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The paper considers the peculiarities of damage to welded joints of steam pipelines that have been operated for a long time (more than 280 thousand hours) under creep and fatigue conditions. It is established that the damage caused by creep and fatigue depends to a large extent on the structural and phase state of the metal of welded joints, which changes considerably during their long-term operation. With longer service life of welded joints, a ferrite-carbide mixture forms in their structure as one of the components. The presence of such a mixture contributes to acceleration of damage of welded joints. The dependence of formation of the ferritecarbide mixture on the initial structure of welded joints was established, and recommendations were given for producing an initial structure with improved quality characteristics, which is advisable for increasing their reliability and service life. [ABSTRACT FROM AUTHOR]

This paper describes the method of shaping the product using 3D technology by means of applying arc heating and consumable material – a wire with a diameter of 1.2 mm. The aim of the work is to study the structure and mechanical properties of the product manufactured using additive 3D technology. Each deposited layer consists of three separate beads: two lateral ones, which provide the set contours of the layer, and one middle one, which fills the space between the two lateral ones. Electric arc surfacing was carried out with the help of a welding robot. The use of a robot made it possible to control the time between layer depositions, thereby controlling grain growth. Also, the use of a robot makes it possible to reproduce a set part as accurately as possible according to a pre-calculated and designed model with a minimum error of repetition of the torch movement of ±0.03 mm. As a result, the structure and mechanical properties of the deposited product were investigated. It is shown that the product manufactured according to the presented technology has a fine-grained ferrite-pearlite structure; the grain size ranges from 7 to 10 numbers. The mechanical properties along and across the deposited layers were studied. The indices practically do not differ. A comparison of their values with normative ones showed that they exceeded normative values by 10–50%. 14 Ref., 3 Tabl., 4 Fig. [ABSTRACT FROM AUTHOR]

The paper presents the main directions of development in the field of promising aluminium alloys. New generation alloys with improved chemical composition, technologies of production and heat treatment of semi-finished products are considered. The question of the relationship between the structure of the alloys and their operational properties, the influence of heat treatment modes and alloying on mechanical properties and weldability of aluminium alloys in order to obtain the specified predicted operational properties is highlighted. The results of the use of aluminium alloys in aviation and space technology are described. A review of industrial deformable alloys of Al-Li and Al-Cu-Mn system, and comparative characteristics of weldability of various promising aluminium alloys (1460, V-1469, 1201 and their analogues 2090, 2195, 2219) is conducted. 30 Ref., 1 Tabl. [ABSTRACT FROM AUTHOR]

Growing use of high-strength low-alloy steels in additive metal structure manufacture is accompanied by an increase in the requirements to the reliability of prediction results in the “composition-structure-properties” system. Application of fractal analysis methods allows establishing the metal structure characteristics by numerical parametrization, the metallographic analysis of which gives only a qualitative assessment. The paper shows the possibilities of fractal analysis for numerical evaluation of such characteristics of additive metal structure as the total length of grain boundaries, distribution of dislocations at the grain structural boundaries, distribution density of nonmetallic inclusion accumulations at a distance less than 5r from one another. Shown is the possibility of numerical parametrization of the structure and nonmetallic inclusions in the “structure-fractal-properties” system for predicting the mechanical properties of additive metal of high-strength low-alloy steel type. 7 Ref., 7 Tabl., 9 Fig. [ABSTRACT FROM AUTHOR]

The paper studies the effect of arc welding technological processes on the resistance of welded joints of scarcely alloyed atmosphere-resistant 06G2BDP steel to cold and hot cracks formation and brittle and fatigue fracture. With the help of the Implant method and using the technological Tekken sample, the conditions for cold cracks formation were evaluated and the methods of their elimination were recommended. It is shown that with the use of mechanized welding in shielding gases, solidsection and flux-cored wires provide high technological strength of welded joints in terms of hot cracks formation in a wide range of welding modes. On the other hand, when using coated electrodes, this range is narrowed, and at Vdef ≥ 20 mm/min, joints are prone to the formation of this defect. The results of studies on the evaluation of welded joints resistance to brittle fracture indicate high values of the stress intensity factor KQ for both the weld metal and HAZ metal. The endurance limit of T-joints when tested by cyclic loading was determined, which is [ σ ]-1 = 35 MPa. 15 Ref., 1 Tabl., 5 Fig. [ABSTRACT FROM AUTHOR]

