The Research On The Drawing Of FVS0812 Hemisphere-shaped Workpiece

The heat-resistant Al-Fe-V-Si alloy (FVS0812) has drawn wide attention due to its excellent high-temperature properties over the range of 423K to 623K on a specific strength basis. In the present study, the forming theory and technology of the FVS0812 sheet as hemisphere-shaped workpiece were investigated.The FVS0812 sheet was prepared by spray deposition- rolling process. The tests on the drawing-ability of the sheet showed that the coefficient of elongation and plastic strain ratio were low and yield ratio .was high, which meant that the drawing-ability of FVS0812 sheet was bad. At the same time, there were other factors which made the drawing of FVS0812 hemisphere-shaped workpiece a difficult task, such as a low relative-thickness coefficient about 0.2%, a complex shape of the product and the difficulty in maintenance of an uniform temperature in workpiece during drawing.The author developed a novel drawing technology named as "packed -layer drawing" The characteristics of packed - drawing technology lay in that the FVS0812 sheet was coated by two layers of thicker metal sheets with high strength, good elongation. The three-layer sheets were darwed together. The thicker packing sheets could prevent wrinkling of FVS0812 sheet. The drawing-ability of FVS0812 sheet was improved greatly by "the effect of friction preservation" and "the effect of zero frictional resistance" which made the deformation in sheet scattered uniformly. Moreover, the packed sheets could reduce the heat loss of FVS0812 sheet in warm drawing or heat drawing. Experiences showed "packed -layer drawing" was a successful method in drawing of FVS0812 sheet.The winkling model in the process of drawing was developed on the base of Hill's bifurcation-point bulking theory, which became the theoretical basis of the analysis of flange wrinkle and side-wall wrinkle. In addition, a critical side-wall wrinkle BHF(blank holding force) model of the hemispherical workpieces in the drawing process was established on the basis of the energy method in the shell theory. Critical side-wall wrinkle BHF of hemispherical workpieces during the drawing process could be calculated according to this model. An apparatus to adjust BHF on single-acting hydromechanical press was designed by the author based on the BHF model Experimental results showed that this device was useful in avoiding wrinkling during drawing.Based on the winkling model and the BHF model the FVS0812 sheet as hemisphere-shaped workpiece was drew successfully by "packed -layer drawing".