The difference between them is: high alumina refractory clay is a refractory material used in the joints of refractory bricks, and the sheet material is high aluminum powder plus a certain proportion of binding agent and coagulant. After adding water or adding liquid binder, stir it into a slurry, and apply it on the surface of the refractory brick to adjust the size deviation. It can make the refractory bricks form a tight whole to prevent the damage of high temperature and external force. In other words, it is the fire clay for bricklaying. It is a finished solid powder.
High alumina cement is a kind of binder in the application of refractories. High alumina cement is also called aluminate cement. It is clinker with 50% alumina content calcined with bauxite and lime. Aluminate cement is yellow or Brown, high grade high alumina cement is white. The labels are 625#, 725#, 925# and CA70, CA80.
High alumina cement is closely related to refractory materials and can be used as a binder for various castables. In addition, some 525# and 425# refractory cements are equipped with gypsum bauxite for construction and special projects. High alumina cement has a good coagulation effect in the castable, which will make the castable have high temperature resistance and good strength. It is a raw material for refractory materials.
The high alumina refractory clay cement is also divided into multiple grades, and is used for building a variety of multi-material refractory bricks. It is divided into high alumina refractory mud and phosphoric acid refractory mud.
Although both high alumina refractory mud and high alumina cement are powdered materials, there is a big difference between high-alumina refractory mud and high alumina cement. High alumina refractory mud is processed into powder with high-alumina particles smaller than 180 mesh, plus some binders. , A synthetic material made of coagulant. The high alumina cement is the finished material after calcining bauxite and lime.
Therefore, high alumina cement and high alumina refractory mud are completely different products, but they are closely related to refractory materials. It is also one of two varieties with a large proportion among refractory products.
Adding steel fiber to the refractory castable can enhance the toughness of the castable. Moreover, it can enhance the wear degree and mechanical impact of the castable, and more importantly, improve the thermal shock stability of the castable.
The critical point of adding steel fiber to the castable is at 1350℃. If it exceeds 1350°C, the steel fiber will not play its due role. Like some castables used at positions exceeding 1400°C, there is no need to add steel fiber. No matter how much it is added, it will not have any effect, but it will increase the cost of the castable.
Like cement rotary kiln, white ash rotary kiln, pellet rotary kiln front and rear kiln mouths can use steel fiber-added refractory castables, because the front and rear kiln mouths have many castings, it is impossible to use refractory bricks for masonry, use steel fiber-added refractory pouring The material is not only resistant to tension and compression, but also resistant to fatigue and abrasion.
Not only steel fibers are added to refractory castables, but also appropriate amounts of steel fibers can be added to plastics and ramming materials to improve cracking resistance and peeling resistance. And in the curing process, adding steel fiber can prevent the linear shrinkage of the castable.
However, the amount of steel fiber added should not be too large, which will cause internal changes in the castable. After the castable is sintered at a high temperature, the expansion coefficient will increase and the thermal conductivity will also increase. Especially during construction, excessive addition of steel fiber will cause unnecessary troubles for construction.
There are many kinds of refractory castables with steel fiber, and there are many grades, such as high aluminum and steel fiber, corundum and steel fiber, mullite and steel fiber, and silicon carbide steel fiber. Compound refractory castable. It’s just that different proportions are added under different circumstances.
However, the amount of addition is a technical field, but if the temperature exceeds 1350 ℃, do not add steel fiber, not only does not work. On the contrary, the increase in cost also adds inconvenience to the construction.
The main reasons for the damage of the hot blast furnace include:
The masonry quality is not ideal, and the construction and acceptance are not carried out according to the masonry specifications;
The quality of the high-strength refractory fire castable in the hot blast pipe and the combustion pipe area is defective, which causes the upper brick to fall off The lining falls off;
The hot blast stove is changed frequently, which causes a certain degree of damage to the brick lining;
The operation of the furnace is not standardized, resulting in low-frequency pulsation of gas combustion, forming gas surge combustion, as the combustion capacity increases
Structural cracks occur when the hot blast stove cools down;
The arch roof combustion temperature exceeds the prescribed standard, and the arch roof fire brick lining is exposed to thermal stress and causes denudation;
The hot blast stove oven does not strictly follow The curve is controlled, and the oven effect is not ideal, which affects the life of the hot blast stove;
The daily operation and maintenance of the hot blast stove is not in place, and effective maintenance and repair measures are not taken for the hot blast stove and local redness;
The hot blast stove The failure of the monitoring devices and interlocking facilities of the company led to errors in post operation;
The quality of the tooling equipment and refractory materials required for the hot blast stove was low in the selection and selection of the hot blast stove, which affected the service life of the hot blast stove.
