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1.15 Repair methods
Pores
Pores within the weld bead constitute the most frequently
encountered defect. Pore formation reduces with increasing
solidification intervals.
Pores are formed by the inclusion of gas bubbles in the event
of excessively rapid cooling. This is caused by the greater
solubility of hydrogen in liquid aluminium (20 times higher than
in the solid state). Condensation therefore poses a particular
hazard, as moisture causes a layer of hydroxide to form, which
has a high hydrogen content.
Other possible causes of pore formation are:
•
unstable electric arc (due to irregular current, irregular
movement of the wire electrode or incorrect weld settings),
•
incorrect placement of welding torch,
•
insufficient inert gas quantity,
•
air infiltration,
•
nozzles that are too small or obstructed by metal splashes,
•
contaminants in the weld bead area (grease, oil, paint,
dirt).
Penetration notches (Fig. E) are formed in the event of using
excessive weld currents or in the event of incorrect placement
of the welding torch.
Protruding weld beads
Protruding weld beads are formed in the event of using
excessively low weld currents or in the case of excessively
slow weld speeds (Fig. F).
Copyright ©
2010
E
F
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