Advanced Welding Processes: Technologies and Process Control

25
23
21
19
17
15
13
11
9
7
20
18
16
14
12
10
6
7
8
6
4
2
6 and above
Below 6
0 0
Stability
CO 2
Gases for advanced welding processes 67
Ar + O 2
10
9
8
1
The high-helium mixtures are used predominantly for dip transfer, where
the higher helium level increases welding speeds, improves bead appearance
and increases the dip transfer frequency. The arc voltage is increased and
fusion is improved especially at low currents.
Lower-helium mixtures have been developed mainly for spray and pulsed
transfer welding. They promote smooth spray transfer, good fusion and excellent
bead profiles. The addition of 1–2% hydrogen to these mixtures improves
wetting and bead appearance by chemically reducing the surface oxide.
Although these mixtures were specifically developed for austenitic stainless
steel they can be used for plain carbon steel, where increased speed and
improved surface appearance are required (e.g. in automated welding of thin
sheet steel components).
Gases for GTA welding of steels
Argon is the most widely used gas for GTAW although mixtures of argon
with up to 5% hydrogen are often used, particularly for austenitic stainless
steels where increased speed, improved profile and improved process tolerance
2
25
23
21
19
17
15
13
11
9
7
18
1614
3
Stability
4
5
CO 2
6
Ar + O 2
25
23
21
19
17
15
13
11
9
7
10
9
8
7
5.6 Arc stability, dip transfer GMAW in argon/CO 2/O 2 mixtures.
(Stability is measured as the standard deviation of arc time, i.e. low
values of the standard deviation indicate good stability.)
Stability