The paper deals with application of welding and conducting repair-restoration operations in space, as well as evolution of the design of electron beam tool over several decades. Technical characteristics and technological capabilities of all the generations of hardware and requirements to it at different operation stages are described. Substantiation is provided for electron beam welding being the most suitable process for application under lower gravity conditions. Specification of “Vulcan” automatic unit is given, in which welding experiments were conducted for the first time in space. Specification of the versatile hand tool (VHT) is provided, and its capabilities are described during performance of operations of welding and other related technological processes, namely cutting, brazing, coating deposition and heat treatment, if required. Samples are shown, which were made when conducting the world’s first experiment in open space, when the cosmonaut-welders used VHT to perform the technological operations of welding, cutting, brazing and coating deposition. It is proved that generalization of investigation results and incorporating the experience of operation of all the previous samples of the hardware allowed development of the next “Universal” tool, which passed comprehensive testing at NASA, including in the KC-135 flying laboratory and in the space simulation test chamber. The paper presents new generation electron beam tool, which was developed and is manufactured at PWI. [ABSTRACT FROM AUTHOR]

Research papers devoted to development of laser-plasma processes during the last two decades are reviewed. It was found that the current directions of scientific research of the processes of laser-plasma welding are focused mainly on studying the peculiarities of joint impact of constricted arc plasma and laser radiation with wave length of 1.03 – 1.07 μm (first of all, fiber laser) on steels and alloys, as well as studying the physical fundamentals of manifestation of the synergic (hybrid) effect at such an impact and determination of the possibilities of its practical application. It was determined, in particular, that increase of the effectiveness of synergic effect manifestation is related to improvement of the plasma arc burning conditions in the zone of ionized vapour plume, which forms under the impact of focused laser radiation, as well as simplification of laser keyhole formation due to plasma arc pressure. Ref. 49, Fig. 9. [ABSTRACT FROM AUTHOR]

Application of artificial long lines in arc welding equipment is considered. These lines allow forming pulsed welding currents of a regulated shape. The need for such currents is determined primarily by the objectives of pulsed technologies, where the loading current shape ensures the required time law of power input into the technological object. The most characteristic examples of such technologies are pulsed laser welding, laser heat hardening, laser piercing of holes, etc. The possibility of adjustment of amplitude-time parameters of loading current pulses in a broad range allows determination and further on ensuring the optimal parameters of pulsed electrophysical processes in order to improve their quality and productivity. Special pulsed current generators are required to create such energy flows, which are described and proposed in the paper. Ref. 12, Fig. 6. [ABSTRACT FROM AUTHOR]

The objective of the paper is investigation of hygienic characteristics of harmful substances, which contaminate the air in continuous and pulsed flash-butt welding, to create the appropriate means for welder protection. Description of the methods of studying the chemical composition of welding fumes and gases, dispersed composition of the fumes and assessment of their influence on the welder body is given. It is found that flash-butt welding of R65 rails is accompanied by evolution of harmful substances into the working zone air in the form of fumes at the nanorange level, which are characterized by high biological activity. It is shown that fume toxicity at continuous and pulsed flashing belongs to a moderately dangerous class. The main elements, which determine the fume toxicity, are manganese and iron. It is found that in flash-butt welding the fumes are generated, which contain nanosized components of manganese and iron in concentrations, exceeding the calculated tentatively safe levels of human exposure. Performed studies showed that flash-butt welding is accompanied by generation of such toxic gases as nitrogen dioxide and carbon monoxide in the work place, in concentrations exceeding the limit permissible ones. Obtained results of comprehensive hygienic assessment of the fumes in flash-butt welding provided exhaustive information on the level of harmful influence of these fumes on the welder body. Ref. 20, Tabl. 5, Fig. 11. [ABSTRACT FROM AUTHOR]

The main direction of improving the operational characteristics of titanium alloys is the creation of heat resistant and high temperature titanium alloys. The high specific strength and corrosion resistance of this type of alloys, at temperatures up to 500…600 °С, enables making them the main structural material for aircraft and rocket engineering. However, their widespread use is associated with the problem of precipitation of brittle phases during welding, which requires the use of additional technological operations, such as local heat treatment or pre-heating. In this paper, the finite element modeling method was applied to study the influence of the TIG welding thermal cycle of the high temperature titanium alloy of Ti‒6.5Al‒5.3Zr‒2.2Sn‒0.6Mo‒0.5Nb‒0.75Si system with and without the use of pre-heating and to plot the cooling rates diagrams of the produced welded joints. Ref. 10, Tabl. 2, Fig. 12. [ABSTRACT FROM AUTHOR]

