Prediction of charge welds in hollow profiles extrusion by FEM simulations and experimental validation

In direct extrusion of aluminum alloys, billets are discretely loaded into the press and joined by the high hydrostatic pressure field. The contamination of the billet-to-billet interface by oxides, dust, or lubricant produces a welded zone (charge weld) with reduced mechanical properties that requires profile discharge. For an efficient material scrapping, both the position of the transition zone and its extent in the profile must be accurately identified. In industrial practice, in relation to a lack of experimental and numerical studies on this specific matter, the determination of the zone to be discarded is still performed mainly by experience or labor-intensive analyses. The aim of the present study is to bridge this gap by investigating the evolution of the charge welds inside an industrial multi-profiles and determining their exact position and extension by experimental microstructural analyses coupled with comprehensive 3D FE simulations performed with the Arbitrary Lagrangian–Eulerian code HyperXtrude®. Skin and rest defects are also experimentally investigated and a numerical sensitivity study on the influence of the friction model selection is performed. Comparison between numerical and experimental results shows a good agreement both in terms of general trend and exhausting points of the charge welds. The results prove that the FE code is a reliable tool in assisting and driving the die and process design stages, not only for process optimization as reported in literature but also for the scrap length determination. Finally, a process efficiency index is defined and, for the specific case study, it is found to be increased from 82.6 %, as resulting from the actual industrial practice, to a 88.3 % as optimized by the performed coupled experimental and numerical activities.

[1]  J Lof,et al.  FEM simulations of the extrusion of complex thin-walled aluminium sections , 2002 .

[2]  I. Flitta,et al.  Nature of friction in extrusion process and its effect on material flow , 2003 .

[3]  Henry Valberg,et al.  Extrusion welding in aluminium extrusion , 2002 .

[4]  Henry Valberg,et al.  Joining of metal streams in extrusion welding , 2009 .

[5]  Guoqun Zhao,et al.  Effect of extrusion stem speed on extrusion process for a hollow aluminum profile , 2012 .

[6]  Hui Zhao,et al.  Simulation of extrusion process of complicated aluminium profile and die trial , 2012 .

[7]  Di Feng,et al.  Oxide distribution and microstructure in welding zones from porthole die extrusion , 2013 .

[8]  Ben Young,et al.  Effects of transverse welds on aluminum alloy columns , 2007 .

[9]  Mehdi Imaninejad,et al.  Mechanical properties and microstructural characterization of extrusion welds in AA6082-T4 , 2004 .

[10]  Zhen Zhao,et al.  Simulation of sheet metal extrusion processes with Arbitrary Lagrangian-Eulerian method , 2008 .

[11]  Mark Jolly,et al.  Finite element modelling simulation of transverse welding phenomenon in aluminium extrusion process , 2003 .

[12]  Jie Zhou,et al.  3d fem simulation of the thermal events during aa6061 aluminum extrusion , 1999 .

[13]  J. Weiner,et al.  Fundamentals and applications , 2003 .

[14]  Lorenzo Donati,et al.  Seam Welds Modeling and Mechanical Properties Prediction in the Extrusion of AA6082 Alloy , 2008 .

[15]  J. H. Hollomon,et al.  Effect of Strain Rate Upon Plastic Flow of Steel , 1944 .

[16]  R. Radev,et al.  About input data selection for the FEM analysis of bulk forming , 2003 .

[17]  Sverre Brandal,et al.  Optimisation of flow balance and isothermal extrusion of aluminium using finite-element simulations , 2011 .

[18]  Barbara Reggiani,et al.  Evaluation of process speed effect in aluminium extrusion by experiment and simulations , 2010 .

[19]  Janusz Dobrzański,et al.  Mechanical properties and structure of the Cr-Mo-V low-alloyed steel after long-term service in creep condition , 2007 .

[20]  Taylan Altan,et al.  Metal Forming : Fundamentals and Applications , 1983 .

[21]  Guoqun Zhao,et al.  Design of a Multihole Porthole Die for Aluminum Tube Extrusion , 2012 .

[22]  Hao Chen,et al.  Numerical simulation and metal flow analysis of hot extrusion process for a complex hollow aluminum profile , 2012 .

[23]  Lorenzo Donati,et al.  The effect of die design on the production and seam weld quality of extruded aluminum profiles , 2005 .

[24]  Peng Liu,et al.  Die structure optimization for a large, multi-cavity aluminum profile using numerical simulation and experiments , 2012 .

[25]  Janis Kandis,et al.  Metal Flow in Two-Hole Extrusion of Al-Alloys Studied by FEA with Experiments , 2012 .

[26]  Jie Zhou,et al.  FE analysis of metal flow and weld seam formation in a porthole die during the extrusion of a magnesium alloy into a square tube and the effect of ram speed on weld strength , 2008 .

[27]  Stefania Bruschi,et al.  Physical Simulation of Longitudinal Welding in Porthole-Die Extrusion , 2006 .

[28]  Lorenzo Donati,et al.  Seam Welds in Hollow Profile Extrusion: Process Mechanics and Product Properties , 2008 .

[29]  Henry Valberg Understanding metal flow in aluminium extrusion by means of emptying diagrams , 2010 .

[30]  Taylan Altan,et al.  Prediction of Temperature Distributions in Axisymmetric Compression and Torsion , 1975 .

[31]  Lorenzo Donati,et al.  Characterization of seam weld quality in AA6082 extruded profiles , 2007 .

[32]  Santosh Kumar,et al.  Die design and experiments for shaped extrusion under cold and hot condition , 2007 .

[33]  C. L. White,et al.  Effect of specimen orientation and extrusion welds on the fatigue life of an AA6063 alloy , 2010 .

[34]  A. N Levanov,et al.  Improvement of metal forming processes by means of useful effects of plastic friction , 1997 .

[35]  Lorenzo Donati,et al.  Friction model selection in FEM simulations of aluminium extrusion , 2010 .