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Oct 29 2026

Several Factors Affecting the Performance of Alumina-Magnesia Refractory Castables for Steel Ladles

Alumina-magnesia castables—a type of refractory castable—are widely used as linings for steel ladles. Refractory specialists both in China and abroad have conducted extensive research on these materials, focusing on how various components—such as aggregates, magnesia, corundum fines and ultrafines, and silica fume—influence their performance.

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Selection of Aggregates

Aggregates serve as the structural framework within refractory materials. The alumina-based aggregates used in alumina-magnesia castables primarily include fused alumina, sintered alumina, and natural bauxite clinker.

Studies comparing the effects of high-alumina bauxite clinker, high-purity fused corundum, and electro-fused bauxite-corundum on the properties of alumina-spinel castables have shown that castables utilizing fused high-alumina corundum exhibit the best flowability, while those based on bauxite-spinel demonstrate the poorest thermal shock stability.

Research into the selection of aggregates for steel ladle alumina-magnesia castables—specifically comparing fused white corundum, brown corundum, and premium-grade bauxite clinker—indicates that samples containing brown corundum aggregates offer the best flowability. In terms of thermal shock stability, samples with white corundum aggregates perform best, followed by those with brown corundum, while samples using bauxite clinker perform the worst.

An analysis of replacing “Grade 88” high-alumina material with “Grade 88” homogenized material, or with “Grade 85” homogenized high-alumina material, suggests that substituting higher-grade high-alumina materials with “Grade 85” homogenized material—specifically in the 3–1 mm and 1–0 mm aggregate fractions as well as the fine powder fraction—offers greater economic viability and feasibility.

Selection of Corundum Fines

The Al₂O₃ present in corundum fines can react with CaO in molten slag to form high-melting-point phases, specifically CA₂ and CA₆. Furthermore, alumina-rich spinel—which contains cationic vacancies—can capture FeO and MnO from the slag, forming (Mg, Fe, Mn)O·Al₂O₃. This process increases the SiO₂ content and the viscosity of the slag, thereby enhancing the material’s resistance to slag erosion and penetration.

Research into the effect of alumina fines on spinel formation in alumina-magnesia castables has shown that when a castable contains reactive alumina, the magnesia acts as a substrate for spinel formation; the reactive alumina provides an abundant supply of Al₂O₃, which diffuses to form magnesium-rich spinel. Conversely, because sintered alumina possesses lower reactivity, the interdiffusion between alumina and magnesia requires more time. Given the nature of the contact interface during this diffusion process, alumina-rich spinel is formed, which offers superior slag resistance. Moreover, as sintered alumina is more cost-effective than reactive alumina, it is the more advantageous choice. Additionally, incorporating an appropriate amount of reactive α-Al₂O₃ micro-powder into alumina-magnesia castables increases the density of the material, further improving its resistance to slag. A high-purity alumina-magnesia castable bonded with ρ-Al₂O₃ was also developed; it was found that, compared to castables bonded with pure calcium aluminate cement, the matrix of the ρ-Al₂O₃-bonded castable is significantly purer, which extends the service life of the material.

Proportioning for Spinel

The chemical formula for magnesium-aluminum spinel is MgO·Al2O3, with a theoretical composition of 28.3% MgO and 71.7% Al2O3. The proportioning used to synthesize magnesium-aluminum spinel—specifically the molar ratio of MgO to Al2O3—directly influences the properties of the resulting material. Magnesium-rich spinels, which typically have an MgO/Al2O3 molar ratio greater than 1, exhibit a relatively dense structure. In contrast, aluminum-rich spinels contain a higher density of intra-crystalline pores; this is likely due to the differing growth mechanisms occurring on the MgO-rich and Al2O3-rich sides during the spinel formation process. In industrial practice, the MgO/Al2O3 ratio for synthetic spinel is determined by its intended application. Magnesium-rich spinel is commonly used for the kiln linings of large-scale cement kilns. Aluminum-rich spinel is frequently combined with Al2O3-based raw materials to produce castables or precast shapes for large- and medium-sized steel ladles, as well as specialized components such as porous plugs and seating blocks. Meanwhile, bauxite-based spinel castables—synthesized from natural raw materials—are primarily used for small-scale steel ladle applications.

Magnesia Content

As the primary raw material for the in-situ formation of spinel in alumina-magnesia castables, magnesia (MgO) significantly influences the strength, volume stability, slag resistance, and thermal shock resistance of the specimens. Furthermore, because MgO is prone to hydration, the magnesia content also has a notable impact on the workability (construction properties) of the castables.

Research into the effect of fine magnesia powder content on the slag resistance of alumina-magnesia castables indicates that as the amount of added magnesia increases, the material’s resistance to slag erosion decreases, while its resistance to slag penetration improves. However, an excessive amount of magnesia leads to a loose material structure, which ultimately results in a decline in overall slag resistance.

Studies on the influence of fused magnesia content on the properties of unfired alumina-magnesia materials have shown that the reaction to form spinel begins at 1050°C. By adjusting the particle size and the quantity of added magnesia, it is possible to effectively prevent issues such as spalling, swelling, and slag penetration. Leveraging China’s abundant high-alumina bauxite resources—and taking into account the practical operational capabilities of small and medium-sized steel mills—refractory castables in the Al2O3-MgO system have been developed using premium-grade calcined high-alumina bauxite and fused magnesia as the primary raw materials. Research demonstrates that increasing the magnesia content within the matrix enhances the matrix’s resistance to erosion, though it simultaneously reduces the castable’s resistance to penetration.

Silica Fume

Silica fume has a significant impact on the properties of alumina-magnesia castables. Specifically, its inclusion can substantially reduce the required water content, inhibit the hydration of magnesia (periclase), enhance fluidity, and improve workability during installation. On one hand, silica fume can react with MgO, CaO, and Fe2O3 present in the material to form low-melting-point phases—such as anorthite, gehlenite, forsterite, and merwinite—which adversely affect high-temperature performance. On the other hand, it can be used to regulate the volume expansion associated with spinel formation and accelerate the spinel-forming reaction itself.

Research into the relationship between silica fume content and the phase composition and properties of high-purity alumina-magnesia castables indicates that an excessive amount of silica fume leads to the infiltration of a liquid phase—formed at high temperatures—into the spaces between corundum, periclase, and spinel grains. This causes “over-firing” of the castable, resulting in cracking and spalling. Conversely, the addition of silica fume can enhance the cold strength of the castable across various temperature ranges and reduce its residual expansion. In the development of bauxite-based ladle castables—utilizing premium-grade bauxite and fused magnesia as primary raw materials and employing an MgO-SiO2-H2O bonding system—the amount of silica fume added should be minimized, with the limit being the point at which it would otherwise cause a significant increase in the water required for the mix.

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Oct 14 2026

On-site Preparation Method for Refractory Mortar Used in Kilns and Furnaces

Those familiar with refractory materials know that when installing refractory bricks or precast refractory shapes, the refractory mortar used must be of the same material composition as the bricks or shapes themselves. This is essential to prevent quality issues that could arise from material incompatibility. The construction of kiln linings may involve various types of refractory mortar—such as clay-based, high-alumina, or phosphate-bonded varieties. Consequently, all masonry work must adhere to the following requirements.

Fireclay Mortar

Fireclay mortar should be used when laying fireclay bricks, fireclay insulating bricks, or diatomite-based insulating products. In China, its properties must meet the requirements for grade NN-42 as specified in the national standard GB/T 14982, “Fireclay Mortar.”

High-Alumina Mortar

High-alumina mortar should be used when laying high-alumina bricks. In China, its properties must meet the requirements for grades LN-55B and LN-65B as specified in the national standard GB/T 2994, “High-Alumina Mortar.”

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Refractory Castable Precast Blocks and Refractory Mortar for Furnace Roof Masonry

When laying refractory castable precast blocks, a refractory mortar of the same composition as the blocks must be used, ensuring an appropriate mix ratio and consistency. For the construction of furnace roofs or other critical components, phosphate-based mortar or PA-80 high-temperature resistant mortar should be employed.

Phosphate-based Mortar

1) Mix Ratio.

The mix ratio for phosphate-based mortar must follow specified requirements. The performance specifications for the phosphoric acid used must comply with relevant standards.

2) Preparation Method.

① During preparation, pour the phosphoric acid into a warm (50°C–80°C) hide-glue solution according to the prescribed proportions and stir until well-blended. Then, add the high-alumina calcined powder (grog) in the required proportions, stirring continuously until the mixture is uniform.
② Mixing may be performed mechanically or manually. For mechanical mixing, the duration for each batch should generally not exceed 5 minutes. For manual mixing, the material must be stirred continuously from the moment ingredients are added until the mixture is uniform.
③ Aging (Maturation) Requirements. Once mixed, the phosphate-based mortar must undergo an aging process. If the aging temperature is between 20°C and 30°C, the aging duration should be no less than 4–24 hours. If the temperature is between 40°C and 60°C, the duration should be no less than 4–16 hours. This allows the phosphoric acid to fully react with impurities in the high-alumina calcined powder, ensuring that any generated gases are released. During the initial stage of aging, the reaction is vigorous and produces many air bubbles; therefore, frequent stirring is required. Once the number of air bubbles decreases, the mixture should be stirred once every 1–2 hours.
④ Consistency Adjustment. To accurately control the consistency of the phosphate-based mortar and to become familiar with its working properties, a trial masonry test should be conducted to fine-tune the consistency.

