The objective of this paper is the analysis and evaluation of the quality of the new flux-cored wire designed for the MAG welding process that was developed and produced using special laboratory equipment. Experimental welding was performed with the new activated flux-cored wire and classic solid wire with changing of welding parameters and shielding gas composition (100 % CO2 and gas mixtures of Ar + CO2 + O2)

D. Bajić

D. Veljić

M. Rakin

N. Bajić

English

Hrčak - Portal of scientific journals of Croatia

453METALURGIJA 52 (2013) 4, 453-456N. BAJIĆ, D. BAJIĆ, D. VELJIĆ, M. RAKINADVANTAGE OF USE OF ACTIVATED FLUX-CORED WIRE INSTEAD OF SOLID WIRE WITH THE MAG WELDING PROCESS FROM THE MECHANICAL PROPERTIES ASPECT Received – Prispjelo: 2013-01-21Accepted – Prihvaćeno: 2013-04-15Original Scientifi c Paper – Izvorni znanstveni radISSN 0543-5846METABK 52(4) 453-456 (2013)UDC – UDK 621.791.052:621-426:536.1=111N. Bajic, Techno-experts d.o.o – Research and Development Center, Ser-bia, D. Bajic, University of Montenegro, Faculty of Mechanical Engi-neering, D. Veljic, Techno-experts d.o.o – Research and Development Center, Serbia, Marko Rakin, University of Belgrade, Faculty of Tech-nology and MetallurgyThe objective of this paper is the analysis and evaluation of the quality of the new fl ux-cored wire designed for the MAG welding process that was developed and produced using special laboratory equipment. Experimental weld-ing was performed with the new activated fl ux-cored wire and classic solid wire with changing of welding param-eters and shielding gas composition (100 % CO2 and gas mixtures of Ar + CO2 + O2).Key words: welding, electrode, activated fl ux-cored wire, solid wire, heat aff ected zoneINTRODUCTIONThe MAG – process is widely used for welding of constructions made of carbon and low alloyed steels, due to a number of advantages compared to similar processes [1-3]. Melting of the wire electrode and the transfer of droplets through the electric arc depend on the shielding environment, parameters of the welding process (current power, voltage, polarity), chemical composition and diameter of the wire [1-6].Besides positive outlined features the MAG process has some technological limitations when welding with wire of more than 2,0 mm in diameter and drawbacks such as intense splatter and unsatisfactory shape of weld metal. Eliminating these defi ciencies in the MAG weld-ing process is possible in two ways. The fi rst is to re-place the shielding CO2 gas with an optima two ways. The fi rst is to replace the shielding CO2 gas with an op-timal composition of a gas mixture, and the second is the development of a new quality of fi ller, primarily, different qualities and forms of fl ux-cored wires.Numerous investigations have indicated the possi-bility of replacing CO2 with a gas mixture (Ar + CO2 + O2) which improves the quality of the welded joints and reliability of the welded constructions. Similar effects, can be achieved by using the new quality activated fl ux-cored wire which compared to the classical solid wire represents signifi cant technological progress [1-5].The main goal of this paper is to, based on mechani-cal properties of welded joints, determine the positive effects and advantages for justifi ed use of activated fl ux-cored wire in relation to use of classical solid cross section wire [5, 7-12].EXPERIMENTAL WORKFor experimental welding boiler plate was chosen as the base metal, two fi llers (standard solid and activated fl ux-cored wire) CO2 shielding and several systems of gas mixtures (Ar + CO2 + O2) [5, 8, 12].In the fi rst part of the preliminary experiments de-fi ned were the optimal energy parameters of root weld-ing and groove fi lling with solid or activated fl ux-cored wire in CO2 shielding, provided that the heat input was in the interval from 1,0 to 1,1 KJ/mm. The share per-centage of