What is unshaped refractory? What are unshaped refractories?

I. What is unshaped refractory?

Amorphous refractory is a kind of refractory material which is made of refractory aggregate with certain particle size gradation, powder, binder and admixture. They have no fixed shape and can be made into slurry, mud paste and loose, so they are also called loose refractories. Used for lining of thermal equipment, directly baked without sintering process. Compared with refractory bricks, unshaped refractory materials have the characteristics of simple process (due to the omission of firing process), energy saving, low cost and convenient mechanized construction. The application effect is better than that of refractory bricks in some thermal equipment.

Second, what are the unshaped refractories?

According to the construction method and material properties, unshaped refractories can be divided into pouring materials, plastic refractory, ramming materials, gunning materials, dry mixing materials, projectiles and coatings.

1. Pouring material

A material with good fluidity after mixing with water. After molding, it needs proper curing to make it coagulate and harden, and it can be used after baking according to a certain system. The pouring material takes aluminum silicate clinker, corundum material or alkaline refractory clinker as aggregate; The lightweight pouring material takes expanded perlite, vermiculite, ceramsite and alumina hollow spheres as aggregates. The binder is calcium aluminate cement, water glass, ethyl silicate, polyaluminum chloride, clay or phosphate. Admixtures depend on the usage, and their functions are to improve the construction performance and physical and chemical properties.

The construction and molding methods of pouring materials include vibration method, pump injection method, pressure injection method and injection method. As a whole lining, pouring material is often used in conjunction with metal or ceramic anchors. If it is reinforced with stainless steel fiber, its mechanical vibration resistance and thermal shock resistance can be improved. The pouring material is used as the lining of various heat treatment furnaces, ore roasting furnaces, catalytic cracking furnaces, reforming furnaces, etc., and also used as the lining of melting furnaces and high-temperature melt launders, such as lead-zinc melting furnaces, tin tanks, salt bath furnaces, tapping or tapping tanks, steel drums, suction nozzles of vacuum circulating degassing devices for molten steel, etc.

2. plastic refractory

Plasticity of mud or mud blank. When an appropriate external force is applied, it is easy to deform without cracking; After the stress is relieved, it is no longer deformed. Plastic refractory is made of semi-silica, clay, high alumina, zircon, carbon, and light plastic refractory. Plasticizing materials must be added to plastic refractory, which are mostly high plasticity clay. Plasticizers can also be used to improve the plasticity of this clay. Plasticizers include carboxymethyl cellulose, dextrin, lignosulfonate, etc. The binders used in plastic refractory are plastic clay, phosphoric acid, aluminum dihydrogen phosphate, aluminum sulfate and so on. Alumina plastic refractory added with phosphoric acid or phosphate binder will react chemically with alumina during storage to produce insoluble aluminum orthophosphate, which will harden the clay. Therefore, preservatives, such as oxalic acid, citric acid and acetylacetone, should be added.

The construction method generally adopts tamping method or vibration method. When using plastic refractory to build integral furnace lining, metal or ceramic anchors must be equipped. Plastic refractory is used as the lining of soaking pits, heating furnaces, boilers and other thermal equipment, and also used to wrap the water cooling pipes of heating furnaces.

3, gunning material

A refractory mixture used for gunning or spraying by a jet machine. According to gunning methods, gunning can be divided into wet gunning (or mud gunning), semi-dry gunning and fire gunning. Wet gunning can achieve high fog dispersion and high attach rate by spraying slurry containing 20 ~ 40% refractory powder with compressed air, and can be used for 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%, and the attach rate is low, so it can be used for gunning thicker layers. Fired gunning belongs to dry gunning, and gunning material is sent to the flame of fuel-oxygen spray gun, which is partially melted in the nozzle flame and attached to the brick lining.

The gunning materials are aluminum-silicon, aluminum-silicon-zirconium, magnesium, magnesium-calcium, magnesium-chromium and so on. The binders used are sodium silicate, phosphate, polyphosphate, asphalt, resin, etc. In order to improve attach rate, clay, bentonite, lime and other additives are added. In order to ensure good sintering of gunning materials, sintering AIDS, such as serpentine, pure olivine, lime, refractory clay and iron oxide, are also added.

4. Refractory coating

The material coated on the refractory lining. According to the different application requirements and construction methods, refractory coatings can be prepared into mud paste and mud. The binders used vary with materials, such as phosphate, polyphosphate and magnesium sulfate, which are used to prepare alkaline coatings for continuous casting tundish; Clay, aluminum dihydrogen phosphate, aluminum chromium phosphate and water glass are used to prepare high-alumina coatings. In order to improve the spreadability of coatings, plasticizers and other additives are generally added. The coating is mainly used as a protective coating for the lining of various thermal equipment, or to repair the local damage of brick lining.

5, tamping material

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

The ramming material adopts forced ramming construction, with low porosity and high density. Therefore, among unshaped refractories, ramming material is especially suitable for lining of melting furnaces and various containers containing high-temperature molten metal. Such as open hearth and electric hearth, lining of various induction furnaces, taphole of blast furnace, steel bucket, etc.

6. Projecting material

A semi-dry mud material that is projected by a projector to build a lining. It is mainly used to build the inner lining of integral steel bucket. Materials include silica, wax stone, clay, high alumina and zircon. High silica and high alumina projectiles are widely used.

7. Dry mixing

Dry mixture, also known as dry vibrating material or dry material. Unshaped refractories constructed in dry state are vibrated or rammed. Most of these materials contain some temporary binder, which is demoulded after baking.