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Section 8. Machinery construction
Section 8. Machinery construction
Ermatov Ziyadulla Dosmatovich, senior lecturer of technological machines and equipment department
Tashkent State Technical University E-mail: ermatov-ziyadulla@rambler.ru Dunyashin Nikolay Sergeevich, head of technological machines and equipment department, senior lecturer, candidate of engineering sciences Tashkent State Technical University E-mail: dunjashin-nikolajj@rambler.ru
DEVELOPMENT OF ELECTRODES FOR SHIELDED METAL ARC WELDING BASED ON THE CLASSIFICATION OF THE COATING CHARGE COMPONENTS
Abstract: The article provides classification of the charging materials of electrodes for shielded metal arc welding that allows the initial analysis of the charging mixture of welding materials for further researches.
Keywords: electrode, shielded metal arc welding, classification, nanomaterial, minal, potassium fluorozirconate.
Welding is an important industry that produces more than half of the gross national product in industrialized countries. Today, the domestic market of welding materials has a high share of imported electrodes due to the need to transport raw materials to electrode factories, including importation of raw materials from neighboring countries and beyond, deterioration in product quality, shortage of traditional welding materials, and high prices. Basic ideas of electrode selection for shielded metal arc welding are determined by the following conditions [1-3]:
- absence of hot and cold cracks;
- absence of pores and slag inclusions or their minimal size and quantity per unit length of the weld, which are reasonable and permitted for specific products or operating conditions;
- special properties of the weld metal;
- package and level of mechanical properties of the weld metal in combination with the metal of the welding parts;
- adaptability properties of the electrodes, such as their versatility, suitability for use in specified climatic conditions;
- satisfactory sanitary and hygienic properties of the electrodes (welder safety and health).
These conditions are fulfilled by selection of the appropriate electrode rod and components of the electrode coating. Modern electrode coatings are complex multicomponent systems. Materials of electrode coatings have a variety of metallurgical and technological functions [2-4].
Production of electrode coating for shielded metal arc welding uses the raw materials, which can be conventionally divided into: mineral raw materials, ferroalloys, deoxidation metals, alloying metals and modification of the weld metal, organic materials and synthetic chemical materials.
The initial analysis of the charging materials in electrode coatings used for shielded metal arc welding is carried out according to the following classification:
1) Pure metals (iron powder, electrolytic copper powder, aluminum powder, molybdenum powder, nickel powder, titanium powder, manganese metal, tungsten metal);
2) Ferroalloys (ferroboron, ferrovanadium, ferromolyb-denum, ferrochrome, ferroroaluminium, ferrotitanium, fer-rosilicon, ferromanganese);
3) Mineral raw materials (carbonates, titanium-containing materials, aluminum silicates, fluorine-containing raw materials, silicates, quartz materials, iron and manganese ores);
4) Synthetic chemicals (fluorine-containing materials, chlorine-containing materials, carbonates, oxides);
5) Organic materials (cellulose electrode, carboxymethyl cellulose, starch, dextrin, dextrinol, wood flour).
The minerals and raw materials used for production of welding electrodes can be divided according to their purpose into the following groups: slag-forming, gas-forming, alloying, stabilizing, deoxidizing, plasticizing and binding. The components of the charging mixture of mineral raw materials for
DEVELOPMENT OF ELECTRODES FOR SHIELDED METAL ARC WELDING BASED ON THE CLASSIFICATION OF THE COATING CHARGE COMPONENTS
the production of welding materials are limited on the basis of phosphorus and sulfur content.
Addition of the ultra-disperse components in the composition of welding materials can be helpful to obtain electrode coatings with optimal structures, which provide a more efficient use of welding materials components. The optimum temperature during electrode manufactures using nanomate-rial can adjust the water content and hydroxyl groups in the composition of welding materials that affect the porosity of the weld metal, the content of hydrogen in it and the strength performance characteristics of welded products.
One of the issues solved in this article is the introduction of small amounts of alloying elements into the components of welding materials, such as rare-earth elements, zirconium, etc. to improve the welding and technological characteristics of the weld. For this purpose, the distribution ofthese elements should be as uniform as possible throughout the entire welding electrode coating. Such a distribution in practice could not be achieved with the introduction ofsmall additives ofthe necessary elements directly into the coating composition; therefore, the transition to the composition of the weld metal is also not uniform.
Introduction of alloying elements to the coating was carried out by the method of obtaining fused components -minals that contain alloying elements among other elements. We used the purified components during the minal melting, as well as oxides of rare-earth elements as a source of alloying elements. This method provides homogeneous products, their low reactivity to liquid glass and easy addition of small amounts of alloying elements.
The composition of the electrode coating is, by wt.%: marble: 52-60; quartz sand: 8-11; fluorspar: 17-21; upgraded kaolin: 3.8-5.4, soda: 1.5-1.9; electrode cellulose 0.8-1.6; potassium hexafluorozirconate (VI): 12.5-18.9; ferromanganese: 1.9-2.1; ferrosilicon: 3.2-3.8; ferrotita-nium: 11.0-15.0.
The procedure that causes positive changes consists of refining the weld metal by sulfur and phosphorus, by creating harmless compounds with them: zirconium phosphorous and zirconium sulfurous, which deposits as molten slag.
Introduction to the composition of the electrode coating of less than 12.5 wt.% potassium hexafluorozirconate (VI) does not increase the impact hardness of the weld metal, since this amount is not enough to achieve the desired level of activity of the welding slag which causes purifying reaction. Increase in K2ZrF6 content above 18.9% sharply affects the welding and technological properties of the coating. Surface of electrode coating is flat, smooth, and has no defects. Coating strength was determined by applying impact force: electrodes were thrown from a certain height on the concrete surface with no chipping of coating detected. Therefore, manufactured welding electrodes have the required coating quality, uniform distribution of components and the absence of defects. It indicates the quality of the mineral raw materials used in the coating composition. Welding using these electrodes is performed with direct current of reverse polarity and alternating current. Productivity (for diameter of 4.0 mm) 10.5 g/Ah; 1.6 kg/h. Electrode consumption per 1 kg of weld metal is 1.8 kg.
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