How to Select the Right Castable Refractory for Your Furnace Needs?

Castable refractory is a crucial component of furnace construction, serving as a heat-resistant lining that helps to protect the surrounding environment from the extreme temperatures generated within. Selecting the right castable refractory for your furnace needs is therefore a critical decision that requires careful consideration of several key factors. In this essay, we will explore some of the most important considerations to keep in mind when selecting castable refractories for your furnace.

high-alumina castables for your furnace lining

One of the first things to consider when selecting castable refractory for your furnace is the operating temperature range. Different types of refractory materials are designed to withstand different temperature ranges, and it is important to select a material that is appropriate for your specific application. If your furnace will be operating at extremely high temperatures, for example, you may need to choose a high-alumina castable that can withstand temperatures of up to 1800°C or higher. On the other hand, if your furnace will be operating at lower temperatures, a lower-grade refractory material may be sufficient.

Another important consideration when selecting castable refractory is the chemical composition of the material. Different types of refractory materials are made from different raw materials and can have varying degrees of chemical resistance to different substances. If your furnace will be used to process chemicals or other corrosive materials, it is important to choose a refractory material that is resistant to the specific substances that will be present in your furnace environment.

In addition to temperature range and chemical resistance, it is also important to consider the physical properties of the castable refractory material. For example, the thermal conductivity of the material can affect the efficiency of your furnace, and choosing a material with a low thermal conductivity can help to improve overall efficiency. Other physical properties to consider include the density, compressive strength, and abrasion resistance of the material, as these can all affect the durability and lifespan of your furnace lining.

Finally, when selecting castable refractories for your furnace, it is important to consider the cost and availability of the material. While high-grade refractory materials may offer superior performance, they may also be more expensive and difficult to source. It is important to balance performance requirements with cost considerations to ensure that you are selecting the most appropriate material for your needs without overspending on unnecessary features.

In conclusion, selecting the right castable refractory for your furnace needs requires careful consideration of several key factors, including temperature range, chemical resistance, physical properties, and cost. By taking these factors into account and working closely with a trusted supplier of refractory materials, you can ensure that you are selecting the most appropriate material for your specific application and that your furnace will perform reliably and efficiently for years to come. Rongsheng Refractory Castable Manufacturer can provide high-quality monolithic refractories for furnace lining. Rongsheng is a powerful manufacturer and seller of refractory materials.

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What Indicators Should be Paid Attention to When Purchasing High Alumina Refractory Castables?

The technical indicators of refractory castables are the main reference in the procurement process. Most buyers use this as a reference. The index of refractory castable determines the performance of refractory castable and affects the service life of the refractory lining. There are 7 main technical indicators of refractory castables, namely A2O3 content, bulk density, apparent porosity, compressive strength at room temperature, softening temperature under load, and thermal shock stability. Rongsheng refractory castable manufacturer takes high alumina refractory castable as an example to analyze what indicators should be paid attention to when purchasing high alumina refractory castable?

Rongsheng High-Alumina Castables

1. The content of AI2O3

The content of Al2O3 in high alumina castables, the popular point is the content of aluminum oxide in high alumina castables. It determines the performance of high aluminum castables. Therefore, it is the main performance index of high alumina castables.

2. Bulk density

Bulk density is the ratio of the dry mass of the high-alumina castable to its total volume, and the unit is g/cm3. The bulk density mainly indicates the compactness of the high-alumina castable. Generally, the bulk density of high alumina castables has a great relationship with its porosity and mineral composition.

3. Room temperature flexural strength

The room temperature flexural strength is the maximum bending stress that the bar-shaped test block made of high-alumina castable can withstand in the test. The chemical composition, mineral composition, organizational structure, production process, etc. of the material have a decisive influence on the flexural strength of the material, especially the high-temperature flexural strength. Usually, high-purity raw materials are selected, reasonable particle gradation of materials is controlled, molding pressure is increased, high-quality binders are used, and the sintering degree of products is improved to improve the flexural strength of materials.

