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The Correct Baking After The Construction Of The Tundish With Refractory Material Should Be Done!
Dec 17, 2018

Received technical consultation from a kiln construction company. During the baking process of the tundish for the construction of a steel factory in Tangshan, the construction unit produced a “beep” gun sound in the permanent layer of high-alumina refractory castable. Through inquiry and communication, it was found that the main reason for this was the improper baking of the lining.


In previous technical articles, we have repeatedly emphasized the importance of baking throughout the construction process. The tundish is applied to the refractory material. The application of the refractory castable is more, the construction body is large, and the moisture is not easily discharged. Baking time usually takes seven days. In principle, the tundish that has reached the service temperature after baking can be put into use.


Tundish


However, in actual operations, heating up too quickly has become a common problem in the industry, and workers are often eager to achieve, not in accordance with the designed heating curve. In the oven, the temperature rises rapidly, and the evaporation rate of the surface of the refractory castable is too fast, so that the drying is faster, and the water vapor generated by the internal moisture is not discharged in time. A large amount of steam and helium gas could not be discharged to form a destructive steam pressure, and the sound of the guns heard by the construction workers at the beginning appeared.


Once this happens, the castable will crack and even burst and fall off due to shrinkage. The compactness and strength properties of the construction body were seriously degraded and could not be expected. Ultimately affect the life cycle of the tundish.


So how to bake the high-alloy refractory castable for the permanent layer of the tundish is the most correct?


The oven curve of the refractory castable is mainly set according to the kiln structure, refractory castable properties, lining thickness and water consumption. The tundish mainly has a rectangular tundish and a triangular tundish. Among them, the rectangular tundish is widely used. The refractory castable used in the permanent layer of the rectangular tundish is generally a high alumina refractory castable and a mullite self-flow castable. The specific tundish oven scheme is as follows:


Tundish oven system


The entire oven solution is based on the expansion characteristics of all refractory materials in the kiln, especially before 300 °C. This is mainly because the water becomes water vapor at 110 ° C. At this stage, the amount of dehydration of the material is large, the dehydration speed is fast, and the influence on the material is also the greatest.


In the process of the oven, the oven principle of “slow heating, no turning back” must be implemented. In the whole process, the furnace temperature can only rise and fall. If the temperature rises too fast, it will only keep warm or slow down the heating rate, and it is strictly forbidden to rise and fall sharply; if the temperature rises to the day's plan, don't rush to catch up with the plan, and should approach the planned value slowly.


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