Lime Kiln Refractory Bricks - Refractory Materials for Kilns

Limekiln refractory brick is a kind of refractory material used in a lime kiln, usually made of high alumina, clay, or corundum. Because lime kiln has the characteristics of high temperature and strong corrosion, the performance requirements of refractory materials are relatively high, and lime kiln refractory brick is designed to meet these requirements.

Lime Kiln Refractory Brick Lining

Characteristics of lime kiln refractory bricks

1. High temperature performance. Limekiln refractory bricks can withstand high temperatures, have high thermal stability, and can be used in environments up to 1300°C or above.

2. Corrosion resistance. Since the gases and materials in the lime kiln are corrosive, lime kiln refractory bricks need to have good corrosion resistance.

3. Good thermal insulation performance. Lime kiln refractory bricks can insulate, reduce heat transfer, and improve energy utilization.

4. Wear resistance. In harsh environments such as high temperatures and corrosion, lime kiln refractory bricks need to have good wear resistance to ensure their service life.

Application of lime kiln refractory bricks

Lime kiln refractory bricks are widely used in various types of lime kilns, including vertical kilns, rotary kilns, etc. During use, it is necessary to select appropriate refractory brick models and specifications according to different furnace types and use environments. At the same time, the following points should be noted during use:

• 1. During installation, it should be carried out according to the drawings provided by the manufacturer to ensure the installation quality and service life.
• 2. Avoid collision and extrusion during use to avoid damage.
• 3. Regularly inspect and maintain, discover and solve problems in time, and ensure the normal operation of the lime kiln.

Rongsheng Refractory Brick Manufacturer

Lime kiln refractory bricks are an indispensable part of the lime kiln furnace. Their performance and service life are directly related to the normal operation and production efficiency of the lime kiln. With the continuous development and progress of technology, lime kiln refractory bricks will continue to innovate and develop, providing better support and guarantee for the development of the lime industry.

When choosing suitable lime kiln rotary kiln refractory bricks, we need to analyze the characteristics of different types of refractory bricks in detail. According to the production process and the actual situation of the lime kiln rotary kiln, Rongsheng refractory brick manufacturer can customize refractory lining bricks. For example, for high temperature and high pressure environments, we can choose high alumina refractory bricks or magnesium-alumina refractory bricks. For occasions that require corrosion resistance, we can choose silicate refractory bricks. In the selection process, we need to consider a variety of factors, such as refractoriness, stability, durability, and cost. Contact Rongsheng for free solutions and quotes.

Magnesia Spinel Refractory Brick Manufacturer

In the vast land of China, there is a powerful manufacturer and seller of refractory materials, Rongsheng Refractory Material Factory. Rongsheng Factory has its own unique concept, high-quality products and comprehensive customer service in the field of refractory materials. Magnesia refractory brick, magnesium spinel refractory brick manufacturer. Contact us for free samples and quotes.

RS Magnesia Spinel Refractory Brick Manufacturer

Magnesia Alumina Spinel Brick

Magnesium-aluminum spinel has a series of excellent properties such as high melting point, good thermal shock stability, and resistance to slag erosion. It has been widely used in refractory materials and other industrial fields.

At present, the most common method for preparing magnesium-aluminum spinel is solid-phase reaction synthesis. That is, oxides, chloride oxides or carbonates are used as raw materials, and the raw materials are mixed and pressed into billets and then reacted at high temperature (greater than 1400°C) to prepare spinel. The electric melting method is another commonly used method for synthesizing spinel in industry, which also has disadvantages such as high energy consumption. Although wet chemical methods such as sol-gel method and hydrothermal method can synthesize spinel at a lower temperature, their operation process is complicated, the equipment required is expensive, and the cost is too high to meet the needs of large-scale industrial production.

Magnesium-aluminum spinel bricks produced with magnesia sand and magnesium-aluminum spinel sand as raw materials are usually called magnesium-aluminum (periclite-spinel bricks). The magnesia sand raw material used to produce periclase spinel bricks is required to have as low an impurity content as possible (especially CaO).