4. Compressive strength at room temperature

Compressive strength refers to the ultimate load that a high-alumina castable(https://refractorycastablecement.com/high-alumina-castable-refractory/) construction body can withstand per unit area without being damaged at a certain temperature. The compressive strength at room temperature can indicate the sintering condition of the material and the properties related to its structure. In addition, other properties, such as wear resistance and impact resistance, can be judged indirectly through the normal temperature compressive strength.

5. Load softening temperature

The load softening temperature of high alumina castables refers to the temperature at which deformation occurs during use. The load softening temperature indicates the ability of the refractory to resist both high temperature and load. To a certain extent, it shows the structural strength of the product under similar service conditions.

6. Alkali resistance

High alumina castables for cement kilns are often eroded by alkaline gas in the kiln. Therefore, it is very necessary to test the alkali resistance of the material. Alkali resistance is the ability of refractory castables to resist alkaline erosion at high temperatures.

The above is the key to the technical performance indicators of high-alumina castables. When purchasing and using high-alumina castables, they must be selected in strict accordance with the actual kiln usage requirements. Only in this way can the service life be extended and maintenance costs saved on the premise of ensuring the service life of the high-alumina castable. Rongsheng refractory castable manufacturers provide free samples and solutions for refractory lining materials. If you need, please contact.

Fluidity and Influencing Factors of High Alumina Self-flowing Castable

High-alumina self-flowing castable is a new type of refractory material, which has obvious advantages compared with ordinary high-alumina refractory castables. It not only inherits the high density, good fire resistance, corrosion resistance, and wear resistance of low cement castable. Moreover, it can flow and solidify by itself during construction and does not require vibration equipment. At the same time, self-flowing materials will be widely used in other industrial kilns due to their excellent construction performance, such as heating furnaces, soaking furnaces, rotary kiln coolers, nozzles, etc. Its service life will be twice that of traditional castables. So, why is the fluidity of high-alumina self-flowing castables so good? And what are the factors that affect the fluidity of high aluminum self-flowing castables?

Self-Flowing Refractory Castable for Sale

What is the fluidity of high alumina self-flowing castable?

Self-flowing castables are characterized by good fluidity after mixing. In order to assess its flowability, it is necessary to measure the self-flow value on a material flow bench. We use self-made instruments to simulate actual construction conditions to measure flow values. The experimental method is as follows, the empty conical mold is placed on the flat plate, and then the mixed self-flowing material is poured into the mold. After the material is full, scrape off the material beyond the upper mouth of the mold, and then lift the cone mold vertically to allow the material to flow automatically on the flat plate.

By calculating the self-flow value to reflect the self-flow performance of the castable. This can measure whether the self-flowing material has proper construction performance and stable physical properties. The self-flow value is small, the fluidity of the material is poor, and dense filling cannot be achieved during the construction process. If the self-flow value is too large, serious particle segregation will occur in the material during construction. Refractory castable manufacturers believe that the self-flow value should be within 50-100%, preferably around 80%.

High-Alumina Self-Flowing Castable Refractory

What are the factors affecting the fluidity of high aluminum self-flowing castables?

1. The amount of water to be added.

Self-flowing castables are particularly sensitive to the amount of water added. If the amount of water added is insufficient, the self-flow value is too small, the material cannot flow and fill normally, and the air bubbles cannot be discharged. Too much water can cause the aggregate to sink, causing the aggregate to separate from the matrix. And too much water can compromise the material’s density and strength, as well as its corrosion and wear resistance.

2. Particle gradation.

Raw materials: (1) Aggregate: super grade alum. (2) Powder: special-grade alum clay powder, uf-SiO2, pure calcium aluminate cement, α-Al2O3 micro powder. Through experiments, the relationship between fluidity and particle gradation is clarified.

The fluidity of the self-flowing castable comes from the cement slurry. Some have a lot of mud and good fluidity, but too much powder requires a lot of water, so it is beneficial to increase the particle composition of 1~0mm. It can be seen from the experiment that >1mm when the particle composition is 50% larger, it is difficult to obtain better fluidity. The research results show that the particle size composition range has good fluidity: >1mm35~50%, 1~0mm15~30%, <0.088mm35~50%.

