液压件铸件气孔缺陷的形成原因及防止措施

Causes and Preventive Measures of Blowhole Defects in Hydraulic Castings

液压件铸件内腔形状复杂、尺寸精度要求高,砂芯常用覆膜砂制作。气孔是该类铸件常见缺陷之一,具体表现为表面气孔、重皮、呛火等形式,主要是由于砂芯发气量大所致。以液压件后盖为例,对铸件的气孔缺陷形成原因进行了分析,然后以“排、减、溢”为原则,提出了防止铸件气孔缺陷的具体措施,包括加强芯头排气、砂芯减重、制芯后二次烘烤、提高浇注温度、设置溢流冒口等。

The shape of inner cavities in hydraulic castings is complex and high dimensional precision is required.Their sand cores are usually made of precoated sand.Blowhole is one of the common defects in such castings,which is manifested as surface porosity,double skin,boiling,and so on.It is mainly due to the large gas generation of sand core.In this paper,firstly taking the back cover as an example,the causes of blowhole defects in hydraulic castings were analyzed,and then the specific measures to prevent the blowhole defects were proposed based on the principle of“discharge,reduction and overflow”,such as strengthening the gas exhaust from core heads,reducing the weight of sand cores,secondary baking of sand cores,increasing the pouring temperature and setting the overflow riser.