Domestic sintered magnesia MS95, MS97, MS97.5, and DMS97 are widely used. Spinel sand is used as granular material, and magnesia sand is used as fine powder and part of the granular material. According to the mixing, forming, and firing process of high-grade magnesia-alumina bricks, products with good high-temperature performance and high thermal shock stability can be produced.

Magnesia-alumina spinel bricks are often used in cement rotary kilns, glass kiln lattices, mixed iron furnaces, and refractory kilns with large temperature changes.

Magnesium Aluminum Chrome Spinel Brick

The magnesium aluminum chrome spinel brick system is the periclase/magnesium aluminum chrome spinel system: MgO-R2O3 (Cr2O3, Al2O3) system. In order to facilitate the comparison of the production of magnesium aluminum chrome products, Cr2O3 is introduced into MgO in the form of chromite, and the manufacturing process often accompanies the appearance of sesquioxides such as Cr2O3, Al2O3, and Fe2O3.

First of all, from the perspective of high temperature resistance and slag resistance, the MgO-MgO·Cr2O3 system has advantages in the MgO-R2O3 system. In addition to its high eutectic temperature (2350℃), it also lies in the low solubility of Cr2O3 in the silicate liquid phase.

As we all know, lower solubility should have stronger crystallization ability. It can effectively reduce the intercrystalline interface energy, so that the silicate liquid phase tends to move into the intergranular gap in an isolated state. It is easy to achieve direct bonding between periclase grains or through magnesium chrome spinel bridges, which can effectively improve high temperature strength and inhibit slag penetration, and improve slag resistance. However, Cr2O3 is highly volatile and has poor stability at high temperatures, especially under vacuum conditions.

Secondly, from the perspective of thermal shock resistance, the MgO-MgO·Al2O3 system is more superior. Because the solid solution-peptization effect of MgO·Al2O3 or Al2O3 in MgO at high temperature is much weaker than that of MgO·Cr2O3 or Cr2O3, especially MgO·Fe2O3 or Fe2O3, and the high-temperature vapor pressure of MgO·Al2O3 above 1600℃ is also lower than that of MgO·Cr2O3. Therefore, the MgO-MgO·Al2O3 system material is more stable when the temperature fluctuates and has good thermal shock resistance.

When the MgO/R2O3 ratio is constant, the MgO-MgO·Al2O3 and MgO-MgO·Cr2O3 systems are compared. It can be inferred that in the molten MgO-MgO·Al2O3 system material, there are fewer precipitated spinels in the periclase grains, and more spinels between the grains. MgO-MgO·Cr2O3 system materials have more intracrystalline precipitated spinel and less intercrystalline spinel. Obviously, changing the proportion of each component in R2O3 can adjust the distribution of spinel phase and change the microstructure.

Magnesium Iron Aluminum Spinel Brick

Magnesia-alumina spinel bricks are mainly used in cement kiln firing zones. Traditional refractory materials used in cement kiln firing zones are mainly magnesia-chrome refractory materials. The highly toxic hexavalent chromium that can be dissolved in water in magnesia-chrome bricks after use will cause serious environmental pollution. Finding chromium-free alternative products for cement kilns has been recognized by experts. Magnesia-alumina spinel bricks were proposed by RHI in the 1990s. It is a mixture of magnesia sand and pre-synthesized alumina spinel, and fired at high temperature under certain processes. It has now been widely used in the lining of cement rotary kilns to replace magnesia-chrome bricks.

The microstructural characteristics of magnesia-alumina spinel are relatively complex, mainly a combination of magnesia sand microstructure and alumina spinel microstructure. The interface between magnesia sand and alumina spinel is closely combined through the mutual diffusion of Mg2+, Al3+, and Fe2+ ions, realizing direct bonding of materials.

Please contact us to purchase high-quality refractory products. Refractory lining materials, refractory services, and furnace lining materials for sale.

Unshaped Refractory Lining Materials for Cupola Linings

Different from the traditional cupola ladle lining, the two types of ladles built with refractory ramming material or refractory castable material can greatly increase the working life of the ladle lining and reduce the number of spare ladles. What are the specific material choices for the two new types of ladle linings?

