Refractory impregnation is to put refractory products or prefabricated parts into a solution or suspension, so that the solution or suspension penetrates into the pores of the refractory products or prefabricated parts, plug the pores, reduce the porosity or reduce the pore size, make the products dense, increase the strength, and better resist erosion.
The early refractory impregnation technology was called oil impregnation. Dolomite bricks were impregnated with tar pitch and used in the Thomas converter steelmaking industry. With the improvement of impregnation technology, the scope of refractory impregnation is constantly expanding. Magnesia bricks, magnesium carbon bricks, magnesium chrome bricks, high alumina bricks, wax stone bricks, lime bricks, etc., almost all refractory materials have achieved good results after impregnation, and the types of impregnants have also increased. In addition to tar pitch, various salts such as phosphoric acid and aluminum phosphate can also be used.
Phosphoric acid impregnated clay bricks
Phosphoric acid impregnated clay bricks are used in the waist and body of blast furnaces, and the use effect is good. Clay bricks just out of the kiln, if all indicators have been inspected and qualified, and the appearance has no missing corners or edges, and the size is within the specified range, can be put into phosphoric acid for impregnation; if it is a refractory brick that has been out of the kiln for a long time, it must be baked at 200℃ for 2 hours, and then the impregnation can be started in the hot brick state.
During the impregnation process, after the second low-temperature firing, phosphoric acid enters along the open pores of the brick, reacts with SiO₂ and Al₂O₃ in the brick, generates phosphate compounds, and fills the pores.
The porosity of clay bricks impregnated with phosphoric acid decreases, and the compressive strength is significantly improved. In addition, during the phosphoric acid impregnation process, the phosphate compounds generated have excellent alkali corrosion resistance, and also improve the special alkali corrosion resistance of clay bricks.
Phosphate (phosphoric acid) impregnated high-alumina bricks
Put ordinary high-alumina bricks in phosphate or phosphoric acid solution for impregnation, take them out from the phosphate solution or phosphoric acid solution after a certain period of time, and put them into use after drying. After being impregnated with phosphate or phosphoric acid, the load softening temperature of high-alumina bricks has increased, the porosity has been significantly reduced, the volume density has increased, the flexural strength has been improved, the use quality has been improved, and the service life has been significantly increased.
Salt-impregnated magnesia-chrome bricks
Magnesia-chrome bricks have excellent resistance to slag erosion, high temperature overheating damage, vacuum damage, oxidation reduction, and abrasion erosion. They are widely used in key parts of metal smelting furnaces, especially the working linings of smelting furnaces that use vacuum, acid-base changes in smelting slag, or strong oxidizing atmosphere, such as various high-quality steel refining furnaces (RH or DH vacuum degassing furnaces, VOD ladle vacuum degassing furnaces, AOD argon oxygen refining furnaces, ultra-high power electric furnaces, etc.), large non-ferrous metal smelting furnaces (flash furnaces, converters, anode furnaces, Kaldo furnaces, etc.) working linings, hot spots, slag lines, wind eye areas, erosion areas and other vulnerable parts.
The physical and chemical properties and performance of magnesia-chrome bricks treated with salt can be greatly improved. The reduction of porosity makes it difficult for the metal solution to enter the interior of the magnesia-chrome brick, blocking the open pores and extending the service life of the magnesia-chrome brick.
Impregnation is also one of the important process measures for producing refractory materials such as slide plates, casting bricks, and carbon-containing products. By impregnating the products, the carbon content, compressive strength and bulk density of the products can be greatly improved, the apparent porosity of the products can be reduced, and the thermal shock stability and corrosion resistance of the products can be improved.