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What are the Common Firing Defects in the Production of Refr

Sunrise Refractories Group has many years of experience in producing refractory bricks. For common firing defects in the production process of refractory bricks, Tianyang Refractories is summarized as follows:
The main defects are underburn, overburn, damage, pollution, black heart, distortion, cracks, etc.
 
Underburning is caused by insufficient firing temperature or insufficient holding time or leakage of cold wind. In general, under-fired bricks have low mechanical strength, loose bonding, low sound when struck, easy damage during transportation, and poor high temperature performance and corrosion resistance.
 
Over-firing is a problem caused by too high firing temperature, or too long holding time, or flame directly contacting the brick surface. In general, over-fired bricks have high mechanical strength, low apparent air voids, large size shrinkage, large brick deformation, too close bonding, serious research, loud sound when exposed, and poor thermal shock resistance. However, when transition metal oxide impurities such as Feigao Fe2O3 and TiO2 are present in the original department, over-firing may also cause the refractory to foam, reducing the density, increasing the apparent porosity, and increasing the volume expansion.
Defects are defects such as chipping, falling corners, and falling particles after burning. The reasons may be that the number of substrates is too small, the strength of the bonding agent is insufficient, the force is too strong during transportation, the kneading is uneven, the particles are segregated, the molding pressure is insufficient, or the firing temperature is too low.
 
Pollution refers to defects such as molten holes and iron spots. The cause of the melting hole may be caused by the low melting materials such as coal slag and sundries mixed with the brick material, and the refractory material is melted during firing. Iron plaques are dark plaques caused by the oxidation and diffusion of iron materials during firing when iron materials are mixed into the raw materials during manufacturing. The reason may be that iron materials are mixed with refractory raw materials during crushing and grinding.
Black heart is a defect that appears black in the center of the refractory after burning. The cause of the black heart may be that the surface of the product is sealed by the glass before the organic substances inside the product are oxidized. It may also be that the product is fired in a reducing atmosphere and is affected by the oxidizing atmosphere during cooling. Under normal circumstances, the corrosion resistance of black core products is not good.
 
Twisting is the deformation of refractory products under pressure at high temperatures, and its sign is that the edges of the bottom of the refractory brick are not on the same plane. Improper molding, kiln installation and firing may cause distortion of the refractory bricks.
 
Cracks refer to all kinds of cracks in refractory products after burning, including surface, internal, visible and hidden cracks. The causes of cracks are different, such as spalling due to improper molding; shrinkage and excessive expansion during drying and firing, or uneven shrinkage and expansion will cause cracks; bricks are heated and unevenly cooled during firing, resulting in inconsistent line construction Variations or excessive thermal stress can also cause cracking. In addition, when firing refractory materials containing free calcium oxide, special attention should be paid to as little as possible to attract various kinds of moisture (enclosed water, adsorbed water, crystal water, combined water), and strictly implement a heating system to prevent cracking of the brick.
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