Process analysis for magnetic pulse welding of aluminium-copper - PowerPoint PPT Presentation

Process analysis for magnetic pulse welding of aluminium-copper joints Verena Psyk, Christian Scheffler, Maik Linnemann, Dirk Landgrebe I 2 FG workshop on impulse metalworking 2016 December 1 st -2 nd , 2016 Nantes, France 1

Agenda • Introduction to the JOIN’EM project • Process analysis for magnetic pulse welding of aluminium-copper joints • Setup and process parameters • Welding experiments • Characterisation of the joint • Correlation of adjustable process parameters and weld quality • Quantification of collision parameters via numerical simulation • Correlation of collision parameters and weld quality • Summary 2

JOIN’EM – facts and figures • Titel JOIN ing of copper to aluminium by E lectro M agnetic fields • Acronym JOIN’EM • Duration 01.09.2015 - 31.08.2018 • Budget 4.7 Mio. € * • Grant 4.1 Mio. € • Coordinator Fraunhofer IWU (Dr.-Ing. Verena Psyk) • Project partners *Word cloud designed using Tagxedo 3

JOIN’EM – overall aims • Supplementing the heavy use of full copper 4.0 3.5 components in applications related to electrical and 3.0 Price in €/lb thermal conductivity by hybrid copper – aluminium 2.5 2.0 Copper solutions 1.5 � Reduce material costs 1.0 0.5 Aluminium 0 � Reduce product weight Jan Jul Jan Jul Feb Nov 2000 2002 2005 2007 2010 2013 (Source: www.infomine.com) • Development of a flexible, highly productive, and cost effective joining process for high quality Copper Aluminium dissimilar material joints Electrical � magnetic pulse welding (MPW) 58 MS/m 36 MS/m conductivity Thermal • Enabling the industrial implementation of MPW and 401 W/mK 236 W/mK conductivity facilitating the exploitation of known process Density 8.9 g/cm³ 2.7 g/cm³ Price 4.478 €/ton* 1.550 €/ton* advantages in series production (Source: http://www.boerse-online.de/rohstoffe; 2016-11-04) 4

JOIN’EM – objectives • Experimental and numerical process Fields of application and suggested demonstrators analysis and design ����������� ���������������������� • Development of validated process and ��������������� joint design concepts • Development of multiscale simulation strategies • Development of optimized tools for Source: Calyos Source: Whirlpool HVAC industrial implementation ������� ������� • Development and automation of non- destructive testing and quality control Source: Refco • Design, realization, and evaluation of ������������������������������� industrial demonstrators • Economic process and product evaluation Source: Cegasa via life cycle cost analysis 5 Source: Alke

Setup and process parameters Parameters considered for detailed investigation Experimental setup Coil conductor Capacitor charging energy E (10 up to 40 kJ) Flyer thickness t flyer (0.3 up to 1.5 mm) Initial gap between flyer and target g initial Spacer Flyer (1.0 up to 3.0 mm) (Cu-DHP) x-position of the flyer edge x flyer Target (-2 up to +2 mm) (EN AW-1050) Support Fixed parameters Tool coil Capacitance C (300 µF) Target thickness t target (2 mm) x-position of target edge x target (14 mm) Free length l (16 mm) L active = 100mm Width of flyer and target w flyer = w target (100 mm) 6

Welding experiments 800 Tool coil (housing) 600 Current I in kA 400 Flyer 200 Fixture (adjustable 0 in height) -200 -400 0 5 10 15 20 25 30 EN AW-1050 Time t in µs Cu-DHP Capacitor charging energy 10 kJ 15 kJ 20 kJ 30 kJ 40 kJ Exemplary welded part 7

Characterization of the joint Position of specimens in the hybrid sheet Specimen no. weld • Electrical resistance 1 10 measurement micrograph • Lap shear test 2 75 100 • Metallographic 3 analysis 190 Target: EN AW-1050 Flyer: Cu-DHP 8

Characterization of the joint Measurement points • Electrical resistance measurement Resistance � � � • Lap shear test Imposed current: I =4 A � Measurement of voltage drop U • Metallographic • analysis Resistance of the joining partners is negligible if measurement points are close to the joining zone. � Calculated resistance corresponds to resistance of the joint. 9

Characterization of the joint Failure cases Failure in the joint Failure in the copper Failure in the alumi- (occurs for all flyer base material nium base material thicknesses) (occurs for flyer thick- (occurs for flyer thick- nesses of 0.5 mm only) nesses ≥ 1 mm) • Electrical resistance measurement • Lap shear test Cu-DHP EN AW-1050 Cu-DHP EN AW-1050 Cu-DHP EN AW-1050 • Metallographic 3 3 3 analysis Base material Force in kN aluminium Base material Base material 2 2 2 copper aluminium aluminium copper copper 1 1 1 Hybrid Hybrid Al-Cu part Al-Cu part Hybrid Al-Cu part 0 0 0 0 10 20 30 0 10 20 30 0 10 20 30 Elongation in mm Elongation in mm Elongation in mm All cases: Welding of copper flyers to aluminium targets 10