PA-80 High-Temperature Resistant Mortar

1) Mix Ratio. The mix ratio for PA-80 high-temperature resistant mortar must follow specified requirements. The performance specifications for the materials used must comply with the relevant provisions of GB 201 “Aluminate Cement” and GB/T 2994 “High-Alumina Refractory Mortar.”

2) Preparation Method. Mix the PA-80 high-temperature binder with the composite refractory powder in the specified proportions. After allowing the mixture to mature for 16–24 hours, incorporate the high-alumina cement—adding it in portions as needed for the immediate application—and mix thoroughly. The entire batch should be used at once; any mortar that has already set (cured) must not be used.

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Particle size of the refractory mortar: Generally, fine-grained refractory mortar is used. The specific particle size may also be selected based on the thickness of the mortar joint, provided that the maximum particle size does not exceed 30% of the joint thickness.

Methods and Construction Procedures for Using Refractory Mortar

Refractory mortar is an essential construction material, widely used in the building and repair of equipment such as furnaces, kilns, and chimneys that operate in high-temperature environments. Composed primarily of refractory materials, it can withstand extreme heat, protecting equipment from damage caused by overheating. Consequently, following the correct application methods and construction procedures is crucial to ensuring the effectiveness of the refractory mortar.

Before beginning construction, gather all necessary tools and materials. Refractory mortar typically consists of refractory clay, a binder, and water; the specific proportions should be adjusted based on the requirements of the project. The work site must be kept clean and tidy, free of any debris that could compromise construction quality. Additionally, the surfaces to be treated should be inspected to ensure they are dry and free of oil, grease, or dust, which helps improve the adhesion of the mortar.

Next, thoroughly mix the refractory clay and binder according to the specified ratio. Gradually add water until the mixture reaches the desired consistency for application. Ensure the mortar is blended uniformly—either by hand or using a mechanical mixer—making sure there are no dry pockets or lumps. Once mixed, the refractory mortar should be used promptly to prevent it from losing its adhesive properties due to prolonged exposure.

During application, spread the prepared refractory mortar evenly over the areas requiring repair or new construction. Use tools such as trowels or spatulas to ensure a uniform thickness and smooth, natural-looking edges. For complex areas, the mortar may be applied in layers to ensure overall density and structural strength. After application, it is advisable to provide initial curing—keeping the material moist while protecting it from excessive heat or rapid air-drying—to enhance its strength and fire resistance.

Once the refractory mortar has fully dried, the final inspection and finishing steps are essential. Check the surface for flatness, cracks, or other defects to ensure the mortar will perform as intended. Furthermore, the refractory material should be subject to regular maintenance and inspection throughout its service life to ensure optimal performance and longevity. By following these meticulous construction steps and methods, the use of refractory mortar can achieve optimal results, providing a robust safeguard for various high-temperature equipment.

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Sep 29 2026

How Should the Raw Materials and Binders for Basic Refractory Gunning Mixes be Correctly Selected?

The use of basic refractory gunning mixes to repair steelmaking converters, electric arc furnaces, and ladles while they are in a hot state—thereby extending their service life—has become a widely adopted practice in the global steel industry. It serves as a highly effective technical measure for protecting furnace linings.

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Performance Characteristics of Gunning Mixes

Gunning mixes are essential materials for extending the service life of furnace linings. In general, a gunning mix should possess the following basic properties:

(1) An adhesion rate of greater than 80%.
(2) No spalling or cracking of the gunned surface after the first heat of steel is tapped.
(3) A residual amount of at least 50% on the gunned surface after one heat of operation.

High-quality gunning mixes must meet the following requirements:

(1) Uniform flow characteristics when passing through gunning equipment.
(2) Good adhesion, solidification, and hardening properties.
(3) Minimal rebound (material bounce-back).
(4) Favorable physical properties for the applied layer (high bulk density, low porosity, and high strength).
(5) Good sintering capability.
(6) Excellent refractory performance.
(7) Strong resistance to erosion.

It is evident that the application performance (adhesion, sintering, etc.) and erosion resistance (slag resistance, wear resistance, etc.) of a gunning mix depend on the composition of the raw materials, the particle size distribution, and the properties of the binder system. Furthermore, the rate of rebound directly impacts economic efficiency.

To obtain a high-performance gunning mix, its properties can be adjusted through three fundamental approaches:

(1) Careful selection of raw materials.
(2) Optimization of particle size distribution.
(3) Selection of an appropriate binder system.

Main Raw Materials for Basic Gunning Mixes

Basic gunning mixes are typically composed of MgO-based or MgO-CaO-based materials, with MgO-based compositions being the most common. To ensure that magnesia-based gunning mixes are both effective and economical, simply choosing the cheapest blend is rarely the best approach. High-quality magnesia-based gunning mixes, combined with modern application techniques, can significantly extend the service life of furnaces in the steel industry without compromising production capacity. Consequently, it is essential to select high-purity raw materials.

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High-grade, phosphate-bonded magnesia gunning mixes generally utilize dead-burned magnesia with an MgO content of approximately 95%–97% and a high CaO/SiO₂ ratio. In cases where the CaO/SiO₂ ratio is low, additional CaO should be incorporated. Under these conditions, it is also critical to ensure that the total content of Fe₂O₃ and Al₂O₃—denoted as Σ(Fe₂O₃+Al₂O₃)—does not exceed 1.5%. For high-quality gunning mixes, this value should be kept below 1.0%.

When using dead-burned magnesia with a CaO/SiO₂ ratio greater than 2—supplemented with CaO-rich dead-burned magnesia—to produce phosphate-bonded gunning mixes, hydration can occur, potentially leading to the spalling of excessively thick gunning layers. Appropriate preventive measures must therefore be taken; surface coating (applied to MgO-CaO grains or CaO-rich dead-burned magnesia) is a particularly effective technique.

High-quality gunning mixes require high-calcium additives to facilitate the formation of high-melting-point phases (such as calcium phosphates or dicalcium silicates), while preventing the creation of low-melting-point silicates. These high-calcium additives, which react with the binder, are most effective when distributed in the form of fine powder.

Gunning mixes designed for long service life should contain free CaO (fCaO) in addition to high-purity raw materials. By incorporating extra calcium, the basicity of infiltrating slag is increased, which helps prevent the formation of low-melting-point silicates caused by the penetration of other phases, thereby extending the service life of the gunned layer.

Theoretically, the additional fCaO is typically introduced in the form of fine sintered dolomite powder. However, given that this material is prone to hydration, the resulting volume expansion can lead to the failure of the gunning layer. Therefore, it is more appropriate to use an MgO-CaO aggregate containing approximately 20% free CaO (fCaO). In this type of MgO-CaO aggregate, the CaO is encapsulated by periclase, which imparts a relatively high resistance to hydration.

Binders and Binder Combinations

The selection of binders for basic hot-gunning mixes must meet the following requirements:

(1) Optimal adhesion, characterized by rapid hardening and solidification.
(2) Sufficient strength of the gunning mix throughout the entire temperature range in which chemical bonding is active.
(3) Minimal reduction in the slag-erosion resistance of the gunning mix caused by the binder.

Typically, gunning mixes utilize chemical binders. Since these binders influence adhesion, they are required to stabilize the gunned layer as quickly as possible. Stabilization can be achieved either physically—by increasing the (apparent) viscosity of the fine-powder/water slurry between the particles—or chemically—by accelerating the solidification reaction. The amount of binder used should be sufficient to keep the gunned layer stable after drying and as the temperature rises, up until the point where sintering occurs, without significantly compromising the layer’s resistance to corrosion.

Common binders include sodium silicate (water glass), phosphates, and composite systems based on these substances.

1. Silicate Binders

Silicates are used as binders in wet-gunning mixes, specifically in the form of water-soluble silicates (water glass). These are cost-effective and widely applicable—notably in the production of special steels (where phosphorus contamination of the molten steel must be avoided). Modern water glass formulations have been developed with optimized dissolution and solidification rates; for instance, using water glass with an SiO₂/Na₂O molar ratio of 2.7 as a binder yields excellent results.

2. Phosphate Binders

Compared to phosphates, silicates (water glass) offer inferior adhesion when used as binders for basic gunning mixes. Furthermore, they exhibit poorer high-temperature strength and thermal shock resistance, leading to limited durability (specifically, poor resistance to erosion by basic slags). This is particularly true when low-grade magnesia is used as the raw material. Extensive research and practical application data indicate that phosphate-based binders are the most ideal bonding systems for basic gunning mixes.