3. Coarse particle size and critical particle size distribution.

In the case of gradation: >1mm40%, 1-0mm20%, <0.088mm40%, from the influence of the thickness ratio of aggregate on fluidity, it can be seen that the amount of coarse grain is large and the fluidity is good. Some people say that the critical particle size is controlled at 5mm. Experiments show that the conclusion is just the opposite. Theoretically speaking, the larger the particles in the >1mm component, the smaller the specific surface, the smaller the contact area with the mud, the smaller the flow resistance, and the better the fluidity.

4. The impact of cement.

The self-flow increases with the increase in cement consumption, the water demand increases, and the fluidity are poor, which is not conducive to high-temperature strength. On the other hand, the amount of cement is too small, and the temperature and strength are low, so the amount of cement should be around 5%. The mineral composition of cement will also have a certain influence on the fluidity of self-flowing materials. For example, when pure calcium aluminate cement and alum cement are used as binders, the ratio of water reducer and dispersant should be adjusted.

High Temperature Castable Refractory Materials for Sale Supplier

What are high-temperature castable refractory materials? Unshaped refractory material is one of the important basic materials in the application of high-temperature furnace industrial refractory lining technology. High-temperature castable refractory materials, refractory castables are an important type of unshaped refractory materials. Its important feature is that the supply cycle is short and it is not limited by the shape of the equipment. A refractory material that can be used directly without pre-calcined, loose mixture and suitable anchors after on-site forming and baking. Refractory castables can be used to make seamless linings, also known as integral refractories. Over the years, amorphous refractories such as high alumina castables, high alumina low cement castables, steel fiber wear-resistant castables, and corundum castables have been widely used in lining design of cement kilns. The refractory layer of thermal equipment is widely used in different parts.

Rongsheng High-Temperature Castable Refractory Materials Plant

High-temperature Compressive Strength of Common Refractory Castables

The high-temperature compressive strength refers to the ultimate stress when the sample is damaged by the pressure load under the specified high-temperature state. It is the basis for evaluating the wear resistance, slag resistance, and spalling resistance of amorphous refractories. It is also the basis for selecting high-temperature castable refractory materials and their application parts.

When the heating temperature is below 800 ℃, the amorphous refractory sample is in the stage of elastic deformation, and its high-temperature compressive strength is generally similar to or slightly lower than the compressive strength after burning. When the temperature is higher than 800 °C, the sample is in the plastic deformation stage, so the high-temperature compressive strength gradually decreases with the increase of the heating temperature. When it reaches 1400℃, it is only 1~10MPa. Experiments show that the high-temperature compressive strength of refractory castables and the high-temperature compressive strength of clay combined refractory castables are better than those of other materials, and the temperature strength is better.

How Much is a Ton of High-Temperature Refractory Castable?

How much is a ton of high-temperature refractory castable? High-temperature refractory castable is an unshaped refractory material for high-temperature kilns, and it is also a kind of unshaped refractory material. The price of high-temperature refractory castable is directly related to the refractory raw materials used. Commonly, refractory castables can be used for the casting of blast furnace linings. High-temperature refractory castables come in a variety of materials and specifications, such as clay castables, high alumina castables, mullite castables, corundum castables, steel fiber castables, and more.

Refractory castables of different materials are used in different high-temperature environments, so the prices of high-temperature refractory castables are also different. Before understanding the price of high-temperature refractory castables, first understand the working environment and temperature of the high-temperature kiln, the performance of the kiln on the lining, service life, and other factors, and then choose the appropriate high-temperature refractory castable.

The high-temperature refractory castable is convenient for construction and can be poured according to the application site, and its constructability is better than that of refractory brick masonry. High-temperature refractory castables can be used in various high-temperature thermal kiln equipment, such as blast furnaces, hot blast stoves, electric furnaces, converters, heating furnaces, rotary kilns, shaft kilns, etc.

According to the high-temperature kiln environment and use location, selecting the appropriate high-temperature refractory castable to cast the lining can make the kiln run longer. There are many materials of high-temperature refractory castables. Taking common high-aluminum and high-temperature refractory castables as an example, the price of ordinary high-temperature refractory castables is generally around 2,300 yuan. For specific price information, the price of castables needs to be determined according to the physical and chemical indicators of high-alumina refractory castables and the use environment.