The paper gives the results of investigations on vacuum diffusion welding of МА2-1 magnesium alloy. Different technological measures were used in welding: unsupported welding, welding with application of forming matrices, welding without interlayers and with a zinc interlayer. It is found that it is not possible to produce the joint in unsupported welding without an interlayer at 400 °С temperature and process duration less than 60 min. Increase of welding temperature or time leads to considerable grain growth. Application of 250 ~m zinc interlayer and of the following welding mode: Т = 320 ºС, Р = 10 MPa, t = 30 min allows producing the joint. Analysis of chemical composition in different areas of the joint zone shows that development of diffusion processes in the butt during welding results in pore formation with magnesium content on the level of 17.8 – 20.12 wt. % in the zinc interlayer at 2 – 3 ~m distance from magnesium/zinc contact line. In the central part of the joint zone the metal chemical composition is close to pure zinc composition. Application of forming matrices and an interlayer of zinc in the solid-liquid state in welding in the following mode: Т = 340 ºС, Р = 10 MPa, t = 30 min. allows producing sound joints due to localisation of plastic deformation in the butt joint. Results of metallographic investigations showed formation in the butt joint of common grains and remains of the interlayer in the form of dispersed particles of 15…50 ~m size, with chemical composition of Mg–4.53Al–0.20Mn–63.49Zn, wt. %, having an irregular elongated shape. [ABSTRACT FROM AUTHOR]

The paper is devoted to making art products from low-carbon steel. Due to the peculiarities of the design of such products, configuration and relative position of permanent joints and their elements, application of electric arc welding technologies turns out to be limited. The advantages of electric arc braze-welding for making such structures are considered. A detailed description of the implementation of technological tasks, arising in manufacture of real sculptures made of steel, is given, namely joining continuous profiles, joining wire parts to a tube, joining a bundle of thin wires to a semisphere and joining wires of different diameters at sharp angles. A photo and characteristics of the sculptures made with application of TIG braze-welding are given. [ABSTRACT FROM AUTHOR]

Welding of living tissues replaces stitching of tissues with threads during surgical operations. It simplifies and shortens the time of operation performance, lowers their cost and probability of postoperative complications. Water makes up more than half of the biological tissues mass. During welding the melting stage is not clearly expressed. In the post-operative period the weld should be gradually replaced by a healthy tissue without loss of strength. Computer modeling greatly accelerates, simplifies and lowers the cost of studying the mechanical, electromagnetic and thermal processes, running in live tissue welding. Different mathematical packages allow modeling these processes simultaneously. The paper gives an example of mathematical modeling using the finite element method. Its application enables overcoming the difficulties, when studying the processes running in live tissue welding and allows using a 3D computer model, which models the processes of tissues compression and alternating current passage. [ABSTRACT FROM AUTHOR]

The paper presents the results of investigations of the strength, hardness and structure of butt joints on aluminium alloys of different alloying systems, produced by friction stir welding (FSW). It is shown that this process allows producing sound joints of aluminium alloys of different alloying systems, both in similar and dissimilar combinations. This is true not only for aluminium alloys made by casting by the standard technological scheme, but also for granulated alloys, containing the oversaturated solid solution of refractory transition metals, produced by powder metallurgy. It is found that the strength of welded joints produced at FSW of aluminium alloys, depends on the chemical compositions and mechanical properties of these alloys. Maximum ultimate strength is demonstrated by welded joints of the following high-strength alloys: 1995 (483 MPa), 1963 (473 MPa) and D16 (441 MPa), which is due to a slight degree of metal softening in the zone of thermomechanical impact (ZTMI), which is where the samples fail at mechanical stretching. Destruction of samples of welded joints of dissimilar aluminium alloys also runs in this zone or on its boundary with the heat-affected zone (HAZ) from the side of the softer alloy. Their ultimate strength is on the level of the joints of the respective similar alloys. It is shown that intensive plastic deformation of metal at FSW of dissimilar aluminium alloys results in formation of grains of practically globular shape in the weld nugget in the permanent joint zone, their size not exceeding 4 – 6 μm. In granulated alloy welding, the oversaturated solid solution is preserved in the granules, just their mechanical refinement takes place, resulting in a fine dense structure of the weld nugget, and the granules containing an oversaturated solid solution of refractory transition metals are uniformly distributed over the entire volume of the matrix in the weld metal. [ABSTRACT FROM AUTHOR]

