IMPROVEMENT OF SURFACE QUALITY OF CONTINUOUSLY CASTED SLAB OF MEDIUM CARBON STEEL

摘要

Krakatau Steel has commercially produced many steel grades for critical application such as automotives, households, tin mill black plates, oil- gas line pipes, LPG bottles and pressure vessels. These products are mainly classified into four types of steel grade which are consisted of low carbon, medium carbon, high carbon and micro alloy grades. In term of medium carbon steel especially for application of tin mill black plate products and oilgas line pipe. Krakatau Steel has successfully improved the strength properties of steels, formability, toughness and utility properties. However, such a steel grade has low cast ability because of low hot utility and high shrinkage. The slab products has low surface quality due to surface cracks such as corner crack, transverse crack and star crack. In order to eliminate the surface quality problems, optimization of casting parameters of medium carbon steel which consist of casting speed, casting temperature, secondary cooling and machine alignment has been carried out. In this paper, the authors describe some countermeasures performed to improve slab surface quality of medium carbon steel grade by optimizing casting process (and maintaining performance of continuous casting machine).