1. Introduction to the types of unshaped refractory materials

Pouring material

Pouring material is a material with good fluidity after adding water and stirring. Proper curing after molding makes it harden, and it can be used after baking. The casting material uses aluminum silicate clinker, corundum material or alkaline refractory clinker as the aggregate; the lightweight casting material uses expanded perlite, vermiculite, ceramsite, and alumina hollow spheres as the aggregate. The binding agent uses calcium aluminate cement, water glass, ethyl silicate, polymeric aluminum, clay, or sodium chloride. The role of the admixture is to improve the construction performance and improve the physical and chemical properties, and use it according to the specific situation.

There are three methods for construction and molding of pouring materials: injection method, vibration method, pump injection method and spray method. When casting materials are used as integral linings, they often need to be used in conjunction with metal or ceramic anchors. If you add stainless steel fiber reinforcement, you can improve its resistance to mechanical vibration and thermal shock. Pouring material is used as the lining of various heat treatment furnaces, ore roasting furnaces, catalytic cracking furnaces, reformers, etc., and also used as the inner lining of melting furnaces such as lead-zinc melting furnaces, tin baths, salt bath furnaces, and high-temperature melt launders. lining.

Plastic

Plastics are plastic or mud bodies with plasticity. When appropriate external force is applied, it is easy to shape without cracking; after the stress is relieved, it will no longer be deformed. Plastic materials include not only semi-silica, high-alumina, carbon, clay, zircon, etc., but also light-weight plastics. Plastics must be added with plasticizing materials, most of which are highly plastic clays, and plasticizers can also be used to improve the plasticity of this clay. Plasticizers include carboxymethyl cellulose, dextrin, lignosulfonate and the like. The binders used for plastics include plastic clay, *acid, *acid aluminum dihydrogen, aluminum sulfate and so on. Alumina with *acid or *salt binder is plastic, and it will chemically react with alumina during storage to produce insoluble aluminum ortho-aluminum and harden the mud. Therefore, it is necessary to add preservatives, such as oxalic acid and lemon. Acid, acetyl*ketone, etc.

Generally, the construction method can adopt the ramming method or the vibration method. When using plastics to build the overall furnace lining, metal or ceramic anchors must be provided. Plastic can be used as the inner lining of soaking furnaces, heating furnaces, boilers and other thermal equipment, and can also be used to wrap water-cooling tubes of heating furnaces.

Gunning material

Gunning material is a refractory mixture used for gunning or spraying with a jet machine. According to the gunning method, it can be divided into wet 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 mist dispersion, high adhesion rate, and more uniform thin-layer gunning. Semi-dry gunning is to add water to the nozzle to wet the refractory powder sprayed by compressed air. The amount of water added is 11-14*, the adhesion rate is low, and the thicker layer of gunning can be carried out. Fire gunning belongs to dry gunning. The gunning material is sent to the flame of the fuel oxygen spray gun. The gunning material is partially melted in the nozzle flame and adheres to the brick lining.

Gunning materials are made of aluminum silicon, aluminum silicon zirconium, magnesia, magnesia calcium, magnesia chromium, etc. The binding agents used are sodium silicate, sodium sulfate, polycarbonate, asphalt, resin and so on. 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 such as serpentine, pure olivine, lime, refractory clay, and iron oxide are also added.

Refractory coating

The material coated on the refractory brick lining. According to different application requirements and construction methods, refractory coatings can be formulated into paste-like and mud-like forms. The binding agent used varies with the material, such as alkaline coatings * acid salt, poly * acid salt, magnesium sulfate for the preparation of continuous casting tundish; for the preparation of high alumina coatings, clay, aluminum acid dihydrogen acid, aluminum chromate * salt are used , Water glass, etc. In order to improve the spreadability of the coating, additives such as plasticizers are generally added. The paint is mainly used as a protective coating for the lining of various thermal equipment, or used to repair local damage to the brick lining.

Ramming material

A bulk refractory material with low or no plasticity. The materials are siliceous, clay, high alumina, corundum, zircon, silicon carbide, carbon, magnesia, etc. According to the material and use conditions of the ramming material, inorganic binders or organic binders similar to the casting materials can be used, such as water-soluble dextrin, carboxymethyl cellulose, lignin, sulfonate, polyvinyl alcohol; water resistance And with thermoplastic paraffin, asphalt, tar, phenolic resin, random polypropylene and so on.

The ramming material adopts forced ramming construction, with low porosity and high density. Therefore, among the unshaped refractory materials, the ramming material is particularly suitable for smelting furnace lining and various containers for holding high-temperature molten metal such as open furnaces and The lining of electric furnace hearth, various induction furnace lining, blast furnace tapping channel, ladle, etc.

Projection material

A semi-dry mud that is projected by a projection machine to build a lining. Mainly used to build the lining of the whole steel drum. The materials are siliceous, wax stone, clay, high alumina and zircon. The most used are high-silicon and high-aluminum projection materials.

Characteristics of unshaped refractories

1. The factory occupies a small area, does not require forming and firing processes, consumes little energy, and has low investment and operating costs.

2. It can obviously reduce the variety and quantity of special-shaped bricks, which is convenient for material preparation and construction.

3. The furnace lining has good integrity, improves the strength and air tightness, and reduces heat loss.

4. Equipped with metal or ceramic anchors, or reinforced with stainless steel fibers, it can improve the resistance to mechanical vibration and thermal shock, and it can also repair damaged parts locally.

5. It is convenient for storage and transportation, which is conducive to the mechanization of furnace construction. The construction management must be strict, otherwise it will affect the physical and chemical properties and life of the furnace lining. Sometimes unshaped refractory materials are used as prefabricated components.