Issue Date: March 2006
Air Carbon-ArcGuide
Version: 1 Form No. 89-250-008
March 2006
Air Carbon-Arc Guide
�
WE APPRECIATE YOUR BUSINESS!
Congratulat�ons on your new Arca�r® product. We are proud to have you as our customer and w�ll str�ve to prov�de you w�th the best serv�ce and rel�ab�l�ty �n the �ndustry. Th�s product �s backed by our extens�ve warranty and world-w�de serv�ce network. To locate your nearest d�str�butor or serv�ce agency call 800-231-9353, or v�s�t us on the web at www.thermadyne.com.
Th�s Operat�ng Manual has been des�gned to �nstruct you on the correct use and operat�on of your Arca�r® product. Your sat�sfact�on w�th th�s product and �ts safe operat�on �s our ult�mate concern. Therefore please take the t�me to read the ent�re manual, espec�ally the Safety Precaut�ons. They w�ll help you to avo�d potent�al hazards that may ex�st when work�ng w�th th�s product.
YOU ARE IN GOOD COMPANY!
The Brand of Choice for Contractors and Fabricators Worldwide. Arca�r® �s a Global Brand of Arc Weld�ng Products for Thermadyne Industr�es Inc. We manufacture and supply to major weld�ng �ndustry sectors worldw�de �nclud�ng; Manufactur�ng, Construct�on, M�n�ng, Automot�ve, Aerospace, Eng�neer�ng, Rural and DIY/Hobby�st.
We d�st�ngu�sh ourselves from our compet�t�on through market-lead�ng, dependable products that have stood the test of t�me. We pr�de ourselves on techn�cal �nnovat�on, compet�t�ve pr�ces, excellent del�very, super�or customer serv�ce and techn�cal support, together w�th excellence �n sales and market�ng expert�se.
Above all, we are comm�tted to develop technolog�cally advanced products to ach�eve a safer work�ng env�ronment w�th�n the weld�ng �ndustry.
Air Carbon-Arc Guide
�� March 2006
!!
WARNINGS
Read and understand th�s ent�re Gu�de and your employer’s safety pract�ces before �nstall�ng, operat�ng, or serv�c�ng the equ�pment. Wh�le the �nformat�on conta�ned �n th�s Gu�de represents the Manufacturer’s best judgement, the Manufacturer assumes no l�ab�l�ty for �ts use.
A�r Carbon-Arc Gu�de Form Number 89-250-008:
Publ�shed by:Thermadyne Industr�es, Inc.2800 A�rport RoadDenton, Texas 76207(800) 231-9353www.thermadyne.com
Copyr�ght © 2006 by Thermadyne Industr�es, Inc.® All r�ghts reserved.
Reproduct�on of th�s work, �n whole or �n part, w�thout wr�tten perm�ss�on of the publ�sher �s proh�b�ted.
The publ�sher does not assume and hereby d�scla�ms any l�ab�l�ty to any party for any loss or damage caused by any error or om�ss�on �n th�s manual, whether such error results from negl�gence, acc�dent, or any other cause.
Publ�cat�on Date: March 1, 2006
Record the following information for warranty purposes:
Where Purchased: ___________________________________
Purchase Date: ___________________________________
Equ�pment Ser�al #: ___________________________________
March 2006
Air Carbon-Arc Guide
���
TABLE OF CONTENTS
Page #
1. Introduction 1
2. Safety and Health 4
3. Principles of Operation 10
4. Operating Techniques 19
5. Equipment Selection 30
6. Important Process Variables 37
7. Advantages and Limitations 46
8. Troubleshooting 48
Air Carbon-Arc Guide
�v March 2006
Sugg
este
d Cu
rren
t Ran
ges
For C
omm
only
Use
d El
ectro
de T
ypes
and
Siz
es
Elec
trode
Di
amet
erDC
Ele
ctro
de W
ithDC
EPAC
Ele
ctro
de W
ithAC
AC E
lect
rode
With
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in.
mm
.M
inim
umAm
psM
axim
umAm
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umAm
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axim
umAm
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umAm
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83.
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324.
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150
3/16
4.8
200
250
200
250
150
180
1/4
6.4
300
400
300
400
200
250
5/16
7.9
350
450
3/8
9.5
450
600
350
450
300
400
1/2
12.7
800
1000
5/8
15.9
1000
1250
3/4
19.1
1250
1600
125
.416
0022
00
March 2006
Air Carbon-Arc Guide
v
!!
WARNINGS
Fumes from the a�r carbon-arc process are of var�ous types and strengths, depend�ng on the k�nd of base metal be�ng worked on. To ensure your safety, do not breathe these fumes. Vent�late near the arc to protect a�r carbon-arc operators and others �n the area. Somet�mes, operators may need to use spec�al breath�ng equ�pment. Be sure to test the a�r to ensure �t �s free of dangerous fumes.
SECTION 1: INTRODUCTION
Process Description
The a�r carbon-arc process (CAC-A) removes metal phys�cally not chem�cally (as �n oxy-fuel cutt�ng - OFC). Goug�ng or cutt�ng occurs when the �ntense heat of the arc between the carbon electrode and the workp�ece melts part of the workp�ece. Meanwh�le, a�r passes through the arc qu�ckly enough to blow the molten mater�al away.
S�nce the a�r carbon-arc process doesn’t need ox�dat�on to ma�nta�n the cut, �t can gouge or cut metals that the OFC process can’t. Most common metals - carbon steel, sta�nless steel, many copper alloys and cast �rons - can be cut us�ng the a�r carbon-arc process. The metal removal rate depends on the melt�ng rate and the a�r jet’s effic�ency �n remov�ng molten metal. The a�r must l�ft the molten metal clear of the arc before the metal sol�d�fies.
History
A�r carbon-arc goug�ng began �n the 1940’s, grow�ng out of an ex�st�ng process, carbon-arc cutt�ng. Need�ng to remove several hundred feet of flat, cracked, sta�nless steel weld, Myron Stepath, a weld�ng eng�neer, developed a�r carbon-arc goug�ng.
Air Carbon-Arc Guide
1-2 March 2006
Before, carbon-arc cutt�ng had been used to remove overhead and vert�cal defect�ve welds and r�vet heads. The carbon-arc melted the metal, and grav�ty moved away the molten metal.
Then Stepath reasoned that an a�r jet could prov�de the force to remove metal ly�ng flat. A d�rect current electrode negat�ve carbon-arc was tr�ed, and an a�r blast was prov�ded by a second operator, d�rect�ng an a�r nozzle at the molten pool.
Th�s attempt was unsuccessful because the arc was not as stable as a carbon-weld�ng arc. Next, Stepath tr�ed d�rect current electrode pos�t�ve. The result was a�r carbon-arc goug�ng. The bas�c pr�nc�ple rema�ns the same today, but the equ�pment has been �mproved and the number of appl�cat�ons expanded.
In 1948, Myron Stepath �ntroduced the first a�r carbon-arc torch to the weld�ng �ndustry. In 1949, Stepath and two assoc�ates founded the Arca�r® Company.
No longer were two operators needed. The compressed a�r came through the torch and out beneath the electrode. Th�s new tool saved t�me on weld backgoug�ng, crack removal, and repa�r of other weld defects on carbon, alloy and sta�nless steel. Prev�ously, such work had been done by gr�nd�ng or ch�pp�ng. As the process became more popular, torches were des�gned for more effic�ent, cleaner metal removal and for greater operator comfort.
March 2006
Air Carbon-Arc Guide
1-3
Applications
Industry has enthus�ast�cally adopted a�r carbon-arc goug�ng and has found many uses for the process: �n metal fabr�cat�on and cast�ng fin�sh�ng, �n chem�cal and petroleum technology, �n construct�on, m�n�ng, general repa�r and ma�ntenance.
Arca�r® Torches and Electrodes are used throughout the world, anywhere metal �s gouged, grooved, severed, or removed from a surface.
The a�r carbon-arc process �s flex�ble, effic�ent, and cost effect�ve on pract�cally any metal: carbon steel, sta�nless steel and other ferrous alloys; gray, malleable and duct�le �ron; alum�num; n�ckel; copper alloys and other nonferrous metals.
Air Carbon-Arc Guide
2-4 March 2006
Section 2: SAFETY AND HEALTH
Introduction
Safe pract�ces �n weld�ng and cutt�ng processes, such as a�r carbon-arc, �s covered �n ANSl Z49.1, “Safety in Welding and Cutting”, and ANSl 249.2, “Fire Prevention in Use of Welding and Cutting Processes.” A�r carbon-arc operators and the�r superv�sors should adhere to the safe pract�ces d�scussed �n these documents.
Other hazards �n arc weld�ng and cutt�ng are br�efly d�scussed �n th�s sect�on.
Properly Install, Use, and Maintain Equipment
Ser�ous �njury or death may result �f goug�ng and cutt�ng equ�pment �s not properly �nstalled, used and ma�nta�ned. M�suse of th�s equ�pment and other unsafe pract�ces can be hazardous. The operator, superv�sor and helper must read and understand the follow�ng safety warn�ngs and �nstruct�ons before �nstall�ng or us�ng any a�r carbon-arc torch or equ�pment.
The goug�ng cutt�ng process �s used �n many potent�ally dangerous env�ronments such as elevated he�ghts, areas of l�m�ted vent�lat�on, close quarters, around water, �n host�le env�ronments, etc., and �t �s �mportant that the operators are aware of the dangers assoc�ated �n work�ng �n these types
March 2006
Air Carbon-Arc Guide
2-5
of cond�t�ons. Be certa�n that the operator(s) are tra�ned �n safe pract�ces for env�ronments �n wh�ch they are expected to work and under competent superv�s�on.
