High Temperature Performance of Silicon Carbide Refractories

SiC is widely used in key areas of the steel and nonferrous metallurgy industries due to its stable high-temperature chemical properties, excellent high-temperature strength, high wear resistance, and good thermal shock resistance. Examples include blast furnace tuyere, inner wall, ceramic cups, various furnace wall linings, and kiln furniture. Compared to metals and intermetallic compounds, silicon carbide refractories have higher high-temperature strength and creep resistance. Compared to oxide ceramics, they have higher thermal conductivity and thermal shock resistance. The high-temperature properties of silicon carbide refractories are as follows:

Silicon Carbide Refractory Castable
Silicon Carbide Refractory Castable

Free Quote

    Leave Your Requirements

    Your Name (required)

    Your Email (required)

    Your Phone


    Your Requirements(required)

    High-Temperature Oxidation Resistance of SiC Refractories

    Although SiC offers excellent performance, it is susceptible to oxidation during long-term use. Extensive research has been conducted on the oxidation process of SiC. Results indicate that high-temperature oxidation of SiC can be divided into two types: passive oxidation and active oxidation. When the O₂ partial pressure is below 10⁻⁴Pa, SiC undergoes active oxidation, with the product being SiO₂ gas and the net weight decreasing. When the O₂ partial pressure is above 10⁻⁴Pa, SiC undergoes passive oxidation, with the product being SiO₂ and the net weight increasing. The formation of a SiO₂ protective film prevents further oxidation. However, at oxidation temperatures above 1473K, SiO₂ converts to cristobalite at high temperatures. This volume expansion destroys the structure of the oxide film, causing cracks, which in turn leads to internal oxidation, severely shortening the service life of the SiC material. Therefore, improving the oxidation resistance of SiC materials is an essential consideration in the design and preparation of SiC refractories.

    The high-temperature oxidation behavior of a self-bonded SiC material with a porosity of 11.5% in air at 1573K was studied. Research results show that the amorphous SiO2 formed during the initial oxidation process can passivate pores and crack tips within the material, resulting in an increase in the room-temperature strength of the material with increasing oxidation time. The refractory material achieved its highest strength, reaching 293 MPa, at an oxidation time of 22.5 h. As oxidation time continues, the amorphous SiO2 crystallizes to form cristobalite, destroying the structure of the oxide film and generating new surface cracks during cooling, resulting in a decrease in the room-temperature strength of the material.

    The effects of adding varying amounts of calcium oxide, aluminum oxide, and zirconium oxide to SiC on its oxidation resistance at different temperatures were investigated. Experimental results show that a 2 wt% aluminum oxide addition yields the best oxidation resistance. Mullite coatings were generated on recrystallized SiC materials of varying particle sizes using a sol-gel method. The effects of coating thickness and particle size on the high-temperature oxidation behavior of the recrystallized SiC at 1773 K were investigated. Results show that the formation of mullite coatings significantly improves the high-temperature oxidation resistance of the recrystallized SiC. Furthermore, increasing coating thickness increases the oxidation resistance of the recrystallized SiC material. Al₂O₃, SiO₂, and Mullite coatings were applied to SiC whiskers using a sol-gel method. Anti-oxidation experiments showed that all three coatings improved the oxidation resistance of SiC.

    In summary, while silicon carbide refractories possess relatively good oxidation resistance, oxidation to a certain degree can be fatal to the material’s structure. Therefore, studying the mechanism and control of the oxidation process in silicon carbide refractories, as well as its impact on the material’s structure and properties, is of great significance.

    Silicon Carbide Lining Refractory for Furnaces
    Silicon Carbide Lining Refractory for Furnaces

    Free Quote

      Leave Your Requirements

      Your Name (required)

      Your Email (required)

      Your Phone


      Your Requirements(required)

      Thermal Shock Resistance of SiC Refractories

      As an important high-temperature industrial structural material, silicon carbide refractories have high requirements for thermal shock resistance. The thermal shock resistance of SiC materials is not only related to their microstructure, grain size, and the shape and distribution of internal defects, but also to physical properties such as strength, elastic modulus, thermal conductivity, thermal expansion coefficient, Poisson’s ratio, and porosity. Improving and enhancing the thermal shock resistance of SiC materials is crucial for their safe and stable use.

