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Brief introduction to bell - type furnace
Bell - type furnace is used for bright annealing and heat treatment of workpiece equipment, belongs to the intermittent variable temperature furnace, furnace temperature in 650 ~ 1100 ℃, according to the provisions of the heating system changes with time. According to the loading of bell-type furnace, the furnace is divided into two categories: square bell-type furnace and circular bell-type furnace. The heat source of bell-type furnace is mostly gas, followed by electricity and light oil. Generally consist of an outer cov, an inner cover and a furnace platform, wherein that combustion device is mostly arranged on the out cover, the outer cover is provided with a heat insulation layer, and a workpiece is generally arranged in the inner cover for heating and cooling.
The advantages of heat preservation of bell-type furnace: good air tightness, small heat loss and high heat efficiency of furnace. Secondly, that furnace doe not need a furnace door, a lifting mechanism and various mechanical transmission mechanism, and the cost is low. Therefore, in the heat treatment furnace of the workpiece, the bell-type furnace is widely used.

Selection of refractory material for bell-type furnace
Selection and restriction points for heat preservation and refractory materials of cover type bright annealing furnace;
The heating hood is usually steel frame, so lightweight and energy saving are the two most critical requirements for lining materials. 
1. the traditional refractory material density is larger ( insulating brick more than 600 kg / m3, light castable more than 1000 kg / m3 ), the load requirements on the furnace cover steel structure is also large, steel structure consumption is high, increase the investment in furnace building. 
2. the cover is too heavy, also affect the lifting capacity of the production workshop and covers an area of. 
3. the bell-type furnace belongs to intermittent variable temperature operation furnace. the specific heat capacity of insulating brick and light castable is large, the thermal conductivity is large, and the energy consumption is serious.
Cover heat treatment furnace heat preservation, ceramic fiber material shortlisted advantages:

　　

The density is low, and that consumption of the steel structure is reduce; 
The heat capacity is small, and the energy consumption is saved;
Low thermal conductivity, low heat storage capacity and low bulk density are the basis of its wide application in heating mantle. _
Ceramic fib lining heat insulation structure for hood body of bell-type furnace
The following aluminum silicate ceramic fiber insulation structures can be adopted for high-temperature heat insulation of bell-type furnaces, heat insulation of bell-type bright annealing furnaces, fire insulation of bell-type resistance furnaces, heat insulation of rectangular gas bell-type furnaces, and heat insulation of moving bell-type furnace refractory linings, etc.
The common lining structure of the heating cover is a composite structure of a ceramic fiber module and a layer blanket
Material selection: ceramic fiber module hlgx - 489, bulk density of 220 kg / m3 + ceramic fiber blanket hlgx - 422;
Total insulation thickness: 330 or 350 mm, ceramic fiber module 300 mm, backing layer ceramic fiber blanket 30 or 50 mm;
Heating mantle burner zone: this zone uses ceramic fiber modules and ceramic fiber blankets of one grade higher than the lining.

Technical advantage
The fiber lining of the bell-type furnace adopts a layer paving - module composite structure, so that the steel consumption is saved at first, and the overall cost of the lining can be reduced; secondly, the anchoring element is positioned between the ceramic fiber layer paving blanket and the ceramic fiber module, so that the long-term service life of the anchoring element can be ensured; and thirdly, the fiber direction of the ceramic fiber blanket is vertical to the folding direction of the ceramic fiber module, so that the sealing effect can be effectively improved.