Effects of Shielding Gas on Gas Metal Arc Weld ing A luminum

Contrary to the conclusion of previous investigators, argon may be the optimum shielding gas for the gas metal arc welding of aluminum

BY W . R. REICHELT, J. W . E V A N C H O A N D M . G. H O Y

ABSTRACT. A r g o n , h e l i u m , a n d m i x ­tures o f these gases are used fo r sh i e l d ­ing in gas meta l -a rc w e l d i n g o f a l u m i ­n u m . Cons ide rab le w o r k has been d o n e p rev ious ly by o t h e r invest iga tors to d e f i n e t h e ef fects of these gases o n p e n e t r a t i o n , arc s tab i l i t y a n d po ros i t y . M o s t of th is w o r k , h o w e v e r , was per­f o r m e d by m a i n t a i n i n g an " o p t i m u m " arc gap. C o n s e q u e n t l y , for var ious c o m p o s i t i o n s a n d f l o w rates s tud ies , w e l d parameters w e r e also va r ied .

To fu r t he r unde rs tand the ef fects o f sh ie ld ing gas o n gas meta l -a rc w e l d i n g a l u m i n u m , a s tudy was c o n d u c t e d w h e r e b y al l w e l d set t ings w e r e preset at cons tan t va lues and ef fects o f sh ie ld ing gas c o m p o s i t i o n a n d f l o w rate o n arc gap , vo l t age , and cu r ren t , in a d d i t i o n t o p e n e t r a t i o n , arc s tab i l i t y , and po ros i t y w e r e eva lua ted . Sh ie ld ing gas c o m p o s i t i o n and f l o w rate b o t h a f fec ted d e p t h o f p e n e t r a t i o n . M a x i ­m u m pene t ra t i on was o b t a i n e d w i t h pu re argon at 150 c f h , whe reas m i n i ­m u m d e p t h o f p e n e t r a t i o n was asso­c ia ted w i t h a 25% a r g o n / 7 5 % h e l i u m m ix tu re at 200 c f h .

Effects o f sh ie ld ing gas o n d e p t h of pene t ra t i on co r re la ted d i r ec t l y w i t h ef fects o f s h i e l d i n g gas o n wa t t age . Gas c o m p o s i t i o n s h igh in a rgon also p r o d u c e d best arc s tab i l i t y , a n d t h e m i n i m u m a m o u n t of m i c r o - p o r o s i t y . Results of th is w o r k suggest t ha t , c o n ­trary to t he c o n c l u s i o n s o f p rev ious invest igators , a rgon my be the o p t i ­m u m sh ie ld ing gas for gas meta l -a rc w e l d i n g o f a l u m i n u m .

Paper presented under sponsorship of the Aluminum Alloys Committee of the Weld­ing Research Council at the AWS 60th Annual Meeting in Detroit, Michigan, dur­ing April 8-12, 1979.

W. R. REICHELT, J. W. EVANCHO and M. G. HOY are with the Joining Division of Alcoa Laboratories, Alcoa Center, Pennsylvania.

I n t r o d u c t i o n

Sh ie ld ing gas, as an i m p o r t a n t va r i ­ab le in gas meta l -a rc w e l d i n g o f a l u m i ­n u m , serves t h ree p r ima ry f u n c t i o n s : It p rov ides a p lasma fo r c o m m u t a t i o n o f cu r ren t ; it p ro tec ts t h e w e l d p o o l f r o m react ing w i t h t he air e n v i r o n m e n t ; and w h e n w e l d i n g us ing d i rec t cu r ren t re­verse po la r i t y (DCRP) , it can p r o v i d e the c l ean ing ac t i on w h i c h par t ia l l y removes a l u m i n u m o x i d e f r o m the a l u ­m i n u m p la te .

