If you want to reduce the production cost of magnesia-carbon bricks and learn how to scientifically introduce recycled materials, you must first know how to identify the quality of waste magnesia-carbon bricks. First we need to classify:
(1) Large crystalline waste magnesia carbon bricks are produced from large crystalline fused magnesia and high-grade graphite. The large particles are mainly large crystalline fused magnesia.
(2) Fused waste magnesia carbon bricks are produced from fused magnesia and graphite, and the large particles are mainly fused magnesia.
(3) High-purity waste magnesia-carbon bricks are produced from high-purity magnesia and graphite. The large particles are mainly high-purity magnesia.
(4) Recycled waste magnesia carbon bricks are produced from recycled materials and a small amount of magnesia and graphite. They have few large particles and are basically fake particles.
(5) Bauxite waste alumina-magnesia carbon bricks are produced from alumina and a small amount of magnesia and graphite. The large particles are mainly 88 alumina.
(6) Corundum waste alumina-magnesia carbon bricks are produced from corundum and a small amount of magnesia and graphite. The large particles are mainly corundum.
The identification of waste magnesia carbon bricks requires the accumulation of time and experience to achieve high accuracy. Look for experience in the actual operation process, observe more, and have more contact. After summary, it can be divided into three steps: the first step is to observe the appearance, which is referred to as the first observation; the second step is to crush and see the structure of the pellets, which is referred to as the second smashing; and the third step is to test, which is referred to as the third test.
The first step to observe the appearance is to observe the overall appearance. The overall appearance can make people judge the approximate grade.
If the overall appearance is that the particles are large and plump, the color is black and shiny, and the corners are round and crispy, then this type of waste magnesia carbon bricks generally belong to a relatively high-grade category. The large particles, black and shiny color, indicate that the magnesia grade is high, the amount of graphite added is large, and the edges are round and crisp, which further proves this point. Products with high graphite content have low strength after use and frequently collide with natural edges during transportation. The corners are round and crunchy.
On the other hand, if the overall appearance is that the large particles are not obvious, the color is dark and dull, and the corners are neat and orderly, then this type is generally of a lower grade.
In addition to the lower-grade ones, which are dark and dull in color and have neat and orderly corners, the same is true for waste alumina-magnesia carbon bricks. However, the waste alumina-magnesia carbon bricks are exposed to the outside and watered by wind and rain. After a long time, there are many rust spots on the surface. This is because refractory materials with high aluminum content are prone to nodules and slag during use. The slag contains iron, which will cause rust over time.
The second step of crushing to see the structure of the pellets is to use a hammer to break them open and then observe the taste of the particles. The color of magnesia of used magnesia carbon bricks is different from that of unused magnesia. We distinguish what kind of magnesia it is based on the color of magnesia and the size of grains.
As shown in Figure 4, after breaking open, the particles are white in color and full of grains. This is a typical large crystalline magnesia particle
As shown in Figure 5, after breaking open, the crystallization is obvious, but the grains are not large, and the color is yellow, light yellow, off-white or white with black, which is a typical fused magnesia particle. The color is yellow. It is easy to tell that this is fused magnesia. This kind of particles generally exists in magnesia carbon bricks that have not been exposed to high temperatures. As shown in the picture on the right, the color is white with black. This is not large crystalline fused magnesia. sand, but ordinary fused magnesia. The reason why it is white is that the colored impurity oxides in magnesia are reduced by graphite. Although the color is white, the grains are too small and are still different from large crystalline magnesia. There is a big difference. This kind of particles mainly exists in magnesia carbon bricks that have been exposed to high temperatures for a long time.
As shown in Figure 6, after being broken open, the cross section is fine, with no obvious crystallization, and the color is grayish white or light yellow. This kind of particle is high-purity magnesia.
As shown in Figure 7, the particles feel hard and brittle when struck. After breaking open, the cross section is fine, without crystals, gray or dark gray in color, and sharp in cross section. These particles are alumina particles.
If after breaking it open, it is difficult to find large particles, or if you find large particles and lightly smash them, the particles will turn into powder or disperse into small particles without new cross-sections, indicating that these particles are fake particles and residual particles. The bricks are recycled waste magnesia carbon bricks.
The third step is testing, which refers to sampling and testing the waste magnesia carbon bricks you are interested in purchasing to verify the results of the previous judgment based on experience.