In the design of furnaces, the main attention is paid to the structural design, the operation of individual components of the structure and the provision of a smoke removal function. Initially, materials for the manufacture of the structure are also calculated, since the specifics of its operation determines stringent requirements for the characteristics of the unit. At the same time, the base material is far from always able to cope with the thermal effects that a particular furnace is designed for. Lining, as a technological operation of additional processing, allows both minimizing thermal negative factors and preventing mechanical damage to the structure.
When is lining done?
The initial choice of building material for the technical implementation of the structure is made taking into account its ability to cope with operational loads. As noted above, basic characteristics are not enough. It is necessary to use additional thermal insulation materials in some cases associated with an increase in temperature loads on the surface of the structure. In particular, this applies to furnaces designed to operate in long-term combustion modes. Also, elevated temperatures give high-calorie fuel, although such unitsrarely used and mainly in enterprises.
As for household stove structures, they usually do not require additional protective coatings, but only if we are talking about small and medium-sized structures. The situation is different if a massive Russian stove is considered. The lining in this case allows you to protect functional areas that can also be used for cooking.
Main lining materials
Refractory fireclay bricks are considered a classic material for lining stoves. With its help, an external shielded protection is formed. This option is suitable for sauna stoves that require some kind of complete thermal insulation. In the usual version, the refractory lining with fireclay is a lining of the furnace part in order to protect against elevated temperatures.
As technology has developed, other means of protecting furnace structures have emerged. So, if earlier concrete mortars were prepared, from which ordinary plaster was later laid, then in its modern form the same method looks somewhat different. The main difference is that the mixture is applied to a hot surface using shotcrete technology. That is, heat-resistant concrete is applied to the target surface in layers using compressed air-based pneumatic tools.
Roll lining
The fundamental difference from classic coatings and masonry withroll coatings have a thermal insulation function. First, they are easy to apply. Secondly, the coating takes up a minimum of space, increasing the thickness of the structure by no more than 1 cm. For comparison, heat-resistant concrete in the form of plaster increases the thickness of the walls of the furnace structure by 1-2 cm, and a brick can reach 10 cm in this indicator. presented in several forms, usually on a flame-retardant paper base.
The most widespread in this segment is mullite-silica kaolin wool, which is obtained by melting silicon and oxide in an electric furnace. In practice, it is noted that this material has low thermal conductivity and at the same time increased thermal stability. Also, kaolin thermal insulation materials are not destroyed by chemicals, for which they are valued in industrial production.
Induction furnace protection features
To begin with, it should be noted that the need to perform lining of induction furnaces arises not because of the weakness of the structure before thermal shocks, but because of the specifics of their application. Such units are used for melting metals at high temperatures, therefore, special means in the form of dry mixtures are used to protect them. In essence, this is a classic coating, but the composition for the mass is fundamentally different from concrete mortars. Thus, the lining of induction furnaces, which melt low-alloy and carbon steel, involves the use of spinel-forming masses. The latter, by the way,are resistant to slag formation. Units for melting cast iron are treated with quartzite compositions, and if non-ferrous grades with steel are added to this metal, then technologists add mullite-forming components to the lining recipe.
Execution technology
There are different lining techniques and approaches that differ in surface coverage and insulating material application. Protective lining can be external and internal. The outer lining is usually applied over the entire height - from the bottom to the crowning edges. Interior decoration may provide for the protection of work surfaces in contact with both direct flame and smoke in the form of high-temperature exhaust gases. The greatest effect is given by protection circuits that comprehensively isolate the furnace. Lining is carried out only on cleaned surfaces. Preparation of the material, as a rule, involves the dilution of active substances in solvents. In this way, a mixture for coating is formed, which is applied to the surfaces of the structure using traditional facing tools. Brick, in turn, is laid according to standard schemes in accordance with the requirements for the protection of structures.
Conclusion
Outer coatings of ovens must not only provide resistance to thermal effects, but also provide protection from other factors. For example, in the conditions of industrial premises, the risk of mechanical influences to whichbake. The lining in this case also involves the fulfillment of the tasks of physical protection of the structure. Therefore, special plasticizers can be added to the mixture, modifying the strength properties of the composition. But this applies only to the means of creating external thermal insulation, and internal coatings are fully oriented towards the formation of effective temperature screens.
