During the baking process of the tundish construction of a steel plant, the high aluminum refractory castables on the permanent of the tundish appeared the sound of “bang bang bang”. The main reason for this was that the lining was improperly baked. The tundish in the allocation of refractory materials, the refractory castable is more widely used, the construction volume is large, and the moisture is not easily discharged. It usually takes seven days to bake. In principle, the tundish that has reached the service temperature after baking can be put into use.    

However, in the 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, when 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 water vapor 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 meet the expected. Ultimately affect the service life cycle of the tundish.

So how to bake the high aluminum 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 have rectangular tundish and 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-flowing castable.

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

In the process of the oven drying, the oven principle of “slow heating, no turning back” must be implemented.In the whole process, the furnace temperature can only rise but not fall. If the temperature rises too fast and exceeds the daily heating plan, 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 less than the day's plan, don't rush to catch up with the plan, and should approach the planned value slowly.