Characterization of the joint Cu-DHP EN AW-1050 • Electrical resistance measurement • Lap shear test Width of the weld • Metallographic Start of the weld analysis End of the weld 11

Correlation of adjustable process parameters and weld quality Maximum transferable force in a lap shear test is considered for mechanical joint characterisation 3 Pre-selected value: Pre-selected value: Pre-selected value: Pre-selected value: Transferable =30 kJ =1 mm =3 mm =-2 mm E t Flyer g initial x flyer 2 F in kN force 1 0 2 Reference value of a non-welded (clamped) connection resistance R in µΩ Joint 1 0 4.5 w weld in mm Weld width 3.0 1.5 0 5 15 25 35 45 0 0.5 1.0 1.5 2.0 0.5 1.5 2.5 3.5 -3 -1 1 3 Capacitor charging Flyer thickness Initial gap width x-position of the energy in kJ in mm between flyer and flyer edge in mm E t Flyer x flyer target in mm g initial 12

Numerical modelling Experiment Coil conductor Flyer: AW1050A H14/24 (CuCrZr) Flyer (Cu-DHP) Target: Cu-DHP R240 Target V109: 30kJ, 544kA, 22.2kHz, t flyer =2, gap=3, x=-2 (EN AW-1050) Support Corresponding Coil conductor macroscopic simulations (CuCrZr) 12 20 Flyer: AW1050A H14/24 15 12 Target 0.5 V109: 30kJ, 544kA, 22.2kHz, t flyer =2, gap=3, x=-2 Support (EN AW-1050) Flyer (Cu-DHP) 13

Numerical calculation of collision parameters Impacting velocity v impact in m/s 500 v impact α impact α α α Coil conductor 400 d = 0 (CuCrZr) 300 Flyer Target Flyer (Cu-DHP) Coordinate d 200 100 Target 0 (EN AW-1050) 0 2 4 6 8 10 12 14 Distance to flyer edge d in mm Support 50 Impacting angle α impact in � Process parameters Coil conductor Capacitor charging energy: 30 kJ (CuCrZr) 40 12 20 Initial gap flyer / target: 3mm Flyer 30 Material: Cu-DHP 15 Thickness: 1 mm 12 20 Edge position: -2 mm Target 10 Material: EN AW-1050 Thickness: 2 mm 0 0 2 4 6 8 Edge position: 14 mm Target 0.5 Distance to flyer Support edge d in mm (EN AW-1050) Flyer (Cu-DHP) 14

Correlation of adjustable process parameters and collision parameters v impact Collision parameters at a distance of 2 mm from the flyer edge are α considered because typically this area is welded if welding occurs at all. 2 mm Target Impacting velocity 800 Pre-selected value: Pre-selected value: Pre-selected value: Pre-selected value: E =20 kJ t flyer =1 mm g initial =2 mm x flyer =0 mm 600 v impact 400 200 0 80 Impacting angle 60 α impact 40 20 0 5 15 25 35 45 0 0.5 1 1.5 2 0.5 1.5 2.5 3.5 -3 -2 -1 0 1 2 3 E in kJ t flyer in mm g initial in mm x flyer in mm 15

Correlation of collision parameters and joint quality Maximum transferable force in a lap shear test is considered for mechanical joint characterisation 3 Force F in kN Transferable Pre-selected value: Pre-selected value: α impact =15 � v impact =400 m/s 2 1 0 Resistance 1.5 R in µΩ 1.0 0.5 0 6 w weld in mm Weld width 4 2 0 200 300 400 500 0 10 20 30 40 Impacting velocity v impact in m/s Impacting angle α impact in mm 16

Summary • JOIN’EM aims at reducing the heavy use of copper to reduce cost and weight. • Hybrid aluminium copper parts shall replace current full copper solutions. • MPW is a promising technology for manufacturing copper aluminium joints. • An experimental and numerical process analysis considering MPW of aluminium copper joints has shown that high quality joints require by trend • high impacting velocity (i.e. >250 m/s for welding of Cu-DHP and EN AW-1050) and • low impacting angle (i.e. 5°-20° for welding of Cu-DHP and EN AW-1050). • The impacting velocity is higher if • high capacitor charging energy (and consequently higher force) is applied and • the flyer thickness (and consequently the flyer mass to be accelerated) is low. • The impacting angle is lower if • the initial gap width between flyer and target is small and • the overlap of flyer and tool is relatively long. 17

Acknowledgement The JOIN’EM project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 677660. 18