Thermal Arc Fabricator 140, Руководство по обслуживанию, Страница: 43 / 84

OPERATION FABRICATOR 140, 180
Janua r y 25, 2008 4-7 Manual 0-4992
4.08 MIG Welding (GMAW) Variables
Most of the welding done by all p r ocesses is on ca r bon
steel. The following items desc r ibe the welding va r iables
in sho r t-a r c welding of 24 gauge (0.024”, 0.6mm) to ¼”
(6.4mm) mild sheet o r plate. The applied techniques and
end r esults in the GMAW p r ocess a r e cont r olled by these
va r iables.
Pre-selected Variables
P r e-selected va r iables depend upon the type of mate r ial
being welded, the thickness of the mate r ial, the welding
position, the deposition r ate and the mechanical
p r ope r ties. These va r iables a r e:
1. Type of elect r ode wi r e
2. Size of elect r ode wi r e
3. Type of gas (not applicable to self-shielding wi r es
FCAW)
4. Gas flow r ate (not applicable to self-shielding wi r es
FCAW)
Primary Adjustable Variables
These cont r ol the p r ocess afte r P r e-selected Va r iables
have been found. They cont r ol the penet r ation, bead width,
bead height, a r c stability, deposition r ate and weld
soundness. They a r e:
1. A r c Voltage
2. Welding Cu rr ent (wi r e feed speed)
3. T r avel Speed
Secondary Adjustable Variables
These va r iables cause changes in p r ima r y adjustable
va r iables which in tu r n cause the desi r ed change in the
bead fo r mation. They a r e:
1. Stickout—distance between the end of the
contact tube (tip) and the end of the elect r ode
wi r e. Keep this at about 3/8” (10mm) stickout
(as shown in Figu r e 4-8).
Ga s Nozzle
Tip to Work
Di
s ta n ce
Co n tact Tip (T u be)
Electrode Wire
Act u al S ticko u t
Average Arc Le n gth
Art: A-05109
Figu r e 4-8: Elect r ode Stick-Out
2. Wi r e Feed Speed. Inc r ease in wi r e feed speed
inc r eases weld cu rr ent. Dec r ease in wi r e feed speed
dec r eases weld cu rr ent.
3. Nozzle Angle. (Figu r es 4-9 and 4-10) This r efe r s to
the position of the welding gun in r elation to the
joint. The t r ansve r se angle is usually one half the
included angle between plates fo r ming the joint. The
longitudinal angle is the angle between the cente r
line of the welding gun and a line pe r pendicula r to
the axis of the weld. The longitudinal angle is
gene
r ally called the Nozzle Angle and can be eithe r
t r ailing (pulling) o r leading (pushing). Whethe r the
ope r ato r is left-handed o r r ight-handed has to be
conside r ed to r ealize the effects of each angle in
r elation to the di r ection of t r avel.
Lo n git u di n al
A n gle
Tra ns ver s e
A n gle
Axi s of Weld
Art: A-05110
Figu r e 4-9: T r ansve r se and Longitudinal Nozzle Axes
Directio n of G un Travel
90º
Leadi n g or "P us hi n g"
A n gle (Foreha n d)
Traili n g or "P u lli n g"
A n gle (Backha n d)
Art # A-05111
Figu r e 4-10: Nozzle Angle, Right-Handed Ope r ato r