Experimental studies of isothermal flanging of blanks with an inclined flange

The results of experimental studies of power modes and wall thickness of branch pipes with inclined flange obtained by isothermal flanging under conditions of slow hot deformation are presented. Aluminum alloys AMg5 and D16 were used as the material of the blanks. Blanks with a constant outer diameter and a variable hole diameter were obtained from sheet metal by laser cutting. During the experiment, the following parameters were varied: the angle of inclination of the working plane of the dies to the horizontal plane, which was 10, 15 and 20 degrees, for which a set of three dies with clamps with appropriate angles of inclination was made; the degree of deformation, which was changed by changing the inner diameter of the hole in the blank at a constant punch diameter; the rate of deformation, which was 0.01 and 0.001 s–1. Ensuring a given rate of deformation was achieved by setting the speed of punch movement in accordance with the calculated degree of deformation. Flanging was carried out on a certified P5 testing machine equipped with a computerized traverse speed control system with a load-displacement graph. The blank was heated together with the die tooling by an annular ceramic electric heater to a temperature of 400 ± 5 oC. The isothermal conditions were ensured by the presence of a thermal insulation casing and regulated by a temperature controller that maintains the set temperature in a preset range. The thermal insulation casing consisted of two shells made of corrosion-resistant steel, the space between which was filled with asbestos cloth. According to the results of the performed studies, the dependences of the maximum flanging force on the degree of deformation at different values of the angle of flange inclination and the rate of deformation were obtained. It is established that a decrease in the speed of the operation leads to a decrease in the technological force, which is explained by the manifestation of the viscous properties of the material in the given temperature and speed conditions. An assessment of the amount of thinning of the branch pipe edge part by its generatrix showed that different areas of the edge part thin to varying degrees. To eliminate the uneven thickness, an additional isothermal piercing is required.