High-Alumina Refractory Ramming Materials

Refractory Ramming Material Lining

Ramming material is a general term for plastic refractory materials composed of refractory aggregate, binder, and moisture. The mineral composition of refractory aggregate coated with ramming material is generally bauxite, corundum, quartz sand, and quartz powder. The chemical composition is mainly composed of alumina (Al2O3) and silicon oxide (SiO2) two parts. Due to the different mineral compositions and particle sizes, various suppliers have developed a variety of packaging ramming material specifications. At present, the chemical composition of the lining ramming material, among which the higher the alumina content, the higher the use temperature, the greater the drying density, the stronger the thermal conductivity of the lining, and the longer the life of the lining.

Bauxite, corundum, quartz sand, and quartz powder in the lining ramming material are materials with high thermal conductivity. In addition, due to the size grading of refractory materials, the compaction density of ramming materials is larger. Therefore, the thermal conductivity of the lining ramming material is higher. If the ramming material is used completely to build the lining, the heat conduction of the lining causes the temperature of the iron liquid to drop more. Therefore, before using the lining ramming material to build the lining, a heat insulation layer of a certain thickness should be designed inside the cladding.

The ramming die must be prepared in advance to build the packing lining with ramming material. The ramming die is specially designed according to the ladle structure and lining to be located, and either has a certain inclination or has the performance of split disassembly. When building the lining, first use the ramming material layer by layer, ramming the bottom to a certain thickness. Then, the ramming mold is placed in the shell, and the ramming material is filled layer by layer to the mouth of the bag. Finally, pull out or remove the ramming die, and brush the surface of the lining with graphite powder coating.

The construction quality of ramming material lining has a decisive influence on the life of the lining, and the difference in construction quality may make the same material have different life. When building the lining with ramming material, it should be rammed tightly. The ramming compactness must conform to the drying compactness range of the lining material. The drying and roasting temperature and time of the packaging should also meet the technical requirements of the relevant products.

SiC Refractory Castable Lining

Refractory Castable Lining

Refractory castable is a class of amorphous refractory materials with cement as binder. The mineral composition of the refractory aggregate is the same as that of the refractory aggregate used for lining ramming. Calcium oxide (CaO) is an essential component of cement as the binder lining cement castable is high alumina cement. Therefore, the calcium oxide content can indirectly represent the cement content in the castable. Cement-lined castable can be divided into general cement castable, low cement castable and ultra-low cement castable. The lower the cement content, the higher the refractoriness of the material. Chemical composition range of coated low cement and ultra low cement castables. Among them, the higher the Al2O3 and the lower the CaO, the higher the refractoriness and the longer the life of the lining.

Before building the lining with refractory castable, it is necessary to make the casting mold with thin steel plate in advance, and the casting mold needs a certain taper to facilitate smooth pulling out after pouring. A certain thickness of heat insulation layer is set in the interior of the cladding to improve the heat preservation property of the ladle before constructing the cladding with cement castable. During construction, the bottom is covered with castable to the required thickness. After vibrating with a vibrator commonly used in concrete construction, the casting mold is fixed in the cladding. The castable is then filled layer by layer between the insulation layer and the casting mold. At the same time, vibrator is used to vibrate to the envelope, and the casting mold is pulled out in time after the initial solidification of the castable. Finally, the coating surface is coated with graphite powder.

Using low cement or ultra-low cement castable to build the lining is short in construction time, less in physical exertion, and easy to ensure the construction quality. At the same time, the lining can be repaired after partial damage. Therefore, the lining life is long and the consumption of tons of liquid iron refractory is low.

Unshaped Refractory Lining Materials for Cupola

Selection of Amorphous Refractory Castable for Cupola Lining

Cupola is subjected to high temperature and chemical erosion during melting. The melting time of cupola is 6~10 hours, the furnace lining erosion is large, and the furnace condition is unstable.

The corrosive atmosphere of furnace lining has a high requirement on the selection of refractory castable. It is better to use refractory castable with 70%~80% aluminum content in the feeding area and flow channel. Because of the high aluminum content, the high temperature strength and wear resistance and thermal shock performance are good, and the resistance to alternating hot and cold shock is strong.

