APPLICATION OF MAGNETIC PULSE WELDING (MPW) FOR ALUMINIUM ALLOYS AND SPCC STEEL SHEET JOINTS

Transcription

1 APPLICATION OF MAGNETIC PULSE WELDING (MPW) FOR ALUMINIUM ALLOYS AND SPCC STEEL SHEET JOINTS Tomokatsu Aizawa, Mehrdad Kashani and Keigo Okagawa Tokyo Metropolitan College of Technology, Department of Electronics and Information Engineering, Shinagawa-Ku, Tokyo, Japan.

2 OUTLINE 1) Introduction 2) MPW Principle 3) Experimental Setup 4) Experimental Results 5) Conclusions 6) Future Plan

3 1) Introduction Hybrid structures of aluminium alloy and steel are suggested for reducing the weight of automobiles to improve fuel efficiency and control air pollution. Therefore, joining steel and aluminium alloy in different shapes is receiving attention Factor Machinability Aluminum Steel(=1) Melting Point Density Thermal Electrical Conductivity Conductivity Comparison of Aluminium and Steel

4 1) Introduction History: Magnetic Pulse Welding process was developed in the late 1960s and early 1970s for nuclear energy applications. Russian scientists at the Kurchatov Institute of Nuclear Physics invented a technique for pulsed magnetic welding of end closures of nuclear fuel rods.

5 1) Introduction The magnetic pulse welding (MPW) is a cold weld process of conductive metals to the similar or dissimilar material such as Aluminium alloys to SPCC-Steel sheet. The MPW process is a heat-free which can eliminate localized annealing.

6 1) Introduction Magnetic Pulse Welding Benefits and Advantages Use for several dissimilar metals joints combination Eliminates localized annealing Heat-free solid state welding process Less Joint weight Joint interface is stronger than the weakest material No filler material.

7 2) MPW Principle When Steel a high energy current is discharged through a coil the eddy current is produced in the conductive workpiece near Al the coil and the repulsion between the two magnetic forces creates pressure which i xb=f can drive the primary metal against the target metal, thereby Lorentz producing Force a solid-state weld. F Gap Before Welding Coil Steel Steel Al Al i Eddy Current B Magnetic Field Magnetic Field Current Eddy Current Main Current Magnetic Field Coil Coil

8 2) MPW Principle The eddy current i and the magnetic pressure p are given as following: i = Eddy current B = Magnetic Field P = Magnetic Pressure = Electrical conductivity = Magnetic permeability = Thickness = Angular frequency i = κ B t 2 B P ( pressure ) = 1 exp 2 µ δ ( skin depth ) = 2 ωκµ 2τ δ

9 3) Experimental Setup Gap Switch High-Voltage Power supply Coil Bank Capacitor (200µ F, 10kV) Gap Switch Flat Coil Control System Trigger System Bank Capacitor

10 3) Experimental Setup MPW Coil Fe sheet Coil Fe sheet Al sheet Al sheet Magnetic field Coil Magnetic Field Double H-shaped Layer Coil One E-shaped layer Coil

11 3) Experimental Setup The aluminium alloys ( A1050, A2017, A3004, A5182, A5052, A6016, and A7075) and Steel (SPCC) sheets with size of 10x10cm were prepared to carry out the weld testing Number of test pieces Welded Zone 10cm

12 3) Experimental Setup The Aluminium Alloy and SPCC Steel Characteristics Sample Specification A1050 A2017 A3004 A5182 A5052 A6016 A7075 SPCC Conductivity [IACS] Tensile Strength [MPa]

13 3) Experimental Setup System Setup Fixture Gap Before Welding Insulator sheet Steel(SPCC) Al sheet coil Coil Current 5mm 130 mm Current

14 4) Experimental Results 4-1) Discharge Current =0.58mm 490F =0.45mm 210F Skin-Depth Capacito =0.36mm 90F =0.33mm 60F

15 4) Experimental Results 4-2) Al sheet Speed before Collision Al Al sheet sheet speed speed just just before before collision collision (m/s) (m/s) Maximum Discharge Discharge Bank Energy Current (kj) (ka)

16 Number of test pieces 4) Experimental Results 4-5) Tensile Shear Test standard tensile shear testing machine at test rate of 10mm/min 10cm Distribution of tensile shearing strength for 10 divided pieces of welded sample: A1050/SPCC A5052/SPCC A6016/SPCC rupture of non-welded area Welded Zone rupture of welded area

17 4) Experimental Results 4-3) Weld Geometry Steel(SPCC) Al-A1050 Al-A5052 1mm Al-A1050 Eddy current path 1mm Steel(SPCC) Al-A1050 Al-A µm Al-A µm Typical macrostructure of joined interface zone for A1050/A1050 and A5052/SPCC

18 4) Experimental Results 4-3) Weld Geometry SPCC 1mm A6016 SEM image of joined interface for A6016/SPCC sample

19 4) Experimental Results 4-4) Micro-Hardness Profile SPCC A m Berkovich hardness, (mgf/m 2 ) SPCC Interface layer Al Micro-Hardness profile of interface layer for A6016/SPCC

20 4) Experimental Results 4-6) Electron Probe Micro-Analysis (EPMA) SPCC A1050/SPCC CP 5µm A1050 Al 5µm SPCC Al 5µm 10µm Fe 5µm

21 5) Conclusions We can conclude that the solid-state weld quality achievable for most aluminium alloys and SPCC steel combination by using MPW method.

22 5) Conclusions Our experimental results show that the weld joint is always stronger than the weaker metal and in all tested combination a discontinuous or continuous pocket-type, wavy transition layer was formed without any significant heat-affected zone (HAZ).

23 5) Conclusions The capability of our MPW method has been also examined for several other types of metals joint, such as T-joint, circular joint, long sheet work-pieces (up to 500mm) successfully. Holder Al Al sheet coil Magnetic flux

24 6) Future Plan Now we are working on application of MPW for Super Alloy joints and also the design of the compact commercial MPW system for Industrial application. The first compact model

25 Address: Tokyo Metropolitan College of Technology, Department of Electronics and Information Engineering, Shinagawa-Ku, Tokyo, Japan Web: