Reasons for cracks in refractory castables after furnace baking

Furnace baking is a crucial link before the operation of refractory castables after construction, which directly determines the future service life of the kiln. When baking high-aluminum castables, furnace preparations should be made, furnace baking time should be controlled well, and the furnace heating curve, etc. need to be operated under strict conditions. Improper furnace baking operation may cause engineering quality accidents such as castable cracks.

Is it normal for castables to have cracks after furnace baking? What are the causes?

Under normal circumstances, after the furnace baking is completed, the kiln can operate normally after the project acceptance, and the castable can also achieve its own performance within the use temperature range. There are three main reasons for cracks in castables after furnace baking:

01 When the refractory castable is wet mixed, the amount of water added is not controlled well. Adding too much water will cause the castable to have insufficient bonding strength, which will cause the castable to fall off. Adding too little water will also greatly weaken the performance of the castable. Therefore, the amount of water added must be strictly controlled according to the proportion and as written in the instructions.

02 When curing refractory castables, the curing time is not enough, resulting in the strength of the molded castables not being achieved. Generally, when the temperature is high, the curing time of the castables is 24 hours, and in the colder winter, the curing time of the castables is 48 hours. Due to the low temperature, a small amount of accelerator will be added to speed up the coagulation of the castables.

03 When the castables are baked in the furnace, the temperature rises too fast. When the castables are baked in the furnace, the boiler heating curve must be controlled. When baking the furnace, the construction personnel often formulate the baking curve according to the boiler conditions. When baking the furnace, the heating temperature is strictly controlled to avoid rapid heating and rapid cooling.

After baking, if the cracks in the castables are not obvious or serious, they need to be checked in time and repaired with the same castables. Once the cracks are large or the castables fall off, the construction personnel need to solve the problems and repair them with new castables.