铝、镁合金真空低压消失模壳型铸造的缺陷分析

分析了采用泡沫模用精密铸造制壳,并用真空低压浇注成形铝、镁合金铸件的典型缺陷(主要是浇不足和冷隔、孔洞及粘砂缺陷)的行貌特征和形成机理,并提出相应的防治措施。结果表明,浇不足和冷隔缺陷主要由金属液充型速度慢、充型动力不足、浇注温度低等原因造成;孔洞缺陷主要由金属液浇注速度过快、保压压力小或保压时间短,浇注温度高,浇注系统设计不合理及型壳透气性差等原因造成。粘砂缺陷主要由型壳强度低、充型压力和真空度过大、造型型砂粒径大和激冷效果差等原因所致。

Analysis of Formation Mechanism of Typical Defects in Aluminum (Magnesium) Alloys Castings by the Expendable Pattern Shell Casting with Vacuum and Low Pressure

The appearance characteristics of typical defects including misrun and cold shut,porosity as well as sand burning in aluminum(magnesium) alloys were investigated during the expendable pattern shell casting with vacuum and low pressure,and the forming mechanism of these typical defects were analyzed.Finally,the control measures for the corresponding defects were presented.The results show that misrun and cold shut defects are generated as a result of lower filling velocity of the molten metal,insufficient filling capacity and lower casting temperature,etc.The porosity defects occur due to faster pouring speed,lower holding pressure or holding time,higher casting temperature,unreasonable design of the gating system and poorer permeability of the ceramic shell,etc.The sand burning defect is formed because of lower strength of ceramic shell,higher filling pressure and vacuum level,larger particle size and poorer cooling ability of sand.