The article describes the influences of welding parameters, modes of metal transfer through the arc and the number of wires applied on weld formation and final shape. Diagrams show the influence of current intensity and arc voltage while a figure shows the influence of streaming and rotating metal transfers on the final weld shape. Diagrams and macro specimens, however, show the influence of the number of wires used on the weld shape and weld formation in submerged arc welding with a triple-wire electrode.U članku je opisan utjecaj parametara zavarivanja, utjecaj načina prolaska materijala kroz električni luk i utjecaj broja žica na nastajanje zavara i njegov konačni oblik. Pomoću dijagrama su prikazani utjecaji jačine struje zavarivanja i napetosti električnog luka, a slika prikazuje utjecaj prelaska materijala tečenjem i utjecaj prelaska materijala okretanjem na završni oblik zavara. Dijagramima i pomoću makrobrušenih uzoraka prikazan je utjecaj broja žica na oblik i nastanak vara kod zavarivanja trostrukom žičanom elektrodom pod zaštitom praha

J. Tušek

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METALURGIJA 41 (2002) 2, 89-92 89J. TUŠEK: FACTORS AFFECTING WELD SHAPE IN WELDING WITH A TRIPLE-WIRE ELECTRODEReceived - Primljeno: 2001-08-30Accepted - Prihvaćeno: 2002-01-30Original Scientific Paper - Izvorni znanstveni radISSN 0543-5846METABK 41 (2) 89 (2002)UDC - UDK 621.791.753.5.042=20. ŠEKJ. Tušek, Welding Institute, Ljubljana, SloveniaFACTORSAFFECTING WELD SHAPE IN WELDING WITH A TRIPLE-WIRE ELECTRODEINTRODUCTIONIn fusion arc welding the final weld shape is influencedby welding parameters, mode of metal transfer, number ofwelding wires used and their arrangement in the contacttube, type of material to be welded, type of shielding me-dium and similar.In some articles, descriptions of investigations on theinfluence of the kind of material and the type of shieldingmedium used on the weld shape and size can be found [1-4]. Articles describing the influences of temperature gra-dient of surface tension, in which the arc is burning, andof electromagnetic forces on motion of the weld pool andthe weld depth and shape can also be found [5-7]. M. Ushiosupplies even a mathematical description of motion of theweld pool in TIG welding [8, 9].Not even a single publication, however, has been foundto report on influences of metal transfer and the number ofwires in the contact tube on weld formation.INFLUENCE OF WELDING PARAMETERSON WELD FORMATION AND FINAL SHAPEThe welding current is the most important parameter.An increase in this parameter produces an increase in thepenetration depth and the weld cross section.The article describes the influences of welding parameters, modes of metal transfer through  the arc and thenumber of wires applied on weld formation and final shape. Diagrams show the influence of current intensity andarc voltage while a figure shows the influence of streaming and rotating metal transfers on the final weld shape.Diagrams and macro specimens, however, show the influence of the number of wires used on the weld shapeand weld formation in submerged arc welding with a triple-wire electrode.Key words: weld, triple electrode, fusion arc welding, metal transferFaktori koji utječu na oblik zavara kod elektrolučnog zavarivanja trostrukom žičanom elektrodom. Učlanku je opisan utjecaj parametara zavarivanja, utjecaj načina prolaska materijala kroz električni luk i utjecajbroja žica na nastajanje zavara i njegov konačni oblik. Pomoću dijagrama su prikazani utjecaji jačine strujezavarivanja i napetosti električnog luka, a slika prikazuje utjecaj prelaska materijala tečenjem i utjecaj prelaskamaterijala okretanjem na završni oblik zavara. Dijagramima i pomoću makrobrušenih uzoraka  prikazan jeutjecaj broja žica na oblik i nastanak vara kod zavarivanja trostrukom žičanom elektrodom pod zaštitom praha.Ključne riječi: zavar, trostruka žičana elektroda, elektrolučno zavarivanje topljenjem, prelazak materijalaElectrode Weld poolParent metalWeldElectrode Weld poolParent metalWelda)b)Figure 1.Slika 1.Two different modes of melting the parent metal: a) dire-ctly by arc, b) indirectly by arc via the weld poolDva različita načina topljenja osnovnog materijala: a) iz-ravno električnim lukom, b) neizravno električnim lu-kom preko taljevine zavaraMETALURGIJA 41 (2002) 2, 89-9290J. TUŠEK: FACTORS AFFECTING WELD SHAPE IN WELDING WITH A TRIPLE-WIRE ELECTRODEWelding voltage U is influenced mostly by the arclength. Increase in the arc length produces increase also inthe range of movement of the cathode spot and anode spotson the workpiece, which consequently produces increasein the weld width.Welding speed v is a very important welding param-eter too. An increase in welding speed produces a decreasein heat input and the volume of deposited metal per unit oflength of the weld. Welding speed has a specific influenceon the weld penetration. At a high speed the weld pool,which is formed from the parent metal and the filler mate-rial, can not follow the arc and will lag behind. In thiscase, the arc will burn between  the electrode and theunmolten workpiece, which results in