New single-layer and double-layer coatings of UONI-13/55 welding electrodes for welding low-carbon and low-alloy steels have been proposed. The coatings were applied with superfine ultradispersed opal-quartz-carbonate bentonite clay of the Taganskoye deposit of the East Kazakhstan region. Studies have confirmed that the use of new coatings can improve the welding and technological properties of electrodes and increase the strength and ductile characteristics, as well as the cold resistance of the deposited metal

A. V. Russakova

E. M. Azbanbayev

G. K. Daumova

N. V. Seraya

Yu. I. Lopukhov

English

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377METALURGIJA 60 (2021) 3-4, 377-380G. K. DAUMOVA, YU. I. LOPUKHOV, E. M. AZBANBAYEV, N. V. SERAYA, A. V. RUSSAKOVARESEARCH OF ULTRA-DISPERSED OPAL-QUARTZ-CARBONATE BENTONITE CLAY FOR COATING WELDING ELECTRODES  UONI-13/55Received – Primljeno: 2020-12-29Accepted – Prihvaćeno: 2021-04-10Preliminary Note – Prethodno priopćenjeG. K. Daumova, Yu. I. Lopukhov, N. V. Seraya. A. V. Russakova, D. Serikbayev East Kazakhstan Technical university, Ust-Kamenogorsk, KazakhstanE. M. Azbanbayev (eldar.imsc@gmail.com), «Kazakhstan Paramount Engineering» LLP, Nur-Sultan, KazakhstanNew single-layer and double-layer coatings of UONI-13/55 welding electrodes for welding low-carbon and low-al-loy steels have been proposed. The coatings were applied with superfine ultradispersed opal-quartz-carbonate bentonite clay of the Taganskoye deposit of the East Kazakhstan region. Studies have confirmed that the use of new coatings can improve the welding and technological properties of electrodes and increase the strength and ductile characteristics, as well as the cold resistance of the deposited metal.Keywords: welding electrode, coating, opal-quartz-carbonate bentonite clay, weld metal, mechanical propertiesINTRODUCTIONLow-hydrogen electrodes with the basic type of coating UONI-13/55 are used for the production of crit-ical and especially critical metal structures from low-carbon and low-alloy steels. The main disadvantages of the UONI-13/55 electrodes are: poor ionization of the arc gap, unstable arc burning, poor separability of the slag crust, increased spattering of the electrode metal, a tendency to form porosity during arc elongation, insta-bility of the mechanical properties of the weld metal, mainly impact toughness at low temperatures [1, 2]. The cold brittleness threshold of the metal of welds made with these electrodes is from –30 to –40 ° С. Un-stable burning of the welding arc during melting of electrodes with a basic coating is explained by the pres-ence of fluorine ions in the arc gap, which are arc deion-izers [3, 4]. However, calcium fluoride also has signifi-cant positive properties. It binds free hydrogen and wa-ter vapor into thermally stable hydrogen fluoride, and thus ensures the minimum hydrogen content in the de-posited metal in welding metallurgy [5]. In the coatings of most brands of low-hydrogen electrodes, the gas and slag-forming system CaF2–SiO2–TiO2 is used, in which the welding-technological properties of theelectrodes and the efficiency of protection of the molten metal are regulated by the CaCO3 / CaF2 ratio and the coating thickness [6]. With significant positive properties of electrodes with calcium fluoride coating, low techno-logical properties cause technological defects during ISSN 0543-5846METABK 60(3-4) 377-380 (2021)UDC – UDK 66.017:621.793:622.371/·378·362·37-549.74:535.82:620.17=111welding, which significantly reduce the quality and me-chanical characteristics of the weld metal.Therefore, finding coatings with improved mechanical and weld-ing-technological characteristics for low-hydrogen welding electrodes is an urgent problem. To manufacture electrode coatings for manual arc welding, a raw material base is used, such as