Refractory Blog Archives - Rongsheng Refractory Castable Manufacturer

Castables Refractory for Regenerative Heating Furnaces

September 3, 2024August 20, 2024 by rsrefractorycastable

Regenerative continuous heating furnaces enable steel companies to efficiently utilize low calorific value fuels. However, compared with ordinary steel rolling heating furnaces, the combustion method, heat exchange method, heat exchange medium and other aspects of the regenerative heating furnace have undergone major changes. The furnace structure has also changed as a result, resulting in a series of problems such as more channels in the furnace wall of the regenerative heating furnace, complex structure, and difficulties in construction and baking. As a result, the airtightness and comprehensive integrity of the working lining are poor, and the refractory materials in the furnace lining and burner area are prone to cracking and damage during use.

Industrial Kiln Insulation Refractory Castables Construction

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In addition, the high-temperature flue gas and high-temperature preheated combustion medium of the regenerative heating furnace are circulated from the burner body and the working conditions are frequent switching between pairs of burners. It is easy to cause thermal shock cracks, thermal stress fatigue damage and burner nozzle deformation in the refractory materials in the furnace lining and burner area. In response to the above situation, refractory castable manufacturers have taken the following measures:

Improvement Measures for Castables Refractory for Regenerative Heating Furnaces

(1) Select high-quality high-alumina bauxite clinker with an impurity content not exceeding 2% as large aggregate. In order to prevent the raw materials from containing more impurities and producing low melting point substances during the high temperature process, the load softening temperature of the castables will be reduced. It affects the high-temperature performance of the castables, causing the burner to deform during operation and reducing its working performance.

(2) Select sintered mullite as fine aggregate and powder. The advantages of mullite include good structural structure, low creep rate, small thermal expansion, good thermal shock resistance and strong resistance to chemical erosion. Improve the linear change rate, thermal shock stability, erosion resistance and high temperature creep resistance of the castable, and increase the high temperature compressive strength of the castable.

(3) Select andalusite and kyanite as expansion materials, and use the volume expansion effect of andalusite and kyanite during the mulliteization process at high temperatures to improve the linear changes of the castable after high-temperature burning and improve the thermal shock stability of the castable. sex.

(4) Select dense corundum fine powder, α-Al2O3 micro powder, and silica micro powder as micro powder materials. While improving the density of the castable, the high melting point of α-Al2O3 is used to improve the refractoriness of the burner castable. Mullite and secondary mullite are generated by sintering powder and aggregate under high temperature conditions. While improving the line change rate of the castable, it also improves the comprehensive mechanical strength and high temperature performance of the castable.

In addition, the researchers added a small amount of Al-80 cement as a binding agent to improve the medium and low-temperature bonding strength of the castable by taking advantage of its rapid hardening, high strength, and fire resistance. Polycrystalline alumina fiber is added as reinforcing and toughening material, and explosion-proof fiber is added as explosion-proof agent to further improve the bonding strength and thermal shock stability of the castable. Sodium hexametaphosphate and FS20 are used as high-efficiency composite dispersants (water reducing agents) to improve the construction performance of castables.

High-Alumina Refractory Castables Manufacturer

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Excellent Physical and Chemical Properties of Castables for Regenerative Heating Furnaces

Compared with ordinary high-aluminum castables, the improved castables have better comprehensive indicators. The change of its line after burning shows that it has micro-expansion, which can effectively prevent shrinkage cracks in the furnace lining and burner nozzle. The number of water cooling times at 1100°C reaches 25 times, which indicates that the thermal shock stability of the castable is good and can reduce thermal shock cracking of the refractory material in the burner part. The starting temperature of high-temperature load softening is greater than 1400°C, which is higher than the maximum operating temperature of the heating furnace. It can avoid the problems of furnace lining bulging and burner nozzle deformation, and delay the deterioration of burner performance.

In summary, the improved integral castable of the regenerative heating furnace lining and burner has a reasonable microstructure. It has the advantages of good medium and high-temperature sintering bonding, high mechanical strength, excellent linear change rate and thermal shock stability, and high load softening starting temperature. Moreover, the improved castable has good construction performance and its service life is more than doubled to more than 12 months under maintenance-free conditions. It effectively reduces the workload of furnace lining and burner maintenance, and reduces the consumption and maintenance costs of heating furnace castables, and repair materials.

Improvement of Furnace Body Refractory Castable Structure of Chamber Heating Furnace

Forging heating furnace is a key equipment in the forging industry. It is characterized by intermittent operation and large temperature changes. It often works under conditions such as high temperature and strong vibration, collision of loading and unloading machinery, and chemical erosion of iron oxide scale. It seriously damages the lining bricks of the furnace, shortens the service life of the furnace, and also causes the heat loss of the furnace to increase.

Application of High-Strength Refractory Castables in Reforging Heating Furnaces

High-strength refractory castables are good lining materials for forging heating furnaces, which extend the life of the furnace, reduce energy consumption, and achieve good economic results. In the design, the overall furnace structure of the chamber heating furnace was improved. The improvement steps are carried out according to the reservation of furnace top, furnace wall, furnace bottom and expansion joints.

High-Strength High-Alumina Refractory Castables

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(1) Stove top

The furnace top is a composite flat furnace top, and 48 high-aluminum hanging anchor bricks are evenly buried in the furnace top, with the brick length being 460mm. The anchor bricks and refractory castables form a whole, and the thickness of the cast layer is 300mm. The furnace top adopts a metal hanging structure, and the hanging bolts are connected to the metal hanging beams. The force of the hook is adjusted evenly to maintain the overall force and is in a free hanging state. The upper surface of the furnace roof is covered with a layer of 70mm thick refractory fiber to enhance the heat preservation performance of the furnace.

(2) Furnace wall

The furnace wall is a composite type. A δ=8mm steel plate is added around the furnace wall. A 40mm thick refractory fiber is pasted on the inside of the steel plate, and a 114mm lightweight refractory brick is built on the inside of the refractory fiber. The lining is integrally cast with high-strength refractory castables, and the thickness of the casting layer is 300mm. The burner hole is reserved during pouring, and the burnt bricks are embedded after the castable solidifies. The gap between the burner brick and the castable is filled with fine powder, and the furnace wall is poured at one time. Compared with brick furnace walls, it has good impact resistance and thermal insulation effects, reduces heat loss and saves energy.

(3) Furnace bottom

In order to improve the wear resistance of the furnace bottom, steel fiber reinforced castables are used and integrally poured into the pit surface. The working layer at the furnace bottom is 280mm thick, and 210mm thick refractory clay bricks and lightweight refractory clay bricks are laid underneath. Some clay bricks were laid in areas with lower temperatures, up to the ground level. Three flue holes are left in each room to communicate with the main flue, and the flues are all built with refractory sticky bricks.

(4) Connection between furnace top and furnace wall

The furnace wall does not bear the weight of the furnace top, and there is a 20mm gap between the two to allow the furnace wall to expand due to heat. In order to prevent the flame from escaping from the joint between the furnace wall and the furnace top, the two should overlap by at least 150mm, and clay bricks should be built on the side of the furnace top to isolate the flame. At the same time, wet clay bricks are used on top, and the gaps between the furnace top castables, refractory clay bricks and refractory fiber fillers are sealed to prevent fire escape.

(5) Expansion joints left

Leave an expansion joint at the four corners of the furnace wall, at the center of the middle partition wall, and at the joint between the partition wall and the front and rear. The width of the expansion joint is 3~4mm, and flammable corrugated board is used as the filling material. There are no expansion joints in the stove top itself. 20mm refractory fiber is laid around the working layer of the furnace top to replace the expansion joint.

