#Ele#Ctrode Welding

8/18/2019 #Ele#Ctrode Welding

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SMAW & TIG WeldingSMAW & TIG Welding


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Shielded metal arc welding (SMAW)Shielded metal arc welding (SMAW),,

Shielded metal arc welding (SMAW)Shielded metal arc welding (SMAW), also known as, also known as manualmanualmetal arc (MMA) weldingmetal arc (MMA) welding or informally asor informally as stick weldingstick welding, is, isa manuala manual arc weldingarc welding process that uses a consumable process that uses a consumable electrodeelectrode coated incoated in fluxflux to lay the weld.to lay the weld.

AnAn electric currentelectric current, in the form of either, in the form of either alternating currentalternating current orordirect currentdirect current from afrom a welding power supplywelding power supply, is used to form an, is used to form anelectric arcelectric arc between the electrode and the between the electrode and the metalsmetals to be oined.to be oined.

As the weld is laid, the flux coating of the electrodeAs the weld is laid, the flux coating of the electrode

disintegrates, gi!ing off !apors that ser!e as adisintegrates, gi!ing off !apors that ser!e as a

shielding gasshielding gas

and pro!iding a layer of slag, both of which protect the weldand pro!iding a layer of slag, both of which protect the weldarea from atmospheric contaminationarea from atmospheric contamination

http://en.wikipedia.org/wiki/Arc_weldinghttp://en.wikipedia.org/wiki/Arc_weldinghttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Flux_(metallurgy)http://en.wikipedia.org/wiki/Flux_(metallurgy)http://en.wikipedia.org/wiki/Current_(electricity)http://en.wikipedia.org/wiki/Current_(electricity)http://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Welding_power_supplyhttp://en.wikipedia.org/wiki/Welding_power_supplyhttp://en.wikipedia.org/wiki/Electric_archttp://en.wikipedia.org/wiki/Electric_archttp://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Shielding_gashttp://en.wikipedia.org/wiki/Shielding_gashttp://en.wikipedia.org/wiki/Shielding_gashttp://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Electric_archttp://en.wikipedia.org/wiki/Welding_power_supplyhttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Current_(electricity)http://en.wikipedia.org/wiki/Flux_(metallurgy)http://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Arc_welding


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"ecause of the !ersatility of the process and the"ecause of the !ersatility of the process and thesimplicity of its e#uipment and operation, shieldedsimplicity of its e#uipment and operation, shielded

metal arc welding is one of the world$s most popularmetal arc welding is one of the world$s most popularwelding processes.welding processes.

%t dominates other welding processes in the%t dominates other welding processes in themaintenance and repair industry, and thoughmaintenance and repair industry, and though

flux&cored arc weldingflux&cored arc welding is growing in popularity,is growing in popularity,SMAW continues to be used extensi!ely in theSMAW continues to be used extensi!ely in theconstruction of steel structures and in industrialconstruction of steel structures and in industrialfabrication.fabrication.

'he process is used primarily to weld'he process is used primarily to weld ironiron andand steelssteels

(including(including stainless steelstainless steel) but) but aluminumaluminum,, nickelnickel andandcopper copper alloysalloys can also be welded with this methodcan also be welded with this method

http://en.wikipedia.org/wiki/Flux-cored_arc_weldinghttp://en.wikipedia.org/wiki/Flux-cored_arc_weldinghttp://en.wikipedia.org/wiki/Ironhttp://en.wikipedia.org/wiki/Ironhttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Aluminumhttp://en.wikipedia.org/wiki/Aluminumhttp://en.wikipedia.org/wiki/Nickelhttp://en.wikipedia.org/wiki/Nickelhttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Alloyhttp://en.wikipedia.org/wiki/Alloyhttp://en.wikipedia.org/wiki/Alloyhttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Nickelhttp://en.wikipedia.org/wiki/Aluminumhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Ironhttp://en.wikipedia.org/wiki/Flux-cored_arc_welding


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'o strike the'o strike the electric arcelectric arc, the electrode is brought into, the electrode is brought intocontact with the workpiece in a short sweepingcontact with the workpiece in a short sweeping

motion and then pulled away slightly.motion and then pulled away slightly.

'his initiates the arc and thus the melting of the'his initiates the arc and thus the melting of the

workpiece and the consumable electrode, and causesworkpiece and the consumable electrode, and causesdroplets of the electrode to be passed from thedroplets of the electrode to be passed from the

electrode to the other .electrode to the other .

As the electrode melts, the flux co!eringAs the electrode melts, the flux co!ering

disintegrates, gi!ing off !apors that protect the welddisintegrates, gi!ing off !apors that protect the weld

area fromarea from oxygenoxygen and otherand other atmosphericatmospheric gases.gases.

http://en.wikipedia.org/wiki/Electric_archttp://en.wikipedia.org/wiki/Electric_archttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Earth%27s_atmospherehttp://en.wikipedia.org/wiki/Earth%27s_atmospherehttp://en.wikipedia.org/wiki/Earth%27s_atmospherehttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Electric_arc


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'o strike the'o strike the electric arcelectric arc, the electrode is brought into contact, the electrode is brought into contactwith the workpiece in a short sweeping motion and then pulledwith the workpiece in a short sweeping motion and then pulled

away slightly.away slightly. 'his initiates the arc and thus the melting of the workpiece'his initiates the arc and thus the melting of the workpiece

and the consumable electrode, and causes droplets of theand the consumable electrode, and causes droplets of theelectrode to be passed from the electrode to the weld.electrode to be passed from the electrode to the weld.

'he heat produced by the arc melts the base metal, the'he heat produced by the arc melts the base metal, theelectrode core rod, and the coating.electrode core rod, and the coating.

As the molten metal droplets are transferred across the arc andAs the molten metal droplets are transferred across the arc andinto the molten weld puddle, they are shielded from theinto the molten weld puddle, they are shielded from theatmosphere by the gases produced from the decomposition ofatmosphere by the gases produced from the decomposition of

the flux coating. 'he molten slag floats to the top of the weldthe flux coating. 'he molten slag floats to the top of the weld puddle where it protects the weld metal from the atmosphere puddle where it protects the weld metal from the atmosphereduring solidificationduring solidification

http://en.wikipedia.org/wiki/Electric_archttp://en.wikipedia.org/wiki/Electric_archttp://en.wikipedia.org/wiki/Electric_arc


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#O$"! !$!CTO"! GON" CA$! WO S#I!$"!" M!TA$ AC W!$"ING CICIT#O$"! !$!CTO"! GON" CA$! WO S#I!$"!" M!TA$ AC W!$"ING CICIT


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#uipment /peration#uipment /peration

& /ne reason for the wide acceptance of the SMAW& /ne reason for the wide acceptance of the SMAW

process is the simplicity of the necessary e#uipment. process is the simplicity of the necessary e#uipment.'he e#uipment consists of the following items. (See'he e#uipment consists of the following items. (Seeigure 0)igure 0)

-. Welding power source-. Welding power source 0. lectrode holder0. lectrode holder 1. round clamp1. round clamp 2. Welding cables and connectors2. Welding cables and connectors

3. Accessory e#uipment (chipping hammer, wire3. Accessory e#uipment (chipping hammer, wire brush) brush)

4. 5rotecti!e e#uipment (helmet, glo!es, etc.)4. 5rotecti!e e#uipment (helmet, glo!es, etc.)