The paper gives the results of investigations on fluxless brazing of АD1М, AMts (Al-Mn), AD31 (Al-Mg-Si) aluminium alloys (Al-Mg-Si) with application of Al-25Ge-5Si-5Cu-1.5Mn-0.15Ti brazing filler metal at the temperature of 550 ± 5 °С in the atmosphere of high-purity nitrogen. The results of high-temperature differential thermal analysis were used to determine the solidus and liquidus temperatures of the brazing filler metal. Thermal effects on the derived thermal curve are indicative of the presence of three phases, which correlates with the results of X-ray microprobe analysis. It is shown that the brazing filler metal structure in the initial state is formed by two solid solutions, based on α-Al and β-GeSi and eutectics. Mechanical testing revealed that the short-term strength of the brazed joints is higher than that of the base metal, and fracture occurs in AD1M alloy. Application of steplike cooling of AD31 alloy brazed joint with soaking at the temperature of 500 C promotes increase of shear strength from 84 to 102 MPa. 42 Ref., 1 Tabl., 7 Fig. [ABSTRACT FROM AUTHOR]

The paper presents the results of investigations on diffusion welding of high-temperature alloy EI437B, using foil from high-entropy alloy of CrMnFeCoNi system as an interlayer. The features of producing foil from high-entropy alloy and its main physical-chemical properties in as-rolled and as-annealed condition are given. Increase of the degree of the foil general deformation to 99.9 % results in up to three times increase of the yield limit, and further annealing of the foil leads to its lowering to values characteristic for EI437B alloy. During diffusion welding the Young’s modulus increased from 165 to 195 GPa in the joint zone corresponding to the high-entropy alloy, which may be indicative of a diffusion-induced redistribution of elements in the interlayer. Chemical element distribution in the joint zone is indicative of their sufficiently high diffusion mobility. It is shown that application of a high-entropy alloy interlayer in vacuum diffusion welding ensures formation of a diffusion zone of a rather homogeneous chemical composition with a monotonic nature of distribution of the main alloying elements. The thermo-deformational impact results in equalizing of the characteristics of hardness and modulus of elasticity in different regions of the joint, and their physical-mechanical properties become similar. [ABSTRACT FROM AUTHOR]

Application of high-strength titanium alloys in modern aircraft construction poses new challenges every year both to the developers of such alloys and to specialists in the field of joining materials. Wire Arc Additive Manufacturing (WAAM) is a highly promising technology, which allows manufacturing complex-shaped large-sized parts from high added value materials. This technology is part of additive manufacturing processes, which uses metal wires as filler materials and the arc - as the energy source. The paper shows the application of the developed experimental metal-cored wire based on a promising local high-strength titanium alloy T120 in multilayer argon-arc surfacing. The joint microstructure, its microhardness and mechanical properties were studied. [ABSTRACT FROM AUTHOR]

The paper deals with the results of studying the structure and strength of butt, overlap and fillet joints of AMg6M aluminium alloy, produced by friction stir welding (FSW). It is shown that a weld nugget with fi ne-crystalline structure forms as a result of intensive plastic deformation. The size of grains, which are of practically globular shape, does not exceed 4…5 ~m, and that of dispersed phase precipitates – ≤ 1 ~m. In the zone of thermomechanical impact, in addition to fi ne grains, somewhat larger elongated grains (6…7 мкм) form, which are oriented along the direction of plasticized metal displacement by the tool working surfaces. Here, in the heat-affected zone, where the metal did not undergo any deformational impact, the maximum size of its grains is on the level of 10…15 ~m. The strength limit of samples of butt joints and fillet joints, produced by making butt and overlap-butt welds, is on the level of 335 – 350 MPa at their static tension, and it practically does not depend on the welded sheet location either from the advancing side or from the retreating side, or on the weld orientation relative to their flanging direction. Here, the butt joint samples fail mainly through the base metal or the boundary of zones of thermomechanical and thermal impact. Samples of fillet joints produced by overlap-butt welds, fail in the zone of weld-to-base metal transition in the thermomechanical impact zone, and those produced by butt welds fail also through the base metal. 16 Ref., 1 Tabl., 10 Fig. [ABSTRACT FROM AUTHOR]

The paper gives the results of investigation of the features of formation of D16 aluminium alloy welds in consumable electrode welding with application of two insulated fi ller wires or embedded elements of diff erent chemical composition. Wires of Zv1201, ZvАК5, ZvАК12 grades of 1.6 mm diameter and embedded elements cut out of V92, V96 and 7056 alloy blanks with diff erent content of zinc were evaluated. It is shown that ZvАК5 wire ensures reduction of the length of solidifi cation cracks and quantity of pores in welded joints, and welded joint strength becomes higher at addition of zinc into the welds. 15 Ref., 5 Tabl., 5 Fig. [ABSTRACT FROM AUTHOR]

