Charge Weld Scrap Minimization by Means of Dead Metal Flow Control in Die Design

1. TENTH INTERNATIONAL ALUMINUM EXTRUSION TECHNOLOGY SEMINAR AND EXPOSITION Charge Weld Scrap Minimization by Means of Dead Metal Flow Control in Die Design Tommaso Pinter1, Dan Antonios2, Barbara Reggiani3, Andrea Gamberoni3 1Almax Mori & Alumat, Mori, Italy 2Alexandria Industries Midamerica, Indianapolis, USA 3Università di Bologna, Dipartimento di Ingegneria Industriale (DIN), Bologna, Italy

2. Outline • Why we are here? • State of the art • Numerical model verification for the charge weld prediction • Experimental set-up • The FE model • Comparison between experimental / numerical results • Evaluated die and process design modifications • Comments

3. Because of Charge Weld

4. State-of-the-art Numerical investigations Experimental investigations 2D investigations Qianget al. (2003. Mater Des 24–7,493–496) investigated the formation and evolution of the transition zone at a very early stage of the process (less than 10 mm stroke) Jonanneset al. (1996. 6th ET Seminar (2), 89-94) performed an extensive experimental work that showed how the material scrap can be reduced by changing the ratio of port volume to cross section. Time consuming Expensive Hardlygeneralizableconclusions Zhang et al. (2012, Int J Adv Manuf Technol 60,101–110) focused the study on the oxide distribution at the interface with particular attention to oxides breakings during port filling and seam joining in welding chambers. Duplanĉić and Prgin (1988, 4th ET Seminar (2), 235–240) carried out a comprehensive investigation and showed that charge weld lenght may be shortened by increasing the temperature, reducing the degree of deformation and lowering the height of the die welding chamber, but on a simple round tube with a fixed shape. Mahmoodkhani et al.(2014, Materials 7, 3470-80) computed the thickness and length of the charge welds transition zone for different feeder dimensions and validated the calculation against industrial data. Jowett et al.(2008, 9th ET Seminar, 13–16) investigated nine hollow dies and four solid dies concluding that the flow in the ports should be balanced and that ports volumes should be reduced and designed proportional to the profile cross section in order to the reduce the scrapped material. However, as a further concluding remarks of the work, the paper reports that the ports reduction has the main drawbacks the decrease of the press productivity and increase of the back-end defect. Reggiani et al.(2013, Int. J. Adv. Manuf. Technol. 69 (5), 1855-1872)validated the capability of a commercial FE code to predict the charge weld extension for a complex 3D multi-hole porthole die, finding a good agreement between experimental and numerical data in terms of evolution of the phenomenon and dimensions of the segments to be discarded. Pinter et al. (2015, Materials Today: Proceedings 2 (10), Part A, 4856–4865) showed that the rule of volume reduction properly works, but for a tubular profile symmetrically fed. Aim: investigate the way to minimize the front-end defect by a proper die design modification without affecting the overall process productivity for an industrial hollow profile made of AA6061 aluminum alloy. Yu et al. (2016, JMPT 230, 153–166) proved that the shapes of legs have greatly influences on the charge welds extension and that pointed legs produces shorter welds than those of the profile extruded with square legs.

5. The investigated profile Extrusion Press Profile AA6061 aluminum alloy. Section area of the profile 2496 mm2. 35 MN (10’’ billet container) extrusion press. Alexandria Industries Midamerica

6. Good Metal Sample Front Scrap Experimental Activity • Technique used to identify coring position in extrusions

7. Numerical model verification • Specimens were ground and etched in Tucker’s reagent

8. Numerical model verification • Die design and Seam weld position real expected

9. Numerical model verification • The FE model Bearings definition ALE approach 885090 tet. elements used

10. Numerical model verification • The FE model

11. Numerical model verification • Numerical-experimental comparison

12. Numerical model verification • Numerical-experimental comparison

13. Evaluated die design modifications 1.5* Vports/(profile cross section) ≈ 1 2 Increase Keep Same Reduce Reduce 3

14. Evaluated die design modifications Time 16 sec Time 9 sec Time 25 sec Flow lowering down Flow speed up

15. Evaluated die design modifications Exit flow unbalance Unchanged seam welds quality

16. Evaluated process design modifications • Sensitivity analysis No influence of process parameters Additional investigations required….

17. Conclusions • FE analysis is an accurate tool for the assessment of the charge weld extension in direct extrusion of hollow profiles. • The material scrap is not only a matter of port volume reduction but it is also strongly influenced by the ports shape. • A cylindrical reduction of the ports volume for an asymmetrical profile leads to an increase in both the flow unbalance and charge weld extension. • The dynamic compression of the flow in conical ports, without altering the global volume, results in a lower transition zone. • Empirical formulas reported in literature are not suitable to predict the amount of material scrap. Please use FE analyses! • The charge weld extension and pattern, as numerical predicted by the FE code, is not influenced by the main process parameters (ram speed and billet preheating temperature) and by the extruded aluminum alloy.

18. Thank you for your attention