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Welding 5ower SourcesWelding 5ower Sources **

Shielded metal arc welding may utili6e either alternatingShielded metal arc welding may utili6e either alternatingcurrent (A7) or direct current (87), but in either case, thecurrent (A7) or direct current (87), but in either case, the

power source selected must be of the constant current type. power source selected must be of the constant current type. 87 type of power source will deli!er a relati!ely constant87 type of power source will deli!er a relati!ely constant

amperage or welding current regardless of arc lengthamperage or welding current regardless of arc length!ariations by the operator!ariations by the operator

'he amperage determines the amount of heat at the arc and'he amperage determines the amount of heat at the arc andsince it will remain relati!ely constant, the weld beadssince it will remain relati!ely constant, the weld beads

produced will be uniform in si6e and shape. produced will be uniform in si6e and shape. Whether to use an A7, 87, or A7987 power source dependsWhether to use an A7, 87, or A7987 power source depends

on the type of welding to be done and the electrodes used.on the type of welding to be done and the electrodes used.'he following factors should be considered:'he following factors should be considered:


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-.-. !lectr+de Selecti+n!lectr+de Selecti+n & *sing a 87 power source allows the& *sing a 87 power source allows theuse of a greater range of electrode types. While most of theuse of a greater range of electrode types. While most of the

electrodes are designed to be used on A7 or 87, some willelectrodes are designed to be used on A7 or 87, some willwork properly only on 87.work properly only on 87.

0.0. Metal ThicknessMetal Thickness & 87 power sources may be used for& 87 power sources may be used forwelding both hea!y sections and light gauge work. Sheetwelding both hea!y sections and light gauge work. Sheet

metal is more easily welded with 87 because it is easier tometal is more easily welded with 87 because it is easier tostrike and maintain the 87 arc at low currents.strike and maintain the 87 arc at low currents. - "istance .r+m W+rk - "istance .r+m W+rk & %f the distance from the work to the& %f the distance from the work to the

power source is great, A7 is the best choice since the !oltage power source is great, A7 is the best choice since the !oltagedrop through the cables is lower than with 87. !en thoughdrop through the cables is lower than with 87. !en though

welding cables are made of copper or aluminum (both goodwelding cables are made of copper or aluminum (both goodconductors), the resistance in the cables becomes greater as theconductors), the resistance in the cables becomes greater as thecable length increases.cable length increases.


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2.2. Welding '+siti+nWelding '+siti+n "ecause 87 may be operated at lower welding"ecause 87 may be operated at lower weldingcurrents, it is more suitable for o!erhead and !ertical welding than A7. A7currents, it is more suitable for o!erhead and !ertical welding than A7. A7

can successfully be used for out&of&position work if proper electrodes arecan successfully be used for out&of&position work if proper electrodes areselected.selected. 3.3. Arc l+w (Arc l+w (Arc l+w is a /r+0lem that e1ists with m+st electricArc l+w is a /r+0lem that e1ists with m+st electric

welding /r+cesses- It is caused 02 the /re.erential magnetic .ieldswelding /r+cesses- It is caused 02 the /re.erential magnetic .ieldsde3el+/ed near the arc- These are m+st +.ten caused 02 the arcde3el+/ed near the arc- These are m+st +.ten caused 02 the arccurrent gr+und /ath +r in the .i1ture h+lding the /art t+ 0e welded-current gr+und /ath +r in the .i1ture h+lding the /art t+ 0e welded-

The .ields interact with the sel. induced .ield ar+und the electr+de-The .ields interact with the sel. induced .ield ar+und the electr+de-When em/l+2ing "C /+wer the e1ternal .ield will 0e /re.erentiall2 inWhen em/l+2ing "C /+wer the e1ternal .ield will 0e /re.erentiall2 in+ne directi+n- This 0uilds a str+nger .ield +n +ne side +. the arc than+ne directi+n- This 0uilds a str+nger .ield +n +ne side +. the arc thanthe +ther causing it t+ m+3e in the directi+n +. the weakened .ield- Thethe +ther causing it t+ m+3e in the directi+n +. the weakened .ield- Thew+rse situati+n is when this m+3ement causes the arc t+ 0l+ww+rse situati+n is when this m+3ement causes the arc t+ 0l+w0ackwards and 0ec+me unsta0le0ackwards and 0ec+me unsta0le-- ) & When welding with 87, magnetic) & When welding with 87, magneticfields are set up throughout the weldment. %n weldments that ha!e !aryingfields are set up throughout the weldment. %n weldments that ha!e !arying

thickness and protrusions, this magnetic field can affect the arc by makingthickness and protrusions, this magnetic field can affect the arc by makingit stray or fluctuate in direction. 'his condition is especially troublesomeit stray or fluctuate in direction. 'his condition is especially troublesomewhen welding in corners. A7 seldom causes this problem because of thewhen welding in corners. A7 seldom causes this problem because of therapidly re!ersing magnetic field producedrapidly re!ersing magnetic field produced


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When using a 87 power source, the #uestionWhen using a 87 power source, the #uestionof whether to use electrode negati!e orof whether to use electrode negati!e or positi!e polarity arises. Some electrodes positi!e polarity arises. Some electrodesoperate on both 87 straight (W95 ;!e andoperate on both 87 straight (W95 ;!e andelectrode electrode &).electrode &). 8irect current flows in one direction in an8irect current flows in one direction in an

electrical circuit and the direction of currentelectrical circuit and the direction of currentflow and the composition of the electrodeflow and the composition of the electrodecoating will ha!e a definite effect on thecoating will ha!e a definite effect on thewelding arc and weld beadwelding arc and weld bead


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. igure 1 shows the connections and effects. igure 1 shows the connections and effects

of straight and re!erse polarity.of straight and re!erse polarity. lectrode negati!e (&) produces welds withlectrode negati!e (&) produces welds with

shallow penetration= howe!er, the electrodeshallow penetration= howe!er, the electrode

melt&off rate is high. 'he weld bead is rathermelt&off rate is high. 'he weld bead is ratherwide and shallow as shown atwide and shallow as shown at 4A44A4 in igure 1.in igure 1.

lectrode positi!e (


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%*+ 1%*+ 1 "C 'OW! SOC! !$!CTO"! "C 'OW! SOC! !$!CTO"! A"C 'OW! SOC! !$!CTO"! "C 'OW! SOC! !$!CTO"! A

#IG#! N*O%% AT!, $!SS '!N!TATION "!!' '!N!TATION, $OW N*#IG#! N*O%% AT!, $!SS '!N!TATION "!!' '!N!TATION, $OW N*

O%% AT! WO 'I!C! STAIG#T 'O$AIT5 !6!S! 'O$AIT5 WOO%% AT! WO 'I!C! STAIG#T 'O$AIT5 !6!S! 'O$AIT5 WO

'I!C!'I!C!


