Common Types of Surface Cracks on Silica Bricks

      The cracks of silica brick products can be divided into surface cracks and internal cracks, which are also called lamellar cracks. Surface cracks are divided into transverse cracks, longitudinal cracks and network cracks. Silica bricks are made of dense body by semi-dry machine press molding method. The cracks produced along the pressing direction of bricks are transverse cracks, and the cracks produced perpendicular to the pressing direction of bricks are vertical cracks. The surface of silica brick products is composed of Composed of several cracks, cracks distributed in a spider web, that is, network cracks.

      Usually, as far as a standard type silica brick is concerned, the pressing direction of the green body is generally the thickness direction. The molding process of silica brick products is essentially a process of making the particles in the billet dense and the air discharged to form a dense body. After the adobe is machine-pressed, it has the advantages of high density, high strength, small drying shrinkage and firing shrinkage, and easy control of product size. However, when the machine press molding process is not properly controlled, the green body will form layered cracks perpendicular to the direction of pressing during the pressurization process. Therefore, the layered cracks inside the silica brick, or lamellar cracks for short, are also longitudinal cracks.

      Large spalls can be detected just after the brick is formed, or after the brick is dried. However, the micro-cracks in the adobe can only be clearly detected after firing if they continue to expand with the action of thermal stress during the firing process of the silica brick. Silica bricks containing crack defects, especially lamellar cracks, are prone to fracture, which can not be used, but also reduces the yield of silica brick products.

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