The phys ica l p roper t i es a n d charac­ter ist ics o f b o t h argon and h e l i u m , t h e t w o p r i n c i p l e s h i e l d i n g gases used f o r w e l d i n g a l u m i n u m , are c o m p a r e d in Tab le 1 . The i o n i z a t i o n p o t e n t i a l o f argon is m u c h l o w e r t h a n that of h e l i u m ; i o n i z a t i o n p o t e n t i a l is t h e vo l tage requ i r ed to m o v e an e lec t ron f r o m an a t o m , t he reby t u r n i n g t he a t o m i n to an i o n . C o m p a r i s o n o f i o n i ­za t ion po ten t i a l s gives an i n d i c a t i o n as

t o t he re lat ive ease w i t h w h i c h the sh ie ld ing gas f o rms the p lasma; t he h igher t he i o n i z a t i o n p o t e n t i a l , t h e more d i f f i cu l t it is t o i n i t i a te an arc. H igh i o n i z a t i o n po ten t i a l s can also result in p o o r arc s tab i l i t y ; h e l i u m , t he re fo re , w e l d s w i t h a less s tab le arc.

Therma l c o n d u c t i v i t y is i m p o r t a n t , because a gas w i t h g o o d t h e r m a l c o n ­d u c t i v i t y w i l l he lp t o c o n d u c t heat i n to t h e w o r k p i e c e . Deg ree of t h e r m a l c o n d u c t i v i t y has been r e p o r t e d to af fect t he shape of t h e w e l d bead and the c o n d i t i o n o f t he meta l next t o t he w e l d . H e l i u m ' s h i gh t h e r m a l c o n d u c ­t i v i t y re lat ive t o tha t of a rgon is o n e fac to r w h y w e l d s m a d e w i t h h e l i u m show a b roader w e l d p u d d l e . Dens i t y o f h e l i u m is o n e - t e n t h tha t o f a rgon . Because o f th is d i f f e rence in dens i t y , h igher f l o w rates are genera l l y re­qu i r ed w h e n w e l d i n g w i t h h e l i u m . A rgon possesses exce l l en t c l ean ing

Table 1—Properties of Shielding Gas

Ionization potential Arc init iat ion Arc stability

Thermal conductivi ty (cal/sq. cm/cm/ °C /s )

Density (relative to air) Cleaning action

Argon

15.8 eV Good Good

0.406 x 10

1.38 Good

Helium

24.6 eV Poor Poor

3.32 X 10-

0.137 Poor

Table 2—Advantages/Disadvantages of Hel ium and Argon

Advantages

Helium • Higher arc voltage and assumed greater heat input (deep penetra­t ion and high welding speeds)

• Broad weld root width Argon • Good arc init iat ion and stability

• More effective shielding • Low cost • Good cleaning

Disadvantages

• Poor cleaning • Poor arc init iat ion and stability • Cost • Requires greater f low rates • Narrow weld root width

W E L D I N G R E S E A R C H S U P P L E M E N T I 147 -s

Fig. 1—Grooved 5083 plate. Groove dimensions: VA in. (6.3 mm) deep and Yi in. (12.7 mm) wide

Fig. 2—Commercially available equipment utilized during weld evalua­tion. Shown are the welding torch, arc viewer, track wire filler metal feed controller

action. Helium on the other hand pro­vides no cleaning.

Because of the differences in physi­cal properties and characteristics of helium and argon, each shielding gas has its advantages and disadvan­tages-Table 2. A higher arc voltage associated wi th helium results in a greater heat input and supposedly a deeper penetration. This greater heat input also permits welding at higher speeds. The main advantage asso­ciated wi th the high heat input, how­ever, is the broad weld root width obtained when welding wi th helium.

Although the greater heat input is a major advantage for hel ium, this gas also has several disadvantages. Helium does not assist in cleaning the oxide from aluminum plate, and its high ionization potential results in difficult arc initiation and poor arc stability. A greater f low rate is also required wi th helium because of its lower density. Probably the greatest disadvantage of this shielding gas is related to its cost. Helium continues to be more costly than argon.