      The Effect of Different Bonding Methods on the Thermal Shock Resistance of SiC Kiln Furniture. Si2N2O-bonded SiC kiln furniture exhibits superior thermal shock resistance to mullite- and Si3N4-bonded SiC kiln furniture. When the Si2N2O content is ≤20%, the thermal shock resistance of Si2N2O-bonded SiC samples improves with increasing Si2N2O content. When the Si2N2O content exceeds 20%, the thermal shock resistance of the samples decreases.

      Si3N4-SiC and Sialon-SiC materials were prepared by reaction sintering. The results show that the in-situ formation of Si3N4 or Sialon bonding phases can increase the toughness of SiC materials, influence crack propagation, and modulate stress distribution at high temperatures, improving the material’s plastic deformation capacity at high temperatures and, consequently, enhancing the thermal shock resistance of SiC materials.

      The thermal shock resistance of reaction-sintered SiC materials was also studied. The results show that materials with low residual Si content and small SiC particles exhibit superior thermal shock resistance to materials with high residual Si content and large SiC particles.

      Aluminum Silicon Carbide Castables
      Aluminum Silicon Carbide Castables

      Free Quote

        Leave Your Requirements

        Your Name (required)

        Your Email (required)

        Your Phone


        Your Requirements(required)

        SiC Refractories’ Resistance to Cryolite Attack

        SiC is used as the bottom material for aluminum electrolytic cells because it is non-wettable by molten aluminum and exhibits high thermal conductivity, chemical stability, and excellent oxidation resistance. Aluminum smelting typically uses cryolite (Na₃AlF₆) as a flux, and is carried out by electrolytic reduction of aluminum oxide in the electrolytic cell at a temperature typically between 1173 and 1273 K. Therefore, studying the resistance of SiC materials to cryolite attack is of great practical significance.

        The attack of cryolite on various non-oxides, such as BN, SiC, Si₃N₄, Al₁N, and TiN, was studied. The results showed that these non-oxides exhibited good resistance to cryolite attack. Cryolite melt enters the pores of Si₃N₄-bonded SiC refractory materials and reacts with the binder phase. Erosion of the binder phase causes SiC particles to fall into the cryolite melt, resulting in corrosion of the material.

        The crucible method was used to study the cryolite melt corrosion resistance of Si3N4-bonded SiC refractory materials. The results showed that after 20 hours of corrosion at 1273K, only a small amount of corrosion was observed on the inner wall of the crucible of the Si3N4-bonded SiC refractory prepared in an air atmosphere. This indicates that the material has good cryolite corrosion resistance.

        The static crucible method was also used to study the cryolite corrosion resistance of alumina-based Sialon-bonded corundum-SiC composite refractory materials at 1273K. The results showed that under these conditions, cryolite erosion of the composite material was minimal, with an erosion layer thickness of approximately 1mm, and the erosion product being NaAlSiO4. The penetration layer depth was approximately 6mm, and the penetration rate decreased with increasing Sialon content.

        In summary, silicon carbide refractory materials have excellent cryolite corrosion resistance. The corrosion mechanism suggests that corrosion primarily occurs between cryolite and oxides in the binder phase. Reducing or eliminating the oxide content in the binder phase could further improve the cryolite corrosion resistance of silicon carbide refractory materials.

        To purchase high-quality silicon carbide refractory materials, please contact Rongsheng Refractory Materials Factory for free samples and quotes.

          Get Excellent Service

          Please Leave Your Inquiry for Rongsheng Refractory Castable & Cement! We Will Reply You In 12 Hours!

          Your Name (required)

          Your Email (required)

          Your Phone

          Your Requirements(required)

          What Should You Do if the Refractory Plastic Cannot be Cured?

          Recently, a user of Rongsheng Refractory Material Factory consulted that a batch of refractory plastics purchased before could not solidify after ramming, and wanted to ask what was going on. Rongsheng Factory, based on years of production, sales, and construction experience, analyzed from the following aspects to help customers solve the problem. Rongsheng Refractory Castable Factory, a professional technical team, and an environmentally friendly fully automatic amorphous refractory production line provide material guarantees for the overall refractory lining of high-temperature industrial furnaces. Contact Rongsheng to get free solutions and quotes for refractory linings.

          Phosphate Bonded High Alumina Refractory Plastics
          Rongsheng Refractory Plastics

          Free Quote

            Leave Your Requirements

            Your Name (required)

            Your Email (required)

            Your Phone


            Your Requirements(required)

            As we all know, the components of refractory plastics are made of granular and powdered aggregates, plastic clay, and other binders and plasticizers, and then a small amount of water is added. After fully mixing, it is a hard mud-paste-like amorphous refractory material that maintains high plasticity for a long time.

