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抽真空是消除铸件气孔缺陷的有效方法。在综述现有各种压铸真空系统抽真空动力学特点的基础上,指出现行压铸真空技术难以获得满意抽真空效果的原因是:为及时有效关断真空通道、阻止高速充型熔体进入真空系统而导致型腔抽真空速度过低。然后根据型腔气体排溢动力学理论,提出在确保真空通道及时关断的前提下,抽真空效果主要取决于抽真空系统的动态响应特征和型腔在高速熔体充填前所能达到的真空度;增大抽排气管路当量直径和减小管道长度是抽真空排气通道的设计关键,并展示了满足该原则的新型抽真空技术的使用效果。
Vacuum is to eliminate porosity defects in casting an effective method. On the basis of reviewing the vacuum dynamics characteristics of various die-casting vacuum systems, it is pointed out that the reason why vacuum die-casting technology is difficult to obtain satisfactory vacuum-evacuation effect is as follows: to effectively shut off the vacuum passage in time and prevent the high-speed filling melt from entering the vacuum system Which led to cavity vacuum speed too low. Then according to the theory of cavity gas discharge dynamics, it is proposed that the vacuum effect depends on the dynamic response characteristics of the vacuum system and the vacuum that the cavity can reach before the high-speed melt filling, under the premise of ensuring the vacuum channel is shut off in time. Degree; increasing the equivalent diameter of the exhaust pipe and reducing the length of the pipe are the key points of design of the vacuum exhaust passage, and the utility effect of the new vacuum technology satisfying the principle is demonstrated.