experimental study of gas tungstun arc welding process paramenets

8/13/2019 Experimental study of gas tungstun arc welding process paramenets

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DEVELOPMENT OF MATHEMATICAL MODEL ON GAS

TUNGSTEN ARC WELDING PROCESS

1K.ASHOK KUMAR, 2G. SATISH, 3V.LAKSHMI NARAYANA

1, 2, 3 Department ! Me"#an$"a% En&$neer$n&,S#r$ V$'#n( En&$neer$n& C%%e&e !r Wmen, )NTU*,

+#$maaram-.3/202, An#ra Prae'#, In$a

ashokkumark@sve!.e"u.#$, sa%#sh&@sve!.e"u.#$,'akshm#$ara(a$av@sve!.e"u.#$

A)STRA*T +

GAS TUNGSTEN ARC WELDING (GTAW) is the quality weld proess! It is pre"erred weldi#$ proess "or

stai#less steel% low alloy steel% #i&el% o'alt% tita#iu% alui#u% opper% a#d a$#esiu! The prese#t wor&

ais to ealuate the e""et o" Gas Tu#$ste# Ar Weldi#$ proess paraeters o# the quality o" the weld 'ead!

The proess paraeters Weldi#$ Curre#t% Wire Diaeter% Wire *eed Speed% Ratio o" wire "eed rate to trael

speed a#d +late thiess are ta&e# as a i#put aria'les "or this prese#t wor&! The quality o" the weld 'ead a#

'e assessed 'y the 'ead harateristis suh as +e#etratio#% Rei#"oree#t , Width! E-perie#ts wereo#duted to study the e""ets o" the weldi#$ proess paraeters! Statistially desi$#ed e-perie#ts with .

proess paraeters (eah at / leels) are o#duted to study the e""et o" these paraeters o# 'ead $eoetry! It

is "ou#d "ro the a#alysis o" aria#e (AN01A) that the wire "eed rate% trael speed a#d wire diaeter are the

ai# paraeters that i#"lue#e 'ead $eoetry i# GTAW! 2atheatial odels are deeloped "or depth o"

pe#etratio#% rei#"oree#t hei$ht a#d 'ead width "or GTAW usi#$ the ultiple re$ressio# a#alysis!

KY -ORS 3 GTAW% Data*it ersio# 4!5!.4% I% D% W*R% TS% +T!

1 Intr("t$n

Gas tungsten arc welding (GTAW), also

known as tungsten inert gas (TIG) welding, is an arcwelding process that uses a non-consumable tungsten

electrodeto produce theweld.The weld area is protectedfrom atmospheric contamination b a shielding gas

(usuall an inert gassuch as argon), and afiller metalis

normall used, though some welds, known asautogenous welds, do not re!uire it. A constant-current

welding power suppl produces energ which is

conducted across the arc through a column of highlioni"ed gas and metal #apors known as aplasma.

GTAW process is a candidate welding process,as it produces high !ualit and consistent welds and

pro#ides e$cellent control of heat input. The GTAWprocess uses a non-consumable electrode protected b an

inert gas. As this process uses a non-consumable

electrode, e$tra material, if re!uired, is added through afiller wire either manuall or using a wire feeder.

GTAW is most commonl used to weld thin

sections of stainless steeland non-ferrous metals such asaluminum, magnesium, and copperallos. The process

grants the operator greater control o#er the weld thancompeting procedures such as shielded metal arc

welding and gas metal arc welding, allowing forstronger, higher !ualit welds. %owe#er, it is

comparati#el more comple$ and difficult to master, and

furthermore, it is significantl slower than most otherwelding techni!ues. A related process, plasma arc

welding, uses a slightl different welding torch to create

a more focused welding arc and as a result is oftenautomated. . TIG welding has become a popular choice

of welding processes when high !ualit, precisionwelding is re!uired.

GTAW is fre!uentl referred to as TIGwelding. TIG welding is a commonl used high !ualit

welding process. TIG welding has become a popularchoice of welding processes when high !ualit, precision

welding is re!uired.

In TIG welding an arc is formed between anon-consumable tungsten electrode and the metal being

welded. Gas is fed through the torch to shield the

electrode and molten weld pool. If filler wire is used, itis added to the weld pool separatel.

