Operation Manual

19
A7 TIG Orbital System 300© Kemppi Oy 2016 1615
OPERATING MANUAL
Wire feed can be continuous, or you can select Step Mode.
In Step Mode, two levels of wire feed are synchronized
with pulsed current. Wire feed during the low current
pulse period is set as a percentage (0–99 %) of the high
pulse wire feed speed. This feature is useful to control
weld puddle size and to maximize ll rate. It may not be
possible to use the same wire feed speed for both high
and low current pulse periods, but the amount of wire fed
during low pulse can be tailored to optimize solidication
rate and puddle control.
3.1.4 Root-pass procedure
Filler wire to tungsten electrode gap should be
approximately 1.5 mm (rule of thumb is 2/3 the diameter
of the electrode). When welding a "J" prep, the wire entry
into the weld puddle is correct when it appears that the
wire is standing still. Wire should feed smoothly into the
front edge of the weld puddle. There should be no drip or
drag of the wire. When welding a 37.5 degree bevel, the
wire should push slightly into the work.
To make the wire enter the weld puddle directly under the
tungsten electrode:
1. Adjust arc length so that wire entry is correct. As
the weld puddle partially solidies during low
current, the edge of the puddle freezes, forming a
circular "chill mark".
2. Observe the chill marks on the weld bead surface.
If the chill marks are closer than 0.8 * root land
thickness, increase travel speed by 3 mm/min until
you have reached the needed reinforcement.
• If the ID bead is almost solidied between current
pulses, increase high-pulse heat input by doing
one or more of the following:
• Increase high pulse current.
• Increase high pulse time (0.2 s minimum).
• Decrease wire speed.
• Decrease travel speed.
• If the ID bead is too uid, reduce low pulse heat
input by doing one or more of the following:
• Reduce low pulse current (reduce % of high
pulse).
• Increase low pulse time.
• Increase wire speed.
• If there is insucient penetration on the I.D,
observe the chill marks on the weld surface.
• If chill mark spacing is adequate, check that low
pulse weld current is at least 50 % of the high
pulse level and increase high-pulse weld current
if necessary.
• Record all changes.
3.1.5 Hot-pass procedure
1. Set wire to tungsten electrode distance and ensure
that the wire is aimed laterally directly under the
electrode.
2. Ensure that the hot pass is not causing the root
bead to melt again as this may result in "suckback"
or concavity of a previously acceptable root bead.
3. If the root pass melts, reduce weld current.
4. Ensure that the weld puddle is fusing into both
sidewalls.
5. Check centering and increase oscillation width if
necessary.
6. If the puddle runs ahead of the tungsten electrode
on the downhill side, reduce wire speed.
7. If the puddle is sticking or making "wagon tracks"
on the sidewalls, reduce travel speed.
When using the pulsillation technique, the lower amperage
during torch excursion across the seam reduces the size of
the weld puddle. The weld puddle must be large enough
to ensure that the ller wire melts properly and does not
"drag" on the unmelted solid surface of the joint. Set low-
pulse amperage to approximately 70 % of high pulse.