rsrefractorycastable, Author at Rongsheng Refractory Castable Cement for Sale Manufacturer and Supplier

Construction Requirements of Refractory Castables for Tubular Heating Furnace Linings

May 1, 2025 by rsrefractorycastable

Tubular heating furnace lining construction regulations. Construction Requirements for Refractory Castables and Ceramic Fibers for Tubular Heating Furnace Linings. In the lining design of tubular heating furnaces for petrochemicals, the main application is refractory castables and ceramic fiber products. Its structure can be divided into castable lining structure, ceramic fiber structure, and composite lining structure. During the construction and installation process, it must be carried out in accordance with the following regulations:

Under ambient temperature of 27℃ and windless conditions, the design temperature of the outer surface of the furnace body and hot smoke duct should not exceed 80℃.
The design of the lining structure should allow all components to expand appropriately. When using multi-layer or composite linings, the joints should not continuously penetrate the lining.
Unless otherwise specified, the allowable operating temperature of any layer of refractory material should be at least 165℃ higher than its calculated hot surface temperature, and the minimum allowable operating temperature of the refractory material of the radiation and shielding section should be 980℃.
The minimum operating temperature of the burner brick should be 1650℃.
The manhole door should be protected by refractory materials with the same thermal insulation performance as the surrounding refractory layer to avoid direct radiation.
In addition to the cast structure lining, an anti-corrosion layer should be applied to the inner side of the furnace wall steel plate.

Monolithic Refractory Castables Lining Structure

Hydraulic castable lining is applicable to all parts of the heating furnace. The type of castable material should be selected according to its use temperature and should comply with the relevant provisions of SH/T3115.
For double-layer castable lining, the minimum thickness of the hot surface layer should be 75mm. The anchor should support each layer of lining.
When the thickness of the castable lining is greater than 50mm, the height of the anchor should penetrate 70% of the thickness of the lining. The distance between its top and the hot surface should not be less than 12mm.
The anchors should be arranged in a square shape, and the maximum spacing should be 3 times the total thickness of the lining, but should not exceed 300mm on the furnace wall and 225mm on the furnace roof. To avoid the formation of continuous shear surfaces, the fork direction of the anchors should be staggered.
When the total thickness of the lining does not exceed 150mm, the minimum diameter of the anchor nail should be 5mm; when it exceeds 150mm, the minimum diameter of the anchor nail should be 6mm.
The lining thickness of elbow box, tail flue, smoke duct and chimney should not be less than 50mm.
Expansion joints should be left around burner brickwork and pre-burned molded products.
Linings with a density greater than or equal to 970kg/m3 are allowed to be reinforced with metal fibers, and the amount of metal fibers added should not exceed 3% of the dry mix.
When the total amount of heavy metals including sodium in the fuel exceeds 250mg/kg, the exposed hot surface layer should use low iron (iron content not more than 1%) or heavy castables. The density of heavy castables is at least that the content of AI2O3 in its aggregate should not be less than 40%, and the content of SiO2 should not be greater than 35%.

Ceramic Fiber Structure

1) Ceramic fibers with layered or modular structures can be used in all parts of the heating furnace except chimneys and flues.

2) The minimum thickness of the ceramic fiber blanket for the hot surface layer should be 20mm, and the density should not be less than 128kg/m3. The thickness of the ceramic fiber board used for the hot surface layer should not be less than 38mm, and the density should not be less than 240kg/m3. The minimum density of the ceramic fiber blanket used for the back layer should be

3) The allowable operating temperature of any layer of ceramic fiber should be 280℃ higher than the hot surface temperature of the acid meter.

4) The maximum distance from the anchor of the hot surface layer of the ceramic fiber blanket to all edges should be 75mm.

5) The furnace roof anchors are arranged in a rectangular shape. The spacing between them should not exceed the following values:

The ceramic fiber blanket is 300mm wide and the spacing is 150mm×225mm
The ceramic fiber blanket is 600mm wide and the spacing is 225mm×225mm
The ceramic fiber blanket is 900mm wide and the spacing is 225mm×250mm
The ceramic fiber blanket is 1200mm wide and the spacing is 225mm×270mm

6) The furnace wall anchors are arranged in a rectangular shape. The spacing between them should not exceed the following values:

The ceramic fiber blanket is 300mm wide and the spacing is 150mm×300mm
The ceramic fiber blanket is 600mm wide and the spacing is 225mm×300mm
The ceramic fiber blanket is 1200mm wide and the spacing is 270mm×300mm

7) Metal anchors that are not covered by furnace tubes should be completely covered by ceramic fiber modules or protected by ceramic fiber blankets.

8) When the flue gas velocity exceeds 12m/s, the ceramic fiber blanket cannot be used for the hot surface layer:

When the velocity is greater than 12m/s and less than 24m/s, the hot surface layer should use wet blanket, ceramic fiber board or ceramic fiber module.
When the velocity exceeds 24m/S, the hot surface layer should use castable or outer protective layer.

9) When the ceramic fiber blanket is constructed, the maximum dimension direction should be consistent with the flue gas flow direction, and the connection of the blanket on the hot surface layer should be overlapped, and the overlap direction is along the flue gas flow direction. When the hot surface layer uses ceramic fiber board, it should be butt-jointed and the joints should be tight.

10) The ceramic fiber blanket used for the back layer should use a butt joint with a compression amount of at least 25mm at the joint, and all joints of adjacent layers should be staggered.

11) The ceramic fiber module should be constructed according to the vertical seam vertical masonry method, and the staggered mosaic method is only applicable to the furnace top.

12) When the ceramic fiber module is constructed, each side should be compressed to avoid shrinkage cracks.

13) The ceramic fiber module on the furnace roof should be designed so that its anchoring range should be at least greater than 80% of the module width.

14) The anchors should be fixed on the wall panels before the ceramic fiber module is constructed.

15) The anchor assembly should be installed less than 50mm from the module cold surface.

16) The metal parts in the module should be at least austenitic + stainless steel or nickel alloy.

17) When the ceramic fiber structure is used for fuel with a sulfur content greater than 10mg/kg, the inner surface of the shell should be coated with a layer of anti-corrosion paint, and the allowable operating temperature of the anti-corrosion paint should not be less than 180℃.

18) When the sulfur content in the fuel exceeds 500mg/kg, an austenitic stainless steel foil gas barrier layer should be set. The position of the gas barrier layer should be such that the temperature of the gas barrier layer should be 55℃ higher than the calculated dew point under any operating conditions. The edges of the gas barrier layer should overlap by at least 175mm, and the edges and openings should be sealed.

19) Ceramic fiber structures should not be used when the heavy metal content in the fuel exceeds 100 mg/kg.

20) Ceramic fiber structures should not be used in convection sections equipped with soot blowers, steam spray guns or water washing facilities.

21) Anchors should be installed before the wall panels are coated with anti-corrosion paint. The paint should cover the anchors, and the temperature of the uncovered part should be above the acid dew temperature.

Composite Lining Structure

When using a cast hot surface layer, its minimum thickness is 75mm.
The anchoring system should have a fixing and supporting function for each layer.
For each lining, the type and installation of anchors shall comply with the requirements of Articles 2 and 3.
The allowable operating temperature of any layer of material shall comply with the requirements of Articles 2 and 3.
The insulation block shall be made of calcium silicate or slag wool with an operating temperature of at least 900°C. The insulation block can only be used as a backing material. However, it is not allowed to be used when the sulfur content in the liquid fuel exceeds 1% (mass fraction) or the hydrogen sulfide content in the gas fuel exceeds 100mg/kg.
If the sulfur content in the fuel exceeds 10mg/kg, and insulation blocks or ceramic fibers are used as backing insulation, the wall panels should be coated with protective coatings, and the allowable operating temperature of the protective coatings should not be less than 180°C.
If insulation blocks or ceramic fibers are used as the backing layer of the castable, they should be isolated to prevent water from seeping out of the castable.
The density of the ceramic fiber module used as the backing material shall not be less than 190kg/m3, and the density of the ceramic fiber blanket shall not be less than 128kg/m3.

