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

Phosphate-Bonded Refractory Castables The composition of phosphate-bonded refractory castables is similar to that of general castables. Aggregates and powders include high-alumina, clay, silica, and magnesia. Phosphates such as aluminum phosphate and phosphoric acid react slowly with neutral and acidic aggregates and powders at room temperature. To enable hardening at room temperature, hardeners like active aluminum hydroxide, talc, ammonium fluoride, magnesium oxide, alkaline aluminum chloride, and calcium aluminate cement are added. Magnesium oxide is particularly effective as a hardener, but the resulting magnesium phosphate reduces refractoriness and lowers hot strength. The hardening time varies significantly with ambient temperature. When phosphates react with aggregates, the formation of insoluble products can lead to aging effects. Reactions involving iron content in raw materials may also impact aging. Additionally, the mixing process can corrode mixing equipment, necessitating the addition of aging inhibitors and mitigating additives.   Phosphate-bonded castables must be dried at 450–500°C to form aluminum phosphate or metaphosphates. At lower drying temperatures, hygroscopic compounds such as pyrophosphoric acid (H₄P₂O₇) may form, which absorb moisture from the air and revert to orthophosphoric acid, compromising bonding properties. Aluminum Sulfate-Bonded Refractory Castables Common aluminum sulfate solutions have a density of 1.20–1.30 g/cm³ and are added in amounts ranging from 12% to 18%. Being acidic, these solutions contain sulfate and bisulfate ions, which react with iron and other components in aggregates and powders, releasing hydrogen gas and causing expansion. To counteract this, the material is left to rest for over 24 hours before forming. Initially, 70–80% of the total aluminum sulfate solution is added, with the remainder added after resting.   After forming, the castables are naturally cured in dry air and at 50°C for three days to meet strength requirements. Accelerators such as bauxite cement (2–4%) can be added to speed up hardening. To enhance high-temperature performance, 5–10% of fine clay powder or expansion agents can be incorporated to counteract shrinkage. The strength of aluminum sulfate-bonded castables fluctuates with temperature. At room temperature, hardening is slow, but with the addition of accelerators, compounds like calcium sulfate, ferric sulfate, and magnesium sulfate form. These compounds interact to produce needle-like or columnar precipitates (e.g., calcium sulfoaluminate or aluminoferric sulfate), promoting hardening. At 500–600°C, the strength remains similar to that after drying. However, at 700–800°C, decomposition of aluminum sulfate and its salts releases SO₂ gas, reducing density and strength. Above 1000°C, active Al₂O₃ from decomposition reacts with SiO₂, forming mullite and other compounds, which significantly increase strength.   To address the structural loosening and strength reduction around 800°C, composite binders with 25–50% phosphoric acid can be used. The service temperature of aluminum sulfate-bonded castables depends on the material type: clay-based at 1300–1350°C, high-alumina at 1350–1550°C, and corundum-based at 1500–1650°C. Sodium Silicate-Bonded Refractory Castables Sodium silicate-bonded castables use aggregates and powders from diverse sources, including aluminosilicate, silica, semi-silica, magnesia, and magnesia-alumina materials. Due to the high viscosity of sodium silicate, mixing and vibration times are extended. In the 1970s, fast-dissolving solid sodium silicate was introduced, allowing refractory aggregates and powders to be mixed on-site with water for convenient casting. However, at 800–1000°C, sodium fluoride and sodium oxide melt, increasing the liquid phase and reducing the effect of silica gel, leading to lower softening temperatures under load. The service temperature of sodium silicate-bonded castables is relatively low: 1400°C for high-alumina, 1000°C for clay and semi-silica, and 1600°C for magnesia. To address these limitations, the addition of sodium silicate and sodium fluosilicate must be minimized, or high-modulus sodium silicate should be used.   Despite these challenges, sodium silicate-bonded castables exhibit high room-temperature strength and minimal strength reduction during heating, providing excellent high-temperature wear resistance. They are particularly effective in resisting acid media (except hydrofluoric acid) and sodium salt melts. The acid resistance of clay and semi-silica sodium silicate castables exceeds 93%, meeting the requirements for acidic thermal equipment. About Us Henan Rongsheng Xinwei New Materials Research Institute Co., Ltd. is affiliated to Henan Rongsheng Refractory Group and we have been a leading manufacturer and supplier of high-performance refractory materials for more than 20 years. As a national high-tech enterprise, we specialize in research, development, production, and technical services of advanced refractory materials.   Our product range includes refractory castables, high-alumina bricks, corundum bricks, AZS bricks, fireclay bricks, insulating bricks, and unshaped materials such as refractory cement and mortar. These products serve industries like iron and steel, cement, glass, petrochemical, and non-ferrous metals, with exports to over 100 countries worldwide.   We are committed to providing innovative, energy-efficient, and environmentally friendly solutions for high-temperature industries.   Contact Us Today!