3. Alkali-Silicate-Phosphate Binders

Combining the two aforementioned types of binders results in an alkali-silicate-phosphate composite bonding system. Although this system sets relatively slowly, it yields high high-temperature strength by facilitating the formation of significant quantities of sodium-calcium silico-phosphate (a silicophosphate mineral phase) within the gunning layer. When used in basic oxygen furnaces (BOFs), gunning mixes employing this composite bonding system perform comparably to those using phosphate-based binders. However, this type of mix is particularly well-suited for electric arc furnaces (EAFs), where the lining is subjected to rapid temperature fluctuations—conditions that are especially pronounced near water-cooled panels.

4. Cement-Based Binders

The primary drawbacks of basic gunning mixes that utilize cement-based binders are poor adhesion at high temperatures and inadequate volume stability during rapid heating. These issues can be mitigated by incorporating organic acids; the addition of an organic acid induces flocculation shortly after dispersion, thereby ensuring excellent high-temperature adhesion. Furthermore, the addition of small amounts of a dispersant and an anti-spalling agent can improve volume stability during rapid heating.

Magnesia-based gunning mixes that use high-alumina cement as a binder adhere to the substrate in a plastic state. It can be inferred that when bonding occurs via a liquid-phase intermediate layer, a higher-viscosity layer offers greater resistance to shear stress; this enhances the material’s overall stress resistance and strengthens its bond with the substrate. Consequently, the gunning layer becomes more stable, ultimately resulting in superior durability. Such gunning mixes are particularly well-suited for the repair of localized damage in the linings of steel ladles and secondary refining vessels.

Additionally, there are instances where calcium phosphate, sodium phosphate, and sodium silicate are used in combination, as well as cases involving the combined use of calcium phosphate and aluminum sulfate.

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Optimization of Basic Gunning Mix Formulations

Basic gunning mixes are primarily used for the hot repair of steelmaking equipment; therefore, their formulations must be tailored to the specific steel grades being produced, operational conditions, and the type of equipment. In other words, different gunning mixes should be selected based on the distinct requirements of each application. Users can generally make their selection according to their specific smelting conditions and equipment characteristics.

(1) Under high-basicity smelting conditions, it is advisable to use phosphate-bonded magnesia-based gunning mixes with a relatively high CaO content (approximately 6%). These materials offer superior resistance to erosion by basic slag and exhibit greater durability compared to silicate-bonded magnesia-based gunning mixes.
(2) MgO-CaO-based gunning mixes (containing 8%–12% CaO) that utilize a polyphosphate-CaO-SiO₂ binder system provide even greater resistance to basic slag erosion and are, therefore, referred to as “long-life” gunning mixes.
(3) Magnesia-based gunning mixes bonded with silicates (such as water glass)—produced using high-purity magnesia with a low CaO/SiO₂ ratio—demonstrate excellent resistance to erosion by acidic (low-basicity) slag.
(4) When magnesia with a low CaO/SiO₂ ratio is used as the raw material, the resulting gunning mixes—regardless of whether a phosphate or silicate binder is employed—exhibit strong and comparable resistance to acidic slag. However, the low CaO content (and the resulting lack of free CaO, or fCaO) slows the curing rate of phosphate-bonded magnesia-based mixes. Consequently, such mixes (derived from low-CaO/SiO₂ magnesia) are difficult to apply in thick layers. This issue can be addressed by incorporating an appropriate amount of a CaO-bearing substance.
(5) Magnesia-based gunning mixes that employ a composite binder system—consisting of both silicates and phosphates—offer greater versatility and are thus known as “universal” gunning mixes. These mixes are particularly well-suited to the operational conditions of steel ladles.
(6) Magnesia-alumina gunning mixes—formulated with cement as a binder, an organic acid as a flocculant, and small amounts of a dispersant and an anti-stripping agent—are suitable for localized gunning repairs in secondary refining units and offer good durability.

Based on the above discussion, the following conclusions can be drawn:

(1) For different applications—such as basic oxygen furnaces (BOFs), electric arc furnaces (EAFs), and ladles—it is necessary to select specific grades and types of basic gunning mixes, tailored to the distinct operating conditions of each.
(2) In BOFs, phosphate-bonded MgO-based or MgO-CaO-based gunning mixes are typically used to achieve a long service life. However, if the operating temperature is too low, the gunning mix layer may fail to sinter sufficiently and subsequently spall off. In such cases, it is advisable to use an MgO-CaO-based gunning mix with a phosphate-CaO-SiO₂ bonding system, which is better suited to these operating conditions.
(3) Silicate-bonded MgO-based gunning mixes are primarily used in EAFs and can also be applied in ladles (at moderate temperatures). When high-purity dead-burned magnesia is used as a raw material to enhance corrosion resistance, the binder content should be appropriately increased, and specific additives should be incorporated; otherwise, the gunning mix layer may spall, preventing the desired performance.
(4) Magnesia-based gunning mixes that utilize a composite binder—consisting of both silicates and phosphates—exhibit high adaptability and can be considered “universal” gunning mixes. These are particularly well-suited to the operating conditions of steel ladles.
(5) Cement-bonded MgO-Al₂O₃-based gunning mixes, when modified with the addition of flocculants, dispersants, and anti-spalling agents, can also be used in ladles and secondary refining equipment.

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Blog Copper Metallurgy Refractory

Sep 14 2026

Why is There No Standardized Furnace Designed for Copper Smelting?

Copper smelting furnaces come in various types, including flash furnaces, Australian furnaces, SKS furnaces, silver furnaces, and Noranda furnaces. Many people might wonder after reading this: since all these furnace types can complete matte smelting, why isn’t there a single furnace type suitable for all copper smelters? The reason is simple: copper smelting isn’t a “furnace selection competition,” but rather a “system matching battle.” Flash furnaces emphasize large-scale continuous operation and stable concentrate; top-blown furnaces emphasize strong stirring and adaptability to complex materials; bottom-blown furnaces emphasize the internal reaction of the molten pool and flue gas conditions; and side-blown furnaces emphasize continuous organization and control of the side reaction zone. There is no absolutely optimal furnace type, only what is suitable or unsuitable.

Conclusion: There is no one-size-fits-all furnace, only system compatibility.

Many people, when discussing furnace types, like to ask: Which furnace is the best? This question is actually difficult to answer. Copper smelting isn’t about choosing a single “one-size-fits-all” piece of equipment, but rather selecting a complete process system. The quality of a furnace depends not only on the furnace itself, but also on: the raw material conditions; the stability of the concentrate grade; the suitability of sulfur, iron, and silicon content; the level of impurities; the proportion of return material and dust; the compatibility of the flue gas acid production system; how the slag is handled; whether it’s connected to a converter or continuous blowing; the affordability of investment and operating costs; and the level of on-site operation and maintenance. Therefore, different furnace types are not simply a matter of advanced versus outdated. More accurately, they solve different problems.

Flash Furnace: Suitable for stable concentrates and large-scale continuous production.

The core characteristic of flash smelting is that the ore reacts in the air. Dried fine-grained copper concentrate and oxygen-enriched air enter the reaction tower, where oxidation, exothermic reaction, melting, and preliminary matte formation are rapidly completed in a suspended state. The advantages of flash furnaces are obvious: fast reaction speed; high thermal efficiency; high degree of continuous operation; better SO₂ conditions in the flue gas; and suitability for large-scale production. This is why the Outokumpu flash furnace has become one of the important mainstream furnace types in modern copper smelting.

However, flash furnaces also have their own prerequisites: they rely heavily on dry ore, stable particle size, stable batching, and good injection organization. In other words, they are well-suited for processing concentrates with stable conditions and thorough preparation, but they also have relatively high requirements for raw material fluctuations, complex material proportions, and the preparation system.

So, what are flash furnaces suitable for? Flash furnaces are suitable for large-scale, efficient, and continuous production under stable concentrate conditions.

Top-blown furnaces: Suitable for strong stirring and handling complex materials

Typical examples of top-blown furnaces are the Åbo furnace and the ISA furnace. Its core is the top-immersion lance. The lance is inserted into the molten pool from the top of the furnace, injecting oxygen-enriched air, fuel, etc., into the molten pool.

The keyword for top-blown furnaces is: strong stirring. Once the molten pool is agitated, the contact between gas, liquid, and solid is significantly enhanced, leading to increased heat and mass transfer. Materials entering the molten pool do not float quietly on the surface and react slowly; instead, they are quickly drawn into the melt to participate in the reaction. Therefore, top-blown furnaces are highly adaptable to complex copper-containing materials, return materials, fumes, and cold materials.

However, top-blown furnaces are not a “one-size-fits-all” solution. Attention must be paid to lance lifespan, lance position, molten pool splashing, slag entrainment, and subsequent settling and depletion pressure. Strong agitation is an advantage, but it also results in more thorough mixing of slag and matte, requiring careful handling of copper content and separation issues in the slag.

So, what are top-blown furnaces suitable for? Top-blown furnaces are suitable for systems requiring strong agitation, high adaptability to complex materials, and a high proportion of return materials and fumes. Their advantage is not being the “cleanest,” but rather their ability to “quickly draw complex materials into the reaction.”

