Characteristics of Inclusions and Microstructures Around Solidification Hook of Low-Carbon Steel Continuous Casting Slab

The area around the solidification hook for low-carbon steel continuous casting slab is divided into four zones: zone A (the overflow zone), zone B (the capture zone), zone C (the zone between oscillation marks) and zone D (the oscillation mark zone without hook). The inclusions and microstructures in the zones of A, B, C and D are observed and detected. The results indicate that the inclusions captured by the solidification hook are Al2O3, MnO and MnO + MnS. The number densities of Al2O3, MnO and MnO + MnS in the zone B are all higher than those of the same types of inclusions in the other zones, indicating that the solidification hook have no tendency to just catch a certain type of inclusions. The proportion of the inclusions greater than 5 & mu;m in the zone B is close to 40 pct, and those in the other zones are less than 12 pct, indicating that the solidification hook is easy to capture the inclusions greater than 5 & mu;m. Besides, the grains near the oscillation marks on the zones of A, B and D are mostly with orientation, while the grains in the zone C are mainly with orientation and the proportion of the grain boundaries with low angle in the zone C is the largest. Thus, the grain orientations and grain boundary angles are affected by the oscillation marks. There are lots of small grains in the zone B because inclusions can hinder the movement of grain boundaries during grain growth. The temperature marangoni force and buoyancy force are the decisive forces whether the solidification hook can capture the large inclusions or not.