Classification and definition of refractory clay

Classification and definition of refractory clay

Refractory mud is an important refractory material, mainly used for masonry of refractory bricks and other refractory products, playing the role of bonding and sealing. The following is the classification and definition of refractory mud:

Classification by Chemical Composition

Neutral Refractory Clay

Definition: Neutral refractory clay has relatively balanced chemical properties, with its primary components typically including aluminum oxide (Al₂O₃). High-alumina refractory clay is a common neutral refractory clay, with an Al₂O₃ content generally ranging from 45% to 85%. It can be used in both acidic and alkaline environments, offering good versatility. For example, in furnaces with complex chemical environments that may come into contact with both acidic and alkaline substances, such as certain non-ferrous metal smelting furnaces, neutral refractory clay demonstrates its excellent adaptability and ensures the proper operation of the furnace.

Basic Refractory Clay

Definition: Basic refractory clays are primarily composed of alkaline oxides such as magnesium oxide (MgO) or calcium oxide (CaO). For example, magnesia refractory clays contain a high concentration of MgO, typically ranging from 70% to 90%. This type of refractory clay is primarily used in alkaline furnaces, such as basic steelmaking furnaces and magnesia brick linings. In these furnaces, basic refractory clay bonds well with the alkaline lining material and resists corrosion from alkaline slag, ensuring the integrity and tightness of the lining.

Acidic Refractory Clay

Definition: Acidic refractory clay is primarily composed of silicon dioxide (SiO₂), which resists corrosion from acidic substances at high temperatures. For example, siliceous refractory clay is a typical acidic refractory clay. It is primarily made from silica powder and typically contains over 90% SiO₂. This type of refractory clay is widely used in industrial furnaces operating in acidic environments, such as glass melting furnaces and acid metallurgical furnaces. These furnaces generate large amounts of acidic gases or slag during operation, and acidic refractory clay effectively prevents corrosion.

Classification by Binder Type

Ceramic-bonded Refractory Clay

Definition: Ceramic-bonded refractory cladding achieves its bond through a high-temperature sintering process that forms a ceramic phase. At high temperatures, certain components in the refractory cladding undergo a chemical reaction, forming a ceramic-like structure that bonds the refractory material together. The advantages of this type of refractory cladding include high strength and excellent corrosion resistance at high temperatures. For example, some ceramic-bonded refractory claddings used for high-temperature kiln linings, after sintering at temperatures between 1400°C and 1600°C, form a dense ceramic bond that effectively resists erosion from slag and gases.

Waterglass-bonded refractory mortar

Definition: Waterglass-bonded refractory mortar uses waterglass (sodium silicate or potassium silicate) as a binder. When mixed with the other components of the mortar, waterglass undergoes a series of physical and chemical changes, forming a gel structure with a certain degree of adhesion. This mortar exhibits excellent room-temperature bonding properties and is relatively easy to apply. For example, in low- to medium-temperature furnace masonry, waterglass-bonded refractory mortar can quickly bond refractory bricks and maintain good performance within a certain temperature range (e.g., below 1000°C).

Phosphoric Acid Bonded Refractory Clay

Definition: Phosphoric acid bonded refractory cladding uses phosphoric acid or phosphates as a binder. Phosphoric acid reacts with metal oxides and other components in the refractory cladding to form phosphate bonds, thereby bonding the refractory materials together. This refractory cladding exhibits high high-temperature strength and excellent chemical stability. For example, in certain high-temperature, wear-resistant industrial furnaces, phosphoric acid bonded refractory cladding effectively bonds the refractory materials and maintains structural stability under the complex conditions of high temperature, wear, and chemical attack.

Cement-bonded Refractory Clay

Definition: Cement-bonded refractory cladding uses refractory cement (such as alumina cement) as a binder. When mixed with water, the refractory cement undergoes a hydration reaction, forming a gel-like substance that gives the refractory cladding its adhesive properties. The advantages of this type of refractory cladding include relatively rapid hardening and high early strength. For example, in furnaces and kilns that require rapid construction and commissioning, cement-bonded refractory cladding can achieve a certain strength quickly, meeting basic requirements. However, its long-term high-temperature performance may not be as good as that of ceramic-bonded or phosphate-bonded refractory cladding.