount of heat required to raise the temperature of one kilogram of refractory material by one degree Celsius under constant pressure. It's significant for designing and controlling the heating process and heat storage capacity of furnaces.   These physical properties play essential roles in determining the performance and lifespan of refractory materials in glass melting furnaces. Therefore, they should be carefully evaluated when selecting refractory products for specific applications.

The configuration of refractory materials for the bottom of glass melting furnaces is crucial for withstanding the harsh conditions present in this area. Typically, the bottom of a glass melting furnace is only subject to erosion from the liquid phase and does not experience erosion from the glass liquid surface or the three-phase interface. However, erosion upwards can occur when the glass liquid reaches beneath the stratified refractory bricks. Erosion products on the furnace bottom tend to be retained on the surface of the refractory material due to gravity, to some extent, allowing for the use of refractory materials with poorer erosion resistance in this area. However, changes in the convection pattern of the liquid flow or variations in furnace load may lead to defects in the glass when using refractory materials with lower erosion resistance in this area.   Bubble formation from the bottom of the furnace is a common practice. Local turbulence generated by bubble action requires the use of refractory materials with better erosion resistance in this area. Typically, this involves the separate placement of thicker fused cast refractory materials from the customary brick paving of the furnace bottom. These thicker bricks, by preventing disturbance damage caused by stratified structures, contribute to a more balanced and consistent furnace lifespan. The presence of metallic impurities in glass batch materials has a significant impact on the furnace bottom structure. The furnace bottom is the area where metallic deposition into the furnace is most likely to occur. Metal deposited on the furnace bottom structure can corrode pores in the refractory material, similar to the upward erosion caused by glass liquid on refractory materials. Generally, metals with lower melting points exhibit higher and more significant rates of erosion compared to iron and its alloys. In some cases, metals can be directly reduced from the glass due to conditions within the furnace.   For glass melting furnaces producing high-alumina content glass, the furnace bottom structure is unique compared to general furnace bottom configurations in the glass industry, as there is a tendency for the bottom layer or overlying refractory materials to drift or float due to the high density of glass. Therefore, the optimal furnace bottom structure for melting high-lead glass is a single-layer furnace bottom made of a single refractory material. The most commonly used material for this purpose is fused cast zirconium-aluminum-silicate refractory material.

1.Refractory Cement: Refractory cement, also known as special cement, is produced by blending high-quality bauxite and high-quality lime into a suitable raw material mixture in specific proportions. After sintering, the resulting clinker primarily composed of aluminate is finely ground to produce a refractory hydraulic binder. In simple terms, refractory cement, a type of special cement, is used for high-temperature applications such as furnaces and chimneys due to its ability to withstand high temperatures and resist chemical erosion.   2.Ordinary Cement: Ordinary cement refers to the six major types of silicate cement commonly seen in general construction and concrete structures.   3.Based on their respective purposes, refractory cement is used for high-temperature fire resistance rather than for enhancing the strength of concrete under normal conditions. Therefore, in general, ordinary cement would have higher strength and can reach strengths of up to 62.5 MPa. Refractory mortar, also known as fire clay or joint material (powdered material), is used as joint material for refractory products. It consists of refractory powder and additives. Almost all refractory materials can be made into powders used to prepare refractory mortar.   Common refractory mortar, made by mixing refractory clinker powder with an appropriate amount of binder, has relatively low strength at room temperature, but it develops higher strength at high temperatures when it forms a ceramic bond. Refractory mortar can be classified into various types based on their refractoriness, including ordinary refractory mortar (580-1250°C), intermediate refractory mortar (1300-1770°C), high-grade refractory materials (1770-2000°C), and special-grade refractory materials (above 2000°C). They can also be classified according to their chemical properties as acidic, neutral, or alkaline refractory materials, with special refractory mortars used for specific applications.   Refractory cement, also known as aluminate cement, is made from bauxite and limestone, which are calcined to produce clinker primarily composed of calcium aluminate with an alumina content of approximately 50%. It is then finely ground to produce a hydraulic binder. Refractory cement is commonly yellow or brown, sometimes gray. Its main mineral components include calcium aluminate (CaO·Al2O3, abbreviated as CA) and other aluminates, as well as minor amounts of dicalcium silicate (2CaO·SiO2). Refractory cement is used to bond various refractory aggregates (such as corundum and calcined high-alumina bauxite) to produce refractory castables or concrete for lining industrial kilns. Under high temperatures, refractory cement forms low-melting compounds. Excessive use of refractory cement in refractory castables may reduce their high-temperature performance, and silica fume can be used to partially replace refractory cement in formulations.   The key difference between refractory mortar and refractory cement lies in their respective uses: refractory mortar is used as a joint material (mixed with water or other liquids) for laying refractory bricks, while refractory cement serves as a binder for various refractory aggregates to produce refractory castables used for lining kilns.    