In the early 1970s, Lafarge in France successfully developed low cement castables, followed by the development of ultra-low cement castables, which gained global application in the 1980s. In China, there is no unified standard for categorizing these castables. According to ASTM standards in the United States, they are defined based on the CaO content in the product.   Unlike conventional refractory castables, low cement and ultra-low cement castables partially or largely replace calcium aluminate cement with ultrafine powders of the same or similar chemical composition as the castable's main material. Additionally, small amounts of dispersants (water reducers) and delayed-setting accelerators are added. Cement-free castables use ultrafine powders or oxide sol entirely as binders.   The setting and hardening mechanisms of low cement, ultra-low cement, and cement-free castables differ from those of conventional calcium aluminate cement. While traditional cement relies primarily on hydration bonding, low cement castables exhibit both hydration and coagulation bonding, ultra-low cement castables are predominantly coagulation-bonded, and cement-free castables rely entirely on coagulation bonding. The principle behind coagulation bonding is as follows: in silica-alumina castables containing SiO₂ ultrafine powder, mixing the powder with water forms colloidal particles due to the high activity of SiO₂ ultrafine powder. The surface of these colloidal particles dissociates Si-OH groups into Si-O⁻ and H⁺, giving the particles a negative charge. These negatively charged particles adsorb Al³⁺ and Ca²⁺ ions slowly released during the hydrolysis of calcium aluminate, leading to a decrease in the zeta potential of the colloidal particles. When adsorption reaches the isoelectric point (where the colloidal particles are neutral), coagulation occurs, forming bonds that harden through drying. Advantages of Low Cement, Ultra-Low Cement, and Cement-Free Castables: Reduced CaO Content: Lower CaO content reduces the formation of low-melting phases, enhancing refractoriness, high-temperature strength, and slag resistance, with cement-free castables offering superior performance. Lower Mixing Water Requirement: The water needed for mixing is only 1/2 to 1/3 of that for conventional refractory castables (about 4%–6%), resulting in lower porosity and higher bulk density. Improved Strength: After forming and curing, minimal or no cement hydration products are generated. This avoids significant strength reduction due to the breakdown of hydration bonds during heating. Instead, strength gradually increases with sintering at higher temperatures. Aggregate and Powder Materials Low cement, ultra-low cement, and cement-free castables can use aggregates and powders made of clay, high alumina, mullite, corundum, carbon-containing materials, or silicon carbide. The choice of binders such as ultrafine powder or silica/alumina sol depends on the chemical composition of the aggregate. For example: Corundum-based castables should use alumina ultrafine powder or a combination of alumina and silica ultrafine powder. Silica-alumina castables can use silica ultrafine powder alone, a combination of silica and alumina ultrafine powder, or silica sol as the binder. These innovative castables represent a significant advancement in refractory material technology, providing enhanced performance and broader applications across high-temperature industries.