Argon has many advantages over helium. Because of its low ionization potential, it demonstrates good arc initiation characteristics and excellent arc stability. Argon is also effective in assisting cleaning of the oxide from aluminum plate. Because of its higher density, argon provides a more effec­tive shield from the environment at lower f low rates than are required for helium; also, most importantly, argon is cheaper than helium. The main dis­advantage attributed to argon is the narrow weld root width that results when using this shielding gas.

Many of these statements about argon and helium as shielding gases have resulted from qualitative evalua­tions over several years. However, only limited quantitative data on the effects of shielding gas composit ion or f low rate are available in the literature. As a

result, several "rules of t humb" have evolved as to the benefits of the vari­ous shielding gases or the mode of using the various shielding gases w i th ­out substantial theoretical verification. In this regard, most references on arc welding indicate that shielding gas flow rate should be selected by reduc­ing f low rate until an unstable arc is observed and then increasing the f low rate slightly for a safety margin. Anoth­er statement is that helium provides greater penetration.

Previous in-house process develop­ment work has suggested that shield­ing gas f low rates may be just as significant as shielding gas composi­tion in affecting weld penetration and weld cross-section geometry. To quan­tify the effects of shielding gas compo­sition and f low rate, a program investi­gating both argon and helium was conducted.

Procedure

Effects of shielding gas composit ion and f low rate on weld penetration and weld cross-section geometry were de­termined by automatic GMA welding in the flat position. Shielding gas com­positions ranging from pure argon to pure helium, including various mix­tures, were evaluated at flow rates ranging from 50 cfh (23.5 l iters/min) to 300 cfh (141 liters/min). The program was conducted in two phases as described below.

Phase l-No Arc Gap Control

Initial weld parameters were deter­mined using a shielding gas composed of 50 cfh (23.5 liters/min) helium and 50 cfh (23.5 liters/min) argon. Wire filler metal feed speed, current and travel speed were adjusted to produce a smooth welding arc and a sound weld. The weld settings determined by an experienced welder's observations fol low: voltage-35 V; current-404 A;

travel speed—12 ipm (5 mm/s). These parameters resulted in an arc

length of 0.148 in. (4 mm). Subsequent welds were made maintaining these machine settings as shielding gas com­position and f low rate were varied. Initially, three welded samples were made for each condit ion of shielding gas composit ion and f low rate. How­ever, uniform results permitted the number of samples to be reduced to one per shielding gas variable.

Phase II—Arc Gap Control

The procedure for Phase II was simi­lar to that of Phase I. In this phase, however, a constant arc gap of 0.150 in. (4 mm) was maintained first by adjusting current. The procedure was then repeated and arc gap was adjusted by voltage (filler metal feed).

Accurate shielding gas flow rates were maintained through the use of thermal mass meters. Voltage and cur­rent were recorded using a Brush recorder, and arc gap was observed by means of an arc viewer mounted on the travel carriage.

All welds were made on a grooved 5083-0 plate, 1 X 9 X 1 2 in. (25.4 x 228 X 305 mm), using 3/32 in. (2.4 mm) diameter 5183 electrode. The groove was VA in. (6.3 mm) deep and Vi in. (12.7 mm) wide—Fig. 1. Shielding gas was commercial welding grade argon and helium.

All welds were cross-sectioned at the midpoint perpendicular to the weld. The cross-section was polished and etched; and weld penetration, width at varying depths,* and crown height were measured. In Phase II, welders' comments concerning arc characteristics were also docu­mented.

*Weld width measured approximately VA in. (6.4 mm) from bottom of weld

148-sl M A Y 1980

Equipment

Commercially available equipment was utilized for this investigation—Fig. 2. This equipment included a water-cooled welding torch wi th a 3/4 in. (19 mm) gas cup, a wire filler metal feed controller, a Gulco KAT track, and a drooping volt-ampere characteristics power supply.