Insulation Compression Non-Sintered High-Strength Low-Temperature Castable for Galvanizing Furnace

April 17, 2025 by rsrefractorycastable

Since 2003, when China Jiangnan Shipbuilding (Group) Co., Ltd. introduced China’s first high-speed pulse flame galvanizing furnace (Weistek®) to Dalian Xinyongshang Technology Co., Ltd., all structural galvanizing furnaces launched by Dalian Xinyongshang Technology Co., Ltd. to the world have been using heat-insulating and pressure-resistant non-sintered low-temperature castables as the bottom insulation material for the furnace bottom insulation structure for more than ten years.

In the hot-dip galvanizing industry in mainland China, whether it is a flat flame galvanizing furnace or a high-speed pulse galvanizing furnace, except for the furnace type launched by Dalian Xinyongshang Technology Co., Ltd. for the hot-dip galvanizing industry, as of the time of publication, all use heavy and lightweight refractory brick masonry structures.

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Advantages of lightweight heat-insulating, pressure-resistant, non-sintered low-temperature castable insulation layer compared to traditional insulation layer

Comparison between “lightweight heat-insulating, pressure-resistant, non-sintered low-temperature castable” and “refractory brick masonry insulation layer”, the application advantages are obvious:

(1) “Refractory brick masonry insulation layer” is built with ordinary refractory bricks. When the galvanizing furnace needs to heat up, the refractory bricks absorb heat, resulting in a slow heating rate. However, when the furnace needs to cool down, the refractory bricks release heat to the outside, resulting in a very slow cooling rate, which affects work efficiency and wastes energy.

Ordinary refractory brick masonry insulation layer has many gaps in the masonry, and employees of hot-dip galvanizing companies cannot meet the precision requirements of thermal kiln masonry. The large number of gaps increases the penetration of heat to the foundation.

Since the zinc pot is placed on the insulation layer, if it is a refractory brick masonry, the zinc pot will expand during the heating process. Due to the strong friction between the pot bottom and the insulation layer masonry, the existing gaps in the refractory brick masonry will be pulled open, causing the gaps to expand further. During the cooling process of the zinc pot, the friction between the pot bottom and the refractory bricks is much smaller than the pressure friction between the refractory bricks. Therefore, the existing cracked masonry gaps cannot be restored. Therefore, the heating and stopping processes that often occur in hot-dip galvanizing production intensify the penetrating transfer of heat to the insulation layer at the bottom of the furnace. This causes a large amount of heat loss and reduces the thermal efficiency of the galvanizing furnace system.

(2) “Lightweight heat-insulating and pressure-resistant non-sintered low-temperature castable” is a refractory material made of refractory aggregates, powders, binders, and admixtures with a certain particle size distribution, also known as bulk refractory materials. It is used for the lining of thermal equipment and is directly baked without going through the firing process. Compared with refractory bricks, it has the characteristics of simple process (because the firing process is omitted), energy saving, low cost, and easy mechanized construction. It is used in the zinc pot base to meet the pressure requirements and has better thermal insulation performance than refractory bricks, reducing the heat dissipation of the galvanizing furnace foundation and significantly improving thermal efficiency.

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Correct application of castables

For the correct application of castables, its characteristics must be mastered. The smaller the bulk density of the castable, the better its thermal insulation performance, but the decrease in bulk density will definitely reduce the compressive strength in the non-sintered state. For the galvanizing furnace system, when using castables, the compressive strength in the non-sintered state must be met first, and the thermal insulation protection of the furnace bottom heat must be met secondly. Therefore, the thermal insulation performance of the furnace bottom can only be improved by reducing the bulk density on the premise that the compressive strength meets the requirements.

The castable is constructed by one-time integral casting, and the micropores are enriched in the insulation layer of the base to form dense air pockets, so it has excellent thermal insulation performance. At the same time, the entire insulation layer has no gaps, which can ensure the integrated shrinkage of the entire insulation layer and reduce the heat transfer path to the earth. The heat is isolated and collected in the furnace combustion chamber to the maximum extent, thereby greatly improving the thermal efficiency.

The thermal insulation structure design of the zinc pot base adopts lightweight, heat-insulating, and compressive non-sintered low-temperature castables, which puts forward more requirements for the application of castables. The smaller the bulk density, the better the thermal insulation performance, but the decrease in bulk density will definitely greatly reduce the compressive strength in the non-sintered state. This will increase the thermal stability of the zinc pot after it is in place. In order to solve this contradiction, Tangshan Kaiping Xinde Hot-dip Galvanizing Technology Co., Ltd. has made gradual improvements in response to the development trend of thermal efficiency, energy saving and consumption reduction of the galvanizing furnace system. Relying on large state-owned enterprise groups and professional refractory research institutes, lightweight heat-insulating and compressive non-sintered low-temperature castables for zinc pot bases have been developed. This castable belongs to a new generation of high-grade amorphous heat-insulating refractory materials without beads.

Lightweight heat-insulating and compressive non-sintered low-temperature castables replace floating beads with “lightweight aggregates“. After the raw materials are burned and crushed, the third-grade aggregates are obtained. When manufacturing “lightweight aggregate + high-aluminum system” castables, multi-level (guaranteed to be above level three) particle grading and pre-mixed finished products are used for construction. Solved the technical problems of water drift and low strength in the construction of lightweight materials.

“Lightweight aggregate + high aluminum series” castables belong to alkaline refractory materials, which are used for heavy-load insulation structures of large tunnel kilns, roller kilns, shuttle kilns, anti-seepage insulation of aluminum electrolytic cells, and load insulation of galvanizing furnace bottoms. It solves the defects of water enrichment and cavitation segregation of floating beads. During the construction process, vibrating equipment can be used to accelerate the construction progress. Under natural air drying conditions, the process from initial setting to reaching the strength of the zinc-carrying pot is shortened to less than one week. The construction and galvanizing furnace renovation period is shortened, ensuring the timeliness of the production line to obtain economic benefits.

Conditions of use

1100℃, lightweight. Construction methods: pouring, coating and spraying. Low-temperature castable for hot surfaces.

Product features

(1) Aggregates are pre-sintered with special refractory materials to produce third-grade particles for secondary grading and pre-mixed finished product construction. This solves the technical problems of light material construction water drift and low strength.

(2) The material belongs to alkaline refractory materials, which are used for heavy-load insulation structures of large tunnel kilns, roller kilns, shuttle kilns, anti-seepage insulation of aluminum electrolytic cells, and load insulation of galvanized furnace bottoms.

(3) A new generation of beadless, high-grade, heat-insulating, and pressure-resistant non-sintered low-temperature castable developed by a professional refractory materials research institute.

Erosion of Na2O and Reducing Atmosphere on 70 Refractory Castables in Aluminum Melting Furnace

April 12, 2025March 27, 2025 by rsrefractorycastable

Attack of aluminosilicate refractories by molten aluminum. For example, in aluminum melting furnaces and holding furnaces, this usually results in the formation of aluminum oxide deposits on the refractory. The degree of attack is increased in the presence of alkalis and in reducing atmospheres. This is related to the conversion of alumina bricks into sodium aluminate in a reducing atmosphere. The formation of sodium aluminate promotes the formation of aluminum nitride. In melting furnaces and holding furnaces, the alkali may come from the metal charge.