It �s essent�al that the operator, superv�sor and others �n the work area are aware of the dangers of the a�r carbon-arc process. Tra�n�ng and proper superv�s�on are �mportant for a safe work place. Keep these �nstruct�ons for future use. Add�t�onal recommended safety and operat�ng �nformat�on �s referenced �n each sect�on.
WARNING !!
ELECTRIC SHOCK CAN CAUSE INJURY OR DEATH
Install and ma�nta�n equ�pment �n accordance w�th the Nat�onal Electr�cal Code NFPA 70 and local codes. Do not serv�ce or repa�r equ�pment w�th power on. Do not operate equ�pment w�th protect�ve �nsulators or covers removed.Serv�ce or repa�r to equ�pment must be done by qual�fied and/or tra�ned personnel only.
ElectrodesKeep carbon electrodes dry. If yours are damp, bake them for 10 hours at 300oF (176oC). Wet electrodes may shatter.
Air Carbon-Arc Guide
2-6 March 2006
Do not contact electr�cally l�ve parts. Do not touch electrode w�th bare sk�n and electr�cal ground at the same t�me. Always wear dry weld�ng gloves �n good cond�t�on. Alum�n�zed protect�ve cloth�ng can become part of the electr�cal path. Keep oxygen cyl�nders, cha�ns, w�re ropes, cranes, ho�sts. and elevators away from any part of the electr�cal c�rcu�t. All ground connect�ons must be checked per�od�cally to determ�ne that they are mechan�cally strong and electr�cally adequate for the requ�red current.
When engaged �n alternat�ng current goug�ng/cutt�ng under wet cond�t�ons or warm surround�ngs where persp�rat�on �s a factor, the use of rel�able automat�c controls for reduc�ng no load voltage �s recommended to reduce shock hazard. When the goug�ng/cutt�ng process requ�res values of open c�rcu�t voltages �n alternat�ng current mach�nes h�gher than 80 volts, and d�rect current mach�nes h�gher than 100 volts, means must be prov�ded to prevent the operator from mak�ng acc�dental contact w�th the h�gh voltage by adequate �nsulat�on or other means.
When goug�ng �s to be suspended for any substant�al per�od of t�me, such as dur�ng lunch or overn�ght, all electrodes should be removed from the torch and the torch carefully located so that acc�dental contact cannot occur. The torch must be d�sconnected from the power source when not �n use. Never �mmerse a�r carbon-arc torches or electrodes �n water.
March 2006
Air Carbon-Arc Guide
2-7
WARNING !!
SMOKE, FUMES AND GASES CAN BE DANGEROUS TO YOUR HEALTH
Ventilation Hazards
Keep smoke, fumes and gases from the breath�ng area. Fumes from the goug�ng process are of var�ous types and strengths, depend�ng on the k�nd of base metal be�ng worked on. To ensure your safety, do not breathe these fumes. Vent�lat�on must be adequate to remove smoke, fumes and gases dur�ng the operat�on to protect goug�ng operators and others �n the area.
Vapors of chlor�nated solvents can form the tox�c gas “Phosgene” when exposed to ultrav�olet rad�at�on from an electr�c arc. All solvents, degreasers and potent�al sources of these vapors must be removed from the operat�ng area.
Fumes produced by cutt�ng part�cularly �n confined places can cause d�scomfort and phys�cal harm �f �nhaled over an extended per�od of t�me. Prov�de adequate vent�lat�on �n the goug�ng/cutt�ng area. Use a�r-suppl�ed resp�rators �f vent�lat�on �s not adequate to remove all fumes and gases.
Air Carbon-Arc Guide
2-8 March 2006
Never vent�late w�th oxygen, because oxygen supports and v�gorously accelerates fire.
WARNING !!
NOISE CAN DAMAGE HEARING
Personal Protective Equipment and Clothing
No�se from the a�r carbon-arc process can damage your hear�ng. Wear protect�ve hear�ng dev�ces to ensure protect�on when no�se levels exceed OSHA standards. Adequate hear�ng protect�on dev�ces must be worn by operators and surround�ng personnel to ensure personal protect�on aga�nst no�se.
March 2006
Air Carbon-Arc Guide
2-9
PERMISSIBLE NOISE EXPOSUREDurat�on Per Sound LevelDay (�n hours) DBA
Slow Response8 906 924 953 972 1001-1/2 1021 1051/4 or less 115
WARNING !!
ARC RAYS, HOT SLAG AND SPARKS CAN INJURE EYES AND BURN SKIN
The goug�ng/cutt�ng processes produce extreme local�zed heat and strong ultrav�olet rays. Never attempt to gouge/cut w�thout a weld�ng helmet w�th the proper lens, that compl�es w�th federal gu�del�nes. A number 12 to 14 shade filter lens prov�des the best protect�on aga�nst arc rad�at�on. When �n a confined area, prevent the reflected arc rays from enter�ng
Air Carbon-Arc Guide
2-10 March 2006
around the helmet. Make sure others are protected from arc rays and sparks. Approved sh�eld�ng curta�ns and appropr�ate goggles should be used to prov�de protect�on to others �n the surround�ng area and operators of nearby equ�pment.
Sk�n should also be protected from arc rays, heat and molten metal. Always wear protect�ve gloves and cloth�ng wh�ch w�ll not allow sk�n to become exposed. All pockets should be closed and cuffs sewn shut. Leather aprons, sleeves, legg�ngs, etc. should be worn for out-of-pos�t�on goug�ng/cutt�ng or for heavy metal-removal operat�ons us�ng large electrodes. H�gh top work shoes prov�de adequate protect�on from foot burns. For added protect�on use leather spats. Flammable ha�r preparat�ons should not be used when goug�ng/cutt�ng. Wear ear plugs to protect ears from sparks.
Shielding Booths
Where the work perm�ts, the arc welder should be enclosed �n an �nd�v�dual booth pa�nted w�th a fin�sh of low reflect�v�ty such as z�nc ox�de, an �mportant factor for absorb�ng ultrav�olet rad�at�ons, and lamp black, or shall be enclosed w�th noncombust�ble screens s�m�larly pa�nted.
March 2006
Air Carbon-Arc Guide
2-11
WARNING !!
WELDING SPARKS CAN CAUSE FIRES AND EXPLOSIONS
Fire and Burn Hazards
Causes of fire and explos�on are; combust�bles reached by the arc, flame, fly�ng sparks, hot slag or heated mater�als. Remove combust�bles from the work area and/or prov�de a fire watch. Avo�d o�ly or greasy cloth�ng as a spark may �gn�te them. Have a fire ext�ngu�sher nearby, and know how to use �t.
Be alert to the danger of conduct�on or rad�at�on, for example �f goug�ng/cutt�ng �s to be done on a metal wall, part�t�on, ce�l�ng or roof, precaut�ons must be taken to prevent �gn�t�on of combust�bles on the other s�de. Do not gouge/cut conta�ners that have held combust�bles. All hollow spaces, cav�t�es and conta�ners should be vented pr�or to goug�ng/cutt�ng to perm�t the escape of a�r or gases. Purg�ng w�th �nert gas �s recommended.
Never use oxygen In an air carbon-arc torch.
Air Carbon-Arc Guide
2-12 March 2006
Tabl
e 1
- Rec
omm
ende
d M
inim
um A
ir Re
quire
men
tsRe
com
men
ded
Com
pres
sor R
atin
g
Air
Pres
sure
(1
)
Air
Cons
umpt
ion
Inte
rmitt
ent U
seCo
ntin
uous
Use
ASM
ERe
ceiv
erSi
zeTy
pe o
f Tor
chps
iKp
acf
mL/
min
.hp
kWhp
kWga
llit
.
L�gh
t Dut
y (2
)40
280
822
7.5
0.4
1.5
1.1
6022
7Ge
nera
l Dut
y (2
)80
550
2570
85
3.7
7.5
5.6
8030
3M
ult�p
urpo
se (3
)80
550
3393
47.
55.
610
7.5
8030
3Au
tom
at�c
(4)
6041
446
1303
1511
.280
303
1. P
ress
ure
wh�
le to
rch
�s �n
ope
rat�o
n2.
Acc
omm
odat
es fl
at e
lect
rode
s3.
Gen
eral
ly c
ons�
dere
d a
foun
dry
touc
h4.
Req
u�re
s so
me
k�nd
of m
echa
n�ca
l man
�pul
at�o
n
March 2006
Air Carbon-Arc Guide
2-13
Use only compressed a�r. Use of combust�ble compressed gases can cause explos�ons result�ng �n personal �njury or death.
SAFETY AND OPERATING REFERENCES1. Code of Federal Regulations. (OSHA) Section 29 Part 1910.95, 132, 133, 134, 139, 251, 252, 253, 254 AND, 1000. U.S. Government Printing Office, Washington, DC 204022. ANSl Z49.1 "Safety In Welding and Cutting"3. ANSI Z87.1 "Practice for Occupational and Educational Eye and Face Protection."4. ANSl Z88.2 "Standard Practice for Respiratory Protection." American National Standards Institute, 1430 Broadway, New York, NY 10018.5. AWS C5.3 "Recommended Practices for Air Carbon-Arc Gouging and Cutting."6. AWS F4.1 "Recommended Safe Practices for Welding and Cutting Containers." The American Welding Society, 550 NW Lejeune RD., P.O.Box 351040, Miami FL. 331357. NFPA 51B "Fire Prevention in Cutting and Welding Processes” National Fire Protection Association, Battery Park. Quincy MA 022698. CSA Standard W117.2, "Safety in Welding. Cutting and Allied Processes" Canadian Standards Association, 178 Rexdale Blvd., Rexdale, Ontario, Canada M9W 1R3
Tabl
e 1
- Rec
omm
ende
d M
inim
um A
ir Re
quire
men
tsRe
com
men
ded
Com
pres
sor R
atin
g
Air
Pres
sure
(1
)
Air
Cons
umpt
ion
Inte
rmitt
ent U
seCo
ntin
uous
Use
ASM
ERe
ceiv
erSi
zeTy
pe o
f Tor
chps
iKp
acf
mL/
min
.hp
kWhp
kWga
llit
.
