Electron beam welding of steam turbine diaphragms

Electron beam welding can produce deep narrow welds in a single pass in depths of 150mm or more in a wide range of steels and other materials. Welding speeds are typically 100mm per minute and dissimilar combinations (e.g. 12Cr to 0.5CrMoVn steel) can be readily joined. There are not usually any consumables - closely butting faces are fused together by the beam.

Transverse section from reduced pressure EB weld in 150mm thick c-mn steel

EBW has the following advantages applied to these products:

• Low heat input - low distortion welding
• Dissimilar combinations possible
• Very thick section welding (>150mm) in a single pass
• Thin band welding possible
• High integrity welding
• Fast
• Well proven technology in aero-engine and power gas turbine manufacture

Either high vacuum electron beam welding or Reduced Pressure electron beam welding can be applied to this type of component. Both processes produce similar fusion zone and weld properties. The Reduced Pressure EBW technique offers the following additional advantages:

• Rapid pump down times - operates ~1mbar
• Part cleanliness (away from joint area) not important
• Much improved immunity to flashover interruptions

For further information, please contact: power@twi.co.uk

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