Classification of monolithic refractory materials
1.Grouting material
A material with good fluidity after adding water and stirring, also known as pouring material. After forming, it needs to be properly cured to make it solidify and harden, and can be used after baking according to a certain system. Grouting materials use aluminum silicate clinker, corundum material or alkaline refractory clinker as aggregate; lightweight pouring materials use expanded perlite, vermiculite, ceramsite, and hollow alumina balls as aggregate. The admixture depends on the use situation, and its function is to improve the construction performance and physical and chemical properties.
The construction molding methods of grouting materials include vibration method, pump injection method, pressure injection method, injection method, etc. Grouting materials are often used in conjunction with metal or ceramic anchors for integral lining. If stainless steel fiber reinforcement is added, its resistance to mechanical vibration and thermal shock can be improved. The grouting material is used as the lining of various heat treatment furnaces, ore roasting furnaces, catalytic cracking furnaces, converters, etc. It is also used as the lining of smelting furnaces and high-temperature melt flow channels, such as lead-zinc melting furnaces, tin baths, salt bath furnaces, steel or iron tapping troughs, steel ladle, molten steel vacuum circulation degassing device suction nozzles, etc.
2.Plastisol
Plastic clay or clay blank. When appropriate external force is applied, it is easy to deform without cracking; after the stress is eliminated, it will no longer deform. Plastic materials include semi-siliceous, clay, high-alumina, zircon, carbon, etc., and there are also lightweight plastics. Plastic materials must be added to plastics, and plastic materials are mostly highly plastic clays. Plasticizers can also be used to improve the plasticity of this clay. Plasticizers include carboxymethyl cellulose, dextrin, lignin sulfonate, etc. The binders used in plastics include plastic clay, phosphoric acid, aluminum dihydrogen phosphate, aluminum sulfate, etc.
The construction method generally adopts ramming method or vibration method. When using plastic to build an integral furnace lining, metal or ceramic anchors must be configured. Plastics are used as linings for thermal equipment such as soaking furnaces, heating furnaces, boilers, and are also used to wrap water-cooling pipes for heating furnaces.
3.Gunning material
A refractory mixture used for gunning or spraying with a jet machine. According to the gunning method, it can be divided into wet gunning (or mud gunning), semi-dry gunning and fire (flame) gunning. Wet gunning uses compressed air to spray mud containing 20-40% refractory powder, which can achieve higher atomization and high adhesion rate, and can be used for more uniform thin layer gunning. Semi-dry gunning is to add water to the nozzle to moisten the refractory powder sprayed by compressed air. The amount of water added is 11-14%, the adhesion rate is lower, and thicker layers can be gunned.
Gunning materials include aluminum silicon, aluminum silicon zirconium, magnesium, magnesium calcium, magnesium chromium, etc. The binders used are sodium silicate, phosphate, polyphosphate, asphalt, resin, etc. In order to improve the adhesion rate, clay, bentonite, lime and other additives are added. In order to ensure that the gunning material can achieve good sintering, sintering aids are added, such as serpentine, olivine, lime, refractory clay, iron oxide, etc.
4.Refractory coating
The material applied to the refractory brick lining. According to different use requirements and construction methods, refractory coatings are prepared in the form of mud paste and mud. The binder used varies according to the material. For example, phosphate, polyphosphate, and magnesium sulfate are used for preparing alkaline coatings for continuous casting tundishes; clay, aluminum dihydrogen phosphate, aluminum chromium phosphate, water glass, etc. are used for preparing high-alumina coatings. In order to improve the spreadability of the coating, plasticizers and other additives are generally added. The coating is mainly used as a protective coating for the lining of various thermal equipment, or for repairing local damage to the brick lining.
5.Ramming material
A bulk refractory material with very low or no plasticity. The materials include siliceous, clay, high alumina, corundum, zircon, silicon carbide, carbon, magnesium, etc. According to the material and use conditions of the ramming material, inorganic or organic binders similar to the pouring material can be used, such as water-soluble dextrin, carboxymethyl cellulose, lignin, sulfonate, polyvinyl alcohol; water-resistant and thermoplastic paraffin, asphalt, tar, phenolic resin, random polypropylene, etc.
Ramming material is constructed by forced ramming, with low porosity and high density. Therefore, among amorphous refractory materials, ramming material is particularly suitable for lining of smelting furnaces and various containers for high-temperature molten metal. Such as open-hearth and electric furnace hearths, various induction furnace linings, blast furnace tapping channels, steel ladle, etc.