In order to prevent the corrosion of the furnace shell steel plate, acid-resistant paint is selected to protect the hot blast stove vault steel plate in the design. Among them, it is the key to choose a reasonable acid-resistant coating suitable for the use conditions of the hot blast stove. Monitoring method: In the past, two methods were mainly used to detect the temperature of the vault of the hot blast stove. One is to use platinum rhodium-platinum thermocouple to detect the vault temperature of the hot blast stove, which is a contact temperature measurement method, which has the advantage of high accuracy, but there are several defects:
The reaction speed is slow, mainly because of the poor performance of the protection tube
Inconvenient installation and operation of thermocouples;
(3) Short working life, there is a large amount of CO gas in the vault of hot blast stove, and CO is reducible, and it is very easy to corrode the thermocouple, which increases the maintenance cost in the later period. The other is to use a single-band infrared optical fiber to detect the temperature of the vault of the hot blast stove, which is a non-contact temperature measurement method, that is, the temperature is detected by measuring the infrared radiation emitted by the measured object through a temperature probe.
The castable for ladle, in terms of material, was originally based on “Zirconia-Silicon” stone. However, with the requirement of clean steel and the increase of secondary refining, the high-durability alumina spinel is gradually adopted. During this period, tests were also done on magnesia-based alkaline materials, but they were not put into practical use due to the inability to suppress structural peeling. Therefore, in terms of extending the service life of the ladle, understanding the damage mechanism of the castable for the ladle is a very important link. Refractory manufacturers and steel mill customers have conducted a series of studies on the damage pattern of the castable for ladle.
The Damaged Appearance of Castable for Ladle
Regardless of shaped or unshaped refractories for ladle, the slag line, molten steel parts, and the bottom of the ladle will be damaged to varying degrees.
Damage to the slag line
At the position equivalent to the “slag-steel” interface, the damaged surface is smooth and deep with a clear outline. The reason for making it smooth is that the damage is mainly corrosion, but there are also cracks. Recently, due to the use of alumina spinel castables, satisfactory durability has not been obtained. Therefore, magnesia carbon bricks are mostly used. The damage rate is 1~2mm/furnace, and it needs to be repaired after about 100 furnaces are poured.
Damage to the molten steel
The corrosion damage is very small under the current materials and uses conditions, and the cracks and the peeling caused by their expansion are the main damages. Repeated peeling affects the life span. On average, the damage rate of “zirconium-silica” stone is 1 mm/furnace, and alumina spinel is 0.3~0.5mm/furnace. Now the most durable alumina spinel has a life span of 250 to 300 furnaces. Since the molten steel part is the main part that determines the life of the ladle, the damage of this part needs to be paid attention to.
The bottom of the package is damaged by the steel part
Due to the impact of molten steel, the steel parts during pouring steel wear and then develop into cracks, where molten steel penetrates to affect the service life. Use alumina castable prefabricated block, which needs to be repaired after about 100 times of pouring.
Damage Patterns of Refractory Materials for Ladle
The characteristics of the damage of the castable are that although there is no damage to the brick joints, cracks of varying sizes and seldom occur hot spalling instead. The damage of ladle castables is also the same as before, which can be divided into the following three aspects.
Corrosion, continuous loss caused by surface or internal melting.
Mechanical wear, loss caused by the impact of molten steel, etc.
Spalling, falling of refractory lining caused by high temperature, machinery, structure, etc.
It is rare that corrosion is the main factor in molten steel. At the part of the molten steel where the working face is spalled in layers, the structural spalling caused by slag penetration, that is, the cracking caused by the structural thermal stress is the main cause of damage. However, for alkaline materials and some alumina spinel castables, cracks also occurred in the original layer, and thermal spalling occurred, mainly due to the cracks caused by the concentration of thermal stress.
The temperature of molten steel, the composition of slag, and the residence time of molten steel have a great influence on the damage of refractory materials. After discovering the damage of the refractory layer of the ladle, the analysis of the related damage mechanism will be of great help to prolong the service life of the ladle. To purchase refractory castable for ladle, please contact the refractory castable manufacturer.
With the increase in the use temperature and service life of various high-temperature kilns and thermal equipment, refractory castables are widely used in production and use as unshaped refractory materials. In the modern era of rapid industrial technology, there are many types of refractory castables. Compared with refractory bricks, the advantages of using refractory castables are simple to process, energy-saving, low cost, and easy mechanized construction. It has been widely used in various types of thermal equipment such as cement, steel, glass, and electric power. As a result, the use of refractory castables in high-temperature kilns often encounters some problems. Experienced unshaped refractory castable manufacturers will take you to understand these problems and provide you with the most suitable refractory castable lining solution for your production needs.