(6)Construction

The construction of high-strength refractory castables is different from ordinary refractory castables. Therefore, careful construction must be carried out in accordance with relevant regulations. Before installing the formwork, install the burner, flue and furnace door membrane. Then set up the furnace wall formwork, and connect the hole membrane to the furnace wall formwork. The furnace top formwork is set up after the furnace bottom castables have a certain strength. After the support is completed, the anchor bricks are hung. The gap between the lower end of the anchor brick and the formwork is 0~5mm. The formwork support must be firm and must not be loose. High-strength refractory castables are finished materials that must be stirred evenly by a forced mixer before pouring. After the materials are put into the mixer and mixed dry for 1 minute, 6.5%~7.2% water is added, and then wet mixed for 3~4 minutes before the material is discharged. The mixture poured out from the mixer must be used within 30 minutes.

To purchase high-quality refractory castable products, please choose Rongsheng Refractory Castable Manufacturer. Our refractory products have been sold to more than 120 countries around the world, such as South Africa, Chile, Egypt, Colombia, Uzbekistan, Italy, Indonesia, Ukraine, Hungary, Spain, Kenya, Syria, Zambia, Oman, Venezuela, India, Peru, the United States, Ethiopia, etc. Moreover, our product quality is reliable and our after-sales service is guaranteed. Contact us for a free sample and quote for your refractory castables.

Applications of Wear-Resistant Castables and Refractory Precast Shapes

August 6, 2024 by rsrefractorycastable

Silicon carbide castables are often used in boiler linings or linings of iron trenches in front of blast furnaces. High-strength wear-resistant castables are used in boiler linings. It is also used in the unloading part of the rotary kiln and the use effect is very good, here, it is called anti-crushing castable in this part.

Conditions for Use of Silicon Carbide Wear-Resistant Castables

Silicon carbide castables can be used under high temperatures and harsh conditions. Silicon carbide castables have particularly good wear resistance. As long as it is used in the right location, its service life will be increased by more than 50% compared with ordinary low-cement castables.

Wear-Resistant Corundum Silicon Carbide Castable — Wear-resistant Corundum Silicon Carbide Castable in Rongsheng Factory

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What is the Suitable Working Temperature for Silicon Carbide Castables?

Silicon carbide castables are suitable for use in furnace linings under reducing atmospheres, and are more effective when used at temperatures above 1500°C.

Silicon carbide castable is a composite refractory castable. A certain proportion of silicon carbide, alumina powder, corundum or high-content bauxite raw materials is added to the inner matrix. The bonding agent is composed of pure calcium aluminate cement and some other chemical ingredients.

The use temperature of silicon carbide in reducing atmosphere is as high as 2454°C. If used in an oxidizing atmosphere, oxidation reactions may easily occur. If used in an oxidizing atmosphere, silicon carbide cannot produce a protective film on the surface. If the oxidation pressure is high, the surface layer will crack or peel due to temperature changes and mechanical impact.

If the oxygen partial pressure is low, the protective layer cannot be formed and will diffuse in the pores, resulting in a reduction in the quality of silicon carbide castables.

Castable manufacturers will add a certain proportion of binder to the composite process ratio to adjust the oxidation reaction. Under normal circumstances, metallic silicon is used to regulate the oxidation reaction. It is also useful to use sodium salt solution or sol to penetrate into the open pores of the material to inhibit oxidation and increase the service life.

Therefore, silicon carbide castables are not suitable for use at low temperatures, especially in oxidizing atmospheres. When used in a reducing atmosphere, the higher the temperature, the better the effect.

Refractory Precast Shapes for Sleeve Kiln Arch Blocks

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Application of Wear-Resistant Castables and Refractory Precast Shapes in Sleeve Kiln Arch Blocks

In the arch bridge part of the sleeve kiln, both wear-resistant castables and refractory Precast Shapes can meet the requirements. Prefabricated parts have a long cycle but good results, and the construction of wear-resistant castables is complicated but has strong adaptability. Enterprises can make reasonable choices based on actual working conditions.

The arch bridge of sleeve lime kiln has always been a difficult problem to overcome. Because this part needs to be load-bearing, wear-resistant, and wind-resistant, the required refractory materials are difficult to determine with just one material.

In this case, many manufacturers use a dual method of laying refractory bricks first and then making refractory castables to increase the service life of the arch bridge. Another reason is that there are many types of refractory bricks used in this part, their weight is small, production is inconvenient, and the production cycle is long. In this case, Refractory Precast Shapes were used to meet the requirements of this part.

According to the current feedback from manufacturers, the service life of refractory prefabricated parts used in arch bridges is quite good, usually more than 3 years, while the use of magnesia bricks is only about one year. Using a mixture of refractory bricks and castables, the service life is probably more than one year.

However, the use of refractory Precast Shapes requires large molds, and the production cycle must be at least 20 days. During construction, a crane can be used to place them at the location of use. As the temperature of the kiln body rises, the refractory Precast Shapes are also baked, which can be said to be the best of both worlds. However, the model is large and the price will be higher than using wear-resistant castables.

If the production cycle of refractory prefabricated parts will be limited in the case of emergency repair, wear-resistant castables should be used. However, due to the large area and thickness of wear-resistant castables, the anchors must be changed into cage shapes according to the specifications of the parts used. Weld the cage-like anchoring material at the arch bridge part and then find high wear-resistant castables, which can also meet the use needs of this part.

In short, prefired Precast Shapes or wear-resistant castables are used for the arch bridge of the sleeve kiln, both of which can meet the usage requirements. Enterprises can decide based on actual construction time and other advantageous conditions.

Ultra-Low Cement Iron Ditch Castable – Long Service Life Refractory Lining

July 30, 2024 by rsrefractorycastable

At this stage, most blast furnaces use alumina-silicon carbide-carbon iron trench castables. With the advancement of smelting technology, the amount of iron passed through at one time has increased from the initial tens of thousands of tons to hundreds of thousands of tons, which has also put forward higher requirements for the performance of iron trench materials. The fastest eroding part of the tap trench is the impact zone. In addition to thermal shock, molten iron erosion, and oxidation, the main damage to the iron trench is the high-temperature erosion of molten iron and iron slag.

During the smelting process of molten iron, more silica will be generated. Calcium oxide (the main source of calcium oxide is cement), silica and alumina will react together to form anorthite and anorthite (liquid phase at the operating temperature). Or low melting phase such as calcium aluminate. These low melting phases greatly reduce the high-temperature performance of the iron trench material. Seriously affects the corrosion resistance of the product, thereby affecting its service life. When the low-melting phase is generated, the alumina powder used as the matrix is also consumed. After the matrix is consumed and eroded, the aggregate particles that serve as the skeleton will loosen and peel off, causing the product structure to be destroyed.

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Ultra-Low Cement Bonded Al2O3-SiC-C Iron Trench Castable

At present, most blast furnace trenches use alumina-silicon carbide-carbon castables with high-purity calcium aluminate cement as the binding agent. Calcium oxide is inevitably introduced, thus forming a low-melting phase during high-temperature use. If cement is not used and only ultrafine powders such as alumina powder and silica powder are used, the demoulding strength at room temperature will be low and cannot meet the Stinging requirements. Although there are reports using P-Al2O3 combination (hydraulic alumina) and sol-gel (silicon and aluminum) combination to make iron trench castables. However, there are problems such as fast solidification and difficult control during on-site construction, so it has not been widely used. Cement is still the main binding agent for iron trench materials at this stage. Develop ultra-low cement-bound Al2O3-SiC-C iron trench castables and combine them with ultra-fine powder to minimize the introduction of calcium oxide while ensuring the demoulding strength at room temperature. It not only ensures that it will not be damaged after casting and demoulding, but also improves the high-temperature strength and performance of the material by reducing the low melt content of the castable at high temperatures. It can well resist the erosion of molten iron and slag, thereby extending the service life of the iron trench.

