Thermal shock resistance refers to the ability of refractory materials to resist damage caused by rapid changes in temperature. It has been called thermal shock stability, thermal shock resistance, temperature sudden change resistance, and rapid cold and heat resistance.
The thermal shock resistance should be determined according to different requirements and product types according to the corresponding test methods. The main test methods are: ferrous metallurgy standard T376.1-1995, thermal shock resistance test method for refractory products (water quench method), Ferrous metallurgy standard YB/T376.2-1995 Refractory product thermal shock resistance test method (air quenching method), ferrous metallurgy standard YB/T376.3-2004 Refractory product thermal shock resistance test method Part 3: Water quench-crack Judgment method, ferrous metallurgy standard YB/T2206.1-1998 refractory castable thermal shock resistance test method (compressed air flow quenching method), ferrous metallurgy standard YB/T2206.2-1998 refractory castable thermal shock resistance test method ( Water quench method).
The mechanical properties and thermal properties of materials, such as strength, fracture energy, elastic modulus, linear expansion coefficient, thermal conductivity, etc., are the main factors that affect their thermal shock resistance. Generally speaking, the smaller the linear expansion coefficient of the refractory material, the better the thermal shock resistance; the higher the thermal conductivity (or thermal diffusion coefficient) of the material, the better the thermal shock resistance. In addition, the particle composition, density, pore size, pore distribution, and product shape of the refractory material all have an impact on its thermal shock resistance. The presence of a certain number of micro-cracks and pores in the material is conducive to its thermal shock resistance; the large size and complex structure of the product will cause serious uneven temperature distribution and stress concentration inside it, reducing thermal shock resistance.
High-temperature volume stability means that during the use of refractory materials, due to the effect of heat load, its external volume or linear dimension remains stable and does not change (shrinkage or swelling performance. For fired refractory products, the products are usually used without heavy load. The following heating volume change rate or heating permanent linear change rate is expressed; and for unburned refractory materials (mainly amorphous refractory materials), it is usually expressed by the heating linear change rate.
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, so as to ensure the stability of the masonry, reduce the gap of the masonry, improve its sealing and corrosion resistance, and avoid 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 products 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 rate of change of the drying line refers to the drying of the sample at (110+5)℃ for a certain period of time
After that, the ratio of the irreversible change in length to the length of the sample before drying (%). The linear change rate after burning means that the length of the sample is irreversible after being heated at a specified temperature and kept for a certain period of time.
The amount of inverse change is expressed by the change in sample length (%. The heating line change rate of unshaped refractories is a very important performance index. If the line change rate is too large, it will be very destructive to the masonry lining. It is easy to produce structural peeling or reduce the compactness of the lining body, thereby reducing other properties such as erosion resistance and reducing the service life of the lining body.
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.
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