TECHNICAL ASPECTS REGARDING THE MANUFACTURING OF TUBULAR PARTS USING COLD REVERSE EXTRUSION

Abstract

Processing of metals by cold pressing acquires an increasingly wide application, because of its proved benefits: low metal and energy consumption, high productivity, low costs and the possibility to achieve high precision products. In this context, cold metal extrusion can be considered as a leading process which offers the possibilities that a few years ago were unimaginable.

This paper presents design problems with practical character, the execution problems of the extrusion dies and considerations regarding the technical equipment, which contribute to the product realization. In comparison with other procedures, the reverse extrusion assures high productivity, very efficient material utilization and reduced workload.

Also due to the hardening of extruded material, the finished parts have superior mechanical characteristics. The high complexity of the process required extensive theoretical and experimental research over the years, resulting in widening the range of products manufactured.

Obtaining a good quality of the extruded products requires a good knowledge of the properties that characterize the formability of metallic materials, plasticity and their resistance to straining, and also their dependence on the conditions in which the extrusion takes place. Most of the parts obtained by reverse extrusion have axial symmetry, but under certain conditions, irregular parts can be also extruded. In this case, the center of the technological forces should be placed on the tool axis. Theoretically, all metals and their alloys can be processed by cold extrusion; however, in practice, using different metals and alloys is conditioned by their formability. The specific pressure required for extrusion should not exceed (2000 ... 2500) N/mm², a value that provides good durability for the tools and a load of the equipment within acceptable limits.

Key words: extrusion, reverse extrusion, extrusion technology.