Through experiments, it was found that if the amount of cement added is too small, the demoulding strength at room temperature cannot be guaranteed, and if the amount added is high, the high-temperature performance will deteriorate. Based on the above properties, the optimal addition amount of cement in Al2O3-SiC-C iron trench castable is 0.6%.

Rongsheng Low Cement Silicon Carbide Castable (Al2O3-48%,SiC-30%)

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Industrial testing and applications. On the basis of laboratory research results, a plan to add 0.6% cement will be carried out industrial testing in a steel company. The blast furnace capacity is 1080m3, the length from the main trench to the small pit is 14.5m, the slag trench is 11m, and the shared material is 73t. Among them, the main ditch uses 49t. From use to the next set-up, it was used for a total of 84 days, and the iron output was about 165,000 tons, which achieved good results.

in conclusion. Reducing the amount of cement added can improve the high-temperature performance of iron ditch castables. The main reason is to reduce the formation of eutectic anorthite and generate staggered network mullite crystals in the castable to improve high-temperature performance. When the cement addition amount is 0.6%, the overall performance of the castable is better. The iron ditch castable produced on this basis has achieved good industrial test results.

The Castables used in Copper Smelting Trenches Must Have the Following Properties:

According to the working environment and conditions of the copper tapping trench, the castables used for the copper tapping trench must have the following properties.

(1) It has good thermal shock stability.
(2) Resistant to corrosion and erosion, and resistant to structural spalling.
(3) It has suitable expansion properties, anti-permeability, and does not stick to copper liquid.
(4) It has lower porosity and higher strength.

Aluminum Silicon Carbide Castables for Sale

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High Alumina-SiC Ultra-Low Cement Castable

In response to usage requirements, refractory material manufacturers have cooperated with enterprises to develop high-aluminum-SiC ultra-low cement castables.

The Adding Amount of Silicon Carbide

Silicon carbide has the advantages of excellent slag resistance, small thermal expansion coefficient, high thermal conductivity, and good wear resistance. Adding an appropriate amount of silicon carbide to high-aluminum ultra-low cement castables can improve its resistance to copper liquid erosion and structural spalling. For the sample with SiC added, as the silicon carbide content in the matrix increases, the compressive strength of the castable first increases and then decreases. The linear change rate after burning increases with the temperature, from shrinkage to expansion, and changes with the SiC content. increases with the increase. This is because as the temperature continues to increase, the oxidation rate of SiC accelerates.

The Adding Amount of Silica Powder

The addition of silica powder can improve the normal temperature strength and post-fired strength at medium and high temperatures of the castable, and reduce the apparent porosity of the material. Microsilica powder can effectively reduce the oxidation rate of SiC at high temperatures. Because silica powder not only forms a siliceous protective film on SiC, but also sinters easily at high temperatures, increasing the thickness of the protective siliceous layer. Therefore, silica powder has a protective effect in inhibiting SiC oxidation when the temperature is above 1000°C. The results show that when the SiC addition amount is optimal and an appropriate amount of silica powder is added, the various properties of the sample are the best and the oxidation rate of SiC is the lowest.

Sintering Agent

The temperature of copper extraction is between 1150 and 1300°C. At this time, the bonding phase of the general castable is at the weak link. That is, a strong ceramic bond is not formed, and erosion often occurs. In order to improve the erosion resistance of the castable and the oxidation resistance of SiC, appropriate sintering agents should be added. To this end, the types and amounts of sintering agents were studied. The results show that when the adding amount of composite sintering agent is 10%, products with excellent performance can be obtained.

Application of High-Aluminum-SiC Ultra-Low Cement Castable in Copper Channel of Copper Converter

Based on the above experimental results, high-aluminum-SiC ultra-low cement castables were used for industrial testing on the copper tapping channel of the blister copper converter. The service life has reached more than three times that of the original magnesia ramming material. The main reason for the damage of high-aluminum-SiC ultra-low cement castables is that the surface layer is oxidized, followed by slag hanging, and peeling off due to thermal shock. The new surface layer oxidizes, slags, and peels off, over and over again, and is finally destroyed. Due to the superior oxidation resistance of this castable, oxidation is limited to the surface layer, so the damage rate is much slower than that of magnesia ramming materials.

Application of Ferrosilicon Nitride in Al2O3-SiC-C Blast Furnace Iron Trench Castables

July 23, 2024 by rsrefractorycastable

The blast furnace iron trench is a channel for guiding high-temperature molten iron and molten slag. Its refractory lining is subject to high temperature, mechanical and chemical erosion by molten iron and slag liquid. The first is the scouring effect on the surface of the refractory material when iron and slag flow. Secondly, due to the frequent alternation of hot and cold during tapping or the long-term action of high temperature, micro-cracks occur in the refractory material. Such microcracks promote the penetration and structural damage of molten iron and slag. Therefore, the iron trench lining material is required to have strong resistance to the erosion of molten iron and slag, good thermal expansion stability, small change in burnt volume, and strong oxidation resistance. It is easy to construct and does not adhere to slag iron, making it easy to repair and dismantle. It has a uniform, highly dense structure and high strength. It does not produce harmful gases and is conducive to environmental protection.

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Service Life of Blast Furnace Tap Trough Refractory Materials

After the blast furnace became larger, the usage conditions of the tap trough also changed, and the erosion and wear of the trough wall by molten iron increased. Increasing the generation gap, reducing costs and reducing the work pressure of workers behind the furnace are the main goals of the work behind the furnace. For the main iron trench and different parts, the erosion conditions are different, and the selection of materials should be different to achieve a comprehensive and balanced economic life. For iron ditches, efforts should be made to improve the anti-penetration properties of the material. As far as the construction technology and maintenance process are concerned, some operating methods are also closely related to the service life of the material.

Damage Mechanism of Blast Furnace Iron Trench Refractory Materials

The damage to refractory materials used in blast furnace iron trenches is mainly due to cracks, chemical erosion, penetration, and erosion caused by thermal shock of high-temperature molten iron and slag.

The first is the effect of high-temperature molten iron. Since the blast furnace has a certain pressure, the molten iron with a temperature of up to 1500°C spurting out from the blast furnace directly impacts the working surface of the iron trench. This results in erosion and damage of trench lining materials, especially within the impact zone. The vortex formed here not only intensifies the thermal impact of molten iron and slag on the trench lining, but also intensifies the erosion and erosion of the iron trench lining. The most severe damage is to the trench lining material. Therefore, the damage here determines the service life of the tap hole.

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Secondly, in the metallurgical industry, the damage caused by molten slag to refractory materials is the most serious. Since the slag contains relatively complex chemical components, it is easy to react with components in refractory materials to form low melting point substances. Causes damage to the structure of the refractory material and reduces the corrosion resistance, erosion resistance and other properties of the refractory material. When the blast furnace taps iron, in addition to high-temperature molten iron, there is also high-temperature slag entering the tap trough. Slag not only aggravates the erosion of the iron trench lining, but also tends to adhere to the trench wall. It is the main factor that damages the trench lining material. In addition, the damage to the iron trench lining material caused by molten slag also varies depending on the structure of the tap trench. For molten iron tap trenches, the main damage caused by molten slag is erosion and erosion. As for the non-molten iron tap trough, in addition to the above functions, more and more slag adheres to the trench wall and is deposited, which hinders the normal use of the tap trough. Therefore, slagging operations must be carried out in front of the furnace. When slag removal is carried out, the refractory material of the trench wall will be removed together with the bonded slag, which is the greatest damage to the non-molten iron tapping trench lining.

Third, although the blast furnace is a high-temperature equipment that operates continuously, tapping is an intermittent operation, causing the trench lining refractory material to withstand rapid changes in temperature. At this point, the molten iron tap trough also has advantages over the non-molten iron tap trough. Therefore, rapid changes in temperature reduce the thermal shock stability of iron trench lining refractory materials.

In addition to the above damage, the penetration of molten iron into the iron trench lining material is also one of the factors that destroys the material structure. It causes the material to erode and peel off, thereby reducing erosion resistance.