In the paper special attention is given to application of pulsed-arc tandem welding by coated electrodes. Mock-ups of equipment for tandem welding and surfacing were developed and studied. A scheme was proposed for tandem arc welding by stick coated electrodes, fi tted with capacitive energy storage devices, as well as a device-attachment that allows using any welding current source to perform this kind of welding operations. The attachment operation is based on the principle of controlling the electrode melting rate that ensures their uniform mutual burnout. Also shown are time diagrams, which clarify the principle of operation of the device, photos of surfaced samples, oscillograms of currents supplied to the welding electrodes. 7 Ref., 8 Fig. [ABSTRACT FROM AUTHOR]

The paper gives the results of studying [H]dif interaction in low-carbon metal, deposited by coated electrodes, with the dislocation structure of metal at plastic deformation during cooling in the range from 370 to 20 °С. [H]dif content was determined by thermodesorption analysis with chromatographic termination. [H]disl formation was found during deposited metal cooling at deformation temperature below 100 and up to 20 °С. Sample cooling method to determine [H]dif content corresponded to ІSO 3690 standard, and ensured [H]disl formation in the deposited metal. Metal alloying by nickel, chromium, and molybdenum leads to increase of [H]disl content. 21 Ref., 7 Tabl., 1 Fig. [ABSTRACT FROM AUTHOR]

The paper presents a review of studies on the influence of inoculation of dispersed refractory compounds into the weld pool on formation of weld metal microstructure in low-alloyed high-strength steels. Features of the process of primary structure formation are considered in the presence of refractory nonmetallic inclusions in the liquid metal, as well as on the interface of δ-dendrites and γ-phase. Possibilities of inoculant influence on the temperature range of bainite transformations, possibilities of formation of microstructural components with higher brittle fracture resistance, and improvement of weld metal toughness values are shown. 18 Ref., 5 Fig. [ABSTRACT FROM AUTHOR]

The paper deals with the features of laser welding with incomplete (non-through thickness) penetration of high-strength aluminium alloys of 7ххх series. It was found that at joining of 1.5 mm sheets by fibre laser welding to the depth of 0.5…0.7 mm there arises the risk of formation of pores, in particular, in the root zone, streaks of oxide film in the weld lower part, as well as hot cracks. The latter can be eliminated by reducing the heat input below 25 – 30 J/mm. The weld metal is characterized by an equiaxed finely dispersed structure with grain size of 10…15 ~m for 7005 alloy and 15…25 ~m for 7075 alloy. In the fusion zone, the grains are of an elongated shape with 2.5…3.0 coefficient for 7005 alloy and 2…5 for 7075 alloy. In the HAZ the grain length is reduced, the shape coefficient becomes 3…5 and 3.0…3.5 for 7005 and 7075 alloys, respectively. At performance of laser welding with small (~5 J/mm) values of the heat input, microhardness of the welds and HAZ is rather uniform, and close to that of the base metal. For 7075 alloy microhardness drop to 20% was observed in the fusion zone region, that is due to formation of grains of an elongated shape with shape coefficient of 2…5. The found drawbacks can be eliminated through reduction of pulsations of the vapour-gas channel with simultaneous increase of the stability of its existence and introduction of cathode breaking of the oxide film. [ABSTRACT FROM AUTHOR]

The paper is devoted to studying the technological features of plasma-arc spraying by consumable current-conducting wire-anode. The relevance of applying such a process is related to the possibility of spraying directly by atomization of wires without the need to make powders from them. Experimental verification of the results of mathematical prediction of the influence of annular protective flow of compressed air, accompanying the particle-loaded plasma jet, on the results of plasma-arc spraying by compact wire anodes was performed. The key role of increasing this flow rate above 20 m³/h for improvement of the spay-deposited coating formation and quality was established. In spraying of coatings from compact wires porosity decreased with increase of the values of flow rates of accompanying air flow G2, and achievement of this parameter values within 0.5…2.5 %. Conducted experiments allow producing porefree coatings in spraying with wires from М2 copper, Kh20N80 nichrome, NP1 nickel, AMg63 aluminium-magnesium alloy. Studying these experimental results showed that at increase of the rate of accompanying protective air flow G2 from 0 to 40 m³/h, the loss of alloying elements (С, Mn) during spraying by steels wires of 65G and 70 grades decreases by 30…40 % on average. Increase of the parameter of rate G2 of the air flow accompanying the particle-loaded plasma jet influences improvement of the coating adhesion strength and wear resistance. So, at G2 = 20…40 m³/h the adhesion strength at tearing off of coatings from steel 70 along the normal reaches 60…70 MPa, and that of coatings from М2 copper is 40…55 MPa. Wear resistance of coatings under the conditions of boundary friction and resistance at cavitation wear increases at G2 increase from 0 to 40 m3/h, which is manifested in reduction of such wear from 1.35 to 0.32 mg/min. 13 Ref., 9 Fig. [ABSTRACT FROM AUTHOR]