Results

Phase I—No Arc Gap Control

When arc gap was allowed to vary, both shielding gas composit ion and f low rate significantly affected weld penetration—Fig. 3. For pure argon, maximum penetrations were asso­ciated wi th 150 cfh (70.5 liters/min) f low rates. Flow rates greater than or less than 150 cfh (70.5 l iters/min) resulted in lesser penetrations. M in i ­mum penetrations were associated wi th shielding gas compositions be­tween 60 and 80% helium at approxi­mately 150 cfh (70.5 l iters/min) to 200 cfh (94 liters/min) f low rates. Increas­ing or decreasing the f low rate or increasing or decreasing the percent­age of helium in the shielding gas resulted in increased penetration. In no case, however, was penetration as great as the level obtained wi th 150 cfh (70.5 liters/min) pure argon.

Shielding gas f low rate had little effect on weld root w id th . However, shielding gas composit ion significantly affected weld root width. Root widths less than 0.250 in. (6.3 mm) were pro­duced wi th pure argon and increased to 0.4 in. (10 mm) with compositions

NO ARC GAP CONTROL

100

ARGON - CFH

Fig. 3—Effect of shielding gas on weld penetration

containing 70% helium—Fig. 4. Effects of shielding gas on weld

cross-sectional area were complex and are shown in Fig. 5. For shielding gas compositions rich in argon, f low rate had a significant effect on cross-sectional area. Maximum cross-sec­tional areas of 1 square inch (645 mm2) was obtained at f low rates between 100 cfh (47 liters/min) and 150 cfh (70.5 liters/min) for compositions con­

taining 50% or more argon. As the compositions became richer in he­lium, f low rate had less effect; howev­er, variations in composit ion between 70 and 90% helium did affect cross-sectional area.

These results are further illustrated in Fig. 6, which shows weld cross-section profiles as affected by shield­ing gas composition and f low rate. Of particular interest is the effect of f low

90% He 80% 60%

50%

20%

10%

150

E 100

s => Zl III

50

9 0 %

/ /

He 80%

Jj

/

70%

/

. 8 5 0 ^ - -

60%

NO ARC GAP CONTROL

\ . 850 SQ. IN.

/ \A.900 \

^V.950 V A A

\ \ j . O O o \ \ Y \

j.ooo \ J>«r\ \ \ 20

50 100 ARGON - CFH

150

Fig. 4—Effect of shielding gas on weld root width

50 100 ARGON - CFH

Fig. 5—Effect of shielding gas on weld cross-sectional area

150

W E L D I N G RESEARCH SUPPLEME NT I 149-s

200 NO ARC GAP CONTROL

U

uJ I

0 0

50

100

ARGON-CFH

150 200

Fig. 6—Effect of shielding gas on weld cross-section geometry

rate on increasing the weld root width when pure argon is used. Weld root profile for 150 cfh (70.5 l iters/min) argon is similar to profiles using an argon-helium gas mixture. A flow rate of 150 cfh (70.5 liters/min) pure argon provides adequate weld width and deep penetration and is a significant

improvement over the narrow weld spike typically associated wi th pure argon. Wide weld widths generally associated wi th pure hel ium or com­positions high in helium are most evi­dent at the top of the weld. However, this wide weld bead provides no sig­nificant benefit.

Phase II—Arc Gap Control

Arc Cap Controlled by Current. When arc gap was adjusted by current to 0.150 in. (4 mm), penetration was primarily affected by shielding gas f low rate; shielding gas composit ion had essentially no effect—Fig. 7.

80% 60% 90% He 80%

X O 100

50

r \.350 IN. I I / ! 1

I / /

\i //yy^

) \ .350 IN.

Jy^/

/ \ ARC GAP - 0.150"

/ # \ / / J \ ADJUSTMENT BY

/ ^ y \CURRENT

\ / y

JS \ ^^250 I N ^ \

.200 IN. _ \ — * \ "

30%

20%

50 100 ARGON - CFH

50 100 ARGON - CFH

Fig. 7—Effect of shielding gas on weld penetration Fig. 8—Effect of shielding gas on weld root width

150-sl M A Y 1980

Increasing the gas f low rate beyond 100 cfh (47 liters/min) decreased weld penetration.

