超大断面圆坯垂直半连铸凝固过程模拟分析

Simulation Analysis of Solidification of Round Blooms with Super-Large Cross-Section during Vertical Semi-Continuous Casting Process

采用垂直半连铸工艺制备直径超过Ф1000 mm大型圆坯的方法,是一种优化生产流程,降低材料损耗,提升铸坯质量,突破连铸工艺尺寸极限的变革性制坯方法。该方法将工艺分为浇注拉坯和静置冷却两个阶段。通过模拟分析Ф1600 mm大圆坯在不同拉速下的垂直半连铸工艺过程发现在拉坯过程中结晶器内的温度和出口处的坯壳厚度逐步稳定。模拟结果表明,拉坯速度对完成拉坯时的熔池相貌有着显著的影响,当拉坯速度小于0.4 m/min时,纵向截面上的熔池形貌呈V形,在拉坯结束时,凝固坯壳在内部钢水静水压力作用下的应力和变形都较小,出现漏钢事故的可能性较低。在静置冷却阶段,小于0.4 m/min拉速下形成的初始V形熔池,可保证在后续凝固进程中凝固前沿出现明显的自下而上的顺序凝固过程。因此,Ф1600 mm大圆坯在垂直半连铸工艺条件下的拉坯速度应小于0.4 m/min。

The vertical semi-continuous casting technique for large round blooms in diameter equal to or beyondФ1000 mm is a revolutionary way to optimize the production process,reduce material loss,improve the quality of blooms and break the size limit of continuous casting process.The technique allows the solidification to happen in two stages:casting and standstill cooling.The analysis by simulating the solidification of aФ1600 mm large round bloom during vertical semi-continuous casting process at different casting speed reveals that the temperature of liquid steel in the mold and the shell thickness at the outlet become stable gradually during casting,and the casting speed of significant effect on the shape of the molten pool should be lower than 0.4 m/min.for vertical semi-continuous casting ofФ1600 mm large round blooms because the molten pool presents a V-shape in the longitudinal cross section when the casting speed is lower than 0.4 m/min.,which can reduce the risk of breakout accidents when the casting operation ends because the solidified shell suffers lower stress and deformation under hydrostatic pressure of the molten steel inside it,and can allow the solidification to occur obviously from the bottom to the top during standstill cooling.