双流板坯中间包加高提升钢液洁净度的数理模拟

Numerical and physical simulation on enhancing steel cleanliness by increasing height of two-strand slab tundish

连铸过程逐渐向大断面高拉速方向发展,中间包容量成为制约生产效率和铸坯质量的关键因素。以某厂双流板坯中间包为对象,通过数理模拟分析不同加高高度下的流场、停留时间分布(Residence Time Distribution, RTD)曲线及夹杂物去除率。结果表明,随着中间包包壁加高和容量相应增大,钢液平均停留时间延长,中间包净化钢液的能力也相应提高。当挡墙随中间包抬高200 mm时,相比于原型和其他加高扩容方案,中间包内钢液平均停留时间延长12.1~153.6 s,死区体积分数减小0.31~2.53个百分点,冲击区自由液面平均速度减小6.7%~15.6%,中间包内钢液额外温降不明显,夹杂物总去除率提高1.63个百分点。此外,中间包加高200 mm时,拉速由1.35 m/min提高到1.50 m/min,使钢液平均停留时间由743.7 s降至677.9 s,仍比原型低拉速时高88.0 s,且死区体积分数降低了2.18个百分点,体现了扩容中间包在高拉速连铸中的优势。本研究可为钢铁企业进行中间包加高扩容及高拉速浇注工业计划的实施提供理论指导。

With the development of continuous casting process towards the direction of large cross section and high casting speed,the capacity of tundish has become key factor restricting production efficiency and billet quality.The flow field,residence time distribution(RTD)curves and inclusion removal rate in two-strand slab tundish of a steelmaking plant with different height additions were numerically and physically investigated.The results show that with the increase of tundish height,the capacity of tundish increases and the average residence time of molten steel increases correspondingly,and the ability of tundish to enhance the cleanliness of molten steel is also improved.When the baffle is raised by 2oo mm with the tundish,the average residence time of molten steel in the tundish is extended by 12.1-153.6 s,the volume fraction of dead zone is reduced by 0.31-2.53 percentage points,the average free surface velocity in the impact zone is reduced by 6.7%-15.6%,and the extra temperature drop in the tundish is not obvious.The total removal rate of large size inclusions is increased by 1.63 percentage points,compared with the original tundish and other height expansion schemes.Moreover,when the tundish is heightened by 200 mm,the average residence time of molten steel is reduced from 743.7 s to 677.9 s by increasing the casting speed from 1.35 m/min to 1.50 m/min,but it is still 88.0 s longer than that of the prototype tundish at low casting speed,and volume fraction of dead zone is reduced by 2.18 percentage points,which reflects the advantages of the heightened tundish in continuous casting process with high casting speed.The present study can provide theoretical guidance for steelmaking plants to implement the industrial plan of heightening the tundish height and increasing the casting speed.