6.Projection material
A semi-dry mud material that is projected by a projection machine to build the lining. It is mainly used to build the lining of the integral steel ladle. The materials include silica, wax stone, clay, high alumina and zircon. The most commonly used are high silica and high alumina projection materials.
Application of monolithic refractory materials
1.Characteristics of castable precast blocks
The castable prefabricated block only needs to be heat treated at a relatively low temperature. It is a low-carbon and green refractory material and a unique technology in the refractory lining technology. It can improve the performance of the refractory lining, reduce the consumption of refractory materials, and has stable quality and reliable performance. We know that the purpose of adding steel fiber to the castable is to improve the mechanical properties of the castable, inhibit the generation of cracks or limit their expansion when cracks are formed. The figure below is a picture of steel fiber castables. The steel fiber castable prefabricated block is made using a special process. It is made into a certain shape according to the process location and needs, and heat treated according to its working conditions after demoulding.
2.Application of monolithic refractory materials in blast furnaces
Blast furnace is an important equipment for iron making. Small blast furnaces used to be built by hoisting prefabricated blocks of high-alumina cement and high-alumina phosphate refractory castables, but now resin-bonded aluminum-carbon unburned bricks are commonly used for masonry. The water-cooled walls of large blast furnaces are made of SiC castables, and the bottom cushion and surrounding brick joints are made of refractory castables and silicon nitride fillers. One of the development trends of refractory materials for furnace walls is to use castables. The No. 2 blast furnace of Fukuyama Plant of Japan Steel Pipe Company uses a high-density castable of Al2O350%, SiO245% on the upper part of the furnace body. After 6 years of use, it was found that there was little peeling.
At present, the amorphous refractory materials used for blast furnace tapping channels at home and abroad are mainly Al2-O3-SiC-C (ASC for short), in addition to mullite-SiC-C, Al2O3-C, magnesia-aluminum spinel and other types. my country mainly uses corundum-SiC castables. Most of the blast furnace tapping channels in Japan now use ASC castables and repair gunning materials, and some small blast furnace tapping channels use alumina or synthetic mullite-SiC-C ramming materials. The blast furnace tapping channels in Germany and France generally use ASC ramming materials. France has developed self-flowing castables to increase the service life of the working lining of the main tapping channel.
3.Application of unshaped refractory materials in ladle
The increase in tapping temperature and the extension of the residence time of molten steel in the ladle have greatly changed the refractory materials used in the ladle. The ladle used to be mainly made of shaped refractory materials, but now it is replaced by amorphous refractory materials. The amorphous shape of the ladle can save labor and realize factory automation construction and drying, improving the overall economy. When the side wall of the ladle is amorphous, the maintenance work hours can be saved by 40%. When the ladle lining is all amorphous, the labor saving effect is 70%. Since Al2O3-spinel castables have corrosion resistance Good resistance, small structural spalling, long service life and can improve the quality of steel, making it the main refractory material for the current ladle. However, its use is limited by temperature and molten steel residence time. The Al2O3-MgO castable developed by Kawasa-ki Company of Japan has improved material strength and slag permeability resistance, and its service life is 20% longer than that of Al2O3-spinel castable. At present, the trial use of magnesium refractory castables and aluminum-magnesium-carbon refractory castables on ladles has also achieved initial results.
4.Application of monolithic refractory materials in nonferrous metallurgy
Aluminum smelting reverberatory furnace is a major consumer of refractory materials in aluminum plants. The refractory materials used in the furnace have changed from brickwork to an integral structure. The refractory materials in contact with the hot metal surface of the furnace are usually acid-bonded plastics, phosphate-bonded bricks and low-cement castables. The composition of the hot surface refractory materials of the lower side wall is usually the same as that of the furnace. The insulation material can be lightweight insulating castables, insulating clay bricks or ceramic fibers; the furnace roof material is usually high-quality refractory materials such as ramming materials and burning injection materials; the furnace door is usually cast with dense castables or lightweight castables, and can also be cast with a mixture of the two.
In electrolytic aluminum smelting, amorphous refractory materials are mainly used in aluminum drums. Refractory materials for aluminum drums are required to be resistant to the erosion of aluminum water, withstand the effects of rapid cooling and heating, and have good thermal insulation performance. The non-working lining of aluminum drums generally uses lightweight castables or lightweight high-alumina bricks. If the aluminum liquid in the aluminum drum is to be placed for a long time, thermal insulation castables are usually used to prevent the aluminum liquid from solidifying during transportation. Now, in order to reduce the dead weight of the tank body and enhance the thermal insulation effect, alumina hollow ball refractory castables are used for non-working linings. The working lining is generally built with high-alumina bricks with low SiO2 content. Some tank bodies now use corundum refractory castables.