Erosion on 70 Refractory Castables in Aluminum Melting Furnace

In aluminum melting furnaces and holding furnaces, the contact of aluminosilicate refractories with liquid aluminum usually results in the formation of bonded interfacial deposits containing mainly aluminum oxide. Most of this aluminum oxide is the result of the reaction of aluminum with oxides in the refractory, especially with silicon dioxide. The reaction formula is as follows:

4AL+3SiO2→2AL2O3+3Si (1)

The kinetics of the reaction decreases rapidly after the deposit appears. It is concluded that this deposit becomes a barrier that prevents aluminum from penetrating into the refractory. The kinetics of this deposit are increased in a reducing atmosphere and in the presence of alkali. There are two sources of alkaline sodium oxides, in the aluminum ingots produced by the electrolytic cell or in the refractory. In the latter case, the active presence of Na2O cannot be determined. On the other hand, the relevant aspects of the reducing atmosphere have not yet been explained.

The main experiment this time was to determine the reaction of the aluminum silicate refractory to aluminum corrosion caused by alkali and reducing atmosphere, and to determine the reaction of high-aluminum castables (70% Al2O3) with aluminum fluoride (ALF3) as an infiltrant to such corrosion. The possible effects caused by the presence of alkali in the refractory, this product is a representative of amorphous refractory with non-wetting additives. It is used in industry as aluminum insulation furnace and aluminum smelting furnace lining.

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According to the operating temperature of the aluminum insulation furnace and aluminum smelting furnace, the test temperature is determined, and the temperature at the contact with the metal reaches 850℃, and the temperature at the flame radiation site reaches 1200℃~1500℃. The corrosion experiments on industrial high-alumina refractory castables with aluminum fluoride (ALF3) as a non-wetting agent have shown that the corrosion caused by aluminum and the role of basic oxides contained in the refractory material have been speculated.

It appears that, especially in the presence of a reducing atmosphere, beta alumina is the active phase in the refractory material in contact with liquid aluminum. From a thermodynamic point of view, the action of beta alumina on liquid aluminum leads to the formation of metallic sodium. The reaction equation is as follows:

6NaAL11O17+2AL→6Na+34AL2O3 (2)

When the oxygen partial pressure is higher than 10-19atm, the metallic sodium produced in the aluminum solution (aNa~0.1) will be oxidized. The reaction is as follows:

2Na+1/2O2→Na2O (3)

When the oxygen partial pressure is lower than 10-19atm, the presence of Na2O must be related to the action of refractory oxides (especially in silica) on metallic sodium. The reaction equation is as follows:

4Na+SiO2→2Na2O+Si (4)

On the other hand, in the presence of ALF3, metallic sodium may also be produced. The reaction formula is as follows:

6NaAL11O17+2ALF3→6NaF+34AL2O3 (5)

3NaF+AL→3Na+ALF3 (6)

Through analysis, when the liquid electrolyte with a temperature higher than 888℃ exists, reaction equations (5) and (6) can produce metallic sodium, which is conducive to the mutual exchange between the reactants. Under such conditions, a higher Na2O generation kinetics can be expected. Therefore, if the latter contains ALF3 as a wetting agent, aluminum will corrode the refractory material faster. The interface deposit mainly contains corundum (a-AL2O3) and also contains aluminum (AL) and aluminum nitride (ALN). It is believed that the aluminum nitride present in the deposit may participate in this corrosion process. This participation of aluminum nitride is consistent with the analysis of the reaction products obtained between aluminum and sodium carbonate in air and nitrogen. It was identified that at 900℃, the main reaction product obtained was sodium aluminate (NaALO2), which exists in the form of hydrate (NaALO2·3H2O). The specific gravity of sodium aluminate is 2.69g/cm³, while that of aluminum oxide is 3.96g/cm³. Therefore, the protective aluminum deposit should be accompanied by an increase in volume when it is converted into sodium aluminate. The increase in volume is conducive to the formation of cracks, which is conducive to the penetration of aluminum and thus the refractory is susceptible to corrosion.

Application of Cr2O3-Al2O3 Refractory Castables in Melting Furnaces

In principle, although melting furnaces can be lined with Cr2O3-Al2O3 bricks, they can also be lined with Cr2O3-Al2O3 refractory castables. However, for furnaces with complex structures, Cr2O3-Al2O3 refractory castables are often used for lining when considering cost and construction (convenience). Especially for thermal decomposition gasification melting furnaces, since the furnace walls are mostly boiler water pipes, it is very difficult to use refractory bricks for lining, but it is very convenient to use Cr2O3-Al2O3 refractory castables for lining.

When the melting furnace is lined with corundum refractory castables mixed with Cr2O3-Al2O3 powder and Al2O3 powder, it is believed that the Cr2O3-Al2O3 refractory castable with a high Cr2O3 content in the matrix material will also have high durability.

In order to confirm this, the corrosion resistance of refractory castables was compared and studied. The corrosion test was conducted in a rotary corrosion test furnace (1750℃). The results confirmed that the corrosion resistance of these refractory castables increased with the increase of Cr2O3 content in the matrix. The following conclusions can be drawn from the results of the slag resistance test:

(1) The fact that the concentration of Cr2O3 near the working surface of the Cr2O3-Al2O3 refractory castable decreased confirmed that Cr2O3 had transferred to the slag. The slag contained Cr2O3 and increased its viscosity, which prevented the slag from further penetrating and corroding the Al2O3-Gr2O3 refractory castable.
(2) At high temperatures, Cr2O3 reacted with Al2O3 to form a solid solution, which improved the high-temperature performance of the material while also improving the corrosion resistance of the material.
(3) Since the slag containing Cr2O3 has a high viscosity, it also improves the slag resistance of the Al2O3-Cr2O3 refractory castable.

Low Cement Castable Refractory Cement For Industrial Furnaces High Dense

March 6, 2025 by rsrefractorycastable

Low cement castables have the characteristics of high density, low porosity, high strength, low wear, thermal shock resistance and erosion resistance. Low cement castables not only have the characteristics of traditional refractory materials, but also adopt the most advanced ultrafine powder application technology to improve the medium temperature strength and high temperature volume stability of the castables. The organizational structure of the product forms a firm anchor-shaped multi-directional crystal structure at high temperature. The overall structural connection stability of the lining is ensured, and the service life is increased by 3 times compared with traditional castables.

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Application of Different Types of Low-Cement Castables

Low-cement and ultra-low-cement refractory castables have been widely used in industrial kilns in the fields of metallurgical industry, petrochemical equipment, machinery equipment manufacturing and decorative building materials at this stage, and have shown good use effects and economic benefits. Different types of low-cement castables play specific roles in various application fields as follows:

Clay and high-alumina low-cement castables can be used as lining materials for various heat treatment furnaces such as hot blast furnaces, heating furnaces, soaking furnaces, and rotary kilns.
Mullite low-cement castables are used for various high-temperature burner linings, x water-cooling pipe cladding and other applications.
Corundum and chromium-containing corundum low-cement castables are suitable for the refining equipment parts outside the molten steel furnace, the lining of the power frequency induction furnace, the high-temperature wear-resistant lining of the petrochemical catalytic cracking reactor, and other occasions.
Al2O3-SiC-C Low cement castables can be used for the lining of blast furnace tapping troughs, cupola tapping troughs, integral powder spraying guns for molten iron normalization treatment and other parts.
Low cement castables of refractory and Cr-containing refractory can be used as linings of the triangular area of the top of the iron-making electric arc furnace and the linings of the components of the external refining equipment of the molten steel furnace. For example, the overall spray gun lining for the spouting metallurgical industry, the RH and DH vacuum pump degassing device and the prepreg tube lining, the DC induction furnace lining, and the high temperature wear-resistant lining of the catalytic cracking tubular reactor of the petrochemical equipment.
Low cement castables of MgO-Al2O3 or Al2O3-MgO-Al2O3 are used as lining materials for equipment such as ladles and tapping troughs.

