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 yellowish-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 aluminum 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 refractory brick; if the volume density is greater than 2.3 but less than 2.45, it may be a grade 2 high alumina firebrick; if the volume density reaches 2.45 or above, it may be a grade 1 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 can only be known through chemical testing. Generally speaking, 55% aluminum content is a grade 3 high alumina fire brick, 65% is a grade 2 high alumina refractory brick, and 75% is a grade 1 high alumina firebrick.
Other physical and chemical indicators: In addition to alumina content, physical and chemical indicators such as strength, volume density, reburning line change, and load softening degree of high alumina fire bricks can also be tested. These indicators can more comprehensively reflect the quality and performance of high alumina firebricks.
In summary, the quality of high alumina firebricks needs to be comprehensively considered from multiple aspects such as appearance, sound, weight and volume density, and chemical testing. When purchasing and using high aluminum bricks, you should choose the appropriate grade and quality of products according to your specific needs.