Both shielding gas flow rate and composit ion affected weld root width—Fig. 8. Mimimum weld root widths were associated wi th pure argon shielding at 50 cfh (23.5 liters/ min). Maximum weld root widths were associated wi th pure helium at f low rates exceeding 100 cfh (47 liters/ min).

Flow rate had a significant effect on weld cross-sectional area for shielding gas compositions rich in argon—Fig. 9. Increasing flow rate decreased weld cross-sectional area. On the other hand, shielding gas compositions rich in helium were not affected by f low rate, although changes in helium con­centration did affect the weld cross-sectional area. Maximum cross-sec­tional areas of 1 square inch (645 mm'2) were obtained wi th pure helium.

The results are further illustrated in Fig. 10. The spike typically associated wi th welds made using pure argon shielding gas are evident in this figure. It is also obvious that the larger cross-sectional area associated wi th welds made using pure helium shielding gas results primarily from a broadening of the top of the weld (weld surface bead). Contrary to what would be expected, the weld root width is not significantly affected either by shield­ing gas composit ion or f low rate.

Effects of shielding gas composit ion

I50

90% He 80% 70% 60%

E _ i UJ

x

50%

40%

30%

20%

10%

50 100

ARGON - CFH Fig. 9—Effect of shielding gas on weld cross-sectional area

150

and f low rate on arc characteristics are summarized in Fig. 11. A smooth weld­ing arc was obtained wi th a wide range

of shielding gas compositions at f low rates between 100 cfh (47 liters/min) and 125 cfh (58 l i ters/min). Increasing

X

I00

_ j

jjj 50

0

ARC GAP =0.150 in.

ADJUSTMENT BY

CURRENT

0 50 100 150

£L

o _ l UJ >

X o DC < UJ CO

z UJ

0. o _ l UJ

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or

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DC

Q .

o

> UJ

o -̂ X DC

< UJ CO

a. o _ J UJ

> UJ

o >*. x o DC < UJ CO UJ DC ARGON-CFH

Fig. 10—Effect of shielding gas on weld cross-section geometry

WELDING RESEARCH SUPPLEMENT I 151-s

100

50

FUZZY \ ARC \

~ VIOLENT / ARC /

I

SMOOTH ARC

V

UNDULATING PUDDLE

I

VIOLENT ARC -

UNDULATING PUDDLE

V I

90% He 80%

Fig. 11-Effect of shielding adjustment

100 150 ARGON -CFH

gas on arc characteristics—current

Fig. 12— Effect of shielding gas on weld penetration SO 100

ARGON - CFH

f low rates beyond 125 cfh (58 liters/ min) resulted in a rough, undulating arc. Violent arc characteristics were associated when pure helium was employed.

Arc Cap Adjusted by Wire Feed. Contrary to the results obtained when arc gap was adjusted by current, when arc gap was adjusted by wire feed, shielding gas f low rate did not affect weld penetration significantly. Pene­tration, however, was significantly affected by shielding gas composit ion — Fig. 12. Maximum penetrations were obtained for pure argon and decreased

as percentage of helium was in­creased.

Weld root width was affected pri­marily by shielding gas composit ion. However, shielding gas flow rate slightly affected root w id th , especially at f low rates exceeding 150 cfh (70.5 l iters/min). Min imum weld root widths were associated wi th pure argon, and maximum weld root widths were associated wi th pure helium, as shown in Fig. 13.

