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Development of Electromagnetic Pulse
Welding Technique for DMW
P.C.Saroj
[email protected] | (T) +91 22 25595659
Accelerator & Pulse Power Division
Bhabha Atomic Research Centre
Trombay, Mumbai - 400085
Technical Meeting on the Dissimilar Metal Welding Experiences & Lessons Learned
11 - 14 July,2017
IAEA Headquarters, Vienna, Austria
Vienna International Centre (VIC) M-Building Room M2
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Outline of the Presentation
1. Introduction
2. Electromagnetic Pulse Welding Principle
3. Experimental set up & Results
4. Numerical Simulation of DMW
5. Challenges
6. Conclusions
7. Future Plan
8. References
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Nomenclature
Electro Magnetic Welding (EMW)
Electro Magnetic Pulse Welding (EMPW)
Magnetic Pulse Welding (MPW)
Magnetic Pressure Welding (MPW)
Magnetic Impulse Welding (MIW)
Electromagnetic Pulse Technology (EMPT)
Electromagnetic Pulse Metal Processing Techniques
(EPMPT)
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Introduction
Conventional welding processes show difficulties in joining
dissimilar metal combinations due to difference in M.P.
In contrast; EMP welding technology allow welding between
dissimilar metal by plastic deformation without melting of
base metal
The metallurgical bond is produced without fusion;
mechanical and chemical properties of materials do not
under go liquid–solid transformation.
Produced joint does not adversely affect the heat treatment
and microstructure of metal, so the procedure does not require
preliminary and post-weld heat treatment.
EMW is a solid state welding; that produces a weld by high velocity impact
EMW are more competitive than conventional methods in terms of
Simplicity, environmental friendly and automation
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Equivalent Circuit
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Principle of EMP Welding Technology
Cross Section of Graphic depicting the Tool Coil and Work piece
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Schematic of MPW Process of two tubes (Source: MPW, Manual, LISBOA-2010)
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EM Technology: Potential Applications
across Various Sectors
Automobile Sector
Electrical Industry:
Crimping ..
Ship Building Industry
Aluminum Fabrications in
any Industry
Dissimilar Materials
Advance Core and
Cladding Steel
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Lug Crimping
Courtesy: Trans. Am. Nucl. Soc. (USA)
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Experimental Setup (40kJ, 20kV)
EM Tool (6 Disc Coil
with Field Shaper)
Schematic Block Diagram EM Forming /Welding System
Power
Supply Capacitor
Bank
EMM Tool
4 Disc Coil
without Field Shaper
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4 Disc Coil and Field Shaper For
D9/T91 Tube to SS304 Plug Weld Trial
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Weld Analysis of D9/T91 tube to SS304 plug
Indicative sample of
D9/T91 steel to SS304
EMW sample.
Micrograph of welded sample
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Casted sample
Polished and etched
with Oxalic acid
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Burst Test of EM Welded Sample
• EM welded D9 clad to SS304 end plug,
tube ruptured at TIG welded joint @110MPa
• EM welded joint is also stronger than TIG
welded joint, this could be due to heated
affected zone.
• This proves the superiority of solid state
high strain welding.
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The Sample was subjected to hydraulic
pressure test using Maximator make,
German test Equipment (Capacity: 400Mpa)
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4 Disc EM coil
Current waveform
Pressure on Copper
tube
Dimension
(AL tube)
Measure
(mm)
Dimension
(Cu Disc)
Measure
(mm)
OD 48 OD 44
ID 44 Length 25
Thickness 2 Stand off 2
Weld
length
20 Weld length 20
EM Pulse Welding of Copper tube to Soft Iron
Geometry and Dimensions
Joining of soft iron to copper proves to be very beneficial for several industrial applications. Conventional fusion welding method, by applying the thermal energy to melt these two metals and fuse together leads to unreliable weld due to vast difference in melting points. It is difficult to remove oxide layer on Al. Alloying of the two metals creates a brittle inter-metallic compound that is mechanically and electrically poor in quality.
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Test Results of Cu tube to Soft Iron weld
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Samples of copper tube and
soft iron
Optical Micrograph of
interface
Pull out test
Helium Leak test
Interface penetration of
copper and iron using XRD
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Experimental Setup for Flat Sheet Welding
LOAD COILS
CAPACITOR
SPARK GAP
Source: APPD, BARC, Bombay & Dr. Sachin D. Kore, IIT Guwahati
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Upper
Coil
Lower Coil
Plate
s
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EM Welded Samples Test Results
Al to SS
Cu to SS
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Al to Al-Li
Al to AZ 31
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Numerical Simulation Test Results
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Min Velocity of
Impact for Al-SS
Simulations were performed at various applied voltages,1 kV to 9 kV. There is an increase in the depth of
deformation with the increase in applied voltage.
