Page 64 - Welding of Aluminium and its Alloys
P. 64
Preparation for welding 55
Table 4.1 Suggested parameters for plasma-jet cutting
Metal Plasma Gas Shield Gas Current Voltage Cutting Method
thickness gas flow gas flow (amps) (volts) speed
(l/min) (l/min) (mm/min)
1.0 Air 98 4800 Manual
1.5 Air 98 6300 Manual
3 Air 98 3000 Manual
6.5 Air 98 1000 Manual
6.5 N 2 34 CO 2 100 1800 Manual
6.5 Ar + H 2 25 200 50 1500 Manual
10 N 2 35 CO 2 100 200 1250 Manual
12.5 Ar + H 2 28 280 55 1000 Manual
25 Ar + H 2 33 330 70 500 Manual
50 Ar + H 2 45 400 85 500 Manual
6 Ar + H 2 55 300 140 7500 Mechanise
6 N 2 32 CO 2 100 115 1800 Mechanise
10 N 2 32 CO 2 100 120 900 Mechanise
12.5 N 2 32 CO 2 100 120 480 Mechanise
12.5 N 2 32 CO 2 100 300 3200 Mechanise
12.5 Ar + H 2 60 300 140 5000 Mechanise
25 N 2 70 CO 2 100 400 1800 Mechanise
25 Ar + H 2 60 375 160 2300 Mechanise
50 N 2 32 CO 2 100 400 800 Mechanise
50 Ar + H 2 60 375 165 500 Mechanise
75 Ar + H 2 95 420 170 380 Mechanise
75 Ar + H 2 45 N 2 100 400 500 Mechanise
75 Ar + H 2 45 N 2 100 700 650 Mechanise
100 Ar + H 2 95 450 180 750 Mechanise
125 Ar + H 2 95 475 200 250 Mechanise
12.5mm, argon–hydrogen is regarded as the best choice for the plasma gas,
this gas mixture giving the best quality cut, irrespective of thickness. The
secondary cutting gas may be carbon dioxide or nitrogen.Table 4.1 lists the
recommended cutting/shielding gases and typical parameters for plasma
cutting the aluminium alloys.Water injection into the nozzle can be used in
addition to the orifice gas.This restricts the plasma jet further and produces
a better quality, more square, cut, although above 50mm thickness these
advantages are reduced.
A development of the process known as high-tolerance plasma-arc
cutting (HT-PAC), also known as plasma-constricted arc, fine plasma or
high-definition plasma, has been developed and is being used as a cheaper
alternative to laser cutting of material less than 12mm in thickness. This
variation to the plasma-arc process achieves a better quality cut with
more perpendicular faces, a narrower kerf and a less rough finish than the
