高拉速连铸低碳铝镇静钢铸坯中夹杂物

针对高拉速板坯连铸生产的低碳铝镇静钢铸坯，采用Aspex自动扫描电镜对铸坯表层夹杂物进行大面积的扫描分析，得到不同拉速下夹杂物的变化规律，并探究流场和S含量对夹杂物分布的影响。结果表明：随着拉速增大，钩状坯壳的深度和长度逐渐减小。对拉速大于2 m·min-1的铸坯，由于钩状坯壳不是很发达，铸坯表层没有发现大于200μm的夹杂物。铸坯表层尺寸介于50~200μm的夹杂物主要是由凝固坯壳所捕获，而夹杂物在凝固前沿的受力决定了夹杂物的捕获行为。随着拉速提高，凝固前沿的钢液流速增加，随着冲刷力的增加、捕获力的减少，夹杂物被捕获的数量减少。在高拉速连铸下，如果钢液中S含量较大，夹杂物受到明显的温度Marangoni力，会更容易被凝固坯壳捕获。

Inclusions in low carbon aluminum killed steel slabs at high casting speed

Inclusions in the surface of low carbon aluminum killed steel slabs cast at high casting speed were analyzed by Aspex automated scanning electron microscopy in a large area. The changes in number and size of inclusions were tested at different casting speeds, and the influence of flow fields and sulfur content on the distribution of inclusions was explained in detail. It is found that when the casting speed increases, the depth and length of hooks decrease. Hooks in the slab subsurface is not obvious when the cast-ing speed larger than 2 m·min-1 , so inclusions larger than 200μm cannot be found in the slab surface. Inclusions with the size of 50-200μm in the slab surface are mainly entrapped by the solidified shell, and the entrapment of inclusions is influenced by forces acting on inclusions at the solidifying front. The flow velocity of molten steel increases due to increasing casting speed, then the washing force becomes large and the entrapping force becomes small, and therefore the number of entrapped inclusions decreases. If the sulfur con-tent in the steel is high at high casting speed, inclusions will be easily entrapped by the solidified shell due to the thermal Marangoni force acting on inclusions obviously.