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'arts +. !lectr+de welding e7ui/ments'arts +. !lectr+de welding e7ui/ments !lectr+de #+lder!lectr+de #+lder & 'he electrode holder connects to the welding cable& 'he electrode holder connects to the welding cable

and conducts the welding current to the electrode. 'he insulated handle isand conducts the welding current to the electrode. 'he insulated handle isused to guide the electrode o!er the weld oint and feed the electrode o!erused to guide the electrode o!er the weld oint and feed the electrode o!erthe weld oint and feed the electrode into the weld puddle as it isthe weld oint and feed the electrode into the weld puddle as it isconsumed. lectrode holders are a!ailable in different si6es and are ratedconsumed. lectrode holders are a!ailable in different si6es and are ratedon their current carrying capacity.on their current carrying capacity.

Gr+und Clam/Gr+und Clam/ & 'he ground clamp is used to connect the ground& 'he ground clamp is used to connect the groundcable to the work piece. %t may be connected directly to the work or to thecable to the work piece. %t may be connected directly to the work or to thetable or fixture upon which the work is positioned. "eing a part of thetable or fixture upon which the work is positioned. "eing a part of the

welding circuit, the ground clamp must be capable of carrying the weldingwelding circuit, the ground clamp must be capable of carrying the weldingcurrent without o!erheating due to electrical resistance.current without o!erheating due to electrical resistance.

Welding Ca0lesWelding Ca0les & 'he electrode cable and the ground cable are& 'he electrode cable and the ground cable areimportant parts of the welding circuit. 'hey must be !ery flexible and ha!eimportant parts of the welding circuit. 'hey must be !ery flexible and ha!ea tough heat&resistant insulation. 7onnections at the electrode holder, thea tough heat&resistant insulation. 7onnections at the electrode holder, theground clamp, and at the power source lugs must be soldered or wellground clamp, and at the power source lugs must be soldered or well

crimped to assure low electrical resistance. 'he cross&sectional area of thecrimped to assure low electrical resistance. 'he cross&sectional area of thecable must be sufficient si6e to carry the welding current with a minimumcable must be sufficient si6e to carry the welding current with a minimumof !oltage drop. %ncreasing the cable length necessitates increasing theof !oltage drop. %ncreasing the cable length necessitates increasing thecable diameter to lessen resistance and !oltage drop.cable diameter to lessen resistance and !oltage drop.


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C+ated !lectr+desC+ated !lectr+des & >arious types of coated& >arious types of coated

electrodes are used in shielded metal arcelectrodes are used in shielded metal arcwelding. lectrodes used for welding mild orwelding. lectrodes used for welding mild or

carbon steels are #uite different than thosecarbon steels are #uite different than those

used for welding the low alloys and stainlessused for welding the low alloys and stainlesssteelssteels


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T2/es +. electr+desT2/es +. electr+des 'here are se!eral types of electrodes that can be used, with different characteristics, and the choice must be'here are se!eral types of electrodes that can be used, with different characteristics, and the choice must be

based on the particular kind of application. based on the particular kind of application.

--. %n particular . %n particular ,, acid electr+desacid electr+des (silica and ir+n silicate)(silica and ir+n silicate) are used when materialsare used when materialswith good weldability are oined (the electrode doesn?t ha!e any depurating effectwith good weldability are oined (the electrode doesn?t ha!e any depurating effectand then the weld is subected to hot cracks) and usually aren?t used for hori6ontaland then the weld is subected to hot cracks) and usually aren?t used for hori6ontalwelding, due to !ery high temperatures reached.welding, due to !ery high temperatures reached.%t produce slags that are predominantly silicon dioxide (sand) and ha!e an acidic%t produce slags that are predominantly silicon dioxide (sand) and ha!e an acidic

beha!ior. Acid slag systems do no refining of the weld metal. beha!ior. Acid slag systems do no refining of the weld metal.

0.8iffuse electrodes are the0.8iffuse electrodes are the cellul+sic +nescellul+sic +nes, that ha!e an high penetration capacity, that ha!e an high penetration capacityand allow a strong proection of material from the electrode to the oint, and aand allow a strong proection of material from the electrode to the oint, and awelding from e!ery positionwelding from e!ery position

- asic electr+des (magnesium and calcium car0+nates- asic electr+des (magnesium and calcium car0+nates) de/urates) de/urates the weldthe weld

oint, due to the reaction of magnesium and calcium with phosphorus and sulphur oint, due to the reaction of magnesium and calcium with phosphorus and sulphurcontained in the metal. 'his kind of electrodes works at relati!ely low temperaturescontained in the metal. 'his kind of electrodes works at relati!ely low temperaturesand are the only that allow an o!erhead welding.and are the only that allow an o!erhead welding.

"asic slags do some refining of the weld metal, resulting in lower nonmetallic"asic slags do some refining of the weld metal, resulting in lower nonmetallicinclusion contentinclusion content


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%uncti+ns +. the c+ating +n c+3ered%uncti+ns +. the c+ating +n c+3ered

electr+deselectr+des a)a) Shielding +. the Weld MetalShielding +. the Weld Metal ; ; 'he most important function of a coating is to'he most important function of a coating is to shield the weld metal fromshield the weld metal from

the oxygen and nitrogen of the air as it is being transferred acrossthe oxygen and nitrogen of the air as it is being transferred across the arc,the arc,and while it is in the molten state. 'his shielding is necessary to ensure theand while it is in the molten state. 'his shielding is necessary to ensure theweld metalweld metal will be sound, free of gas pockets, and ha!e the right strengthwill be sound, free of gas pockets, and ha!e the right strengthand ductility.and ductility.