The paper confirms the presence of synergic effect at laser-plasma welding, using fiber laser, by comparing the cross-sectional areas of beads deposited in AISI 304 plate (δ = 4 мм) by laser, plasma, and hybrid processes at close power values of laser radiation and plasma arc (~2 kW each). It is determined that the manifestation of this effect depends on welding speed. At the speed of 2 m/min the hybrid bead cross-sectional area can exceed the sum of areas produced with the laser and plasma processes by up to 30%, and for the speed of 4 m/min by ~20 %. Comparison of input energy of the laser and hybrid processes of stainless steel welding showed that the difference between them depends on the welded sheet thickness (or penetration depth). This value first decreases from ~100 % for sheets with δ = 2 mm to 50 % for sheets with δ = 6 mm, and at further increase of penetration depth it rises to 60 %. The nature of dependencies of the factor of area ratio φ, weld geometry К and penetration depth Ф on the speed of hybrid welding of AISI 304 steel allows recommending the range of speeds of 1.5…2.0 m/min, as a more acceptable by the criteria of synergic effect and penetration depth. It is found that at hybrid welding with application of fiber laser radiation, the plasma component promotes elimination of such defects of weld upper bead formation, characteristic for laser welding, as undercuts and a ridge, etc. [ABSTRACT FROM AUTHOR]

The paper gives the results of measuring the characteristics of ultraviolet radiation in UV-C range at consumable electrode mechanized welding in a mixture of shielding gases. These studies were the base for issuing recommendations on protection of welders and auxiliary personnel, as well as personnel not performing welding operations directly. Recorded values of the intensity of radiation, reflected from the welding booth walls (0.03…0.17 W/m2), exceed the TLV of 0.001 W/m2, specified in SN 4557-88. Therefore, when working in a welding booth, it is necessary to take additional measures for protection of the back of the head and neck from exposure to reflected radiation. 8 Ref., 3 Tabl., 1 Fig. [ABSTRACT FROM AUTHOR]

Manufacture of parts by the method of 3D printing, in particular, applying FDM (Fusing Deposition Modeling) technology, is a promising trend in many branches of mechanical engineering, architecture, construction, medicine, etc. This range of problems challenges three main directions of studies: FDM 3D printing technology, materials science and mathematical modeling of processes for evaluation of functional qualities, in particular, strength of products. This work is devoted to the third direction: evaluation of stress-strain state of products manufactured by 3D printing using FDM technology. The paper considers three stages of solving this problem: 1 – mathematical formulation of the problem, which includes universal balance relations, determining equations of mechanical behaviour of the material; 2 – method of numerical solution of the problem; 3 – solving specific problems in order to determine patterns of thermomechanical processes and provide recommendations for technological parameters of 3D printing. 10 Ref., 12 Fig. [ABSTRACT FROM AUTHOR]

The paper presents the results of investigations of the process of formation of a gas-saturated layer on the weld surface at accidental violation of the conditions of argon protection (under the nozzle) in TIG welding of VT1-0 titanium. It was found that the change of oxygen content in argon of the protective nozzle in the range from 0.024 to 1.18 vol. % leads to a change of the colour of a region of forming weld surface. It is shown that each colour corresponds to a certain depth of the gas-saturated layer that can be up to 0.25 mm. A correlation dependence of weld surface colour – gas-saturated layer thickness – oxygen content in the protective nozzle was established. Results of gas analysis and mechanical testing of the welds show that oxygen and nitrogen from the air practically do not interact with the molten metal of the weld pool in the argon of the protective nozzle during welding. Therefore, the quantitative characteristics of the metal of welds are on the level of those of the metal of welds produced under standard conditions. To increase the operational reliability of welded assemblies with a coloured surface of a weld region, it is proposed to remove it, depending on its colour to the depth in the range from 0.10 up to 0.25 mm. 9 Ref., 2 Tabl., 6 Fig. [ABSTRACT FROM AUTHOR]