Bottom-blown furnace: Suitable for organizing reactions from within the molten pool

A representative bottom-blown furnace is the SKS furnace, also known as the Shuikoushan oxygen bottom-blown smelting furnace. Its core characteristic is that oxygen enters the molten pool from the bottom. More specifically, oxygen enters the copper matte layer from the bottom, forming rising bubbles, molten circulation, and intense reactions within the molten pool.

The advantages of a bottom-blown furnace are: sufficient gas-liquid contact; deep reaction within the molten pool; better oxygen utilization conditions; relatively small flue gas volume; and better SO₂ flue gas conditions. These characteristics are beneficial for subsequent acid production and environmental control.

However, the most challenging aspect of a bottom-blown furnace is also clear: the bottom gas supply system. Because oxygen enters from the bottom, the oxygen lance, tuyeres, bottom refractory materials, sealing, and maintenance are all crucial. Problems with the bottom oxygen supply system are difficult to resolve. Simultaneously, due to the strong agitation during bottom blowing, attention must still be paid to slag copper content, Fe₃O₄, slag viscosity, and slag-matte separation.

So, what is a bottom-blown furnace suitable for? Bottom-blown furnaces are suitable for systems emphasizing internal molten pool reactions, flue gas acid production conditions, and environmental control, but they require high stability in the gas supply from the furnace bottom. Their advantage lies in deepening the reaction from within the molten pool; their challenge also lies at the furnace bottom.

Side-blown furnaces: Suitable for continuous operation and control of the side reaction zone

Representative side-blown furnaces include the Baiyin furnace, Noranda furnace, and Vanyukov furnace. Their core characteristic is that gas enters the molten pool from the side of the furnace body. Side blowing is neither from top to bottom nor bottom to top, but rather from the side tuyeres, driving the melt to form a lateral flow and reaction zone.

The advantages of side-blown furnaces are: relatively intuitive furnace structure; flexible reaction zone layout; suitability for continuous operation; and strong material adaptability. For example, the Baiyin furnace emphasizes the separation of the smelting and settling zones, with a strong reaction at the front and clarification and separation at the back. The Noranda furnace is a horizontal furnace body, organizing the reaction and settling along its length. The Vanyukov furnace emphasizes slag-blown smelting, relying on side-blown oxygen-enriched gas to enhance slag agitation and reaction.

However, side-blown furnaces also present typical challenges: erosion in the tuyeres area; slag line scouring; furnace lining life; localized overheating; copper content control in the slag; and internal flow organization.

So, what are side-blown furnaces suitable for? Side-blown furnaces are suitable for systems with continuous side-blown reactions, flexible process organization, and the ability to accept and manage tuyeres and furnace lining maintenance pressures. The advantages and disadvantages of side-blown furnaces actually stem from the same source: the strong molten pool disturbance caused by lateral air supply.

Choosing a furnace type shouldn’t be based solely on the furnace itself.

Often, a plant’s choice of furnace type isn’t based on just the furnace itself, but on the entire production line. For example: Is there a stable dry ore system at the front end? Is the raw material complex? Is the return material ratio high? Can the flue gas sulfuric acid production system match? Is the downstream a conventional converter or continuous blowing? Does the slag have a settling electric furnace or a slag depletion system? What are the local oxygen, electricity, and fuel costs? How stringent are the environmental protection requirements? Is there sufficient operational and maintenance capability on site? These factors combined determine whether a furnace type is truly suitable for a particular plant. Therefore, you’ll see: some plants are suited to flash furnaces; some to top-blown furnaces; some to bottom-blown furnaces; and some to side-blown furnaces. It’s not that everyone’s judgment is different, but rather that each smelter faces different challenges.

Furnace Selection: Essentially System Matching

Copper smelting is not a victory for a single piece of equipment, but a balance of the entire system. The furnace type is only one component. What truly needs matching are: the raw material system; the smelting system; the blowing system; the slag treatment system; the flue gas acid production system; the environmental protection system; the energy system; and the operation and management system. Looking only at the furnace itself easily leads to one-sided judgments. For example, a certain furnace type might have a strong reaction, but if the subsequent slag depletion cannot keep up, the copper content in the slag may be high. A certain furnace type might have excellent flue gas conditions, but if oxygen costs are too high, its economics may not be suitable. A certain furnace type can handle complex feedstocks, but if maintenance is difficult and on-site management cannot keep up, problems will arise. A certain furnace type has high single-furnace capacity, but if the front-end feed preparation system is unstable, it is difficult to operate stably for a long time. Therefore, furnace selection is not simply “which is the best,” but rather: which is the most suitable for the entire system.

Flash Furnace: Large and precise. Suitable for stable concentrate production, large-scale, efficient, and continuous production.
Top-blown Furnace: Flexible and powerful. Suitable for strong stirring, complex materials, return materials, and fume control.
Bottom-blown furnace: Deep and stable. Suitable for organizing reactions from within the molten pool, with better flue gas conditions.
Side-blown furnace: Wide and flexible. Suitable for continuous processing and control of the side reaction zone.

Ultimately, furnace selection must return to raw materials, scale, environmental protection, investment, and process configuration.

In conclusion,

Copper smelting cannot rely on only one type of furnace. This is not because the technology is immature, but because copper smelting faces different raw materials, processes, and on-site conditions. Flash furnaces have their advantages; top-blown furnaces have their applicable scenarios; bottom-blown furnaces have their characteristics; and side-blown furnaces also have their place. It’s not about which furnace type is best, but rather, under a series of comprehensive conditions such as specific raw materials and scale, which furnace type is most suitable!

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Sep 11 2026

Brand Name and Logo Upgrade Announcement

Dear Esteemed Customers and Partners,

We would like to express our sincere gratitude for your support and trust in Rongsheng Refractory over the years. In a strategic move to more effectively convey our brand concept and meet the evolving requirements of future development, Rongsheng Refractory will, as of now, officially adopt a new brand logo. Concurrently, the brand name “RONGSHENG” will be officially upgraded to “RISING“.

During the transition period of this brand logo upgrade, both the old and new logos will be synchronously used. We kindly request your understanding and patience.

This brand renewal signifies our commitment to persistently offering global customers high-efficiency, energy-saving, and innovative refractory products and services, all delivered with an even more professional demeanor. We are dedicated to upholding the highest standards of quality and service excellence.

Once again, we extend our heartfelt appreciation for your continuous companionship and support.

Rongsheng Refractory Manufacturer

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Aug 30 2026

Performance and Construction Methods of Acid-Resistant Castables for the Petrochemical Industry

Acid-resistant castables are those that can resist corrosion from colloidal media such as nitric acid, hydrochloric acid, sulfuric acid, and acetic acid at temperatures ranging from 80 to 1200℃. Acid-resistant castables are typically made from acid-resistant aggregates, such as silica, cast stone, wax stone, and diabase particles, as well as acid-resistant material powders from waste silica bricks, silica, waste porcelain, and cast stone, using water glass as a binder.

Performance and Applications of Acid-Resistant Castables

The modulus of water glass is between 2.6 and 3.2, and the density is between 1.38 and 1.42 g/m³. The addition amount is typically between 13% and 16%. Sodium fluorosilicate is used as a settling accelerator, added at 10% to 12% of the water glass solution mass. This type of acid-resistant castable is low in cost and has good acid resistance, making it widely used in furnace linings or chimneys in metallurgy and chemical industries. However, it has poor resistance to phosphoric acid, hydrofluoric acid, and high-fatty acid corrosion.

Rongsheng Acid-Resistance Castable Manufacturer

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Technical Performance of Acid-Resistant Castables

Acid-resistant castables possess the following properties:

Acid-resistant castables are a new type of anti-corrosion material with strong prestress, composed of multiple components including potassium silicate as a binder, inorganic molecular materials as curing agents, and silicates as acid-resistant fillers.
Acid-resistant castables have high mechanical strength and excellent bonding properties. Especially in the construction of granite blocks, acid-resistant ceramic tiles, and ceramic slabs, the adhesion between the castable and cement is greater than that of the base material.
The acid-resistant castable exhibits stable performance in various concentrations of organic and inorganic acids. Particularly in dilute acids, industrial water, and neutral aqueous solutions, it does not produce crystalline salts and possesses high impermeability.
It has good heat resistance and can be used in titanium dioxide rotary kiln linings at temperatures as high as 950℃-1000℃.
The acid-resistant castable uses a non-toxic curing agent, posing no harm to operators and construction personnel. It has been certified by medical and health departments as suitable for corrosion protection in food, pharmaceutical, and other equipment.
Compared with organic acid-resistant materials, the acid-resistant castable is inexpensive. In addition to possessing the same acid and corrosion resistance as organic materials, it also has the unique property of resisting corrosion from strong oxidizing media.
It cures at room temperature, is simple to construct, convenient to use, easy to transport, and requires moisture-proof storage.

Applications of Acid-Resistant Castables

Acid-resistant castables can be used in various concentrations of sulfuric acid, hydrochloric acid, nitric acid, chromic acid, hypochlorous acid, chlorosulfonic acid, formic acid, oxalic acid, acetic acid, and other acids; various organic solvents; various acidic salts; oxidizing media such as chlorine and hydrogen peroxide; and mixtures of the above media. Rongsheng acid-resistant materials are widely used in corrosion protection projects for reaction vessels, storage tanks, towers, floors, trenches, electrolytic cells, etc., in industries such as petroleum, chemical, metallurgy, power, pesticides, food, fermentation, hydrolysis, and pickling.