L�gh
t Dut
y (2
)40
280
822
7.5
0.4
1.5
1.1
6022
7Ge
nera
l Dut
y (2
)80
550
2570
85
3.7
7.5
5.6
8030
3M
ult�p
urpo
se (3
)80
550
3393
47.
55.
610
7.5
8030
3Au
tom
at�c
(4)
6041
446
1303
1511
.280
303
1. P
ress
ure
wh�
le to
rch
�s �n
ope
rat�o
n2.
Acc
omm
odat
es fl
at e
lect
rode
s3.
Gen
eral
ly c
ons�
dere
d a
foun
dry
touc
h4.
Req
u�re
s so
me
k�nd
of m
echa
n�ca
l man
�pul
at�o
n
Air Carbon-Arc Guide
3-14 March 2006
SECTION 3: PRINCIPLES OF OPERATION
General
L�ke arc weld�ng, CAC-A uses an �ntense arc to create a molten pool on the workp�ece. Compressed a�r blows away th�s molten metal.
The process requ�res a weld�ng power source, a�r compressor, carbon electrode and goug�ng torch. F�gure 1 shows how the components are usually arranged:
FIGURE 1
March 2006
Air Carbon-Arc Guide
3-15
Cut or gouge only �n the d�rect�on of a�r flow. The electrode angle w�ll vary, depend�ng on the appl�cat�on. The operator should ma�nta�n the correct arc length to enable a�r to remove molten metal. See F�gure 2.
FIGURE 2
Power Sources
S�ngle-phase mach�nes w�th low open-c�rcu�t voltage may not work for a�r carbon-arc goug�ng (CAC-A). However, any three-phase weld�ng power source of suffic�ent capac�ty may be used for a�r carbon-arc goug�ng. The open-c�rcu�t voltage should be h�gher than the requ�red arc voltage to allow for a voltage drop �n the c�rcu�t. The arc voltage used �n a�r carbon-arc goug�ng and cutt�ng ranges from a low of 35 to a h�gh of 56 volts (V); thus the open-c�rcu�t voltage should be at least
Air Carbon-Arc Guide
3-16 March 2006
Tab
le 2
-Rec
omm
ende
d Nu
mbe
r and
Siz
e of
Wel
ding
Lea
ds
for V
ario
us C
urre
nts
(1,2
) and
Len
gths
(3,4
)
Cur
rent
2
5ft.
(7m
) 50
ft. (1
5m)
100f
t. (3
0m)
150f
t. (4
6m)
200f
t. (6
1 m
) 25
0ft.
(76m
)
Am
ps
No.
Si
ze
No.
S
ize
N
o.
Siz
e
No.
S
ize
N
o.
Siz
e
No.
S
ize
100
1
4
1
3
1
2
1
1
/0
1
2/0
1
4
/0
200
1
3
1
2
1
1
/0
1
3/0
1
3
/0
3
3/0
300
1
2
1
2
1
3
/0
2
2/0
2
4
/0
4
4/0
400
1
2
1
1
/0
1
4/0
2
4
/0
3
4/0
5
4
/0
500
1
1
1
2
/0
2
2/0
2
4
/0
4
4/0
600
1
1
1
3
/0
2
3/0
2
4
/0
5
4/0
800
1
1
/0
2
2/0
2
4
/0
4
4/0
100
0
1
2/0
1
4
/0
3
3/0
5
4
/0
120
0
1
3/0
2
4
/0
3
4/0
1400
14/
02
4/0
43/
0
March 2006
Air Carbon-Arc Guide
3-17
1600
(5)
23/
04
3/0
44/
0
1800
24/
04
4/0
2000
(6)
34/
05
4/0
1. R
ecom
men
dat�o
ns a
re b
ased
on
4V, D
C dr
op11
00 ft
.
2. F
or A
C us
e ne
xt h
eav�
er s
�ze.
3. T
he le
ngth
g�v
en �s
one
hal
f the
sum
of t
he e
lect
rode
and
gro
und
lead
s.
4. I
nade
quat
e gr
ound
�ng
caus
es c
able
ove
rhea
t�ng;
at l
east
1 �n
.2 (64
5mm
2 ) o
f con
tact
per
100
0 am
ps.
5. O
ver 1
600
amps
, a h
eavy
-dut
y, a
�r-co
oled
con
cent
r�c c
able
sho
uld
be u
sed.
6. O
ver 2
000
amps
, a h
eavy
-dut
y, w
ater
-coo
led
conc
entr�
c ca
ble
shou
ld b
e us
ed.
Air Carbon-Arc Guide
3-18 March 2006
60V. The actual arc voltage �n a�r carbon-arc goug�ng and cutt�ng �s governed by arc length and the type of goug�ng.
Except for spec�al uses d�scussed later, CAC-A �s used w�th DCEP (reverse polar�ty). The electrode should extend at most 7 �n. (178mm) from the goug�ng torch w�th the a�r jet between the electrode and workp�ece. A m�n�mum extens�on of 2” should be used. Damage to the torch parts w�ll occur �f the st�ckout of the electrode �s less than the 2”.
Compressed Air
Use ord�nary compressed a�r for a�r carbon-arc goug�ng. Normal pressures range between 80 ps� (551.6kPa) and 100 ps� (690kPa) at the torch; h�gher pressures may be used, but they don’t remove metal more effic�ently. Use 60 ps� (413.7kPa) w�th the l�ght-duty manual torch. Don’t use pressures th�s low w�th general duty torches.
Regardless of the pressure used w�th manual torches, the a�r hose supply�ng a�r to the cable assembly connected to the torch body should have an �ns�de d�ameter (ID) of at least 3/8 �n. (6.4mm).
Mechan�zed torches w�th automat�c arc-length control should have an a�r-supply hose w�th a m�n�mum ID of 1/2 �n. (12 mm).
March 2006
Air Carbon-Arc Guide
3-19
Table 1 g�ves the consumpt�on rates of compressed a�r for the manual and mechan�zed torches and the compressor power rat�ng for �nterm�ttent and cont�nuous use. Be sure the compressor’s rece�ver tank �s large enough for the compressor rat�ng.
Electrodes
There are three types of electrodes.
DC copper-coated electrodes:Th�s type �s most w�dely used because of �ts comparat�vely long electrode l�fe, stable arc character�st�cs and groove un�form�ty. These electrodes are made from m�x�ng carbon and graph�te w�th a b�nder. Bak�ng th�s m�xture produces dense, homogeneous graph�te electrodes of low electr�cal res�stance, wh�ch are then coated w�th a controlled th�ckness of copper. These electrodes are ava�lable �n these d�ameters:
1/8” (3.2 mm), 5/32” (4.0 mm), 3/16” (4.8 mm), 1/4” (6.4 mm), 5/16” (7.9 mm), 3/8” (9.5 mm), 1/2” (12.7 mm)
Jo�nted electrodes work w�thout stub loss. They are furn�shed w�th a female socket and a match�ng male tang, and come �n the follow�ng d�ameters:
5/16” (7.9 mm), 3/8” (9.5 mm), 1/2” (12.7 mm), 5/8” (15.9 mm), 3/4” (19.1 mm), and 1” (25.4 mm)
Air Carbon-Arc Guide
3-20 March 2006
Flat (rectangular) coated electrodes come �n these s�zes:
5/32” (4.0 mm) x 3/8” (9.5 mm) and 3/16” (4.8 mm) x 5/8” (1 5.9 mm)
These electrodes make rectangular grooves and remove weld re�nforcements.
DC pla�n electrodes:These electrodes are used �n d�ameters of less than 3/8 �n. (9.5 mm). Dur�ng goug�ng they consume more rap�dly than coated electrodes. They are made l�ke the coated electrodes, but w�thout the copper coat�ng. Pla�n electrodes are ava�lable �n these d�ameters:
5/32” (4.0 mm), 3/16” (4.8 mm),1/4” (6.4 mm), 5/16” (7.9 mm),3/8” (9.5 mm)
AC coated electrodes:These electrodes are made from carbon, graph�te and a spec�al b�nder. Rare-earth mater�als are added to ensure arc stab�l�zat�on when us�ng alternat�ng current. These electrodes, coated w�th copper, are ava�lable �n these d�ameters:
3/16” (4.8 mm), 1/4” (6.4 mm) and 3/8” (9.5 mm)
March 2006
Air Carbon-Arc Guide
3-21
Tabl
e 3
- Sug
gest
ed C
urre
nt R
ange
s Fo
r Com
mon
ly U
sed
Elec
trode
Typ
es A
nd S
izes
Elec
trode
Dia
met
erDC
Ele
ctro
de W
ith D
CEP
AC E
lect
rode
With
AC
AC E
lect
rode
With
DCE
N
in.
mm
Min
imum
Am
psM
axim
um
Amps
Min
imum
Am
psM
axim
um
Amps
Min
imum
Am
psM
axim
um
Amps
1/8
3.2
6090
5/32
4.0
9015
0
3/16
4.8
200
250
200
250
150
180
1/4
6.4
300
400
300
400
200
250
5/16
7.9
350
450
3/8
9.5
450
600
350
450
300
400
1/2
12.7
800
1000
5/8
15.9
1000
1250
3/4
19.1
1250
1600
125
.416
0022
00
Air Carbon-Arc Guide
3-22 March 2006
Welding Cable Leads
Table 2 g�ves the recommended number and s�zes of weld�ng leads for d�fferent currents and lengths.
