The refractory materials for different parts of the step heating furnace must have chemical indexes

Walking beam type steel rolling heating furnace refractory materials are generally castables, plastics mostly, the top of the furnace using hanging structure, the use of anchored bricks plus plastics, close to the parts of the furnace shell steel plate using adiabatic refractory materials, such as lightweight insulation bricks, calcium silicate panels, ceramic fiber blankets and other materials. Hot rolling high-temperature step heating furnace refractory materials used must be considered its performance to use the production of high temperature requirements, such as columns, step beams, the bottom of the refractory castables used with the furnace wall, the top of the furnace can be used plastic, are in direct contact with high temperature environment, in addition to a large number of iron oxide-containing slag adherence and erosion, and therefore with the ordinary heating furnace should be differentiated. Chemical indexes of several refractory materials used in step heating furnace:

1、Analysis of refractory materials for columns and step beams

The walking beam and the column are seriously slag-stained. When the deformation is 0.6%, the load softening temperature of the column and the walking beam castable is 1319℃, while when the deformation reaches 2%, it is only 1342℃. This temperature range is very narrow, but the deformation is large. Such performance will cause the surface of the column to soften, and the liquid phase in the castable increases, which is easy to adhere to the iron oxide scale falling from the steel billet, and it is also easy to react with the iron oxide scale to form a sticky slag. From the structural analysis, the surface slag has a high aluminum content in China, which is estimated to be related to the corrosion reaction between iron oxide and refractory materials. The viscosity of the iron oxide solid solution containing aluminum oxide increases, which is easy to stick to slag.

2.Analysis of refractory materials for furnace walls and bottoms

Deformation of the furnace wall, narrowing in the middle and widening at the bottom, prone to cracking: a large amount of iron oxide slag accumulation at the bottom of the furnace, affecting production.

Deformation of 0.6% of the furnace wall, the bottom of the furnace pounding material of the load softening temperature of 1213 ℃, deformation of 2% of only 1392 ℃, the same will cause the furnace wall, the bottom of the sticky slag. Deformation of 0.6% of the furnace bottom castable weight softening temperature of 1324 ℃, deformation of 2% of only 1352 ℃, if the deformation increases, for the safe use of the kiln is not good. Deformation of 0.6% of the bottom of the furnace using magnesium-chromium castables load softening temperature of 1239 ℃, deformation of 2% of only 1451 ℃, the load softening temperature has increased, so the pad supplement magnesium-chromium castables conducive to the protection of the bottom of the furnace, the furnace wall for the safe use of the kiln is advantageous, the amount of deformation of 0.6% of the load softening temperature needs to be further improved in order to control the amount of liquid phase to reduce the slag adherence.

3.Analysis of refractory materials for dikes and burners

The embankment was seriously clogged with slag, which hindered the travel of the pillars. The embankment also cracked and was easily damaged during the slag removal. The performance of the ramming material used is shown in Table 4. The load softening temperature of the ramming material for the dike is 1222℃ when the deformation is 0.6%, and it is only 1517℃ when the deformation is 2%. The deformation temperature range is relatively wide, and the temperature at which deformation begins is low. The deformation reaches 0.6% from 1222℃. The ramming material is easy to soften and the slag sticking is more serious. The ramming material around the burner is in a relatively stable shape with less sticky slag, indicating that the performance of the furnace lining material used is good. The inward collapse and cracking of the furnace wall are related to the performance of the ramming material. When the deformation is 0.6%, the load softening temperature of the burner plastic is 1316℃, while when the deformation reaches 2%, it is only 1568℃. This temperature range is relatively large, and the increase in load softening temperature is beneficial to reducing slag sticking.

From the damage investigation and refractory performance analysis, it can be seen that the general contractor design unit is not clear about the changes and requirements of the refractory performance required for high-temperature heating furnaces. They generally focus on performance indicators such as compressive strength, flexural strength, bulk density, and linear change rate after high-temperature firing. However, judging from key performance indicators such as the refractoriness under load, the refractory material is of low quality and the kiln is prone to slag sticking. Therefore, it is necessary to change the selection of furnace refractory materials according to the user's process characteristics.

Walking Beam Heating Furnace