At 8kV At 5kV At 9kV
Rebounding
Effect
Work piece was not getting full deformation at 5kV. This may be due to non-uniform distribution of magnetic
field and increased stiffness of the work piece.
Depth of forming was increasing from 35 mm at 5kV to 44.7 mm at 8kV.At 9kV, the depth of deformation
decreases, this is due to the rebounding effect.
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Depth of deformation Vs applied voltage
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Challenges involved
Electrically Failed direct coil MSE & Failure in direct coil
• Mechanical & Elect properties change with increase in
temperature.
• Increase in tempt. Magnifies the joule heating effects.
• Magnetic Saw effect (MSE) is due to molten metal pushed away by
magnetic field, resulting in the damaged surface of the FS with saw
like marks.
MSE in Be-Cu FS
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Be-Cu Field Shaper with replaceable
Copper Insert after trial
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Methods to Reduce Magnetic Saw Effect (MSE)
Use of material with high melting point like Tungsten/ Tantalum etc.
Use of a coil of higher inner radius compared to skin depth.
Complete elimination of irregularities or pre- existing cut in the inner
surface of the coil.
Use of liquid N2 for cooling to reduce the MSE.
Use of a Multilayer or Spiral coil to reduce the characteristic surface
temperature.
To over come MSE, high field zone is to be replaced by disposable
Inserts viz Tantalum, Copper Tungsten, Niobium, AISI316 steel,
P91, AA2014 and ETP copper. Among these Copper showed most
promising results in terms of the quality of the joint.
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Conclusion
EM Pulse Welding of Dissimilar Metal have been demonstrated
for various combinations and sizes of metals
Optical Micrograph and SEM showed good metallurgical bonding.
High strength Disc coil and field shapers have been developed
At high field (~40T), magnetic sawing effect /deformation are seen on
Field shaper
Disposable field shaper at higher(>45) pulse field may be deployed
In case of Flat sheet; at higher voltage, the depth of deformation
decreases due to rebounding effect.
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Future Plan
Analysis of Failure mechanism of tool coil and mitigation technique
Simulation of EMW interface under high strain rate for Dissimilar
Metals
Optimisation of electrical and mechanical parameters for DMW
Inspection and Repair of EMW to be devised
EM pulse welding seems to be a potential technique for DMW for
high strength steels such as ODS steel (generation IV cladding
Material) retaining its metallurgical characteristics
Testing of EMW samples in reactor environment
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References
1. Proceedings of the 17th International Conference on Nuclear Engineering ICONE17 , July 12-16, 2009, Brussels, Belgium
ICONE 17-75630 Electromagnetic Pulse Technology as means of Joining Generation IV Cladding Materials, John McGinley,
European Commission, JRC-ITU ,Karlsruhe, Germany.
2. “20 kV, 40 kJ Electromagnetic Manufacturing Machine"; P.C. Saroj, M.R. Kulkarni, Vijay Sharma, Satendra Kumar and
L.M. Gantayet, BARC Report Internal Report, 2012.
3. “20 kV, 40 kJ Electromagnetic Manufacturing Machine for Forming and Welding applications”, P.C. Saroj, M.R. Kulkarni,
Satendra Kumar, et.al., Annual Welding Seminar on 23rd November 2013 organized by IIW-Mumbai branch.
4. S.D. Kore, P.P. Date, S.V. Kulkarni, Electromagnetic impact welding of aluminum to stainless steel sheets, Journal of
Materials Processing Technology, Volume 208, Issues 1-3, 21 November 2008, Pages 486-493.
5. “Synchronization and reliable operation of triggered spark gap switches in 40 kJ, 20 kV EMM system”, Saroj, P.C. et.al
Page(s): 353 – 355, ISDEVI 2014.
6. “Copper, Iron weld techniques evaluation using helium leak rate”; Satendra* Kumar, T.K. Shah#, P C Saroj*, M R Kulkarni*,
and Archana Sharma*. *APPD, #L&PTD, BARC, Trombay, Mumbai; National Symposium on vacuum techniques &
applications to electron beam (IVSNS-2015) paper No. 15, November 2015
7. Metallurgical & Mechanical Testing of Electromagnetically welded copper and Iron sample; Satendra Kumar, M R Kulkarni,
P C Saroj et al;14th Asia Pacific Conference on NDT – Mumbai, India (apcndt2013.com)., page No.
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