Month: November 2023

Refractory Material Manufacturers Respond – How to Correctly Choose Refractory Castables?

KilnRefractory

Refractory castables are divided into acidic, alkaline, and neutral castables according to their resistance to chemical attack. According to the volume density, it is divided into dense castable refractory and light castable. According to the materials used, it is divided into aluminum silicate, magnesium, magnesium chromium, corundum castables, etc. There are many types of refractory castables, and it is difficult to make a choice without clear indicators and operating temperatures. RS refractory material manufacturer responded to “How to correctly choose refractory castables” and gave some more reliable methods for reference.

(1) Refractory castables must meet the requirements of the kiln’s usage environment.

Dense refractory castables have different requirements depending on where they are used. When selecting, it should be selected according to the characteristics of the castable. For parts that come into contact with high-temperature flames, high-temperature-resistant castables should be selected. Castables with high-temperature resistance and strong penetration resistance should be selected for parts that come into contact with high-temperature solutions. The parts that come into contact with slag should use castables that are highly resistant to the chemical erosion of slag. High-strength and wear-resistant castables are used for parts that come into contact with the impact and friction of various materials. For parts with frequent temperature changes, castables with excellent thermal shock resistance should be used. As long as it meets the requirements of the main production conditions, it is a suitable refractory castable.

Corundum Refractory Castable
Corundum Refractory Castable

The main uses of lightweight refractory castables are heat insulation, reducing load-bearing structures, lowering furnace shell temperature, and reducing heat loss, thereby achieving energy-saving effects.

(2) Economy of investment cost of refractory castables.

After determining which refractory castable to choose, it is also necessary to economically reduce costs. For example, if the use temperature is 1500°C, castables with a use temperature greater than 1600°C will not be selected if the castables can meet the working conditions. If high alumina bauxite clinker is used as the main material in the wear-resistant parts to meet the wear resistance requirements, castables with corundum as the main material should not be selected. The main reason is that the price of refractory castables varies greatly depending on the content of the main materials used. There is no need to ignore economic costs in pursuit of high quality. This requirement is especially important for parts that are subject to daily wear and tear.

(3) Particle size selection of refractory castables.

The construction parts of refractory castables may be thick or thin, and the particle size ratios used are different. For example, when pouring a lining with a thickness greater than 100mm, more large-grained critical aggregates need to be added to improve structural strength and wear resistance. The parts with a thickness of 10mm when poured or painted have fewer large particles of aggregate. Avoid adding large aggregates to make them protrude from the lining, which not only affects the appearance but also causes large particles to wear easily in terms of use. This causes holes in the lining, which in turn affects the service life. Depending on the pouring thickness, the pouring method or the smearing method can be used. Therefore, the selection of particle size of refractory castables is also very important.

(4) The shelf life of refractory castables.

The storage time of refractory castables in dry areas is about 6-9 months. Before use, check whether there are any agglomerations. During transportation or handling, the castable will agglomerate due to extrusion. If it can be easily patted away, the use effect will not be affected. However, the shelf life of the castables is a secondary consideration, because the configuration processes of the castables are different and most parts are not in stock. All need to be produced according to user needs and the production process adjusted.

It can be seen from the above that the selection of refractory castables is variable and must be used flexibly. To quickly select castables, it is necessary to mention the specific use location, working conditions, use temperature, pouring thickness, and construction method of the castables. The main thing is to find the right method to choose high-quality refractory castables while reducing costs.

Wear-Resistant Castable
Wear-Resistant Castable

Performance Characteristics of Dense Refractory Castables

Dense refractory castable is a construction material used in high-temperature operations. Its main function is to fill and support the furnace while providing oxidation resistance at high temperatures. Dense castables refractory are further divided into aluminate cement castables, chemically bonded refractory castables, clay bonded refractory castables, low cement series refractory castables, self-flowing castables, and new technology refractory castables. The body density is generally around 1800Kg/m³-3500Kg/m³.

Dense refractory castables are generally used for furnace lining, working layer, and permanent layer. According to the use environment, use location, and use requirements, different refractory castables are used to extend the service life of the castables.

High-temperature antioxidant properties. Medium and Dense castables refractory can withstand high temperatures and high oxidation temperatures, and their oxidation resistance is better than other types of castables. Can be used in high-temperature furnaces for a long time.

Reusability. Medium and Dense refractory castables can be reused, reducing environmental pollution and waste of resources.

Density and weight. Medium-Dense castables refractory have a lower density and weight than other types of castables, making them easier to move and fill within the furnace.

chemical composition. The chemical composition of medium and Dense refractory castables can be adjusted according to different requirements to meet different high-temperature environments and application needs.

Stability and reliability. Medium and Dense castables refractory can withstand high temperatures and high oxidation temperatures and maintain stability and reliability over long periods of use.

manufacturing cost. Medium-Dense refractory castables are more expensive to manufacture than other types of castables, but their performance value and cost of use make them a popular high-temperature building material.

RS Kiln Refractory Factory

RS Kiln Refractory Factory can provide high-quality refractory lining materials for high-temperature industrial furnace linings, including various refractory bricks, refractory castables, refractory plastics, etc. If you need to buy Dense castables refractory, Dense refractory bricks for the working lining of high-temperature industrial furnaces. Please contact us. We can provide you with high-quality refractory materials at competitive prices.