Question 1: The operating temperature of the kiln is 1500℃, what refractory castable should be used?
When the temperature of the working part of the kiln is 1500℃, corundum castable should be selected according to the use temperature of the refractory castable. Many users do not understand but think that the price is high, so they choose general high-aluminum castables.
However, if the direct use temperature is 1500°C, the general high-aluminum castable is not acceptable. The brown corundum castable must be selected to meet the application requirements. There are also users who propose to use steel fiber castables, which is not acceptable. Because steel fibers begin to melt at temperatures above 1300°C. Therefore, steel fiber castables cannot be used.
However, some customers choose to use stainless steel. The answer given by refractory manufacturers is still no. Because the stainless steel used for the lining only serves as an anchor, it cannot resist high temperature and corrosion. The characteristics of corundum castable are the highest bulk density, lowest apparent porosity, high-temperature resistance, corrosion resistance, and thermal shock resistance. And at 1500℃, the characteristics of corundum castable can be fully reflected. If steel fiber castable is used, it cannot withstand the high temperature of 1500℃. The general high-aluminum castables can be used at a temperature of 1300℃-1400℃.
Refractory castable manufacturers pointed out that if it is a different kiln, the working atmosphere inside the kiln is different and the degree of erosion is different, corundum wear-resistant castable or high-strength wear-resistant castable can also be selected. In this way, it is resistant to both high temperature and corrosion. For example, waste incinerators have low temperatures, but strong corrosion, sometimes with acid and alkali corrosion. At this time, the choice of corundum castable is not acceptable, the temperature is not high, and the corundum cannot be fully used. Wear-resistant castables with clean raw materials can be used to resist acid or alkali corrosion. Moreover, the price is lower than that of corundum castable, and it is also suitable for the special use of incinerators.
In short, no matter what kind of refractory castable is selected, the appropriate refractory castable must be selected according to different kilns, different temperatures, and different degrees of erosion.
Question 2: How much is a ton of corundum steel fiber refractory castable for the rotary kiln?
Corundum steel fiber refractory castable is a high-quality refractory castable. It uses special grade bauxite clinker and sintered corundum as refractory aggregates and admixtures, and calcium aluminate cement as a binder. Unshaped refractory material mixed with a small amount of water reducing agent and a certain proportion of wear-resistant and heat-resistant steel fibers of different sizes and diameters using micro-powder technology. It is castable with good fluidity, high strength, good wear resistance, and good thermal shock resistance.
The corundum steel fiber refractory castable has a good effect. Corundum steel fiber castables with different physical and chemical indicators are used in different industrial furnaces, such as steel-making electric furnaces, tundishes, heating furnaces, rotary kilns, and other thermal equipment. So, how much is a ton of corundum steel fiber refractory castable for the rotary kiln?
Generally, the price of corundum steel fiber castable is about 6,500 yuan per ton. However, there are many factors affecting the price of castables, and the details need to be determined based on the actual kiln situation and the use of castables.
The price of corundum steel fiber castable is a reference factor when customers purchase. But what you pay for is what you pay for. Refractory castables are different from other refractory products. Its quality is not only about the price, but also about the application. The better the effect of the application in high-temperature kilns, the more expensive it is. When purchasing high-quality corundum steel fiber refractory castables, it is best to provide refractory castable manufacturers with the working conditions of the furnace, such as operating temperature and service life. Then the refractory manufacturer will have a technical team to provide corresponding castable solutions to ensure the use of corundum steel fiber castables and calculate the cost of purchasing refractory castables.
To learn more about refractory castables for furnace refractory linings, please continue to follow our blog. For the price of high-quality refractory castables, please contact us.
In the refractory industry, it is well known that steel fiber castables are prepared by adding stainless steel heat-resistant fibers. In addition to the conventional high-temperature abrasion resistance, the product has a certain amount of heat-resistant stainless steel fiber added to its ingredients to prevent the difference between the aggregate and the matrix in the material at high temperatures.
(2) Castables of the same material. Castables reinforced with steel fiber will drop corners after 19 cycles of water cooling at 1100°C, while castables without steel fiber reinforcement will drop corners after 14 cycles. Excellent, which proves that steel fiber reinforcement can improve the thermal shock resistance of the castable.
(3) Steel fiber reinforced refractory castables can still bear the load even after cracking, thereby improving the fracture resistance of the castable and increasing the strength of the refractory castable.
The Main Application of Steel Fiber Castable
Which furnace parts are suitable for steel fiber refractory castables? Refractory manufacturers have compiled the following furnace parts for your reference.
