As for how refractory materials are produced, we have previously introduced the firing process of refractory materials. So, does the firing process mean that all steps have been completed and the refractory products can be shipped?
The answer is of course no.
After the firing process is completed, we still have a crucial step, which is the finished product screening.
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The entire screening process can be divided into the following parts:
1. Check whether the shape and size of the product meet the requirements of the drawing
Generally, there is a certain allowable range for the positive and negative deviations of the finished product size in the standard, which is called the size allowable deviation.
In the standard, there are two ways to stipulate the allowable deviation of product size:
1. For example, the standard size of the product on the drawing is 200mm, and the allowable deviation of the finished product size is ±2mm. Then, products of 202-198mm are all qualified products;
2. If the original drawing length is 200mm, the allowable deviation of the finished product size is plus or minus 2%. Then, 200mm+200mm×2%＝204mm, 200mm－200mm×2%＝196mm are all qualified products.
2. Check the defect status of the product
1. Distortion
The bending deformation that may occur in refractory products during the firing process is called distortion.
The regulations on product distortion in the standard are different according to the product appearance quality requirements, grade, impact on masonry quality, and the length of the measured surface of the product.
For example, for ordinary high-aluminum bricks used in hot blast furnaces, the length of the brick is less than or equal to 345mm, and the distortion is not more than 1.5mm;
For products with a brick length greater than 345mm, the distortion is not more than 2.0mm.
2. Corner and edge missing
Different types of refractory products have clear regulations on the depth of corner and edge missing in the standard according to their use conditions, appearance quality requirements and grades. A few types (such as plug bricks) also limit the length of edge missing.
For example, for high-aluminum products used in hot blast furnaces, the length of corner missing (a+b+c) is allowed to be no more than 40mm, and the length of edge missing (e+f+g) is no more than 50mm.
3. Melt hole
Melt hole refers to the pit caused by the melting of low-melting substances on the brick surface.
In the standard, there is a strict control on the surface (working surface) of refractory products used in direct contact with the melt.
For example, the diameter of the melt hole of high-aluminum products for hot blast furnaces is stipulated as no more than 6mm on the working surface and no more than 8mm on the non-working surface; the diameter of the melt hole of high-aluminum bricks for ladle is stipulated as no more than 5mm and 7mm respectively.
4. Cracks
The cracks that can be seen from the surface of the product when a part of the organizational structure of the product is split are called cracks.
The crack regulations for various refractory products also vary according to their use conditions.
For ordinary refractory materials, cracks with a width of less than 0.2mm are generally not restricted;
However, cracks with a width of more than 1mm are not allowed.
Therefore, you can see that a qualified refractory brick has to go through so many strict screenings before it reaches the hands of customers to ensure that customers can get the best effect when using it.
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