ANALYSIS OF CHARGE WELD EVOLUTION FOR A MULTI-HOLES EXTRUSION DIE

摘要

Extrusion process presents two types of welding mechanism inside the die: seam and charge weld. The first type is unavoidable in the production of hollow profiles while the second is generated during billet to billet transition. Differently from seam weld, charge weld represent an unacceptable defect that require profile discard. Nevertheless charge weld extent and location on extrudates is not evident, thus requiring scrap definition by means of time-consuming trials or to repetitive tests on each batch. In the present paper an industrial four holes porthole die for hollow profiles production was investigated during billet to billet transition. Extrusion of four billet was performed under strict parameter control. The profiles were microscopically analyzed in order to determine weld evolution: in particular start and end points of weld for each profile were determined.