Steel fiber reinforced castable is made of special grade bauxite clinker as aggregate, and high-quality bauxite clinker and corundum fine powder as matrix. It is made of superfine powder and other composite materials as binders and additives, plus stainless steel heat-resistant fibers. At the same time, due to the addition of steel fibers, the overall strength of the furnace wall is greatly enhanced after the material is poured. Steel fiber castables are mainly used in the following areas:
The inner lining of various thermal equipment.
The flue, heat insulation in the large-diameter metal chimney.
Industrial boiler lining, the effect is more obvious when used on the top of the furnace.
Low-temperature air (≤1200℃) heat insulation in the pipeline.
KT-J anti-carburizing fiber castable is used for muffle-free carburizing furnace lining.
Various general and special-shaped prefabs can meet the special application requirements of users.
Backing insulation layer (including furnace wall and furnace roof) with a variety of low-temperature furnace interface temperature ≤1050℃.
In industrial furnaces with flat flame burners, the roof of the furnace is sealed and insulated, and the sealing effect is better than any other materials.
Resistance furnace lining with task temperature ≤1200℃, the electric heating element can be exposed, and it can also be made into an embedded structure.
There is no mechanical vibration in the task, and the furnace lining with large temperature changes is especially suitable. Such as bell-type furnace, removable aluminum melting furnace cover, etc.
HS-J ultra-low temperature refractory fiber castable, ML-J polycrystalline mullite fiber castable, L80-J alumina fiber castable. It can be used for the lining of industrial furnaces with a task temperature of 1300-1450°C.
All kinds of fuel furnace lining with task temperature ≤ 1250℃, including furnace wall and roof. Different types of refractory fiber castables are used to make composite furnace linings, with fluctuating structure, economical and reasonable, and convenient construction.
Performance and Formula of Steel Fiber Refractory Castable
The heat-resistant steel fiber used for common steel fiber refractory castables should be selected according to the use conditions of thermal equipment, and the appropriate amount should be determined. The preparation process as follows. First, weigh the refractory aggregates, powders, binders, and additives, dry mix 1mim, and then mix with water and wet, and evenly sprinkle the steel fibers into the material without forming agglomerates. After mixing for 1 min, the material can be discharged. The total mixing time shall not be less than 5 minutes. When vibrating rods are used for molding, the vibration direction should be staggered, so that the steel fiber distribution direction is reasonable and performance can be improved.
No. 1 is high-strength clay combined with refractory castable. The refractory aggregate and powder are made of third-grade and first-grade bauxite clinker respectively. In order to improve the performance of the matrix, fused brown corundum powder is added, and active SiO2 ultrafine powder and additives are added. Use CA-50 cement as coagulant.
No. 2 is fused calcium aluminate cement aluminum-magnesium refractory castable, dense fused corundum is aggregate, alumina and high-purity sintered magnesia powder are used as refractory powder, and superfine powder and compound additives are added at the same time.
No. 3 and No. 4 are low cement bauxite-mullite refractory castables, and refractory aggregates are made of first-grade bauxite clinker and mullite. The refractory powder is super-grade bauxite clinker powder or corundum powder, the binder is CA-70 cement, and superfine powder and composite admixtures are added at the same time.
No. 5 is a low cement, special alumina corundum refractory castable with a small number of additives. This type of high-quality refractory castable is used at higher temperatures, so the grade 330 heat-resistant steel fiber is selected. The equivalent diameter is 0.5mm, the length is 20mm, and the dosage is 2%. The water consumption is 6% ~7%. According to the selected mixing ratio, various raw materials are weighed and formed after kneading. After molding, it should be naturally cured and no water should be sprayed. After 24 hours of curing, remove the mold and continue natural curing for another 48 hours to check the performance.
With the development of unshaped refractory castables, prefabricated products of steel fiber refractory castables are also used in kiln parts. The information on this will be sorted out before sharing it with you.
Unshaped refractory castables and castable preforms have been widely used by more and more high-temperature industrial kilns due to their advantages of convenient, fast construction and low labor intensity. However, many enterprise users have found that refractory castables or preforms have found some abnormal phenomena during storage or maintenance, such as chalking, white hairs, and so on. So, how to solve the white hair and chalking on the surface of refractory castables preforms?
Firstly, let’s understand how these phenomena are formed.
In fact, these are caused by the contact of high-alumina cement hydration products in refractory castables with acid gases in the atmosphere. As the moisture in the castable evaporates, salt substances continue to migrate and precipitate to the surface, and then slowly aggravate the damage process of the refractory castable. We will analyze these phenomena today. Pulverization occurs during the storage of preforms made of cement-containing refractory castables. Some of them grow “white hair” on the surface, commonly known as white alkali, which causes the pulverization of the surface of the castable. In severe cases, the strength of the castable decreases.