Magnesia chrome bricks are divided into ordinary magnesia chrome bricks, direct-bonded magnesia chrome bricks, semi-bonded magnesia chrome bricks, fused magnesia chrome bricks, fused semi-bonded magnesia chrome bricks, and unfired magnesia chrome bricks. The difference between magnesia chrome bricks and direct-bonded magnesia chrome bricks lies in: 1. the purity of magnesite (raw material); 2. the sintering temperature. The sintering temperature of ordinary magnesia chrome bricks is between 1550°C and 1600°C, while the sintering temperature of direct-bonded magnesia chrome bricks is above 1700°C. When the temperature exceeds 1700°C, the microstructure of magnesia chrome bricks changes, with periclase directly bonding with chromite, hence termed as direct-bonded magnesia chrome bricks. Direct-bonded magnesia chrome bricks perform better in all aspects compared to ordinary magnesia chrome bricks.   Sintered magnesia bricks are made primarily from high-quality sintered magnesite sand as the main raw material, with pulp as the binder. After mixing and high-pressure forming, they are sintered in tunnel kilns at temperatures above 1550°C. They exhibit good thermal stability, erosion resistance, and spalling resistance. Widely used as refractory linings for industrial kilns such as converters and electric arc furnaces. Fused magnesia bricks have a dense brick structure, high mechanical strength, low impurity content, and are mainly used in the high-temperature areas of large glass kiln regenerators.   Magnesia brick is an alkaline refractory material with a magnesium oxide content of over 90%, mainly composed of periclase as the primary crystal phase. It can generally be divided into sintered magnesia bricks (also known as fired magnesia bricks) and chemically bonded magnesia bricks (also known as unfired magnesia bricks). Magnesia bricks with high purity and sintering temperature have periclase grains directly in contact, known as direct-bonded magnesia bricks; bricks made from fused magnesia sand are called fused re-bonded magnesia bricks.   Magnesia bricks have high refractoriness, excellent resistance to alkali slag, and a high starting temperature for load softening but poor thermal shock resistance. Sintered magnesia bricks are made from sintered magnesite sand as the main raw material, crushed, mixed, formed, and then sintered at temperatures between 1550°C and 1600°C, with the sintering temperature of high-purity products being above 1750°C. Unfired magnesia bricks involve adding appropriate chemical binders to magnesia sand, mixing, forming, and drying.   Sintered magnesia bricks are made primarily from high-quality sintered magnesite sand as the main raw material, with pulp as the binder. After mixing and high-pressure forming, they are sintered in tunnel kilns at temperatures above 1550°C. They exhibit good thermal stability, erosion resistance, and spalling resistance. Widely used as refractory linings for industrial kilns such as converters and electric arc furnaces.   Fused magnesia bricks have a dense brick structure, high mechanical strength, low impurity content, and are mainly used in the high-temperature areas of large glass kiln regenerators. Fused magnesia sand is made from high-quality magnesite sand melted down, also known as fused magnesite. It is obtained by high-temperature calcination of magnesite or magnesium hydroxide extracted from seawater. It has strong resistance to hydration.  

Refractory castable is a granular and powdery material made by adding a certain amount of binder to refractory materials. It has high fluidity and is suitable for forming amorphous refractory materials by pouring.   Compared with other amorphous refractory materials, refractory castables have higher binder and moisture content, hence better fluidity. They have a wide range of applications and materials and binders can be selected according to usage conditions. They can be directly cast into linings for use or made into prefabricated blocks using casting or vibration methods.   In cement plants, the use of castables is very extensive, in preheaters, kiln tails, tertiary air ducts, grate coolers, and so on, all require their use. Depending on different operating conditions, different types and models are used, including high-alumina alkali-resistant, anti-spalling, wear-resistant, and specialized for coal injection pipes, among many others. Cement is a powdery hydraulic inorganic binder. When mixed with water, it forms a slurry that can harden in air or better in water, bonding materials like sand and stone together firmly. Cement is an important building material, and mortar or concrete made from it is strong, durable, and widely used in civil engineering, water conservancy, national defense, and other projects.   Refractory cement, also known as aluminate cement, is made from bauxite and limestone, calcined to produce clinker mainly composed of calcium aluminate with an alumina content of about 50%, which is then ground into a hydraulic cementitious material. According to the national standard (GB201—2000), the density and bulk density of aluminate cement are similar to ordinary Portland cement. Its fineness is specified as specific surface area ≥300m2/kg or residue on a 45μm sieve ≤20%. Aluminate cement is divided into four types: CA-50, CA-60, CA-70, and CA-80, and the setting time and strength at various ages of each type of cement must not be lower than the standard requirements.