The prices of high-temperature refractory castables in this article are for reference only. When purchasing castables, various considerations should be taken, and the construction effect and use effect must be ensured to ensure the normal operation of the kiln.

Buy Calcium Aluminate Cement Castable Refractory Lining Sales from Factory

Buy medium and low-grade refractory castables. Sales of refractory castables, such as clay, high alumina, and other castables, use ordinary calcium aluminate cement as a binder. High-grade refractory castables, such as corundum refractory castables, mullite refractory castables, chromium-containing corundum refractory castables, corundum-spinel refractory castables, and other castables, using pure calcium aluminate cement as a binder. The addition amount of calcium aluminate cement for ordinary refractory castables is 10%~20%, the addition amount of low cement refractory castables is 5%~7%, and the addition amount of ultra-low cement castables is less than 3%.

High-Alumina Castables Calcium Aluminate Cement Castable

Calcium acid cement is mainly used as a binder for refractory castables and refractory injection materials. There are two main requirements for ordinary calcium aluminate cement:

• (1) Appropriate setting time to ensure sufficient working time. Generally, the initial setting is more than 1h, and the final setting is less than 8h. The shorter the time interval between the initial setting and the final setting, the better.
• (2) Sufficient early strength. That is, it can reach 60%~70% of the strength specified by the cement label in one day of curing, and it can reach more than 90% in three days.

In addition to the above two points, pure calcium aluminate cement is also required to have a certain degree of refractoriness and good workability to meet construction requirements and high-temperature use requirements. Buy Pure Calcium Aluminate Cement Castable low cement: https://refractorycastablecement.com/buy-low-cement-refractory-castable/.

Corundum High Strength Wear Resistant Castable

Buy Calcium Aluminate Cement Castable Refractory Lining Sales from Factory. Among unshaped refractories, castables with calcium aluminate cement as binders are widely used.

• (1) The use temperature of clay castables is 1300-1450 degrees. Generally used as the lining of steel rolling heating furnaces, various heat treatment furnaces, boilers, shaft kilns, and rotary kiln preheating zone.
• (2) The use temperature of high-alumina castables is 1400-1550 degrees. Can be used for various heat treatment furnace linings and burners. Electric furnace tapping groove, a high-temperature section of lime shaft kiln, rotary kiln head, power plant boiler lining.
• (3) The use temperature of corundum castables is 1500-1650 degrees. Mainly used for the lining of various high-temperature furnaces and high-temperature components. The dip tube of the molten steel vacuum degassing device, the lining body of the spray metallurgy and the argon blowing integral spray gun, the lining body of the triangular area of the electric furnace top, and the LF furnace cover. High-temperature wear-resistant lining body of catalytic cracking reactor in the petrochemical industry, etc.

A mixture prepared with ordinary calcium aluminate cement as a binder and refractory aggregate and powder in a certain proportion and in a certain proportion can be used directly after mixing with water, vibrating casting, curing, and baking. Ordinary calcium aluminate cement is divided into the low iron type and high iron type. The low-iron type produced in my country is sintered with natural low-silicon bauxite and limestone.

The castables combined with ordinary calcium aluminate cement have a wide range of applications. Different types of calcium aluminate cement can be selected as binders according to the use temperature and use conditions, and different refractory aggregates and powders can be added. It is usually used in various heat treatment furnaces, heating furnaces, soaking furnaces, tapping and tapping grooves, boilers, rotary kiln heads, and kiln tails in metallurgy, petrochemical, machinery, building materials, and other industrial sectors. The lining of petrochemical reactors and various heat pipes and valves, etc. Buy Low Cement Refractory Castable – Refractory Castable Cement Sales:  Sales@refractorycastablecement.com.

The Use Conditions and Raw Materials Selection of the Ladle Castable

The use conditions and raw material selection of the refractory castable in the impact zone of the ladle.

The ladle is an important thermal equipment in the steelmaking system. The inner lining of the ladle bears the erosion and impact of molten steel and molten slag for a long time. With the continuous progress of steelmaking technology, the proportion of refined steel has been increasing, which puts forward higher and higher requirements for the performance of refractory materials in the ladle. Because it directly affects the life of the ladle and the stability of production. Years of application practice have shown that the most economical use of ladle is to match materials reasonably according to the different use requirements of each part. In order to synchronize the life of each part of the ladle, reduce the number of minor and intermediate repairs.

