HOW TO IDENTIFY THE QUALITY AND GRADE OF HIGH ALUMINA BRICKS

Recognizing the quality and grade of high alumina bricks can be identified from three aspects: appearance, body density, and laboratory tests.
First, identify from the appearance color: if the color is yellow, it is a third-level high alumina brick, if the color is yellow-white, it proves to be a second-level high alumina brick, if it is white, it is proved to be a first-class high alumina brick. If the appearance of these three colors is not smooth or there is no crystal phase, it means that the sintering temperature is low and the strength is not good during use.
In addition, it depends on whether there are black spots on the surface or a large area of ​​molten material. If there are black spots, it is because the iron content of the raw material is too high, and karst caves will appear during use, which will affect the service life. It also depends on whether the surface is flat. If the surface is not flat, it is because the legs are burned during sintering, and there are large bricks pressed on it, and the surface is uneven. This will also affect the staggered layer during masonry and will also affect the service life in the later period of use.
The next step is to look at the size. The size is measured with a ruler. If the length, width and thickness of the high alumina brick are greater than 2mm, it means that the size of the mold is large. It may also be the reason for the raw material. The ruler will increase after sintering. If the size is uniformly greater than 3mm above. High alumina bricks of this size cannot be used.
The quality can also be seen from the bulk density. The test method is to use an electronic scale to weigh a single brick, then measure the length, width, height or size of the head, and then calculate the volume. Divide the weight by the volume to get the height. If the specific gravity of the aluminum brick is lower than 2.3, it is proved to be a third-grade high alumina brick. If the bulk density is greater than 2.3, it is a second-grade high-alumina brick. If the bulk density is above 2.45, it is a first-grade high-alumina brick.
The aluminum content of refractory bricks, if the aluminum content is 55%, it is a third-grade high-alumina brick, if it is 65%, it is a second-grade high-alumina brick, if it is 75%, it is a first-grade high-alumina brick, but the aluminum content is It can only be known through chemical tests. Intuitively invisible.
In addition, the strength, thermal shock, and reburning line changes of the refractory bricks are all known through physical chemistry, which is invisible to the naked eye.
The load softening temperature of refractory bricks is also the most important item in the use process. There are two ways to identify this. One is to look at the sintering temperature. If the sintering temperature is 1380, then the load is about 1400. If the sintering temperature is 1450, then The load temperature is around 1480. However, if the load softening temperature is to be more accurate, it must be tested.
Under normal circumstances, the quality of high alumina bricks is judged from three intuitive methods: color, size shrinkage, and body density. Of course, if users request other indicators, they must be checked before they can be known.
According to the national standard, it is divided into one, two, and three levels, which is divided into 55%, 65%, and 75% aluminum content.
Currently on the market, because of the difference in furnace type and temperature, there are more kinds of products according to different furnace temperatures, 55%, 65%, 68%, 70%, 72%, 75%, The diversification of 80% aluminum content is due to the fact that the price is also divided into multiple levels.
In this way, more and more products are suitable for temperature and are affordable. This is also due to the actual situation. The epidemic in 2020 and the floods in 2021 have caused many manufacturers to suffer heavy losses, and the price ranges of the three types of bricks of the first, second and third grades are very different. Some furnaces are selected for moderate temperature. The temperature material is used as the inner lining, so that even if it is used, the cost will be reduced. This is also the situation where high-alumina bricks are used in multiple grades due to the actual situation.
More than ten years ago, 48% aluminum content can be called a third-grade high-alumina brick. In the current production, the aluminum content of clay bricks is about 58%. Therefore, 48% aluminum content can only be clay bricks. Basically, if the aluminum content is less than 65% and the aluminum content is within the range of 60%, it is a natural third-grade high-alumina brick that is conventionally agreed. The aluminum content has increased a lot.
However, no matter how high the aluminum content is, the bulk density and load softening temperature are the key to controlling the quality of the product. If the density is not reached, it proves that the quality of the product is not good, and the load softening temperature is the limit that can best prove the quality of the brick, because the load The softening temperature is the most difficult standard to achieve. The reason is that the raw materials are resource-based. People can’t control them if they are taken from underground or mines.
When purchasing raw materials, the price is determined according to the aluminum content and density of the raw materials. When the softening temperature under load cannot be reached, a certain proportion of external raw materials must be added to achieve it. Therefore, the higher the softening temperature under load, the better the performance. This is also the reason for the diversification of its aluminum content.