东北大学毕业设计（论文） 摘 要
Q345宽厚板坯凝固微观组织特征参数研究
摘 要
本文采用ANSYS有限元分析软件，建立宽厚板坯连铸凝固传热数学模型对国内某钢厂1830mm×230mm宽厚板坯Q345钢连铸过程进行了研究。模型预测了铸坯凝固微观组织特征参数一次枝晶臂间距λ1和二次枝晶臂间距λ2，并通过与现场铸坯取样实验结果对比，验证、优化模型，提出了适合Q345钢宽厚板坯连铸凝固组织经验预测模型，在此基础上研究了Q345钢宽厚板坯凝固微观组织特征参数λ1和λ2的分布规律。并讨论了连铸工艺参数（拉速、过热度和比水量）对Q345钢宽厚板坯凝固微观组织特征参数一次枝晶间臂距λ1和二次枝晶间距臂λ2的影响。得到以下主要结论：
(1) 提出了适合Q345宽厚板坯连铸凝固微观组织特征参数的经验预测模型，即
?0.466291602?0.10931377?0.723687242λ1?278.748?CR?CC和λ1?148?CR。
(2) 在其他连铸条件不变的情况下，随着拉速的增大，Q345钢的一次枝晶臂间距λ1和二次枝晶臂间距λ2也会相应地增大，因此，想要获得致密而均匀的组织，需要尽量减小拉速。
(3) 在其他连铸条件不变的情况下，随着过热度的变化，Q345钢的一次枝晶臂间距λ1和二次枝晶臂间距λ2并没有太大的变化，也就是说，Q345钢的凝固微观组织受过热度的影响较小。
(4) 在其他连铸条件不变的情况下，随着比水量的增大，Q345钢的一次枝晶臂间距λ1和二次枝晶臂间距λ2会相应地减小，因此，想要获得致密而均匀的组织，需要尽量增大比水量。
关键词：Q345钢，宽厚板坯，连铸，数值模拟，一次枝晶臂间距λ1，二次枝晶臂间距
λ2，枝晶显示试验
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东北大学毕业设计（论文） Abstract
Abstract
By using the finite element analysis software——ANSYS, a heat transferring mathematical model about wide-thick slab continuous casting solidification was established to study the 1830 x 230 mm wide-thick slab of Q345 steel continuous casting process in a domestic steel mills. The model predicted the primary dendrite arm spacing λ1 and the secondary dendrite arm spacing λ2, which are the characteristic parameters of solidification microstructure of the slab. Through comparing the experimental results with the slab samples, the model was verified and optimized, following that the suitable empirical prediction model for wide-thick slab of Q345 continuous casting solidification organization was obtained, and λ1 and λ2, the solidification microstructure characteristic parameters of wide-thick slab of Q345,was studied based on the former work. Furthermore, we also discussed the influence of continuous casting process parameters (withdrawal speed, degree of superheat and the specific water flow) to λ1 and λ2. And the following main conclusions could be obtained:
(1) Putting forward the suitable empirical prediction model for solidification microstructure characteristic parameters of the wide-thick continuous casting slab of Q345:
0.466291602?0.723687242?1?278.748?C??CC?0.109317377and?2?148CRR
(2) Under the condition of invariable in other casting conditions, with the increase of withdrawal speed,λ1 and λ2 of Q345 steel will also increase accordingly. Therefore, to obtain dense and uniform structures, the speed needs to be limited.
(3) Under the condition of invariable in other casting conditions, with the change of the degree of superheat, λ1 and λ2 of Q345 steel will not change a lot, that is to say, the Q345 steel solidification microstructure has little effect on the heat.
(4) Under the condition of invariable in other casting conditions, with the increase of the specific water flow，λ1 and λ2 of Q345 steel will be reduced accordingly，so we need to increase the specific water flow as much as possible to obtain dense and uniform structures.
Keywords: Q345 steel, wide-thick slab， continuous casting, numerical simulation, primary arm spacing λ1 ,secondary arm spacing λ2，the characterization test of dendrite
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