DETERMINATION OF THE QUANTITIES FOR OBTAINING ELECTRODE COATINGS BASED ON LOCAL RAW MATERIALS

УДК 621.791

Abstract

This article investigates the determination of the optimal quantitative composition of electrode coatings for manual arc-welding electrodes produced on the basis of local raw materials. The reserves of key coating components — rutile, ferromanganese, ferrosilicon, marble powder, feldspar, mica, boron, starch, cellulose, and liquid glass — available within the country exceed 100 thousand tons, which substantiates the relevance of domestic electrode production. Through a series of laboratory experiments, the proportions of rutile and ferromanganese, and subsequently of ferrosilicon and feldspar, were systematically varied across ten coating formulations, and 2 mm, 3 mm, and 4 mm diameter electrodes were manufactured and tested for coating strength, electrode consumption, and weld-seam flatness. The results demonstrate that coating strength and weld-seam flatness improve as electrode diameter increases, while consumption decreases. The most optimal coating composition was established to contain 15% rutile, 18% ferromanganese, 19% ferrosilicon, and 11% feldspar, providing the highest strength, lowest consumption, and most even weld seam among all tested samples. The aim of this study was to determine the optimal quantitative composition of welding electrode coatings prepared from local raw materials, ensuring the highest coating strength, the lowest electrode consumption, and the most even weld seam.

Аннотация

В данной статье рассматривается определение оптимального количественного состава электродных покрытий для электродов ручной дуговой сварки, изготавливаемых на основе местного сырья. Запасы основных компонентов покрытия — рутила, ферромарганца, ферросилиция, мраморного порошка, полевого шпата, слюды, бора, крахмала, целлюлозы и жидкого стекла — имеющихся в стране, превышают 100 тысяч тонн, что обосновывает актуальность отечественного производства электродов. В ходе серии лабораторных экспериментов соотношения рутила и ферромарганца, а затем ферросилиция и полевого шпата систематически варьировались в десяти составах покрытий, и были изготовлены и испытаны электроды диаметром 2 мм, 3 мм и 4 мм на прочность покрытия, расход электрода и ровность сварного шва. Результаты показывают, что прочность покрытия и ровность сварного шва улучшаются с увеличением диаметра электрода, тогда как расход уменьшается. Установлено, что наиболее оптимальный состав покрытия содержит 15% рутила, 18% ферромарганца, 19% ферросилиция и 11% полевого шпата, обеспечивая наивысшую прочность, наименьший расход и наиболее ровный сварной шов среди всех испытанных образцов. Целью данного исследования являлось определение оптимального количественного состава покрытия сварочных электродов, изготавливаемых из местного сырья, обеспечивающего наивысшую прочность покрытия, минимальный расход электрода и наиболее ровный сварной шов.

Keywords: welding electrode, electrode coating, local raw materials, rutile, ferromanganese, ferrosilicon, coating strength, weld seam flatness

Ключевые слова: сварочный электрод, покрытие электрода, местное сырье, рутил, ферромарганец, ферросилиций, прочность покрытия, ровность сварного шва.

Introduction

A key factor in producing welding electrodes from local raw materials is the domestic availability of the components required for their manufacture. More than twenty types of welding electrodes exist, depending on the type and thickness of the materials being welded; for welding steel articles, three types are mainly used [4, 5].

The main coating components - ferromanganese, ferrosilicon, chalk/limestone, kaolin, cellulose, feldspar, talc, and liquid glass - are available domestically, with total reserves exceeding 100 thousand tons [1, 10]. This availability justifies developing competitive, resource-saving electrode production based on local raw materials. Accordingly, this study aimed to determine the optimal quantitative composition of electrode coatings from local raw materials that ensures maximum coating strength, minimum electrode consumption, and the most uniform weld seam.

Materials and methods

The procedure for conducting experiments on obtaining welding electrode components based on local raw materials is presented in detail in Section 2.5. At the outset of the research, laboratory experiments were carried out to determine the optimal proportions for obtaining welding electrode coatings. In doing so, the quantities of rutile (TiO₂), ferromanganese, and ferrosilicon - the components used in the largest amounts in obtaining the coatings - were varied. In the first series of experiments, the quantities of rutile and ferromanganese were varied while the remaining components were held constant, yielding the ten coating formulations shown in Table 1. From each of these 10 coating samples, 30 welding electrodes were prepared from steel wires of three different diameters (2 mm, 3 mm, and 4 mm) in accordance with GOST 2246–70 [7], and their coating strength, electrode consumption, and the evenness of the weld seam were examined in accordance with the classification requirements of GOST 9466-75 and ISO 2560 [4, 8].

