The Appearance Inspection of Refractory Materials

The appearance inspection of refractory materials is generally on the basis of the brick design drawing. If there is no brick design drawing, and the bricks belong to standard brick, inspect the appearance according to the corresponding industry standards or national standards. In addition to dimension, edge losing, cracks and distortion, the inspection programs also include melted holes, fire marks and slag corrosion and end tilt. 

Fire Marks and Slag Corrosion

The fire marks of the refractory products are sediments on the surface caused by the ash pollution by produced by solid fuels. It is different from the slag corrosion. The slag corrosion is the colored melt caused by chemical reactions between the surface of bricks and other impurities and surface erosion. The fire marks do not affect the performance of refractory products, but the slag erosion does. The slag corrosion can be ignored after the products are processed and there is no significant pitted surface and erosion. 

 

Melted Hole

The melted hole is the melted void and the significantly colored part caused by low melting point substances on the brick surface. The hollow is the void caused by the external organic impurities (wood, oil sludge, cloth, etc.). The diameter of the hollow is allowed to exceed the double of the diameter of the melted hole. For example, if the diameter of the melted hole is defined as 8mm, the diameter of the hollow can be more than 16mm. 

 

End Tilt

The end face is not perpendicular to the center line of products. This situation is called end tilt. There are two ways to inspect the end tilt:

1) The end tilt is inspected with a 220x220mm square and a metal feeler with a width of 5mm and a thickness 0.1mm larger than the permissible limit of the standard. 

2) When inspecting, one side of the square firmly contacts the longitudinal surface of the product, while the other side firmly contacts the end face. Then insert the feeler into the gap formed by the square and the product. If the feeler cannot be inserted, the product is qualified. 

 

Insufficient Firing

Insufficient firing is always caused by improper operation when firing. There are two points to identify the insufficient firing:

1) Any product that has significantly different color from the normal products produced with the same process, insufficient dimension expansion and shrinkage and significantly unbroken particles on the section, is called insufficient fired product. 

2) The identification of the insufficient fired product is in accordance with the firing conditions and the physical and chemical properties of the product.