Rongsheng Silicon Nitride Combined Silicon Carbide Castable for Iron Trench

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Ferrosilicon Nitride is Used in Al2O3-SiC-C Blast Furnace Iron Trench Castables

In the past, the iron trenches of small and medium-sized blast furnaces were mainly artificial ramming materials mixed with coke, clay clinker and clay, mixed with tar or syrup, and were manufactured by each ironworks. This kind of iron trench lining has a short service life and the iron flow capacity is less than 10,000 tons. In long-term production practice, people have gradually realized that adding silicon carbide and graphite can significantly increase the service life of the tap hole. In terms of refractory aggregates, corundum materials, high-aluminum vanadium clay, magnesia-aluminum spinel materials, etc. have been tested. In terms of binders, various iron trench materials including resin bond, cement bond, and clay bond were tested. After continuous attempts, various types of iron trench materials suitable for large, medium and small blast furnaces have been gradually formed. For high-temperature and high-pressure operations, the tapping volume is large, the flow rate is fast, the temperature is high (1500°C), the tapping times are frequent, the time is long, the amount of slag is large, and the tap trough lining material is used in harsh conditions. To this end, a new generation of iron trench materials based on Al2O3-SiC-C has been developed, which basically meets the production requirements, and the iron throughput ranges from tens of thousands to 100,000 tons. Blast furnace trench castables.

Al2O3-SiC-C castable has good slag erosion resistance and erosion resistance. It has been widely used in the main trench, skimmer and branch trench of blast furnace tap trench. However, due to the development of smelting technology, the continuous improvement of blast furnace utilization coefficient and the requirement of longevity of blast furnace, it is urgent to further improve the service life of Al2O3-SiC-C iron trench castables. However, the current Al2O3-SiC-C iron trench castables are prone to falling off due to periodic chemical erosion of slag and molten iron, thermal shock and erosion of slag and iron. At the same time, the oxidation of silicon carbide and carbonaceous materials in the castables at high temperatures will also cause structural damage to the materials, which will lead to the damage of the castables.

Ferrosilicon Nitride Al2O3-SiC-C Iron Trench Castable

In recent years, research on the use of ferrous silicon nitride in Al2O3-SiC-C iron trench castables has been increasing. Si3N4 in ferrosilicon nitride has the advantage of not being completely wetted with slag and iron, which can improve the corrosion resistance of iron trench castables. The oxidation product of Si3N4 will form a SiO2 protective film on the surface of the sample, hindering further oxidation of the material and enhancing its anti-oxidation performance. The metallic phase Fe has the effect of assisting sintering and can improve the mechanical properties of the castable. It has better antioxidant properties than pure Si3N4. At the same time, the N2 generated by the oxidation of Si3N4 in ferrosilicon nitride at high temperatures and the CO generated by the oxidation of carbon materials will block the internal pores of the material, thus effectively preventing further oxidation.

Long Service Life Silicon Nitride Combined Silicon Carbide Thermal Shock Resistant Castables

July 16, 2024 by rsrefractorycastable

With the development of the cement industry, in order to adapt to the requirements of large-scale, long-lasting, energy-saving and environmentally friendly cement industry, the requirements for refractory materials for the lining of large and medium-sized cement kilns are becoming increasingly stringent. Existing refractory materials can no longer meet production needs in actual use. Especially at the kiln mouth, grate cooler, coal injection pipe, smoke chamber, top of preheater and other parts. Due to high-temperature thermal stress, rapid cooling and rapid hot air flow impact, high-temperature cement clinker wear and high-temperature gas alkali corrosion, it is easy to cause cracking, peeling and wear of the lining, making it difficult to meet the requirement of the kiln age being more than one year. Moreover, the corundum-silicon nitride-silicon carbide composite castable used in the tuyere belt of the ironmaking blast furnace can be poured and constructed quickly. However, its alkali resistance and thermal shock stability cannot meet the requirements for refractory materials for large and medium-sized cement kiln linings.

Silicon Nitride Combined Silicon Carbide Castable

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Therefore, it has become a primary task to prepare a refractory material with strong thermal shock stability, high compressive strength, small thermal expansion coefficient, low thermal conductivity, good alkali resistance and long service life. Long-life silicon nitride combined with silicon carbide thermal shock-resistant castables solves the above technical problems for the blast furnace and cement industry.

Silicon Nitride Combined with Silicon Carbide Thermal Shock Resistant Castable

This castable uses silicon nitride and silicon carbide as the main raw materials and is also supplemented with corundum, activated alumina and other materials. Using composite explosion-proof materials and additives, silicon nitride combined with silicon carbide thermal shock-resistant castables are made. Its raw material composition is as follows:

Silicon nitride 150-300 mesh, 5-20%.
Black silicon carbide 100-200 mesh, 10-30%.
Green silicon carbide 150-300 mesh, 5-20%.
Tabular corundum, 20-30%.
White corundum, 15-30%.
Activated alumina 300-600 mesh, 3-12%.
Metal aluminum powder 80-150 mesh, 0. 5-3%.
Heat-resistant steel fiber 5%.
Metal silicon powder 100-200 mesh, 2-8%
Aluminate cement 3-6%.

The silicon nitride combined with silicon carbide castable has excellent high-temperature stability, high thermal shock stability (water cooling, 1100°C ≥ 30 times), and high alkali corrosion resistance (level 2 or above). Excellent normal and high-temperature strength and high-temperature material wear resistance. Suitable as long-life (more than one year) large and medium-sized cement kiln lining materials. It is especially suitable for key parts with harsh working conditions such as the kiln mouth, coal injection pipe, cement kiln smoke chamber, grate cooler, and top of the preheater of large and medium-sized cement kilns.

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Analysis of the Causes of Peeling, Cracking, and Peeling of Castables for Cement Kiln Burner Linings

The burner is an important process equipment of the cement kiln firing system. It has a great relationship with clinker output and quality, the life of refractory materials in the kiln, clinker coal consumption, environmental protection emissions, etc. The main reason that affects the service life of the burner is the damage of the burner lining castable. How to extend the service life of the burner lining castable is particularly important. The four-channel pulverized coal burner of a cement manufacturer uses Al₂O₃-SiC series low-cement refractory castable as a protective lining with a thickness of 100mm. Serious damage occurred to the burner head and bottom 2 months after it was put into use. The main modes of damage are peeling, cracking and peeling.

Burner Lining Castable Damage

The damage to the burner lining castable is shown in Figure 1. Take a piece of lining castable from the burner that is completed from outside to inside as a sample, and observe the overall condition of the sample. Divide the residual lining sample into four layers from outside to inside according to different colors. The division of residual lining layers is shown in Figure 2.

Figure 1 Damage to Burner Lining Castables

Figure 2 Analysis of 4 Levels of Lining Castables

From the appearance of the damaged castable, it can be clearly seen that the first layer is light yellow and has obvious erosion, indicating that a liquid phase has been produced on the surface of the castable. The second layer appears white and has the loosest structure. The castable has completely deteriorated and is basically a crystallized accumulation of alkali salts. Layer 3 appears light black and has a dense structure, and the aggregate particles in the castable components can be seen. Layer 4 appears gray and has a dense structure. No crystalline material is found. The matrix part of the castable and the aggregate particles can be clearly seen.

After combining experiments and analyzing its components, a conclusion is drawn.

(1) The outer surface of the burner lining castable produces low melting point anorthite and potassium feldspar, which produces a liquid phase at high temperatures, reducing the surface strength of the castable and causing corrosion damage to the castable.
(2) The middle brushing of high-temperature secondary air damages the SiO₂ film formed by the oxidation of SiC on the surface of the castable, causing alkali salts to enter the castable to form continuous erosion.
(3) The chemical corrosion damage of the burner mainly comes from K salt, which mainly has two aspects: on the one hand, the K salt that penetrates into the castable reacts with the matrix to generate new compounds, destroying the matrix composition of the castable. On the other hand, due to the density difference of the potassium salt itself, volume expansion occurs after deposition and cooling in the castable matrix. The combined effect of two reasons leads to damage to the castable lining.

