WELDING RESEARCH A B Fig. 4 — Conventional 2D xray radiographs of laser welds made in nickel for the following: A — Vacuum at 10–1 mbar pressure; B — Ar shielding gas. Table 3 — Summary of CT Results for an 11.4mmLong Region of Interest along the Length of the Weld for LowPower (LP) and HighPower 65-W water-cooled reflection target that provides a nominal focal spot size of 3 m (when measured at 70 kV and 0.1 mA) at the x-ray emission point. Xray images were captured by a Perkin Elmer XRD0820 amorphous silicon flat panel detector, which has an input screen 200 × 200 mm in size with 1000 × 1000 detector elements resulting in a native pixel size of 0.2 mm, the detector also has a 16 bit (65536 grey levels) dynamic range. The detector is mounted 929 mm from the focal spot of the projected x-ray images, providing a geometrically magnified image for improved defect detection. The weld coupons were placed on the end and rotated about the centerline 422-s WELDING JOURNAL / NOVEMBER 2016, VOL. 95 of the weld using a turntable within the x-ray cabinet between the x-ray source and detector. The coupon was rotated through 360 deg with images (projections) being captured at regular intervals (angular increments) during the rotation. The ideal number of projections to use equates to × number of pixels across the sample, which cor- (HP) Laser Welds, and Electron Beam Welds Material Weld Qualitative Level CT Voxel Total Number Number of Pores Total Volumetric Porosity per Unit Condition of Porosity Size of Pores Larger than 10–4 mm3 Porosity by CT Volume of Weld (m) (mm3) (%) Ni LaserAr, HP H 16.8 117 88 1.50 2.11 Ni LaserAr, LP H 16.8 190 96 0.354 0.08 Ni EB1Vac H 26.1 123 122 0.248 0.23 Ni EB2Vac H 16.8 627 246 0.207 0.18 Ni LaserVac, HP M 19.7 218 132 0.167 0.11 Ni LaserVac, LP M 19.2 214 132 0.097 0.09 Ti LaserAr, HP M 15.3 58 41 0.089 0.14 Ti LaserAr, LP M 15.3 40 33 0.031 0.10 Ti LaserVac, HP L 15.3 2 1 0.003 0.002 Ti LaserVac, LP L 15.3 1 1 0.003 0.002 Total 1590 891 2.83 N/A Table 4 — Summary of Geometric Shapes and CrossSectional Areas of the Welds Material Weld Weld Weld Weld Keyhole Weld Weld Weld Condition Depth Width D/W Width Area Volume(a) Perimeter (mm) (mm) Ratio (mm) (mm2) (mm3) (mm) Ni LaserAr, HP 3.4 3.8 0.89 1.2 6.2 71.0 12.3 Ni LaserAr ,LP 2.5 3.0 0.83 1.1 3.9 44.7 9.2 Ni EBVac 8.9 3.0 2.97 0.94 9.4 106.7 21.7 Ni EBVac 9.8 3.0 3.27 0.83 10.0 113.9 24.4 Ni LaserVac, HP 9.8 2.8 3.50 1.2 12.9 146.5 23.2 Ni LaserVac, LP 7.5 2.5 3.00 1.1 9.3 105.7 18.7 Ti LaserAr, HP 2.7 3.5 0.77 2.2 5.7 65.5 10.2 Ti LaserAr, LP 1.6 3.1 0.52 1.9 2.88 32.8 8.1 Ti LaserVac, HP 8.7 2.5 3.48 1.6 15.2 173.3 20.9 Ti LaserVac, LP 6.3 2.7 2.33 1.6 12.5 142.5 17.7 (a) The weld volume is given for an 11.4mmlength of weld.
Welding Journal | November 2016
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