In summary, different types of low cement castables play an important role in various industries and have been widely used and promoted.

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Advantages and Characteristics of Rongsheng High-Strength Low-Cement Castables

Rongsheng Refractory Castables Manufacturer has rich experience in the production and sales of refractory materials. Rongsheng’s environmentally friendly fully automatic amorphous refractory production line provides a reliable guarantee for the timely delivery of Rongsheng’s high-quality refractory castable products. After years of practical experience, Rongsheng has discovered the application advantages and characteristics of high-strength low-cement castables, which can effectively extend the service life of high-temperature industrial furnace linings. If you need to buy high-strength low-cement refractory castables, please contact Rongsheng for free samples and quotes. Happy to share and make progress together. Next is the advantages and characteristics of Rongsheng’s high-strength low-cement castables.

Improve the refractoriness and high temperature strength of the refractory lining.

Due to the low CaO content in low cement castables, the formation of low eutectic phases in the material can be reduced. Thereby improving the refractoriness, high temperature strength and resistance to slag erosion, especially the cement-free castable has better performance.

The refractory lining has low porosity and high bulk density.

The amount of mixing water used in the construction of low cement castables is only 1/2 to 1/3 (about 4% to 6%) of ordinary low cement castables. Therefore, the porosity is low and the bulk density is high.

After the construction of the refractory lining is completed, less cement hydrate is generated.

After the low cement castable is formed and cured, less cement hydrate is generated, and even during heating and baking, there is no phenomenon of a large number of hydration bonds being destroyed and the medium temperature strength being reduced. The low cement castable will gradually sinter as the heat treatment temperature increases, and the strength will gradually increase.

It can improve the structural stability of the refractory lining.

Low cement castable combines the characteristics of traditional refractory materials, adopts ultrafine powder application technology, and significantly improves the medium-temperature strength and high-temperature volume stability of the castable, so that the product’s organizational structure forms a firm anchor-shaped multi-directional crystal structure at high temperatures. It ensures the overall structural connection stability of the lining, and its service life can be increased by 3 times compared to traditional castables.

Why doesn’t the Ladle Containing Molten Steel Melt?

March 3, 2025February 20, 2025 by rsrefractorycastable

In steelmaking, the container for molten steel is generally called a ladle, which is mainly used to store and transport molten steel. When tapping steel, 1650℃ molten steel is directly poured into the ladle. At this time, the steel is melted, so why is the container for molten steel (ladle) safe and sound?

First, we need to understand the main components of the ladle. From the outside to the inside, the ladle is composed of a metal shell, an insulation layer, a permanent layer, and a working layer.

The insulation layer is close to the steel plate of the ladle shell. Its function is to keep warm, prevent the ladle shell from deforming, and reduce the heat conduction of the ladle wall lining.

The function of the permanent layer is to prevent the molten steel from burning through the metal shell when the refractory material of the working layer in the innermost part of the ladle, which is in direct contact with the molten steel, is partially eroded or thinned.

The working layer is in direct contact with the high-temperature molten steel, and at the same time it is subjected to the mechanical scouring of the molten steel and slag, so the refractory material of the working layer is the most important thing in the ladle lining. The height of a ladle also depends on the selection of working layer materials and masonry technology.

After the temperature of the molten steel passes through the above layers, the temperature that is finally transmitted to the ladle shell wall is only about 300℃. The temperature of the working layer is 1600℃, the temperature of the permanent layer is 800℃, and the temperature of the insulation layer is 500℃. This is why the ladle shell will not be melted.

Simply put, the container (ladle) that holds molten steel will not melt, all thanks to the refractory lining inside. Therefore, the selection of durable, high temperature and wear-resistant refractory materials is the key factor to ensure the service life of the ladle. The refractory materials of the ladle lining working layer are generally magnesia-alumina-carbon bricks and carbon composite refractory materials. The thickness of magnesia-alumina-carbon bricks is about 110~120mm. It needs to withstand high temperature, molten steel and mechanical scouring.

The Use Temperature and Requirements of the Castables for the Ladles of Foundry

The selection of castables for the ladle of the foundry is crucial. It not only affects the service life of the ladle, but also affects the efficiency and safety of production. The selection of suitable castables needs to be determined according to the specific working conditions to ensure its refractory performance and construction convenience.

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Refractoriness of castables for ladle. The refractoriness of the AI2O3-SiC series of materials is between 1580-1770℃, which ensures the stability of the ladle in a high temperature environment.
Compressive strength. The compressive strength of the castable reaches 80MPA, which means that it can withstand the erosion of molten iron and extend its service life.
Use temperature. The use temperature of the castable for the ladle is generally not less than 1650℃ to meet the needs of high temperature operations.
Construction and maintenance. The construction of the castable should be convenient and easy to maintain to adapt to the daily maintenance work of small and medium-sized foundries.
Thermal shock stability. The castable needs to have good thermal shock resistance to cope with the thermal stress caused by temperature changes.
Performance requirements. The amount of water added to the castable should not exceed 7.3%, the number of thermal shocks should reach more than 35 times, the line change after firing should be between 0.3% and 0.8%, and the line change after re-firing should be between 0 and 0.2%.

Through these requirements, we can select the castable suitable for the foundry ladle to ensure that it is safe and efficient during use.

Steel Ladle Castables Rongsheng Manufacturer

Ladle castables are a special material used in the ladle, which can withstand high temperature and high pressure, and needs to have good fire resistance and chemical stability.

Performance Characteristics of Rongsheng Steel Ladle Castables

Good fire resistance. Ladle castables need to withstand high temperature and high pressure, so they need to have good fire resistance. Its refractoriness can reach above 1650℃, and it can work stably at high temperature.
Good chemical stability. Ladle castables need to resist various chemicals in molten steel, so they need to have good chemical stability. It can work stably in molten steel and will not react with substances in molten steel.
Good thermal insulation. Ladle castables need to keep the temperature of molten steel stable, so they need to have good thermal insulation. It can transfer heat in molten steel and keep the temperature of molten steel stable.
Good compactness. Ladle castables need to fill the internal space of the ladle, so they need to have good compactness. It needs to fill the inner space of the ladle tightly to achieve the best insulation effect.
Good unloading. Ladle castables need to be easily unloaded, so they need to have good unloading properties. It needs to be easily washed and peeled off by molten steel to facilitate the discharge of molten steel.

Rongsheng Refractory Castables Factory‘s ladle castables have good fire resistance, good chemical stability, good thermal insulation, good compactness and good unloading properties. These properties can make the ladle castable work stably in the ladle and provide guarantee for the efficient smelting of molten steel. To purchase ladle and iron ladle castables, please contact Rongsheng for free samples and quotations.

What is the Suitable Thickness of Refractory Castables Linings?

January 19, 2025 by rsrefractorycastable

Rongsheng Refractory Castables is a refractory material manufacturer with rich production and sales experience. Rongsheng, based on years of production and sales experience, can customize refractory lining solutions for high-temperature industrial furnace linings. The determination of the thickness of high-temperature refractory castables mainly depends on the working environment temperature, material properties and usage requirements. Contact Rongsheng for detailed information. ‌

‌Working environment temperature‌: The working environment temperature is the most important factor in determining the thickness of refractory castables. The higher the temperature, the greater the castable thickness required to withstand the thermal stress at high temperatures.