Cost-Effective Low-Cement Castable with Excellent Thermal Shock Stability

July 10, 2024July 9, 2024 by rsrefractorycastable

Low cement castable is one of the most widely used castables in thermal kiln linings, with Cost-Effective performance and easy construction. Low-cement castables have the advantages of less water addition, high density, good volume stability, and high strength at high temperatures. However, low-cement castables have poor air permeability and poor thermal shock resistance at high temperatures. When the castable is baked after being demolded, the low-cement castable is prone to bursting, peeling, peeling, etc. In severe cases, it may even damage the entire kiln lining. Therefore, how to improve and enhance the explosion-proof performance of low-cement castables is of great significance to the large-scale application and development of low-cement castables.

Low Cement Castable Directly from Factory

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How to Increase the Explosion-Proof and Thermal Shock Stability of Low-Cement Castables?

Rongsheng castable manufacturer, in order to improve the explosion-proof properties of low-cement castables, uses the method of adding explosion-proof fibers to low-cement castables to increase the permeability of the castables. The addition of explosion-proof fiber significantly improves the explosion-proof performance of low-cement castables. After the explosion-proof fiber is added to the castable, the explosion-proof fiber will shrink and melt when the castable is heated and baked after demoulding. Elongated pores are formed in the castable, increasing the opening vents inside the castable and improving the air permeability of the castable. This accelerates the discharge of water vapor, thereby improving the burst resistance of the castable and improving the explosion-proof performance of the castable.

The overall strength of low cement castables is very high at high temperatures. However, in some thermal kilns that work intermittently, frequent shutdowns and restarts will affect the service life of the low-cement castable working lining. In the case of rapid cooling and heating, it is very easy for the castable lining to peel off and crack, affecting the service life of the low cement castable.

Rongsheng Unshaped Refractory Castable Manufacturer, adding a certain amount of silicon carbide to low-cement castables will significantly improve the thermal shock stability of low-cement castables when facing rapid cooling and rapid heating conditions. However, the amount of silicon carbide incorporated needs to be strictly controlled. Because silicon carbide has a high thermal conductivity, when too much silicon carbide is added, the overall thermal expansion coefficient of low cement castables will increase, which is detrimental to the thermal shock stability of low cement castables. Castable manufacturers strictly control the amount of silicon carbide added to optimize the thermal stress of low-cement castables caused by excessively high thermal conductivity of silicon carbide. Only then will the low-cement castables have the best thermal shock stability when subjected to thermal shock. .

Whether low-cement castables need to improve their explosion protection or thermal shock stability, a comprehensive analysis needs to be made based on the working environment, operating temperature, erosion conditions, etc. of the thermal kiln. Then, make a reasonable formula based on the actual use needs of the enterprise’s kiln. The refractory material industry is an industry with very strong practical applications. There is no perfect refractory material. You can only find the most suitable refractory material based on the actual situation.

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Silicon Carbide Composite Refractory Castable

What happens when silicon carbide is added to low-cement refractory castables? That turns into silicon carbide low cement castable!

The biggest feature of silicon carbide castable is wear resistance, followed by strong corrosion resistance. Its technological feature is that based on the process of refractory castables, a certain proportion of silicon carbide is added to form a composite refractory castable.

Because silicon carbide has strong wear resistance, adding it to refractory castables can improve the wear resistance of the castables. Moreover, the wear resistance coefficient of the castable is reduced, and the service life can be increased by 1 to 2 times. Silicon carbide has high thermal conductivity and small thermal expansion coefficient. Adding an appropriate proportion can increase the thermal shock resistance of the castable, and the thermal shock resistance of the castable is also relatively good. Especially for silicon carbide combined with silicon nitride products, the thermal shock resistance will be increased by 2 times compared to the thermal shock of the castable before adding it. It also prevents slagging or skin formation on the surface of the castable.

However, refractory castables with high silicon carbide content have high thermal conductivity, and the disadvantage of silicon carbide castables is that they are easily oxidized. Manufacturers add metallic silicon powder to the castable to inhibit the oxidation of silicon carbide. Castables combining silicon nitride with silicon carbide have lower oxidation resistance. Because the base material of silicon nitride combined with silicon carbide castable is in the form of interwoven fibers, it has high air permeability and plays a small protective role on silicon carbide particles. In silicate-bonded and silicon oxynitride-bonded silicon carbide products, the surface of the silicon carbide particles is wrapped by a continuous base material. Therefore, it has strong antioxidant properties.

Silicon carbide castables can maintain high strength and wear resistance at high temperatures, and have good chemical stability and will not be eroded by acid and alkali solutions. In addition, the wetting angle of silicon carbide with molten metal and slag is large. It has good corrosion resistance to various furnace lining solids, liquids and gases.

Rongsheng Unshaped Refractory Castable Manufacturer

Rongsheng Unshaped Refractory Castable Materials Manufacturer is a powerful manufacturer of refractory materials production and sales. Our environmentally friendly, fully automatic unshaped refractory material production line ensures the smooth delivery of unshaped refractory materials. Moreover, our professional technical team can customize the refractory castable formula according to the actual working conditions of the kiln lining to ensure the long service life of the refractory lining. Contact us to get free samples and quotes.

Castable Low Cement Lining With Silicon Carbide

July 2, 2024 by rsrefractorycastable

Low cement silicon carbide refractory castable is a special refractory material. Made of low cement ratio, silicon carbide aggregates and powders, ultrafine powder, CA-70 cement and antioxidants. It is suitable for thermal equipment such as power generation boilers, non-ferrous metallurgical furnaces and incinerators. It has low linear expansion coefficient, high thermal conductivity, high strength and good wear resistance. Low-cement silicon carbide refractory castables can improve the fire resistance and thermal efficiency of the equipment under reasonable proportions and use under appropriate conditions, and the application effect is good.

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Low Cement Silicon Carbide Refractory Castable

Low cement silicon carbide refractory castable is a special refractory material suitable for thermal equipment such as power generation boilers, non-ferrous metallurgical furnaces and incinerators. This silicon carbide refractory castable has the following characteristics:

Low coefficient of linear expansion. As the main refractory aggregate and powder, silicon carbide has a low coefficient of linear expansion, which can reduce the possibility of thermal stress.
High thermal conductivity. Silicon carbide has good thermal conductivity and can effectively conduct heat and improve the thermal efficiency of the equipment.
High strength. The use of low cement ratio and reasonable binder can improve the strength of the castable and increase its compression and flexural resistance.
Good wear resistance. Due to the use of silicon carbide with SiC greater than 97% as refractory aggregate, the castable has excellent wear resistance.

Low Cement Silicon Carbide Castable in RS Factory

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Raw Material Composition of Low Cement Silicon Carbide Refractory Castable

The preparation of low cement silicon carbide refractory castable includes the following ingredients:

Refractory aggregates and powders mainly use silicon carbide with SiC greater than 97%, which has excellent refractory properties.
Ultra-fine powder. Adding SiO2 ultrafine powder can improve the density and refractoriness of the castable.
Binder, using CA-70 cement as the binder, can ensure that the castable has a certain strength and durability.
Antioxidants. Metallic silicon antioxidants are used to prevent the oxidation of silicon carbide.

The performance test results of the castable at different temperatures are as follows:

After drying at 110℃, the bulk density is 2.5g/cm³, the compressive strength is 45MPa, and the flexural strength is 9MPa.
After firing at 1000℃, the linear change is -0.2%, the compressive strength is 107MPa, and the flexural strength is 24MPa.
After firing at 1450℃, the linear change is +0.3%, the compressive strength is 130MPa, and the flexural strength is 54MPa.
The thermal conductivity at 400℃ is 12.2W/(m·K).