mineral raw materials, ferroalloys, organic substances and arti-ficial chemical materials [7, 8].Currently, more and more research is being carried out to find cheap local raw materials suitable for the production of welding electrodes [9].EXPERIMENTAL PARTIn order to improve the complex of technological properties of low-hydrogen electrodes with a calcium fluoride coating, in particular, UONI-13/55 electrodes, while maintaining strength, plasticity and cold resist-ance properties, it is proposed to additionally introduce opal-quartz-carbonate bentonite clay of the Taganskoye deposit of the East Kazakhstan region into the standard coating formulation.Electron microscopic studies of the structure and el-emental composition of bentonites and deposited metal were conducted using the scanning electron microscope JSM-6390LV. Mechanical tests of the deposited samples were con-ducted according to GOST 6996-66 [10].Tensile and impact tests were conducted using TTM-1000 tensile testing machine (walter+bai, Switzerland) and PH-300-PS impact testing machine, respectively. Investigation of the welding and engineering prop-erties of the series K1 and K2 electrodes was conducted using direct current of reverse polarity from the VD-301 378G. K. DAUMOVA: RESEARCH OF ULTRA-DISPERSED OPAL-QUARTZ-CARBONATE BENTONITE CLAY... METALURGIJA 60 (2021) 3-4, 377-380power source, and K2 electrodes additionally using al-ternating current from the TD-300 welding transformer. The duration of short circuits was determined with the TX-5000 device when welding in the lower posi-tion.Test electrodes series were manufactured and tested, the base of coatings of which were marble, fluorspar, quartz sand. The total content of the main gas-slag-forming (CaCO3 and CaF2), as well as the ratio between them are shown in Table 1.- K1 - electrodes with a single-layer coating, con-taining a standard formulation of electrodes UONI-13/55, which was additionally injected with opal-quartz-carbonate bentonite clay of the 11th horizon of the Taganskoye deposit. Its elemental composition /wt%:  SiO2 – 51,98;  Al2O3  – 0,96;  Fe2O3 – 1,27;  CaO – 0,22;  MgO – 0,13;  K2O – 0,9; Na2O – 0,10; TiO2 – 0,10 [11]. - K2 - electrodes with a two-layer coating, where the standard formulation of the UONI- 13/55 electrodes was used as the first layer. For the second outer layer, opal-quartz-carbonate bentonite clay of the 11th hori-zon of the Taganskoye deposit was also used [12].Ferroalloys of industrial production were used as de-oxidizers: electric furnace medium-carbon ferromanga-nese (84-85 /wt% Mn), lump ferrosilicon with 44-45 /wt. % Si), as well as ferrotitanium (35/wt% Ti/ 5 wt% Si, and 8/ wt% Al).RESULTS AND DISCUSSIONAs follows from Table 1, in the K1 and K2 series coatings, the gas-slag-forming base, dimensional and en-gineering parameters of the coating of the UONI-13/55 electrodes are reproduced. In them, the CaCO3/CaF2 ratio is 3/1; therefore, there is a high oxidation potential, rather effective protection of molten metal from air, and fine-droplet transfer of electrode metal. In the coating of K2 series electrodes, the CaCO3/CaF2 ratio is 3,5/1, and therefore its oxidation potential increases significantly.To make the K1 series electrodes additional intro-duction of dried opal-quartz-carbonate clay ground to an ultradispersed state into the standard mixture of the coating components of the UONI 13/55 electrodes is required. The high ductility of bentonite leads to a sig-nificant increase in the ductile properties and quality of the coating.All components were mixed with liquid glass and applied by pressing onto metal rods made of Sv08A wire. The test coating is characterized by good ductile properties, uniformity over the entire surface of the electrode, retains its quality after calcination at T 300 ... 