Parameter Optimization And Mechanism In The Process Of Warm Fine Blanking

Fine blanking is a metal forming technology developed on the basis of conventional blanking.In comparison with the conventional blanking,fine blanking has the advantages of high shape accuracy,smooth shear cutting surfaces and low surface roughness,so it is widely used in the manufacturing production of aerospace,automotive,electronic components and household appliances.Warm forming refers to the process of plastic deformation during which the temperature is above the room temperature but below the recrystallization temperature.There exists both strong work hardening and the softening of static recovery during the process of warm forming.Therefore the warm forming not only has the advantage of low deformation resistance,but also harbors the character of high precision of cold forming.By combining warm forming and fine blanking process,the role of the temperature in improving the formability of 6061 aluminum alloy sheet is explored.The conclusions are as follows.1)Uniaxial tensile tests are carried out at different temperatures for 6061 aluminum alloy to obtain the stress-strain curves.The results show that the yield strength of the material decreases as the temperature rises and the material softens significantly after heating.2)The effects of temperature,blank holder force and counter force on the shear cutting surfaces of fine blanking parts are explored through fine blanking experiments.This paper creatively put forward a method to assess the quality of the part by calculating proportions of the areas of shiny burnish surface and rough fracture surface in the shear cutting surfaces.By comparing the proportions of the areas of shiny burnished surfaces and rough fracture surface of 6061 aluminum alloy sheet in different temperatures and different blank holder forces and counter forces,it is discovered that the proportion of shiny burnished surface on the shear cutting surface increased and that of the rough fracture surface decreased as the heating temperature increased.When the temperature was raised up to 175°C,the rough fracture surface disappeared and the whole surface became shiny burnished surface.As blank holder force and counter force increased,the proportion of the shiny burnished surface took on increasing trend and that of the rough fracture surface showed decreasing,both with limited effect of improving.3)By observing the distribution of flow line of the shear zone in fine blanking,it is discovered that the second phase within the shear zone is elongated and the shear band is formed as the punch gradually penetrates.The thickness of the shear zone when the punch penetrates 50% of the thickness of sheet is much larger than that when the punch penetrates 20% of the thickness.At the same time when comparison is given to shear bands at different temperatures at the penetration of the punch to 20% of the thickness of the sheet,it is found that crack near the edge appeared at 25°C,but did not occur when at 175°C.When punch penetrates 50%,it is discovered that crack generates and extends almost through the whole shear zone at 25°C,but crack only generates near the edge of the die and not of punch at 175°C.Experimental results show that heating indeed delayed the generation and propagation of cracks.Finally the finite element simulation method is used to verify the experimental results.