Detailed Analysis of the Classification of Refractory Properties and Their Application Fields 1. Detailed Classification of Properties 1.1 Chemical Composition and Mineral Composition Silica Refractories: Primarily composed of silicon dioxide (SiO₂), silica refractories have excellent acid slag resistance and are commonly used in blast furnaces, hot blast stoves, and coke ovens. Aluminosilicate Refractories: Composed of alumina (Al₂O₃) and silicon dioxide, these refractories offer good heat resistance and thermal shock stability, making them widely used in high-temperature equipment such as blast furnaces, hot blast stoves, and glass melting kilns. Corundum Refractories: Made from high-purity alumina (Al₂O₃), corundum refractories exhibit a high melting point, high hardness, high strength, and excellent chemical stability, suitable for a variety of high-temperature industrial kilns. Magnesia Refractories: Composed mainly of magnesium oxide (MgO), magnesia refractories offer excellent alkali slag resistance and are commonly used in steelmaking converters, electric furnaces, and other alkaline environments. Chromium Refractories: Made from chromium oxide (Cr₂O₃), chromium refractories provide superior high-temperature and oxidation resistance, suitable for industrial kilns operating in high-temperature oxidative atmospheres. Carbon Refractories: Composed of carbon, carbon refractories maintain structural stability and resist deformation at high temperatures, commonly used in blast furnaces, converters, and other areas subject to high-temperature shock. Zirconium Refractories: Made from zirconium oxide (ZrO₂), zirconium refractories have an extremely high melting point and excellent chemical stability, ideal for industrial kilns operating in ultra-high temperatures and corrosive environments. 1.2 Physical Properties and Functional Characteristics High-Temperature Stability: Refractory materials can maintain their physical and chemical properties at high temperatures without significant deformation or melting. Corrosion Resistance: The ability of refractory materials to resist acids, alkalis, salts, and other chemical media, including slag resistance and permeability. Thermal Shock Resistance: Refractories maintain structural integrity and performance stability despite rapid temperature changes, preventing cracking or spalling. Thermal Conductivity: The heat conductivity of refractory materials varies depending on their composition and structure, used to control heat transfer and distribution. Density and Porosity: The density and porosity of refractory materials significantly impact their performance. Lightweight refractories have lower density and higher porosity, suitable for insulation, while dense refractories, with lower porosity, are used in high-temperature and heavy-load environments. 2. Detailed Analysis of Application Fields 2.1 Construction Industry In the construction industry, refractory materials improve the fire resistance and safety of buildings. Materials like fire-resistant walls, doors, and windows help prevent the spread of fire, while refractory coatings and fire-resistant glass enhance the fire performance of building components. 2.2 Metallurgical Industry The metallurgical industry is a primary field for the application of refractory materials. Refractories are used as linings and insulating layers in high-temperature equipment such as blast furnaces, hot blast stoves, converters, and electric furnaces to protect the furnace body from high-temperature and slag erosion. Additionally, refractories are used for linings in slag pots and ladles during the smelting process. 2.3 Glass and Ceramic Industries Glass melting furnaces and ceramic firing kilns are key application areas for refractory materials. In glass melting furnaces, refractories are used in parts such as the melting pool, flow channels, and clarification pools for insulation and load-bearing. In ceramic kilns, refractories are used for the walls, roof, and bottom to provide insulation and heat retention. 2.4 Chemical and Petrochemical Industries High-temperature, high-pressure equipment and reactors in the chemical and petrochemical industries often use refractories as linings and insulating layers. Refractory materials in devices like cracking furnaces, hydrogenation reactors, and synthesis towers resist high temperatures and corrosive media, ensuring stable operation of equipment. 2.5 Power Industry In the power industry, boilers, steam turbines, and generators widely use refractories. Refractories improve heat efficiency and reduce heat loss in the furnace chambers, flue gas ducts, and water-cooled walls of boilers, while high-temperature components in steam turbines rely on refractories to withstand high temperatures and friction from high-speed rotation. 2.6 Aerospace and New Energy Industries In the aerospace industry, high-temperature components such as rocket engines and aircraft engines use refractory materials to enhance heat resistance and stability. For example, refractory materials are used in rocket engine nozzles and combustion chambers to withstand high temperatures and high-speed airflow erosion, while turbine blades in aircraft engines use refractory alloys or composites to improve high-temperature and oxidation resistance. In the new energy sector, refractory materials improve the thermal stability and lifespan of components such as solar panels and fuel cells. For instance, the backplates of solar panels use refractories to prevent deformation and aging under high temperatures, and electrolytes and electrodes in fuel cells are made from refractory materials to enhance high-temperature and corrosion resistance. With over 20 years of experience as a leading manufacturer and supplier of refractory materials, we offer a wide range of high-performance products designed to meet the demands of various industries, including steel, cement, glass, petrochemical, and energy. Whether you require silica, aluminosilicate, magnesia, corundum, or other specialized refractory products, we have the expertise and resources to provide solutions that ensure long-lasting durability and efficiency.   Contact us today for more information and inquiries!   Tel/Whatsapp: +86-13903810769 Email: Jackyhan2023@outlook.com Website: https://www.bricksrefractory.com   Let us help you find the perfect refractory solution tailored to your needs!

