基于实验与3D-CAFé法的高硅钢铸锭凝固行为

通过空冷和水冷实验研究了高硅钢的铸态组织，发现高硅钢铸态组织主要由粗大的柱状晶构成，水冷铸锭中柱状晶比例高达90%以上.依据铸锭的化学成分和晶粒统计结果，确定了3D-CAFE法模拟所需的枝晶生长动力学系数及高斯分布等参数.采用CAFE法对不同冷却条件下高硅钢的凝固过程进行模拟研究，发现空冷铸锭较水冷铸锭的温度场更均匀，糊状区更宽阔；空冷铸锭呈“过渡式”凝固，水冷铸锭呈“分层式”凝固；空冷流场较水冷流场更稳定，凝固末期冒口处出现明显的抽吸现象，而水冷模拟结果中未观察到该现象.组织模拟结果发现，模拟得到的高硅钢凝固组织无论是形貌还是晶粒尺寸都与实验结果相一致；最后通过改变浇注温度模拟研究了过热度对高硅钢凝固组织的影响，结果表明，随着过热度的降低，铸锭中心等轴晶率提高，晶粒数量增加，晶粒尺寸变得细小. 

Solidification behavior of high-silicon steel based on experimental and 3D-CAFE method

The as-cast structure of high-silicon steel ingots under different cooling conditions was studied in this paper. It is found that the as-cast structure of the ingot is formed mainly by coarse columnar crystals, especially in the water cooling ingot, and the ratio is reaches as 90%. The dendrite tip growth kinetic coefficients and Gauss distribution parameters for 3D-CAFE simulation were determined according to the compositions of high-silicon steel and the results of as-cast structure. Then the solidification process of high-silicon steel under different cooling conditions was simulated by 3D-CAFE method. The results show that the temperature field under air cooling is more uniform, the mushy zone is broader, and it exhibits a transitional solidification pattern, however, which shows a layered solidification pattern under water cooling. The flow field under air cooling is more stable than that under water cooling, there is a remarkable suction region within the feeder head of the air cooling ingot, and this phenomenon is not observed in the water cooling one. The CAFE results including both morphology and grain size show a good agreement with the results from experiments. Moreover, the influence of superheat on the solidification structures was researched to find that the ratio and quantity of equiaxed structures increase with the decrease of the superheat, and the grain size becomes finer.