Construction characteristics of refractory plastics

February 15, 2022

     The lining of the walking beam heating furnace is the main structural part that bears the heat load, and its construction quality plays a key role in the heating furnace reaching the design thermal index. With the application of new refractory materials and the complexity of furnace design, the construction difficulty is becoming more and more difficult, which poses a greater challenge to the quality control of furnace lining construction. At present, many large-scale walking beam heating furnaces in China use refractory plastics as the refractory layer in the heating furnace.


     Refractory plastics are refractory aggregates, powders, binders and additives with a certain particle gradation, which are prepared, mixed with water (or liquid containing binders), and extruded into lumps or mud-like materials. It still has good plasticity after being packaged and stored for a certain period of time. It can be constructed by ramming method. It is mainly used in various heating furnaces, soaking furnaces, annealing furnaces, sintering furnaces and electric furnace roofs in the iron and steel industry. lining. Plastic has the advantages of high high temperature strength, good thermal shock resistance, low thermal conductivity, strong spalling resistance and slag resistance, long service life, energy saving, etc. It is especially suitable for furnace roofs, burner bricks, etc., which are easily damaged. And the parts that are not easy to form. 


     Refractory plastics are gas-hard or thermo-hard materials. The water content in the plastic is less, and it will harden after being exposed to the air for a short time, so the joint surface should be continuously constructed during construction. The plastic blocks must be combined with a certain external force, which needs to be perpendicular to the construction surface.


    When the plastic is used on the top of the furnace, because the furnace roof adopts a hanging structure, the refractory material is suspended by the anchoring bricks to form a whole, and it is required that the plastics and the anchoring bricks must be tightly combined. The anchoring bricks are hung on the steel structure of the furnace roof. During the construction process, each anchoring brick must be prestressed, so as to ensure that the stress surface of the furnace roof is uniform and does not collapse. In the process of combining with external force, the plastics will inevitably expand around, and the thickness of the furnace roof cannot be guaranteed. This requires that templates should be set on the upper and lower sides of the furnace roof, so that the thickness of the plastics can be controlled within the required range. .


     Plastics will shrink at high temperatures, so there is no need to leave expansion joints in the traditional way. However, in order to prevent horizontal cracks after the material shrinks, the method of slitting can be used in the construction process to control the expansion and contraction during drying and heating.


    The processed plastic surface is smooth, which is not conducive to bonding. Pay attention to make the bonding surface as rough as possible. In order to ensure ventilation, the outer surface should be rough after construction, and foreign objects should not be smeared or processed with a trowel.

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