The main parts of the cupola are hearth, bridge and slag separator. These parts have slag contact, chemical erosion is serious. Refractory castables with high aluminum content, due to the purity of the substrate itself, less impurities, strong resistance to iron wash, and very good oxidation resistance.

When selecting castable material for cupola lining, the slag composition should be considered, because there is a certain proportion of limestone in the burned material. Limestone has an alkaline composition, so the refractory castable used should have the ability to resist alkali erosion. That is, there should be a silicon carbide component in the castable, silicon carbide wear resistance and slag erosion resistance.

If it is alkaline erosion, magnesium or spinel are good choices. If spinel and silicon carbide are added to the castable, then this composite material is the most ideal material. However, silicon carbide and spinel should be added in different proportions according to the different slag composition.

If the top of the furnace lining can also be selected plastic, so easy to construction. Plastic should also consider the composition of ceramic combination, it is best to use phosphoric acid combination of plastic, do not use water glass combination. Because phosphate bonded plastic, strength and high temperature resistance are good. If castable is selected, plastic is still used for daily repair, which can shorten the maintenance time.

It should also be noted that in the furnace production process if the coke does this cupola melting heat source. It is necessary to control the quality of coke to stabilize the use of furnace lining.

In the final analysis, the refractory castable selected for the lining is still a refractory castable with high aluminum content. Because the pure castable has good wear resistance, the castable with silicon carbide or spinel composition has better corrosion resistance.

Are There Any Lightweight Spraying Refractory Coatings?

During the construction process of refractory spray paint material, the material is compacted by repeated and continuous impact of the sprayed material. Therefore, the sprayed coating has a better density and mechanical strength. Refractory spray paint can be used in hot blast duct systems, blast furnace throats, furnace tops and gas outlet pipe systems, furnace bottom foundations, and blast furnace and hot blast furnace linings.

RS Spraying Refractory Coatings for Sale

What is Refractory Coating?

The construction of spray refractory coating actually combines transportation, pouring, or tamping into one process. It does not require or only requires a single-sided formwork. The process is simple, highly efficient, and has good adaptability. During the construction process of refractory spray coating, the repeated and continuous impact of cement, aggregate, and other constituent materials causes the sprayed materials to be compacted, so the spray coating has better density and mechanical strength.

Are There Any Lightweight Spraying Refractory Coatings?

High-temperature refractory coatings and spray coatings are unshaped materials among refractory materials. Therefore, there are also light, heavy, and semi-heavy ones.

Heavy refractory spray paint is relative to light refractory spray paint. Light spray paint refers to a density of 0.5-1.3g/cm3, and medium-heavy spray paint refers to a density of 1.3-1.8g/cm3. Then the density of heavy spray paint is the largest, and its volume density is greater than 1.8g/cm3. Lightweight spray coatings are used as thermal insulation and thermal insulation linings, while medium and heavy spray coatings can be used as both thermal insulation linings and working linings for low and medium-temperature atmosphere furnaces. Heavy spray coatings are mainly used as high-temperature service linings.

Lightweight Spraying Refractory Coating

Applications of High-Temperature Refractory Coating Products

Refractory spray paint is mainly used as a sealing material for the lining of thermal equipment in industrial furnaces. It can be used in hot blast duct systems, blast furnace throats, furnace tops and gas outlet pipe systems, furnace bottom foundations, and blast furnace and hot blast furnace linings.

The lightweight spray coating plays the role of thermal insulation, while the semi-heavy spray coating not only plays the role of thermal insulation, but also can be used as a working layer in furnace linings, chimneys, and pipes where the temperature does not exceed 1000°C.

Heavy refractory spray coatings are generally used for lining hot blast furnaces and blast furnaces and are also used for emergency repairs in lime kiln linings. At present, some domestic manufacturers also spray directly on the lining of the white ash shaft kiln as the working layer. The advantage of refractory spray paint is that it can be applied quickly.

Semi-heavy spray paint is used for flue and chimney linings because the temperature of the flue and chimney linings is not high and there cannot be adequate lining materials. Therefore, many manufacturers choose semi-heavy spray coatings for both thermal insulation and working layers. In this way, the inner diameter space is saved, and it can also prevent wind and smoke erosion.

