低碳铝镇静钢（LCAK）常用于生产冷轧板，要求铸坯有高的洁净度。但连铸开浇阶段由于浇铸状态的不稳定，会严重恶化头坯洁净度。从铸坯成分和非金属夹杂物等方面系统研究了一定浇铸条件下低碳铝镇静钢头坯洁净度的变化，并讨论了头坯洁净度的影响因素。结果表明，头坯洁净度在开浇准数达到0.17后趋于稳定，这可为实际生产中铸坯质量评级提供帮助。研究发现恶化头坯洁净度的主要因素是中间包二次氧化，并且除了由空气造成的中间包二次氧化外，更大程度上的二次氧化是由中间包耐火材料及覆盖渣等因素造成的。还提出了几点改善头坯洁净度的措施，为生产实践提供一定的参考。

High cleanliness is required for low carbon aluminum killed (LCAK for short) steel which is widely used for production of cold rolled sheet. But, head slab cleanliness is seriously deteriorated by the unsteady casting condition at casting start stage. Cleanliness of LCAK steel head slab was systemically investigated on aspects of slab composition and non-metallic inclusions under the present casting conditions. Besides, factors affecting the cleanliness of head slab were discussed. A cast starting number is defined.The results show that the head slab cleanliness is unstable until the number reaches 0.17, which can help slab quality classification. The main factor deteriorating head slab is the reoxidation in tundish. Besides oxygen in the air, more extent of reoxidation is caused by the refractory and covering slag in tundish. Several measures of improving head slab cleanliness were put forward as well, which can provide certain reference on plant operations.