一、前言这种既像气孔又更像缩孔的气缩孔,在生产中经常可以碰到。因此,弄清气缩孔形成原因,是一件很重要的工作,对进一步提高铸件质量有重大意义,而且对铸件质量有决定性影响的造型工艺和熔炼工艺的设计有指导价值。二、气缩孔产生的部位及其特征根据多年来在生产实践中的观察,对气缩孔产生的部位及其特征有了一些初步的了解。我厂350型柴油机缸盖,毛重230公斤,外形尺寸610×560×295毫米,材质HT28—48,铁水在HG×-3型三相电弧炉中熔炼,于型浇注。1978年6月以前成份控制为C2.8～3.1％、Si1.5～1.8％、Mn0.8-1.0％、P和S均小于0.1％。图一是汽缸盖的局部结构。在孔φ129周围4个螺孔中,发现1号位置螺孔在水压试验时经常漏水,而2、3、4号位置的螺孔却没有漏水现象。进行解剖检查,发现在1号螺孔搭子部位存在严重的缩松,有的已在搭子热节中心形成了较大的 I. INTRODUCTION This kind of shrinkage hole which is more like stomata and shrinkage cavity can often be encountered in production. Therefore, to clarify the formation of gas shrinkage hole is a very important work, to further improve the quality of castings is of great significance, but also has a decisive impact on the quality of the cast molding process and smelting process design has guiding value. Second, the site of the production of shrinkage and its characteristics According to years of observation in the production practice, the site of the production of shrinkage and its characteristics have some preliminary understanding. I 350 diesel engine cylinder head, gross weight 230 kg, dimensions 610 × 560 × 295 mm, material HT28-48, hot metal in the HG × -3 type three-phase electric arc furnace smelting, in the type of casting. Before June 1978, the components were controlled to C2.8 ~ 3.1%, Si1.5 ~ 1.8%, Mn0.8 ~ 1.0%, P and S were less than 0.1%. Figure 1 is the cylinder head of the local structure. In the hole φ129 around 4 screw holes, screw holes No. 1 location found in the water pressure test often leaks, while 2,3,4 position screw holes did not leak. Anatomical examination found that there is a serious shrinkage in the No. 1 screw hole taking part, and some have formed a larger