With the advancement of science and technology, various industries such as aerospace, nuclear energy, metallurgy, electronics, chemical engineering, construction materials, and transportation continually pose new challenges to refractory materials. The usage conditions are becoming increasingly harsh and specialized. Ordinary refractory materials cannot meet these new requirements. Only special refractory materials with high temperature resistance, corrosion resistance, and good performance in high-temperature chemistry and thermal stability can shoulder these responsibilities and meet the usage demands.   Special refractory materials encompass a wide range of categories, primarily including high-melting-point oxides, high-melting-point non-oxides and their derived composite compounds, metal ceramics, high-temperature coatings, high-temperature fibers, and their reinforcing materials. Among them, high-melting-point non-oxides are commonly referred to as refractory compounds, which include carbides, nitrides, borides, silicides, and sulfides.   Applications of Oxide Special Refractory Materials   1.Alumina (Corundum) Special Refractory Materials   Due to the excellent high-temperature performance and cost-effectiveness of alumina materials, they have the widest range of applications.   High-purity, high-density, high-performance corundum bricks are widely used in large blast furnaces and ladles in steel plants, achieving excellent results. They are the best lining materials for the secondary furnace and gasification furnace in large-scale synthetic ammonia plants (300,000 tons) and the cracking furnace in a 300,000-ton ethylene project.   High-temperature stable corundum bricks are the preferred lining materials for various ultra-high-temperature furnaces, such as special materials and products firing furnaces, molybdenum wire furnaces, tungsten rod furnaces, diffusion furnaces, ceramic metalization furnaces, siliconized molybdenum electric furnaces, etc. High-quality corundum bricks are also used in the hot air furnaces of magnetofluid generators. Alumina hollow ball products and alumina fiber products are high-temperature energy-saving products. Due to their low volume density and low thermal conductivity, they are ideal lining materials for energy-saving and consumption-reducing furnaces.   Precision alumina ceramics can be made into crucibles and pads for smelting or purifying non-ferrous, rare, and precious metals, high-temperature furnace tubes, thermocouple protection tubes, and insulating ceramic tubes, laser tubes, rectifier tubes, transparent sodium lamps. Tubes, radar antenna covers, microwave devices, sodium-sulfur battery shells, gas purifiers, and spark plugs.   Alumina ceramics, as wear-resistant and corrosion-resistant materials, can be used for metal liquid filters, high-temperature ceramics for physical and chemical analysis, and parts in the chemical and textile machinery industries, such as seals, valves, plungers, and catalyst carriers for petrochemicals.   Alumina ceramics can be used in nuclear energy for reactor insulation pads and in bioengineering to make artificial joints, artificial teeth, etc.   Due to the extremely high hardness of corundum materials, second only to diamonds, they are excellent wear-resistant materials. They can be made into various cutting and grinding tools, abrasives, wire drawing dies, towers for synthetic fiber drawing, grinding discs for grinding machines, wear-resistant and high-temperature bearings, ball mill liners, and grinding media, sandblasting nozzles, and high-temperature burners, among others.   2. Magnesium Oxide (Periclase) Special Refractory Materials   Magnesium oxide (periclase) is an alkaline refractory material with a high load softening temperature and low creep. Although it has a very high melting point of 2800°C, it is prone to volatilization in a reducing atmosphere, limiting its maximum usage temperature to 2000°C. It serves as an excellent structural material for ultra-high-temperature kilns and is also suitable for lining induction furnaces, medium-frequency furnaces, and high-frequency heating furnaces. High-purity magnesia bricks can be used as channel linings in magnetofluid generators.   Magnesium oxide ceramic products can be manufactured into magnesia crucibles for smelting and purifying non-ferrous, rare, and precious metals. They are also used as high-temperature furnace tubes, ultra-high-temperature tungsten-rhenium thermocouple protection tubes, and insulating ceramic beads.   