MetFab - Air Products Welder's Handbook - Flipbook - Page 33
Defects in welds
Porosity
Porosity may be caused by:
• inadequate/incorrect weld process gas
• contamination of the weld preparation
or consumables
• welding onto material which
reacts or which contains dissolved gases
• incorrect welding parameters
Prevention methods:
• ensure satisfactory cleanliness of the
workpiece. Remove contaminates such
as grease, oil, moisture, rust, paint and
dirt before welding
To avoid porosity, always select weld
parameters that generate sufficient weld
pool size and fluidity to ensure gases are not
entrapped. This is particularly important
when welding:
• Double-sided fillet welds
• Butt welds with depth to width ratios
greater than 1
• eliminate contamination of the welding
consumables
• ensure the correct selection and flowrate
of your weld process gas
• eliminate draughts
• purchase materials from
reputable suppliers
• use filler wire with sufficient
deoxidents when welding steels
• ensure weld process gas delivery
system is contamination and leak free
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