Both shielding gas flow rate and composit ion affected weld cross-sec­tional area slightly. Maximum cross-

sectional areas are associated wi th pure argon at f low rates less than 100 cfh (47 liters/min)—Fig. 14. These results are dramatically illustrated in Fig. 15. The tremendous benefit of pure argon on weld penetration is obvious from Fig. 15. Of particular interest is the tendency towards a wider weld root width for pure argon at 100 cfh (47 liters/min) than is normally associated wi th pure argon shielding. Weld root w id th increased considerably when pure helium was employed; however, penetration de­creased significantly. Benefits of ad-

150

100

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w .500 IN.\

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50%

30%

50 100

ARGON - CFH

Fig. 13-Effect of shielding gas on weld root width

50 100

ARGON - CFH 150

Fig. 14—Effect of shielding gas on weld cross-sectional area

152-sl M A Y 1980

150

X y !00

I 5 0

0

ARC GAP • 0.150 in. ADJUSTMENT BY

WIRE FEED

0 50 100

ARGON-CFH 150

Fig. 15—Effect of shielding gas on weld cross-section geometry

100

I o

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50

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fig. 1 ad jus

SLUDGE I

FUZZY I ARC

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/ ^ \ / \ ROUGH ARC \

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100

ARGON

as on

(CFH)

VIOLENT ARC • UNDULATING

PUDDLE

SLIGHT UNDULATING

PUDDLE

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arc characteristics-wire

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feed

z

z o

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III z 111

Fig. 17—Effect of welding current on weld penetration

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-200 - 220 O • A -=£ 200 © a / \ - •- ?2o mm A

ARC GAP CONTROL

O CURRENT • 50% CURRENT - 50% WIRE FEED

A WIRE FEED

ding helium to the shielding gas when adjustments of arc gap are made by wire feed are not evident from these data.

The effects of shielding gas on arc characteristics are summarized in Fig. 16. As was the case when arc gap was adjusted by wire filler metal feed, a wide range of shielding gas composi-

300

tions and flow rates resulted in a smooth welding arc. Increasing flow rates above 150 cfh (70.5 l iters/min) resulted in an undulating puddle, and pure helium created a fuzzy arc which produced shallow penetration.

4 0 0 500

C U R R E N T ( A M P E R E S )

Discussion

It is evident from this investigation that both shielding gas composit ion and flow rate significantly affect weld cross-section geometry. These effects,

a. O _ i UJ >

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x o DC < LLi

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WELDING RESEARCH SUPPLEMENT I 153-s

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0 CURRENT ADJUSTMENT

O W I R e F E E D ADJUSTMENT

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-

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60 70 JOULES x 103

.600

.200

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8? o 0

I I

I

o°° o

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m CURRENT ADJUSTMENT

O WIRE FEED ADJUSTMENT

• •

I I

40 50 80 90

Fig. 18—Effect of heat input and method of arc adjustment on weld cross-sectional area

60 70

JOULES X 103

Fig. 19— Effect of heat input and method of arc adjustment on penetra­tion

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J5

A

3

2

I

-

o

-

-

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CURRENT ADJUSTMENT

WIRE FEED ADJUSTMENT

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100%

— 50%

25%

^

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HELIUM

-100% 50%

75%

-

60 70

JOULES x 103

Fig. 20—Effect of heat input and method of arc adjustment on weld root width

WIDTH (IN)

Fig. 21—Effect of shielding gas composition on weld penetration/ weld root width ratio

however, are not consistent w i th those previously reported in the literature. Depending on how arc gap was adjusted, much deeper penetration could be obtained when pure argon was employed. More important, how­ever, is the effect of f low rate. Flow rate not only affects weld penetration but weld root width and, by employ­ing proper controls, a desirable weld cross-section geometry can be ob­tained when using pure argon.

Reasons for the effects of shielding gas composit ion and f low rate on weld cross-section geometry are not ob­vious. Contrary to what had been reported previously, greater penetra­tion did not result from a higher arc voltage associated wi th pure helium shielding. Penetration, however, was affected by the welding parameters, particularly current (Fig. 17), regardless of voltage (wire feed speed) em­ployed. The differences in weld cross-

section geometry then are attributed to the effects of changing shielding gas composition and f low rate on welding current. This is further illustrated in Figs. 18,19 and 20.