Several Phenomena on the Surface of Refractory Castables after Construction
Carbonation of Castables
Carbonation of high-alumina refractory castables is often considered to be one of the main reasons that lead to the decrease of castable structure and spalling. The high-alumina cement-bonded refractory castable is exposed to the air, and the hydration products therein react with the CO2 gas in the air to undergo a carbonation reaction. In addition, refractory castables are more likely to undergo carbonation under high humidity conditions and compared with dense castables, lightweight castables with high water content are easier to pulverize. This shows that in the presence of water, the hydration product interacts with the CO2 acid gas, and the PH value of the liquid in the single pore of the phase drops sharply, which makes all the new hydration organisms in the refractory castable become unstable.
Sulfation of Castables
Compared with the carbonation of high-alumina cement hydration products, the sulfation phenomenon has not attracted enough attention from the construction party and the user. In the atmosphere, in addition to the CO2 acid gas, there are also SO2, H2S, and other gases, which also have a strong corrosive effect on the hydration products of the matrix part of the high alumina cement castable. Eventually, this lead to powdering and peeling of the castable.
In addition to being sulphated by SO2 and H2S in the air, high-alumina cement hydrate may also interact with SO42- or H+ in the water source. As the activity and acidity of the two increase, the stability of the three high-alumina cement hydration products also decreases sharply.
Salt Precipitation Phenomenon of Castable
The salt precipitation phenomenon on the surface of refractory castables is another important factor that aggravates the structural damage of the castables. During the curing or natural drying process of refractory castable, some soluble carbonate, sulfate, chloride, phosphate, and other salt compounds will focus on the surface of refractory castable and crystallize with the evaporation of water. This phenomenon is often called salting out.
As the water evaporates from the surface of the refractory castable, these ions migrate and aggregate with the water molecules from the inside to the surface of the castable, or react with acid gases in the air on the surface of the castable. The salts formed after the hydrate reaction are focused on the surface. Finally, these salt compounds crystallized out due to exceeding the solubility in water.
In fact, all soluble salts containing crystal water include chloride, sulfate, carbonate, and so on. These salts all have the process of removing the crystal water, accompanied by the change of crystal form and volume change. These are some of the reasons that aggravate the pulverization, peeling, and lumps of the surface structure when the castable is cured in the air.
Solutions to the Phenomenon after the Construction of Refractory Castables and Preforms
(1) Dry the castable as soon as possible after construction to remove water and eliminate the carrier of sodium salt in the cast, so that the alkali stays in the construction body and no longer migrates to the surface.
(2) If the construction conditions cannot be dried in time, the pouring material should be sealed and the surface should be covered with plastic film to prevent moisture from migrating to the surface with alkali.
(3) The refractory castable is made of refractory raw materials with low alkali content to increase the viscosity and fast hardening of the refractory castable. It can reduce the migration speed of sodium salt, strengthen quality management, and strictly control the amount of water added to the construction.
Rongsheng is a refractory manufacturer with an environmentally-friendly and advanced unshaped refractory production line. Rongsheng’s unshaped refractory production line has an annual output of 80,000 tons. Our refractory products have been sold to more than 60 countries and regions all over the world. Our customers of refractory castables have a high degree of recognition of our product quality and a high rate of return orders. Our monolithic refractory products can be customized according to the customer’s specific furnace requirements. We have rich experience in the field of wear-resistant refractory castables and refractory plastic products. In addition, he has rich experience in prefabricated refractory castables on the roof of the furnace. For more information about monolithic refractories, please contact us.
Ladle castables are used in steelmaking plants and foundries to receive molten steel and carry outpouring operations in front of open-hearth, electric furnace, or converter. Ladle castable is a kind of granular and powdery material made of refractory materials and a certain amount of binder for a ladle. Ladle castable is an unshaped refractory made of high alumina bauxite, corundum, and magnesia as the main materials, using composite micro powder and adding some additives.
Ladle castables are made of bauxite clinker, corundum, magnesia, magnesium spinel, and ultrafine powder, etc., with different binders and additives. Its characteristics are strong corrosion resistance, good thermal shock resistance, good volume stability, suitable for medium and small ladle use, and long life. Good explosion-proof performance, high-temperature strength, slag corrosion resistance, and strong erosion resistance.
Al2O3-MgO·Al2O3 Refractory Material for Ladle
Al2O3-MgO·Al2O3 refractory materials are selected for the sidewalls and bottom of the ladle. The most common form is Al2O3-MgO·Al2O3 castables. The design of its chemical composition is mainly to use the eutectic phase region of the MgO·Al2O3-Al2O3 sub-system in the Al2O3-MgO binary system, and the area of MgO about 5%. As shown in Figure 5-26, its Al2O3 content is about 90%.