At the high temperatures of the arc, nitrogen and oxygen combine readilyAt the high temperatures of the arc, nitrogen and oxygen combine readilywith iron to form iron nitrides andwith iron to form iron nitrides and iron oxides that, if present in the weldiron oxides that, if present in the weldmetal abo!e certain minimum amounts, will cause brittleness and porosity.metal abo!e certain minimum amounts, will cause brittleness and porosity.

@itrogen is the primary concern since it is difficult to control its effect once @itrogen is the primary concern since it is difficult to control its effect onceitit has entered the deposit. /xygen can be counteracted by the use ofhas entered the deposit. /xygen can be counteracted by the use ofsuitable deoxidi6ers. %nsuitable deoxidi6ers. %n order to a!oid contamination from the air, theorder to a!oid contamination from the air, thestream of molten metal must be protected or stream of molten metal must be protected or shielded by gases that excludeshielded by gases that excludethe surrounding atmosphere from the arc and the molten weldthe surrounding atmosphere from the arc and the molten weld metal.metal.

'his is accomplished by using gas&forming materials in the coating that'his is accomplished by using gas&forming materials in the coating that break down break down during the welding operation and produce the gaseous shield.during the welding operation and produce the gaseous shield.


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0)Sta0ili8ati+n +. the Arc0)Sta0ili8ati+n +. the Arc & A stabili6ed arc is one that starts& A stabili6ed arc is one that startseasily, burnseasily, burns smoothly e!en at low amperages, and can besmoothly e!en at low amperages, and can bemaintained using either a long or a short arcmaintained using either a long or a short arc length.length.

c)c) All+2ing Additi+ns t+ Weld MetalAll+2ing Additi+ns t+ Weld Metal & A !ariety of elements& A !ariety of elementssuch as chromium,such as chromium, nickel, molybdenum, !anadium and coppernickel, molybdenum, !anadium and coppercan be added to the weld metal by including themcan be added to the weld metal by including them in thein the

coating composition.coating composition.

%t is often necessary to add alloys to the coating to balance the%t is often necessary to add alloys to the coating to balance the expected loss of alloys of the core wire during the weldingexpected loss of alloys of the core wire during the weldingoperation, due to !olati6ation and chemical reaction.operation, due to !olati6ation and chemical reaction.

Mild steel electrodes re#uire small amounts of carbon,Mild steel electrodes re#uire small amounts of carbon,

manganese andmanganese and silicon in the deposit to gi!e sound welds ofsilicon in the deposit to gi!e sound welds ofthe desired strength le!el. A portion of the carbonthe desired strength le!el. A portion of the carbon andandmanganese is deri!ed from the core wire, but it is necessary tomanganese is deri!ed from the core wire, but it is necessary tosupplement it withsupplement it with ferromanganese and in some casesferromanganese and in some casesferrosilicon additions in the coatingferrosilicon additions in the coating


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d)d) C+ncentrati+n +. the Arc StreamC+ncentrati+n +. the Arc Stream & 7oncentration or& 7oncentration ordirection of the arcdirection of the arc stream is attained by ha!ing a coatingstream is attained by ha!ing a coatingcrater (depression) form at the tip of the electrodes. *se of thecrater (depression) form at the tip of the electrodes. *se of the

proper binders assures a good hard coating that will maintain a proper binders assures a good hard coating that will maintain acrater andcrater and gi!e added penetration and better direction to thegi!e added penetration and better direction to thearc stream.arc stream.

%urnish Slag .+r %lu1ing%urnish Slag .+r %lu1ing & 'he function of the slag is& 'he function of the slag is

(-) to pro!ide additional(-) to pro!ide additional protection against atmospheric protection against atmosphericcontamination,contamination,

(0) to act as a cleaner and absorb impurities(0) to act as a cleaner and absorb impurities that are floated offthat are floated offand trapped by the slag,and trapped by the slag,

(1) to slow the cooling rate of the molten metal to(1) to slow the cooling rate of the molten metal to allow theallow theescape of gases.escape of gases.

'he slag also controls the contour, uniformity and general'he slag also controls the contour, uniformity and generalappearance of the weldappearance of the weld


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f)f) Characteristics .+r Welding '+siti+nCharacteristics .+r Welding '+siti+n & %t is the addition of& %t is the addition ofcertain ingredients,certain ingredients, primarily titanium compounds, in the primarily titanium compounds, in thecoating that makes it possible to weld out&of&position ,coating that makes it possible to weld out&of&position ,

!ertically, and o!erhead.!ertically, and o!erhead. Slag characteristics, primarily surface tension and free6ingSlag characteristics, primarily surface tension and free6ing

point, point, determine to a large degree the ability of an electrode todetermine to a large degree the ability of an electrode to be used for out&of&position work. be used for out&of&position work.

C+ntr+l +. Weld Metal S+undnessC+ntr+l +. Weld Metal S+undness ; ; 5orosity or gas pockets in weld metal5orosity or gas pockets in weld metal can be controlled to acan be controlled to a

large extent by the coating composition. %t is the balance oflarge extent by the coating composition. %t is the balance ofcertaincertain ingredients in the coating that ha!e a marked effect oningredients in the coating that ha!e a marked effect onthe presence of gas pockets in thethe presence of gas pockets in the weld metal.weld metal.

'he proper balance of these is critical to the soundness that can'he proper balance of these is critical to the soundness that can be produced. be produced. erromanganese is probably the most commonerromanganese is probably the most commoningredient used to attain the correctly balanced formula.ingredient used to attain the correctly balanced formula.


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h)h) S/eci.ic Mechanical 'r+/erties t+ the WeldS/eci.ic Mechanical 'r+/erties t+ the Weld

MetalMetal & Specific mechanical& Specific mechanical properties can be properties can beincorporated into the weld metal by means of theincorporated into the weld metal by means of the

coating. igh impactcoating. igh impact !alues at low temperature, high!alues at low temperature, high

ductility, and increases in yield and tensile propertiesductility, and increases in yield and tensile properties

can becan be attained by alloy additions to the coating.attained by alloy additions to the coating. i)i) Insulati+n +. the C+re WireInsulati+n +. the C+re Wire & 'he coating acts as& 'he coating acts as

an insulator so that the corean insulator so that the core wire will not short&circuitwire will not short&circuit

when welding in deep groo!es or narrow openings=when welding in deep groo!es or narrow openings=

coatings alsocoatings also ser!e as a protection to the operatorser!e as a protection to the operator

when changing electrodeswhen changing electrodes


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"isad3antage"isad3antage

'he weld oxidation and to impurity inclusion, that'he weld oxidation and to impurity inclusion, that

worsened structural performance of the welded oint.worsened structural performance of the welded oint.to resol!e these problems, nowadays electrodes areto resol!e these problems, nowadays electrodes areco!ered with appropriate deoxidi6ing agents, thatco!ered with appropriate deoxidi6ing agents, thatincrease welded oint characteristics.increase welded oint characteristics.