Manual Gouging TorchesA manual torch �s shown �n F�g. 3. The electrode �s held �n a sw�vel head, conta�n�ng one or more a�r holes, so that, regardless of the angle of the electrode to the goug�ng torch, the a�r jet stays al�gned w�th the electrode.
Torches w�th two heads (the a�r jet �s on two s�des of the electrode) or w�th a fixed angle between the electrode and the holder, are better for some uses - e.g. remov�ng pads and r�sers from large cast�ngs (padwash�ng).
Torches are usually a�r cooled. For h�gh-current appl�cat�ons, water-cooled cable assembl�es may be used w�th heavy-duty torches.
FIGURE 3
March 2006
Air Carbon-Arc Guide
4-23
SECTION 4: OPERATING TECHNIQUES
Controlling Automatic Gouging Torches
There are two methods of controll�ng automat�c a�r carbon-arc goug�ng torches. E�ther method can make grooves of cons�stent depth to a tolerance of +/-0.025 �n. (+/- 0.64 mm). These automat�c un�ts are used to ach�eve h�gh qual�ty gouges and �ncrease product�on. (See F�gure 4) The methods are as follows:
A) An amperage-controlled method wh�ch ma�nta�ns the arc current by amperage s�gnals through sol�d-state controls. Th�s method controls the electrode feed speed, wh�ch ma�nta�ns the preset amperage. It �s run w�th constant-voltage (CP) power sources only.
B) A voltage-controlled method that ma�nta�ns arc length by voltage s�gnals through sol�d-state electron�c controls. Th�s method controls the electrode feed speed, wh�ch ma�nta�ns the preset voltage. It can run w�th constant current (CC) power suppl�es.
The N6000 Automat�c Goug�ng System developed by Arca�r® can run on e�ther “CC” or “CP”.
Air Carbon-Arc Guide
4-24 March 2006
FIGURE 4
Gouging With manual Torches
The electrode should be gr�pped, as shown �n F�gure 2, so a max�mum of 7 �n. (178 mm) extends from the torch.
For alum�num, th�s extens�on should be 3 �n. (76.5 mm). Table 3 shows suggested currents for the d�fferent electrode types and s�zes.
The a�r jet should be turned on before str�k�ng the arc, and the torch should be held as shown �n F�gure 5. The electrode
March 2006
Air Carbon-Arc Guide
4-25
slopes back from the d�rect�on of travel w�th the a�r jet beh�nd the electrode.
FIGURE 5
Dur�ng goug�ng, the a�r jet sweeps beneath the electrode end and removes all molten metal. The arc may be struck by l�ghtly touch�ng the electrode to the workp�ece. The electrode should not be drawn back once the arc �s struck.
Goug�ng �s d�fferent from arc weld�ng �n that metal �s removed, not depos�ted. A short arc should be ma�nta�ned by work�ng �n the d�rect�on of the cut fast enough to keep up w�th metal removal. Stead�ness of movement controls the smoothnessof the result�ng cut.
Air Carbon-Arc Guide
4-26 March 2006
For goug�ng vert�cally, the goug�ng torch should be held as shown �n F�gure 6. Goug�ng should be done downh�ll, perm�tt�ng grav�ty to help remove the molten metal.
Vert�cal goug�ng may be done uph�ll, but do�ng so �s d�fficult. Goug�ng hor�zontally may be done e�ther to the r�ght or left, but always w�th forehand goug�ng.
FIGURE 6
In goug�ng to the left, the torch should be held as shown �n F�gure 7. In goug�ng to the r�ght, the torch should be reversed. Pos�t�on the a�r jet beh�nd the electrode. When goug�ng �n the overhead pos�t�on, as shown �n F�gure 8, the
March 2006
Air Carbon-Arc Guide
4-27
electrode and torch should be held so molten metal won’t dr�p on the operator’s glove.
FIGURE 7
The groove’s depth �s controlled by travel speed. Grooves up to 1 �n. (25 mm) deep may be made. However, the deeper the groove, the more exper�enced the operator needs to be. Slow travel speed w�ll produce a deep groove. Fast travel speeds w�ll produce a shallow groove. The w�dth of the groove �s determ�ned by the s�ze of the electrode used. The groove �s usually about 1/8 �n. (3.2 mm) w�der than the electrode’s
Air Carbon-Arc Guide
4-28 March 2006
d�ameter. A w�der groove may be made w�th a small electrode that �s osc�llated �n a c�rcular or weave mot�on.
When goug�ng, a push angle of 35 degrees from the surface of the workp�ece should be used for most appl�cat�ons. A steady rest w�ll ensure a smoothly gouged surface, espec�ally �n the overhead pos�t�on.
FIGURE 8
Proper travel speed depends on the s�ze of the electrode, on the base metal, on amperage and on a�r pressure. Proper speed, produc�ng a smooth h�ss�ng sound, w�ll result �n a good gouge.
March 2006
Air Carbon-Arc Guide
4-29
Severing
F�gure 9 shows the electrode ready for sever�ng. The sever�ng techn�que �s l�ke goug�ng, except the operator holds the electrode at a steeper angle, between 70 and 80 degrees to the surface of the workp�ece.
FIGURE 9
For cutt�ng th�ck nonferrous metals, the electrode should be held perpend�cular to the workp�ece, w�th the a�r jet favor�ng the s�de you w�sh to use. W�th the electrode �n th�s pos�t�on, the operator can sever the metal by mov�ng the arc up and down w�th a saw�ng mot�on.
Air Carbon-Arc Guide
4-30 March 2006
Washing
In us�ng the a�r carbon-arc process for remov�ng metal from large areas, surfac�ng metal and r�ser pads on cast�ngs, the operator should pos�t�on the electrode as shown �n F�gure 10. Weave the electrode from s�de to s�de wh�le push�ng forward at the depth des�red. In the pad-wash�ng operat�on, use an angle of 15 to 70 degrees to the workp�ece. The 15-degree angle �s used for l�ght fin�sh�ng passes, wh�le steeper angles allow deeper rough goug�ng to be done w�th greater ease.
FIGURE 10
Well-su�ted for th�s appl�cat�on are goug�ng torches w�th fixed-angle heads that hold the electrode at the correct angle. W�th other types of torches, be sure to keep the a�r beh�nd the electrode. The stead�ness of the operator determ�nes the smoothness of the surface produced.
March 2006
Air Carbon-Arc Guide
4-31
BevelingFor one bevel�ng method, used for th�ck plates, the electrode should be held, as �n F�gure 11 (a), w�th a travel angle of 90 degrees and a work angle equal to the bevel angle. The a�r jet should be between the electrode and the workp�ece.
The second method, used for th�n plates, �s shown �n F�gure ll,(b). The torch should be parallel to the edge be�ng beveled and the electrode angle should equal the bevel angle. The a�r jet should be between the electrode and the workp�ece surface.
FIGURE 11
Air Carbon-Arc Guide
4-32 March 2006
Tab
le 4
-Aut
omat
ic C
AC-A
U-G
roov
e Op
erat
ing
Data
E
LECT
RODE
D
ESIR
ED D
EPTH
S
PEED
IN/M
IN.
AM
PS
INCH
M
M
INCH
M
M
INCH
M
M
DC
5/
167.
941/
8 3
.18
6
5
165
1
400
5/
167.
943/
16 4
.76
4
5
114
3
400
5/
167.
941/
4 6
.35
3
6
914
4
00
5/16
7.94
5/16
7.9
4
33
8
38
400
5/
167.
947/
16 1
1.11
2
2.5
5
72
400
3/
89.
531/
8 3
.18
7
0
177
8
500
3/
89.
533/
16 4
.76
4
4
111
8
500
3/
89.
531/
4 6
.35
3
5
889
5
00
3/8
9.53
3/8
9.5
3
20
5
08
500
3/
89.
539/
16 1
4.29
1
7.5
4
45
500
1/
212
.71/
8 3
.18
9
6
243
8
850
1/
212
.71/
4 6
.35
5
7
144
8
850
1/
212
.73/
8 9
.53
3
5
889
8
50
1/2
12.7
1/2
12.7
2461
085
0
March 2006
Air Carbon-Arc Guide
4-33
1/2
12.7
3/4
19.0
517
.544
585
05/
815
.88
1/4
6.35
7218
2912
505/
815
.88
3/8
9.53
4812
1912
505/
815
.88
1/2
12.7
3794
012
505/
815
.88
5/8
15.8
830
762
1250
5/8
15.8
815
/16
23.8
119
.549
512
503/
419
.05
1/4
6.35
7218
2914
003/
419
.05
3/8
9.38
4210
6814
003/
419
.05
1/2
12.7
3486
514
003/
419
.05
5/8
15.8
827
687
1400
3/4
19.0
53/
419
.05
2256
014
003/
419
.05
1 1/
828
.58
1433
014
00If
you
wan
t a g
roov
e de
pth
grea
ter t
han
1-1/
2 t�m
es th
e d�
amet
er o
f the
ele
ctro
de b
e�ng
use
d,
mak
e th
e gr
oove
�n tw
o or
mor
e pa
sses
Tabu
lat�o
ns a
re b
ased
on
the
labo
rato
ry c
ond�
t�ons
. Us
e th
�s �n
form
at�o
n as
a g
u�de
and
adj
ust
for fi
eld
var�a
nce.
Air Carbon-Arc Guide
4-34 March 2006
Tabl
e 5
- Aut
omat
ic C
AC-A
J-G
roov
e Op
erat
ing
Data
Mat
’lEl
ectro
de D
ata
Elec
trode
Ove
rhan
g (in
ch) P
ass
Pow
er D
ata
Trav
el S
peed
(ipm
)Ai
r
Size
Size
Angl
eSt
ick
Out
12
3Am
psVo
lts1
23
Pass
Ov
eral
l Sp
eed
CFM
PSI
3/8
5/16
453.
