The analysis of crack of castable when heating-up

Oven drying is a crucial link after the construction and before the operation of high alumina castable, which directly determines the future service life of the kiln. When baking high alumina castable, it should be prepared for oven drying, the oven drying time should be controlled, and the furnace temperature rise curve should be operated under strict conditions. If the furnace drying operation is not standardized, there may be engineering quality accidents such as castable cracks.

Is it normal for castable to crack after oven drying? What are the causes?

Under normal circumstances, after the completion of drying, the kiln can operate normally through project acceptance, and the castable can also achieve its own performance within the service temperature range. There are three main reasons for cracks in castable after oven drying:

1、 During wet mixing and mixing of high alumina castable, the amount of water added is not well controlled. Excessive water addition leads to insufficient bonding strength of castable, resulting in falling off of castable. Too little water addition will also greatly weaken the performance of castable. Therefore, the amount of water added must be strictly controlled according to the proportion and in accordance with the instructions.

2、 During the curing of high alumina castables, the curing time is not enough, resulting in the failure of the strength of the formed castables. Generally, when the temperature is high, the curing time of the castables is 24 hours, while in colder winter, the curing and sweeping time of the castables is 48 hours. Between the lower temperature, a small amount of coagulant will be added to speed up the setting speed of the castables.

3、 When the castable is baked, the temperature rises too fast. When the castable is drying out, the boiler temperature rise curve must be controlled. When drying the furnace, the construction personnel often formulate the drying curve according to the boiler situation. When drying the furnace, strictly control the heating temperature to avoid rapid heating and cooling. After oven drying, if the cracks of the castable are not obvious or serious, it needs to be checked in time and repaired with the same castable. Once the cracks are large or the castable falls off, the construction personnel need to make solutions to the problems and repair them with new castable.

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