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Copyright © TWI Ltd 2014
Chris Punshon TWI [email protected] 1
Development of Local Vacuum Technology for the Application of Power Beam Welding to Massive
Structures
SMEA Sheffield Metallurgical & Engineering Association 17th June 2014
Copyright © TWI Ltd 2014
� Drivers for local vacuum
� EB welding with mobile local vacuum
� Practical application
� Laser Welding with mobile local vacuum
� Summary
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Scope
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Why Power Beam Welding?
ProductivityEconomyQuality DistortionResidual StressMetallurgical
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� Since EB welding first used - 1957
� Vacuum chambers
� Asset
� Hindrance
� Non-vacuum developed for automotive
� Mobile sealing attempts
� Laser developments
History
4SMEA June 2014 CSP TWI
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� Ideal welding atmosphere -
prevents oxidation of reactive metals
vacuum re-melted weld metal
� No plasma effects
� Easy to generate
� Low cost: e.g. £20/day
� for 150 m3 (10-3mbar)
� Control
� fume, convection, containment
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Vacuum
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� Size of structures
� Transportation issues
� Site welding
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Why Local Vacuum?
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� High vacuum 10-3 - 10-4 mbar
� Partial vacuum 10-1 - 10-2 mbar
� Non - vacuum 1000 mbar
REDUCED PRESSURE ~ 1mbar
Vacuum considerations
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� 100Pa = 1mbar = 1.33 torr
� 10Pa = 10-1 mbar = 1.33 x 10-1 torr
� 1 Pa = 10-2 mbar = 1.33 x 10-2 torr
� 0.1Pa = 10-3 mbar = 1.33 x 10-3 torr
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Vacuum Pressure units
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Electron Beam 350mbar
350mbar, 200kV, 300mA, Helium12SMEA June 2014 CSP TWI
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Industrial Need
A forged flange from a Chinese supplier, Kinhi
Large diameter
forged flanges:
-Expensive (~€35k)
-Few suppliers
-Long lead times
18SMEA June 2014 CSP TWI