            1. What aggregates and binders are refractory plastic components divided into?

            According to the type of aggregate, it can be divided into clay, high aluminum, mullite, corundum, chromium, silicon carbide, and zirconium-containing refractory plastics. According to the type of binder, it can be divided into refractory plastics combined with aluminum sulfate, phosphoric acid, phosphate, water glass and resin.

            1. The plasticity index of refractory plastics requires that the amount of water added must be limited when adding binders

            Plastic clay is an additional binder for plastics. It only accounts for 10%~25% of the total weight of plastics, but it has a great influence on the bonding strength between plastics and their hardened bodies, the plasticity of plastics, the volume stability and refractoriness of plastics and their hardened bodies.

            The plasticity of refractory materials is related to the characteristics of clay, the amount of clay used and the amount of water. It mainly depends on the amount of water, which increases with the increase of water. However, too much water will bring adverse effects, generally 5%~10% is appropriate.

            1. Necessity of adding appropriate amount of plasticizer to refractory plastic

            In order to control the amount of clay in plastic and reduce the amount of water, it is necessary to add appropriate amount of plasticizer. Its plasticizing effects mainly include: increasing the hygroscopicity of clay particles. Dispersing clay particles and wrapping them with water film. Dispersing humus in clay and making clay particles sol. Increasing the electrostatic repulsion between clay particles in clay-water system. Stabilizing sol. Excluding ions that hinder solification from the system as insoluble salts, etc.

            1. Considering the hardening and strength of plastic, it is necessary to correctly select the binder

            Plastic without any added chemical binder is called ordinary plastic. This kind of plastic has very low strength before sintering, but as the temperature rises, water escapes and the strength increases. After high-temperature sintering, the cold strength increases. But the hot strength at high temperature decreases with the increase of temperature.

            The strength of plastic with sodium silicate increases faster with the increase of temperature after construction, and the mold can be removed faster after construction. However, during the drying process, this binder may migrate to the surface of the structure or product, preventing the smooth removal of moisture and causing stress and deformation of the surface.

            Aluminum phosphate is the most widely used thermosetting binder in plastics. After construction, it can obtain high strength after drying and baking.

            In order to improve the shortcomings of plastics with soft clay as binder, such as slow hardening after construction and low strength at room temperature, it is often chosen to add an appropriate amount of air-hardening and thermosetting binders and their polymers.

            1. High-quality plastics also need to have excellent thermal shock resistance

            The good thermal shock resistance of plastics mainly depends on the following aspects: Plastics made of aluminum silicate refractory raw materials as granular and powdered materials will not produce serious deformation caused by crystal transformation during heating or when used at high temperatures. The mineral composition near the heating surface is fine crystals of mullite and cristobalite, with less glass, and transitions along the heating surface to the low-temperature side. The structure and phase of the plastic are gradual rather than drastic. Due to the uniform porous structure in the plastic component, the expansion coefficient and elastic modulus are generally low.

            1. Correct construction method of refractory plastics

            The construction of plastics requires a tamping machine or manual tamping. The thickness of each addition is 80~100mm. After tamping, the surface is loosened, and then the material is added to continue tamping until it is completed. According to the type of binder, temperature and humidity conditions, the plastic should be naturally dried for a period of time before demolding. Because demolding too early will cause cracks on the stress surface of the anchor brick. When the temperature is around 25℃, the plastic combined with phosphoric acid should be demoulded after 48 hours of natural drying. The plastic combined with aluminum sulfate and clay should be demoulded after 72 hours of natural drying.

            1. The shelf life of refractory plastic should not be too long

            Refractory plastic generally has a shelf life of 15 days. Experienced manufacturers do not use hydraulic binders to ensure that the plasticity of plastic does not decrease significantly during its shelf life. Rongsheng Refractory Material Manufacturers recommends that users use up the products in one construction within 3-5 days after the arrival of the goods, and do not store them for a long time.

            Rongsheng Refractory Material Manufacturer recommends that you purchase high-quality refractory plastic products and read the instructions for the construction and use of refractory plastic in detail. Strictly follow the construction instructions for construction. Choose a professional construction team to carry out the construction of the refractory furnace lining. After the construction is completed, reasonable maintenance of the refractory furnace lining can effectively extend the service life of the furnace lining.

              Get Excellent Service

              Please Leave Your Inquiry for Rongsheng Refractory Castable & Cement! We Will Reply You In 12 Hours!

              Your Name (required)

              Your Email (required)

              Your Phone

              Your Requirements(required)