In summary, low cement silicon carbide refractory castable has a low linear expansion coefficient, high thermal conductivity, high strength and good wear resistance. Through reasonable proportions and the use of appropriate materials, the fire resistance and thermal efficiency of the equipment can be improved. The castable has good application results in thermal equipment such as power generation boilers, non-ferrous metallurgical furnaces, and incinerators.

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Low Cement Mullite Corundum Castable

Low-cement mullite-corundum refractory castables use sintered or electro-fused mullite, brown corundum, alumina-based corundum and white corundum as refractory bone powder. Sometimes special-grade alumina clinker powder is also used, and ultra-fine powder is mixed with α-Al2O3 and silica fume. It is formulated with aluminate cement as binder and additional dispersant. This material is used for steel rolling heating furnace lining, water cooling pipe wrapping and burner bricks. The use effect is good on thermal equipment such as tundish slag weir, medium and small blast furnace tap trough and electric furnace cover.

Does Low Cement Castable Need to Add Steel Fiber when Used in Settling Chamber?

When low-cement castables are used in settling chambers, steel fibers are usually not required. When the design of the settling chamber is unreasonable, the discharge opening of the cone section is too small and the smoke dust needs to be beaten. At this time, steel fibers can be added to the low cement castable to enhance wear resistance and extend the service life. Under special circumstances, the settling chamber can be lined with clay bricks or high-aluminum castables with high-voltage electrical porcelain added.

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If low-cement castables are used in settling chambers, there is generally no need to add steel fibers.

If the lower opening of the cone section of the settling chamber is too small and needs to be beaten during use, just add steel fibers to the low-cement castable used in the cone section to increase traction, wear resistance, and erosion resistance. However, if the discharge port of the settling chamber is reasonable, and the size of the settling chamber and the rotary kiln are also reasonable, there is no need to add steel fiber to the castable.

The temperature of the settling chamber is not high, and it mainly plays the role of dust removal. The dust has fallen to the bottom before the flue gas flows out of the settling chamber, and is collected by the ash hopper at the bottom of the settling chamber. The unsettled dust is brought out with the flue gas. General low-cement castables can be used.

Generally, it is common to use high-aluminum castables and low-cement castables. However, clay bricks are also used as linings for settling chambers. There is also the use of high-aluminum castables with a certain proportion of high-voltage electrical porcelain added to the castables to create a glazed surface to facilitate the fall of smoke and dust.

Adding steel fibers to low-cement castables is rarely used in settling chambers. In recent years, the settling chambers of some white ash rotary kilns and zinc volatilization kilns are often lined with clay bricks. However, the size design of some settling chambers is not reasonable. If the settling chamber is too small, and the cone section discharge opening is also too small, there will be a situation of beating during the production process to make the smoke and dust sink. This will speed up the service life of the cone section lined with clay bricks or low-cement castables.

Therefore, under special circumstances, a reasonable proportion of steel fibers is added to the low-cement castable to increase the wear resistance of the cone section and extend its service life.

Application Advantages of Refractory Precast Shapes

April 27, 2024April 26, 2024 by rsrefractorycastable

Application cases of RS refractory prefabricated parts. Refractory prefabricated parts are most commonly used in small high-temperature kiln equipment. The products required at the construction site are produced in advance by the manufacturer to facilitate customer construction. Used for special-shaped or special-shaped refractory products. Refractory prefabricated parts are widely used in various industrial kilns due to their irreplaceable advantages. Its biggest advantage is that it can be pre-baked and directly hoisted, so the construction period is greatly shortened, and the quality is stable and easy to control.

Application Solutions for Refractory Precast Shapes

Refractory prefabricated parts are an important variety of refractory materials, and their applications account for an increasing proportion. Refractory prefabricated parts are made by dividing the parts of the high-temperature kiln to be constructed into small pieces in advance. And design it into a special shape, and make the mold according to the shape. In the factory, refractory castables and other materials are pre-cast, cured, and baked before being transported to the site for hanging and assembly before use.

Ultra Low-Cement Castable Precast Shapes for Iron Trough

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Castable precast shape refractories can be preformed into various shapes at will, with good thermal shock stability, high strength, and good spalling resistance. No joints, good air tightness, less heat loss, and energy saving. It can quickly repair the kiln and improve the furnace operation rate. It can realize direct hoisting and mechanized furnace construction, and the construction efficiency is high. It can solve technical problems in furnace construction for users and can be customized according to user requirements and furnace-type conditions. Consider lining body design and multiple construction options for users.

There are the following solutions for the shaping of unshaped refractory materials in cement kilns. As a result, the unshaped refractory materials used in special parts of the cement kiln are customized and produced. The product has the following characteristics:

(1) There is no need for on-site pouring construction or formwork pouring, which reduces labor costs and material costs.
(2) Heat-resistant anchors are not required, eliminating the material and construction costs of anchors.
(3) The pouring, curing, drying, and baking steps of prefabricated parts have been completed when delivered, saving a lot of construction time.
(4) It is not restricted by environmental and climatic conditions, which solves the problem that castable materials cannot be constructed on-site under natural conditions during hot summer and severe winter.
(5) It can be made into various special products with different sizes and shapes. Such as grate cooler low wall, tertiary air duct elbow, lifting gate valve, kiln tail smoke chamber, coal injection pipe, kiln mouth, and other refractory materials.
(6) Maintenance is easy to replace, has little waste loss, and saves labor and time. Corundum, fused mullite, special grade bauxite aggregate, and special wear-resistant materials are added to the material, and a certain proportion of special additives are added. Vibration forming. Therefore, the product has high strength, wear resistance, corrosion resistance, good mechanical impact resistance, and excellent thermal shock resistance. It has excellent peeling resistance and cracking resistance, long service life, convenient construction, safety, and reliability, and greatly shortens the construction period.

Application Advantages of Refractory Prefabricated Parts

Refractory Preforms refer to components with a certain shape and size made of refractory materials according to specific ratios and process conditions. The main raw materials of refractory precast shapes usually include refractory castables, refractory bricks, refractory fibers, and other special refractory materials. Refractory prefabricated parts are prepared under certain process conditions, which usually include mixing, molding, curing, and drying.

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Refractory Precast Shapes have the Following Advantages

stable quality. During the production process of prefabricated components in the factory, raw materials, proportions, and process conditions are strictly controlled. Therefore, product quality is stable and reliable.
Save construction time. The use of refractory prefabricated parts can significantly shorten the construction period and improve construction efficiency.
Reduce on-site labor. Prefabricated components are produced in factories, reducing the workload of construction workers and material handling on-site.
Good performance. Because the production process of prefabricated components is strictly controlled, their performance is often better than that of refractory materials constructed on-site.

Refractory prefabricated parts are widely used in various industrial furnaces and equipment in petrochemicals, metallurgy, building materials, electric power, and other industries. Such as heating furnaces, smelting furnaces, converters, gas generators, glass kilns, etc. Depending on the actual application environment and needs, refractory prefabricated parts can be customized with different shapes, sizes, and properties. When selecting refractory prefabricated parts, factors such as the working environment, usage conditions, performance of refractory materials, and construction requirements should be considered.

When using refractory prefabricated parts, you need to pay attention to the following points.