3. Zirconium Oxide Special Refractory Materials   Zirconium oxide is an acidic refractory material with a melting point of 2650°C. Due to its excellent chemical stability at high temperatures, it can be used in various applications, including vacuum furnaces, molybdenum wire furnaces, gas furnaces, medium-high frequency electric furnaces, and single crystal furnaces. It serves as lining material for high-temperature furnaces, with a maximum usage temperature of up to 2400°C. In the metallurgical industry, it is used for casting nozzles and separation rings in continuous casting, and it can be employed in the production of insulation covers and linings in single crystal furnaces.   Zirconium oxide hollow spheres and zirconium oxide fiber products are currently the most energy-efficient insulation materials among oxide materials. They not only serve as insulation and thermal barrier materials in high-temperature furnaces but can also be used directly as lining materials.   High-temperature zirconium oxide ceramic products can be used to manufacture crucibles for smelting non-ferrous, rare, and precious metals, as well as high-temperature furnace tubes and thermocouple protection tubes. Additionally, they find applications in various high-temperature environments, such as oxygen control and temperature measurement in flues and molten steel, solid electrolytes for ceramic insulation engines, components for magnetic fluid generators, insulation and ablative materials for jet engines, missiles, rocket nozzles, spacecraft nose cones, and more.   Zirconium oxide high-temperature ceramics can also be used to make wire drawing dies, cutting tools, springs, high-temperature bearings, wear-resistant pads, corrosion-resistant pump parts, grinding media balls, and other components.   Special zirconium oxide refractory materials can also be used to produce heating elements for high-temperature electric furnaces, thermosensitive resistors, gas sensors, as well as spray coatings and castables for unshaped refractories. 4. Other Oxides (BeO, CaO, ThO2, CeO, SiO2) Special Refractory Materials   Beryllium oxide (BeO) is an alkaline special refractory material known for its high thermal conductivity, excellent thermal shock resistance, and low electrical conductivity. It possesses favorable nuclear properties, such as strong neutron deceleration ability and high X-ray penetration. However, due to its significant toxicity, its production and application are restricted. It can be used to manufacture containers for smelting rare metals and high-purity metals like Be, Pt, V, as well as neutron decelerators and anti-radiation materials for atomic reactors. In the electronics industry, it finds applications in high-frequency, insulation, and heat-dissipating devices.   Calcium oxide (CaO) is another alkaline special refractory material. While it has a high melting point, its susceptibility to hydration causing powdering limits its practical use. Its products can be employed as crucibles for melting platinum, special refractory materials for jet metallurgy, and other specialized refractories.   Thorium dioxide (ThO2) special refractory material, despite its high melting point of 3050°C, has radioactivity. It can be utilized as crucibles for smelting metals like uranium, osmium, rhodium, and radium, as well as fuel for atomic reactors and heating elements for ultra-high-temperature electric furnaces.   Cerium oxide (CeO) special refractory material, though it has a high melting point, is prone to reduction. Its products can be used as containers for smelting rare earth metals, low-resistance semiconductor devices, and grinding materials.   Silicon dioxide (SiO2) special refractory material, known for its extremely low linear expansion coefficient and excellent thermal shock resistance, finds applications in various industries. Fused quartz products can serve as conduits for transporting molten metal, linings for valves and pumps in non-ferrous metal smelting, and refractories for continuous casting. In the chemical industry, quartz materials are employed as acid-resistant and corrosion-resistant linings for containers and reactors. In the glass industry, quartz materials are used for melting tank bricks, arch flow rings, plungers, and thermal repair materials.   Application of refractory compound special refractory materials 1.Carbon and carbide products Carbon or graphite products are extensively used in the metallurgical industry, with the largest usage in blast furnace carbon bricks for components like the furnace bottom, hearth, and bosh. Carbon bricks are also employed in aluminum electrolytic cells, electric furnaces for producing iron alloys, acid pickling tanks in the electroplating industry, dissolving tanks in the paper industry, reaction tanks and storage tanks in the chemical industry, and high-pressure vessels in the petrochemical industry.   