singular components in the mixture was changed on two levels.Base metal and fi llersThe base metal chosen for experimental welding was in the shape of a strip marked Č. 1204, 12 mm thick [4]. The chemical composition and mechanical proper-ties of the chosen base metal according to the certifi cate of the producer, Iron Mill Skopje, are given in Table 1.Table 1  Chemical composition and mechanical properties of the base metal Č. 1204 / wt. %C Mn Si P S0,19 0,55 0,21 0,013 0,025Mechanical propertiesTensile strength / MPaYield strength / MPaElongation / % Toughness / KV (J)500 310 31 93 - 100The fi ller chosen for the experimental MAG welding process was in two metallurgical qualities of which the fi rst is in the form of activated fl ux-cored wire a diam-eter of 1,2 mm marked FW-10 (producer: “Paton” Insti-454  METALURGIJA 52 (2013) 4, 453-456N. BAJIĆ et al.: ADVANTAGE OF USE OF ACTIVATED FLUX-CORED WIRE INSTEAD OF SOLID WIRE...tute, Kiev, Ukraine, internal marking AP-AN10), and the second quality is a standard solid wire marked SW-60 (producer Zeljezara, Jesenice, marked VAC-60). The chemical composition and mechanical properties of the pure weld metal, according to producer's data are given in Table 2.Cut base metal plates for experimental welding size: 300 x 150 x 12 mm were cut from a metal sheet so that the longer end is in the direction of rolling achieving that after welding the position of specimens, for me-chanical testing of welded joints, have a transverse di-rection to the rolling direction of the steel strips [4-8]. After cutting the obtained plates, along one longer side are mechanically processed and brought to an angle of 60º (JUS C.T3.061).Table 2  Chemical composition and mechanical properties of pure weld metal / wt. %Filler C Mn Si Ti P SFW-10 0,08 l,50 0,50 0,045 0,025 0,023SW-60 0,1 1,45 0,90 - - -Mechanical propertiesFillerTensile strength / MPaYield strength / MPaElonga-tion / %Toughness / KV (J)+ 20 °C - 40 °CFW-10 620 520 25 120 42SW-60 590 490 22 80 38Experimental weldingThe experimental welding of prepared specimens was carried out using the MAG device LAH 320 –ESAB in CO2 shielding and a gas mixture (Ar + CO2 + O2) formed using gas mixer type Wedmix. Table 3 shows the sequence of carrying out of experimental welding.Table 3  Experimental welding sequence, with solid SW-60 and fl ux cored FW-10 wire in various shielding gas mixturesFiller Shielding gas compositionFW-10 SW-60 / % / % / %Specimen markingSpecimen marking Ar CO2 O21FW 1SW 70 25 52FW 2SW 56 39 53FW 3SW 66 26 94FW 4SW 52 39 95FW 5SW 61 32 76FW 6SW 61 32 77FW 7SW 0 100 0TESTING QUALITY OF WELDED JOINTSTensile strength and toughness testingFor tensile strength testing and the bending angle of the welded joint, fl at shaped specimens were prepared according to standard JUS C.T3.051. For toughness testing according to set standard a standard specimen with a “V” notch was prepared which was placed verti-cally along the weld metal axis of the welded joint.The tensile strength test results of welded joints (ac-cording to Table 3) that were done with solid wire qual-ity SW-60 and with fl ux-cored wire quality FW-10 are sown in the diagram Figure 1.Changes in value of toughness of welded joints at temperatures of + 20 °C and – 40 °C performed in gas mixtures shielding using activated fl ux-cored wire FW-10 and using solid wire SW-60 are shown in the dia-gram in Figure 2.Hardness testing of welded jointsHardness testing was performed according to Rock-well on samples for microscopic examination of welded joints as per JUS C.A4.003 standard. Locations where the test was performed are along the lines which go transversally (s) and vertically (v) on the welded joint, Figure 3.Regarding the base metal, in all the welded joints, a decline of hardness appears in the HAZ, and then in the weld metal hardness increases up to the axis of the weld