100 questions about refractories for electric furnace steelmaking (4)

Section 4 Binders commonly used in refractory materials

33. What are the commonly used binders for refractory products?

There are clay fireclay, high alumina fireclay, water glass, brine, high temperature cement, phosphate, aluminum sulfate, tar pitch, resin glue, etc.

34. What is a binder? What is plasticity?

(1) It has bonding ability, can bond bulk refractory materials into shape, and the bond with certain strength is called binder.

(2) When the refractory material with binder is mixed into a mass, the mud mass will deform without cracking under the action of external force, and the characteristic that its shape remains unchanged after the external force is removed is called plasticity.

35. What are the characteristics of clay binder?

Clay binders generally use unsintered soft clay and semi-soft clay. Due to the large surface area and surface energy of clay particles, it has strong adsorption and is a kind of high-quality and low-cost binder. It is mainly used in clay bricks, high-alumina bricks, clay fire clay, and high-alumina fire clay products. It is characterized by easy shrinkage when dry, and shrinkage after firing.

36. What is water glass? What are the characteristics of water glass binder?

(1) Sodium silicate is also called sodium silicate or soaking alkali, and its molecular formula is Na2O.nSiO2. It is made of finely ground quartz sand powder and sodium carbonate or sodium sulfate in a certain proportion and then heated and melted at 1300 ° C to 1400 ° C to form sodium silicate. Then it is melted by steam in the container.

(2) The appearance of water glass is a blue-gray translucent thick liquid, and the ratio M is called the modulus. It is characterized by good bonding performance at room temperature and gradually melts as the temperature rises.

37. What are the characteristics of brine binder?

The main component of the brine binder is MgCl2, and contains 4 to 6 crystal waters. MgCl2 is not easily soluble in water no matter in winter or summer. It should be soaked in water before use, and slowly dissolved with low-pressure steam. Generally, brine with a concentration of 1.2 to 1.4 Baume is used. It is mainly used for permanent lining of electric furnace slope, high alumina powder, clay mud, and joint filler for bricks of soup channel floor. The brine binder is characterized by high strength at room temperature and medium temperature, and fast drying.

38. What are the characteristics of high temperature cement binder?

(1) High-temperature cement is a hydraulic binding material made of high-alumina bauxite and limestone as raw materials, mixed and sintered clinker in a certain proportion, and ground into fine powder. According to the different aluminum content, it can be divided into two types:

??(2) High-temperature cement is used in refractory castables and refractory concrete. It can be hardened after adding water and stirring. It is characterized by high medium temperature strength. The overall structural performance is strong. The use of feed should strictly control the amount of water added. The amount of water required for water hardening can be met, and too much water will form pores.

39. What are the characteristics of phosphate binders?

(1) The phosphate binder is made of industrial phosphoric acid H3PO4 with a concentration of 85%, adding 9-6 kg of water for every 10 kg, and diluting it into a solution with a concentration of 45-55%.

(2) The main function of phosphate combination is that it can chemically react with refractory materials, polymerize and form glue, which is suitable for acid, alkali and neutral refractory materials as binders. Its properties are fast hardening speed, high medium temperature strength and easy sintering at high temperature.

40. What are the characteristics of aluminum sulfate binder?

(1) Aluminum sulfate is white grain or powder, the molecular formula is Al2(SO4)3.18H2O, and the theoretical content of Al2O3 is 15.3%. It needs to be heated with hot water or steam at 80-100°C during preparation to accelerate the dissolution, and the commonly used concentration is about 1.2.

(2) Aluminum sulfate binder can also chemically react with refractory materials to form glue. It is characterized by strong cementing ability at room temperature, easy to decompose at medium temperature, and the strength decreases, but the strength increases when the temperature is above 1200 °C.

41. What are the characteristics of tar pitch binder?

(1) Tar pitch is a by-product of the coking process, and its composition is extremely complex. The main component is hydrocarbons, which belong to the category of organic binders. Tar pitch is a black solid at room temperature, and it softens as the temperature rises until it becomes a flowable viscous liquid before it can be used as a binder. Its biggest disadvantage is that the temperature of the binder is high, yellow smoke is emitted, the production environment is polluted, and the working conditions are poor.

(2) Tar pitch is mainly used for asphalt magnesia bricks, asphalt magnesia furnace lining, cold patching material for electric conduction, hot patching material, etc. Its characteristic is that the temperature should be raised rapidly during use, avoiding the softening temperature, and the asphalt tar is decomposed and carbonized at high temperature, and can form a network structure, with high strength and good slag corrosion resistance. But carbon is easily oxidized.

42. What are the characteristics of resin adhesive?

(1) Due to the increase of carbon content, the slag corrosion resistance of refractory bricks can be greatly improved, and the thermal shock resistance of refractory bricks can be improved. However, the maximum limit of carbon content added to the tar pitch binder is about 6%.

(2) Asphalt-modified phenolic resin binder is characterized by good affinity between graphite and refractory materials, high residual carbon content, it can be produced at room temperature, the bricks are dense, and the maximum limit of carbon content can be increased to about 25%. It is widely used in magnesia carbon bricks and aluminum carbon bricks. Resin glue is expensive and the production cost is high, so the price of its carbon-containing refractory brick is also relatively expensive.

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