How to identify the quality of high alumina bricks

The quality identification of high alumina bricks can be carried out from the following aspects:

1. Appearance inspection

Color: The color of high alumina bricks is usually related to their alumina content. Generally speaking, the higher the alumina content, the whiter the color. The color of the third-grade high alumina brick is yellowish, the color of the second-grade high alumina brick is yellow-white, and the color of the first-grade high alumina brick is white. If the color is not smooth or there is no crystal phase, it may indicate that the sintering temperature is low and the strength is not good during use.

Surface quality: High quality high alumina bricks have a smooth surface and few black spots. Black spots are mainly formed by ferric oxide during the calcination process. If black spots appear in a large area, it means that the ferric oxide content of the brick is too high, and there may be problems in the ratio, which will affect the service life of the brick. At the same time, there should be no large area of molten material on the surface.

Flatness: The surface of the high alumina brick should be flat, without obvious bending, warping or unevenness. Bricks with uneven surfaces will increase the difficulty of construction during masonry, affecting the appearance quality and service life of the furnace lining.

Size: The size of high alumina bricks should be regular, with small side length errors, usually within the allowable tolerance range. If the size deviation is large, it may affect the quality of masonry, resulting in uneven brick joints and reducing the overall strength and sealing of the furnace lining.

2. Sound inspection

Use two bricks to hit, and the sound of high alumina bricks is crisp and not dull. This is because the internal structure of high-alumina bricks is tight and the sound conductivity is good when knocked.

3. Weight and volume density

Weight: The weight of high alumina bricks is related to their grade and alumina content. Generally speaking, the weight of a first-grade high alumina brick is about 4.4 kg, the weight of a second-grade high alumina brick is about 4.0 kg, the weight of a third-grade high alumina brick is about 3.7 kg, and the weight of a special-grade high alumina brick is about 4.8 kg. However, the weight will also be affected by factors such as the production process, so a fluctuation of 0.1-0.2 kg is within the normal error range.

Volume density: Volume density is one of the important indicators of the quality of high-alumina bricks. The volume density of high alumina bricks can be calculated by weighing and measuring the size. Generally speaking, the higher the volume density, the better the strength and refractory performance of the brick. If the volume density is lower than 2.3, it may be a grade 3 high alumina brick; if the volume density is greater than 2.3 but less than 2.45, it may be a grade 2 high alumina brick; if the volume density reaches 2.45 or above, it may be a grade 1 high alumina brick.

IV. Chemical test

Alumina content: The main component of high alumina brick is alumina. The higher the alumina content, the better the refractory performance of the brick. However, the alumina content needs to be known through chemical tests. Generally speaking, 55% aluminum content is a grade 3 high alumina brick, 65% is a grade 2 high alumina brick, and 75% is a grade 1 high alumina brick.

Other physical and chemical indicators: In addition to the alumina content, physical and chemical indicators such as strength, volume density, reburning line change, and load softening degree of high alumina bricks can also be tested. These indicators can more comprehensively reflect the quality and performance of high alumina bricks.

In summary, the quality of high alumina bricks needs to be comprehensively considered from multiple aspects such as appearance, sound, weight and volume density, and chemical tests. When purchasing and using high alumina bricks, you should choose the appropriate grade and quality of products according to your specific needs.