metal and then decreases again towards the HAZ on the 500491495498488500497500482500491498 498487470475480485490495500505Tensile strenght / MPa 1 2 3 4 5 6 7Composition of shielding gas     SW     FW122122,8122112,5124,1117,5131,94341414041,242,853,7120129,5 131,9117,5127,9123,3137,442,853,745,131,540,541,146,3204060801001201401600 1 2 3 4 5 6 7 8Composition of shielding gas (Table 3)Toughness / JFW (+ 20 ºC) FW (- 40 ºC)SW (+ 20 ºC) SW (- 40 ºC)Figure 1  Changes in value of tensile strength of welded joints made using solid wire SW-60 and using fl ux-cored wire FW-10 in gas mixtures shieldingFigure 2  Changes of toughness depending on the test temperature of welded joints made using fl ux-cored wire FW-10 and using solid wire SW-60 in diff erent gas mixtures shielding455METALURGIJA 52 (2013) 4, 453-456N. BAJIĆ et al.: ADVANTAGE OF USE OF ACTIVATED FLUX-CORED WIRE INSTEAD OF SOLID WIRE...other side of the weld metal. There is a signifi cant in-crease in hardness in the weld metal made with FW-10 in comparison to specimens made using SW-60.Changes of hardness along the line that runs along the middle of the weld metal, for welds performed with fl ux-cored FW-10 are given in the diagram, Figure 4.In the diagram, Figure 5, shown are changes in hard-ness of welded joints of steel Č. 1204, made with solid wire SW-60.In the diagram, Figure 6, for welded joints made with solid wire SW-60 and fl ux-cored wire FW-10 in different gas mixtures, given are the changes of hard-ness values along the line which passes vertically in the middle of the weld metal from face to root.RESULTS AND DISCUSSIONThe fi llers of selected quality have tensile features beyond the features of the base metal Č.1204.The biggest difference between the hardness of base metal and weld metal was achieved in the weld metal made with fl ux-cored electrode wire (Ti alloy, which in the weld metal favors the formation of needle ferrite, particularly with increased Mn content in the weld met-al in the amount of ~ 1,5 %).Toughness results of the weld metal have shown that the greatest infl uence on toughness has the chemical composition of the base metal and then the burning of elements during welding.The results show that the best toughness at + 20 °C is achieved when welding with solid wire in a gas mix-ture in which the content of CO2 and O2 is at the lower level. However, the toughness at – 40 °C  was signifi -cantly higher when welding with activated fl ux-cored wire in a gas mixture in which CO2 and O2 content is also at the lower level.CONCLUSIONSOn the basis of obtained experimental results of in-fl uence of the composition of gas mixtures on the qual-ity of welded joints made with solid and activated fl ux-cored wire, the following conclusions can be made:1.  Using activated fl ux-cored wire instead of classi-cal solid wire an increase tensile strength and toughness at low temperatures.2.  It has been established that activated fl ux-cored wire retains all positive properties of wire with a full cross section along with the following improve-ments of welding-technological properties: easy S v 2 1 14016018020022024026014 12 10 8 6 4 2 0 2 4 6 8 10 12 14Distance from the weld metal axis / mmHardness / HV51FW2FW3FW4FW5FW6FW7FW15015516016517017518018519019520014 12 10 8 6 4 2 0 2 4 6 8 10 12 14Distance from the weld metal axis / mmHardness / HV51SW 2SW 3SW 4SW5SW 6SW 7SW1601802002202402602803003203403603804001 2 3 4 5 6 7 8 9 10 11 12 13Weld metal face measuring locations               (step 1,0 mm) weld metal rootHardness / HV51FW 2FW3FW 4FW5FW 6FW7FW 1SW2SW 3SW4SW 5SW6SW 7SWFigure 3  Layout of measuring points for hardness testing of welded jointsFigure 4  Changes of hardness of welded joints made with fl ux-cored wire FW-10 in diff erent gas mixtures shieldingFigure 5  Changes of hardness of welded joints made with solid wire SW-60 in diff erent gas