薄板坯连铸及其铸坯表面缺陷的形成机理

薄板坯连铸连轧技术已成为了钢铁冶金技术发展的主要趋势之一,但薄板坯连铸具有拉速高、凝固速度快、铸坯宽厚比大等特点,使得铸坯容易出现表面夹渣、表面裂纹等缺陷,而这些铸坯表面缺陷问题的产生与结晶器流场、温度和热流分布有直接的联系。因此,对薄板坯连铸结晶器内高温动态行为进行系统地概述,并在此基础上分析了铸坯表面缺陷的形成机理。研究表明,薄板坯连铸结晶器内钢液流动更加紊乱、涡流速度更快,这不利于夹杂物的上浮,且容易导致卷渣的发生,增大铸坯表面夹渣缺陷产生的可能。此外,在钢液湍流和涡流的作用下,铸坯内温度分布不均,加上在高拉速下结晶器内热流更大,这使得铸坯表面更易产生裂纹缺陷。

A review of thin slab casting and formation of slab surface defects

Thin slab casting and rolling technology has become one of the main trends in the development of metallurgy technology. However, there is prone to occur surface defects of the as-cast slab during the process of thin slab continuous casting, such as surface inclusive slag and surface cracks, which is due to the high casting speed, and the fast solidification speed of slab, and its large ratio of width to thickness. Furthermore, the formation of the slab surface defects is directly related to the flow flied and the distribution of temperature, as well as the heat flux in mold. Therefore, the in-mold high temperature dynamic behavior during the process of thin slab continuous casting has been systemically summarized. Besides, the formation of slab defects has also been analyzed. The results indicated that there was the serious random turbulence and the faster vortex velocity of in-mold molten steel, which prevented the inclusion from floating up, and leaded to the occurrence of inclusive slag and cracks in slab surface. In addition, the temperature distribution in slab was easy to unevenness under the turbulence effect, and plus the high heat flux with the high casting speed, which resulted in the formation of slab cracks.