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(11DEVELOP
THEP.OOL
DIRECTION
f
WORKPIECE
Figure 3
(2) MOVE
TO C.
f_///I///77///////////3
(4)REMOVEROE}
"[he filler rod is usually held at an angle of approximately
15 degrees to the work and slowly fed into the weld puddle.
One of the most commonly usedtechniquesfor feeding filler
rod is shown in figure 3. Another method, used mostoften
in multiple-pass welding of vee pints, is to press the filter
rod into the vee groove in line with the weld and melt it
along with joint edges. Still another method, used fre-
quently in making large welds, isto feed filler metal con-
tinuously into the weld puddle by oscdloting the filler rod
and arc from one side of the weld to the other. The filler
red moves in one direction while the arc moves in the
opposite direction, but the filler rod is at all times in close
proximity to the arc and feeding into the weld puddle.
Joints may be welded by the TJ.G. process include all
standard types, suchas square abutting edge, vee buff, tee
and lap connections. It isseldom necessary"to bevel edges
of materlal ll8-inch or less, although heavier materials are
usually beveled. Whenever joints are beveted, filler ma-
teria( must always be added.
The accompanying table provides a guide to the type of
current recommended for welding some typical materials.
ElectTodesused for the T.hG. (nonconsumable) processmay
be pure tungsten or tungsten alloy. Pure tungsten electrodes
were formerly used exclusively. At this time, however, many
(31Ann _
FILLERMETAL
(5) MOVETORCH
TO LEADINGEI)GE_
o,PUODL
_////S////////////////_;'//////_///////A
_Lf .OO\
@
ADDITIONOF
FILLERMETAL
(VERTICAL _"s°"i
POSITION)
electrodes are alloyed with small percentages of thorium
or zirconium. Suchelectrodes have the advantage of greater
current-carrying capacity For a given diameter, a more
stable arc at low current values, and longer llfe with less
deposit of tungsten in the welds.
TYPES OF GAS TO USE
Eitherargon, helium,or amixture ofthe two can be usedwith
the T.I.G. process. Argon is used most frequently because:
1. It provides general suitability with a wide variety of
metals.
2. It mamtalns a stabilizing influence on the welding arc
3. It costs less (due to the lower flow rates required).
Helium isgenerany usedwhen welding heavy metal sections
because it provides greater weld penetration. Mixtures of
argon and helium are useful when a balance of these char-
acteristicsis desired.
Argon isgenerally supplied in K-cylinders, having a capac.ty
of approximately 238 cubic feet at a pressure of 2200 psi,
or in T-cylinders, having a capacity of approximately 330
cubic feet at a pressureof 2640 psi. Purity of commercial
argon ranges between 99.95% and 99.99%.
CurrentSelectionfor Inert.gas
(nonconsumable)welding
Material
APernse_ Current* Direct Currellt
St_lllz_d St_ght IP_t_ity Reverse POlaritY
I i =
Magnesiumup to _z-m th=ck v" \/
Magnesiumabove % s-m thick _/ \'
MaEneslumcastings %/ _,,
Alummumupto _2-in thick _/ _/
Aluminum over _3a-,n th,ck x/ v
Alurnm_m castmgs \/ V'
Stamless steel V \/
Brass alloys v' x/
_lllCOn copper _ _/
S11ver %/ _,/
Higb-chromium, nickel-base, high
temperature alloys _/ V
Silver cladding _/ x/
Harb facing _/ _,'
Cast iron _/ V'
Low-carbonsteel, 0 015 to 0 030 in t %/
Lowcarbon steel 0 030 to O 125 in "/ _/
High-carbonsteel, O O15 to 0 030 in %/ x/
High-carbonsteel, 0.030 in and up "_/ \/
Deoxidized copper_ %/ \1
\
%/
%/
%,t
"v
%/
\/
%/
• Where alternating currs_t is recommended as a second choif;_J_, US_ about 25% hlsher current than that
reco_lmended for OCSP
DO riot Use elternatln_ current On tightly jigged parts
; Use braZlCg flux Or slllCO_ b_ont_ flu:_ for 1/4 inch anr_thicker
1-20
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