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为了阐明铸锭健全性与凝固要素的关系,本文建立了单方向凝固过程凝固收缩负压的数学模型,并解决了模型中各项要素、特别是液体在固-液两相区内穿透率的合理确定方法。以Al-3mass％Si为实验合金,通过测定整体凝固和单方向凝固两种类型实验所得铸锭的密度,并与收缩负压计算结果相比较,得到如下结果:(1)根据补液性随固相率的变化,可将凝固过程分为EFZ、RFZ、IFZ三个凝固区间,其中RFZ的补液性对铸锭健全性影响最为重要;(2)RFZ和IFZ的分界固相率为液体在两相区内的流动限度固相率,其值在冷却速度为0.12K/s时约为0.7;(3)建立了单方向凝固收缩负压数学模型,解决了模型中诸因素的合理确定方法;(4)铸锭密度同凝固速度V和液体能够流动的固-液两相区长度L的乘积有良好的相关性;(5)收缩负压随V·L成比例增加,并在达到一定值后,助长气孔缺陷的生成。
In order to clarify the relationship between ingot robustness and solidification factors, a mathematical model of solidification shrinkage under unidirectional solidification was set up and various factors in the model were solved, especially the penetration rate of liquid in solid-liquid two-phase region Reasonable way to determine. Taking Al-3mass% Si as the experimental alloy, the density of the ingot obtained by the two kinds of experiments of solidification and unidirectional solidification was measured and compared with the calculation results of the shrinkage under negative pressure. The following results were obtained: (1) The solidification process can be divided into three solidification zones: EFZ, RFZ and IFZ. Among them, the rehydration of RFZ is the most important factor affecting the robustness of ingot. (2) The solidus ratio of RFZ and IFZ is Phase flow rate solid phase rate, the value of the cooling rate of 0.12K / s is about 0.7; (3) established a unidirectional solidification shrinkage negative pressure mathematical model to solve the model of a reasonable determination of the factors; (4) There is a good correlation between the density of the ingot and the product of the solidification velocity V and the length L of the solid-liquid two-phase zone where the liquid can flow. (5) The negative pressure of contraction increases proportionally with V · L and reaches a certain value After, contribute to the formation of stomatal defects.