Refractory Materials for Steel Rolling Reheating furnaces and soaking pits in steel rolling extensively use monolithic refractory materials as replacements for traditional brick linings. Among monolithic refractories, the proportion of castables has increased, while the use of plastics has decreased. To conserve energy, refractory fibers are widely applied in reheating furnaces and soaking pits. 1. Reheating Furnaces Reheating furnaces are thermal equipment used to heat steel billets or small steel ingots, typically operating at temperatures of 1300–1400°C. The furnace lining is primarily constructed with fireclay bricks or third-grade high alumina bricks, which are subject to damage from high temperatures, thermal stress, gas flow erosion, and mechanical impacts. In high-temperature zones, the lower parts of the furnace walls, the furnace bottom, and the water-cooled pipe wrapping layers also suffer corrosion from molten iron oxide slag. To counter this, magnesia bricks or magnesia sand are used as protective layers. Since the 1970s, monolithic refractory materials have been progressively applied. Gas-fired reheating furnaces use crystalline alumina fiber or aluminosilicate fiber products as the working layer, achieving significant energy-saving effects. (1) Furnace Body Initially constructed with fireclay bricks, the furnace body was later replaced with castables bonded with high alumina cement or phosphates. After 1980, clay-bonded or low-cement castables became widely adopted. In high-temperature zones and furnace bottoms, erosion-resistant corundum, mullite, or magnesia-chrome refractory castables are used, while wear-resistant steel-fiber-reinforced castables are applied on soaking beds. (2) Combustion Chamber Corundum, super-grade high alumina clinker, or magnesia-alumina spinel castables are used in combustion chambers, offering lifespans 2–3 times longer than traditional brick linings. Other areas where castables have been implemented show significantly improved performance. 2. Soaking Pits Soaking pits are thermal equipment used in primary rolling mills to heat and homogenize steel ingots. The furnace body and roof are subject to rapid temperature fluctuations, mechanical wear, impacts, and slag corrosion. High-alumina plastics or clay-bonded high-alumina castables are employed. For the furnace mouth, corundum and mullite low-cement or cement-free castables greatly enhance service life. The checkerwork in the regenerator uses grid bricks, with the upper part made of high-alumina bricks and the lower part using fireclay bricks. The heat exchanger, originally constructed with fireclay or fireclay-silicon carbide bricks, is now made with high-alumina silicon carbide castables, increasing service life by 50%.

Commonly Used High Alumina Bricks For Industrial Kilns High alumina bricks are essential refractory materials widely applied across various high-temperature industrial fields due to their excellent refractory performance, corrosion resistance, and thermal stability. Below is a detailed introduction to commonly used high alumina bricks for industrial kilns: 1. Definition and Characteristics of High Alumina Bricks High alumina bricks are refractory bricks with a high alumina (Al₂O₃) content, typically exceeding 48%. Their key characteristics include: High Temperature Stability: Operate stably under high-temperature environments, resisting deformation or damage caused by thermal expansion or contraction. Corrosion Resistance: Effectively resist chemical corrosion from acids, alkalis, and other agents. Wear Resistance: With a high surface hardness, they maintain long service life even under abrasive conditions. High Strength: Excellent compressive and flexural strength to endure significant mechanical and thermal stress. At Rongsheng Refractory, we specialize in manufacturing high-quality high alumina bricks designed to meet these demanding requirements. Our products are known for their exceptional durability and precision-engineered performance, making them the preferred choice across industries. 2. Manufacturing Process of High Alumina Bricks The production of high alumina bricks involves several precise steps: Batching: Selecting raw materials and adjusting the composition to achieve the required Al₂O₃ content and performance indicators. Forming: Utilizing advanced machinery to shape bricks with consistent dimensions and strength. Firing: Bricks are fired in high-temperature kilns to achieve the desired density and mechanical properties. Rongsheng's state-of-the-art production facilities and stringent quality controls ensure that every high alumina brick we produce meets international standards and the specific needs of our clients. 