Ukrainian Society USNDT issued and is disseminating International Standard ISO 5817, concerning three levels D, C, B of welded joint quality, which has been applied by all the leading countries of the world since 2003 at mutual deliveries of welded metal structures. In Russia it is valid since 2009 р. Starting from 2019 all the metal structures made in Ukraine by arc welding methods should comply with STSU USNDT ISO 5817-2019 standard «Fusion-welded joints in steel, nickel, titanium and their alloys, quality levels (ISO 5817:2014, IDT) Kyiv, 2019. This standard is an identical translation of ISO 5817:2014 «Welding. Fusion – welded joints in steel, titanium and their alloys – Quality level for imperfections», adopted as DSTU ISO 5817:2016 by confi rmation method. The paper explains the importance of this standard, and gives a short table with admissible dimensions of surface defects for levels D, C, B. STSU USNDT ISO 5817-2019 standard is presented completely in USNDT site: www. usndt.com.ua. 6 Ref., 1 Tabl. [ABSTRACT FROM AUTHOR]

The paper presents the results of experimental studies performed with the aim of development of a high-efficient technology, equipment and special technological fixtures for restoration of worn teeth of coarse pitch helical gears by electroslag cladding (ESC). The main objectives of the work were development of the design and method of fabrication of a special water-cooled forming fixture, establishing ESC modes that guarantee fusion of the filler with the base metal, as well as sound formation of the working surfaces of clad teeth; adaptation of the assemblies of batch-produced machine A-535 UKhL4 with TShS 100-3 power source to perform consumable-nozzle ESC by 3 mm electrode wire, using AN-8 and AN-9U fused fluxes; restoration of a test-standard helical gear and assessment of its serviceability. The level of specific heat input that ensures sound teeth restoration was established; welding consumables were selected to ensure the required chemical composition and performance of the deposited metal. A special shop section was set up at repair-mechanical plant of TPA «Bratsk TIC» for restoration of the teeth of coarse pitch gears, where a gear was restored using ESC and sent for performance tests. Operation experience showed that the restored gear has good running smoothness and teeth resistance under the conditions of alternating and contact loads, arising at operation of the debarking drum. Teeth wear on the level of the generating circle is not more than 3 – 5 mm. [ABSTRACT FROM AUTHOR]

The paper deals with an important question which arises at designing and improvement of the structures of gas turbine engines, in order to increase the operating parameters, cost characteristics and competitiveness – welding of dissimilar, multi-structural high-temperature materials. Weldability assessment by the criteria of strength and crack resistance was performed. The main questions, arising in welding high-temperature nickel alloys in dissimilar combinations: welding method, features of weld formation, chemical composition and structure, cracking susceptibility of welded joints and mechanical properties, are considered in the case of welding typical high-temperature materials widely used in aircraft engine building, namely EI698VD and ZhS26VI alloys with polycrystal and single-crystal structure, respectively. Methods to control the technological strength are established. Mechanical properties of welded joints produced in the temperature range of 20…1000 °С by different technology schemes, are determined. [ABSTRACT FROM AUTHOR]

The paper presents the results of studying the features of weld formation at consumable electrode pulsed-arc welding of 4 mm AMg5M alloy in diff erent positions at the speed of 23 m/h. with forming backing element (FBE) and without it. It is shown that sound welds form irrespective of the angle of butt joint inclination relative to the horizontal plane. FBE presence increases the geometrical dimensions of weld made with consumable electrode by 4 – 12% on average, depending on the position of butt joints. Obtained data clearly demonstrates the possibility of achieving the required quality of welds and high level of mechanical properties in consumable electrode welding of aluminium-magnesium alloys at diff erent positions of the butt joints without FBE application. 6 Ref., 3 Tabl., 4 Fig. [ABSTRACT FROM AUTHOR]