Storage and transportation. During storage and transportation, prefabricated parts should be protected from moisture, heat, and external force damage. It is recommended to store prefabricated parts in a dry, ventilated, and cool warehouse. And pay attention to reasonable stacking to avoid extrusion and deformation.
Install. When installing refractory prefabricated parts, design requirements, and construction specifications should be strictly followed. For different types of prefabricated parts, corresponding installation methods and connection methods need to be adopted. During the installation process, it should be ensured that the position of the prefabricated parts is accurate and that good connection and sealing properties are maintained.
Seam treatment. Seams between precast parts should be kept clean and tight to prevent heat loss and the penetration of aggressive gases. Depending on the actual working conditions and precast material, appropriate filling materials can be used for joint treatment. Such as refractory mud, refractory fiber, etc.
temperature control. During the initial heating and operation of the furnace, the heating rate and temperature should be strictly controlled. To prevent the refractory prefabricated parts from being damaged due to thermal stress caused by excessive heating. At the same time, regularly check the use of prefabricated parts to detect and deal with potential problems in a timely manner.
Maintenance and overhaul. During use, the refractory prefabricated parts should be inspected and maintained regularly. If damage, cracks, and other problems are found, they should be repaired or replaced in time. For prefabricated parts with a long service life, timely cleaning and maintenance can be carried out to extend their service life.
With proper selection, installation, and maintenance, refractory prefabricated components can provide efficient and stable performance for industrial furnaces. Save construction time and cost at the same time. In the continuously developing industrial field, the application of refractory prefabricated parts will continue to expand to meet the needs of various working conditions and environments.

Precast Shapes with Refractory Anchor Bricks for Heating Furnace Top

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What Should We Do if These Problems Arise with Refractory Castables and Castable Precast Shapes?

Unshaped refractory castables and castable refractory precast shapes have the advantages of convenient and fast construction and low labor intensity. It has been widely used in more and more high-temperature industrial kilns.

However, many corporate users have discovered some abnormal phenomena in refractory castables or prefabricated parts during storage or maintenance. For example, some have chalking, some have white hair, etc. In fact, these are caused by the contact between the high alumina cement hydration products in the refractory castable and the acidic gases in the atmosphere. As the water in the castable evaporates, salt substances continue to migrate and precipitate to the surface, and then slowly intensify the damage process of the refractory castable. Powdering occurs during the storage of prefabricated parts made from cement-containing refractory castables. Some of them have “white hair” growing on the surface, commonly known as white alkali, which causes the surface of the castable to become powdery. In severe cases, the strength of the castable will decrease.

Solution

Dry the castables as soon as possible after construction to remove moisture. Eliminate the carrier of sodium salt in the pouring body, so that the alkali stays in the construction body and no longer migrates to the surface.
When the construction conditions do not allow for timely drying, the castable environment must be sealed and the surface covered with plastic film to prevent moisture from carrying alkali from migrating to the surface.
Use refractory raw materials with low alkali content in the refractory castable to increase the viscosity and rapid hardening of the refractory castable, which can reduce the migration speed of sodium salt. Strengthen quality management and strictly control the amount of water added during construction.

Tips: Leave a message to ask your questions about kiln refractory castables, and we can provide solutions for free.

Steel Fiber Refractory Castable Precast Shapes

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RS Unshaped Refractory Castable Manufacturer

RS unshaped refractory castable manufacturer is a powerful manufacturer of refractory materials production and sales. Our environmentally friendly, fully automatic unshaped refractory material production line customizes unshaped refractory lining materials for high-temperature industrial furnaces. Extend the service life of the kiln lining, save the cost of production energy, and improve economic benefits. Customize refractory precast shapes, wear-resistant refractory castables, insulation castables, refractory plastics, refractory ramming materials, etc. from Rongsheng unshaped refractory material manufacturer. Contact us to get a free customized plan and quote.

The Difference between Hot Ramming and Cold Ramming of Carbon Ramming Materials

April 25, 2024April 18, 2024 by rsrefractorycastable

[Introduction] There are two types of carbon ramming materials, hot ramming and cold ramming. Hot pounding requires crushing and heating, and the wind pressure cannot be less than 0.5MPa. Cold ramming does not require heating, and the maximum thickness of each ramming cannot exceed 100mm. Carbon ramming materials are mainly used for gap filling and leveling of blast furnaces to achieve non-leakage requirements. Cold ramming changes the traditional hot ramming process and improves the performance of the lining. RS, a manufacturer of unshaped refractory castables, can provide high-quality carbon ramming materials and advanced construction technology guidance to help you extend the service life of your kiln lining and save production costs.

Construction Technology of Carbon Ramming Material

Carbon ramming material–Refractory Encyclopedia. RS Refractory Castable Manufacturer. There are two types of carbon ramming materials: hot ramming materials and cold ramming materials. Both hot and cold ramming carbon materials are monolithic refractory materials composed of powdery and granular refractory materials and binders. Under normal circumstances, it is recommended to use cold-rammed carbon materials.

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Before ramming hot carbon ramming materials, the carbon ramming materials must be crushed and heated. The heating temperature is set evenly according to the mixing temperature of the finished material. There are no hard lumps in the heated carbon material, so it can be laid and pounded. Use a hot hammer when pounding, and the material temperature should not be lower than 70°C. When using hot pounding, the hammer head should be heated to dark red, and the wind pressure should not be less than 0.5MPa. The upper and lower material layers should be staggered at a certain angle, and the pounding should be done continuously to prevent delamination. RS Castable Refractory Manufacturer. When each joint is made, the surface should be “scraped” or adhesive should be brushed, and then the material should be spread and pounded. When pounding, hammer half or one-third of the hammer back and forth 2-3 times in a straight line.

When adopting cold carbon ramming materials, due to the product process upgrade, there is no need to reheat the materials, and there is no need to stir during construction, and the materials can be poured directly into the use site. Subsequently, manual or mechanical methods are used for construction, and the ramming material is also rammed with one hammer and half hammer. RS Castable Refractory Manufacturer. However, it should be noted that the thickness of each pounding should not exceed 100mm until it is dense. The reference compression ratio is 40-45%. If additional thickness is required, a second layer can be laid for pounding. However, before laying, the surface of the upper layer must be roughened to make the upper and lower layers densely bonded. The wind pressure during ramming is the same as that during hot tamping, and cannot be less than 0.5Mpa.

Carbon ramming material is mainly used in the gap between the blast furnace bottom carbon bricks and the furnace bottom sealing plate, or between the hearth carbon bricks and the cooling stave. There is also leveling above the center line of the furnace bottom water-cooling tube and filling of the cooling staves, filling every corner and small gap to meet the requirements of no leakage of molten iron and gas. RS Castable Refractory Manufacturer.

The biggest difference between hot ramming and cold ramming of carbon ramming materials is that cold ramming has changed the old process of traditional hot ramming, the working conditions have been improved, and the performance of the lining has been improved.

RS Castable Refractory Manufacturers

RS Castable Refractory Manufacturer is a powerful manufacturer and seller of unshaped refractory materials. We can provide high-quality refractory lining material products, including various castables, ramming materials, refractory precast shapes, etc. Our products are of reliable quality and our professional construction technical team can customize refractory lining solutions and construction techniques for you. Maximize the service life of high-temperature industrial furnace linings and save production costs for enterprises. Contact us to get a free refractory lining solution and quote.

24 Kinds of Refractory Raw Materials Commonly Used in Unshaped Refractory Castables (2)

April 5, 2024 by rsrefractorycastable

In recent years, the output of unshaped refractory products has become higher and higher, and their application range has become wider and wider. Refractory castables do not need to be fired at high temperatures and can be used directly after being baked during construction. It is a new refractory material with a simple production process, saving energy and labor, mechanized construction, good integrity, easy repair, and long life.

Refractory castables are a type of refractory material that is mixed with a certain grade of refractory aggregates and powdery materials, binders, and admixtures and is used directly without going through the molding and firing processes.

According to the combination of raw materials, refractory castables can be divided into oxide refractory castables, non-oxide refractory castables, and composite refractory castables. Oxide refractory castables can be subdivided into non-alkaline refractory castables and alkaline refractory castables. Therefore, the performance of refractory castables mainly depends on the raw materials used in the formulation. In order to improve the performance of refractory castables, most manufacturers have used high-purity raw materials, homogeneous materials, electrofusion materials, synthetic materials, transformation materials, and ultra-fine powders as main raw materials. Let’s talk about the 24 raw materials that are often used in the formula of refractory castables.

