Heating furnace, that is, the whole process of drying and heating and temperature raising for the lining of industrial electric furnace after completion or maintenance according to the temperature raising curve in the design scheme: cooling furnace is the whole process of temperature reduction for the applied furnace according to the temperature reducing curve in the design scheme. The speed of elevator heating rate depends on the structure of furnace, the relevant characteristics of common refractory materials and the strength of heating and refrigeration equipment. Therefore, the heating furnace and cooling furnace are not the longer the better, but an effective upper and lower temperature rules and regulations must be formulated.

For the fireproofing brick masonry furnace, when heating the elevator, we must pay special attention to the symmetry of heating or cooling and the temperature field in the thin and thick direction of the infilled wall, so as to avoid too large difference in volume due to too fast heating or too high temperature, resulting in structural stress damage.

For the furnace built with amorphous refractory materials, the same attention should be paid to the fireproof brick masonry in the whole process of temperature reduction and refrigeration: for the whole process of heating and temperature rise, special attention should be paid to the discharge rate of water in the engineering construction body and the solidification rate of the external surface in the whole process of temperature rise. When the internal water discharge rate is less than the internal water volatilization rate, the saturated vapor pressure in the amorphous refractory construction body increases. When the internal steam pressure reaches or exceeds the compressive strength of the infilled wall, cracks will gradually occur inside the steam body, which will cause cracking when it is more serious.

1: Some difficult problems that must be avoided in the work of heating furnace

(1) Cracking of fireproof concrete

(2) Accumulation of water vapor

(3) Anti cracking

(4) Partial in-situ stress and reflective failure

(5) Steam and solidification

(6) Shedding of amorphous and unburned refractories

2: The unreasonable temperature of the elevator is very easy to cause the problem of centralized rate structure damage.

(1) Anti cracking, to put it bluntly, thermal cracking means that when the refractory is subjected to rapid cooling and heating, the temperature difference is caused on the surface and inside of the refractory. Due to the existence of the difference, the in-situ stress is formed inside the refractory infilled wall. The cracking generated after the local stress accumulates to a certain level is thermal cracking.

(2) The minerals that make up silicon carbide bricks are Sima Xiang, such as quartzite, scaly quartzite and cristobalite. At the same time, with the compound conversion of quartzite, the volume produces gene mutation. When heating or cooling silicon carbide bricks construct infilled walls, attention must be paid to the problem of thermal cracking.

(3) Magnesia brick or magnesia chrome brick is easy to form thermal cracking due to its large linear expansion coefficient and temperature gene mutation.

(4) Because of its low specific heat, large temperature field in the brick body and low relative compressive strength, the thermal insulation board is also easy to cause cracking problems.

(5) Reflective cracking, to put it bluntly, refers to the situation that the thermal deformation and in-situ stress caused by insufficient swelling capacity or partial high temperature in the heating of arc and other special structural forms, resulting in the influence of in-situ stress on the overall structure. When the insulating brick furnace body and the rotary kiln are heated by a single layer, at the same time of temperature rise, different temperature positions cause different surge. Therefore, the insulating brick suffers from the punching machine adjacent to the insulating brick. When the working pressure exceeds its compressive strength, the brick body will be damaged. Such damage usually occurs first on the hot surface.

(6) Tectonic collapse. When the refractory is applied in the high-temperature natural environment, the heating surface is usually adhered with coal ash and other residues. Because of their adhesion and infiltration, a mildew layer is produced around the heating area of the refractory. Because this moldy layer will collapse due to vitrification or fall off due to thermal deformation, this kind of situation is called structural collapse.