0.0
6345
042
.065
6547
60
1/2
5/16
453.
0.0
6345
042
.035
3547
60
5/8
3/8
453.
0.0
63.0
6360
042
.050
5025
4760
3/4
3/8
453.
0.0
63.0
6360
042
.037
3718
.547
60
15/
845
3.0
.125
.125
1250
42.0
4040
2047
60
1.5
5/8
453.
0.0
63.0
63.0
6312
5042
.047
4747
1647
60
2.0
5/8
453.
0.1
25.1
25.1
2512
5042
.028
2828
9.5
4760
March 2006
Air Carbon-Arc Guide
5-35
SECTION 5: EQUIPMENT SELECTION
Gouging TorchChosen for the job be�ng done, torches range from l�ght-duty farm and body-shop s�zes to extra heavy-duty foundry torches. Here �s a gu�de for torch use:
Angle-Arc® Torches:
K2000TM - L�ght-duty general purpose torch - accepts 1/8” (3.2 mm) to 1/4” (6.5 mm) round electrodes and 3/8” (9.5 mm) flat electrodes. Max�mum of 450 amperes.
K3000TM - Med�um-duty general purpose torch - accepts 5/32” (3.97 mm) to 3/8” (9.5 mm) round electrodes and 3/8” (9.5 mm) flat electrodes. Max�mum of 600 amperes.
K4000® - Heavy-duty general purpose torch - accepts 5/32” (3.97 mm) to 1/2” (12.7 mm) round electrodes and 3/8” (9.5 mm) and 5/8” (15.9 mm) flat electrodes. Max�mum of 1000 amperes.
Foundry-Heavy Duty.. . Tr�-Arc®
General foundry work and heavy-duty fabr�cat�on. L�m�ted to 1600 amps w�th a�r-cooled cables and 2000 amps w�th water-cooled cables.
Air Carbon-Arc Guide
5-36 March 2006
Automat�c...Arca�r-Mat�c® N6000Edge preparat�ons and backgoug�ng, h�gh qual�ty and h�gh product�v�ty uses. Used w�th 5/16” - through 3/4” jo�nted carbons.
Power Sources
Any three-phase weld�ng power source w�th enough capac�ty may be used for the a�r carbon-arc goug�ng process. However, be sure the open c�rcu�t voltage �s h�gh enough to allow for a voltage drop �n the c�rcu�t. Some constant voltage w�th droop�ng character�st�cs requ�re very h�gh OCV to run a�r carbon-arc goug�ng equ�pment. S�ngle-phase power sources are usually too small for th�s process.
Power sources �n conjunct�on w�th mechan�zed goug�ng should be 100% duty cycle for the requ�red amperage.
DC...constant current (motor generator, rect�fier, or res�stor gr�d un�t).Preferred power supply for all electrode s�zes.
DC...constant voltage (motor generator or rect�fier).Usable only for 5/16 �n. (7.9 mm) and larger d�ameter electrodes. May cause carbon depos�ts w�th smaller electrodes. Not su�table for automat�c torches w�th voltage control only.
March 2006
Air Carbon-Arc Guide
5-37
AC...AC constant current (transformer).Recommended for AC electrodes only.
AC/DC transformer rect�fiersDC suppl�ed from three-phase transformer rect�fier sources �s sat�sfactory, but DC from s�ngle-phase suppl�es g�ves unsat�sfactory arc character�st�cs. AC output from AC/DC �s sat�sfactory, prov�ded AC electrodes are used.
Automatic Systems
Automat�c systems are often used �n today’s fabr�cat�on �ndustry. These systems offer a h�gh qual�ty, h�gh-product�v�ty alternat�ve to manual goug�ng. There are two types of systems to be cons�dered, both operat�ng on a s�gnal from the arc to control goug�ng.
Dual-Signal System
W�th th�s type of automat�c system, e�ther constant current (CC) or constant voltage (CV) power suppl�es can be used. When on CC, the arc length �s ma�nta�ned through a voltage-s�gnal system. A predeterm�ned voltage sett�ng �s set on the system controller, wh�ch then advances or retracts the electrode through a stepp�ng motor to ma�nta�n the arc length. On a CV power supply, amperage sens�ng controls the feed or retract of the electrode to ma�nta�n the r�ght arc current.
Air Carbon-Arc Guide
5-38 March 2006
Single Signal System
L�ke the dual-s�gnal system, th�s system also ma�nta�ns arc length through a voltage s�gnal. It w�ll not, however, operate w�th an amperage s�gnal. Th�s type of system operates only on a CC power supply.
Advantages
Automat�c CAC-A systems ensure better product�v�ty and qual�ty. The systems can do out-of-pos�t�on goug�ng. They do well at mak�ng long gouges �n flat work p�eces w�th a mov�ng goug�ng apparatus and for mak�ng c�rcular gouges �n p�pes and tanks w�th the goug�ng apparatus rema�n�ng stat�onary.
They make an even U-groove shape and can control depth of groove to w�th�n + /- 0.025 �n. (+ /- 0.64 mm). Tables 4 and 5 show operat�ng �nformat�on for both U and J-grooves.
March 2006
Air Carbon-Arc Guide
6-39
SECTION 6: IMPORTANT PROCESS VARIABLES
Process Variables
L�ke any thermal-cutt�ng process, a�r carbon-arc goug�ng �s sens�t�ve to var�ables �n operat�on. Var�ables can cause changes �n the fin�shed gouge that range from undetectable to unacceptable results. Here are some var�ables �n a�r carbon-arc process:
Electrode D�ameter - Determ�nes the s�ze of the groove.
Amperage - Determ�ned by the d�ameter of electrode be�ng used. Th�s current flow melts the base metal.
Voltage - The pressure beh�nd the amperage, or arc force. Determ�ned by arc length on CC power suppl�es and set on CV power suppl�es.
A�r Pressure and Flow Rate - The med�um for remov�ng molten metal.
Travel Speed - Determ�nes the depth/qual�ty of a fin�shed groove.
Electrode Travel and Work Angle - Can determ�ne groove shape.
Air Carbon-Arc Guide
6-40 March 2006
Electrode Extens�on - Affects metal removal rates and qual�ty of groove.
Base Metal - Affects many other var�ables.
Electrode Diameter and Type
The electrode’s s�ze and type determ�ne groove s�ze. The electrode also affects product�v�ty, groove qual�ty and metal-removal rates. The w�dth of the groove w�ll be about 1/8 �n. w�der than the d�ameter of the electrode.
Choose the proper electrode by the s�ze of the groove you want. Ava�lable power w�ll d�ctate the outer l�m�t. For example, a 1/2 �n. w�de, 1/4 �n. deep groove 10 �n, long could be made manually �n two passes us�ng a 1/4 �n. electrode, or �n one pass w�th a 3/8 �n. d�ameter electrode. In the first case, the best goug�ng rate would be 10 �nches per m�nute (�pm) d�v�ded by 2 or 5 �pm. The latter travel speed �s 17 �pm.
Here the 3/8” d�ameter electrode g�ves a 200% �ncrease �n goug�ng rate that could offset the added electrode cost. Automat�c systems further �ncrease the product�v�ty rate through fin�te control of the arc voltage.
Amperage
The goug�ng amperage �s the process’s melt�ng force. It �s affected by electrode s�ze. If the amperage were set too
March 2006
Air Carbon-Arc Guide
6-41
low for the electrode s�ze, the melt�ng rate of the base metal would be �nadequate and free carbon depos�ts would occur. Although the base metal would melt, a sett�ng too h�gh would rap�dly deter�orate the electrode wh�le reduc�ng the metal removed per electrode. Too h�gh a sett�ng could also substant�ally reduce torch l�fe.
Voltage
Is the pressure or arc force that enables the current to flow across the arc gap. CAC-A often requ�res a h�gher voltage than do most weld�ng processes. To ensure proper operat�on, use a power supply w�th h�gh enough open-c�rcu�t voltage to ma�nta�n a 28-volt operat�ng m�n�mum. Not enough voltage can create a sputter�ng arc or �t can prevent arc establ�shment, result�ng �n uneven grooves and probably free carbon depos�ts. These requ�re excess�ve gr�nd�ng to remove.
Air Pressure and Flow Rate
The a�r jet removes molten metal. Adequate pressure and flow rate are requ�red for proper results. Keep �n m�nd that a�r volume or (cfm) �s as �mportant as a�r pressure. Pressure �s the speed of a�r that moves the molten metal from the groove. If there �s not enough a�r volume or (cfm) to l�ft molten mater�al out of the groove, the pressure or veloc�ty cannot remove �t. The result �s excess�ve slag adhes�on and unnecessary gr�nd�ng to clean up the groove.
Air Carbon-Arc Guide
6-42 March 2006
Travel Speed
Affects the depth of the gouge and the qual�ty of the groove. The faster the travel of an electrode, the shallower the gouge. Use a smaller electrode, �f the travel speed �s too fast for the operator’s comfort, or try automat�c goug�ng. Mak�ng a groove too deep for the electrode’s d�ameter results �n a poor qual�ty groove that requ�res much gr�nd�ng.
Electrode Push Angle
The electrode’s push angle can vary somewhat. When goug�ng manually, a steeper angle tends to g�ve a more V-shaped groove, wh�le w�th the automat�c system a steeper angle g�ves a sl�ghtly deeper groove at the same travel speed.
Base Metals
Gouging Recommendations
The follow�ng procedures are recommended:
For Carbon steel and low alloy steel, such as ASTM A514 and A517 - Use DC electrodes w�th DCEP (electrode pos�t�ve). AC electrodes w�th an AC transformer can be used, but for th�s appl�cat�on, AC �s only half as effic�ent as DC.