When the operation is finished, the weld needs to beWhen the operation is finished, the weld needs to bechiseled, in order to remo!e scrap that forms duringchiseled, in order to remo!e scrap that forms duringwelding.welding.

'he manual character of this process, and the need for'he manual character of this process, and the need forconsumable electrode substitution, decrease theconsumable electrode substitution, decrease the

production rate of this process production rate of this process


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'ungsten inert gas ('%) welding'ungsten inert gas ('%) welding

Gas tungsten arc weldingGas tungsten arc welding ((GTAWGTAW), also known as), also known as tungstentungsteninert gas (TIG) weldinginert gas (TIG) welding, is an, is an arc weldingarc welding process that uses a process that uses anonconsumablenonconsumable tungstentungsten electrodeelectrode to produce theto produce the weldweld..

'he weld area is protected from atmospheric contamination by'he weld area is protected from atmospheric contamination by

a shielding gas (usually an inert gas such as argon), and a fillera shielding gas (usually an inert gas such as argon), and a fillermetal is normally used, though some welds, known asmetal is normally used, though some welds, known asautogenous welds, do not re#uire it.autogenous welds, do not re#uire it.

A constant&current welding power supply produces energyA constant&current welding power supply produces energywhich is conducted across the arc through a column of highlywhich is conducted across the arc through a column of highlyioni6ed gas and metal !apors known as a plasma.ioni6ed gas and metal !apors known as a plasma.

http://en.wikipedia.org/wiki/Arc_weldinghttp://en.wikipedia.org/wiki/Arc_weldinghttp://en.wikipedia.org/wiki/Tungstenhttp://en.wikipedia.org/wiki/Tungstenhttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Weldinghttp://en.wikipedia.org/wiki/Weldinghttp://en.wikipedia.org/wiki/Weldinghttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Tungstenhttp://en.wikipedia.org/wiki/Arc_welding


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'AW is most commonly used to weld thin sections'AW is most commonly used to weld thin sectionsof stainless steel and light metals such as aluminum,of stainless steel and light metals such as aluminum,magnesium, and copper alloys.magnesium, and copper alloys.

'he process grants the operator greater control o!er'he process grants the operator greater control o!erthe weld than competing procedures such as shieldedthe weld than competing procedures such as shieldedmetal arc welding and gas metal arc welding,metal arc welding and gas metal arc welding,allowing for stronger, higher #uality welds.allowing for stronger, higher #uality welds.

owe!er, 'AW is comparati!ely more complex andowe!er, 'AW is comparati!ely more complex anddifficult to master, and furthermore, it is significantlydifficult to master, and furthermore, it is significantlyslower than most other welding techni#uesslower than most other welding techni#ues


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as tungsten arc welding producesas tungsten arc welding produces exceptionally clean weldsexceptionally clean welds no slag is produced,no slag is produced,the chance inclusions in the weld metal is and the finished weld re#uires !irtuallythe chance inclusions in the weld metal is and the finished weld re#uires !irtuallyno cleaning.no cleaning.

Argon and elium, the primary shielding gasesArgon and elium, the primary shielding gases employed, are inert gases. %nertemployed, are inert gases. %nertgases do not chemically combine with other elements and therefore, are used togases do not chemically combine with other elements and therefore, are used toexclude the reacti!e gases, such as oxygen and nitrogen, from forming compoundsexclude the reacti!e gases, such as oxygen and nitrogen, from forming compoundsthat could be detrimental to the weld metal.that could be detrimental to the weld metal.

as tungsten arc welding may be used for welding almost all metalsas tungsten arc welding may be used for welding almost all metals B mild steel, B mild steel,low alloys, stainless steel, copper and copper alloys, aluminum and aluminumlow alloys, stainless steel, copper and copper alloys, aluminum and aluminum

alloys, nickel and nickel alloys, magnesium and magnesium alloys, titanium, andalloys, nickel and nickel alloys, magnesium and magnesium alloys, titanium, andothers. 'his process is most extensi!ely used for welding aluminum and stainlessothers. 'his process is most extensi!ely used for welding aluminum and stainlesssteel alloys where weld integrity is of the utmost importance.steel alloys where weld integrity is of the utmost importance.

Another use is for the root pass (initial pass) in pipe welding, which re#uires aAnother use is for the root pass (initial pass) in pipe welding, which re#uires aweld of the highest #uality. ull penetration without an excessi!ely high insideweld of the highest #uality. ull penetration without an excessi!ely high inside bead is important in the root pass, and due to the ease of current control of this bead is important in the root pass, and due to the ease of current control of this process, it lends itself to control of back&bead si6e. process, it lends itself to control of back&bead si6e.

or high #uality welds, it is usually necessary to pro!ide an inert shielding gasor high #uality welds, it is usually necessary to pro!ide an inert shielding gasinside the pipe to pre!ent oxidation of the inside weld bead.inside the pipe to pre!ent oxidation of the inside weld bead. 99 as 'ungsten Arcas 'ungsten ArcWelding ('AW) is the current terminology appro!ed by the American WeldingWelding ('AW) is the current terminology appro!ed by the American WeldingSociety, formerly known as C'%C ('ungsten %nert as) welding.Society, formerly known as C'%C ('ungsten %nert as) welding.


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!:I'M!NT AN" O'!ATION!:I'M!NT AN" O'!ATION & as tungsten arc& as tungsten arcwelding may be accomplished with relati!ely simplewelding may be accomplished with relati!ely simple

e#uipment, or it may re#uire some highly sophisticatede#uipment, or it may re#uire some highly sophisticatedcomponents. 7hoice of e#uipment depends upon the type ofcomponents. 7hoice of e#uipment depends upon the type ofmetal being oined, the position of the weld being made, andmetal being oined, the position of the weld being made, andthe #uality of the weld metal necessary for the application.the #uality of the weld metal necessary for the application.'he basic e#uip& ment consists of the following:'he basic e#uip& ment consists of the following:

-. 'he power source-. 'he power source 0. lectrode holder (torch)0. lectrode holder (torch) 1. Shielding gas1. Shielding gas 2. 'ungsten electrode2. 'ungsten electrode 3. Water supply when necessary3. Water supply when necessary 4. round cable4. round cable D. 5rotecti!e e#uipmentD. 5rotecti!e e#uipment


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AS '*@S'@ A+7 WE8%@AS '*@S'@ A+7 WE8%@

7/@@7'%/@ S7MA'%77/@@7'%/@ S7MA'%7

..


