Continuous casting bloom (CCB) surface defect can be defined as a surface defect that is present when the surface of the CCB does not meet the desired quality standard. The surface defect can be caused by a number of factors including improper casting parameters, inadequate mold release, inadequate mold lubrication, and poor heat-sink effect.
Some of the common surface defects seen with the CCB include pores, cracks, and pits. Pores, or indentations on the surface of the CCB, are usually small and can be caused by gas trapped in the metal during solidification. There are several methods used to reduce and prevent pores, namely, proper mold preparation, proper mold lubrication, and correct filling.
Cracks are surface defects which are usually linear and deep. They are caused by high forces that can result from either mechanical or thermal stresses. If mechanical stresses are the cause of the cracking, they can most likely be corrected with appropriate heat treatment. Heat treatment, when conducted correctly and at a suitable temperature, can reduce the amount of cracking that is visible on the surface of the CCB.
Tiny pits on the surface of the CCB can also be visible and present. These defacement may form due to base metal contamination, improper mold design, incorrect filling technique and inadequate cooling as the casting solidifies. There are several methods implemented to reduce this type of surface defect. These include proper cleaning and maintenance of the casting machinery and equipment, accurate mold design and filling, and correct mold cooling.
In conclusion, surface defects on the CCB can significantly detract from the quality of the metal product, making it unsuitable for a wide range of applications. It is important to ensure the casting machine and operations are routinely inspected and maintained in order to ensure quality metal products with minimal defects. Appropriate heat treatment, mold design and maintenance, and cooling will all help reduce the occurrence of these surface defects.