For Sta�nless steel - Same as for carbon steel.
March 2006
Air Carbon-Arc Guide
6-43
For Cast �ron, �nclud�ng malleable and duct�le �ron (nodular) - Use 1/2” or larger electrodes at the h�ghest rated amperage.
Use spec�al techn�ques when goug�ng these metals. The push angle should be at least 70-degrees off the workp�ece. The depth of the cut should not exceed 1/2 �nch per pass.
For Copper alloys (copper content 60% and under) - Use DC electrodes w�th DCEN (electrode negat�ve) at the electrode’s h�ghest amperage rat�ng.
For Copper alloys (copper content over 60% or s�ze of workp�ece �s large) - Use DC electrodes w�th DCEN at max�mum amperage rat�ng of the electrode or use AC electrodes w�th AC.
For Alum�num Bronze and Alum�num N�ckel Bronze (spec�al naval propeller alloy) - Use DC electrodes w�th DCEN.
For N�ckel alloys (n�ckel content �s over 80% of mass) - Use AC electrodes w�th AC.
For N�ckel alloys (n�ckel content less than 80% of mass) - Use DC electrodes w�th DCEP.
For Magnes�um alloys - Use DC electrodes w�th DCEP. Before weld�ng, w�re brush groove.
Air Carbon-Arc Guide
6-44 March 2006
For Alum�num - Use DC electrodes w�th DCEP. You must w�re brush w�th sta�nless w�re brushes before weld�ng. Electrode extens�on (length of electrode between torch and work) should not exceed 3 �n. (76.2 mm). DC electrodes w�th DCEN can also be used.
For T�tan�um, Z�rcon�um, Hafn�um, and the�r alloys - Don’t cut or gouge to prepare for weld�ng or remelt�ng unless you mechan�cally remove surface layer from cut surface.
NOTE
If you preheat for weld�ng, preheat for goug�ng.
Effects of the CAC-A Process on Base Metals
Here �s what happens metallurg�cally dur�ng goug�ng and cutt�ng w�th the a�r carbon-arc process.
W�th DCEP and the correspond�ng half cycle of alternat�ng current, the current flow carr�es �on�zed carbon atoms from the electrode to the base metal. The free carbon part�cles are qu�ckly absorbed by the melted base metal. S�nce th�s absorpt�on �s sure to happen, be sure that all carbur�zed molten metal �s removed from the kerf, us�ng the a�r jet.
When the a�r carbon-arc process �s used under �mproper cond�t�ons, carbur�zed molten metal may be left on the workp�ece surface. Its color �s usually a dull gray-black, �n
March 2006
Air Carbon-Arc Guide
6-45
Tabl
e 6
- Res
ults
of C
orro
sion
Tes
ting
on T
ype
304L
Sta
inle
ss.
Spec
imen
Id
entifi
catio
nW
eldi
ng
Proc
ess
Wel
ding
Po
sitio
nRo
otPr
epar
atio
nCo
rros
ion
Rate
(per
mon
th)
�n.
mm
HC1
GMAW
Hor�z
onta
lCA
C-A
Goug
�ng
0.00
0593
0.01
505
HC2
GTAW
Hor�z
onta
lCA
C-A
Goug
�ng
0.00
0594
0.01
509
HG1
GMAW
Hor�z
onta
lGr
�nd�
ng0.
0006
460.
0164
HG2
GTAW
Hor�z
onta
lGr
�nd�
ng0.
0006
180.
0157
VC1
GMAW
Vert�
cal
CAC-
A Go
ug�n
g0.
0006
860.
0174
2VC
2SM
AWVe
rt�ca
lCA
C-A
Goug
�ng
0.00
0627
0.01
593
VGSM
AWVe
rt�ca
lGr
�nd�
ng0.
0006
670.
0169
5OG
SMAW
Over
head
Gr�n
d�ng
0.00
0632
0.01
605
OCSM
AWOv
erhe
adCA
C-A
Goug
�ng
0.00
0645
0.01
638
Air Carbon-Arc Guide
6-46 March 2006
contrast to the br�ght blue of the properly made groove. Inadequate a�r flow may leave small pools of carbur�zed metal �n the bottom of the groove. Irregular electrode travel, espec�ally �n a manual operat�on, may cause r�pples �n the groove wall that trap the carbur�zed metal. F�nally, an �mproper electrode push angle may cause small beads of carbur�zed metal to rema�n on the groove’s edge.
If th�s carbur�zed metal stays on the cut surface, �t can affect the workp�ece when �t �s welded aga�n. These effects depend on the amount of carbur�zed metal present, the weld�ng process used, the k�nd of base metal, and the weld qual�ty requ�red. Although you m�ght th�nk filler metal put on the surface dur�ng weld�ng would absorb small pools or beads of carbur�zed metal, work w�th steel base metals shows that trace metal w�th only 1% carbon may stay along the weld �nterface. Such flaws may lessen weld strength and toughness.
Copper from copper-coated electrodes doesn’t transfer to the cut surface �n base metal, unless the process �s �mproperly used.
Remove carbur�zed metal from a cut surface by gr�nd�ng, but prevent hav�ng to do so by goug�ng properly �n the r�ght cond�t�ons.
Stud�es were conducted on sta�nless steel to determ�ne whether a�r carbon-arc goug�ng, carr�ed out �n the prescr�bed manner, adversely affects corros�on res�stance. The stud�es
March 2006
Air Carbon-Arc Guide
6-47
show no s�gn�ficant d�fference �n the corros�on rates for welds prepared by CAC-A and those prepared by gr�nd�ng (See Table 6). Had carbon been absorbed, the corros�on rates for welds backgouged by CAC-A would have been s�gn�ficantly h�gher. In the stud�es, type 304L sta�nless steel was welded us�ng several processes. Backgoug�ng of the jo�nt was performed by a�r carbon-arc goug�ng and by gr�nd�ng. Spec�mens from the jo�nts were subjected to the bo�l�ng-65%-n�tr�c-ac�d test.
Compared to oxy-fuel gas cutt�ng, CAC-A �s a lower-heat-�nput process. Therefore, a work p�ece gouged or cut by CAC-A �s less d�storted. The mach�n�ng of low carbon and non-hardenable steels �s not affected by the a�r carbon-arc process. W�th cast �ron and h�gh-carbon steels, however, th�s process may cause enough harden�ng to make the cut surface tough to mach�ne. St�ll, because the hardened zone �s shallow (approx�mately, 0.06 �n. / 0.15 mm), a cutt�ng tool can penetrate the hardened zone to remove the hardened surface.
Air Carbon-Arc Guide
7-48 March 2006
SECTION 7: ADVANTAGES AND LIMITATIONS
Advantages
Fast - F�ve t�mes faster than ch�pp�ng. Gouges a groove 3/8 �n. (9.5 mm) deep at over 2 ft. (600 mm) per m�nute.
Eas�ly controllable - Prec�sely removes defects. Defects are clearly v�s�ble �n the groove and may be followed w�th ease. The depth of the cut �s eas�ly controlled and slag does not hamper the cutt�ng act�on.
Low cost - Gas cyl�nders and regulators are unnecessary except �n field operat�ons.Econom�cal to operate - No oxygen or fuel gas requ�red. The welder or weld�ng operator may also do the goug�ng or cutt�ng.
Easy to operate - Welders operate the equ�pment after only a few m�nutes and become sk�lled �n a few days. The torch conta�ns an a�r-control valve and sw�vel head that perm�t chang�ng the electrode angle to su�t the job wh�le ma�nta�n�ng a�r-jet al�gnment.Compact- Not much larger than a sh�elded metal arc weld�ng torch.
Versat�le - Use �t anywhere you weld. May be operated �n spaces too restr�cted for a ch�pp�ng hammer or an oxy-fuel
March 2006
Air Carbon-Arc Guide
7-49
gas cutt�ng torch. Needs no d�fficult adjustments for use on d�fferent metals.
Clean cutt�ng - Result�ng surface �s clean and smooth. Weld�ng or braz�ng �s often done w�thout further gr�nd�ng or clean�ng of the groove.
Air Carbon-Arc Guide
7-50 March 2006
AREA
S OF
APP
LICA
TION
The
a�r c
arbo
n-ar
c go
ug�n
g pr
oces
s ha
s be
en u
sed
�nAg
ricul
ture
Prep
ar�n
g fo
r wel
d�ng
the
jo�n
ts o
f bro
ken
met
als
on fa
rm
mac
h�ne
ry.
Rem
ov�n
g su
rfac
e w
elds
. Se
ver�n
g m
etal
s.Ai
rcra
ftM
a�nt
a�n�
ng g
roun
d eq
u�pm
ent a
nd a
�rpor
t stru
ctur
es.
Re-w
ork�
ng d
�es
and
fixtu
res.
Auto
mot
ive
Ma�
nta�
n�ng
equ
�pm
ent.
Pre
par�n
g br
oken
cas
t-�ro
n pa
rts.
Seve
r�ng
met
als.
Rem
ov�n
g br
oken
or s
e�ze
d be
ar�n
g ra
ces,
col
lars
, etc
., fro
m s
hafts
.Bo
iler S
hops
Rem
ov�n
g r�v
ets
and
defe
ct�v
e w
elds
. Pr
epar
�ng
crac
ks
for r
e-w
eld�
ng.
Rem
ov�n
g tu
bes
from
tube
she
ets.
Brew
erie
sM
a�nt
a�n�
ng e
qu�p
men
t, va
ts, p
�p�n
g, e
tc..
Cutt�
ng a
nd
goug
�ng
all t
ypes
of m
etal
s, e
spec
�ally
sta
�nle
ss s
teel
s.Ch
emic
al P
lant
sPr
epar
�ng
equ�
pmen
t and
p�p
�ng
of s
ta�n
less
ste
el a
nd
nonf
erro
us m
etal
s fo
r rep
a�r a
nd a
ltera
t�on
by w
eld�
ng.