a greater penetra-tion depth hu than in the case of a somewhat lower weld-ing speed v, where the arc is burning between the elec-trode and the weld pool, which prevents the arc to melt theparent metal deeper. Figure 1. shows both modes of arcburning described above.The influence of welding speed v on the penetrationdepth hu is shown in Figure 2.. The penetration depth as afunction of the welding speed is shown with two differentsets of welding conditions. The first curve shows the in-fluence of welding speed v on the penetration depth intriple-wire electrode submerged arc welding on a flat plate,without welding edge preparation, with a current intensityI of 410 A per wire, and with a welding voltage U of 30 V.The diagram shows that the penetration depth hu decreaseswith the increase in welding speed v up to 45 cm/min, thenit begins to increase along with the increase in weldingspeed v from 45 cm/min up to 75 cm/min, and finally itagain decreases if welding speed v is increased above 75cm/min. The initial and final parts of the curve are quitelogical since with increase in the welding speed, heat en-ergy input decreases, which causes the penetration depthto reduce. The part of the curve indicating the increase inthe penetration depth hu, however, can be explained by atransition from the indirect mode of melting the parentmetal to the direct one. This indicates that the increase inthe welding speed v above 45 cm/min produces decreasein the weld pool depth under the first arc, i.e. the weldpool begins to lag behind with regard to the first arc.Similar findings could be stated for curve no. 2 in thesame diagram, the only difference being that the transitionfrom the indirect melting of the parent metal to the directone is going on at a much higher welding speed v due to ahigher current intensity I and a differently shaped weldinggroove [10].INFLUENCE OF THE MODE OF MATERIALTRANSFER ON WELD FORMATION AND SHAPEThe mode of material transfer is largely influenced bywelding parameters, the shielding medium used, the typeof power source, and the pressure in which the arc is burn-20 65 110 155 2009876543 [mm]huv [cm/min]1260°15157Figure 2.Slika 2.Influence of welding speed  on the penetration depth  in submerged arc welding with triple electrode, wire  = 3 mm,  = 9 mm,  = 25 mm, electrode positiveUtjecaj brzine zavarivanja na dubinu uvara kod zava-rivanja trostrukom elektrodom pod prahom: žica  = 3 mm,  = 9 mm,  =25 mm, plus pol na elektrodiv hudb Ldb LI = 410 A, U = 30 VI = 515 A, U = 32 VAAAVLEMWire spoolsStraighteningmechanismFeedsystemShunts* Contact tube   divided into   three separate   parts*bWorkpieceWelding rectifierFigure 3.Slika 3.Schematic representation of equipment for triple-wire welding:  - wire extension length,  - distance between two wiresShematski prikaz naprave za zavarivanje trostrukom žičanom elektrodom.  - slobodna duljina elektrodne žice;  - razmak između dvije žiceL bLbMETALURGIJA 41 (2002) 2, 89-92 91J. TUŠEK: FACTORS AFFECTING WELD SHAPE IN WELDING WITH A TRIPLE-WIRE ELECTRODEing. Modes of material transfer may be classified, accord-ing to the International Institute of Welding (IIW), intoeight groups [1].The greatest influence on the weld shape is exerted bythe rotating material transfer. Current density in the wireis so high that electromagnetic forces induce rotation ofthe wire extension, the melted material of the wire exten-sion flows in a stream into the weld and forms a ratherwide penetration.INFLUENCE OF THE NUMBER OF WIRES USEDON WELD FORMATION AND FINAL WELD SHAPEIt has already been stated that almost no data are avail-able in the literature on the influence of the number ofwires used on weld formation or on the function of indi-vidual wires in weld shaping in multiple-wire welding.The influence was investigated in submerged arc weld-ing with a triple-wire electrode. Equipment for triple-wirewelding is schematically shown in Figure 3.. All three wiresare fed through a joint contact tube, they have a commonpower source, the same feed rate and joint regulation. Inour investigations, the wires were arranged in the tandemposition, i.e. one after another in the welding direction [11].In the investigations, a wire for submerged arc weldingwith a diameter d of 2 mm was used, the distance betweenwires b being 8 mm and the wire extension length L 25 mm.Welding was carried out at welding speeds v of 0.7 m/min,1.4 m/min, and 1.8 m/min. With each speed, a differentlyshaped groove was applied (Figure 4.).Current intensity I was 390 A for the first three weldsand 480 A for the other three welds. That is to say that themodes of weld formation and the influence of the wires inweld shaping were investigated in eighteen different welds,i.e., six of them with a single wire, six with a twin-wireelectrode, and six with a triple-wire electrode. All the weldswere submerged arc welded, the conditions per wire be-ing the same for all. This is further to say that the weldingspeed v and the arc voltage U were constant.v = 1.8 m/min v = 1.4 m/minv = 0.7 m/min90° 70°1460°8Figure 4.Slika 4.Groove shapes used when investigating the function of wires in weld shaping