Acid-resistant castable refractory construction requirements:

Acid-resistant castable refractory, 10-20 mm thick, should be applied in sections. The spacing between sections should be 2-3 meters, and the joint width should be 15-20 mm. The joints should be completely filled with a suitable sealant.
Acid-resistant castable refractory can also be used to line granite blocks. The bonding layer and joint width are generally 10-15 mm.
The construction requirements for acid-resistant castable refractory are the same as those for mortar application.
Acid-resistant castable refractory can be used for integral casting linings of reaction vessels, storage tanks, towers, electrolytic cells, trenches, floors, fermentation tanks, etc., in chemical, light industry, metallurgical, pickling, petroleum, pesticide, food, electroplating, and electrolysis industries. With the addition of reinforcing steel, it can serve as a structural corrosion-resistant material.
When casting inside carbon steel equipment, the surface of the carbon steel equipment should be sandblasted to remove rust. When casting inside cement concrete equipment, the surface of the equipment should be thoroughly cleaned of oil and dust.
The formwork structure used for casting must be tight, dimensionally accurate, and possess sufficient rigidity; a height of 50 cm is recommended.
Before construction, the formwork surface should be coated with oil, then a plastic film should be placed on the formwork surface, extending 5-10 cm beyond the joints.
Mixing containers and tools must be clean and dry.
The temperature at the construction site must be above 15℃. Rain shelters should be erected during the rainy season.
Mix the concrete and potassium silicate thoroughly according to the mixing ratio.
Pour the mixed material into the formwork and compact it manually or with mechanical vibration.
The filling depth should be 30 cm each time.
If the ambient temperature is above 35℃, the formwork can be removed after seven days. After demolding, strictly prevent impact and localized high-temperature welding.
If casting load-bearing structural equipment, reinforcement should be designed accordingly.

Acid-Resistance Castable for Sale — Acid-Resistant Castable for Sale

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Precautions for Acid-Resistant Castable Resin Construction

Carbon steel equipment should be sandblasted to remove rust before construction. For concrete equipment, surface dust should be cleaned and uneven areas repaired. The moisture content of concrete tanks and pools should be less than 6%.
The surfaces of acid-resistant bricks and granite used for lining should be clean and dry.
Containers and tools for mixing acid-resistant materials should be clean and dry.
The temperature at the construction site should be between 15°C and 35°C, and the ambient air temperature should be below 80°C before construction. If it exceeds 80°C, ventilation and dehumidification facilities should be added.
Weigh potassium silicate according to the acid-resistant castable resin mix ratio and add it to the mixer or mixing container. Then add the weighed powder and mix thoroughly. Each batch of mixture should be used within 30 minutes.
During construction, it is strictly forbidden to add powder or potassium silicate to the acid-resistant castable resin. If the mortar hardens, it should be discarded.
When lining brick slabs, the mortar should be applied fully and compacted with a spatula, squeezing the mortar out of the brick joints. Excess mortar should be scraped away with a knife. The bonding layer and joint should generally be 3- 5 mm.
When lining large acid-resistant bricks, they should be supported and secured to prevent movement.
After successful lining, the equipment must be cured in an environment above 15 degrees Celsius for at least 14 days. During curing, contact with water and water vapor is strictly prohibited.
For open-air construction, a rainproof and sun-protective shed should be erected.

What is the difference between acid-resistant and alkali-resistant castables?

Alkali-resistant castables are castables that resist the corrosion of alkali metal oxides at medium to high temperatures. They can be classified into medium-temperature and high-temperature types according to their service temperature, and into lightweight and heavyweight types according to their bulk density. Medium-temperature alkali-resistant castables typically use aluminosilicate materials as aggregates or fine powders, such as clay clinker, waste porcelain powder, and expanded perlite. Their resistance to alkali corrosion works by reacting with alkali metal oxides to form a high-SiO2, high-viscosity glaze layer on the surface of the refractory castable, thus preventing further penetration of alkali metal oxides into the interior of the refractory castable and improving its corrosion resistance.

Alkali-resistant castables are divided into high-strength alkali-resistant castables and ordinary alkali-resistant castables. They are used extensively in cement rotary kiln preheaters, with SiO2 content around 60% and Al2O3 content between 45% and 75%. High-strength alkali-resistant castables use high-voltage electrical porcelain materials, while ordinary alkali-resistant castables use low-voltage electrical porcelain materials. The higher the operating temperature, the higher the Al₂O₃ content. Depending on the application, calcium aluminate cement, silica powder, etc., can be selected to adjust the process proportions.

For excessively high temperatures, alkali-resistant castables are also made using chromium corundum, zircon, fused spinel, etc., as aggregates or fine powders. These types of alkali-resistant castables are mostly used in hazardous waste incinerators.

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Aug 15 2026

The Influence of Al2O3-Cr2O3 Solid Solution Particles on the Performance of High-Chromium Bricks

High-chromium bricks are shaped refractory products made primarily from industrial-grade chromium trioxide and alumina, with the addition of small amounts of zirconium oxide, etc., and fired at high temperatures. The chromium trioxide content is not less than 75%, and the combined content of chromium trioxide, alumina, and zirconium oxide is not less than 98%. Some even have a chromium trioxide content as high as approximately 90%. This high chromium trioxide content endows high-chromium bricks with excellent refractory properties and high-temperature stability.

Advantages and Characteristics of High-Chromium Bricks

High-chromium bricks possess the following characteristics:

(1) High Refractoriness: High-chrome bricks have a refractoriness far exceeding that of ordinary refractory products, maintaining structural stability at high temperatures and resisting softening and deformation. Therefore, they can be used in thermal equipment such as industrial furnaces and kilns with extremely high temperature requirements.
(2) High High-Temperature Strength: Under high-temperature conditions, high-chromium bricks maintain high strength and possess excellent wear and impact resistance. They can resist the erosion and friction of materials inside the furnace, extending the service life of the furnace lining.
(3) Strong Corrosion Resistance: They have good resistance to some acidic and alkaline chemicals and are not easily corroded by molten slag and gases inside the furnace, thus ensuring the integrity and stability of the furnace lining.
(4) High Thermal Conductivity: They have high thermal conductivity, enabling rapid heat transfer within the furnace, improving energy utilization efficiency, and reducing energy consumption.

Due to their excellent refractoriness and high-temperature stability, high-chrome bricks can be widely used in various high-temperature environments. In steelmaking, high-chromium bricks are widely used in the linings of high-temperature furnaces such as blast furnaces, converters, and electric furnaces, including the belly and waist of blast furnaces. High-chromium bricks effectively resist the erosion of high-temperature gas and slag, improving the service life and production efficiency of the blast furnace. In glass melting furnaces, high-chromium bricks can be used in the pool walls and furnace bottom, resisting the erosion and scouring of molten glass while possessing good heat insulation properties, thus contributing to improved glass melting quality and production efficiency. High-chrome bricks also have important applications in the smelting of non-ferrous metals such as copper, aluminum, and zinc. In areas like the tuyeres and slag line of copper smelting furnaces, high-chromium bricks effectively resist the erosion of high-temperature melt and slag, extending the service life of the furnace lining.

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The Influence of Al2O3-Cr2O3 Solid Solution Particles on the Performance of High-Cr Bricks

By optimizing particle size distribution, increasing the sintering temperature, and adding novel accelerators and binders, the strength of high-chromium bricks can be improved.

Specific experimental schemes for adding different fused Al2O3-Cr2O3 solid solutions to high-chromium bricks in granular form are presented. K1, K2, K3, K4, K5, and K6 represent the aggregate portions of the samples, which are 100%, 95%, 90%, 75%, 10%, and 0% aluminum-chromium, respectively.

The changes in bulk density and apparent porosity of various samples with different Al2O3-Cr2O3 solid solutions added to high-chromium bricks in granular form are also shown. It can be seen that as the Al2O3 content in the added Al2O3-Cr2O3 solid solution increases, the bulk density of the product initially decreases. Then, in scheme K6, i.e., with 0% Aluminum-Cr2O3, the apparent porosity increases, and correspondingly, it first increases, then decreases again with 0% Aluminum-Cr2O3. In this part of the experiment, because the bulk density and apparent porosity of the product are affected not only by the degree of sintering densification but also by the properties of the particles themselves and the theoretical density of different compounds, they do not have a significant effect on predicting local variation trends.

The cold strength of each sample with different Al2O3-Cr2O3 solid solutions added to high-chrome bricks in granular form was measured. It can be seen that the room-temperature flexural strength and room-temperature compressive strength have the same trend, i.e., first decreasing and then increasing. At scheme K4, i.e., with 75% Aluminum-Cr2O3 particles, the minimum values of 23.8 MPa and 126.3 MPa were reached, respectively. The strengths of schemes K6 and K1, with 0% and 100% aluminum-chromium particles, respectively, were the highest and second highest among all samples, at 42.8 MPa and 192.9 MPa, and 30.4 MPa and 172.1 MPa, respectively. The differences in the physical properties of the products were very significant.

