Consequently the tubes are MIAB welded (parameters as per trial
20 of Table 4) and radiography test is performed on the weld joint
after removal ofthe reinforcement. The resultis shown in Fig. 8. Itis
observed that the number of pores, has reduced to a greater extent
even as compared to the result shown in Fig. 7. This concentration
of pores is within the acceptable limits as per ASME section 5. Thus
the study demonstates that the butt surface of the tubes must be
free fromimpurities to get a better resultfor radiography test. These
small number of pores may arise due to the interaction of the gas
molecules in the weld region during the heating and cooling proces
of welding.
Hence, it is proposed that, by employing shielding gas during
MIAB welding, there is a possiblity to eliminate the pores.
However, in common with other forge welding techniques such
as flash and friction, MIAB weld quality cannot be assessed by the
non-destructive techniques of radiography. This is because itis possible
to have thin layers of oxide or flattened inclusion at the weld
line which are too smallto detect but can give areas of low adhesion
and hence weakened welds.