The lightweight spray paint is used as a thermal insulation layer, and when used, if the area to be used is small, it can also be applied directly. Because the construction time of lightweight spray paint is short, in general, it is convenient and quick to use lightweight spray paint when the usage is large. Because hundreds of tons of spray paint will be sprayed within a few hours.

However, spray coatings have a rebound rate, and the national standard is 20%. However, the rebound rate of spray coatings currently on the market is around 8-10%. During construction, professionals must cooperate with the sprayer for normal use. A small amount can also be applied manually, and just use putty when applying.

Spray coatings are divided into neutral, acidic, and alkaline materials. When using, select the material suitable for the furnace lining for spraying according to the atmosphere of the furnace lining. Because the furnace lining atmosphere and materials are in the same atmosphere, the furnace lining atmosphere is good and the service life is long.

Rongsheng Refractory Materials Manufacturer is a powerful manufacturer and seller of refractory materials. Our environmentally friendly, fully automatic unshaped refractory material production line provides high-quality refractory lining materials for various industrial kilns. Product quality is guaranteed, and the spray refractory coating formula can be customized. The professional technical and construction team provides pre-sales technology and after-sales construction services for refractory lining solutions. Contact us to get free samples and quotes.

Rongsheng Refractory Plastic Manufacturer

Refractory plastic is composed of refractory (bauxite) aggregate and refractory powder, mixed in proportion, adding binders such as plastic white mud or clay and an appropriate amount of plasticizer. It is an unshaped refractory material that is in the form of bulk material or paste and maintains high plasticity for a long time.

Classification of refractory plastics: According to the types of refractory aggregates, they are divided into clay, high alumina, mullite corundum, chromium, silicon carbide, and zirconium. According to the type of binder, it is divided into composite binders such as raw clay and aluminum sulfate, phosphoric acid, phosphate, water glass, and resin. According to the normal temperature hardening properties, it is divided into air-hardening and thermosetting refractory plastics.

RS High Alumina Plastic Refractory

Refractory Plastic Properties

To ensure normal use at high temperatures and smooth construction, refractory plastics should have the following basic characteristics:

1. It has a shelf life of construction time to ensure that the molding performance remains unchanged during the specified storage period.

2. It has good plasticity for easy construction.

3. It has good strength after curing at room temperature so that the frame can be dismantled after construction.

4. It has good high-temperature volume stability to prevent damage to the furnace lining structure due to excessive deformation.

Applications of Refractory Plastics

Refractory plastics are mainly used in the linings and maintenance of furnaces, cyclones, superheaters, flues, etc. of various power station boilers, and in the linings of heating furnace roofs, water-cooled walls, etc. Materials can be divided into high aluminum, clay, corundum, corundum silicon carbide, silicon, magnesia, chromium, etc. According to the classification of binders, there are white mud binders, aluminum phosphate binders, water glass binders, sulfate binders, aluminate binders, etc.

Advantages of Rongsheng Refractory Plastics

Application Advantages of Rongsheng Refractory Plastics

The characteristic of refractory plastic is that it can be constructed into any shape and the construction period is short. It can be constructed by ramming, or it can be repaired according to the damaged location. Moreover, it can be put into use directly according to the furnace temperature without baking. It is a good repair material.

Fire-resistant plastic has good wear resistance, strong plasticity, and good bonding properties. It is mostly used in circulating fluidized bed boilers or heating furnaces. Plastics can be produced in many forms during the production process. If the construction is to be put into use immediately, one-third of the cementing material can be added during production. Trapped materials first, go to the construction site and add the other two-thirds of the PA80 glue, and then the construction can be started. You can also add all the glue into the material, but the packaging must be scientific. Open the plastic packaging at the construction site and put it into use.

The raw material of refractory plastic can be corundum, burnt gemstone, or high-aluminum aggregate. It can be made into plastics of different grades and qualities. However, the cementing material used must be PA80 glue. Glue is made by boiling aluminum dihydrogen phosphate and phosphoric acid. It can be added first or on-site. If it is added on-site, there still needs to be a process of trapping the material to achieve the best results.