How to Use Low Cement Castables Efficiently?

KilnRefractory

Low cement castables are widely used in the steel industry because of their advantages such as high density, good fire resistance, and excellent slag resistance. At the same time, low cement castables also have some disadvantages. Such as instantaneous coagulation, delayed hardening instantaneous loss of fluidity, etc. Failure to achieve the construction effect will cause losses to users and cause worse effects. So how to use low cement castables efficiently?

Rongsheng Low Cement Castable
Rongsheng Low Cement Castable

Problems that easily occur during the construction of low cement castables. Since low-cement castables contain various additives, they are easily affected by external influences during construction. Its operating performance and quality are prone to changes over time. The main manifestations of on-site construction include excessive condensation, delayed hardening, and reduced fluidity. In the past, low cement castables have experienced phenomena such as instantaneous setting, delayed hardening, and instantaneous loss of fluidity during construction. RS Kiln Refractory manufacturer found through research that the above problems are related to the construction performance of low cement castable itself.

(1) Condensation too fast and too slow

The setting and hardening process of low-cement castables is caused by hydration bonding and cohesion bonding, or cohesion bonding alone. After the water-reducing agent in the castable is determined, the fluidity of the castable will also vary greatly depending on the amount of pure calcium aluminate cement added. When the addition amount exceeds 9%, the flow value of the castable is lower than 110mm, and the normal construction fluidity of the castable can no longer be guaranteed. This may be due to the excessive amount of pure calcium aluminate cement that accelerates the setting and hardening process of the castable.

The following measures can be taken to solve the aging changes of low cement castables. (1) Double-sealed packaging, especially in the rainy season or when the storage time is long. (2) Choose a dispersant with a strong dispersing ability. (3) Consider adding some newly opened packages of cement during construction and mixing. (4) Use a powerful mixer to mix and control the mixing time. (5) Add an accelerator or retarder to adjust the hardening speed of the castable. (6) In terms of on-site management, prevent moisture absorption during storage.

At present, the most effective way to solve the aging change of low cement castables on site is to add a setting accelerator or retarder to the castables. The accelerators and retarder used, especially the carbonate accelerator and citric acid retarder, are used in small quantities have significant effects, and have no adverse effects on the strength of the castable at all temperatures.

Low Cement Castable Refractory Material
Low Cement Castable Refractory Material

(2) Instantaneous loss of liquidity

Instantaneous loss of fluidity sometimes occurs during castable construction. The analyzed reason should be due to the failure of the water-reducing agent in the castable material or improper operation during construction.

Water reducing agent is a surface active substance. The surface activity of inorganic water-reducing agents is not significant. It mainly increases the zeta potential through chemical adsorption, effectively destroying the flocculation structure between particles. Give full play to the filling effect of micro powder and the lubrication effect of free water to increase fluidity. The anionic group N ionized by the organic water-reducing agent in water has a strong surface activity. Its lipophilic end is adsorbed on the surface of colloidal particles by physical adsorption and enters the fixed adsorption layer. The ζ potential increases in the negative direction, and the oil-repellent ends repel each other to achieve the purpose of dispersion. However, the water-reducing agent easily absorbs the moisture in the castable ingredients during the storage process and causes deliquescence and hydrolysis, which increases the acidity of the castable ingredients. This results in loss of water-reducing effect and instantaneous fluidity loss. Therefore, measures should be taken during the production and storage of castables. For example, use a water-reducing agent with poor hygroscopicity, separate the water-reducing agent from the castable, etc. At the same time, instantaneous fluidity loss may also occur during the construction of high-tech castables, especially when the mixing time is too long. We believe that the reason should be caused by the temperature rise caused by long-term stirring.

In addition, when using low-cement castables, avoid adding too much water. If too much water is added, its performance will decrease and even cause the following hazards:

  • Reduced intensity. Adding too much water will make the water-cement ratio of low-cement castables too high. This results in a reduction in its strength and reduces the load-bearing capacity and service life of the refractory material.
  • Decreased slag resistance. Adding too much water to low-cement castables will lead to a decrease in slag resistance. It is susceptible to slag erosion and reduces the service life of refractory materials.
  • Poor thermal shock performance. Adding too much water to low-cement castables will result in a decrease in the thermal shock properties of the material. It is prone to cracking, peeling and other phenomena, which greatly shortens the service life of the material.
  • Construction difficulty increases. Adding too much water will result in increased flowability of low cement castables. Problems such as slurry leakage and looseness are prone to occur during construction, which affects the quality of the project.

According to the above content, it is known that adding too much water to low-cement castables will have a serious impact on its performance and service life. During construction, the amount of water added must be strictly followed to ensure the quality and performance of the material.

Before construction and storage, pay attention to moisture-proof and avoid contact with water; when using, control the amount of water added and use additives rationally. Storage and use in strict accordance with the construction instructions will basically enable low-cement castables to effectively exert their advantages in high-temperature industrial furnace linings. Contact RS Kiln Refractory Factory for a free quote and sample of low cement castables.