Lincoln Electric INVERTEC SVM161-A Service Manual page 26

B-10
STEEL TIG WELDING
The TIG process is very effective for welding both car-
bon steel and alloy steel, especially in applications
requiring precision results. DC Electrode Negative
Polarity is required. Since this process does not
include the removal of impurities, proper cleaning and
preparation of the edges is required.
FILLER MATERIAL:
The filler rods must deposit welds with mechanical
characteristics appropriate for the application.
COPPER TIG WELDING
Since the TIG welding is a process characterized by
high heat concentration, it is particularly suitable for
welding materials with high thermal conductivity, like
copper. As with steel, the DC Electrode Negative
Polarity is employed, with argon as protective gas.
Considering the fluidity of molten copper, the use of
backup support may prove useful.
FILLER MATERIAL:
In order to avoid the oxidation of the molten material,
filler materials containing phosphorus, silicon or other
deoxidating materials are typically used. The mechan-
ical properties can also be improved through the use of
silver.
TIPS FOR AC TIG WELDING
AC Inverter TIG power sources offer two significant
advantages over conventional Silicon Controlled
Rectifier (SCR) / transformer power sources:
Electrode Polarity
Electrode Tip Preparation
Electrode Type
EWTh-2, EWLa-1
Electrode Size-in. (mm)
.010 (0.25)
.020 (0.50)
.040 (1.0)
1/16 (1.6)
3/32 (2.4)
1/8 (3.2)
Tungsten electrodes are classified as follows by the American Welding Society (AWS):
+2% Thoria .......................EWTh-2 ...red
+1.5% Lanthana ...............EWLa-1 ...black
OPERATION
GTAW Process
DC-
Sharpened
Up to 15 A.
Up to 15 A.
Up to 80 A.
Up to 150 A.
Up to MAX. A.
X
INVERTEC® V205-T AC/DC™
1. The AC wave balance can be set to a higher per-
centage electrode negative which minimizes tung-
sten heating and erosion.
2. The AC frequency can be varied to "focus" the arc.
Increasing the AC frequency above 60Hz will narrow
the cone shape arc from the tungsten's tip.
Decreasing the AC frequency below 60Hz will
broaden the cone shape arc from the tungsten's tip.
The two above benefits can be used to maintain a tight
focus of the arc for precise heat control and tight joint
access. Because of the AC inverters abilities in these
areas the following recommendations are made as a
starting point:
• A 2% Thoriated tungsten is recommended instead of
the Pure tungsten that is normally recommended for
AC welding. Thoriated tungstens emit electrons eas-
ier and therefore will improve starting.
• Sharpen the tungsten to a point. Normally it is rec-
ommended to pre-ball a pure tungsten when AC
welding with a conventional power source.
However, the AC inverter with it's extended AC bal-
ance control minimized tungsten heating thus allow-
ing for a pointed tungsten to be used.
• Set the AC Balance control to maximum 85% elec-
trode negative. This can be reduced if the material
welded is heavily oxidized, however starting at max-
imum and adjusting to less is desired.
• Set the AC Frequency in the 100 to 120 Hz range.
This is a "Sweet Spot" for most aluminum applica-
tions.
AC
Sharpened
EWTh-2, EWLa-1
Up to 15 A.
Up to 20 A.
Up to 60 A.
Up to 130 A.
Up to MAX. A.
X
B-10
Approximate Argon
Gas Flow Rate
C.F.H. (l/min.)
Stainless
Aluminum Steel
3-8 (2-4) 3-8 (2-4)
5-10 (3-5) 5-10 (3-5)
5-10 (3-5) 5-10 (3-5)
5-10 (3-5) 9-13 (4-6)
13-17 (6-8) 11-15 (5-7)
15-23 (7-11) 11-15 (5-7)