Graphite blocks and graphite electrodes serve as conductive electrode materials in various industrial electric furnaces for steel refining, aluminum electrolysis, magnesium electrolysis, nickel electrolysis, and electric fusion refractories. Due to the excellent conductivity of carbon or graphite products, they are also used to manufacture carbon heating elements.   There are various types of carbides, such as SiC, B4C, ZrC, TiC, WC, among which SiC, B4C, and WC are more commonly used. Silicon carbide (SiC) and its products find widespread applications due to their excellent properties. They are used to manufacture abrasives and grinding tools, non-metallic resistance heating elements, and special refractory materials. In metallurgical industries, silicon carbide products are utilized as lining materials for blast furnaces, and in non-ferrous metal (zinc, copper, aluminum) smelting, they are employed in distillation columns, molten metal conduits in electrolytic cells, suction pumps, crucibles, etc. In the electric porcelain and ceramics industry, silicon carbide products are used for the muffles, shelves, boxes, and other kiln furniture in flame-retardant kilns. Silicon carbide ceramics can be made into high-temperature furnace tubes, thermocouple tubes, radiation tubes, heat exchanger tubes, ceramic rolls, insulating engines, turbine blades, and sealing rings, among others. Silicon carbide products are excellent wear-resistant materials and can be used for making parts in paper machine components, air jet spinning nozzles, etc. In the chemical industry, various parts such as pipes, pumps, valves, etc., can be made from silicon carbide for reaction vessels. Silicon carbide can also be manufactured into heating elements, silicon carbide fibers, and whiskers. Boron carbide special materials Boron carbide special materials are mainly used for abrasives and grinding tools. They can also be used in metal smelting, crucibles for single crystal pulling, separation rings for horizontal continuous casting, metal casting molds, sheaths for thermocouples, control agents for atomic energy reactors, moderators, and cover materials for nuclear fuels.   2.Nitride Special Refractory Material   Silicon nitride special refractory material： In the metallurgical industry, it can be used to produce casting containers, pipes for transporting liquid metals, valves, pumps, thermocouple protection tubes, and crucibles, boats, and various lining materials for non-metallic smelting. Its high resistance to heat and impact makes it suitable for manufacturing lining materials for rocket nozzles, missile jet nozzles, and other components. In the mechanical industry, it can be made into turbine blades, turbo blades, and automotive engine blades. Utilizing its excellent wear resistance, it can be used to manufacture bearing balls and rollers, ceramic parts for high-speed textile machines, and cutting and grinding materials. In the building materials and ceramics industry, it can be used to make high-strength, long-life kiln furniture and saggers. Due to its properties as an electrical insulator and dielectric, it can be used as a thin film in integrated circuits.   Boron nitride special refractory material： Due to its high corrosion resistance, heat resistance, and resistance to thermal shock when exposed to molten metals, it can be used to make various containers for molten liquids, crucibles for pulling single crystals, thermocouple protection tubes, and pressure die-casting molds. Its electrical insulation properties make it suitable for use as a furnace lining material in magnetic fluid power generation devices, plasma flow furnaces, high-frequency electrical insulation materials, heat sinks for transistors and integrated circuits, and nozzles for ion rockets. Boron nitride can also be used as a lubricant and release agent, and cubic boron nitride grinding wheels exhibit superior wear resistance compared to those made with diamond.   Aluminum nitride special refractory material： As an excellent corrosion-resistant material, aluminum nitride can be used to make crucibles for melting metals, release agents, and protection tubes. In the aluminum refining industry, it is employed to make containers for aluminum vacuum evaporation. High-purity aluminum nitride can be used as containers for refining gallium arsenide and gallium phosphide, among other semiconductors.  