Different grades of refractory plastics are determined according to the furnace lining atmosphere, temperature, and wear resistance of the used parts. If the temperature is low, materials suitable for the temperature can be made and produced, and the price is relatively cheap. If the temperature is high or too high, corundum or even zirconium corundum must be used to make it meet the needs of the furnace lining.

The function of refractory plastic is that it has strong plasticity and can be used on the stovetop. It can also be used for pounding on the furnace wall.

To purchase high-quality refractory materials and refractory plastic products, please contact us. Get free samples and quotes.

High Performance Lightweight High Aluminum Castable

To improve the energy-saving effect of thermal kilns, the number and scope of applications of lightweight castables are gradually expanding. From the permanent layer, the insulation layer to the working layer, it extends from the medium and low-temperature areas to the medium and high-temperature areas and transitions from a low-load environment to a high-load environment. At present, the technical performance of lightweight high-aluminum castables used in working layers at medium-low temperatures (<1 200°C) and high temperatures (>1 500°C) has been basically mature. However, the performance of lightweight castables used in the medium and high-temperature range (1 200 ~ 1 500 ℃) needs to be improved. To meet the new requirements for the use of lightweight high-aluminum castables, it is first necessary to understand the impact of the selection and configuration of lightweight aggregates on their performance. RS refractory material manufacturer can provide high-quality refractory lining products for high-temperature industrial furnace linings.

Lightweight High Aluminum Castable

The raw material configuration of traditional lightweight high-aluminum castables mainly uses lightweight aggregates and heavy fine powders. The lightweight aggregate used has larger pore diameters and lower strength, so the thermal conductivity of the lightweight castable is higher. At the same time, the low strength of the aggregate affects the overall strength of the lightweight castable, limiting its use at higher temperatures. Therefore, microporous aggregates and high-strength aggregates are used. The raw materials used mainly include microporous lightweight mullite and complex-phase hollow spheres. High alumina bauxite, floating beads, kyanite, silica micro powder, alumina micro powder, pure calcium aluminate cement, raw bauxite powder, andalusite, pore-forming agent D, pore-forming agent C, etc.

The Choice of Lightweight Aggregates

To meet the construction and high-temperature performance of lightweight castables, lightweight mullite, and complex-phase hollow balls are selected as lightweight aggregates. Multiphase hollow spheres were used to gradually replace lightweight mullite to study the effect on the properties of the castables. The wall thickness of the multiphase hollow spheres is 0.3~0.5 mm, the particle size is 3~7 mm, and its packing density is 0.60 g/cm3. The packing density of microporous mullite is 0.80 g/cm3.

Effect of adding amount of multi-phase hollow spheres on the volume density of castables

When the amount of multiphase hollow spheres increased from 0 to 40%, the bulk density of the sample dropped from 1.86 g/cm3 to 1.68 g/cm3 after baking at 110 °C × 24 h. The bulk density also shows the same trend after high-temperature firing. Since the packing density of the composite hollow spheres is smaller than that of the lightweight mullite aggregate, the bulk density of the castables shows a downward trend as its addition amount increases. That is, the effect of complex-phase hollow balls on reducing the volume density of castables is greater than that of lightweight mullite.

Effect of the Adding Amount of Complex Phase Hollow Balls on the Normal Temperature Compressive Strength of Castables

The changing trend of normal temperature compressive strength of castables after adding different proportions of multi-phase hollow spheres. As the amount of composite hollow balls increases, the normal temperature compressive strength of the castables after baking and high-temperature firing shows an upward trend. Since the strength of the composite hollow sphere, aggregate is higher than that of the lightweight mullite aggregate, and the surface of the composite hollow sphere is dense, its water absorption rate is lower than that of the lightweight mullite aggregate. At the same time, the spherical aggregate is beneficial to improving the fluidity of the castable, reducing the amount of water added to the castable, and is also beneficial to improving the strength of the sample. Therefore, the reinforcing effect of complex hollow spheres on castables is greater than that of light mullite.