&igure ' GTAW stem setupThe weld-bead formed b the GTAW process

plas an important role in determining the mechanicalproperties of the weld and its !ualit. The weld-bead

geometr also directl affects the comple$it of weld
mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]://en.wikipedia.org/wiki/Arc_weldinghttp://en.wikipedia.org/wiki/Arc_weldinghttp://en.wikipedia.org/wiki/Tungstenhttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Weldinghttp://en.wikipedia.org/wiki/Weldinghttp://en.wikipedia.org/wiki/Weldinghttp://en.wikipedia.org/wiki/Shielding_gashttp://en.wikipedia.org/wiki/Inert_gashttp://en.wikipedia.org/wiki/Argonhttp://en.wikipedia.org/wiki/Filler_metalhttp://en.wikipedia.org/wiki/Filler_metalhttp://en.wikipedia.org/wiki/Filler_metalhttp://en.wikipedia.org/wiki/Welding_power_supplyhttp://en.wikipedia.org/wiki/Welding_power_supplyhttp://en.wikipedia.org/wiki/Plasma_(physics)http://en.wikipedia.org/wiki/Plasma_(physics)http://en.wikipedia.org/wiki/Plasma_(physics)http://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Aluminumhttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Shielded_metal_arc_weldinghttp://en.wikipedia.org/wiki/Shielded_metal_arc_weldinghttp://en.wikipedia.org/wiki/Shielded_metal_arc_weldinghttp://en.wikipedia.org/wiki/Gas_metal_arc_weldinghttp://en.wikipedia.org/wiki/Plasma_arc_weldinghttp://en.wikipedia.org/wiki/Plasma_arc_weldingmailto:[email protected]:[email protected]:[email protected]://en.wikipedia.org/wiki/Arc_weldinghttp://en.wikipedia.org/wiki/Arc_weldinghttp://en.wikipedia.org/wiki/Tungstenhttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Weldinghttp://en.wikipedia.org/wiki/Shielding_gashttp://en.wikipedia.org/wiki/Inert_gashttp://en.wikipedia.org/wiki/Argonhttp://en.wikipedia.org/wiki/Filler_metalhttp://en.wikipedia.org/wiki/Welding_power_supplyhttp://en.wikipedia.org/wiki/Plasma_(physics)http://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Aluminumhttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Shielded_metal_arc_weldinghttp://en.wikipedia.org/wiki/Shielded_metal_arc_weldinghttp://en.wikipedia.org/wiki/Gas_metal_arc_weldinghttp://en.wikipedia.org/wiki/Plasma_arc_weldinghttp://en.wikipedia.org/wiki/Plasma_arc_welding


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schedules. The weld-bead shape parameters such as thebead width, reinforcement height and depth of

penetration, shown in &igure , are determined b theGTAW process parameters such as current, #oltage,

welding speed and wire feed rate.

&igure Weld bead geometr

2 Stat$'t$"a% e'$&n ! eper$ment' an

TAGUCHI met#

A designed e$periment is the simultaneouse#aluation of two or more factors (parameters) for their

abilit to affect the resultant a#erage or #ariabilit of

particular product or process characteristics. Toaccomplish this in an effecti#e and statisticall proper

fashion, the le#els of the factors are #aried in a strategicmanner, the results of the particular test combinations are

obser#ed, and the complete set of results is anal"ed todetermine the important factors and preferred le#els, and

to find whether increase or decrease of those le#els willpotentiall lead to further impro#ement. The initial

e$periments, often referred to as screening e$periments,are used to find the few important, significant factors out

of man possible factors in#ol#ed with a product orprocess design. This e$periment is tpicall a small

e$periment with man factors at two le#els. *ater rounds

of e$periments tpicall in#ol#e few factors at morethan two le#els to determine conditions of furtherimpro#ement.

21 T#e p#a'e' $n e'$&n ! eper$ment'

The design of e$periments (+) process is

di#ided into three main phases as (') the planning phase

() the conducting phase () the analses phase.The planning phase is b far the most

important phase for the e$periment to pro#ide thee$pected information. An e$perimenter will learn the

information from an e$periment, sometimes in apositi#e sense and sometimes in a negati#e sense.

/ositi#e information is an indication of which factorsand which le#els lead to impro#ed product or process

performance. 0egati#e information is an indication ofwhich factors don1t lead to impro#ement, but no

indication of which factors do. If the e$perimentincludes the real, et unknown, influential factors, the

e$periment will ield negati#e information. In theplanning phase factors and le#els are selected and,

therefore, it is the most important stage ofe$perimentation. Also, the correct selection of factors

and le#els is nonstatistical in nature and is moredependent upon product and process e$pertise.

The second most important phase is the

conducting phase, where test results are actuallcollected. If e$periments are well planned and

conducted, the analsis is much easier and more likel toield positi#e information about factors and le#els.