mixtures shieldingFigure 6  Changes of hardness of weld metal (along the vertical line from face to root) made with electrode wires FW-10 and SW-60 in CO2 and gas mixtures shielding456  METALURGIJA 52 (2013) 4, 453-456N. BAJIĆ et al.: ADVANTAGE OF USE OF ACTIVATED FLUX-CORED WIRE INSTEAD OF SOLID WIRE...formation and stable burning of the arc, minimal splatter, a fl at and smooth weld metal surface, a gradual transition of the weld metal onto the base metal, secure penetration of the root, a satisfactory shape of weld metal in all spatial positions and easy separation of slag. By using activated fl ux-cored wire there is an increase in productivity up to 30 % compared to use of classical solid wire.3.  Replacing CO2 with an optimal gas mixture 70 % Ar + 25 % CO2 + 5 % O2 uring welding with classical solid wire led to the improvement of the quality of the welded joint and the processability of the MAG process.4.  The performed research has confi rmed that acti-vated fl ux-cored wire has numerous advantages compared to solid wire and can be recommended for semi-automatic, automatic and robotized welding in CO2 shielding.AcknowledgementThis work is supported by the Serbian Ministry of Science and Technological Development (project number TR 34016).REFERENCES[1] N. M. Voropaj, N.K. Kostenjek: Vlijanije sastava aktivira-noj provoloki na karakteristiki processa svarki v ugleksi-lom gaze, Naučno-tehničeskoj razdel, Kijev, 1986.[2] N. M.Voropaj, i dr.: Vzaimodejstvije rasplavljenogo meta-la s gazami i šlakom pri svarke v CO2 aktivi-rovanoj pro-voloki, Avtomatičeskaja svarka, 1986.[3] A. Radović, V. Grabulov: Quality improvement of welded joints of HIGH strehgth low-alloy steels using fl ux cored electrodes, International symposium –The days of wel-ding- Budva (1986), 51-53.[4] N. Bajić, V. Šijački-Žeravčić, S.Stojadinović, Poređenje kvaliteta zavarenih spojeva izvedenih MAG i E-postupci-ma, Zbornik radova Zavarivanje 96, (1996), 318-322.[5] N. Bajic, V. Sijacki-Zeravcic B. Bobic, D. Cikara, M. Ar-sić: Filler Metal Infl uence on Weld Metal Structure of Microalloyed Steel, Welding Journal, 90 (2011), 55-62.[6] N. Bajić, M. Simičić, B. Bobić, D. Veljić, B. Petrovski: Analysys of infl uence of fi ller metal composition on the quality of welded joints of microalloyed, II Međunarodni Kongres „Inženjerstvo, ekologija i materijali u procesnoj industriji“, BiH, Jahorina, mart, 2011, Zbornik radova, 1164-1175, CD[7] N. M. Ramini De Rissone, H. G. Svoboda, E. S. Surian, and L.A. De Vedia: Infl uence of Procedure Variables on C-Mn-Ni-Mo Metal Cored Wire Ferritic All-Weld Metal, Welding Journal, September 2005, 139-148.[8] N. Bajić, V. Šijački–Žeravčić, M. Rakin, K. Kovačević: Effect of Welding Regime and Filler Content on Structure of Microalloyed Nb/Ti Steel Weldments, Matеrials Scien-ce, 46 (2010) 1, 123-133. [9] M. A. Wahab, M. J. Painter: Numerical models of gas me-tal arc welds using experimentally determined weld pool shapes as the representation of the welding heat source. Int J Press Vess Pip 1997; 73:153-9.[10] R. C. Voight, C. R. Loper Jr.: A study of heat affected zone structure in ductile cast iron, Welding Journal 62 (1983), 82-88.[11] S. Aslanlar, A. Ogur, U. Ozsarac, E. Ilhan: Welding time effect on mechanical properties of automotive sheets in electrical resistance spot welding. Mater Design (2008); 29:1427-31.[12] J. Horvat, J. Prezelj, I. Polajner, M. Cudina: Monitoring Gas Metal Arc Welding Process by Using Audible Sound Signal, Strojniski vesnik-Journal of Mechanical Engineering 57(2011) 3, 267-278.Note:  The responsible translator of the English language is Teodora Kelic, IHIS - Research and Development Center a.d. Zemun, Serbia

Advantage of use of activated flux-cored wire instead of solid wire with the mag welding process from the mechanical properties aspect

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