35 °С and meets the requirements of GOST 9466-75 [13], GOST 9467-75 [14].To make the K2 series electrodes bentonite clay was preliminarily subjected to super-grin-ding in a vibrating mill [15] and mixed with water glass, and then applied to the first dried layer by pressing onto a standard elec-trodelayer by pressing onto a standard electrode coating UONI-13/55.When the tip of the electrode burns, the activating properties of superfine bentonite at the level of nano-particles increase and the electronegative ions formed in the vapor, mixing with the positive ions of the slag-forming and gas-forming components, contract (com-press) the column of the welding arc due to electrody-namic forces. In this case, the active section of the arc column decreases, and the current density in the arc in-creases. This allows to increase the penetration depth of the welded metal and increase the productivity of the welding process. As a result, arc constriction and pene-tration and hence the productivity of the welding pro-cess will increase.The test results indicate that the experimental series of electrodes are characterized by fine-droplet transfer of electrode metal, negligible spatter, and good protec-tion of the welding zone from the surrounding atmos-phere (Table 2).Electron-microscopic studies of the deposited metal show that in the deposited metal of the test electrodes K1, K2, in comparison with UONI-13/55, a higher con-tent of deoxidizing elements Mn, Si, Ti with an addi-tional presence of Al, which has passed from the ben-tonite of the coating of the test electrodes (Figures 1, 2, Table 1 Base of coatings, dimensional and technological indicators of experimental electrodesTest electrode SeriesMass fraction of coating Dcoat./drod/ mm Coating mass  coefficient/%Slag protection  coefficient/%CaCO3 CaF2 CaCO3/CaF2К1 54 15 3 /1 1,50 54,3 25К2 54 15 3,4/1 1,72 56,2 27Table 2 Welding and engineering properties of electrodesElectrodeseriesCurrent typeand polaritySlag crust separabilityBead formationand surfaceShort circuitduration τs.c/msPenetrationdepth/ mmSplashing Pore tendency in arc lengtheningUONI- 13/55 Direct, reverse Satisfactory Satisfactory 3,7 2,5..2,8 Excessive Excessive (∆Larc>3,5 mm)К1 Direct, reverse Excellent Excellent,  fine-scaled2,7 3…3,5 Negligible None (∆Larc≤6 mm)К2 Alternating, direct reverseExcellent Excellent,  fine-scaled2,2 4...4,5 Small None (∆Larc≤7 mm)379G. K. DAUMOVA: RESEARCH OF ULTRA-DISPERSED OPAL-QUARTZ-CARBONATE BENTONITE CLAY...METALURGIJA 60 (2021) 3-4, 377-3803). At the same time, the oxygen content in the depos-ited metal in the K1 and K2 electrodes is noticeably re-duced relative to the UONI-13/55 electrodes. In this case, the main source of oxygen is non-metallic inclu-sions that did not have time to escape into the slag, which are formed at the stage of crystallization of the weld pool (Figure 3).Chemical composition of the deposited metal corre-sponds to standard electrodes (Table 3).In the study of the macrostructure of welded sam-ples, it was found that the melting depth of metal weld-ed by standard electrodes without an external layer of activating components was 2,5...2,8 mm, and the smelt-ing of samples welded by an experimental electrode Figure 1  Point scanning of the elemental composition of the deposited metal of the K1 electrodesFigure 2 Point scanning of the elemental composition of the deposited metal of the K2 electrodesFigure 3 Point scanning of the elemental composition of the deposited metal of the UONI-13/55 electrodesTable 3 Chemical composition of the deposited metal/wt%Type of  electrodeChemical compositionC K Si S PUONI- 13/55 0,08 – 0,13 0,8 – 1,2 0,20-0,45 0,030 0,035K1 0,062 1,25 0,35 0,020 0,023K2 0,062 1,27 0,32 0,020 0,026with a layer of activating components applied to the sur-face of the smear, the layer of slag-forming and gas-forming components was 4...4,5 