3. Applications of High Alumina Bricks in Industrial Kilns High alumina bricks from Rongsheng Refractory are trusted in a wide range of industrial kilns, including ceramic kilns, glass kilns, steel blast furnaces, and hot blast stoves. Specific applications include: Ceramic Kilns: Used as kiln linings, our high alumina bricks withstand extreme temperatures and chemical erosion, ensuring stable kiln operations and high-quality ceramic products. Glass Kilns: Providing structural stability and resistance to high-temperature flames and molten glass, our bricks play a critical role in glass production. Steel Blast Furnaces: With outstanding refractory performance, our high alumina bricks protect blast furnaces and hot blast stoves from extreme temperatures and chemical erosion. Other Industrial Kilns: In cement, chemical, and power industries, Rongsheng high alumina bricks deliver superior performance: Cement Industry: Ideal for rotary kilns and preheaters. Chemical Industry: Reliable linings for high-temperature reactors and heat exchangers. Power Industry: Key components in boilers and flue systems. 4. Development Trends of High Alumina Bricks As industrial needs evolve, high alumina bricks continue to see advancements in performance and applications. Future trends include: Green and Sustainable Manufacturing: At Rongsheng, we prioritize environmentally friendly and sustainable production methods. High Performance: Our R&D focuses on optimizing material properties to enhance resistance to heat, corrosion, and wear. Diversification: We offer a wide range of specifications to meet diverse customer needs. Intelligent Manufacturing: Leveraging automation and advanced control systems, we ensure consistent product quality while reducing costs. Why Choose Rongsheng Refractory? With over 20 years of expertise, Rongsheng Refractory is a global leader in the manufacturing, supply, and export of premium refractory materials. Our extensive product range includes high alumina bricks, corundum bricks, insulating bricks, and unshaped materials such as refractory castables and cement. Our products cater to 90% of the refractory needs in industries such as Iron & Steel, Cement, Non-ferrous, Power, Petrochemical, and Glass. Exported to over 100 countries, our high alumina bricks have earned a reputation for reliability and excellence.   For inquiries, contact us at: Tel/Whatsapp: +86-18538509097 Email: Jackyhan2023@outlook.com   Choose Rongsheng Refractory for durable, high-performance high alumina bricks that meet the challenges of modern industrial kilns. Let us be your trusted partner in achieving operational excellence.

Application of Ladle Castables Ladle castables are specialized refractory castables designed for use in steel ladles. With their excellent performance, they have found widespread application across various fields. Below is a detailed summary of their applications: I. Main Application Areas Steel Ladle Linings Ladle castables are primarily used as linings for steel ladles, including the bottom, sidewalls, and slag line. These areas come into direct contact with high-temperature molten steel and slag, requiring exceptional refractory properties and resistance to erosion. Ladle castables protect the ladle structure from damage caused by high temperatures and slag erosion, thereby extending the service life of the ladle. Metallurgical Furnaces Ladle castables are widely used in various metallurgical furnaces, such as reheating furnaces and soaking pits. These furnaces operate under high temperatures and demand outstanding refractory performance and stability. Ladle castables meet these requirements, ensuring the safe and efficient operation of the furnaces. Other Smelting Industries In industries such as petroleum, chemical, building materials, and power, ladle castables are also extensively used. They can serve as linings or coatings for various high-temperature equipment, enhancing their thermal resistance and extending their service life. II. Specific Application Scenarios Ordinary Steel Ladles Ladle castables are suitable for working linings of ordinary steel ladles, improving their resistance to high temperatures and erosion. They protect the ladles from damage caused by molten steel and slag, thereby prolonging their lifespan. Refining Steel Ladles During the refining process, steel ladles are subjected to higher temperatures and more complex chemical environments. Ladle