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'+wer S+urces'+wer S+urces & "oth A7 and 87 power sources are used in& "oth A7 and 87 power sources are used ingas tungsten arc welding. 'hey are the constant current typegas tungsten arc welding. 'hey are the constant current type

with a drooping !olt&ampere cur!e.with a drooping !olt&ampere cur!e. "irect current electr+de negati3e ("C!N)"irect current electr+de negati3e ("C!N) is produced whenis produced when

the electrode is connected to the negati!e terminal of thethe electrode is connected to the negati!e terminal of the power source. power source.

Since the electrons flow from the electrode to the plate,Since the electrons flow from the electrode to the plate,

approximately DFG of the heat of the arc is concentrated at theapproximately DFG of the heat of the arc is concentrated at thework, and approximately 1FG at the electrode end.work, and approximately 1FG at the electrode end.

'his allows the use of smaller tungsten elec& trodes that'his allows the use of smaller tungsten elec& trodes that produce a relati!ely narrow concentrated arc. 'he weld shape produce a relati!ely narrow concentrated arc. 'he weld shapehas deep penetration and is #uite narrow.has deep penetration and is #uite narrow.

8irect current electrode negati!e is suitable for welding most8irect current electrode negati!e is suitable for welding mostmetals. Magnesium and aluminum ha!e a refractory oxidemetals. Magnesium and aluminum ha!e a refractory oxidecoating on the surface that must be physically remo!edcoating on the surface that must be physically remo!edimmediately prior to welding if 87S5 is to be usedimmediately prior to welding if 87S5 is to be used


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"irect current electr+de /+siti3e ("C!')"irect current electr+de /+siti3e ("C!') isis

produced when the electrode is connected to the produced when the electrode is connected to the positi!e terminal of the welding power source. positi!e terminal of the welding power source. %n this condition, the electrons flow from the work%n this condition, the electrons flow from the work

to the electrode tip, concentrating approximately DFGto the electrode tip, concentrating approximately DFGof the heat of the arc at the electrode and 1FG at theof the heat of the arc at the electrode and 1FG at thework.work.

'his higher heat at the electrode necessitates using'his higher heat at the electrode necessitates usinglarger diameter tungsten to pre!ent it from meltinglarger diameter tungsten to pre!ent it from meltingand contaminating the weld metal.and contaminating the weld metal.

Since the electrode diameter is larger and the heat isSince the electrode diameter is larger and the heat isless concentrated at the work, the resultant weld beadless concentrated at the work, the resultant weld beadis relati!ely wide and shallow.is relati!ely wide and shallow.


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Aluminum and magnesium are two metals that ha!e a hea!yAluminum and magnesium are two metals that ha!e a hea!y

oxide coating that acts as an insulator and must be remo!edoxide coating that acts as an insulator and must be remo!ed before successful welding can take place. before successful welding can take place. Welding with electrode positi!e pro!ides a good oxideWelding with electrode positi!e pro!ides a good oxide

cleaning action in the arc. %f we were to study the physics ofcleaning action in the arc. %f we were to study the physics ofthe welding arc, we find that the electric current causes thethe welding arc, we find that the electric current causes the

shielding gas atoms to lose some of their electrons. Sinceshielding gas atoms to lose some of their electrons. Sinceelectrons are negati!ely charged, these gas atoms now areelectrons are negati!ely charged, these gas atoms now areunbalanced and ha!e an excessi!e positi!e charge.*ponunbalanced and ha!e an excessi!e positi!e charge.*ponstriking the work surface, they dislodge the oxide coatingstriking the work surface, they dislodge the oxide coating

permitting good electrical permitting good electrical conducti!ity for the maintenance ofconducti!ity for the maintenance of

the arc, and eliminate the impurities in the weld metal thatthe arc, and eliminate the impurities in the weld metal that could be caused by these oxides.could be caused by these oxides.


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"irect current electr+de /+siti3e"irect current electr+de /+siti3e is rarelyis rarely

used in gas&tungsten arc welding. 8espiteused in gas&tungsten arc welding. 8espite thetheexcellent oxide cleaning action, the lower heatexcellent oxide cleaning action, the lower heat

input in the weld area makes it a slowinput in the weld area makes it a slow process, process,

and in metals ha!ing higher thermaland in metals ha!ing higher thermal

conducti!ity, the heat is rapidly conductedconducti!ity, the heat is rapidly conducted

awayaway from the weld 6one. When used, 875from the weld 6one. When used, 875

is restricted to welding thin sections (underis restricted to welding thin sections (under

-9HC) of -9HC) of magnesium and aluminummagnesium and aluminum


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Alternating currentAlternating current is actually a combination of 87@ andis actually a combination of 87@ and875 and is widely875 and is widely used for welding aluminum.used for welding aluminum.

%n a sense, the ad!antages of both 87 processes are combined,%n a sense, the ad!antages of both 87 processes are combined, and the weld bead produced is a compromise of the two.and the weld bead produced is a compromise of the two.+emember that when welding with+emember that when welding with 4F 6 current, the electron4F 6 current, the electron

flow from the electrode tip to the work re!erses direction -0Fflow from the electrode tip to the work re!erses direction -0Ftimestimes e!ery second. 'hereby, the intense heat alternates frome!ery second. 'hereby, the intense heat alternates fromelectrode to work piece, allowing theelectrode to work piece, allowing the use of an intermediateuse of an intermediatesi6e electrode.si6e electrode.

'he weld bead is a compromise ha!ing medium'he weld bead is a compromise ha!ing medium penetration penetrationand bead width. 'he gas ions blast the oxides from the surfaceand bead width. 'he gas ions blast the oxides from the surface

of aluminum andof aluminum and magnesium during the positi!e half cycle.magnesium during the positi!e half cycle.


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"C c+nstant current /+wer s+urces"C c+nstant current /+wer s+urces ; ; 7onstant current power sources, used for 7onstant current power sources, used for shielded metal arc welding, mayshielded metal arc welding, may

also be used for gas&tungsten arc welding. %n applicationsalso be used for gas&tungsten arc welding. %n applications

where weldwhere weld

integrity is not of utmost importance, these power sources will suffice.integrity is not of utmost importance, these power sources will suffice.WithWith machines of this type, the arc must be initiated by touching themachines of this type, the arc must be initiated by touching thetungsten electrode to the work tungsten electrode to the work and #uickly withdrawing it to maintain theand #uickly withdrawing it to maintain the

proper arc length. proper arc length. 'his starting method'his starting method contaminates the electrode and blunts the pointcontaminates the electrode and blunts the point

which has been grounded on the electrodewhich has been grounded on the electrode end. 'hese conditions can causeend. 'hese conditions can cause

weld metal inclusions and poor arc direction.weld metal inclusions and poor arc direction. *sing a*sing a power source designed for gas tungsten arc welding with a power source designed for gas tungsten arc welding with a highhigh

fre#uency stabili6er fre#uency stabili6er willwill eliminate this problem. 'he electrode need not beeliminate this problem. 'he electrode need not betouched to the work for arc initiation.touched to the work for arc initiation. %nstead, the high fre#uency !oltage,%nstead, the high fre#uency !oltage,at !ery low current, is superimposed onto the weldingat !ery low current, is superimposed onto the welding current. When thecurrent. When theelectrode is brought to within approximately -9H inch of the base metal, theelectrode is brought to within approximately -9H inch of the base metal, the

high fre#uency ioni6es the gas path, making it conducti!e and a weldinghigh fre#uency ioni6es the gas path, making it conducti!e and a weldingarc is established.arc is established. 'he high fre#uency is automatically turned off'he high fre#uency is automatically turned offimmediately after arc initiation when using directimmediately after arc initiation when using direct currentcurrent


