Development of forging processes using intermediate workpiece profiling before drawing: research into strained state

Abstract

The purpose of this work is a study of strain distribution in a workpiece body during billet profiling with convex wedge dies with different angles and degrees of reduction followed by a drawing operation with flat and cut dies. This development of a new forging process was focused on an increase in quality of large forged parts. A conceptual design of this process for working of large workpieces without an upsetting operation has been proposed. The proposed process leads to the accumulation of a high level of strain in the workpiece without significant reduction of the cross-sectional area. It has been found that an increase in convex dies angle and an increase in deformation depth lead to a linear growth of strain in the forging’s body. It was shown that the following drawing of the profiled workpiece with a concave cross-section by flat dies causes a decrease in deformation force by 2–3 times in comparison with drawing by cut dies. An optimal die shape for the achievement of a uniform strain distribution has been established. It was found that the die wedge angle must be in the range of 150°–165°. The necessary parameters for deformation without upsetting operation have been determined. The degree of billet reduction by the convex dies must be in the range of 20–30%. The drawing after profiling must be carried out with flat dies. The orientation of the workpiece in the flat dies must be “edgewise”. The strain state in the workpiece body has been investigated using FEM and a combined theoretical/experimental method of coordinate gridlines. The prime novelty and originality of the present research are the establishment of an optimal convex die geometry for profiling and die configuration for the follow-on drawing process, as well as the determination of the mechanical deformation required for obtaining a uniform strain distribution in the forged workpiece. A forging process for pressure working of large workpieces by convex wedge dies without using upsetting has been introduced. This novel forging process results in an increase in productivity of 17–25%. The heat energy loss was decreased from 6 to 4. The derived results have confirmed the feasibility of eliminating the upsetting process previously required. The forging process time has been decreased by 20%. Energy consumption required for deformation was reduced by 15%. Practical recommendations, derived from the present investigation, have been implemented at the Public Joint Stock Company “Novokramatorsky Mashinostroitelny Zavod”.