Steel Ladle

The Use Conditions and Requirements of the Castable in the Impact Zone of the Ladle

• The temperature of molten steel. The tapping temperature of the converter is 1650℃~1680℃.
• Directly bear the impact of molten steel in the converter. The ladle contains 95t~105t of steel, the molten steel has a drop of about 5m, and each ladle has an assessment of 70 times.
• The residence time of molten steel in the ordinary ladle, including pouring time, is about 60 minutes/time.

It can be seen that the castable in the impact zone of the bottom of the ladle should have high refractoriness, high thermal strength, excellent thermal shock resistance, slag resistance, and corrosion resistance of molten steel. Therefore, its service life should be synchronized with the ladle wall.

Selection of Raw Materials for Ladle Castables

The raw material of ladle castable (https://refractorycastablecement.com/refractory-castable-manufacturer/steel-ladle-castable/) is generally high alumina spinel, which is proved to be suitable after years of actual application experience. Relevant studies have shown that the reaction of Al2O3 and MgO to produce spinel has a large volume expansion, adding an appropriate amount of pre-synthesized spinel to the matrix can reduce excessive expansion and promote sintering. And when the spinel is added in the form of a fine powder, it can absorb a large amount of iron oxide in the slag, solidify the iron oxide, and slow down the penetration of the slag. In addition, by adding Al2O3 fine powder to the matrix ingredients, on the one hand, a mineral phase in which spinel and corundum coexist is formed in the matrix; on the other hand, the CaO in the slag and the Al2O3 in the fine powder form needles to make the pores finer. Both of these factors can inhibit the penetration of slag, thereby improving the corrosion resistance of the castable.

In summary, we can make the system highly purified and improve the material quality without greatly changing the material system of the castable. Some high-alumina materials are replaced by corundum, and sintered magnesia is replaced by fused magnesia, the addition of fine powder is optimized, and fine powder of fused corundum and spinel with an average particle size of less than 5μ is introduced.

In addition, adding an appropriate amount of industrial Cr2O3 as a modifier can supplement the lattice defects of Al2O3 and activate the Al2O3 lattice. Because Cr2O3 and Al2O3 and other oxides form an infinite solid solution or a compound with a high melting point at high temperatures, it has a small thermal expansion value. At the same time, the addition of Cr2O3 promotes the absorption of iron by the spinel and increases the viscosity of the slag. When it is evenly distributed in the material matrix, the high-temperature performance and corrosion resistance of the material can be improved.

To purchase high-quality refractory castables for ladle, please choose refractory manufacturers. A strong refractory castable manufacturer not only has advanced production equipment but also high-quality refractory castable products. And provide comprehensive customer service, including the customization of ladle refractory castable lining scheme, refractory castable sample service, and after-sales service. Look forward to receiving your email.

What are the Characteristics and Classifications of Lightweight Thermal Insulating Castables?

Lightweight insulating castables are made of aluminate cement, high-alumina fine materials, and ceramsite, plus a number of additives. The product has light volume, high compressive strength, acid and acid gas corrosion resistance. Through the introduction of unshaped refractory castable manufacturers, after we have a certain understanding of refractory castables and lightweight refractory castables, we can clearly know the characteristics and classification of lightweight thermal insulating castables.

Lightweight Insulating Castable

Technical Characteristics and Application of Lightweight Thermal Insulating Castable Refractory

Lightweight heat-resistant Insulating castable refractory is characterized by heat preservation, heat resistance, and energy saving. The main reason is the low thermal conductivity of the lightweight heat-resistant insulating castable. Generally, in the kilns and thermal equipment of the metallurgical, petrochemical, electric power, and building materials industries, more lightweight heat-resistant insulating castables are used, but they are all used for insulation construction. But there are also some lightweight castables that can be used as working layers or load-bearing components, all of which have better results. Moreover, only the parts in contact with the liquid metal or molten slag use an insulating board on the tundish, and the good effect is confirmed.