castables can withstand these harsh conditions, maintaining the integrity and stability of the ladles. Electric Furnace Ladles Electric furnace ladles generate substantial heat and slag during operation. Ladle castables provide resistance to high temperatures and slag erosion, safeguarding the structural integrity of the ladles. Other Equipment Ladle castables can also be used for applications like tundish refractory nozzle inserts, prefabricated ladle stopper heads, and other scenarios. Additionally, they can be shaped into cast bricks to meet the needs of various high-temperature equipment. III. Advantages of Application High Refractoriness Ladle castables offer excellent refractoriness, capable of withstanding high-temperature molten steel and slag erosion. Strong Erosion Resistance They exhibit superior slag resistance and anti-spalling properties, maintaining the integrity of the ladle lining over time. High Adhesion Rate and Easy Repairs Ladle castables have a high adhesion rate, making them less prone to detachment and easy to repair through spraying. This reduces maintenance costs and enhances equipment efficiency. Excellent Workability With good construction performance, ladle castables are easy to apply and shape, ensuring accuracy and efficiency during installation. Improved Smelting Efficiency By selecting appropriate ladle castable materials and employing efficient installation methods, heat storage and thermal losses in steel ladles can be reduced. This lowers energy consumption and production costs for steel plants while improving smelting efficiency and ensuring the stability of molten steel quality. In conclusion, ladle castables demonstrate significant application value across various fields and specific scenarios. Their high refractoriness, strong erosion resistance, high adhesion rate, ease of repair, and excellent workability make them an ideal material for high-temperature environments.

Classification Methods of Lightweight Castables Lightweight castables can be categorized in various ways. Below are some of the main classification methods: 1. Classification by Porosity Dense Castables: Feature relatively low porosity, offering higher strength and density. Insulating Castables: Have a porosity of no less than 45%, mainly used for insulation and heat preservation to effectively reduce thermal conductivity. 2. Classification by Binder Type Hydraulic Bonded Castables: These harden at room temperature through hydration. Key varieties include castables made with silicate cement, ordinary calcium aluminate cement, pure calcium aluminate cement, and fused calcium aluminate cement. Chemically Bonded Castables: Harden at room temperature via chemical reactions initiated by additives. Common examples include castables bonded with water glass, aluminum sulfate, and phosphate. Cohesively Bonded Castables: Harden through sintering during the firing process. The primary example is clay-based castables. 3. Classification by Refractory Aggregate Clay-Based Aggregates: Contain 30%–45% alumina. High-Alumina Aggregates: Contain no less than 45% alumina. Silica-Based Aggregates: Contain no less than 85% silica and less than 10% alumina. Basic Aggregates: Typically include magnesia and dolomite. Special Aggregates: Include materials such as carbon, carbides, spinel, zircon, and nitrides. Insulating Aggregates: Examples include perlite, vermiculite, ceramic spheres, cenospheres, lightweight brick sand, porous clinker, and hollow alumina spheres. 4. Classification by Bulk Density Semi-Lightweight Refractory Castables: Have a bulk density of 1.0–1.8 g/cm³. Lightweight Refractory Castables: Have a bulk density of 0.4–1.0 g/cm³. Ultra-Lightweight Refractory Castables: Have a bulk density of less than 0.4 g/cm³. 5. Classification by Operating Temperature Low-Temperature Insulating Refractory Castables: Suitable for use at 600–900°C. Medium-Temperature Insulating Refractory Castables: Suitable for use at 900–1200°C. High-Temperature Insulating Refractory Castables: Suitable for use at temperatures above 1200°C. In practical applications, lightweight castables can also be tailored to specific engineering requirements by incorporating mixed aggregates or special composite materials such as carbon fibers to achieve specific functional needs. Conclusion In summary, lightweight castables can be classified using diverse methods, each with unique advantages and applicable scenarios. Selecting the appropriate type of lightweight castable requires consideration of the specific operating environment and project requirements.

