【摘要】 鉴于液态补缩机制不能解决大高径比铸件中心缩孔疏松缺陷,提出了固态补缩机制.通过分析金属液静水拉力对内孔形核和固相屈服变形的作用,阐明了固态补缩机制的原理,并得出了影响铸件固态补缩能力的主要因素:液体破裂压力值、金属液气体含量以及固相屈服强度.在此基础上,提出了降低铸件在径向上的温度梯度是减少大高径比铸件缩孔疏松缺陷的有效方法.最后,设计了铸件在不同模具温度下凝固的验证实验,证实了固态补缩对于减少大高径比铸件缩孔疏松的作用.更多还原

【Abstract】 Shrinkage porosity is one of major defects in castings, which seriously influences the quality of the castings. In general, the common method to eliminate this defect is to increase the liquid feeding ability of the casting through setting a riser in the corresponding position. However, for the casting with large height-to-diameter ratio, narrow and long feeding channel increases the flow resistance of the liquid metal in the late stage of the solidification. It is difficult to achieve a long-range liquid feeding, and the effect of the feeding is very little. Therefore, the penetrated shrinkage porosity in axis is frequently produced in the continuous casting ingots with large height-todiameter ratio and large cross- section. As the liquid feeding mechanism has no effect on this problem, the solid feeding mechanism is proposed. First, the solid feeding mechanic is clarified by analyzing the effect of the hydrostatic tense stresses on the pore formation and the solid deformation. In addition, the ability of the solid feeding is determined by the value of the fracture of liquids, the content of the gas solute in liquid metal and yield strength of the solid. Then on the basis of this mechanism, reducing the temperature gradient in the radial direction of the casting is proposed to enhance the solid feeding ability. Finally, a verification experiment was conducted, and the results proved the function of the solid feeding on eliminating the shrinkage porosity defects.更多还原