Influencing Factors of True Density of Silica Brick

True density is an important parameter of refractory materials. The value of true density can reflect the phase composition of the material and the purity of the raw material. For silica bricks, true density is particularly important. The true density is the key factor that determines the thermal stability of the silica brick. The true density is one of the important signs to determine the degree of conversion of the silica brick quartz. The smaller the true density of the silica brick, the more complete the quartz conversion, the smaller the residual expansion during the oven process, and the more stable the performance of the silica brick.

RS High Quality Silica Refractory Brick
RS High-Quality Silica Refractory Brick

Testing principle of true density of silica brick

Crush and grind the sample so that there are no closed pores as much as possible, measure its dry mass and true volume, and then measure the true density. The volume of fines is measured with a pycnometer and a liquid of known density. The temperature of the liquid used must be controlled or carefully measured.

Influencing factors of true density of silica brick

To understand the influencing factors of the true density of silica bricks, it is necessary to test the true density of silica bricks. Only in the experiment can we better discover the factors that affect the true density of silica bricks. The following are the factors that influence the true density of the resulting silica bricks.

  • Mineral phase composition

The silica in the silica brick exists in the form of three mineral phases, namely quartz, cristobalite, and scaly quartz. The true density of the three mineral phases is different, with scaly quartz being the smallest, cristobalite second, and quartz the largest. If the true density of the silica brick is small, it means that the quartz is converted into scale quartz and cristobalite during firing, the residual quartz is less, the high-temperature volume stability is good, and the re-expansion during use is small. Therefore, the true density of silica brick is an important technical indicator to measure the degree of quartz transformation, and also a key indicator to characterize the quality of silica brick products.

The relationship between the phase composition of silica brick and the true density. The decrease of phosphorus quartz content and the increase of quartz content will lead to an increase of the true density of silica brick. Therefore, in the production of silica bricks, the content of residual quartz should be strictly controlled to reduce the true density of silica brick products.

  • Wetting liquid

Different infiltrating liquids contain different impurities, different infiltrating capabilities, and different reactions between the sample and the liquid molecules, resulting in deviations in the true density test results.

  • Test temperature

When the pycnometer is placed in a constant temperature water bath, due to the different expansion coefficients of the container and the liquid, the fluctuating temperature will cause the degree of the overflow of the liquid in the pycnometer. The weighing result will change, which will affect the true density test result. Therefore, when placing the sample in a constant temperature water bath, the temperature of the water in the constant temperature water bath must be strictly controlled within 2°C±0.2°C higher than room temperature.

  • Vacuum

During the test, the pycnometer containing the sample and the infiltrating liquid should be placed in a vacuum device with a certain residual pressure for degassing to ensure that the infiltrating liquid can completely wet the sample. During the vacuuming process, the residual pressure is too large or too small will affect the true density test results.

It can be seen from the experiment that when the pressure is too small, the air in the sample cannot be completely discharged, and there is unexhausted gas in the powder particles of the sample, which leads to the reduction of the drainage volume, thereby overestimating the volume of the sample and ultimately causing the true density. The calculation result is too small. On the contrary, when the pressure is too high, the sample may be splashed during the vacuuming process, resulting in a loss of sample quality, and the true density test result will be small.

Application of silica brick

Silica brick has been used for more than 100 years. It is mainly used to build the partition walls of the carbonization chamber and combustion chamber of the coke oven, the roof and wall of the glass pool kiln, and the firing kiln of silicate products. In order to improve the production capacity of modern large-scale coke ovens, it is necessary to thin the furnace wall openings of the coking oven carbonization chamber and combustion chamber. Therefore, refractory bricks manufacturers are required to develop a silica refractory brick material with high density, high thermal conductivity, high-temperature strength, and good thermal shock resistance. Buy high-quality silica bricks, Rongsheng refractory manufacturers will provide you with high-quality silica brick products.

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