How to Select Refractory Castable?
Refractory castable products have acid resistant high temperature environment, alkali resistant high temperature environment and medium high temperature resistant environment, in addition to low cement, ultra low cement, phosphate combined, water glass combined casting refractory, alumina Magnesia, alumina silicon carbide carbonaceous products, including wear resistant refractory, lightweight insulation, steel fiber reinforced refractory castables, etc. In addition to the use temperature of the equipment, the refractoriness is not an indicator of the choice of refractory products, but only to test the purity of the raw refractory materials and the degree of refractory. Only refractory products that meet the requirements of use can be selected to achieve the ideal operating life of the lining.
How to Ensure Quality of Refractory Castables
According to the specific use part of the high temperature furnace, select the appropriate refractory castable, including the working temperature of the furnace, Refractory castable of the material selected in the working environment, and consider whether the working temperature of refractory castable and the various indexes reach the use of the high temperature furnace.
Refractory Castables Service Life Affecting Factors
1. Moisture content in the construction of refractory castables
Controlling the amount of water added is the key to ensuring the strength of the refractory castable. The factors affecting the amount of water added during actual construction are the mixing time and the level of vibrating technology. When mixing, generally use a forced mixer, should be dry and evenly mixed, then add water about 80% to stir the water, until the fluidity meets the requirements of vibration, the total time should be no less than the amount of water to start to play after stirring.
The level of vibration also affects the amount of water added. Unskilled vibrators, in order to resonate the slurry layer, require high fluidity of the slurry, and increase the amount of water added under the same conditions. Therefore, the amount of water added should be strictly controlled during the construction of the refractory castable, and the skilled vibrator should be arranged for construction. To lay the foundation for the excellent performance of castables.
2. Anchor Design and Construction Quality
For refractory castable linings, the anchor is the basis for its attachment to the casing. Its design and construction quality directly affect the service life of refractory castables. In the production, the problem of improper selection of anchor materials or too small design equivalent diameter is often encountered, which may make the anchors unable to withstand the force of refractory castables at the use temperature. Softening and deforming, causing an accident of collapse.
Similarly, if the anchor arrangement is too dense or the expansion joint is too small, internal stresses may occur due to thermal expansion mismatch between the refractory castable and the anchor during heating, which may cause loose flaking of refractory castable. Therefore, when designing and constructing anchors, refractory materials, forms and arrangements should be selected according to the specific conditions such as the temperature, thickness and location of refractory castables, and the anchor expansion joints and welding quality should be handled.
3. Maintenance of Refractory Castables
Maintenance is one of the most important factors affecting the performance of castables and one of the most overlooked factors. The curing is to give the bonding agent in the castable a solidification and hardening time to obtain sufficient initial strength. The maintenance system is related to the type of binder of the refractory castable.
The mold curing time and mold release curing time of castables should meet the requirements of the specification. Generally, in the case of ambient temperature 5 °C ~ 35 °C, the mold curing time is not less than 24 hours, and the mold release curing time is not less than 24 hours. Ensure the early strength of the castable.
4. Baking of Refractory Castables
Baking is the most direct and critical factor affecting the performance of refractory castables. Baking is to eliminate more free water and chemically bound water. Properly baked, can improve the service life of refractory castables,however, if the baking is not proper, the temperature rises too fast, and the refractory castables may be cracked, peeled off or even burst due to unsatisfactory moisture removal.
Refractory castable must be baked before use. The baking should meet the baking system to ensure that the free water and crystal water in the rtcastable can be fully discharged, so as to avoid the phenomenon of “peeling and bursting” in the early stage of feeding or use. The normal use of refractory castables. For some special parts, it is best to perform separate baking before the whole baking. For some key parts (such as the front kiln mouth, kiln hood, heat section of the cooler, etc.), bamboo chopsticks can be used to reserve the vent hole.
