Mud-shaped or mud-shaped unshaped refractories constructed by ramming, shaking or extrusion methods. It is fully mixed with a certain grade of refractory aggregate, powder, binder, admixture and water or other liquids. According to the quality of refractory aggregate F, it is divided into: clay, high alumina, corundum, siliceous, magnesia, chromium, zircon and silicon carbide refractory plastics, etc. According to the type of bonding agent, it is divided into: water glass, phosphate, sulfate and organic bonding agent, fire-resistant plastic, etc.
According to the hardening method, it can be divided into two types: air-hardening or thermosetting,
refractory and plastic.
Refractory plastics usually use Al2O3-SiO2 aggregates. The main consideration when choosing the material is the volume stability of the material, a certain degree of water absorption, and the clay clinker, sintered alumina, fused alumina, etc. that can be sintered well with the cementing material. material. Bonded clay is usually an important raw material for plastics, which directly affects the performance of plastics. In addition to requiring good plasticity and bonding, attention should be paid to the sintering performance and alkali content indicators of clay. The plastic is mixed with a certain amount of raw clay, and the furnace body built with it shrinks when it is dried, and further shrinks after heating and cooling. If the shrinkage is too large, the furnace body will be damaged. The volume expansion caused by the secondary mulliteization at high temperature cannot offset the shrinkage caused by the raw clay. Therefore, an appropriate amount of expansive material, such as fine kyanite powder, is often added to the plastic. When kyanite begins to decompose to form mullite and quartz at 1300°C, a volume expansion of 10% to 12% occurs sharply to offset the high temperature shrinkage of the plastic matrix part. However, drying shrinkage still exists, so adding an appropriate amount of ultra-fine barren raw materials, such as fine powders such as quartz and fused alumina, to replace part of the clay, which is beneficial to reduce shrinkage and improve high-temperature load performance.
The plastic can be extruded or compacted into a block, and it can be properly tamped and trimmed during use. The plastic has a uniform porous structure, good thermal shock resistance, and high temperature strength.
Corundum plastic is a kind of plastic in which corundum is used as aggregate and powder, and clay and phosphoric acid mud are used as binder. Clay-phosphoric acid mud is prepared by using 25% orthophosphoric acid and soft clay in the ratio of 84:16 and boiled for 5 minutes. The plasticizers used in it are sulfite alcohol waste liquor, cycloethane acid, paraffin oil, lignosulfonate, lignin phosphate, lignin chromate and colloidal bentonite, etc.
The use temperature of such plastics depends on the alumina content in the aggregate, which is generally above 1350~1500°C. The higher the alumina content in the corundum aggregate, the better the fire resistance.
