Causes of cracks in high alumina bricks

November 12, 2018

Causes of cracks in high alumina bricks 

High alumina bricks molding is usually formed by a friction press or automatic brick press of 300T or more. Due to the cracks caused by the brick type, molding die, uneven cloth, forming operation and pressure, the biggest feature is strong regularity, and the depth, position and direction of the crack are basically the same.

1) Brick type

Because different brick types are pressed by different molds, the mold structure design with holes, tongues, grooves or corners is unreasonable, the tongue grooves are more and more difficult to form on the die upper surface, and both sides of the die are movable plates, which can easily lead to cracks after the mold is released.

2) Molding die

Unreasonable design:

Due to the lack of exhaust grooves and vent holes in the design of the molding die, cracks are easy to occur when the brick billet is molded out.

Unreasonable installation and use:

The mold is not installed properly, and the bricks are prone to cracks when they are molded. During the use of the mold, the mold and the mud are rubbed together during the molding process, and the surface finish and hardness of the mold wall are subject to certain wear, which may cause cracks in the holes, tongues, grooves or corners.

3) Uneven cloth

Uneven cloth easily makes the compactness of the edge and middle part of the high-aluminum brick blank different. When the blank is in the drying process, the surrounding temperature is lower than the middle, and the edge temperature is higher than the middle. The temperature causes the edge water to evaporate quickly, the intermediate water evaporates slowly, and the edge dehydration rate is greater than that of the middle portion. When the edge dehydration shrinks too fast, cracks occur at the edges of the green body.

4) Forming operation and pressure

During the forming operation, “short-range quick beating” and “full-range hard beating”, although most of the gas is excluded, a small part of the gas is compressed and not completely discharged. When the pressure exceeds the breaking strength of the brick , the brick will have internal transverse cracks.