MetFab - Air Products Welder's Handbook - Flipbook - Page 18
Choice of current
Both direct current (DC) and
alternating current (AC) are
commonly used when TIG welding.
Crater filling
Automatic gradual reduction of the
current at the end of a weld run avoids the
formation of a crater.
Crater or
hole and
solidification
crack at the
end and center
of the weld
Direct current with the electrode
connected to the negative terminal
(DCEN) of the power source is used for:
• Carbon steels
• Copper and its alloys
• Stainless steels
• Nickel and its alloys
Arc extinguished
• Titanium and its alloys
• Zirconium and its alloys
Welding
current
Alternating current is used for
welding:
Weld surface
smooth at end
of weld run
• Aluminium and its alloys
• Magnesium and its alloys
• Aluminium bronze
Power sources are available to deliver
pulsed DC or combining AC and DC.
Current slowdown
Top Tip
Only use stainless steel wire brushes
and scrapers to clean aluminium
before welding. Do not use these to
clean other materials.
14
Welding
current
