前言 在铸件中往往存在有缩孔疏松等缺陷。改进浇注工艺如采用离心浇注、高导热冷模浇注等并不能完全消除这种缺陷,有时却会带来其他铸造缺陷如冷隔、微裂纹等,而得不到完全致密的铸件。由于缩孔、疏松缺陷的存在,使某些性能如疲劳、持久下降,使性能波动大而分散,因而使用可靠性也差。这就是为什么在关键动部件较少采用铸件以及一些铸件品率较低的原因之一,在六十 Preface Castings often exist defects such as shrinkage porosity. Improve the casting process, such as the use of centrifugal casting, casting and other high thermal conductivity cold mold and can not completely eliminate this defect, sometimes it will bring other casting defects such as cold, microcracks, etc., and can not be completely dense castings. As the shrinkage, loose defects exist, so that some properties such as fatigue, lasting decline, so that performance fluctuations and dispersion, so the use of reliability is poor. This is one of the reasons why fewer castings are used in critical moving parts and some castings have a lower yield,