Monolithic Refractory Castables for CFB Boilers Refractory Linings — Monolithic Refractory Castables for Refractory Linings

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‌Material properties‌: Refractory castables of different materials have different refractory properties and thermal expansion coefficients, and the differences in these properties will directly affect the choice of thickness. For example, the thickness design ranges of light and heavy materials are 10-200mm and 200-300mm respectively.

‌Usage requirements‌: Usage requirements are also an important factor in determining thickness. Some projects may require that the castables not only withstand high temperatures but also have corrosion resistance, which requires a more sophisticated design.

Recommendations on the thickness of refractory castables in different application scenarios

‌Ladle‌: The thickness of the working lining is usually 100-150mm, and the thickness of the coating layer is 10-15mm.

‌General furnace type‌: The thickness is generally 200-230mm, and there are also designs of 150-200mm thick according to the location conditions.

‌Special requirements‌: If the furnace weight needs to be reduced, it can be designed to be 80-100mm thick, but the service life will be shortened accordingly.

As the amount of refractory castables continues to increase, the scope of use is also getting larger and larger. However, the thickness of different refractory castables and the thickness of spray coatings and coatings are different.

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The thickness of heavy refractory castables or refractory concrete cannot be less than 100mm. If it is less than 100mm, the service life of heavy castables will be affected. The most suitable thickness is 200mm. When there are certain restrictions on the use of some parts, it is also possible to pour at a thickness of not less than 100mm, and of course 150mm is also possible. If conditions permit, it is best to pour 200mm.

Of course, some user manufacturers require that refractory castables be poured at 220mm? Of course. Generally, 200mm is suitable. If 220-250mm is OK, the service life will be longer. If the user requires the refractory castable to be poured at a thickness of 50mm, be sure to tell the user that 50mm castables are not possible. Not only does it affect the service life, but also because the particles of the refractory castables are large and the thickness is too thin, it will not work at all.

The pouring thickness of lightweight refractory castables cannot be less than 80mm. If there is no specific restriction on the location of use, pouring 100-150mm is most appropriate.

There are also some user manufacturers who cannot distinguish whether to use refractory castables for pouring, coating or spraying. They should first ask the required thickness of pouring or spraying, and give users suggestions on using castables or spray coatings and coatings. The thickness of spray coatings and coatings is 30-50mm, usually 50mm is the most suitable. Too thick spray coatings or coatings will cause delamination, and too thin will affect the service life.

Therefore, as long as the user requires 30-50mm thickness, spray coatings or coatings must be used.

There are also refractory plastics, and the thickness is the same as spray coatings and coatings, 50mm is the most suitable. If 80mm is used for a specific temperature and environment, it can also be used, but the thickness cannot exceed 80mm. Too thick will also cause delamination and affect the service life.

Suggestions for the construction and maintenance of refractory castables

‌ During construction, adjustments need to be made according to the specific parts and conditions to ensure the versatility of the construction parts.
‌ In actual construction, the thickness selection needs to be adjusted and optimized according to the specific situation to ensure the quality and safety of the project. ‌

Castable Refractory Material for Heating Mantle Lining of Annealing Furnace

March 3, 2025December 21, 2024 by rsrefractorycastable

The heating hood of the bell-type annealing furnace is in a long-term working environment of alternating high and low temperatures, and is in a rising or falling working state, with poor working conditions. This causes cracks and falling off of the original furnace lining castable, resulting in large heat dissipation losses of the heating hood, serious energy consumption, and excessively high temperatures of the outer wall and burner area. Rongsheng refractory castable manufacturer can provide high-quality heating hood lining castables for annealing furnaces. Contact Rongsheng for free samples and quotes.

Refractory Materials for Heating Hood Lining

The working temperature of the heating hood used for annealing heating is about 850 ℃, and the requirements for the refractory materials of the furnace lining are relatively high. The furnace lining must have good refractory and heat insulation effects. Even if the temperature of the hot surface of the furnace lining reaches 850℃～900℃, the average temperature of the outer wall of the heating hood remains ≤ room temperature + 45℃, and the average temperature of the shell of the burner area remains ≤ room temperature + 55℃. However, due to the cracks and cracking and shedding of the original lining castable of the heating hood, the average temperature of the outer wall and the shell of the burner area is statistically: the outer wall> 75℃ (room temperature 20℃), the shell of the burner area> 85℃ (room temperature 20℃), which has exceeded the design temperature index. Therefore, the refractory materials of the heating hood lining of the annealing furnace are modified to effectively reduce heat loss, reduce the temperature of the outer wall of the furnace and the shell of the burner area, and reduce energy waste.

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Problems with Refractory Materials for Heating Hood Lining

The heating hood is welded from large structural steel and a solid electroplated cylinder. The refractory materials for heating hood lining are currently mainly castable structures, which have the following disadvantages:

(1) The lining is a castable structure, the temperature of the outer wall of the furnace top is too high, the heat dissipation loss is large, the energy consumption is serious, and the working environment is harsh.

(2) The lining material is a heavy and light castable structure, and the thermal shock resistance and mechanical vibration performance of the lining material are poor. Cracks are easily generated during use, resulting in serious cracking and peeling of the castable lining, shortening the service life, and making maintenance difficult and expensive.

(3) The castable structure of the lining needs to be baked before use. If the baking effect is not good, it will affect the performance of the lining.

Renovation Plan for Refractory Castable Materials of Heating Hood Lining

Choice of refractory materials At present, refractory ceramic fiber materials are widely used as refractory materials for furnace lining in domestic bell furnace applications. Refractory ceramic fiber materials are a lightweight and efficient thermal insulation material. Compared with traditional insulation materials, they have the following advantages:

(1) Low volume density: Fiber furnace lining is more than 75% lighter than lightweight insulation brick furnace lining and 90%~95% lighter than lightweight castable furnace lining.

(2) Low thermal conductivity: When the average temperature of refractory fiber furnace lining is 400℃, the thermal conductivity coefficient is <0.11 W/m·K. When the average temperature is 600℃, it is <0.16 W/m·K. When the average temperature is 1000℃, it is <0.22 W/m·K, which is about 1/8 of lightweight clay bricks and 1/10 of lightweight heat-resistant lining (castable), with significant insulation effect.

(3) High thermal sensitivity: The thermal sensitivity of refractory fiber lining is much better than that of conventional refractory lining. At present, heating furnaces are generally controlled by microcomputers. The high thermal sensitivity of fiber lining is more suitable for the automatic control of industrial kilns.

(4) No need to bake the furnace: The lining can be put into use after the construction is completed, and no baking procedure is required.

(5) Simple construction: No expansion joints are required during the construction process, and the influence of construction technical factors on the insulation effect of the lining is small.

(6) The disadvantages of refractory ceramic fiber lining are that it is not wear-resistant, has poor thermal shock stability, and is not resistant to hot air erosion. This requires special attention. After long-term use, it will be found that ceramic fiber cotton will produce slag and agglomeration. Sometimes, improper operation will cause pieces to fall off with a slight collision. This may also be due to the fact that the material itself is an insulation product.

Refractory fiber lining has become a trend in the development of furnace linings, representing the level of modernization of industrial furnaces. Whether refractory fiber lining is adopted or not directly determines the use effect, product quality and output of the furnace. Therefore, the selection of refractory ceramic fiber materials to replace the original furnace lining materials must meet the use requirements of the heating hood of the full hydrogen hood annealing furnace in the cold rolling mill.

Use of Amorphous Refractory Materials in Blast Furnaces — Castable Refractory Lining for Furnaces

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How High a Temperature Can a Refractory Castable Withstand?

