第五讲灰铸铁与球铁缩孔、缩松的形成缩孔和缩松是铸件上常见的一种缺陷。要避免这种缺陷的产生,铸造工人就需要知道铸铁的收缩规律,缩孔和缩松的形成原因,体积的大小、形状及分布的规律,以及掌握防止这些缺陷的工艺措施。一、铸铁的收缩一般的物体具有热胀冷缩的规律。高温的铁水浇入砂型后,从冷却凝固直至降到常温,在这个过程中,体积会出现减小的现象,我们称为收缩。如果我们对收缩过程不采取必要的工艺措施,铸件往往会出现缩孔、缩松、裂 Lecture 5 Gray cast iron and ductile iron shrinkage, the formation of shrinkage Shrinkage and shrinkage is a common casting defects. To avoid such defects, foundry workers need to know the law of shrinkage of cast iron, shrinkage and shrinkage of the reasons for the size, shape and distribution of the rules, as well as master the measures to prevent these defects. First, the general contraction of cast iron objects with thermal expansion and contraction of the law. High temperature hot metal poured into the sand, from the cooling and solidification down to room temperature, in the process, the volume will appear to reduce the phenomenon, which we call contraction. If we do not take the necessary process of contraction process, casting often shrinkage, shrinkage, cracking