This castable not only has good corrosion resistance (see Figure 5-27), but also has excellent resistance to slag penetration, as shown in Figure 5-28 and Figure 5-29. Figures 5-27 and 5-29 show that the more spinel is added, the more spinel with high MgO content is added, the better the corrosion resistance. The resistance to slag penetration is preferably 90% Al2O3 spinel castable. This type of Al2O3-MgO-Al2O3 castable has a thin slag layer and fewer nodules during use, which protects the inner refractory material. Therefore, its durability is good.
The ω (MgO) in the spinel used in this type of Al2O3-MgO·Al2O3 castables is 10% to 30%, and ω (Al2O3) is 70% to 90%. The choice of spinel particles in castables is usually determined by test results.
The particle size of MgO·Al2O3 (20% content) has an effect on the infiltration of slag into the Al2O3-MgO·Al2O3 system. This shows that only when MgO·Al2O3 is added in the form of fine powder, the thickness of the slag soaked layer is the smallest. It can be seen that only when MgO·Al2O3 is evenly dispersed in the matrix of the Al2O3-MgO·Al2O3 brick can the slag penetrate into the deep part of the brick more effectively. The relationship between the amount of spinel added and the melt loss index and slag penetration thickness can be obtained for castables containing 10% to 30% MgO·Al2O3. The small thickness of the slag impregnated layer is an important basis for guiding the design formula.
When the mixing amount of spinel is below 20% (mass fraction), fine powder less than 1mm is used. Under this condition, when the amount of spinel added increases, it has the effect of inhibiting slag penetration. When the amount of spinel is greater than 30% (mass fraction), particles larger than 1mm are used. Under these conditions, when the amount of spinel added increases, it has the effect of improving corrosion resistance. The damage of the castable due to structural spalling is much greater than that of Al2O3-C bricks, and the damage rate of the former is 1.3 to 2.5 times that of the latter. Compared with Al2O3-C bricks, the damage rate of castables is reduced by about 30%, showing better results.
At the most severely damaged ladle impact location, the damage rate of Al2O3-C bricks increases with the increase in the ratio of stainless steel to steel. Castable C has the same damage rate and service life as Al2O3-C bricks. When the Al2O3-MgO-Al2O3 series castable containing 20% spinel fine powder is applied to the sidewall of the ladle and the impact part of molten steel, it will not produce cracks and peeling damage during use, and has the characteristics of stability and durability.
The above research results show that the amount of spinel added has an important impact on the performance of aluminum-spinel fired bricks. This kind of fired brick also has the problem that the joints of the bricks are corroded first. To this end, a certain amount of fused magnesia particles can be added to the ingredients to cause residual linear expansion during use. Therefore, the problem of the brick joints being corroded first is prevented, and the service performance of the aluminum-spinel brick can be improved.
In addition, due to the high CaO content of dolomite, it has excellent impurity purification ability. Therefore, the lining of asphalt combined with dolomite bricks is the most economical material for smelting clean steel. The other is to use fired dolomite bricks as lining to produce ultra-low carbon steel.
Rongsheng is an experienced manufacturer of refractory materials. Rongsheng not only sells various refractory brick products to customers all over the world but also provides overall refractory material solutions and refractory materials for various thermal furnace linings. Rongsheng’s advanced fully automatic monolithic refractory production line has an annual output of 80,000 tons. Rongsheng’s best-selling products include various alumina bricks, magnesia bricks, silica bricks, corundum bricks, mullite bricks, thermal insulation bricks, and other refractory brick products. There are also monolithic refractory products such as high-aluminum refractory castables, refractory plastics, refractory ramming materials, and refractory spray coatings. We also provide customers with high-quality refractory bricks and refractory castables for ladle lining. To get the price of Rongsheng refractory materials for free, please contact us. We will provide you with refractory lining materials that best suit your production needs based on your specific furnace conditions.
Many people may wonder whether adding silicon carbide to refractory castables can increase strength? It is well known that adding silicon carbide to refractory castables can increase the strength of the castables. However, the addition of different proportions has different effects on the performance of refractory castables. What are the effects of adding silicon carbide on Refractory Castables Properties? Refractory manufacturers have come to the following conclusions by analyzing experimental data.
What Effects Does the Addition of Silicon Carbide have on the Refractory Castables Properties?
The proportion of silicon carbide added in the refractory castable is too high, which will affect the strength of the castable at medium and low temperatures. Early mulliteification is prone to occur, and the stomata will be relatively reduced. However, the compressive strength of refractory castables increases at high temperatures.
If too little or no silicon carbide is added to the refractory castable, the strength of the castable will decrease by 25%. The current silicon carbide castable is actually a high-strength high-aluminum castable with few silicon carbides. Therefore, the high aluminum castable strength maintained by the castable without silicon carbide.