Effect of the Adding Amount of Complex Phase Hollow Spheres on Thermal Conductivity of Castables

As the amount of multiphase hollow spheres increases, the thermal conductivity of the sample shows a downward trend. Since the complex-phase hollow balls have a hollow structure, the air is enclosed in the holes, which has a good heat insulation effect. Therefore, the thermal conductivity of the castable decreases after adding complex-phase hollow balls. Since the pore diameter of the multi-phase hollow sphere is larger, the effect of convective heat transfer will increase at high temperatures. As a result, the effect of reducing the thermal conductivity of the castable at 1000°C is not as obvious as that at 700°C.

Microporous lightweight mullite aggregate is beneficial to reducing the thermal conductivity of castables, but its strength is low. Complex-phase hollow spheres are beneficial to improving the strength of castables, but their effect on reducing thermal conductivity is limited. Due to the low density of composite hollow spheres, taking into account the uniform dispersion of different aggregates and taking into account various properties, the appropriate addition amount of both aggregates is 20% to 30%.

To purchase high-quality lightweight high-aluminum castables, please contact Rongsheng Refractory Materials Manufacturer. Our refractory products are of reliable quality and our after-sales service is guaranteed.

Aluminum-Magnesium Castables Combination Methods

 Aluminum-magnesium castable is a refractory castable with bauxite and magnesium oxide as its main components. It is widely used in the industrial practice of out-of-furnace refining and ladle refractory materials. The MgO can be added in the form of magnesia or pre-synthesized spinel. Aluminum-magnesium castables can be divided into different types. According to different raw materials, it is divided into high-purity corundum-spinel castables and low-purity bauxite-spinel castables. According to the different ways of introducing spinel, it can be divided into aluminum-spinel castable (Al2O3-MA castable) and aluminum-magnesium castable (Al2O3-MgO castable). According to the bonding method, it can be divided into cement-bonded, hydrated bonded, silica powder bonded, magnesium silicon water bonded, and other castables.

Aluminum-Magnesium Castables

How to Combine Aluminum-Magnesium Castables

Binders are also an important component of aluminum-magnesium castables. The bonding methods used in aluminum-magnesium castables are generally calcium aluminate cement bonding, silica powder bonding, hydrated alumina bonding, sol bonding, magnesium silicon water bonding, etc.

(a) Cement bonding

In the early stages of the development of aluminum-magnesium castables, pure calcium aluminate cement was used for bonding. This is because cement calcium aluminate reacts with Al2O3 in the matrix to form CA6, which is a highly refractory phase. However, as the amount of cement added increases, the fluidity of the castable decreases. At the same time, due to excessive CaO content at high temperatures, it will react with SiO2, Al2O3, and MgO in the matrix to form a low melting phase. As a result, the high-temperature performance of the castable is reduced. Zhang Wenjie et al. studied the effect of the amount of water added to cement on the thermal expansion behavior of aluminum-magnesium castables after high-temperature firing. The results show that as the amount of cement added increases, the CA2 and CA6 phases in the sample increase, and the linear change rate of the sample after high-temperature heat treatment increases. Gu Huazhi et al. studied the effects of silica powder, magnesia, and cement on the properties of high-purity aluminum-magnesium castables. Studies have pointed out that pure calcium aluminate cement and Al2O3 fine powder in the matrix begin to react at about 1000°C, and the reaction generates CA2 and CA6. The reaction is accompanied by volume expansion, which can reduce the strength ratio after high-to-medium temperature firing and also contribute to the improvement of the high-temperature performance of the sample.

(b)MgO-SiO2-H2O combination

There are many studies on MgO-SiO2-H2O bonding and condensation bonding. The combination of MgO-SiO2-H2O is used in aluminum-magnesium castables. On the one hand, due to the polymerization of SiO2 gel formed by the interaction between SiO2 powder and water, the amount of water added is reduced and the fluidity of the castables is greatly improved. On the other hand, the combination of MgO-SiO2-H2O can inhibit magnesia hydration. However, if too much silica powder is added, it will form a low melting point phase with impurities in the matrix. At the same time, the forsterite phase formed by the reaction of magnesia and silica powder in the matrix has poor thermal shock stability at high temperatures.