mm. This indicates an increase in the smelting capacity of welding arc of the recommended electrode by 60%, which improves the performance of manual arc welding and energy savings at the expense of counter-reaction of the welding arc.380G. K. DAUMOVA: RESEARCH OF ULTRA-DISPERSED OPAL-QUARTZ-CARBONATE BENTONITE CLAY... METALURGIJA 60 (2021) 3-4, 377-380Comparative mechanical properties of the cladded metal of experimental and manufactured according to the standard formulation of UONI- 13/55 electrodes show a slight increase in their strength and ductile prop-erties. However, the values of impact strength of the melted metal of the experimental electrodes significant-ly exceed these indicators of UONI-13/55 electrodes at both positive and negative temperatures (Table 4).СONCLUSIONWhen welding with UONI-13/55 electrodes, the welding zone, due to its low technological properties, is insufficiently protected from the ambient air, and the deposited metal has a low impact strength at T – 60 °C. Under welding conditions, the main deoxidizers of Mn, Si and Ti, such as a deoxidizer and a nitride former, do not fully provide an increase in toughness.The addition of opal-quartz-carbonate bentonite clay of the Taganskoye deposit of the East Kazakhstan region with a single-layer and two-layer coating into the composition of new electrode coatings UONI-13/55 ad-ditionally makes it possible to improve the welding and engineering properties of the gas-slag base of the coat-ing, which helps to increase the protective functions of the welding zone from the surrounding atmosphere and an increase in the impact strength of the weld metal at temperatures of +20 °С and at negative temperatures, including –60 °С due to additional deoxidation of Al. REFERENCES[1] S.˝V. Mikhailitsyn, M. A. Sheksheev, S. I. Platov, A. N. Emelyushin, S.V. Naumov, Investigation of viscosity of liquid welding slags and melts of electrode coatings. Izve-stiya Vysshikh Uchebnykh Zavedenij. Chernaya Metallur-giya 61 (2018) 4, 280-287[2] D. P. Ii’yashchenko, S. B. Sapozhkov, Splashing in manual arc coated electrode welding and methods of reducing splashing. Welding International 22 (2008) 12, 874-877. https://doi:10.1080/09507110802650677[3] K. D. Basiev, G. V. Rukhlin, A.M. Baimatov, Plasticising and stabilising components in coatings of basic electrodes. Welding International 17 (2003) 9, 739-740. http://doi:10.1533/wint.2003.3191[4] K. C. Mills, B. J. Keene, Physicochemical properties of molten CaF2 - based slags. International Metals Reviews, 26 (1981) 1, 21-69. http: doi:10.1179/imtr.1981.26.1.2[5] A. E. Marchenko, N. V. Skorina Influence of technological factors in manufacture of low-hydrogen electrodes on hydrogen content in the deposited metal. The Paton Wel-ding Journal (2013) 8, 13-24[6] V. D. Makarenko, C. P. Shatilo Stability of arcing in wel-ding with calcium fluoride electrodes. 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Adilkanova Experimental studies on wastewater sorption treatment with subsequent disposal of used sorbents, Che-mical engineering transactions (2018) 70, 2125-2130. https://doi:10.3303/CET1870355Note:  The responsible translator for English language is Y.S. Ruleva, Ust-Kamenogorsk, KazakhstanTable 4  Comparative mechanical properties of the melted metal obtained using experimental and standard UONI-13/55 electrodesTestand standardelectrodes seriesYield strengthRn/MPaUltimate ten-sile strength Rm/MPaElongationδ А/ %Reductionof areaZ/ %Impact strength KСV at Е = 300 J (J/cm2)  at temperature/°С+20 –20 –40 –60К1- de 3mm 415 545 32 77,6 262,6 225,6 129,6 42К2- de 4mm 415 540 32,5 78 250,6 220,6 130 37UONI 13/55 de 4mm 395 520 28,5 72 200 140 115 28

Research of ultra-dispersed opal-quartz-carbonate bentonite clay for coating welding electrodes UONI-13/55

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