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T+rchesT+rches & 'he torch is actually an electrode holder that supplies welding& 'he torch is actually an electrode holder that supplies weldingcurrent to the tungsten electrode, and an inert gas shield to the arc 6one.current to the tungsten electrode, and an inert gas shield to the arc 6one.

'he electrode is held in a collet&like clamping de!ice that allows'he electrode is held in a collet&like clamping de!ice that allowsadustment so that the proper length of electrode pro& trudes beyond theadustment so that the proper length of electrode pro& trudes beyond theshielding gas cup. 'orches may be either air or water&cooled.shielding gas cup. 'orches may be either air or water&cooled.

'he air&cooled types actually are cooled to a degree by the shielding gas'he air&cooled types actually are cooled to a degree by the shielding gasthat is fed to the torch head through a composite cable.that is fed to the torch head through a composite cable.

'he gas actually surrounds the copper welding cable, affording some'he gas actually surrounds the copper welding cable, affording some

degree of cooling.degree of cooling.

Water&cooled torches are usually used for applications where the weldingWater&cooled torches are usually used for applications where the weldingcurrent exceeds 0FF amperes.current exceeds 0FF amperes.

'he water inlet hose is connected to the torch head. 7irculating around the'he water inlet hose is connected to the torch head. 7irculating around thetorch head, the water lea!es the torch !ia the current&in hose and cabletorch head, the water lea!es the torch !ia the current&in hose and cableassembly.assembly.

7ooling the welding cable in this manner allows the use of a smaller7ooling the welding cable in this manner allows the use of a smallerdiameter cable that is more flexible and lighter in weightdiameter cable that is more flexible and lighter in weight


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%n %nert gas shielded arc welding processes,a%n %nert gas shielded arc welding processes,a

high presssureinert gas flowing around thehigh presssureinert gas flowing around the

electrode while welding would physicaalyelectrode while welding would physicaaly

displace all the atmospheric gases around thedisplace all the atmospheric gases around the

weld metal to fully protect it.weld metal to fully protect it.


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Shielding GasesShielding Gases & Argon and helium are the maor shielding gases used in gas tungsten arc& Argon and helium are the maor shielding gases used in gas tungsten arcwelding. %n some applications, mixtures of the two gases pro!e ad!antageous. 'o a lesserwelding. %n some applications, mixtures of the two gases pro!e ad!antageous. 'o a lesser

extent, hydrogen is mixed with argon or helium for special applications.extent, hydrogen is mixed with argon or helium for special applications.

0.1.2.-0.1.2.- Argon and heliumArgon and helium are colorless, odorless, tasteless and nontoxic gases. "oth are inertare colorless, odorless, tasteless and nontoxic gases. "oth are inertgases, which means that they do not readily combine with other elements. 'hey will not burngases, which means that they do not readily combine with other elements. 'hey will not burnnor support combustion. 7ommercial grades used for welding are II.IIG pure.nor support combustion. 7ommercial grades used for welding are II.IIG pure.

ArgonArgon is 1HG hea!ier than air and about -F times hea!ier than helium. "oth gases ioni6eis 1HG hea!ier than air and about -F times hea!ier than helium. "oth gases ioni6ewhen present in an electric arc. 'his means that the gas atoms lose some of their electrons thatwhen present in an electric arc. 'his means that the gas atoms lose some of their electrons thatha!e a negati!e charge. 'hese unbalanced gas atoms, properly called positi!e ions, now ha!eha!e a negati!e charge. 'hese unbalanced gas atoms, properly called positi!e ions, now ha!ea positi!e charge and are attracted to the negati!e pole in the arc. When the arc is positi!e anda positi!e charge and are attracted to the negati!e pole in the arc. When the arc is positi!e and

the work is negati!e, these positi!e ions impinge upon the work and remo!e surface oxides orthe work is negati!e, these positi!e ions impinge upon the work and remo!e surface oxides orscale in the weld area.scale in the weld area. Argon is most commonly used of the shielding gases. xcellent arc starting and ease of useArgon is most commonly used of the shielding gases. xcellent arc starting and ease of use

make it most desirable for manual welding.make it most desirable for manual welding. Argon produces a better cleaning action when welding aluminum and magnesium withArgon produces a better cleaning action when welding aluminum and magnesium with

alternating current.alternating current. 'he arc produced is relati!ely narrow.'he arc produced is relati!ely narrow.

Argon is more suitable for welding thinner material and for out of position weldingArgon is more suitable for welding thinner material and for out of position welding ea!iest of all shielding gases hence re#uire lower flow rate for good shielding action.ea!iest of all shielding gases hence re#uire lower flow rate for good shielding action. At e#ual amperage, helium produces a higher arc !oltage than argonAt e#ual amperage, helium produces a higher arc !oltage than argon


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Argon&heliumArgon&helium gas mixtures are used in applications wheregas mixtures are used in applications wherehigher heat input and the desirable characteristics of argon arehigher heat input and the desirable characteristics of argon are

re#uired.re#uired. Argon, being a relati!ely hea!y gas, blankets the weld area atArgon, being a relati!ely hea!y gas, blankets the weld area at

lower flow rates. Argon is preferred for many applicationslower flow rates. Argon is preferred for many applications because it costs less than helium. because it costs less than helium.

eliumelium

elium has higher thermal conducti!ity so it gi!eselium has higher thermal conducti!ity so it gi!es

higher arc !oltage for gi!en current nad higher heat input.higher arc !oltage for gi!en current nad higher heat input. being approximately -F times lighter than argon, re#uires flow being approximately -F times lighter than argon, re#uires flow

rates of 0 to 1 times that of argon to satisfactorily shield therates of 0 to 1 times that of argon to satisfactorily shield thearc. elium rises in turbulent manner and tends to dispersearc. elium rises in turbulent manner and tends to disperse

into air.So higher flow rate will be re#uired.into air.So higher flow rate will be re#uired. %t can withstand higher arc !oltages and hence used for%t can withstand higher arc !oltages and hence used for

welding where higher heat input is re#uiredsuch as for thickwelding where higher heat input is re#uiredsuch as for thicksheets or higher conducti!ity materials as 7u and Al.sheets or higher conducti!ity materials as 7u and Al.