Refractory materials with good thermal shock resistance should possess the following key properties: 1. Stable Chemical Composition and Microstructure Stable Chemical Composition: The chemical composition of refractory materials should remain stable without decomposition or phase changes at high temperatures, avoiding additional thermal stress. Uniform Microstructure: The grain size, shape, and distribution should be uniform to prevent localized stress concentration. Additionally, an appropriate amount of microporous structure helps to quickly conduct and release heat, mitigating stress caused by sudden temperature changes. 2. Excellent Thermal Physical Properties Low Thermal Expansion Coefficient: A low thermal expansion coefficient minimizes thermal stress during temperature fluctuations, enhancing thermal shock resistance. High Thermal Conductivity: High thermal conductivity ensures rapid heat balance within the material, reducing local overheating and stress concentration, thereby improving thermal shock resistance. 3. High Strength and Toughness High Compressive Strength: The material should withstand high-temperature pressure without deformation or failure. High Toughness: Good toughness enables the material to absorb energy through plastic deformation when subjected to thermal stress shocks, preventing brittle fracture. 4. Good Performance in Thermal Shock Testing Stable Performance After Multiple Thermal Cycles: The material should withstand repeated thermal cycles without significant performance degradation. Low Thermal Shock Damage: Indicators such as the degree of surface damage, mass loss rate, and strength loss rate after testing should remain at low levels. 5. Adaptability to Complex Working Environments Resistance to Sudden Temperature Changes: In industrial production, refractory materials often face environments with abrupt temperature fluctuations, requiring excellent thermal shock resistance. Slag Resistance and Corrosion Resistance: In addition to thermal shock resistance, refractory materials should have superior slag and corrosion resistance to ensure long-term stability at high temperatures. 6. Performance in Practical Applications Long Service Life: Refractory materials with good thermal shock resistance typically have a longer service life, reducing the frequency of replacement and maintenance. Improved Production Efficiency: Stable refractory material performance contributes to the efficient operation of industrial furnaces and improved production quality. In conclusion, refractory materials with good thermal shock resistance should feature stable chemical composition and microstructure, excellent thermal physical properties, high strength and toughness, reliable performance in thermal shock tests, and adaptability to complex working environments. These properties collectively determine the stability and reliability of refractory materials in high-temperature and frequently fluctuating industrial environments

There are numerous types of commonly used refractory castables. Based on different classification criteria, they can be categorized into various types. Below are some common types of refractory castables: Classification by Binding Method 1.Hydraulic Binding Refractory Castables Silicate Cement-Bonded Refractory Castables: These are prepared using ordinary silicate cement, slag silicate cement, etc., as binders, combined with refractory aggregates and powders. They are suitable for use at temperatures of 700–1200°C and can be applied in integral load-bearing heat-resistant structures and kiln linings. Aluminate Cement-Bonded Refractory Castables: Known for their rapid hardening, high strength, good thermal shock resistance, and high refractoriness, they can be used at temperatures up to around 1800°C and are widely applied in industries such as metallurgy and petrochemicals. Low Cement Refractory Castables: With calcium aluminate cement content below 8%, they feature high density, low porosity, and high strength, making them suitable for applications like blast furnace iron troughs and steel ladles. Ultra-Low Cement Refractory Castables: With even lower cement content than low-cement castables, they exhibit superior performance and are widely used in high-temperature areas such as blast furnace iron troughs. Chemical Binding Refractory Castables Sodium Silicate-Bonded Refractory Castables: These are air-hardening refractory materials prepared using sodium silicate as a binder and various refractory aggregates. They feature minimal strength loss at high temperatures, good thermal shock resistance, excellent high-temperature wear and corrosion resistance, and a maximum service temperature of 1400°C. Phosphoric Acid and Phosphate-Bonded Refractory Castables: These are new refractory materials made by combining phosphoric acid or phosphate solutions with refractory aggregates and powders in specific proportions, offering excellent performance.   