Table 1. Composition of local products coating a single welding electrode, %

In the second series of experiments, based on the optimal coating composition identified from the first series, work was directed toward determining the optimal amounts of ferrosilicon and feldspar, a stabilizing substance, yielding the ten formulations shown in Table 2. The marble powder used as a slag-forming component met the requirements of GOST 4416–73 for welding-grade marble [6]. Here, too, on the basis of the compositions presented, 30 welding electrodes were prepared from steel wires of the same three diameters, and their coating strength, electrode consumption, and weld-seam flatness level were examined using the same procedure as in the first series.

Table 2. Composition of local products coating a single welding electrode, %

Results and discussion

The first series of experiments is presented in Table 3. As electrode diameter increases, coating strength increases, while consumption decreases and weld-seam flatness slightly decreases. For example, Sample 1 electrodes (2, 3, and 4 mm) show coating strengths of 91, 93, and 95%, respectively; consumption of 0.15, 0.11, and 0.07 units/cm; and weld-seam flatness of 95, 94, and 93%. The other samples follow the same pattern.

The best results are observed for Sample 5, which shows the lowest consumption, highest weld-seam flatness, and highest coating adhesion strength across all diameters. This indicates that the coating based on Sample 5 — containing 15% rutile and 18% ferromanganese — is the most optimal composition of the first series.

Table 3. Strength of electrode coatings, consumption of welding electrode, and flatness of the weld seam

The second series of experiments, using the optimal Series-1 composition as the base while varying ferrosilicon and feldspar, is presented in Table 4. As in the first series, coating strength increases with electrode diameter, while consumption decreases and weld-seam flatness slightly decreases, consistent with the heating and melting behavior reported for similar compositions [3]. For instance, Sample 1 electrodes (2, 3, and 4 mm) show coating strengths of 92, 94, and 95%, respectively; consumption of 0.14, 0.10, and 0.07 units/cm; and weld-seam flatness of 96, 93, and 92%. The other samples follow the same pattern.

The best results are observed for Sample 3, whose coating adhesion strength reaches 99, 100, and 100% for the 2, 3, and 4 mm electrodes, with the lowest consumption and highest weld-seam flatness among all samples.

Table 4. Strength of electrode coatings, consumption of welding electrode, and flatness of the weld seam

Based on the results of both series, consistent with electrode selection principles for similar local-raw-material systems [2], the coating used in Sample 3 of the second series can be considered optimal: it provides the highest strength, lowest consumption, and best weld-seam flatness among all tested samples, with a composition of 15% rutile, 18% ferromanganese, 19% ferrosilicon, and 11% feldspar. A decrease in the combined mass of these components below 63% negatively affects electrode strength.

The 12% total share of starch and cellulose supports stable arc burning: exceeding this amount slows melting at the electrode tip, while a lower amount reduces gas formation. The remaining components — TiO (3%), marble powder/CaCO₃ (8%), mica (6%), and boron (8%) — regulate wire melting, gas formation, and oxygen reduction during welding [6, 9, 11, 12], while also reinforcing electrode strength.

Conclusion

This research confirms that competitive welding electrodes can be produced from local Uzbek raw materials — rutile, ferromanganese, ferrosilicon, marble powder, feldspar, mica, boron, starch, cellulose, and liquid glass — with combined reserves exceeding 100 thousand tons. Sequential optimization identified the best coating composition as 15% rutile, 18% ferromanganese, 19% ferrosilicon, and 11% feldspar, giving the highest coating strength, lowest electrode consumption, and most even weld seam.

These four components must together make up at least 63% of the coating, while starch and cellulose should total about 12% to ensure stable arc burning without impairing melting or gas evolution. The remaining components — titanium(II) oxide, marble powder, mica, and boron — regulate wire melting, gas formation, and oxygen reduction, while strengthening the coating.

These results provide a basis for import-substituting, resource-saving electrode production from domestic raw materials and for further study of the resulting weld joints' properties.

References:

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