1. Linear change of high-strength refractory castable

The linear change rate of high-strength refractory castables is different from the re-burning linear change of shaped fired products, and the inspection method is basically the same. The volume stability at high temperature is rarely measured, and the linear change rate is generally measured, which is divided into the drying line change rate and the linear change rate after firing. The linear change rate after burning is also called the full-line change rate. Because the change rate of the drying line is small, it is often ignored.

The rate of change of the drying line refers to the ratio of the irreversible change in the length of the sample after being dried at 110°C for a certain period of time to its length before being dried, expressed as a percentage. The linear rate of change after burning refers to the ratio of the irreversible change in the length of the sample after heating for a certain time at a specified temperature to its length before heating, expressed as a percentage. The calculation result is negative, which is represented by "-", which is called linear contraction; otherwise, it is called linear expansion, which is represented by "+". The linear rate of change of the material is too large, the damage to the lining is greater, the structure is easy to peel off, and its service life is reduced. Therefore, technical measures such as additives should be adopted to minimize the linear rate of change of the material. In addition, the linear rate of change of the material is also one of the basis for kiln lining structure treatment and expansion joint retention.

2. Thermal shock resistance of high-strength refractory castables

Thermal shock resistance refers to the ability of a sample to resist rapid changes in temperature without being damaged. It is also called rapid cooling and rapid heating, resistance to rapid temperature changes and thermal stability. As we all know, during the use of materials, the increase or decrease of temperature is inevitable, causing expansion and contraction, that is, thermal stress. When the thermal stress exceeds the structural strength of the material itself, cracking or peeling occurs, and even the lining body collapses. Therefore, this performance is an important index for judging the quality of the material, and it is also one of the basis for the design and selection of materials and operation.

The thermal shock resistance is closely related to the material's chemical mineral composition, microstructure, material particles and preparation process, thermal expansion and thermal conductivity, etc. It is also closely related to the structure and strength of the material. For example, in general, the material has a large thermal expansion rate and poor thermal resistance; the higher the thermal conductivity, the better the thermal shock resistance, and so on. In general, unshaped refractories have better thermal shock resistance than shaped fired products. For example, the thermal shock resistance of CA50 cement and high alumina phosphate refractory castables are 15-20 times and 180-200 times, respectively.

3. Slag resistance of high-strength refractory castables

Slag resistance refers to the ability of a sample to resist erosion and erosion by molten slag at high temperatures. It is an important indicator to measure the resistance of materials to chemical erosion and mechanical wear. In thermal equipment such as smelting furnaces, high-strength refractory castables have been used more and more in recent years, so it is necessary to measure their slag resistance.

The slag resistance measurement methods include the melting cone method, the crucible method, the dipping method, the slag spreading method and the rotating method. Crucible slag spreading method and rotating method are widely used. Our country stipulates that the rotating method is used as the standard inspection method for slag resistance.