The addition of silicon carbide to the refractory castable is too low, then it will not play the role of increasing the compressive strength of wear resistance. At this time, judging from its performance, it is just a high-aluminum castable. However, under certain conditions of severe lining erosion, it is still necessary to add silicon carbide to the high-aluminum castable to change the properties of the castable. In order to improve the thermal shock stability and wear resistance coefficient of the refractory castable, the service life of the lining is longer.
Of course, excessive addition of silicon carbide in the refractory castable will react with silicon dioxide, and too little addition will have no effect. How to balance it? Generally, when the furnace is not severely eroded and the erosion is not severe, add 6% silicon carbide to the refractory castable. It is the best balance ratio to use in the strength of semi-finished products or high-temperature areas.
The effect of the amount of silicon carbide added on the apparent porosity of the castable. With the increase in the amount of silicon carbide added, the apparent porosity gradually decreases after heat treatment at 1400 ℃. This shows that as the liquid SiO2 on the surface of silicon carbide increases, more closed pores are formed. At high temperatures, the apparent pores are continuously reduced, and the degree of densification will increase.
The effect of the amount of silicon carbide added on the linear change rate of refractory castables. With the increase of the amount of silicon carbide powder added, the linear rate of heat treatment at 1400℃ gradually decreases. The main reason is that the surface of silicon carbide is oxidized into a liquid SiO2 film at high temperature, showing a trend of increasing volume. This reaction occurs slowly from the outside to the inside, and correspondingly offsets the shrinkage of the substrate. In addition, 1100-1350 ℃ is also the formation stage of mullite. The outer layer of silicon carbide is oxidized to form liquid SiO2, which reacts with alumina powder to form staggered, acicular mullite crystal phases. Accompanied by the larger volume expansion, it compensates for part of the line shrinkage.
The Influence of the Amount of Silicon Carbide Added on the Refractory Castables Properties
The effect of the amount of silicon carbide added on the high-temperature flexural strength of refractory castables. The high-temperature flexural strength of the refractory castable after firing at 1400°C, with the increase of the silicon carbide content, the high-temperature flexural strength is significantly enhanced, and it is much higher than that of the castable without silicon carbide. This is a very significant feature brought by silicon carbide.
When the addition amount of silicon carbide is above 5%, it has good alkali resistance. With the increase of the added amount, the corresponding corrosion resistance and thermal shock resistance can be improved. However, adding a small amount of silicon carbide to the corundum-mullite castable has an effect on the physical properties at room temperature, high-temperature flexural strength, and microstructure. At the same time, trace silicon carbide will not significantly increase the thermal conductivity and heat loss of the castable.
In summary, increasing the content of silicon carbide from 1% to 5% can increase the strength of the refractory castable after heat treatment at 110-1500°C. However, increasing the content of silicon carbide from 5% to 9% will affect the strength of the castable after heat treatment at 1100°C. After the addition of silicon carbide, the wear resistance of the castable is hardly improved after the 110°C treatment; after the 1100°C treatment, the wear resistance of the castable with the silicon carbide content of 1% to 5% is slightly improved. However, the wear resistance of castables with SiC content of 5%-9% is worse.
The production of refractory castables does not go through high temperatures. The reason why the amount of refractory castables is now increased and has a wide range of uses. It is because the production cycle is short and the construction is convenient and quick. The iron parts and special parts of industrial furnace lining can play a better role. Even different manufacturers of refractory castables are constantly experimenting and updating the recipes of castables according to the actual use of customers, so as to better enable the castables to exert their best performance during use. Rongsheng is a refractory castable manufacturer with rich production and sales experience. Rongsheng’s advanced unshaped refractory production line has an annual output of tons. To get the price of refractory castables for free, please contact Rongsheng refractory castable manufacturers.
Refractory castables in cement plants generally use high-alumina wear-resistant castables, steel fiber castables, low-cement castables, corundum castables, alkali-resistant castables, magnesia-chrome spray coatings, phosphate castables, etc. Of course, there are more high-end ones. For example, the castable for coal injection pipes uses alumina-silicon carbide series refractory castables, which is resistant to thermal shock and alkali. In addition, there are corundum-spinel castables, which have good high-temperature flexural strength and alkali resistance. Next, let’s learn more about the performance indicators of commonly used refractory castables in cement plants.