The high-temperature flexural strength variation trends of the high-chromium brick samples with different Al2O3-Cr2O3 solid solutions in granular form were clearly shown. Scheme K4, with 75% aluminum-chromium particles, had the lowest high-temperature flexural strength at 15.5 MPa. This was significantly lower than Scheme K1 (24.5 MPa) with 100% aluminum-chromium particles and Scheme K6 (24.2 MPa) with 0% aluminum-chromium particles. The high-temperature flexural strength showed a trend of first decreasing and then increasing.

The residual flexural strength of high-chrome bricks with different Al2O3-Cr2O3 solid solutions added in granular form after thermal shock initially decreased and then increased, reaching a minimum at scheme K4 with 75% aluminum chromium material particles added.

The effect of Al2O3-Cr2O3 solid solution particles on the static slag resistance of high-chromium bricks. After comparison, it is clear that the thickness of the residual slag layer gradually decreases and disappears from scheme K1 to scheme K5, while a significant slag layer reappears in scheme K6, with an average thickness of approximately 1 mm.

The effect of Al2O3-Cr2O3 solid solution particles on the resistance to coal slag erosion of high-chromium bricks. Macroscopically, the resistance to coal slag erosion increases from 10.1% to 19.4% in scheme K1 to scheme K5, then decreases to 13.3% in scheme K6.

The distribution of Si, Ca, and Fe element contents at different distances from the slag surface after static slag resistance tests for schemes K1, K3, K5, and K6, based on the effect of Al2O3-Cr2O3 solid solution particles on the resistance to coal slag erosion of high-chrome bricks. Comparing schemes K1, K3, and K5, it can be seen that the penetration depth and amount of SiO2, CaO, and Fe2O3 in coal slag gradually increase from K1 to K5. Taking the penetration depth of SiO2, CaO, and Fe2O3 as an example, the penetration depths in scheme K1 are 2mm, 3mm, and 1.5mm, while in scheme K5 they are 7mm, 7mm, and 2.5mm, showing a significant increase in penetration depth. Comparing schemes K5 and K6, it can be seen that the penetration depth and amount of SiO2, CaO, and Fe2O3 in scheme K6 are relatively small. Again, taking penetration depth as an example, the values in scheme K6 are 5mm, 5mm, and 2mm, significantly smaller than the corresponding values in scheme K5. Considering the influence trend of different Al2O3-Cr2O3 solid solution particles on the apparent porosity of high-chromium bricks, it can be concluded that the apparent porosity of high-chromium bricks is one of the key factors determining the penetration depth and amount of SiO2, CaO, and Fe2O3 in coal slag.

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The decrease in chromium oxide content is not the cause of the decline in the physical properties of high-chromium bricks; the changing trends in these indicators are due to differences in densification caused by varying degrees of sintering.

Except for slightly different trends in bulk density and apparent porosity among the sample groups due to interference from other factors, the cold strength, high-temperature flexural strength, and residual flexural strength after thermal shock of high-chromium bricks with different Al2O3-Cr2O3 solid solutions added in granular form all showed the same trend: first decreasing and then increasing, reaching a minimum at scheme K4 using 75% aluminum chromium particles. These analyses show that the changing trend is consistent with theoretical predictions. That is, the increase in mixing entropy results in a smaller decrease in Gibbs free energy, which is not conducive to effective sintering.

From the perspective of differentiated high-chrome bricks based on location configuration, compared to K1 and K6, the samples from other schemes all showed a decline in sintering performance (expressed as apparent porosity and bulk density), thermal shock stability, and slag erosion resistance, and therefore cannot be applied. However, compared to K1, while K6 exhibits reduced resistance to slag erosion, it demonstrates improved strengths such as room-temperature flexural strength, room-temperature compressive strength, and thermal shock resistance. Therefore, this design can be used at the cone bottom of a Texaco gasifier, or at the upper part of the cylinder and the cone bottom of a four-nozzle opposed gasifier.

The fire-facing bricks produced using the K6 design, when used at the cone bottom of a Texaco gasifier, initially had a service life of approximately 6500 hours. After trials, the service life increased by nearly 1000 hours, reaching 7564 hours. Similar results were achieved in industrial applications at the cone bottom of a four-nozzle opposed gasifier. Therefore, the use of high-chromium bricks with 0% aluminum-chromium particles at the cone bottom of a gasifier is effective in improving service life.

Improving the Sintering Densification of the Matrix

Improving the sintering densification of the matrix can significantly improve various physical properties of the product, such as room temperature flexural strength and room temperature compressive strength. From the perspective of the structural composition and performance of high-chrome bricks, the entire system can be simply divided into two parts: an aggregate part with a particle size greater than 1 mm and a matrix part with a particle size less than 1 mm. Therefore, the overall mechanical properties of the material will likely be a combination of the following three parts:

(1) Mechanical properties of the aggregate part.
(2) Mechanical properties of the matrix part.
(3) Mechanical properties of the aggregate-matrix bond.

The sintering conditions of the aggregate particles and matrix bond at the same particle size in schemes K1 and K6 show that, compared to K1, the product in scheme K6 has a tighter bond between the aggregate particles and the matrix, resulting in higher sintering density. Through the comparison of schemes K1 and K6, it can be found that improving the sintering densification between the aggregate and the matrix can improve various physical properties of the product. The photographs of the fracture surfaces of K1 and K6 products show that the fracture does not occur entirely in the matrix or along the edges of the aggregate particles, but rather spans both the matrix and aggregate portions.

Based on the above analysis, it can be concluded that improving the performance of the aggregate particles, improving the sintering of the matrix, or promoting the densification of the sintering between the aggregate particles and the matrix will all contribute to improving the various physical properties of high-chromium brick products.

Rongsheng Refractory Materials Manufacturer

Refractory materials are indispensable for ensuring the stable operation of kilns. As the “heart” of the kiln, the configuration and quality of refractory materials determine the service life and production efficiency of the kiln. With the comprehensive development of the refractory industry, higher requirements are being placed on refractory materials, which in turn promotes the development and technological progress of refractory materials. Rongsheng Refractory Materials Manufacturer will continue to provide reliable refractory lining materials for high-temperature industrial furnaces. Contact Rongsheng for free samples and quotations.

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Jul 31 2026

Performance Advantages of Silicon Carbide Lithium Battery Saggers

Against the backdrop of the rapid development of new energy vehicles and energy storage industries, the demand for lithium batteries has exploded. As the core container in the sintering process of lithium battery cathode materials (such as ternary materials and lithium cobalt oxide), the performance of the sagger directly affects sintering efficiency, material quality, and production costs. Traditional alumina saggers are gradually becoming insufficient to meet the demands due to problems such as rapid high-temperature wear and short lifespan. Silicon carbide (SiC) lithium battery saggers, with their unique material properties, are becoming a key direction for industry upgrading. This article will analyze silicon carbide lithium battery saggers from two dimensions: performance advantages and market prospects.

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Performance Advantages of Silicon Carbide Lithium-ion Battery Saggers: High-Efficiency Sintering

Silicon carbide is a ceramic material composed of silicon (Si) and carbon (C), whose crystal structure endows it with excellent physicochemical properties. It exhibits significant advantages in the field of lithium-ion battery saggers:

Ultra-High Temperature Resistance and Thermal Stability

The sintering temperature of lithium-ion battery cathode materials typically needs to reach 800-1000℃ (some high-nickel ternary materials even exceed 1200℃). Traditional alumina saggers are prone to crystal phase transformation at this temperature, leading to volume shrinkage and cracking. Silicon carbide, however, has a melting point as high as 2700℃ and almost no crystal structure change below 1400℃. Its coefficient of thermal expansion is only 4.5×10⁻⁶/℃ (compared to 8×10⁻⁶/℃), enabling it to withstand extreme high temperatures for extended periods without deformation or cracking, significantly extending its service life.

Extreme Corrosion Resistance: Resistant to Molten Salt and Atmosphere Erosion

During sintering, the sagger needs to come into contact with molten materials such as lithium salts (e.g., lithium carbonate) and transition metal oxides, while being exposed to air or an inert atmosphere. Alumina saggers are prone to reacting with alkaline substances, gradually corroding their surface, leading to rough inner walls and material contamination. Silicon carbide has extremely strong chemical stability, resisting acid and alkali erosion from room temperature to high temperatures (except for hydrofluoric acid), and does not react with lithium salts, maintaining a smooth inner wall for a long time, preventing impurities from contaminating the cathode material and improving product purity.

High Thermal Conductivity and Low Energy Consumption: Accelerated Sintering, Cost Reduction and Efficiency Improvement

Silicon carbide has a thermal conductivity as high as 120-150 W/(m·K) (compared to only 20-30 W/(m·K) for alumina), enabling rapid heat transfer, resulting in a more uniform temperature distribution within the sintering furnace, shortening heating time, and improving production efficiency. Meanwhile, its low heat capacity reduces heat accumulation and lowers sintering energy consumption (actual energy savings of approximately 15%-20%), meeting the cost reduction and efficiency improvement needs of the lithium battery industry.