March 2006
Air Carbon-Arc Guide
7-51
AREA
S OF
APP
LICA
TION
The
a�r c
arbo
n-ar
c go
ug�n
g pr
oces
s ha
s be
en u
sed
�nCo
nstru
ctio
nPr
epar
�ng
jo�n
ts fo
r wel
d�ng
. Re
mov
�ng
defe
cts
�n w
elds
. Fa
br�c
at�n
g w
�thou
t bev
el�n
g. R
emov
�ng
hold
�ng
cl�p
s,
l�ft�n
g pa
ds, e
tc.,
w�th
out d
amag
e to
pad
s or
stru
ctur
e.
Ma�
nta�
n�ng
equ
�pm
ent.
Dred
ging
Ma�
nta�
n�ng
equ
�pm
ent.
Prep
ar�n
g m
anga
nese
ste
el
parts
for r
epa�
r by
wel
d�ng
. Re
mov
�ng
surf
ac�n
g fo
r re
surf
ac�n
g.Fo
undr
ies
Padw
ash�
ng. R
emov
�ng
fins
and
r�ser
s. R
emov
�ng
crac
ks,
sand
poc
kets
, and
oth
er d
efec
ts fr
om c
ast�n
g. M
a�nt
a�n�
ng
equ�
pmen
t.Su
rfaci
ngRe
mov
�ng
old
surf
ace
wel
ds fo
r re-
surf
ac�n
g. P
repa
r�ng
sta�
nles
s an
d m
anga
nese
ste
els
for w
eld�
ng. R
emov
�ng
defe
ct�v
e w
elds
.
Air Carbon-Arc Guide
7-52 March 2006
AREA
S OF
APP
LICA
TION
The
a�r c
arbo
n-ar
c go
ug�n
g pr
oces
s ha
s be
en u
sed
�nLu
mbe
r Ind
ustr
yM
a�nt
a�n�
ng e
qu�p
men
t. Re
mov
�ng
surf
ace
wel
ds fo
r re
surf
ac�n
g. D
�sm
antl�
ng d
amag
ed e
qu�p
men
t for
repa
�r an
d re
use.
Pre
par�n
g ca
st �r
on fo
r wel
d�ng
or
braz
�ng
wel
d�ng
.M
aint
enan
ce S
hops
D�sm
antl�
ng a
nd re
mod
el�n
g eq
u�pm
ent.
Rem
ov�n
g su
rfac
�ng
wel
ds fo
r res
urfa
c�ng
. Sev
er�n
g m
etal
s.
Prep
ar�n
g da
mag
ed a
reas
for r
epa�
r wel
d�ng
.Ar
my/
Mar
ines
Rem
ov�n
g au
sten
�t�c
wel
d m
etal
. Bac
kgou
g�ng
wel
ds
for w
eld�
ng th
e se
cond
s�d
e. S
alva
g�ng
arm
or p
late
s.
Seve
r�ng
met
als.
Rem
ov�n
g de
fect
s �n
wel
dsan
d ca
st�n
gs.
March 2006
Air Carbon-Arc Guide
7-53
AREA
S OF
APP
LICA
TION
The
a�r c
arbo
n-ar
c go
ug�n
g pr
oces
s ha
s be
en u
sed
�nNa
vy/C
oast
Gua
rdRe
mov
�ng
defe
cts
�n w
elds
and
cas
t�ngs
. Bac
kgou
g�ng
to
wel
d th
e se
cond
s�d
e. R
emov
�ng
aust
en�t�
c w
eld
met
als.
Rem
ov�n
g pa
deye
s, d
ogs,
etc
., w
�thou
t dam
age
to a
ttach
men
ts o
r to
ex�s
t�ng
stru
ctur
es. G
roov
�ng
of th
�n
plat
e fo
r wel
d�ng
. Rem
ov�n
g er
oded
are
as o
n sh
�ps’
hul
ls,
ster
n tu
bes,
stru
ts, r
udde
rs, a
nd p
rope
llers
for r
epa�
r by
wel
d�ng
. Rem
ov�n
g of
bul
khea
ds, p
atch
es, a
nd a
cces
s ha
tche
s fo
r reu
se b
y da
mag
e co
ntro
l.M
inin
gM
a�nt
a�n�
ng e
qu�p
men
t. Go
ug�n
g m
anga
nese
ste
els,
cas
t �ro
n, a
nd a
ll no
nfer
rous
met
als.
Rem
ov�n
g su
rfac
e w
elds
an
d ha
rdfa
c�ng
.
Air Carbon-Arc Guide
7-54 March 2006
AREA
S OF
APP
LICA
TION
The
a�r c
arbo
n-ar
c go
ug�n
g pr
oces
s ha
s be
en u
sed
�nOi
l Refi
nerie
sRe
mov
�ng
defe
ct�v
e w
elds
. Cut
t�ng
and
goug
�ng
sta�
nles
s an
d au
sten
�t�c
wel
ds. C
utt�n
g ou
t or p
atch
�ng
tank
bo
ttom
s an
d co
ke-a
nd-p
�pe
st�ll
s. R
emov
�ng
l�ner
s, b
o�le
r an
d he
at-e
xcha
nger
tube
s, a
nd r�
vets
. Rem
ov�n
g de
fect
s an
d pr
epar
�ng
brea
ks �n
cas
t�ngs
for r
epa�
r by
wel
d�ng
. Se
ver�n
g no
nfer
rous
met
als.
Rem
ov�n
g r�s
ers
on c
ast�n
gs.
Prep
ar�n
g th
e su
rfac
e of
ero
ded
and
corr
oded
are
as o
n ac
�d-p
lant
equ
�pm
ent f
or re
bu�ld
�ng
by w
eld�
ng.
Oil D
rillin
gGr
oov�
ng fo
r wel
d�ng
of p
late
s. R
emov
�ng
dr�ll
col
lars
. Re
mov
�ng
surf
ace
wel
ds fo
r re-
surf
ac�n
g. G
oug�
ng o
ut
defe
cts
and
groo
v�ng
edg
es o
f cas
t�ngs
(mud
pum
ps),
etc.
for w
eld�
ng. M
a�nt
a�n�
ng e
qu�p
men
t. Re
mov
�ng
fish
plat
es o
n tru
ck c
hass
�s fo
r ren
ewal
. Gro
ov�n
g of
bro
ken
edge
s fo
r re-
wel
d�ng
.Pa
ckin
g Ho
uses
Prep
ar�n
g eq
u�pm
ent,
vats
and
p�p
�ng
of s
ta�n
less
ste
el
and
nonf
erro
us m
etal
for w
eld�
ng.
March 2006
Air Carbon-Arc Guide
7-55
AREA
S OF
APP
LICA
TION
The
a�r c
arbo
n-ar
c go
ug�n
g pr
oces
s ha
s be
en u
sed
�nPo
wer
Pla
nts
Ma�
nta�
n�ng
equ
�pm
ent.
Groo
v�ng
of m
etal
for w
eld�
ng.
Goug
�ng
out c
ast�n
gs fo
r rep
a�r.
Rem
ov�n
g ca
v�t�e
s fro
m P
elto
n w
heel
s. R
emov
�ng
wel
ded
end
tube
s fro
m
tube
she
ets.
Rem
ov�n
g w
eld�
ng d
efec
ts. G
oug�
ng a
nd
prep
ar�n
g ca
st �r
on fo
r wel
d�ng
or b
raze
wel
d�ng
.Sa
lvag
e Ya
rds
Cutt�
ng s
crap
. Rem
ov�n
g w
elds
w�th
out �
njur
�ng
reus
able
st
ruct
ures
. Cut
t�ng
sta�
nles
s st
eel,
nonf
erro
us m
etal
s, a
nd
cast
�ron
.
Air Carbon-Arc Guide
7-56 March 2006
AREA
S OF
APP
LICA
TION
The
a�r c
arbo
n-ar
c go
ug�n
g pr
oces
s ha
s be
en u
sed
�nRa
ilroa
dsM
a�nt
a�n�
ng e
qu�p
men
t. Re
mov
�ng
jour
nal l
�ner
s, r�
vets
, w
elde
d en
d tu
bes
from
tube
she
ets.
Pre
par�n
g br
eaks
�n
bo�le
rs, fi
re b
oxes
, etc
., fo
r rep
a�r b
y w
eld�
ng. S
alva
g�ng
an
d re
scu�
ng a
fter e
qu�p
men
t wre
ckag
e. P
repa
r�ng
for
wel
d su
rfac
�ng
or �t
s re
mov
al fr
om fr
ogs,
sw
�tche
s,
and
ra�l
ends
. Pre
par�n
g m
anga
nese
ste
el fo
r wel
d�ng
. Re
mov
�ng
r�ser
pad
s an
d de
fect
s fro
m c
ast�n
gs �n
fo
undr
�es.
Pre
par�n
g w
orn
whe
els
for r
ebu�
ld�n
g by
w
eld�
ng.
Ship
build
ing
See
Navy
/Coa
st G
uard
Stai
nles
s Sh
ops
Cutt�
ng s
ta�n
less
ste
el. R
emov
�ng
defe
cts
�n s
ta�n
less
ste
el
cast
�ngs
and
wel
ds.