In the current situation where energy is very scarce, saving energy is the most important thing to pay attention to. The lightweight heat-resistant Insulating castable refractory has the characteristics of energy-saving and heat resistance. The lightweight thermal insulation castable has good thermal insulation performance due to its low volume density and low thermal conductivity. In addition, there are many types of lightweight heat-resistant heat-insulating castables, but lightweight heat-resistant castables are generally chosen as the thermal insulation layer for industrial kiln construction. The reason is that the lightweight, heat-resistant and heat-insulating castable has low refractoriness. The general operating temperature is 600~900℃, which is more suitable for boiler construction below 1000℃.

Lightweight Refractory Castable from RS Factory

Classification of Lightweight Castable Refractory

Lightweight castable refractories can be divided into the following three categories according to the use temperature.

1. Low-temperature lightweight refractory castable. The use temperature of low-temperature lightweight refractory castables is below 900℃. Expanded vermiculite, expanded perlite, ceramsite, etc. are often used as aggregates. Use ordinary Portland cement, alumina cement, or water glass as the binder.
2. Medium temperature light refractory castable. The use temperature of medium-temperature insulating castables is 900-1200℃. Generally, porous clay particles, clay ceramsite, shale ceramsite, etc. are used as aggregates. Use alumina cement, calcium aluminate cement, or aluminum dihydrogen phosphate as the binder.
3. High temperature light refractory castable. The use temperature of high temperature light refractory castable is higher than 1200℃. This refractory castable uses corundum, high alumina, mullite, clay, magnesia, magnesia spinel, and other lightweight particles or hollow spheres as aggregates. The combination system is calcium aluminate cement, aluminum dihydrogen phosphate, silica sol, aluminum sol, and silica powder.

Compared with other monolithic refractories, lightweight insulating castables have a higher binder and moisture content and better fluidity, so they have a wider range of applications. It can be used in petroleum, chemical, non-ferrous metallurgy, and other industries. The material and bonding agent used can be selected according to the conditions of use. It can be directly poured into a lining body for use, and can also be used as a prefabricated block by pouring or vibrating method.

For more product information about thermal insulation castables, please follow our blog. Or get a free quote for insulating castables (https://refractorycastablecement.com/insulating-castable/ ).

How to Distinguish the Quality of High-Aluminum Castables?

There are many types of high-aluminum castables. It is necessary to choose high-aluminum refractory castables of different quality when used under different linings and different temperatures and erosion conditions. So, how can we distinguish the quality of high-aluminum castables?

High-Alumina Refractory Castables

• First, distinguish the grade of the material from the aluminum content. The higher the aluminum content, the better the quality of the castable. If it exceeds the quality of refractory castable and contains 80% aluminum content, it is called corundum castable. Under normal circumstances, high alumina castables have 55%, 60%, 65%, 70%, 75% alumina content.
• Secondly, it is distinguished from the bulk density. The higher the bulk density, the denser the castable and the better the quality.
• Then, it is distinguished from the flexural strength at room temperature. Flexural resistance is a measure of the degree of bending that the castable can withstand. The higher the flexural resistance, the better the performance of the material.
• Also, it is distinguished from the compressive strength. Compressive strength is the ultimate load that the castable can withstand without being destroyed. The greater the strength, the stronger the wear resistance and impact resistance.
• It can also be distinguished from the softening temperature under load. The load softening temperature is the ability of the castable to resist the effects of both high temperature and load. Therefore, the load softening temperature can best explain the quality of the castable.
• From other aspects, we can also distinguish the grade and quality of high-aluminum castables, such as alkali resistance and wear resistance. The high-aluminum castable used in cement rotary kilns and boiler walls will be eroded by alkaline gas or flue gas in the kiln. Therefore, when purchasing high-aluminum castables, it is necessary to test the alkali resistance and wear resistance of the castables. Alkali resistance and abrasion resistance are the ability of castables to resist alkaline erosion at high temperatures.

In short, no matter from the above aspect to distinguish the quality of the high alumina refractory castables. During use, if poor quality castables are selected under high-temperature conditions, the life cycle of the furnace lining will be affected, causing the trouble of replacing the furnace lining back and forth. If the temperature is low, choosing high-quality high-aluminum castables will not only increase the use cost of the furnace lining but also may not necessarily receive a good use effect. Regarding how to choose high-quality high-aluminum refractory castables, it is still necessary to choose the quality grade of the castables according to the use of their own furnace lining.

