What Influence the High-temperature Structural Strength of Refractory Materials?

High temperature structural strength refers to the ability of refractory products to withstand pressure at high temperatures without deformation.It is evaluated by refractoriness under load. The so-called refractoriness under load refers to the temperature at which the refractory material begins to deform and the compression deformation reaches 4% or 40% when the refractory material is heated at a certain heating rate under a pressure of 0.2MPa. The former temperature is called the starting temperature of load-bearing softening, and the latter is called the softening point of 4% or 40% of load-bearing softening.

The compressive strength of refractory materials at normal temperature is very high. However, it does not work at high temperatures. This is because the fusible components inside the refractory bricks melt prematurely and form a liquid phase, which greatly reduces the compressive strength at high temperatures.

In addition to bearing high temperatures, refractory materials also bear load in the kiln masonry. Therefore, the high-temperature structural strength of refractory materials is the main indicator for judging the quality of refractory materials.

1: High-temperature load deformation temperature, that is, the temperature at which refractory products undergo a certain amount of deformation and collapse when they are continuously heated under a certain pressure.

2: High temperature mechanical strength, that is, the maximum compressive stress that refractory products can withstand at a certain measured temperature.

Factors affecting load softening temperature (high temperature structural strength)

Different types of refractory products have different softening temperatures under load, and their softening characteristics are also different.

Item Refractoriness under Load(℃)

Fireclay Brick 1250~1400

High Alumina Brick 1400~1530

Silica Brick 1620~1650

Magnesia Brick 1470~1500

The load deformation of clay bricks from the beginning to failure has a wide temperature range, while that of silica bricks is very small. This shows that the main factors that affect the softening temperature under load are the chemical mineral composition, crystal structure, number ratio of phases and the liquid phase viscosity when they melt. Therefore, we improve the purity of raw materials during the production process, increase the firing temperature to promote crystal condensation and growth, and add additives to improve the crystal structure to increase the load softening temperature. In addition, increasing the molding pressure promotes compactness of the product, and increasing coarse particles can also increase the starting deformation temperature.