Refractory raw materials refer to the essential materials required for the production of refractory material products. They form the foundation for manufacturing refractory materials. The majority of refractory raw materials are natural minerals, such as refractory clay, high-alumina bauxite, silica, chromite, magnesite, kaolin, magnesia olivine, zircon, andalusite, silicon carbide, corundum, etc. With the continuous improvement in the comprehensive performance requirements of refractory materials, industrial raw materials and artificially synthesized materials, such as industrial alumina, synthetic mullite, artificial refractory fibers, and artificial refractory hollow spheres, are increasingly used in the production of refractory materials. The quality and cost-effectiveness of refractory products largely depend on the correct selection and rational utilization of raw materials.   Refractory raw materials can be classified based on their chemical properties into acidic refractory raw materials, alkaline refractory raw materials, and neutral refractory raw materials. They can also be categorized by their source into natural mineral raw materials and artificially synthesized raw materials. Generally, in the production of refractory materials, raw materials are further classified into primary materials and auxiliary materials.   The raw materials used to produce refractory products, whether natural mineral or artificially synthesized, must, from a mineralogical perspective, possess a sufficiently high refractoriness to meet the required product specifications. From a process perspective, they should meet the basic requirements of the manufacturing process. Considering the performance of the products derived from them, they should be able to meet the usage requirements of the products, especially the demands for high-temperature performance.   Refractory raw materials are commonly categorized as aluminum-silicon refractory raw materials (such as silica, clay, high-alumina, etc.), alkaline refractory raw materials, thermal insulating refractory raw materials, and other refractory raw materials.   1.Siliceous Raw Materials Due to the volume effect of quartz variants, silica bricks are also directly produced using siliceous rocks. Siliceous rocks encompass various types such as vein quartz, quartzite, flint, and sandstone. The main component in siliceous rocks is SiO2, with other components considered impurities. Siliceous raw materials used in refractory materials are broadly categorized into crystalline granules and bonded silica rocks.   2.Clayey Raw Materials Refractory clay is the primary raw material for producing alumino-silicate refractory materials, and its refractoriness requirements exceed various hard, soft (semi-soft) clays, and clay shale with a temperature resistance of over 1580°C, collectively referred to as refractory clay. Natural refractory clay typically consists mainly of clay minerals, with kaolinite (Al2O3 • 2SiO2 • 2H2O) as the primary component, representing hydrated silicates. It is accompanied by free quartz, limonite, goethite, and organic matter, forming a mixture. This non-uniform mineral is predominantly composed of dispersed particles with a diameter less than 1.2μm. Based on the different formation processes of clay, it can be classified into primary clay and secondary clay. Primary clay refers to clay formed by the weathering of parent rocks (such as feldspar) that remains in place after the weathering process. Secondary clay, also known as sedimentary clay, is clay that has been transported to other locations and redeposited under natural dynamic conditions. It has fine particle size, high dispersion, and high plasticity.   Refractory clays commonly used in the refractory materials industry can be broadly categorized into the following two types: (1).Hard Clay: Hard clay is characterized by a dense structure, high hardness, extremely fine particles, poor dispersibility in water, and very low plasticity. This type of clay often appears in light gray, gray-white, or gray. It has a shell-like fracture surface, some with a smooth and slippery feel, and is prone to weathering and breaking into fragments.   (2).Soft (Semi-Soft) Clay: Soft (semi-soft) clay usually exists in block-like forms, with a loose and soft structure and relatively good plasticity. The color of this type of clay varies significantly due to differences in the types and concentrations of impurities. It can range from gray and dark gray to black, and in some cases, it may exhibit purple, light red, or white colors. 3.High-Alumina Materials (1) Bauxite: Bauxite is the primary raw material for producing brown fused alumina. High-alumina clinker with an Al2O3 content of 88% to 90% serves as the main material for semi-friable corundum. For the production of white fused alumina, dense corundum, etc., aluminum oxide is used as the raw material. Bauxite is also known as high-alumina shale or alumina shale, with the main minerals being diaspore (Al2O3 • H2O) and boehmite (Al2O3•3H2O). China has extremely abundant reserves of bauxite, with production areas extending from Shanxi, Hebei, and Shandong north of the Yellow River, through Henan and Guangxi in the central region, to Guizhou and Yunnan in the southwest. The main production areas for high-alumina clinker in China are currently in Shanxi, Henan, and Guizhou. There are also some smaller mines under development in Hunan. The main minerals of high-alumina bauxite in China include diaspore, boehmite, kaolinite, and pyrophyllite. Based on their mineral composition, they are classified into three types: diaspore-kaolinite type (DK), boehmite-kaolinite type (BK), and diaspore-pyrophyllite type (DP). Among them, the