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Ultra-long lifespan: Overall cost reduction of over 60%

Traditional alumina crucibles, due to high-temperature wear and corrosion during continuous use, have an average lifespan of only 30-50 cycles. Silicon carbide crucibles, with their high-temperature and corrosion resistance, can achieve a lifespan of 200-300 cycles (some high-end products exceed 500 cycles). Although the cost per crucible is 30%-50% higher than alumina, the overall cost of use is reduced by over 60%, resulting in significant economic benefits.

Application Areas of Silicon Carbide Saggers

Explosive Downstream Demand: A “Must-Have” for New Energy Vehicles and Energy Storage

According to data from GGII (Gaogong Lithium Battery Research Institute), global lithium battery shipments are growing, with power lithium batteries accounting for over 70%. As the core cost unit of lithium batteries (accounting for approximately 40%), the cathode material requires a huge amount of saggers during its sintering process. Estimating the demand of tens of millions of saggers per GWh of ternary cathode material, the annual demand in the power lithium battery sector alone is enormous. With the rapid growth of global energy storage installations, the sagger market will further expand.

Dual Catalysts of Policy and Technology: Accelerated Replacement Process

High-nickel content and single-crystal material are becoming the upgrade directions for cathode materials. High-nickel materials require higher sintering temperatures (above 1200℃), placing more stringent demands on sagger performance. Traditional alumina can no longer meet these requirements, making silicon carbide saggers the inevitable choice. Furthermore, leading battery manufacturers (such as CATL and BYD) and cathode material manufacturers (such as Ronbay Technology and Dangsheng Technology) have accelerated the adoption of silicon carbide crucibles, driving the industry’s substitution process.

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Technological Iteration: Breakthroughs in Cost Reduction and Scale

Early silicon carbide crucibles were limited in large-scale application due to their complex manufacturing process (requiring high-temperature sintering and surface coating treatment) and high cost. In recent years, companies have reduced the cost per unit by optimizing sintering processes (such as pressureless sintering + reactive infiltration) and developing low-cost raw materials (recycled silicon carbide micropowder). Simultaneously, some manufacturers have achieved higher production capacity, and large-scale production further reduces costs.

Core Carrier for Industrial Upgrading

Silicon carbide lithium-ion battery crucibles, with their advantages of high temperature resistance, corrosion resistance, and long lifespan, have solved the pain points of traditional crucibles, becoming the “upgraded standard” in the sintering process of lithium-ion battery cathode materials. With the rapid growth of the downstream lithium-ion battery industry, policy support for high-end materials, and continuous breakthroughs in manufacturing technology, the silicon carbide crucible market is poised for explosive growth. According to industry forecasts, the global lithium-ion battery crucible market size will increase, with silicon carbide crucibles also accounting for a larger share, becoming a key link in the new energy industry chain that combines technological barriers and market potential.

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Jul 16 2026

What Types of Special Kiln Furniture are Used to Support Ceramic Blanks?

Sintering vessels are specialized kiln furniture used to support the fired ceramic blanks or to hold powders, such as cathode materials, magnetic powders, and high-purity ceramic materials, which are calcined and synthesized before undergoing heat treatment in roller kilns, pusher kilns, or tunnel kilns. Depending on the firing process of the user, this kiln furniture will be subjected to different heating conditions, and the material of these products depends on the type of sintered body and the heat treatment process.

Saggers/Crucibles

Saggers are used to hold powders (lithium-ion battery cathode materials, magnetic powders, high-purity ceramic powders) for heat treatment in roller kilns, pusher kilns, and tunnel kilns. They are generally formed using extrusion, machine pressing, casting, and isostatic pressing processes, with the appropriate forming process selected based on the composition and structure of the product. Widely used materials include cordierite-mullite, corundum-mullite, silicon carbide, and graphite. Their application is most prevalent in the synthesis of lithium-ion cathode materials.

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Cordierite-mullite saggers are widely used in the field of lithium-ion battery cathode materials due to their excellent thermal shock resistance and economic efficiency.

Aluminum-silicon saggers generally have a short lifespan due to the strong alkalinity and low melting point of lithium carbonate/lithium hydroxide, which are highly corrosive to acidic refractory materials.

Corundum saggers are mainly used for calcining some high-purity powders in environments with less severe thermal shock conditions and high operating temperatures. For example, the calcination of high-purity alumina powder requires the sagger to be fired at 1800℃, using alumina active powder with an Al2O3 content of 99.9wt% and low-sodium white corundum. The binder uses low-ash content (Ash ≤ 0.01wt%), ensuring effective impurity control throughout the raw material process, and achieving a low coefficient of thermal expansion through sufficient high-temperature firing.

Graphite and silicon carbide saggers possess high thermal conductivity, high-temperature resistance, and excellent thermal shock resistance. While their oxidation resistance is poor, they exhibit excellent resistance to alkaline corrosion under reducing atmospheres. Graphite saggers are commonly used as containers for loading materials during high-temperature sintering in reducing atmospheres, applied in lithium iron phosphate sintering and electromagnetic material sintering. Traditional graphite saggers are produced through machining, which is inefficient and costly. Silicon carbide saggers are also widely used in pharmaceuticals, fine chemicals, engineering metallurgy, and pickling industries.

Firing Plates

Firing plates must withstand the thrust of movement and the friction of loading and unloading products during service, and must not crack under thermal cycling. While meeting the thermal shock resistance requirements, improving the bending and crack resistance of the firing plate is crucial. The firing plate material must have excellent chemical inertness and not react with the products it supports. Firing plate materials include alumina, zirconium oxide, and composite materials, mainly used in electronic ceramics and special ceramics.

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Corundum firing plates refer to high-end kiln furniture with α-Al₂O₃ as the main crystalline phase. They possess excellent properties such as high strength, corrosion resistance, high temperature resistance, and wear resistance. They exhibit minimal deformation at high temperatures (>1650℃), but have high sintering temperatures and poor thermal shock stability. During the firing process of lead zirconate titanate piezoelectric ceramics, corundum firing plates face phenomena such as central warping, surface layered powdering, and peeling.

Zirconia is a corrosion-resistant, high-temperature refractory oxide. Zirconia sintering plates are frequently used as sintering pads in dielectric ceramics, powder metallurgy, chip capacitors, and ferrite magnetic materials to prevent parts from sticking together during sintering and to prevent the loss of electromagnetic properties of electronic components.

The firing temperature of conductive ceramics and device ceramics is generally between 1400 and 1650℃, and they are mostly corundum-mullite, corundum, or composite materials.

Barium titanate ceramics are a star product in the electronic ceramics industry. Sintering is a crucial step in its preparation process, determining the densification and microstructure of barium titanate; therefore, the quality of the sintering plate is particularly important. Because barium titanate has a low melting point (1625℃), high density, and is alkaline, traditional aluminosilicate kiln furniture easily reacts with it, leading to product contamination. Foreign kiln furniture manufacturers have applied plasma spraying technology to the sintering plate preparation process. The firing plate features a corundum-mullite interlayer and a zirconium oxide cladding coating, offering high thermal shock resistance and preventing reaction or adhesion with the fired chip-type multilayer ceramic capacitors.

With industrial development, the variety of products fired has increased, expanding the application areas of kiln furniture beyond ceramics to include fine chemicals and lithium-ion batteries. The performance requirements for kiln furniture materials, considering the characteristics of the fired products, are no longer limited to mechanical strength and thermal shock stability. Some applications also require excellent corrosion resistance and non-contamination of the fired products. Different corrosive media necessitate different requirements for kiln furniture materials. For example, in the production of lithium-ion battery cathode materials, kiln furniture materials must possess excellent thermal shock stability and resistance to alkaline lithium compounds. In the production of piezoelectric ceramics, kiln furniture materials must resist lead and its compounds.

Rongsheng High-Performance Corundum-Mullite Kiln Furniture

With the rapid development of science and technology and the economy, magnetic materials, functional ceramics, and electronic ceramics have been widely used in information, electronics, machinery, and chemical industries. This has also driven the rapid growth in demand for high-performance corundum-mullite kiln furniture materials.

Kiln furniture is a special type of refractory material, primarily serving to support and protect fired products. Product forms mainly include pushers, firing supports, and saggers. During service, kiln furniture is subjected to high temperatures, compression, friction, and thermal cycling, and its damage often manifests as fracture or deformation. Therefore, the key performance requirements for kiln furniture materials lie primarily in their high-temperature mechanical properties, which determine their performance, such as high-temperature flexural strength, high-temperature creep resistance, and thermal shock resistance. Improving these performance characteristics involves the design of the material’s microstructure and its resistance to damage under complex stress conditions under high-temperature loads. This requires in-depth research and development in areas such as raw material selection, matrix material treatment, process control, and thermal stress distribution.

Through rational selection of raw materials, optimized microstructure design, scientific product firing process, and stress distribution calculation, high-performance corundum-mullite kiln furniture has been developed. It can be widely used in the sintering of structural ceramics, electronic ceramics, and powder metallurgy parts.