The temperature resistance of a refractory castable depends on the material composition and preparation process. Generally, it can withstand high temperatures, and different types and formulations of refractory castables have different temperature resistance ranges. Special refractory castables can withstand temperatures up to 2000°C, and attention should be paid to the temperature change rate and temperature gradient when using them. The temperature resistance of a refractory castable depends on its material composition and preparation process. Generally speaking, refractory castables can withstand high temperatures, but the specific temperature resistance range varies depending on the type and formulation of refractory castables.

Some common refractory castables, such as high-alumina refractory castables, corundum refractory castables, and low-cement refractory castables, have higher temperature resistance. These materials can generally withstand high-temperature environments of 1500°C to 1800°C.

However, for higher temperature applications, such as in steelmaking, glassmaking, or other high-temperature processes, refractory castables with special formulations and preparation processes may be required. These special refractory castables can withstand higher temperatures, reaching or even exceeding 2000°C.

It should be noted that even if the refractory castable can withstand high temperatures, it is also necessary to pay attention to the rate of temperature change and the temperature gradient to avoid cracking or thermal shock of the refractory castable due to rapid changes. Therefore, in practical applications, it is necessary to select appropriate refractory castables according to specific circumstances and follow relevant instructions and operating specifications.

Moisturizing and High-Temperature Properties of Refractory Plastics

January 18, 2025November 19, 2024 by rsrefractorycastable

Plastic is a refractory material that was developed and applied earlier and is mainly used in heating furnaces, electric furnace tops, and other parts. Due to its shortcomings such as short storage time and poor fire resistance, its application range is limited. However, this refractory material has some irreplaceable advantages, such as the high-temperature strength of the furnace body constructed with plastic, excellent thermal shock resistance, low thermal conductivity, and flexible construction methods.

Selection of Refractory Plastic Aggregates

Refractory plastics should have excellent plasticity, moisture retention, and high-temperature performance. To meet these conditions, it is very important to select suitable raw materials. The raw materials should have good volume stability. During the heating process, they can be well-sintered and reacted with binders such as clay. Aggregates should have appropriate particle size and grading. Generally, the critical particle size of refractory plastic aggregates is less than 10 mm, the aggregate content is 55% to 65%, and the powder content is 35% to 45%. Through strength tests and moisture retention tests, it was found that although the plastic produced with grade 3 high aluminum and grade 2 high aluminum as the main raw materials has a higher strength after burning, the moisture retention of the material is poor. Therefore, it is determined to use special grade high aluminum alumina as the main raw material, and it is required to be sintered densely and have a low impurity content. In order to improve the moisture retention performance, the iron oxide content in the material should be strictly controlled.

Phosphate Bonded High Alumina Refractory Plastics — High Alumina Refractory Plastics

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Effect of Clay and Powder Addition on the Performance of Refractory Plastic

Binding clay is added to plastic, which mainly plays a bonding role and improves its plasticity and sintering performance. The particle size of clay should generally be less than 200 mesh. Its dosage should be minimized while ensuring the plasticity and bonding ability of plastic. If too much is added, the linear shrinkage of plastic will increase after high-temperature firing, the load softening temperature will decrease, and the high-temperature creep will increase. If the amount added is too little, the plasticity of the material cannot be guaranteed. Through experiments, it is determined that the amount of clay added is 5% to 15%. In order to reduce the linear change of plastic after firing, an appropriate amount of kyanite is added. Since kyanite produces volume expansion at high temperatures, it can offset part of the shrinkage of plastic. Its fineness is 150 mesh, and the amount added is controlled at about 5%. In order to improve the plasticity and thermal shock resistance of plastic and further reduce the impurity content in the raw materials, alumina powder, and silicon powder are added. This can not only improve the construction performance of the material but also increase the medium and high-temperature strength of the product. The total amount of the two is generally controlled at 6% to 12%, which is more reasonable.

Through experiments, it is found that when the plastic index is around 14%, the plastic is relatively hard and the construction performance is poor. When the plastic index is around 26%, the plastic feels softer and the construction is easier. In order to facilitate construction and meet the requirements of other performance indicators. Through repeated experiments, it is confirmed that the plastic index of the plastic is about 28%.

Selection of Fire-Resistant Plastic Binder

In order to make plastic have higher strength and excellent moisture retention performance, various binders were tested, such as phosphoric acid, water glass and aluminum sulfate. Through experiments, it can be proved that plastic with phosphoric acid as binder has higher strength index. However, due to the strong acidity of phosphoric acid and the high iron oxide content in the raw material, phosphoric acid can easily react chemically with iron oxide, which makes the moisture retention performance of plastic worse. Using aluminum sulfate as a binder, plastic has a longer moisture retention performance, but the strength index of plastic cannot meet the use requirements. Using water glass as a binder, the moisture retention performance of the material is better in the short term, but after a long storage time, the construction performance of plastic deteriorates. In addition, when the plastic combined with water glass is baked, the hard shell produced on the surface will have an adverse effect on the strength of the plastic construction body. Through repeated experiments, it was determined that the two binders of phosphoric acid and aluminum sulfate were used in combination, so that the moisture retention performance and strength index of the plastic can meet the use requirements.

High-Strength Aluminum Phosphate Bonded Refractory Plastics

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Factors Affecting Moisture Retention Performance

Influence of aggregate types

Through continuous moisture retention experiments, it was found that the moisture retention performance of plastics with high-aluminum from special downdraft kilns as aggregates is significantly better than that of plastics with other low-grade aggregates. This is due to the dense sintering of special-grade aggregates and the low water absorption rate of particles.

Influence of binder types

Binders have the greatest impact on the moisture retention performance of plastics and also play a key role in other properties. If improperly selected, plastics will not meet the requirements of use.

Through experimental research on the moisture retention performance and compressive strength performance of the test blocks, as well as comprehensive considerations such as raw material costs, phosphoric acid, and aluminum sulfate were finally selected as composite binders. This can not only meet the moisture retention performance requirements of plastics but also meet the requirements of medium and high-temperature strength.

Effect of admixture types

Experiments show that adding organic acids (such as oxalic acid) and dextrin and other admixtures can prevent or delay the reaction between the binder and the refractory material, and play a role in extending the moisture retention of plastic. Some admixtures are oily and can effectively reduce the agglomeration of plastic, which mainly extends the moisture retention of the material from a physical aspect. Oily moisturizers and main binders such as phosphoric acid are not miscible but can reduce the chance of chemical reactions between phosphoric acid and raw materials, making the moisturizing effect better.

When used in furnaces such as heating furnaces and annealing furnaces, plastic has certain advantages over castables. It does not require on-site mixing equipment and can be directly constructed. It has a large viscosity and does not flow. It is easier to combine with the old lining during repair, and local repairs can be performed without templates. Because it has a low water content, the requirements for baking conditions are not very strict.

Conclusion

(1) Using high-grade downdraft kiln high-alumina bauxite as the main raw material can significantly improve the moisture retention performance of plastics.
(2) Using phosphoric acid and sulfuric acid in a composite form, and adding an appropriate amount of additives, plastics with relatively good moisture retention and strength indicators can be produced. The effect of using a single combination is not ideal.
(3) Select high-grade high-alumina bauxite with dense sintering and low impurity content to minimize the iron oxide content in the material. In addition, adding an appropriate amount of moisturizing agent can significantly extend the moisture retention period of plastics.

Rongsheng amorphous refractory castable manufacturer can provide high-quality amorphous refractory lining materials for high-temperature industrial furnaces. If you need to purchase refractory plastics to extend the service life of refractory furnace lining materials. Please contact Rongsheng for free solutions for high-temperature industrial furnace linings.

