Electron beam processing information
Welding - joint design
As a result of the high power density the beam is able to melt material to a depth of several centimetres and allow it to flow together to make a weld. Thus the machining of V or K type preparations and addition filler materials are not required.
To enable high quality welds to be made certain attention must be paid to the joint design and cleaning procedures when EB welding.
Surface cleaning
Surface cleaning must be carried out as with many other fusion welding techniques. Attention should be paid to removal of cutting fluids, oils, and grinding residues. Solvent degreasing followed by drying in clean warm air is preferred. If the parts are to be stored for a short period the faces can be covered with Al foil.
Below are a few joint designs with each with its own advantages and disadvantages when used in EB welding.
| Simplest square edged butt joint preparation for either tubes or plates | Square edged butt joint with added backing bar |
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| Square edged butt joint with excess material for post weld machining | Butt joint with a 'consumable'. Joint preparation for joining thick to thin sections |
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These are only a few simple joint designs amongst the many available, and each one will usually be tailored to the individual needs and specifications of the components to be welded.
When welding different material combinations, weld metal compositions can be tailored by adding metal inlays into the joint.
Demagnetisation
As the beam is made up of charge carriers it can be influenced by stray or residual magnetic fields. It is very important to reduce the residual magnetic field in components to be welded to a level that can be tolerated (typically less than 5 Gauss when measured externally with a Hall effect probe).
| Joint preparation for joining very thin sections to thick sections | In this section poor fit-up may give problems with porosity and/or weld bead concavity |
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More detailed information is available to TWI's Industrial Members:
EB and other techniques fusion reactor fabrication
Contact: electronbeam@twi.co.uk
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