What is the high temperature volume stability of refractories?

High temperature volume stability refers to the performance of refractory materials that remain stable without change (shrinkage or expansion) due to the effect of heat load during use. For fired refractory products, it is usually expressed by the heating volume change rate or heating permanent linear change rate of the product under no heavy load; and for unburned refractory materials (mainly unshaped refractory materials), the heating line change rate is usually used To represent.

The permanent linear change rate of heating refers to the residual expansion and contraction of the fired refractory product after being heated to a specified temperature, holding it for a certain period of time, and cooling to room temperature. The heating permanent linear change rate is an important index for evaluating the quality of refractory products. It is of great significance to determine the high-temperature volume stability of the product, thereby ensuring the stability of the masonry, reducing the gaps of the boron building, improving its sealing and corrosion resistance, and avoiding the destruction of the overall structure of the masonry.

The heating permanent linear change rate of dense shaped refractory products shall be determined in accordance with the national standard GB/T5988-2007 Dense shaped refractory product heating permanent linear change rate test method.

The heating line change rate of monolithic refractories includes the drying line change rate and the line change rate after firing. The drying line rate of change refers to the ratio (%) of the irreversible change in length of the sample after drying at (110+5)C for a certain period of time, and the length of the sample before drying (%). The amount of irreversible change in length after heating and holding for a certain period of time at a specified temperature is expressed by the change in sample length (%). The rate of change of heating line of monolithic refractories is a very important performance index. If the linear change rate is too large, it will be very destructive to the masonry lining, and it is easy to cause structural peeling or reduce the compactness of the lining, thereby reducing other properties such as erosion resistance and reducing the service life of the lining.

The rate of change of heating line of unshaped refractories shall be determined in accordance with the test method of the rate of change of the line of ferrous metallurgy standard YB/T5203-1993 dense refractory castables.