Welding Current - Telwin MIG-MAG Manual De Instrucciones

6.2.2

Welding current

Is determined for a given wire diameter by its own advancement speed. current can be
adjusted by regulation potentiometer (on wire feeder). Remember that for a given
current the wire advancement speed is inversely proportional to the diameter used.
Approximate values for the current in manual welding mode for the most commonly
used wires are given in the table (TAB. 4).
6.2.3 Arc voltage
Can be adjusted at short intervals (steps) by switches on the power source. Voltage
must comply with the chosen speed of wire advancement (current), and with the wire
diameter and shielding gas used. This may be set out in the following equation giving
the medium value:
U = (14 + 0,05 x l )
2 2
where :U = arc voltage in volts;
2
l = welding current in amperes.
2
Remember that in comparison with the no-load voltage supplied for each step, the arc
voltage will be less 2-4V for every 100A delivered. The argon/CO mixtures require arc
voltage of 1-2V less than that required with CO .
TAB. 4 INDICATIVE VALUES FOR WELDING CURRENT (A)
WIRE DIAMETER (mm)
0,6
Carbon and mild
steels
30 ÷ 90
SHORT ARC
SPRAY ARC
Stainless steel
SHORT ARC
SPRAY ARC
Aluminium and alloys
SHORT ARC
SPRAY ARC
FIG. I
A)
HORIZONTAL
WELDING
5 - 15°
2
2
0,8 1
40 ÷ 170 50 ÷ 190
/ 160 ÷ 220 180 ÷ 260
/ 40 ÷ 140 60 ÷ 160
/ / 140 ÷ 230
/ 50 ÷ 75 90 ÷ 115
/ 80 ÷ 150 120 ÷ 210
FRONTAL HORIZONTAL
WELDING
90°
6.2.4 Weld quality
The quality of the weld seam is higher when less spatter is produced. this is determined
principally by a correct balance of the welding parameters: current (wire speed), wire
diameter, arc voltage etc., as well as a correct choice of choke intakes.
In the same way the torch position must comply with the data in figure (FIG. I) in order to
avoid excessive spatter and faults on the weld seam. The weld speed (i.e. the
advancement speed along the joint) is also a determining factor for the correct
execution of the seam. This is particularly important for good penetration and correct
shape of the seam.
The most common welding flaws are summarized in TAB.5.
1,2 1,6
70 ÷ 200 100 ÷ 210
130 ÷ 350 200 ÷ 450
110 ÷ 180 /
180 ÷ 280 230 ÷ 390
110 ÷ 130 130 ÷ 170
125 ÷ 250 160 ÷ 350
B)
5 - 15°
a
x
a
- 26 -
WELDING FLAWS
TAB. 5
FAULT MAIN CAUSE
Porosity - Insufficient protection or poor gas
quality.
- Piece not clean enough.
- Incorrect adjustments.
- Poor operating technique .
Incomplete
- Current too low.
melt
- Welding rate too high.
- Current too low.
Incomplete
- Welding rate too high.
penetration
- Distance of edges of join
insufficient.
- Current too high.
Excessive
- Welding rate too low.
penetration
- Excessive distance of edges of join.
- Current too high.
Incision on
- Poor operating technique.
edges
- Incorrect choice of wire with respect
Broken
to base material.
weld
- INAPPROPRIATE heat transfer
seam
(scant or excessive).
- Unweldable or dirty base material.
C)
VERTICAL
WELDING
TORCH MOVEMENT
DOWNWARDS
UPWARDS
WELDING DIRECTION