Refractory Castable Materials for Boiler Furnaces

December 16, 2024October 29, 2024 by rsrefractorycastable

The boiler furnace is a three-dimensional space surrounded by furnace walls for fuel combustion. Its function is to ensure that the fuel is burned as much as possible and to cool the flue gas temperature at the furnace outlet to a temperature that allows the convection heating surface to work safely. Rongsheng Refractory Material Manufacturer can provide high-quality boiler furnace refractory materials – refractory lining maintenance services for high-temperature industrial furnaces. Contact Rongsheng for detailed information.

High-Alumina Refractory Castables Manufacturer

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Refractory Castables for Furnace Lining

Common refractory castables for furnace lining include steel fiber, special high aluminum, brown corundum, silicon carbide, mullite, etc. Aggregates and powders made of high-temperature resistant or high-temperature wear-resistant products, with binders, ultrafine powders, and other products added, are mixed and made. They can be cast or made into high-temperature-resistant prefabricated parts and hoisted for construction.

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High-Temperature Resistant Plastic Refractory for Furnace Lining

High temperature resistant plastic for furnace High temperature resistant plastic for furnace is basically the same as castable material, but the combination and construction methods are different. It is composed of 80% to 85% high-strength aggregate and fine powder. After adding binder and plasticizer, a small amount of blending agent is added. After sufficient mixing, it is a kind of hard mud paste, which can be made of various high temperature resistant raw materials. It belongs to a more plastic and shape-changing refractory material.

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Ramming Material Refractory for Furnace Lining

Compared with other amorphous refractory materials of the same material, ramming material for furnaces is dry or semi-dry and loose. The dense structure is obtained by strong ramming, and the combination will have density only when it is heated to the sintering temperature. Compared with castables and plastics, it has more reliability and corrosion resistance at high temperatures. However, its service life depends to a large extent on the pre-burning before selection or the sintering amount during the first use. If the heating surface is sintered as a whole without cracks and does not separate from the bottom layer, the service life can be improved.

The refractory materials for furnaces should not only look at the product quality, but also the furnace drying is an important link. The furnace should not only be baked, but also the necessary furnace boiling should be implemented. The heating boiler in winter should also be baked before it is put into operation to drive away the moisture in the furnace body and chimney flue. Boil the furnace means to put scientifically proportioned chemicals into the furnace to dissolve and remove the oil, dirt, rust, etc. attached to the inner wall of the heating surface during the manufacturing or transportation of the boiler, so as to ensure the safe operation of the boiler and the quality of steam and hot water.

Causes of Damage to Refractory Castables for Furnaces and Methods of Repairing Castables

Speaking of the current structure of boilers, it is estimated that a large part of the structure is selected refractory castables. Refractory castables not only have high performance and good performance. In many cases, refractory castables can be modified to produce different properties of refractory materials, which is one of the reasons why refractory castables are very popular now.

However, one of the puzzling problems is that refractory castables are used for a long time, or a considerable part of the products are extremely vulnerable to damage during the curing process. When building boilers, the use of aluminate cement refractory castables is mainly caused by the combination of aluminate cement and castables.

Surface crushing caused by alkaline impurities

In the material, the presence of soluble alkali increases solubility and accelerates the reaction as an important prerequisite. In cement castables, the increase in cement content and the increase in system alkalinity will lead to larger hydrated minerals, which is conducive to the reaction. Curing environment temperature and humidity are important factors for damage. Generally, the greater the humidity, the easier it is to wet the pores in the casting body. Under humid conditions, dissociation is easier and the reaction is smoother. The density of the green body is also an important factor. When the porosity of the green body is high, water in the air is more likely to diffuse into the green body, so that the damage reaction continuously enters the depth of the green body, resulting in casting. The crushing of the table and the inside will damage the material. In addition, the shape and thickness of the blank also affect the progress of the reaction. In addition, the quantity and quality of construction water will also affect the damage.

Surface pulverization caused by carbonation reaction

Surface pulverization caused by carbonation reaction can be divided into two types. One is direct carbonation, where carbon dioxide directly reacts with the hydration products of cement to form a calcium carbonate-calcium aluminate complex. It closes the surface pores and causes surface hardening, thereby inhibiting pulverization. The other is carried out by the catalysis of sodium ions in the presence of soluble alkali metal oxides. This is similar to the mechanism of sodium ion damage, which may lead to the destruction of the castable lining.

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Repair of Furnace Lining Refractory Castables

The damage and repair methods of furnace lining refractory castables are mainly used to solve surface damage.

Wash high-purity raw materials to reduce the content of soluble alkali metals. When preparing refractory castables, choose high-quality refractory aggregates as much as possible, and choose washed and baked raw materials with low alkali content (such as bauxite and corundum). If the raw materials are not calcined (such as andalusite), choose more cautiously and try to use composite sodium and low concentration mixtures. The dispersion effect and filling effect of micropowder are conducive to improving the density of castables. However, when selecting micropowder, the impurity content of micropowder should be properly controlled to minimize the amount of cement containing high alkali metal impurities.
Strengthen the control of construction water quality.
Reduce the contact between the surface of the castable and the air. Surface coatings, coverings, etc. can be used to close the surface pores and minimize the diffusion of CO2 and water vapor into the castable to prevent damage reactions.
Accelerate hardening, dry the green body as soon as possible, promote the development of green strength, and make the damage reaction lose conditions.

After a period of operation, the damage to the original furnace lining has been restored, and the damage to the furnace lining material has not been aggravated. Therefore, when using castables, we should take correct measures in time to make good transformation of the boiler. Rongsheng amorphous refractory castable manufacturer is a powerful manufacturer and seller of refractory materials. To purchase refractory castable products for furnace lining, please contact Rongsheng for free samples and quotations.

Long-Life Thermal Insulation Refractory Castable for Ladle Furnace Lining

November 11, 2024October 15, 2024 by rsrefractorycastable

Ladle is an essential container in the steelmaking process. With the continuous development of smelting technology, especially the processing of out-of-furnace refining LF and RH, its role has evolved from the simplest receiving molten steel to a furnace that undertakes certain smelting functions. If the molten steel stays in the ladle for a long time, it will inevitably cause the temperature of the molten steel to dissipate, and the ladle lining with high thermal conductivity will cause the heat dissipation loss of the molten steel to increase. The deformation of the ladle shell becomes more serious, and the temperature drop rate of the molten steel increases, causing serious slag hanging nodulation, and cold steel on the ladle wall. Excessive low temperatures may even force the middle package to cut off the flow and final pouring. It not only affects the quality of the cast slab but also reduces the yield of molten steel and increases the production cost. Therefore, thermal insulation ladles are increasingly becoming a need for steel mills. The structural model of thermal insulation ladle refractory materials is usually lightweight insulation panels or nano panels + permanent layer castables + working layer refractory materials. Rongsheng’s long-life thermal insulation refractory castable for ladle furnace lining. Contact Rongsheng to get a free quote.

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Insulating Refractory Castables for Ladles

The insulation board itself, which plays the most important role in thermal insulation, needs a layer of refractory material to protect it. The material must first protect the insulation material from too much pressure, and secondly, protect the insulation material from exceeding the operating temperature (if it must be below 1000°C), then the ladle Permanent layer castables are such important materials. The ideal permanent layer refractory material for thermal insulation ladles should have good thermal stability, thermal insulation, corrosion resistance, safe and reliable application, complete structure, and long service life. In order to maintain the good thermal insulation performance of the ladle and reduce the temperature drop of the molten steel, the performance evaluation of the new CA6 castable and the lightweight mullite castable was conducted in this work and applied to the ladle, achieving a relatively good comprehensive thermal insulation effect.