The effect of heat input on weld cross-sectional area is indicated in Fig. 18. Regardless of shielding gas compo­sition and method of arc gap adjust­ment, weld cross-sectional area in­creased as expected wi th increasing heat input. The method of arc gap adjustment did, however, affect the weld cross-section geometry. As indi­cated in Fig. 19, increasing heat input increased weld penetration when ad­justment in arc gap was made by wire feed adjustments. Current adjust­ments, however, resulted in a constant weld penetration even though total heat input was affected substantially. The opposite effect is noted for weld root width—Fig. 20. Increasing heat input by wire filler metal feed adjust­

ment decreased weld root width as heat input increased. Conversely, in­creasing heat input increased weld root width when arc gap was main­tained by current adjustment.

True improvements in weld bead geometry are associated wi th increas­ing weld root width whi le maintaining a constant penetration or increasing penetration. Such improvement has normally been attributed to the use of helium mixtures in shielding gas. Fig­ure 21 shows the ratio of weld penetra­tion to weld root width as a function of shielding gas composit ion. Greater weld root widths for a given penetra­tion were obtained when pure helium was employed; however, greater depths of penetration were obtainable with pure argon. Most interesting, however, is that additions of helium to shielding gas up to a level of 75% helium did not significantly affect ratio of weld penetration to weld root

154-sl M A Y 1980

width.

Conclusion

Results of this work indicate that selection of shielding gas in gas metal-arc welding is an important criteria which affects not only the arc charac­teristics but the weld geometry. Although much concern has previous­ly been expressed regarding the nar­

row weld root widths resulting from argon shielding, proper selection of shielding gas f low rate and method of arc adjustment can optimize weld root width when pure argon shielding is employed and produce satisfactory weld geometries. Consequently, the fol lowing conclusions are warranted:

1. Shielding gas composit ion and f low rate can affect weld penetration and cross-sectional area.

2. The manner by which shielding gas composition and flow rate affected weld penetration and cross-sectional area is dependent on method of arc gap adjustment.

3. Maximum penetrations are pro­duced with pure argon or argon-rich shielding gas.

4. Desirable weld cross-sectional geometry can be obtained wi th pure argon shielding provided f low rate is optimized.

0-o —I LU > LU

a x o DC < LU

WRC Bulletin 256 January 1980

Review of Data Relevant to the Design of Tubular Joints for Use in Fixed Offshore Platforms

by E. C. Rodabaugh

The program leading to this report was funded by 13 organizations over a two-year period. The objective was to establish and/or validate design methods for tubular joints used in fixed offshore platforms. The report is divided into four self contained chapters (1) Static Strength (2) Stresses (3) Fatigue (4) Displacements, wherein detailed cross comparisons of various types of test data and design theories are reviewed.

Publication of this report was sponsored by the Subcommittee on Welded Tubular Structures of the Structural Steel Committee of the Welding Research Council.

The price of WRC Bulletin 256 is $13.00 per copy, plus $3.00 for postage and handling. Orders should be sent with payment to the Welding Research Council, 345 East 47th St., Room 801, New York, NY 10017.

WRC Bulletin 257 February 1980

Analysis of the Ultrasonic Examinations of PVRC Weld Specimens 155, 202 and 203 by Standard and Two-Point Coincidence Methods

by R. A. Buchanan, prepared for publication by 0. F. Hedden

This report describes two methods of analysis of ultrasonic examination data obtained in a 13-team round-robin examination of three intentionally flawed weldments. The objective of the examinations is to determine the accuracy of independently detecting, locating and sizing the weld flaws, using a fixed procedure.

Computer programs to facility comparison of flaw locations with the ultrasonic data, for each of the specimens and both of the methods, are appended to the report.

Publication of this report was sponsored by the Subcommittee on Nondestructive Examination of Materials for Pressure Components of Pressure Vessel Research Committee of the Welding Research Council.

The price of WRC Bulletin 257 is $11.00 per copy, plus $3.00 for postage and handling. Orders should be sent with payment to the Welding Research Council, 345 East 47th St., Room 801, New York, NY 10017.

W E L D I N G RESEARCH SUPPLEMENT I 155-s