Steel billets during continuous casting can experience various common defects. These defects include surface cracks, central segregation, inclusion defects, internal cracks, surface and subsurface defects, and pipe defects.
Surface cracks are cracks that appear on the billet's outer surface. They can occur due to excessive cooling or improper mold lubrication. These cracks can weaken the structural integrity of the billet and potentially cause breakage during subsequent processing.
Central segregation is a defect that arises from an uneven distribution of elements within the billet. This uneven distribution leads to variations in composition across the billet's cross-section. As a result, the billet may possess inconsistent mechanical properties, making it unsuitable for certain applications.
Inclusion defects occur when non-metallic particles or impurities become trapped within the billet during casting. These particles can originate from the refractory lining, mold powder, or the steelmaking process itself. Inclusion defects weaken the material and diminish its overall quality.
Internal cracks are cracks that develop within the billet's body. Thermal stresses or improper cooling are often the culprits behind these cracks. Detecting internal cracks visually is challenging, and they can compromise the structural integrity of the billet.
Surface and subsurface defects encompass various issues such as surface depressions, oscillation marks, and hot tears. Surface depressions arise from excessive mold oscillation or poor mold conditions. Oscillation marks result from non-uniform mold oscillation, leading to uneven cooling and inconsistent billet dimensions. Hot tears occur when the billet contracts unevenly during solidification, resulting in cracks on the surface or subsurface.
Pipe defects are hollow cavities that form within the billet during solidification. Shrinkage is the main cause of these cavities, and they can weaken the material. If these pipes propagate to the surface, they can cause breakage during subsequent processing.
Overall, these defects pose significant challenges in producing high-quality steel billets. Continuous improvement in casting techniques, process control, and quality assurance measures are crucial in minimizing these defects and ensuring defect-free billet production.
Some common defects that can occur in steel billets during continuous casting include:
1. Surface cracks: These are cracks that appear on the outer surface of the billet. They can be caused by excessive cooling or improper mold lubrication. Surface cracks can lead to weakened structural integrity and may result in breakage during subsequent processing.
2. Central segregation: This defect occurs when there is an uneven distribution of elements within the billet, leading to variations in composition across its cross-section. Central segregation can result in inconsistent mechanical properties, making the billet unsuitable for certain applications.
3. Inclusion defects: Inclusions are non-metallic particles or impurities that become trapped within the billet during casting. They can originate from the refractory lining, mold powder, or the steelmaking process itself. Inclusion defects can weaken the material and reduce its overall quality.
4. Internal cracks: These cracks occur within the body of the billet and are often caused by thermal stresses or improper cooling. Internal cracks are difficult to detect visually and can compromise the billet's structural integrity.
5. Surface and subsurface defects: These defects include surface depressions, oscillation marks, and hot tears. Surface depressions can be caused by excessive mold oscillation or improper mold condition. Oscillation marks result from non-uniform mold oscillation, leading to uneven cooling and inconsistent billet dimensions. Hot tears occur when the billet contracts unevenly during solidification, resulting in cracks on the surface or subsurface.
6. Pipe defects: Pipes are hollow cavities that can form within the billet during solidification. They are caused by shrinkage and can result in weak points in the material. Pipes can be particularly problematic if they propagate to the surface, as they can lead to breakage during subsequent processing.
Overall, these defects can pose significant challenges in the production of high-quality steel billets. Continuous improvement in casting techniques, process control, and quality assurance measures are key to minimizing these defects and ensuring the production of defect-free billets.
Some common defects in steel billets during continuous casting include cracks, surface defects such as scabs or scale, internal defects like inclusions or porosity, and dimensional irregularities such as tapering or bulging.