Rongsheng Refractory Castable Manufacturer

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The Main Raw Material of Refractory Castables (13-24)

(13) Magnesite.

Magnesite is a natural alkaline mineral raw material with magnesium carbonate (MgCO3) as the main component. Our country is rich in magnesite resources, with high quality and large reserves. Magnesite is mainly distributed in Liaoning Province. Magnesite is mainly used to produce sintered magnesia, fused magnesia, and raw materials for the production of alkaline refractory materials.

(14) Sintered magnesia.

Sintered magnesia is a product obtained by fully sintering magnesite at 1600~1900℃. The main mineral is periclase. The MgO content of high-quality magnesia is generally above 95%, the particle volume density is not less than 3.30g/cm3, and it has excellent resistance to alkaline slag erosion. Sintered magnesia is one of the main raw materials for the production of alkaline refractory materials.

(15) Fused magnesia.

Fused magnesia is made by melting selected magnesite or sintered magnesite at a high temperature of 2500°C in an electric arc furnace. Compared with sintered magnesia, the main crystal phase periclase grains are coarse and in direct contact, with high purity, dense structure, strong resistance to alkaline slag, and good thermal shock stability. It is a good raw material for high-grade carbon-containing unburned bricks and amorphous refractory materials.

(16) Silicon carbide.

Silicon carbide is usually made from a mixture of coke and silica sand as the main raw materials through high-temperature smelting in an electric furnace. β-SiC (cubic crystal) is generated at a temperature of 1400-1800°C, and α-SiC (hexagonal crystal) is generated when the temperature is higher than 1800°C. Silicon carbide has high hardness, high thermal conductivity, low thermal expansion rate and excellent resistance to neutral and acidic slag. The composition range of commercial silicon carbide is 90%~99.5% SiC. Refractory castables, gunning materials, ramming materials and plastics often use silicon carbide with higher purity.

(17) Silica fume.

Silica fume is a by-product of the production of ferrosilicon and silicon products. Appearance: white to dark gray fine powder with round particles. The particle diameter is generally 0.02~0.45μm, the specific surface area is about 15~25m2/g, and the volume density is 0.15~0.25g/cm3. In recent years, some silica fume has become the leading product and is no longer a by-product. It has high purity, white color and stable ingredients. Shows good rheology when used in self-flowing castables.

(18) Graphite.

Graphite is divided into artificial graphite and natural graphite. Artificial graphite is made by sintering petroleum coke (heating to above 2800°C) or using graphite electrodes. Natural graphite crystal is a hexagonal crystal system with rhombohedral symmetry. There are usually three forms: amorphous, flake graphite and pure crystalline. Amorphous graphite (no form) and artificial graphite have better fluidity than flake graphite and crystalline graphite in castable applications.

(19)Asphalt.

Coal tar pitch has a higher residual carbon content than petroleum pitch, and both can effectively provide carbon components to refractory materials. According to the formula design requirements of the material, it can be used in the form of fine powder or granules. The use of bitumen is preferred over other forms of carbon (such as graphite) in amorphous refractory applications. Because asphalt has a low melting temperature, it can coat particles and thus provide a good protective layer against slag erosion.

(20) Calcium aluminate cement.

The main method for producing high alumina cement is the sintering method. Pureer limestone is the calcium oxide raw material from which all calcium aluminate cements are produced. Sintered alumina is used to produce high-grade calcium aluminate cement, while low-iron, low-silica bauxite is used as alumina raw material for mid-grade and low-grade high-alumina cement. Pure calcium aluminate cement or high alumina cement is the most important hydraulic cement used in the binding phase of refractory castables and shotcrete. During the construction of the refractory castable lining, the water temperature, water addition amount, mixing intensity and time, temperature and heating rate must be strictly controlled. Among them, temperature is the most important parameter, which significantly affects the generation of cement binding phase and the discharge of water in the early stage of heating.

(21) Silica sol.

Silica sol is a water-containing colloid with dispersed silica particles. It is a milky white liquid that is slightly sticky to the touch and has a high specific surface area. Silica sol can be cemented by dehydration, changing the pH value, adding salt or water-miscible organic solvents. When drying, silicon-oxygen (Si-0-Si) bonds are formed on the surface of the particles through rapid dehydration, resulting in polymerization and internal bonding. Silica sol is converted from solution into solid, commonly known as cementation. Commonly used in coatings, castables, pumped materials, ramming materials and gunning materials.

(22) Sodium silicate.

Commonly used silicates are sodium silicate (Na₂O·mSiO·nH₂O), potassium silicate and lithium silicate. The dehydrated product of sodium silicate is usually as transparent as glass and soluble in water, so it is also called water glass. The molar ratio of SiO₂/N₂O (called the modulus of water glass) in industrial products is between 0.5 and 4.0, and the molar ratio of sodium silicate for refractory materials is 2.2 and 3.35. The viscosity of sodium silicate aqueous solution is affected by its molar ratio and concentration, and changes significantly with temperature. Sodium silicate hydrates in aqueous solution, and the solution becomes alkaline. The smaller the molar ratio, the more obvious the hydration of sodium silicate is, and the pH value decreases as the molar ratio decreases. Sodium silicate with a high molar ratio reacts slowly. The choice of curing agent for sodium silicate combined refractory materials needs to be determined based on the application of the refractory materials. Commonly used curing agents include sodium fluorosilicate, polyaluminum chloride, phosphoric acid, sodium phosphate, polyaluminum phosphate, polymagnesium phosphate, ammonium pentaborate, glyoxal, citric acid, tartaric acid, ethyl acetate, etc.

(23) Phosphoric acid and phosphate.

Orthophosphoric acid itself has no binding properties. When it comes into contact with refractory materials, the two react quickly to form phosphate, which makes it show good adhesion. Different forms of phosphates can be used as binding agents. The salt most commonly used in refractory materials is aluminum phosphate. As a binding agent, aluminum dihydrogen phosphate is known for its solubility in water, binding strength and stability. Sodium phosphate is mainly used in refractory materials for cohesion, depolymerization and as a binding agent for alkaline gunning materials. Sodium polyphosphate is often used as a water reducing agent in castables. In addition, sodium phosphate can react with alkaline earth metal compounds (such as CaO and MgO), resulting in agglomeration. It is based on this performance of sodium phosphate that it is used in magnesia alkaline gunning materials.

(24)ρ-Al₂O₃

ρ-Al₂O₃ is a kind of activated alumina. It is different from other crystalline Al₂O₃ and is the worst crystallized Al₂O₃ variant. Among the various crystal states of Al₂O₃, only ρ-Al₂O₃ has a spontaneous hydration reaction at room temperature. The gibbsite and boehmite sol generated by hydration can play a cementing and hardening role. ρ-Al₂O₃ is eventually transformed into α-Al₂O₃ (corundum), an excellent refractory material at high temperatures. Therefore, this ρ-Al₂O₃ combined castable can be regarded as a self-bonding castable of refractory materials, which also acts as a binder. It itself is a high-grade refractory oxide with obvious excellent properties.

(THE END)

By selecting different raw materials as the main raw materials of refractory castables, castables with different properties, operating temperatures, and ranges can be made. Of course, only the main raw materials are not enough. Binders, admixtures, and some special additives are also needed. These are all to improve the performance of refractory castables. Rongsheng Unshaped Refractory Castables Manufacturer is a powerful manufacturer and seller of refractory castables. Our environmentally friendly, fully-automatic unshaped refractory material production line provides high-quality customized refractory lining materials for high-temperature industrial furnaces. Contact us to get a free refractory lining solution and quote.

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