模具温控凝固成形中关键控制参数的选取

提出了一种基于数值模拟的模具温控凝固成形控制参数的选取方法.针对两个较易于控制的关键控制参数进行了研究,对模具预热温度取743、693、673K和冷却控制阈值取753、293、673K等多种工艺条件的成形过程进行了三维非稳态传热模拟,模拟值与实验值的误差在8%以内.结果表明:模具预热温度稍高于材料熔点时有利于减少缩孔缺陷,提高成形质量,同时应结合成形效率和工艺误差合理选取模具预热温度;冷却控制阈值取753K时,全部冷却管道同时开启,材料中上部形成了明显的缩孔;阈值取673K时成形质量较好,此时7组冷却管道依次开启,固液界面基本保持平面形状,凝固速度较快.

Selection of Key Control Parameters of Mold-Temperature-Control Solidification

A method for selecting the control parameters of the mold-temperature-control solidification(MTCS) is presented based on numerical simulations,and two significant parameters which are easy to control,are adopted to carry out the investigation.Then,a 3D transient heat transfer analysis is performed in various conditions with the mold-preheated temperatures of 743,693 and 673 K and the cooling thresholds of 753,293 and 673 K,and a deviance between the numerical and experimental data of less than 8% is obtained.The results indicate that(1) a mold-preheated temperature higher than the melting point of the workpiece contributes to the reduction of shrinkage cavities and the improvement of forming quality;(2) the mold-preheated temperature should be determined by considering both the molding efficiency and the process error;and(3) at a cooling threshold of 753 K,all the cooling channels simultaneously open and obvious shrinkage cavities form in the upper center of the workpiece,while at a cooling threshold of 673 K,seven groups of cooling channels open in sequence and excellent forming quality is achieved since the solid-liquid interface maintains a near-planar surface and the solidification velocity remains fast.