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Argon


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!lectr+des!lectr+des & lectrodes for gas tungsten arc welding are a!ailable in& lectrodes for gas tungsten arc welding are a!ailable indiameters from .F-FC to -92C in diameter and standard lengths range fromdiameters from .F-FC to -92C in diameter and standard lengths range from1C to 02C. 'he most commonly used si6es, howe!er, are the .F2FC, -9-4C,1C to 02C. 'he most commonly used si6es, howe!er, are the .F2FC, -9-4C,

1910C, and -9HC diameters.1910C, and -9HC diameters. 'he'he shape of the tip of the electrodeshape of the tip of the electrode is an important factor in gas tungstenis an important factor in gas tungsten

arc welding. When welding with 87@, the tip must be ground to a point.arc welding. When welding with 87@, the tip must be ground to a point. 'he included angle at which the tip is ground !aries with'he included angle at which the tip is ground !aries with the application,the application, the electrode diameter, andthe electrode diameter, and the welding current.the welding current. @arrow oints re#uire a relati!ely small included angle. When welding @arrow oints re#uire a relati!ely small included angle. When welding

!ery thin material at low currents, a needlelike point ground onto the!ery thin material at low currents, a needlelike point ground onto thesmallest a!ailable electrode may be necessary to stabili6e the arc.smallest a!ailable electrode may be necessary to stabili6e the arc.

5roperly ground electrodes will assure easy arc starting, good arc stability,5roperly ground electrodes will assure easy arc starting, good arc stability,

and proper bead width.and proper bead width.


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T2/es +. !lectr+desT2/es +. !lectr+des

-)-) 'ure Tungsten (AWS !W')'ure Tungsten (AWS !W') Color Code:Color Code:GreenGreen

*sed for less critical applications. 'he cost is low*sed for less critical applications. 'he cost is low

and they gi!e good results at relati!ely low currentsand they gi!e good results at relati!ely low currentson a !ariety of metals.on a !ariety of metals. Most stable arc when used on A7, either balancedMost stable arc when used on A7, either balanced

wa!e or continuous high fre#uency.wa!e or continuous high fre#uency.

5ure 'i electrodes are usually preferred for A75ure 'i electrodes are usually preferred for A7welding of Al and Mg. 'he current carrying capacitywelding of Al and Mg. 'he current carrying capacityis lower than alloyed electrode.is lower than alloyed electrode.


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;< Th+riated Tungsten (AWS !WTh*;);< Th+riated Tungsten (AWS !WTh*;) Color Code: YellowColor Code: Yellow ood current carrying capacity, easy arc starting ,longer life and pro!ide a stableood current carrying capacity, easy arc starting ,longer life and pro!ide a stable

arc.arc. Eess susceptible to contamination. 8esigned for 87 applications of nonferrousEess susceptible to contamination. 8esigned for 87 applications of nonferrous

materials.materials. 1)1) =< Th+riated Tungsten (AWS !WTh*=)=< Th+riated Tungsten (AWS !WTh*=) Color Code: Red Color Code: Red Eonger life than -G 'horiated electrodes. Maintain the pointed end longer, usedEonger life than -G 'horiated electrodes. Maintain the pointed end longer, used

for light gauge critical welds in aircraft work. Eike -G, designed for 87for light gauge critical welds in aircraft work. Eike -G, designed for 87applications for nonferrous materials.applications for nonferrous materials.

2)2) >< Th+riated Tungsten (AWS !WTh*)>< Th+riated Tungsten (AWS !WTh*) Color Code: BlueColor Code: Blue SometimesSometimescalled CstripedC electrode because it has -.F&0.FG 'horia inserted in a wedge&called CstripedC electrode because it has -.F&0.FG 'horia inserted in a wedge&shaped groo!e throughout its length. 7ombines the good properties of pure andshaped groo!e throughout its length. 7ombines the good properties of pure andthoriated electrodes. 7an be used on either A7 or 87 applications.thoriated electrodes. 7an be used on either A7 or 87 applications.

3)3) ?irc+nia Tungsten (AWS !W?r)?irc+nia Tungsten (AWS !W?r) Color Code: BrownColor Code: Brown Eonger life than pure tungsten. "etter performance when welding with A7. MeltsEonger life than pure tungsten. "etter performance when welding with A7. Melts

more easily than thoriam&tungsten when forming rounded or tapered tungsten end.more easily than thoriam&tungsten when forming rounded or tapered tungsten end. %deal for applications where tungsten contamination must be minimi6ed.%deal for applications where tungsten contamination must be minimi6ed. ood arc starting characteristics.ood arc starting characteristics.


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'he current carrying capacity of electrode'he current carrying capacity of electrode

depends on:depends on:

Shielding gas usedShielding gas used

Eength of electrodeEength of electrode

7ooling of the holders7ooling of the holders 5osition of weld type5osition of weld type


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as 'ungsten Arc Welding is one of the maor welding processes today.as 'ungsten Arc Welding is one of the maor welding processes today. 'he #uality of the welds produced and the ability to weld !ery thin metals'he #uality of the welds produced and the ability to weld !ery thin metals

are the maor features.are the maor features. 'he weld metal #uality is high since no flux is used, eliminating the'he weld metal #uality is high since no flux is used, eliminating the

problem of slag inclusions in the weld metal. problem of slag inclusions in the weld metal. %t is used extensi!ely in the aircraft and aerospace industry, where high%t is used extensi!ely in the aircraft and aerospace industry, where high

#uality welds are necessary and also for welding the more expensi!e#uality welds are necessary and also for welding the more expensi!emetals where the weld defects become !ery costly.metals where the weld defects become !ery costly.

Metals as thin as .FF3C can be welded due to the ease of controlling theMetals as thin as .FF3C can be welded due to the ease of controlling thecurrent. 0.1.4.-current. 0.1.4.-

'he maor disad!antages of the process are that'he maor disad!antages of the process are that it is slower than welding with consumable electrodes and is little used onit is slower than welding with consumable electrodes and is little used on

thicknesses o!er -92C for this reason.thicknesses o!er -92C for this reason. Shielding gas and tungsten electrode costs make the process relati!elyShielding gas and tungsten electrode costs make the process relati!ely

expensi!eexpensi!e


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Documents

#Ele#Ctrode Welding