DK-type high-alumina bauxite is the most widely used. The DK-type high-alumina clinker is further classified based on its Al2O3 content into grades S, I, IIA, IIB, III, etc. (2) Sintered Corundum and Fused Corundum Artificial production of corundum utilizes industrial alumina or high-alumina bauxite as the main raw materials and is melted in an electric arc furnace. In addition to this, corundum plate-like aluminum oxide can be produced using the sintering method. In this method, industrial alumina powder is the main raw material, and the process involves calcination, fine grinding, pelletizing, and sintering. This production method poses technical challenges, but the resulting products exhibit high strength, strong erosion resistance, and good thermal shock stability. The term "semi-friable corundum" essentially refers to dense fused corundum based on high-alumina bauxite, with an Al2O3 content exceeding 98% and an apparent porosity of less than 4%. It is produced by electric melting high-alumina bauxite under reducing atmospheres and controlled conditions. The corundum crystals are granular, typically ranging from 1 to 15 mm, with main impurities including hematite, aluminum titanate, and their solid solutions.   (3) Mullite Mullite is a refractory material primarily composed of the crystalline phase 3Al2O3•2SiO2. Mullite can be classified into two categories: natural mullite and synthetic mullite. Natural mullite is rare, and it is generally produced synthetically. Mullite exhibits stable chemical properties and is insoluble in hydrofluoric acid. It possesses excellent high-temperature mechanical and thermal properties.   Synthetic mullite and its products are characterized by high density, high purity, high temperature structural strength, low creep rate at high temperatures, small thermal expansion coefficient, strong resistance to chemical erosion, and resistance to thermal shock.   (4) Silimanite Group Minerals The silimanite group minerals include kyanite, andalusite, and sillimanite, commonly referred to as the "three stones." These minerals share the same chemical composition but have different crystal structures, classifying them as polymorphs. When heated to high temperatures, they all transform into mullite, producing a small amount of molten SiO2 accompanied by volume expansion.   Due to variations in the degree of thermal expansion among these minerals, their direct utilization differs. Because andalusite exhibits minimal volume change during heating, it is used directly in its raw state, either for brick making or as an additive. On the other hand, sillimanite and kyanite are often added in the form of expanding agents to the mix, particularly in the production of unshaped refractory materials. When used for brick making, they need to be fired into clinker, especially in the case of kyanite, which must be sintered into clinker form.   4.Alkaline Refractory Materials 4.1 Magnesia Materials (1) Magnesite Ore In China, magnesite ore is primarily classified into two types: crystalline magnesite ore and amorphous magnesite ore. The main distribution areas for magnesite ore are in the provinces of Liaoning and Shandong. The main impurity in magnesite ore is talc, and some magnesite ores also contain higher levels of CaO, with dolomite being the secondary mineral. In China, magnesite ore is graded into five levels (S, I, II, III, IV) based on its chemical composition. Only S and I grades are used for the calcination of magnesia sand to produce magnesia bricks.   Using a two-step flotation method and a two-step calcination method to prepare high-purity magnesia sand, the high-purity magnesia sand obtained through this process can be utilized as a raw material to develop various high-performance refractory products.   (2) Other Magnesium-Containing Minerals In magnesia refractory materials, products made from forsterite, the main mineral components are forsterite (2MgO·SiO2) and periclase (MgO). These products are characterized by a strong resistance to molten iron oxidation, and their thermal shock stability is superior to ordinary magnesia bricks. The primary raw materials for producing these products are dunite and serpentinite.   4.2 Dolomite Materials Dolomite is a refractory material primarily composed of a complex salt of magnesium carbonate (MgCO3) and calcium carbonate (CaCO3). Its chemical formula is CaMg(CO3)2 or MgCO3 • CaCO3, with a theoretical composition of CaO 30.41%, MgO 21.87%, CO2 47.72%. The CaO/MgO ratio is 1.39, and its hardness is 3.5 to 4.   China has abundant and widely distributed dolomite resources, known for their relative purity. The region around Dashiqiao in Liaoning Province has particularly rich reserves. Provinces such as Shandong, Hubei, Shaanxi, Guangxi, Gansu, Jiangxi, Anhui, Sichuan, Yunnan, and Hunan all boast abundant deposits. Dolomite deposits are often associated with limestone and magnesite. 5、Zirconium-based Product Raw Materials (1) Zircon Zircon (ZrO2·SiO2 or ZrSiO4) is the primary raw material for producing zirconium-based products and zirconia products. The main production site for zircon in China is Hainan Province. It is also found in Guangdong Province, Guangxi Zhuang Autonomous Region, Shandong Province, Fujian Province, and Taiwan Province. The theoretical composition of zircon is ZrO2 67.01%, SiO2 32.99%. It often contains trace elements such as Ti, Fe, and other rare earth oxides, imparting varying degrees of radioactivity. Therefore, necessary protective measures should be taken when using this raw material for product manufacturing.   