压射机构是挤压铸造设备的核心部件之一，卡擦现象是影响压射机构正常工作、压室寿命的关键技术难题．文中首先通过有限元方法计算得到压室和冲头半径方向变形量，并对压射机构发生卡擦现象的原因进行了定性分析，发现在挤压铸造工艺过程中，压室和冲头的间隙变小是压射机构发生卡擦现象的直接原因，压室和冲头各个部位的不均匀变形是导致卡擦现象发生的重要原因．基于此，建立了压射机构卡擦现象可靠性分析模型，采用 Monte Carlo 模拟法计算得到 KDJ-250T 挤压铸造机压射机构的卡擦可靠度，提出了压室结构改进方案．结果显示，利用文中提出的卡擦可靠性分析方法可对压射机构工作性能做出合理的评估，也有助于在设计过程中合理选择压室和冲头之间的配合间隙．

 Injection device is one of kernel parts of the squeeze casting equipment,and scrapping phenomenon is a pivotal technical problem that affects the smooth operation of the injection device and the lifetime of the shot sleeve.In this paper,first,the displacements of the shot sleeve and the plunger tip in radius direction are calculated by means of finite element method (FEM).Next,the cause of the scrapping phenomenon is qualitatively analyzed,finding that the scrapping is directly due to the clearance reduction between the shot sleeve and the plunger tip and that the nonuniform deformation of different areas of the shot sleeve and the plunger tip is also an important cause of scrapping.Then,based on the FEM results,a model to analyze the scrapping reliability is set up,and the scra-pping reliability of the injection device of KDJ-250T squeeze casting machine is calculated through Monte Carlo simulation.Finally,an approach to improving the shot sleeve is proposed.The results show that the proposed scrapping reliability analysis method helps to reasonably evaluate the injection device and choose a proper clearance between the shot sleeve and the plunger tip in design process.