Classification by Aggregate Material Silica Refractory Castables: Use silica stone and quartz sand as primary raw materials. Semi-Silica Refractory Castables: Contain silica and clay-based raw materials. Clay Refractory Castables: Use clay and shale as primary raw materials, suitable for temperatures of 700–1200°C, and applicable in integral load-bearing heat-resistant structures and kiln linings. High-Alumina Refractory Castables: Use high-alumina bauxite and alumina as primary raw materials. They are commonly used in kiln linings with temperatures exceeding 1300°C, offering low cost and high overall strength. Corundum Refractory Castables: Use corundum as the primary raw material, featuring high strength, excellent slag resistance, and a service temperature of 1500–1800°C. Magnesia Refractory Castables: Use magnesia and magnesite as primary raw materials. Spinel Refractory Castables: Use spinel as the primary raw material. Special Aggregate Refractory Castables: Include silicon carbide, chrome slag, zircon sand, etc. Classification by Performance Characteristics High-Strength Wear-Resistant Castables: These unburned refractory materials have slightly lower refractoriness than fired refractory products but feature high ambient temperature strength and excellent resistance to cracking. Lightweight Insulating Refractory Castables: Comprising lightweight porous refractory materials as aggregates and admixtures, these mixtures are combined with binders and water during construction. They are characterized by low weight, low bulk density, and low thermal conductivity, making them ideal for furnace insulation layers and inner linings of furnace covers. Non-Stick Aluminum Castables: Made with high-purity mullite, andalusite, and sillimanite as base materials, they feature high bulk density, high strength, and good thermal shock resistance. Adding appropriate non-wetting agents significantly reduces the wettability of aluminum and alloys on refractory materials. Self-Flowing Refractory Castables: Known for excellent construction and usage performance, these are primarily used in complex high-temperature industrial kiln structures that are difficult to construct. Classification by Application Areas Special Castables for Kiln Mouths: Applied at kiln heads and tails of rotary kilns, these refractory materials feature good thermal shock resistance, easy kiln skin adhesion, and wear resistance. Special Castables for Steel Ladles: Such as corundum-spinel prefabricated blocks made from fused white corundum, tabular corundum, and sintered magnesium-aluminum spinel, offering high strength, erosion resistance, and spalling resistance. Special Castables for Boiler Furnaces: Made from high-quality calcined bauxite aggregates, calcium aluminate cement, and microsilica powder as binders, with the addition of silicon carbide wear-resistant particles and dispersants. In conclusion, there is a wide variety of commonly used refractory castables, each with unique characteristics and applications. When selecting refractory castables, it is essential to consider the specific use environment and requirements to make an appropriate choice.

Chrome corundum, as a traditional material for ladle porous bricks, has played a crucial role for a long time. However, as previously mentioned, the insufficient thermal shock resistance of traditional chrome corundum bricks often leads to cracks during use. These cracks allow molten steel to easily penetrate the brick, resulting in steel infiltration, which can severely impact the argon-blowing performance. Additionally, chromium poses environmental pollution concerns. As a result, chrome corundum porous bricks have gradually been replaced by corundum-spinel porous bricks with superior performance. However, chrome corundum porous bricks still exhibit better structural stability and slag penetration resistance compared to corundum-spinel porous bricks. The material of chrome corundum is primarily made from sintered tabular corundum with a dense structure, low porosity, and easy sinterability. As shown in Table 1, there are some performance differences between the two types of porous bricks. Generally, under the same particle size distribution, the bulk density of corundum-spinel porous bricks is smaller than that of chrome corundum porous bricks. The porosity of corundum-spinel porous bricks is lower than that of chrome corundum porous bricks due to the volume expansion caused by spinel formation during sintering, which offsets some of the shrinkage caused by fine powders, thus reducing the porosity.   On the other hand, the linear dimensional change rate of corundum-spinel porous bricks is slightly larger than that of chrome corundum porous bricks. In other words, the volume stability of corundum-spinel porous bricks is inferior to that of chrome corundum bricks, mainly because magnesium-aluminum spinel is generated during the sintering process of corundum-spinel porous bricks. Since the slotted porous bricks have narrow slots, typically around 200 μm, significant volume changes during sintering may affect the slot dimensions, ultimately impacting airflow and argon-blowing performance, resulting in decreased performance, reduced efficiency, or even failure to blow through.   Due to the better thermal stability of spinel compared to corundum, the thermal shock resistance of corundum-spinel porous bricks is superior to that of chrome corundum porous bricks. Both have the same slag erosion resistance index, but chrome corundum bricks exhibit stronger slag penetration resistance than corundum-spinel bricks. Overall, in terms of performance, corundum-spinel porous bricks surpass traditional chrome corundum porous bricks and have gradually replaced them, becoming the mainstream ladle porous brick material today.