Refractory Castable in Cement Plants for Different Parts
The preheater uses a lower temperature, and generally uses cheaper alkali-resistant castables. The decomposition furnace is prone to skinning and blocking, and anti-skinning castables are generally used. The front and back of the rotary kiln have strong erosion at the mouth of the kiln. Generally, steel fiber castables, kiln mouth castables, and corundum castables are used. The temperature of the kiln door cover is relatively high and there is cold air. Generally, high alumina and low cement castable or steel fiber castable are used. The use conditions of the coal injection pipe are the most demanding, and the special castable for the injection pipe is generally used. When choosing refractory castables for cement plants, you need to look at the life cycle of the refractory castables. No matter how the name and grade of refractory castables change, it is important to meet the production needs of cement kilns. Rongsheng refractory material production and sales manufacturer is specialized in refractory materials for the cement industry. If your cement kiln needs refractory materials, please contact us.
High-strength refractory castables are mainly used for parts that are easy to wear in thermal kilns, such as kiln mouths and coal injection pipes. It is formulated with corundum as aggregate, high-quality high-alumina cement as a binder, and a small number of additives. However, this kind of castable is prone to porosity during the pouring process, and it is easy to peel off during the pouring process, and strong growth is relatively slow. In the process of pouring and subsequent curing, drying, and heating, it should be more careful and delicate. JC498-92 “High-strength Alkali-resistant Castable” stipulates its main physical and chemical performance indicators as follows:
High-strength Alkali-resistant Castable Physical and Chemical Performance Indicators
Al2O3 (%) ≥
SiO2 (%) ≤
CaO (%) ≤
Crushing Strength (MPa) ≥
Flexural Strength (MPa) ≥
Linear Change Rate (%) ≤
Bulk Density after 110 ℃ drying (kg/m3) ≥
Refractoriness (℃) ≥
Note: The initial setting time is not less than 30min and not more than 240min.
Steel fiber-reinforced refractory castables are made of high alumina bauxite clinker or corundum as aggregates and powders, adding binding agent and the appropriate amount of heat-resistant stainless steel fiber, or adding appropriate additives. The proportion of steel fiber in the clinker should be 4% (weight ratio). Steel fiber in the refractory castable greatly improves the anti-stripping performance of the refractory building material. The distribution of steel fibers has a great influence on the quality of concrete, and random distribution is better. Therefore, the time of vibrating should not be too long. The steel fiber castable must be poured at one time, otherwise, the possibility of peeling between the two layers is very high. The physical and chemical performance indicators specified in JC/T499-92 “Steel Fiber Reinforced Refractory Castables” are as follows:
Steel Fiber Reinforced Refractory Castables Physical and Chemical Performance Indicators
Al2O3 (%) ≥
Crushing Strength (MPa) ≥
Flexural Strength (MPa) ≥
Linear Change Rate (%) ≤
Other Refractory Castables
Common refractory castables often have a higher proportion of cement content (10%-15%, weight ratio). But this has caused a series of performance decline of the castable, the reasons are:
In order to completely hydrate the cement, excessive water (10%-15%) is added during mixing, which will increase the porosity of the ceramic refractory castable and decrease the density.
Calcium aluminate hydrate has a strong dehydration and recrystallization effect in the middle-temperature stage, which destroys the structure of the hard spots in the castable, and makes the strength of the refractory castable drop sharply in the middle-temperature stage.
The cementitious binder brings more calcium into the castable, resulting in a decrease in the softening temperature of the ceramicist refractory castable under load and deterioration of thermal shock performance.
In view of the above problems, low cement refractory castables effectively avoid the regret of high-temperature section performance. Refractory castables with a cement content of less than 8% are called low-cement refractory castables; those with a cement content of less than 4% are called ultra-low cement refractory castables. Compared with ordinary refractory castables, its structure is dense, the apparent porosity is low, the refractoriness is high, the high-temperature strength is high, the load softening temperature is high, and the thermal shock performance is good. However, due to the low cement content, the setting time is long and the early strength is low, which is particularly disadvantageous for construction in winter and low-temperature conditions.
Chinese refractory materials companies have found in experimental research that adding a small amount of inactive powder (silica fume or Al2O3) below 5 microns into the castable can fill and lubricate the refractory, and can effectively reduce water consumption and increase the castable. The masonry is dense, thereby increasing the strength and resistance to chemical erosion. The low cement refractory casting performance indicators are as follows:
Rongsheng refractory castable manufacturer has an advanced and fully automatic unshaped refractory production line with an annual output of 80,000 tons. Rongsheng’s unshaped refractory products include high-aluminum refractory castables, wear-resistant castables, wear-resistant plastics, and anti-skinning castables. It can be applied to a variety of thermal kiln equipment, such as ladle lining, heating furnace lining, cement kiln lining, etc. It is widely used in steel, metallurgy, non-ferrous, chemical, and other industries. If you need to buy refractory castables, get the price of Refractory Castables in Cement Plants, please contact us. We will provide you with services according to your specific needs.