To purchase high-alumina refractory castables, please choose refractory castables manufacturers. A strong refractory castable manufacturer not only guarantees product quality but also provides comprehensive customer service. Powerful manufacturers of refractory materials have their own advantages in the types and formulations of refractory castables and can customize solutions for refractory castable refractory linings according to their production needs. To learn more about the product knowledge of monolithic refractory linings, please continue to pay attention to our blog.

What are the Selection Techniques for Using Refractory Castables?

With the increasing use of refractory castables, how to choose suitable materials or refractory castables with certain special properties for refractory linings requires certain methods and skills.

Construction of Castable Refractory Lining

Selection skills of refractory castables

Refractory castables are divided into neutral, acidic, alkaline, and heavy and light. Heavy-weight refractory castables are generally used in the working layer, while light-weight castables are used in the insulation layer for heat preservation.
If it is a neutral high-aluminum refractory castable, the castable of which index is used is determined according to the temperature and erosion of the furnace lining. If the temperature is below 1200°C, use clay castables; if the temperature exceeds 1250°C, use high-alumina castables. If the use temperature exceeds 1350℃, corundum refractory castable is used. If it is extremely corrosive, chromium corundum castable should be used. If the wear is severe, wear-resistant refractory castables are used. The storage time of neutral materials is 6 months, so we must pay attention to the separate opening of raw materials and binders.
If it is a castable used in an acidic atmosphere, an acidic castable should be used. There are two combinations of acidic castables, one is water glass combination and the other is phosphoric acid combination. If it is an acidic atmosphere with a temperature not exceeding 1250°C, the acidic castable combined with water glass can be used. If the temperature is too high, choose acid-resistant castable combined with phosphoric acid.
If it is a castable used in an alkaline atmosphere, magnesia refractory castable should be used. In the case of erosion and wear resistance, use magnesia-aluminum refractory castables or magnesia-chromium castables. If the temperature is too high, magnesia castables with high specific gravity or high content magnesia castables can be used. However, the preservation of magnesia castables must be paid attention to, and they cannot be stored in the open air. Because the magnesia castable cannot see water, otherwise it will pulverize.
If it is a castable for the insulation layer, it also depends on the temperature. If the temperature is low, general light-weight insulation castables can be used. If the temperature is too high, use lightweight high-aluminum or alumina hollow sphere lightweight castables as the insulation layer. The storage of lightweight castables must also be paid attention to, and it should not be placed with materials that are too corrosive, otherwise it will cause damage to the lightweight castables.
If the furnace shell requirements are low, double-layer insulation should be used to solve the problem. It is possible to first use ceramic fiber and then light-weight thermal insulation castable, or directly use ceramic fiber blocks to solve the problem. But if there is a weight requirement in the insulation area, use a specific gravity of 0.6-0.8 as the insulation layer. If the flue is directly used in the thermal insulation castable of the working layer, a lightweight castable with a specific gravity of 1.3-1.5 is used as the lining. If it is acid-resistant atmosphere, it is necessary to choose to use light acid-resistant castable as the lining.
In short, no matter what refractory castable is selected, the castable must be selected according to the use situation, the lining atmosphere, and the temperature.

Tips: What is the relationship between the performance of high-alumina castables and the cement content?
High-aluminum castables often have a higher proportion of cement content, but this also causes a series of performance declines in high-alumina castables. So, what is the relationship between the properties of high-alumina castables and the cement content?

high-alumina castables

1. In order to fully hydrate the cement, excessive water (10%~15%) is needed when mixing. This is easy to cause ceramic refractory castables to show high porosity and decrease density.
2. Calcium aluminate hydrate has a strong dehydration and recrystallization effect in the middle temperature stage. This 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.
3. The cement binder brings more calcium into the castable. This leads to a decrease in the softening temperature of the ceramized high-alumina refractory castable under load, and a decrease in the thermal shock stability performance index.
To learn more about refractory castables, please continue to pay attention to our blog. To purchase high-quality refractory castables, please choose a strong refractory manufacturer.