March 2006
Air Carbon-Arc Guide
7-57
AREA
S OF
APP
LICA
TION
The
a�r c
arbo
n-ar
c go
ug�n
g pr
oces
s ha
s be
en u
sed
�nSt
eel F
abric
atio
nW
eld�
ng a
nd fi
tt�ng
pla
tes
w�th
out b
evel
�ng
by
back
goug
�ng
the
seco
nd s
�de
to s
ound
met
al a
fter w
eld�
ng
the
first
s�d
e. R
emov
�ng
wel
ds fr
om e
x�st
�ng
stru
ctur
es
and
salv
ag�n
g un
dam
aged
mat
er�a
l for
reus
e. C
utt�n
g an
d go
ug�n
g al
l met
als
�n th
e sh
op a
nd a
t the
job
s�te
. M
a�nt
a�n�
ng e
qu�p
men
t.St
eel M
ills
Ma�
nta�
n�ng
equ
�pm
ent.
Cutt�
ng a
nd g
oug�
ng a
ll m
etal
s.
Was
h�ng
b�ll
ets
and
bloo
ms.
Rem
ov�n
g de
fect
s.W
ater
wor
ksPr
epar
�ng
brok
en e
qu�p
men
t for
repa
�r by
wel
d�ng
. Cu
tt�ng
and
gou
g�ng
all
met
als.
Cut
t�ng
cast
-�ron
p�p
e,
espe
c�al
ly c
oncr
ete
l�ned
. Re
mov
�ng
wel
ds s
o de
fect
�ve
p�pe
sec
t�ons
can
be
repl
aced
.W
eldi
ng S
hops
Rem
ov�n
g w
elds
. Cut
t�ng
all m
etal
s, e
spec
�ally
non
ferr
ous
met
als,
sta
�nle
ss s
teel
, and
cas
t �ro
n. G
oug�
ng b
evel
s an
d ba
ckgo
ug�n
g w
eld
root
s. R
emov
�ng
surf
ace
wel
d fo
r re-
surf
ac�n
g.
Air Carbon-Arc Guide
8-58 March 2006
Prob
lem
Larg
e fre
e-ca
rbon
de
posi
t at t
he
begi
nnin
g of
the
groo
ve.
An u
nste
ady
arc,
cau
sing
the
oper
ator
to u
se a
sl
ow tr
avel
spe
ed
even
on
shal
low
gr
oove
s.
Caus
eTh
e op
erat
or e
�ther
neg
lect
ed to
turn
on
the
a�r j
et b
efor
e st
r�k�n
g th
e ar
c,
or th
e to
rch
was
loca
ted
�mpr
oper
ly.
Carb
on ro
d no
t pos
�t�on
ed p
rope
rly �n
he
ad a
ssem
bly.
Not e
noug
h am
pera
ge fo
r the
el
ectro
de d
�am
eter
use
d (s
ee T
able
3)
. Wh�
le th
e lo
wes
t rec
omm
ende
d am
pera
ge m
ay b
e en
ough
, �t r
equ�
res
grea
ter o
pera
tor s
k�ll.
A m
�d-r
ange
am
pera
ge �s
bet
ter.
Solu
tion
The
a�r s
houl
d be
turn
ed o
n be
fore
st
r�k�n
g th
e ar
c an
d sh
ould
flow
bet
wee
n th
e el
ectro
de a
nd th
e w
orkp
�ece
.
Ensu
re c
arbo
n ro
d �s
sea
ted
�n g
roov
e �n
to
rch
head
.
If th
e de
s�re
d am
pera
ge c
anno
t be
obta
�ned
from
the
ava�
labl
e po
wer
sou
rce,
us
e th
e ne
xt s
mal
ler d
�am
eter
ele
ctro
de
or p
aral
lel t
wo
or m
ore
wel
d�ng
pow
er
supp
l�es.
Trou
bles
hoot
ing
March 2006
Air Carbon-Arc Guide
8-59
Prob
lem
Erra
tic g
roov
e w
ith
the
arc
wan
der-
ing
from
sid
e to
si
de a
nd w
ith th
e el
ectro
de h
eatin
g up
rapi
dly.
Inte
rmitt
ent a
rc
actio
n re
sulti
ng in
an
irre
gula
r gro
ove
surfa
ce.
Caus
eTh
e pr
oces
s w
as a
ppar
ently
use
d w
�th D
CEN
(ele
ctro
de n
egat
�ve)
.
The
trave
l spe
ed w
as to
o sl
ow �n
m
anua
l gou
g�ng
. The
ope
rato
r pr
obab
ly s
et h
�s h
and
on o
ther
wor
k fo
r bal
ance
as
sh�e
lded
met
al-a
rc
wel
ders
do.
S�n
ce th
e sp
eed
of a
�r ca
rbon
-arc
gou
g�ng
�s m
uch
fast
er
than
sh�
elde
d m
etal
-arc
wel
d�ng
, fr�
ct�o
n be
twee
n th
e gl
oved
han
d an
d th
e w
orkp
�ece
may
cau
se a
je
rky
forw
ard
mot
�on.
Th�
s m
ot�o
n ca
uses
the
gap
betw
een
the
elec
trode
an
d w
orkp
�ece
to b
ecom
e to
o lar
ge
to m
a�nta
�n th
e ar
c. P
oor g
roun
d co
nnec
t�on.
Solu
tion
Goug
�ng
proc
ess
shou
ld b
e do
ne w
�th
DCEP
(Ele
ctro
de p
os�t�
ve) w
hene
ver
poss
�ble
. D�
rect
cur
rent
ele
ctro
des
shou
ld b
e us
ed w
�th D
CEP
(ele
ctro
de
pos�
t�ve)
on
all m
etal
s, e
xcep
t for
a fe
w
copp
er a
lloys
suc
h as
Sup
erst
on a
nd
N�al
�te. R
efer
to p
age
30 &
31.
The
oper
ator
sho
uld
stan
d co
mfo
rtabl
y so
the�
r arm
s m
ove
freel
y an
d th
e�r
glov
es d
o no
t dra
g on
the
wor
kp�e
ce. I
f yo
u us
e m
echa
n�ze
d eq
u�pm
ent,
chec
k Ta
ble
4 fo
r pro
per o
pera
t�ng
cond
�t�on
s.
Insp
ect g
roun
d cl
amps
and
lead
(s) t
o en
sure
con
nect
�on
prop
er.
Trou
bles
hoot
ing
(Con
t.)
Air Carbon-Arc Guide
8-60 March 2006
Prob
lem
In g
ougi
ng, f
ree
carb
on d
epos
its
at v
aryi
ng g
roov
e in
terv
als;
in p
ad
-was
hing
, fre
e ca
rbon
dep
osits
at
var
ious
spo
ts
on th
e w
ashe
d su
rface
.
Irreg
ular
gro
ove:
to
o de
ep, t
hen
too
shal
low
.
Caus
eTh
e el
ectro
de h
as s
horte
d ou
t on
the
wor
kp�e
ce. I
n m
anua
l gou
g�ng
, th�
s co
nd�t�
on �s
cau
sed
by a
trav
el s
peed
ex
cess
�ve
for t
he a
mpe
rage
use
d an
d fo
r the
dep
th o
f the
gro
ove
be�n
g m
ade.
In m
echa
n�ze
d op
erat
�ons
, th
e co
nd�t�
on �s
cau
sed
e�th
er b
y ex
cess
�ve
trave
l spe
ed o
r by
us�n
g a
flat-c
urve
con
stan
t-vol
tage
pow
er
sour
ce fo
r a s
mal
l d�a
met
er e
lect
rode
5/
16 �n
. (7.
9 m
m).
In p
adw
ash�
ng,
th�s
sho
rt�ng
out
�s c
ause
d by
hol
d�ng
th
e el
ectro
de a
t too
sm
all a
pus
h an
gle.
The
oper
ator
was
uns
tead
y.
Solu
tion
Use
an e
lect
rode
-to-w
ork
angl
eof
15
to 7
0 de
gree
s. A
sm
alle
r ang
le
�ncr
ease
s th
e ar
c�ng
are
a,re
duc�
ng th
e cu
rren
t den
s�ty
; th�
s re
duct
�on
�n a
rc-c
urre
nt d
ens�
tyre
qu�re
s a
grea
t dec
reas
e �n
arc
le
ngth
, to
the
po�n
t of s
hort
c�rc
u�t�n
g. K
eep
a pr
oper
arc
gap
.
The
oper
ator
sho
uld
assu
me
a co
mfo
rtabl
e po
s�t�o
n w
h�le
gou
g�ng
.
Trou
bles
hoot
ing
(Con
t.)
March 2006
Air Carbon-Arc Guide
8-61
Prob
lem
Slag
adh
erin
g to
th
e ed
ges
of th
e gr
oove
.
Caus
eSl
ag e
ject
�on
was
�nad
equa
te. F
or
adeq
uate
sla
g ej
ect�o
n, k
eep
a pr
oper
a�
r pre
ssur
e an
d flo
w ra
te (c
fm).
A�r
pres
sure
bet
wee
n 80
and
100
ps�
(5
50-6
90 k
Pa) m
ay n
ot e
ffect
�vel
y ej
ect a
ll of
the
slag
�f th
e vo
lum
e �s
�n
suffi
c�en
t.
Solu
tion
To d
el�v
er a
dequ
ate
volu
me,
the
a�r
hose
feed
�ng
the
conc
entr�
c ca
ble
asse
mbl
y a
m�n
�mum
�ns�
de d
�am
eter
of
3/8
�n. (
9.5
mm
) for
man
ual
torc
hes.
For
aut
omat
�c to
rche
s, th
e m
�n�m
um h
ose
ID s
houl
d be
1/2
�n
. (12
.7 m
m).
Be s
ure
the
a�r j
et �s
d�
rect
ed p
aral
lel t
o th
e go
uge
area
. Do
not
favo
r one
s�d
e un
less
you
w
ant t
o m
�n�m
�ze s
lag
from
adh
er�n
g to
one
s�d
e of
the
cut.
Trou
bles
hoot
ing
(Con
t.)
Air Carbon-Arc Guide
62 March 2006
NOTES
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