Zircon has a relatively low thermal conductivity, measuring 3.72 W/(m·K) between 20 and 1000℃. Its coefficient of expansion is also comparatively low, reaching 4.6 × 10-6/℃ at 1000℃. The expansion coefficients in two directions, perpendicular and parallel to the main axis (C-axis), exhibit significant differences in single crystals. Zircon demonstrates high chemical inertness, resisting reactions with acids. It reacts to a lesser extent with glass melts and is commonly used in refractory materials for the metallurgical and glass industries.   (2) Monoclinic Zirconia Natural monoclinic zirconia (ZrO2) often appears as irregular blocks in black, brown, yellow, or colorless forms. Natural deposits of monoclinic zirconia are rare in China. The industrial-grade ZrO2, a chemical raw material, is obtained through chemical methods from zircon (ZrO2·SiO2) and appears as a white or slightly yellow powder. Pure ZrO2 has three crystal phases at atmospheric pressure: monoclinic, tetragonal, and cubic, in ascending order of temperature.   Stable ZrO2 can be further classified into partially stabilized ZrO2 and fully stabilized ZrO2, with the latter exhibiting a larger coefficient of thermal expansion and lower thermal shock stability than the former. Therefore, partially stabilized ZrO2 is often used as a toughening agent in ceramics and refractory materials.   (3) Desilicated Zirconia In the production of fused cast zirconia corundum (AZS) refractory materials abroad, in addition to using zirconium silicate concentrate, a certain amount of "desilicated zirconia" raw material is mostly added. The purpose is twofold: to adjust and stabilize the formula, and to improve and optimize product performance.   (4) Zirconia Corundum Mullite The original materials for this product are industrial alumina, kaolin, and zircon. They are finely ground, mixed uniformly, semi-dry pressed into balls, and sintered at 300 to 1700°C. Studies show that increasing the content of zircon leads to a higher sintering temperature, reduced total shrinkage, and increased closed pores. These reactions contribute to the sintered zirconia corundum mullite having higher density and strength, as well as better resistance to thermal shock stability. 6.Chromium-based Product Raw Materials   One of the primary raw materials for producing chromium-based refractory materials such as chrome bricks, chrome-magnesia bricks, and magnesia-chrome bricks is chromium ore or chromite. Chromite is a mixture of various minerals, and its composition fluctuates significantly, leading to variations in both chemical and physical properties. It typically consists of chromic grain minerals, with these minerals often being magnesium silicates, such as serpentine, forsterite, and olivine. In addition to Cr2O3, chromium iron ore also contains Al2O3, Fe2O3, MgO, etc. The general representation for chromite, due to the presence of magnesium and iron, is often expressed as (Mg, Fe) Cr2O3.   The mentioned materials are commonly used refractory raw materials. With the continuous advancement of refractory technology, the variety of raw materials has become more extensive. In recent years, there has been a focus on developing better-performing artificial synthetic materials and more environmentally friendly resource-recycled raw materials (such as silicon nitride iron and seelon), driven by environmental concerns and the depletion of natural resources.

Henan Rongsheng Technology Group Co., Ltd., supported by technology, is committed to becoming a global leading service provider of high-performance refractory new material solutions. It focuses on the research and development of efficient, energy-saving, environmentally-friendly refractory new materials, aiming to solve technical challenges in the field of refractory materials. The company continuously strengthens its independent research and development capabilities and builds a team of talents, striving to construct a new, efficient, energy-saving, emission-reducing, green and environmentally-friendly high-quality development system for refractory material enterprises. The factory of Henan Rongsheng Technology Group Co., Ltd. is located in Laiji Town, established in 2013. It is a refractory material production enterprise affiliated with Henan Rongsheng Technology Group Co., Ltd. With cross-border e-commerce as the leader, technology research and development as the foundation, product production as the basis, and kiln engineering services as the extension, it has a professional kiln construction team, an e-commerce center, overseas storage bases, a research and development center, etc. The company has the production capacity of 80,000 tons of shaped products and 50,000 tons of various unshaped refractory products annually. Its products cover a wide range of series including heavy-shaped, unshaped, lightweight-shaped, and unshaped, and are widely used in fields such as power, steel, non-ferrous, cement, glass, and chemical industries. In order to successfully achieve the annual goals, Henan Rongsheng Technology Group Co., Ltd. continues to increase investment in scientific research, adhering to technological innovation, and collaborating with multiple universities and research institutes for industry-academia-research cooperation. The company has organized and implemented over 20 research and development projects, including new product development, process technology research, energy-saving, and consumption reduction. Meanwhile, leveraging the advantages of the internet, the company has established a multi-platform, fully-networked, online and offline integrated marketing network model. Its products have not only quickly gained a foothold in the domestic market but also expanded to international markets. Currently, the company's products are exported to 105 countries and regions, achieving significant economic and social benefits.