Performance comparison of thermal insulation refractory castables for ladles

At present, the permanent layer materials of ladles are mostly ordinary high-aluminum castables, and the main raw material is bauxite. There are the following shortcomings in the use of this refractory castable. First, the thermal conductivity is high, which causes energy loss during use. Second, the refractoriness is low. If the working layer is used abnormally and the molten steel directly contacts the permanent layer, the probability of steel leakage will be greater and the safety factor is low. Third, the volume density is larger and the empty ladle weighs more. Therefore, the special requirements for ladle insulation are not met, and it is necessary to develop new permanent layer castables with excellent comprehensive properties. Performance comparison of new CA6 castable and lightweight mullite castable.

Among them, the CA6 raw material (CaAl12O19, abbreviated as CA6) is the calcium aluminate phase with the highest Al₂O₃ content in the CaO-Al₂O₃ system. Its melting point is 1875℃, its thermal expansion coefficient is 8.0×10-6℃⁻¹, its particle volume density is 2.70g·cm⁻³, and its apparent porosity is 26.8%. The fire resistance of this material is similar to that of plate corundum, but its thermal conductivity is only 1/3 of corundum. It is a new type of high-quality thermal insulation material that has emerged in recent years. CA6 castable is made of CA6 as aggregate, and the matrix part is made of plate-shaped corundum fine powder, alumina powder, and calcium aluminate cement as binding agents. The volume density of spherical lightweight mullite particles is 1.59g·cm⁻³, and the apparent porosity is 38.9%. The lightweight mullite castable is made of microporous M70 spherical lightweight mullite balls as aggregate, and the matrix part is made of plate-like corundum fine powder, alumina powder, and calcium aluminate cement as binding agents to ensure Better resistance to slag erosion to improve the safety of the permanent layer.

The volume density of lightweight mullite castable is 2.17g·cm ⁻³, and its unit weight is 24% lower than the currently used high-aluminum castable. At the same time, the thermal conductivity is reduced by 16%, which can achieve the purpose of lightweight and low thermal conductivity of the ladle. CA6 castable is also 5.6% lighter than ordinary high-aluminum castable, and its thermal conductivity is reduced by 26%.

Pour the original ladle permanent layer castable B, the new CA6 castable C, and the lightweight mullite castable 3# into crucibles respectively. Add the final converter slag and conduct a slag corrosion resistance test on the crucible under the condition of 1500°C for 3 hours. Observe the resistance to melting loss and penetration of different materials. After completing the test, the crucible was cut open. The erosion status is as follows:

CA6 castable has the best resistance to erosion and penetration, with a large amount of slag remaining in the crucible hole; light mullite castable has the second-best resistance to erosion and penetration. The boundary between ordinary high-aluminum permanent layer casting slag and refractory material is not clear, and the crucible refractory material and slag are melted together. The resistance to penetration is slightly better than the resistance to erosion, indicating that more liquid phases have appeared in the high-aluminum castable at 1500°C. Therefore, the material needs to be improved to improve its high-temperature resistance, which is very important for the safety of the ladle. The micropores of spherical lightweight mullite are beneficial to improve corrosion resistance and permeability, so this lightweight material can also perform better in insulation and corrosion resistance.

Application Comparison

The above three kinds of castables are used for construction and application on 300t steel ladle. The target requirement of the lightweight mullite castable and CA6 castable for the permanent layer of the thermal insulation ladle is to have both good resistance to molten steel erosion and good thermal insulation properties. At the same time, the furnace has good structural integrity and a stable thermal insulation effect during the furnace service process. After three furnace campaigns, the surface conditions of the permanent layer of the steel ladle were different, and cracks of varying degrees appeared in the permanent layer of the steel ladle in the later stages of the furnace campaign. This is related to the thermal shock resistance, strength and damage of the material during the unpacking process. The comprehensive technology of how to reduce the cracking of the permanent layer material of the thermal insulation ladle still needs further in-depth research.

Judging from the average temperatures of each slag line in each furnace, the steel shells of the uninsulated ladle slag lines are all above 320°C, while the average temperatures of the four test slag lines using insulation are below 280°C. Generally, the temperature of the slag line steel shells has dropped. 50～100℃. The temperature drop of the steel shell in the wall part is between 20 and 50°C, which varies slightly depending on the configuration of the insulation material and permanent layer material. The insulation material of the thermal insulation test package remained in good condition during the furnace service period, and the average temperatures of the slag line and wall steel shell were lower than those of ordinary steel ladles, indicating that the permanent layer played a good protective role. In order to ensure safety, the current situation of obvious cracks in the new permanent layer material after two furnace operations still needs to be optimized and improved to ensure that it can be applied to four furnace operations.

In Conclusion

Insulated ladles have become an important technical measure for steel companies to save energy, protect the environment, and improve the quality of steel products. The permanent layer materials of ladles have been given higher requirements. The physical properties such as strength and strength of the developed CA6 castable and lightweight mullite castable meet the application requirements of the permanent layer of the ladle. At the same time, they have better thermal insulation and corrosion resistance than conventional high-aluminum castables and can protect thermal insulation materials. The function ensures that the ladle maintains good heat preservation during the furnace service period. Further in-depth research is needed on the comprehensive technology to reduce the cracking of the permanent layer material of the thermal insulation ladle.

Rongsheng Refractory Castable Manufacturer

Rongsheng refractory castable manufacturer, an environmentally friendly and advanced fully automatic unshaped refractory material production line, provides a reliable guarantee for refractory castable lining materials for high-temperature industrial furnaces. Annual output is 6W tons. Rongsheng Manufacturer can provide high-quality insulation and refractory castable products for ladles, rotary kilns, and non-ferrous smelting furnaces, as well as the design and construction of insulation layer refractory lining materials. The ladle is made of long-life insulation castables and is shipped directly from the manufacturer at a low price. Contact Rongsheng for free details.

Monolithic Refractory Castables Lining Structure

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Advantages of lightweight heat-insulating, pressure-resistant, non-sintered low-temperature castable insulation layer compared to traditional insulation layer

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Correct application of castables

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Erosion on 70 Refractory Castables in Aluminum Melting Furnace

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Application of Cr2O3-Al2O3 Refractory Castables in Melting Furnaces

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Application of Different Types of Low-Cement Castables

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Advantages and Characteristics of Rongsheng High-Strength Low-Cement Castables

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The Use Temperature and Requirements of the Castables for the Ladles of Foundry

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Steel Ladle Castables Rongsheng Manufacturer

Performance Characteristics of Rongsheng Steel Ladle Castables

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Recommendations on the thickness of refractory castables in different application scenarios

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Suggestions for the construction and maintenance of refractory castables

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Refractory Materials for Heating Hood Lining

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Problems with Refractory Materials for Heating Hood Lining

Renovation Plan for Refractory Castable Materials of Heating Hood Lining

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How High a Temperature Can a Refractory Castable Withstand?

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Selection of Refractory Plastic Aggregates

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Effect of Clay and Powder Addition on the Performance of Refractory Plastic

Selection of Fire-Resistant Plastic Binder

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Factors Affecting Moisture Retention Performance

Influence of aggregate types

Influence of binder types

Effect of admixture types

Conclusion

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Refractory Castables for Furnace Lining

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High-Temperature Resistant Plastic Refractory for Furnace Lining

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Ramming Material Refractory for Furnace Lining

Causes of Damage to Refractory Castables for Furnaces and Methods of Repairing Castables

Surface crushing caused by alkaline impurities

Surface pulverization caused by carbonation reaction

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Repair of Furnace Lining Refractory Castables

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Insulating Refractory Castables for Ladles

Performance comparison of thermal insulation refractory castables for ladles

Application Comparison

In Conclusion

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