High alumina bricks are divided into special-grade high-alumina bricks, first-grade high-alumina bricks, second-grade high-alumina bricks, and third-grade high-alumina bricks. According to their characteristics and aluminum content, they can be divided into many types, and their uses are also different. Due to their characteristics and cost-effectiveness, the use of first, second and third-grade high-alumina bricks is very extensive. High-temperature kilns in industries such as steel smelting, chemical industry, glass, and power plants all have first, second and third-grade high-alumina bricks. It is because of the universal use of first, second and third-grade high-alumina bricks that it is usually difficult for users to distinguish the quality and grade of high-alumina bricks when purchasing, resulting in high prices and not being able to buy good products. Today, we will explain the quality and aluminum content of high-alumina refractory bricks from several aspects.
1. Section detection
After cutting off the refractory bricks, check the characteristics of the brick section. Uniform light or stack yellow cross-sections are normal characteristics of clay bricks, silica bricks and high-alumina bricks.
2. Appearance detection
The normal color of high-alumina bricks is generally white, light yellow, and dark yellow, but those with higher iron content are dark brown. The quality of refractory bricks cannot be accurately judged from their color alone.
There are eight regulations for crack inspection of high alumina bricks:
1) Use a steel ruler with a scale of 0.5mm and a steel wire with a diameter to measure the crack width (such as: 0.1.0.25.0.5.1.0mm) for crack inspection.
2) When inspecting cracks in high aluminum bricks, naturally insert the steel wire into the wide part of the crack, but do not insert it into the part where particles can be seen to fall off with the naked eye. The steel wire cannot be inserted into a crack of 0.25mm, and the width is less than 0.25mm. 0.25mm steel wire can be inserted into a crack that 0.5mm steel wire cannot be inserted into, and its width is expressed as 0.25-0.5mm, etc.
3) When the crack is not a straight line, it can be measured in segments, and the total length of each line segment is the total length of the crack. There are cracks with an intermittent distance of less than 5mm in the middle (including infinite cracks), that is, cracks, and their lengths are calculated together, except for cross and parallel cracks.
4) Cracks across edges, except for special circumstances, are calculated as continuous cracks. Cracks across both working and non-working surfaces are calculated as working surfaces. Cracks across two edges at the corners that do not exceed the specified value of the missing angle are not calculated as across two edges. The lower limit cracks specified in the standard are not restricted by the cross-edge and are not checked.
5) Surfaces with grooves and edges are calculated as one surface, except for cast high-alumina bricks. Surfaces with through holes are calculated as two surfaces.
6) High alumina bricks form long and thin straight cracks due to improper cooling, which are cold cracks and should be treated as unqualified products.
7) All cracks form a closed curve, that is, a mesh crack. When calculating the length of the mesh crack, the full length of the surrounding shall prevail. When more than one crack intersects, it is a cross crack. When calculating the number of cross cracks, the straight crack shall prevail.
8) Edges with a maximum angle of 120 degrees are not calculated as edges, and surfaces with a size less than 20mm are not calculated as surfaces, except for cast high-alumina bricks.
3. Standard brick weight detection
How to check whether the aluminum content of high aluminum refractory bricks is met? Single brick weight detection: According to the weight of a single brick, the weight of a single brick is 230*114*65mm (the aluminum content of the first-level high-aluminum brick is 75%, and the specific gravity is 2.5). The single brick type of the second-level high-aluminum brick (aluminum content 65%, specific gravity 2.3) is 3.9 kg, and the single brick type of the third-level high-aluminum brick (aluminum content 55%, specific gravity 2.15) is 3.7 kg. This method is suitable for T3 high-aluminum refractory bricks, not for special-shaped bricks;
High-aluminum refractory bricks are a chemical mixture, and the color of the mixture is difficult to control. If the grasp of each link during the firing process is slightly careless, it will cause uneven arrangement of particles on the surface of the brick, increase roughness, and slightly different colors.
Secondly, the surface of aluminum products will naturally react chemically over time to produce a thin film, which will also cause different colors of high-aluminum bricks. Even high-aluminum brick products produced by the same product, the same formula, and the same production date will have different colors due to different storage environments.
Nowadays, the production technology levels of various refractory brick manufacturers are uneven. The same formula, different production processes and methods will result in different colors of high alumina brick products.