in multi-ple-wire weldingOblik zavarnog žlijeba kod istraživanja uloge žica pri oblikovanju za-vara kod zavarivanja višežičanom elektrodomEach welding performed, the weld concerned was cut,a macrosection was made, its dimensions were measured,and the results obtained were plotted in the diagram shownin Figure 5.. The diagram shows six curves each consist-ing of three parts. The first (left) part of each curve repre-sents the penetration depth hu and the penetration width buof a weld produced with a single wire, the second (middle)part of each curve the penetration depth and width of aweld produced with a twin-wire electrode, and the third(right) part of each curve the penetration depth and widthof a weld produced with a triple-wire electrode. In all threevariants of welding shown with a single curve, the weld-ing current per wire, the wire feed speed and the weldingspeed were the same. All six curves, however, indicatethat the first wire, either in a twin-wire electrode or in atriple-wire electrode, primarily affects the penetrationdepth hu and the penetration width bu least.The welding parameters stated permitted, in all the casesof welding, direct melting of the parent metal. The weldingspeeds v were namely selected in such a way that the weldpool lagged behind with regard to the first arc. This holdstrue for welding with the single electrode as well as with thetwin and triple electrodes. Macrographs in Figure 6. indi-cate that direct melting of the parent metal, in order to ob-tain a quality weld, may be achieved only in welding withseveral wires or with a multiple-wire electrode.5 10 15 20 25 300 02468101214I   = 390 A/wireI   = 480 A/wireh [mm]ub [mm]u     v  = 1.8 m/minI   = 390 A/wireI   = 480 A/wire    v  = 1.4 m/minI   = 390 A/wireI   = 480 A/wire    v  = 0.7 m/min1 wire2 wires3 wiresFigure 5.Slika 5.Influence of the number of wires used on formation of penetration depth hu and width bu in submerged arc weldingUtjecaj broja upotrebljenih žica kod nastajanja dubine hu i širine uvara bu pri zavarivanju pod prahomMETALURGIJA 41 (2002) 2, 89-9292J. TUŠEK: FACTORS AFFECTING WELD SHAPE IN WELDING WITH A TRIPLE-WIRE ELECTRODEREFERENCES1. The Physics of Welding (ed. J. F. Lancaster), Pergamon Press, Ox-ford 19862. C. L. Howard, Welding Journal,  36 (1957) 7, 335-3413. C. R. Heiple et al., Welding Journal, 62 (1983) 3, 72-774. B. N. Badjanov et al., Avtomatičeskaja svarka, 28 (1975) 1, 775. G. M. Oreper et al., Welding Journal, 62 (1983) 11, 307-3126. M. L. Tin et al., Welding Journal, 64 (1985) 6, 163-1697. P. Burgart et al., Welding Journal, 65 (1986) 6, 150-1558. M. Ushio, Welding International, 5 (1991) 8, 593-5979. M. Ushio, Welding International, 5 (1991) 9, 679-68310. J. Tušek, Welding Journal, 75 (1996) 8, 41-4411. J. Tušek et al., Schweissen und Schneiden, 44 (1992) 7, 380-384Physical quantities / Popis fizikalnih veličinab - distance between two wires, mmbu - penetration width, mmd - wire diameter, mmhu - penetration depth, mmI - welding current, AL - electrode extension length, mmU - arc voltage, Vv - welding speed, m/minThe second wire, either in a twin-wire electrode or in atriple-wire electrode,  affects the penetration depth hu farless than the first one. The weld pool being formed underthe second wire, the arc is burning between the secondwire and the weld pool, while arc energy only partly pro-duces melting of the parent metal. The third wire contrib-utes to a greater penetration depth hu only with higherwelding speeds v, while with lower welding speeds v it hasno effect on the penetration depth hu (Figure 6.).CONCLUSIONSThe paper treats influences of welding parameters,modes of metal transfer through the arc and the functionof wires in multiple-wire welding in weld formation andthe final weld shape.Theoretical and practical investigations have confirmedsome known facts and permitted to draw some new con-clusions as follows:- direct melting of the parent metal can be obtained prac-tically only in multiple-wire welding or  multiple-elec-trode welding;- the first wire in triple-wire welding primarily affects thepenetration depth;- the second wire partly affects the penetration depth andpartly the penetration width;- in welding with the triple-wire electrode, the third wirein the welding direction practicallydoes not affect theweld depth but it affects the penetration width and fi-nally shapes the weld face.1    weld - single wirest1 cmFigure 6.Slika 6.Macro sections of welds; submerged arc welding with sin-gle-wire, twin-wire and triple-wire electrodes with con-stant welding speed and with the same welding para-meters per wire:  = 480 A /wire,  = 35 V,  = 0.7 m/min, wire  = 2 mm,  = 25 mmMakrobrušeni uzorci zavara, zavarenih jednostrI U vd Lukom, dvostrukom i trostrukom žičanom elektrodom pod pra-hom s konstantnom brzinom i jednakim parametrima za-varivanja na jednu žicu:  = 480 A/žici,  = 35 V,  = 0,7 m/min, žica  = 2 mm,  = 25 mmI U vd L2     weld - twin wirend1 cm3     weld - triple wireth1 cm

Faktori koji utječu na oblik zavara kod elektrolučnog zavarivanja trostrukom žičanom elektrodom

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