RD&D-Programme 2004 - SKB

Tensile test bars have been taken out of two lid welds (L026 and L028). L026 was welded
without oscillation and L028 with oscillation. Different rotation speeds have also been tried.
No significant difference has been found in strength properties related to welding speed or beam
oscillation. The tensile specimens from lid weld L028 (see Figure 6-14 and Table 6-2) exhibited
a slightly higher tensile strength and elongation limit compared with lid weld L026.
The conclusions from the tensile tests are:
• The fracture occurred in the weld metal.
• The strength level of the weld metal is shown in Table 6-2.
• The strength of the weld metal is uniform at welding speeds between 250 and
325 millimetres per minute.
• The strength of the weld metal in the overlap area is roughly the same as that of the
rest of the weld metal.
Programme
Electron beam welding as a method is known for its good repeatability and reliability once
the process parameters have been determined. The welding trials performed confirm the good
repeatability of EBW, despite a lack of precision in the manufacture of different cathodes. In
the planned demonstration phase, the potential of the method as a production method will be
demonstrated on roughly 20 welds. The resulting weld quality will be investigated for further
statistical processing for the purpose of gathering input data for the safety assessment prior to
the application for a permit to build the encapsulation plant. According to plans, the demonstration
phase will be carried out during 2004 and early 2005.
Figure 6-14. Tensile specimen from lid weld L028. Rotational position 310°.
Table 6-2. Tensile specimen from lid weld no L028 welded with an oscillating beam.
Specimen no/ Welding speed Tensile strength Elongation Elongation at rupture
position in lid weld mm/min R m limit R p0.2 A 5
MPa MPa %
S3/12.5° Slope-out zone 250/325 185 70 26
S1A/40° 250 189 65 29
S1B/40° 250 190 64 30
S2A/310° 325 191 67 29
S2B/310° 325 188 66 29
Reference specimen in parent metal near weld area:
L1/40° lid – 203 85 68
L2/310° lid – 205 82 52
74 RD&D-Programme 2004