| After several decades' development, the conventional slab continuous casting technology has been sophisticated gradually. High casting speed and high efficiency become the goal. Due to the easier control in low casting speed, the slab quality can meet the requirement. However, high casting speed and unsteady casting easily lead to product quality problems. Therefore, it's significant to research the slab quality on high casting speed and unsteady conditions.As the heart of a caster, continuous casting mold plays a crucial role in slab surface quality control. No.2 caster of Meishan Steel was regarded as the research object in the paper. And the industrial investigation was executed to handle the slab quality on unsteady and high casting speed conditions. It also obtained the basic caster parameter and control criterion of the related casting processing. After an amount of slab samples were detected off line by sulfur print and macroscopic examination, small samples were taken from the slab surface, and the quantity of inclusions per unit area ware counted. In order to evaluate the quality of slab, the total oxygen(T[O]) content was measured. Furthermore, this paper constructed the mathematic model,which would be used to simulate the liquid steel flow in mold of Meishan Steel No.2 caster. Based on the model, this paper simulated the flow behavior of liquid steel, including in different section, casting speed, SEN depth, distribution of bubbles and molten slag layer, and the bias flow etc. It would provide a theoretical and practical foundation for the slab quality control.The slab quality study shows that, as a whole, the slab quality at Meishan Steel is placed at a mid-level. The main defects are inclusions and pinholes. The most of inclusions are indigenous Al2O3 and aluminate, and the pinholes caused by argon injection mostly distribute in narrow face. Several unsteady conditions, such as casting start, end and casting speed variation, affect the slab quality greatly, and the influence of laddle exchange ,SEN change, SEN clogging is relative low. The content of inclusion on unsteady conditions is 2-6 times of that on steady conditions. And the T[O] on unsteady conditions is 1.33 times of that on steady ones. Otherwise, the quality of beginning and tail slab is worse than normal ones. The former inclusion content is 26% higher than the latter. Based on the evaluation, the last second slab needn't to be degrade.Numerical simulation shows, when casting speed is 1.8m/min, normal section, near narrow face, there is not flux layer in a large area. And in section 1300mm×210mm, the flow rate in surface level reaches 0.34m/s. So, it should control the surface flow rate by EMBr or decrease casting speed. when casting speed is 1.2m/min, molten slag layer is thin in narrow face, and need to be improved by EMBr. Bias flow is easy to generate asymmetry flow and vortices. What's worse, it will induce slag entrapment. The fine bubbles, desquamation clogging and inclusions easily follow the stream and reach the narrow face and bottom of mold. It's easy to induce defects.
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