In the analsis phase is the positi#e or negati#einformation concerning the selected factors and le#els is

generated based on the pre#ious two phases. This phaseis most statistical in nature of the three phases of the

+.

22 Ta&("#$ met#

Although fractional factorial design allows a

fraction of the total number of runs re!uired in thefactorial design, there are no general guidelines for its

application or the analsis of the results obtained b

performing the e$periments. Taguchi1s approachcomplements these two important areas. &irst, he clearl

defines a set of general designs for factorial e$periments

that co#er man applications. The special set of designsconsists of orthogonal arras (A). The use of these

arras helps to determine the least number of

e$periments needed for a gi#en set of factors. Acomparison of number of e$periments in factorial designand Taguchi design is presented in Table '. econd, he

de#ised a standard method for analsis of the results.The combination of standard e$perimental design

techni!ues and analsis methods in the Taguchiapproach produces consistenc and reproducibilit

rarel found in an other statistical method.

Table ' 2omparison of &actorial design and Taguchidesign

&actors *e#el

&actorial design

Total no. ofe$periments

Taguchi

+esign

3() 3

4() 3

3 '5(3) 4

6 '4(6) 4

'7 654('7) '5

3 4'(3) 8

7 3(7) '4

Taguchi has established orthogonal arras

(A) to describe a large number of e$perimental

situations. The smbolic designation for these arrascarries the ke information on the si"e of the e$periment.

&or e$ample, designated arra *'4 re!uires '4 trail runs9*8 re!uires 8 e$periments and so on. The #ertical

columns of the arras ac!uire a special combinatorial

propert i.e., in an pair of columns in an A, allcombinations of the treatment (of the two factors

assigned to this pair) occur and the do so an e!ualnumber of times. This propert is called the balancing

propert of As. This balancing propert permits theuse of simple arithmetic to find the effect of the

e$perimental factors on the response under stud.Taguchi has tabulated '4 basic orthogonal arras that we

call standard orthogonal arras. The standard orthogonal


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arras along with the number of columns at differentle#els for these arras are listed in Table ..

Table tandard rthogonal Arras

rthogona

l Arra

0umbe

r of:ows

;a$imu

m 0o offactors

;a$imum no of

columns At thesele#els

3 7

*3*4

*8*'

34

8'

6

3''

6-

''

--

3-

--

--

--

--

*'5

*1'5*'4

*7

'5

'5'4

7

'7

74

5

'7

-'

-

-

-6

-

-

7-

-

-

--

5

*6**1

*5*15

6

55

''' A - fA B =e

@ > @ - f@ B =e

2 > 2 - f2 B =ee > e - (fA Cf@Cf2) =e

Per"ent Cntr$5(t$n

The percent contribution of each factor is the

ratio of the factor sum to the total, e$pressed in percent

/A > A B '


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64

8'

fficienc E >

F of dilution >

The e$perimenters log after translating factors

and their le#el #alues using *'4 arra is gi#en in Table 7

Table. 7$perimenters log sheet for GTAW

$perim

-ental0umber

2urrent(A)

Wire

+iameter(mm)

Wire&eed

:ate(mm?m

in)

:atio ofwire feed

rate totra#el

speed

/late

Thickness(mm)


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'<


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mm thick plate. The change in penetration depth isabout


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ii. Wire feed rate (factor 2) has the ne$t largest effecton bead width. @ increasing the feed rate from

'


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&igure 6 shows the relationship betweene$perimental #alue and predicted #alue of depth of

penetration in Gas Tungsten Arc Welding. It is obser#edfrom the figure that the #alues predicted b penetration

model (!n. 7.') are in good agreement withe$perimental #alues. The e$perimental and predicted

#alues of penetration and percentage error are gi#en inTable '. It can be obser#ed from the table that the

percentage error is less than 8F in all the cases e$ceptone. %ence it is concluded that the model can predict the

depth of penetration in GTAW with good accurac.

&igure 6 /redicted #alue =s $perimental #alue of

penetration in GTAWTable ' 2omparison between predicted #alue and

e$perimental #alue of penetration in GTAWL

$p.0o. /enetration(/) mm 2alculated(/) :esidual F rror


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'') Q;etals %andbook, 4th dition, =ol-'/roperties and selection of metals of American

societ for metals.') Q;aterials %andbook @ AW.

') QThe /rocedure %andbook of Arc Welding'thdition, @ *incoln.

'3) Q;echanical ;etallurg @ *innert.

experimental study of gas tungstun arc welding process paramenets

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