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Technical Advantages of High-Performance Corundum-Mullite Kiln Furniture

Operating temperature up to 1750℃.
Strong creep resistance.
Meets the requirements of environments with strong thermal shock.

Applications of Corundum-Mullite Kiln Furniture

Corundum-mullite kiln furniture is an essential consumable refractory material in the ceramics industry, characterized by high demand and wide application. It is mainly used in the sintering of high-tech ceramics and powder metallurgy parts, such as electronic ceramics (MLCCs, varistors, magnetic materials, filters), Al2O3 structural ceramics (substrates, ceramic films, spark plugs, grinding media), ZrO2 structural ceramics (zirconia knives, mobile phone backplates, bearings, fiber optic ferrules), stainless steel, titanium alloys, etc.

High-performance corundum-mullite kiln furniture is used in pusher kilns to fire zirconia knives. High-performance corundum-mullite kiln furniture is used in pusher kilns to fire alumina ceramics.

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Jul 1 2026

The Influence of Binder on the Properties of Silicon Carbide Mortar

Silicon carbide fire mortar is used for the construction or bonding of silicon carbide bricks in blast furnaces, silicon carbide bricks in blast furnace cooling walls, silicon carbide bricks in aluminum electrolysis cells, and silicon carbide bricks in ceramic kilns. Currently, silicon carbide fire mortar mainly uses liquid phenolic resin as a binder, which is mixed evenly in a certain amount before construction. The overall structure after construction must have good structural stability and airtightness, and be able to withstand various physicochemical reactions at high temperatures, so that the equipment can operate safely and stably. During the production, transportation, and use of fire putty, pure phenolic resin is brittle, highly toxic, has a high curing temperature, slow speed, and is prone to cracking and has low wear resistance after curing. This results in low production efficiency, high energy and equipment consumption, and the need to dissolve and dilute it with flammable and explosive materials during the mixing process, which seriously pollutes the environment and causes adverse effects. To solve these problems, three binders were used in the experiment, and comparative tests were conducted on three aspects: cone penetration, bonding time, and bonding strength.

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Raw Materials and Proportions of Silicon Carbide Mortar Used in the Experiment

The main raw materials used in the experiment included: silicon carbide particles (0.5–0 mm) and fine powder (≤0.074 mm) with a w(SiC) content of 98.3%; clay fine powder with a w(Al₂O₃) content of 34.2% and a w(SiO₂) content of 48.3%; alumina sol solid fine powder with a w(Al₂O₃) content of 32.3%; Secar 71 cement fine powder; solid water glass fine powder with a modulus of 2.8; and additives.

The aggregate to fine powder was prepared according to a mass ratio of 40:60, and three different binders were added. The samples were numbered A, B, and C, where A represents alumina sol solid, B represents Secar 71 cement, and C represents solid water glass. The numbers correspond to the amount of binder added.

Sample Preparation and Performance Testing

According to the sample composition formula, the prepared materials were poured into a small mixer and dry-mixed for 1 minute. Then, 10% (w) water was added and mixed for 3 minutes, then an appropriate amount of water was added and mixed for another 3 minutes to form a slurry. The cone penetration, bonding time, and flexural bonding strength of each formulation sample were determined according to GB/T 22459—2008 (drying at 110℃ for 24 hours and charring at 1300℃ for 3 hours).

Performance of Silicon Carbide Firemortar with Different Binders

(1) Silicon carbide firemortar using alumina sol as a binder exhibited the best cone penetration after 1 hour of standing. Silicon carbide firemortar using solid water glass as a binder showed the best cone penetration after 0.5 hours. However, silicon carbide firemortar using Secar 71 cement as a binder rarely achieved ideal cone penetration.
(2) In silicon carbide firemortar, when using alumina sol and solid water glass as binders, the bonding time of samples with binder additions between 4% and 10% (w) was within the national standard requirements. However, when using Secar 71 cement as a binder, the bonding time requirement was only met when the binder addition was 2% (w).
(3) Silicon carbide firemortar exhibited the best flexural bond strength after baking and heat treatment when the alumina sol solid addition was 8% (w). The flexural and bond strength properties were best when the solid water glass content was 6% (w) after drying and heat treatment. However, the strength of the Secar 71 cement sample after drying was too low, while the strength after heat treatment increased with the increase in content.

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What type of refractory mortar is used for laying corundum-silicon carbide composite bricks?

When laying corundum-silicon carbide composite bricks, it is essential to use refractory mortar of the same material, namely corundum-silicon carbide refractory mortar. This is because refractory mortars of the same material have identical performance characteristics and can resist the same furnace atmosphere under the same high temperatures or erosion conditions. There are various types of corundum-silicon carbide composite bricks, including precast bricks and sintered corundum-silicon carbide bricks.

Precast bricks do not require refractory mortar. This is because precast bricks are generally produced in small quantities and are cast according to specific brick shapes for specific locations, thus requiring no refractory mortar for laying.

Sintered corundum-silicon carbide composite bricks, however, are sintered at high temperatures and are generally used in areas of high furnace lining temperature and severe erosion and wear. The required quantity is larger than for precast bricks. Therefore, refractory mortar of the same material must be used for laying them, with the refractory mortar acting as a bonding material to seal the gaps between the bricks.

What phenomena occur with refractory mortar under high temperatures?

When preparing corundum-silicon carbide refractory mortar, the amount of silicon carbide added to the corundum-silicon carbide composite bricks must be considered. Generally, the proportion of silicon carbide added to the mortar should match the proportion added to the refractory bricks. This ensures that the performance is essentially the same for the same material. If too much silicon carbide is added, the bonding during construction will be poor, making construction impossible. Forcibly adding a binder to adjust the amount will affect the later strength. If an unbalanced proportion of silicon carbide is not used, or if refractory mortar without silicon carbide is used, the mortar will crack and fall off at high temperatures. Falling mortar will cause the brick layer to settle, leading to furnace shutdowns for maintenance and production delays.

Therefore, corundum-silicon carbide composite bricks must be laid with corundum-silicon carbide refractory mortar. This ensures that the material, atmosphere, operating temperature, and resistance to erosion and abrasion are identical.

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Author: aluminabricks

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Selection of Aggregates

Selection of Corundum Fines

Proportioning for Spinel

Magnesia Content

Silica Fume

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Fireclay Mortar

High-Alumina Mortar

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Refractory Castable Precast Blocks and Refractory Mortar for Furnace Roof Masonry

Phosphate-based Mortar

PA-80 High-Temperature Resistant Mortar

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Methods and Construction Procedures for Using Refractory Mortar

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Performance Characteristics of Gunning Mixes

Main Raw Materials for Basic Gunning Mixes

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Binders and Binder Combinations

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Optimization of Basic Gunning Mix Formulations

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Conclusion: There is no one-size-fits-all furnace, only system compatibility.

Flash Furnace: Suitable for stable concentrates and large-scale continuous production.

Top-blown furnaces: Suitable for strong stirring and handling complex materials

Bottom-blown furnace: Suitable for organizing reactions from within the molten pool

Side-blown furnaces: Suitable for continuous operation and control of the side reaction zone

Choosing a furnace type shouldn’t be based solely on the furnace itself.

Furnace Selection: Essentially System Matching

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Performance and Applications of Acid-Resistant Castables

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Technical Performance of Acid-Resistant Castables

Applications of Acid-Resistant Castables

Acid-resistant castable refractory construction requirements:

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Precautions for Acid-Resistant Castable Resin Construction

What is the difference between acid-resistant and alkali-resistant castables?

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Advantages and Characteristics of High-Chromium Bricks

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The Influence of Al2O3-Cr2O3 Solid Solution Particles on the Performance of High-Cr Bricks

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Improving the Sintering Densification of the Matrix

Rongsheng Refractory Materials Manufacturer

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Performance Advantages of Silicon Carbide Lithium-ion Battery Saggers: High-Efficiency Sintering

Ultra-High Temperature Resistance and Thermal Stability

Extreme Corrosion Resistance: Resistant to Molten Salt and Atmosphere Erosion

High Thermal Conductivity and Low Energy Consumption: Accelerated Sintering, Cost Reduction and Efficiency Improvement

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Ultra-long lifespan: Overall cost reduction of over 60%

Application Areas of Silicon Carbide Saggers

Explosive Downstream Demand: A “Must-Have” for New Energy Vehicles and Energy Storage

Dual Catalysts of Policy and Technology: Accelerated Replacement Process

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Technological Iteration: Breakthroughs in Cost Reduction and Scale

Core Carrier for Industrial Upgrading

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Saggers/Crucibles

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Firing Plates

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Rongsheng High-Performance Corundum-Mullite Kiln Furniture

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Technical Advantages of High-Performance Corundum-Mullite Kiln Furniture

Applications of Corundum-Mullite Kiln Furniture

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Raw Materials and Proportions of Silicon Carbide Mortar Used in the Experiment

Sample Preparation and Performance Testing

Performance of Silicon Carbide Firemortar with Different Binders

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What type of refractory mortar is used for laying corundum-silicon carbide composite bricks?

What phenomena occur with refractory mortar under high temperatures?