Investigation of variants of deep drawing of steel hollow parts

Deep drawing of hollow parts of various configurations from sheet blanks is widely used in the production of machines, devices, aircraft and household goods. The complexity of the process mechanics and the diversity of technological methods of deep drawing are the reason for the significant attention of researchers to the problems of development and effective using advantages of deep drawing processes. Along with the traditional task of predicting the force regime of the deep drawing process, a number of works are devoted to the geometric accuracy of products and the conditions for obtaining products without defects in the form of cracks, folds and uneven thinning of the walls. Selection of optimal parameters and shape of tools for deep drawing is one of the promising directions for intensification of this technology. The purpose of the work was to evaluate the possibilities of variants for deep drawing of steel hollow parts using traditional and profiled tools, to reduce the power parameters and to decrease the unevenness of the wall thickness of the parts along height. To simulate the deep drawing processes for three variants of using deforming tools (traditional tools, profiled die and blank holder and three profiled tools), the finite element method with next experimental verification of the results was used. For the considered deep drawing process variants, the dependences of deep drawing and blank holder forces vs the stroke of the punch were obtained, the stress–strain state at the maximum deep drawing force was assessed, and the final deformed state as well as the shape and dimensions of the semi-finished products were determined. It has been found that the using a die and a blank holder of special profile for deep drawing process makes it possible to reduce the deformation force compared to traditional deep drawing. The use of profiled deforming tool also provides a more intensive working of the metal structure by cold plastic deformation and, as a result, an improvement of the product strength properties. It was shown that the use of a punch of a special profile ensures the appearance of a pulling force acting on the wall of the deformed workpiece during deep drawing, which leads to a decreasing the tensile force on the bottom of the workpiece and reducing chance of the bottom tearing off. It was additionally revealed, that using profiled punch makes it possible to decrease the gap between the punch and the die, reduce the variation of wall thickness along the height, and also eliminate the curvature of the wall in the semi-finished product. The obtained calculated data on the deep drawing forces and thinning of the sheet blank were confirmed by the results of experiments in manufacturing hollow parts. Hollow steel parts of cup type, obtained by deep drawing, were used as semi-finished products in manufacturing the heating water containers by welding.