The study of real operating conditions of the tuyere for oxygen blasting shows that in its head part, located near reaction zones of the converter, large thermal stresses arise caused by non-uniform heating of different parts of the unit. The nozzles of the head are intensively cooled by water and oxygen, and the tip of the tuyere, on the contrary, is heated by thermal radiation of the liquid metal pool. Namely, thermal stresses along with mechanical loads (reaction of the return effect from oxygen jets fl owing from the nozzles) cause premature destruction of the welds joining the tuyere nozzles with its tip. The need in developing electron beam welding of components of copper tuyeres is predetermined by disadvantages of using the traditional method of their welding – argon-arc method, which does not provide satisfactory properties of welded joints and their stability during operation of a product. The use of electron beam welding in the manufacture of tuyere heads for oxygen blasting allows increasing their service characteristics by alloying welding pool with the elements, having a deoxidizing effect on liquid copper. At the same time in order to increase the service life of tuyere heads it is necessary to reduce the level of thermal stresses in them. The latter becomes possible if the weld metal in terms of thermal conductivity is as close as possible to the base metal. The paper presents the results of mechanical tests of electron beam welded joints produced on M1 copper using different alloying inserts. On the basis of studies of microstructure and character of fractures of the modified electron beam welds, the influence of alloying inserts on their operational properties was established. Together with the specialists from the V. Bakul Institute for Superhard Materials of the NAS of Ukraine, a procedure for conducting investigations on thermal conductivity of welded joints was developed and measurements of thermal conductivity coefficients for the joints produced on M1 copper by AAW and EBW methods using alloying inserts was performed. Computer simulation of the temperature field arising in the areas of welded joints in the conditions of operation of copper tuyeres was also performed. [ABSTRACT FROM AUTHOR]

A new class of high-efficient arc welding equipment is proposed, which is based on wide application of capacitive energy storage systems, in which high-capacity capacitors with a double electric layer are used as such storages. The paper is a study of the structure of sources, which are based on switching-modulation conversion of welding current. Procedures of signal conversion in the proposed sources, using the charge transfer method are analyzed in detail. Analysis of dynamic characteristics of this type of sources was performed, and basic equations were derived, which characterize different types of capacitive welding current converters. [ABSTRACT FROM AUTHOR]

The paper presents the results of comparative studies of corrosion-mechanical resistance of welded joints of V1341 alloy 1.2 mm thick, produced by manual argon-arc welding with free and constricted arc, after different types of heat treatment (HT) – artificial aging and full cycle heat treatment (hardening and artificial aging). It was shown that artificial aging increases the strength characteristics of welded joints: those produced by free arc - by ~23%, compared to the base metal, by constricted arc – by ~29%, but reduces the relative elongation by ~82% and ~84%, and the strength coefficient – to 0.77 and 0.71 (0.81 and 0.83 in as-welded state), respectively. The full cycle of HT provides increase in both strength and ductility. After artificial aging, as well as after a complete heat treatment cycle, the potential difference between the base metal and the HAZ does not exceed the permissible value of 0.05 V (according to GOST 9.005), which will not be dangerous at operation in non-aggressive environments. Artificial aging and full HT cycle do not impair the resistance of welded joints of VB1341T alloy to exfoliating corrosion compared to as-welded state, which is assessed as value 2. An increase of resistance to intercrystalline corrosion (ICC) after artificial aging was demonstrated, the maximum depth of which was 0.301 mm for the joint produced by a free arc, and 0.233 mm – for a joint produced by a constricted arc (in as-welded state it was 0.350 mm and 0.47 mm, respectively). After a complete HT cycle, the ICC depth was 0.287 mm and 0.345 mm, respectively. Artificial aging reduces the corrosion-mechanical resistance of welded joints produced by free and constricted arc: the time to fracture of the samples was 9 and 12 days, respectively (compared to 45 days in as-welded state), but after a full cycle of HT maximum time to fracture of welded joints increased to 54 and 31 days, respectively. Welded joints produced by a constricted arc had higher corrosion-mechanical resistance after a complete heat treatment cycle. [ABSTRACT FROM AUTHOR]

The paper deals with the possibility of constructing mathematical models of the dependence of mechanical properties of silicon- manganese steels designed for ESW, which have high brittle fracture resistance in the HAZ, as well as of the overheated zone, on chemical composition. Data on mechanical properties of these steels were obtained as a result of studying the influence of additional alloying (microalloying) of silicon-manganese steel by manganese, chromium, vanadium, boron, cerium and zirconium on overheating resistance at electroslag welding. The method of multiple linear regression was used for construction of mathematical models. Mathematical models were constructed for the following set of base metal mechanical properties: impact toughness for temperatures of (+20, –40, –60, –70 °С), yield limit, ultimate strength, relative elongation and reduction in area. For overheated zone at electroslag welding mathematical models were constructed for impact toughness (KCU and KCV) for temperatures of +20, –60, –70 °С. Initial validation of the constructed models was performed. 9 Ref., 12 Tabl., 2 Fig. [ABSTRACT FROM AUTHOR]

The paper presents the results of mathematical modeling of the anisotropy of specific electric conductivity of soft biological tissue and investigates the difference between the results of the process of welding biological tissues produced without and taking into account the anisotropy of the specific electric conductivity of a biological tissue. The results of calculations of tissue resistance, current density and impedance dispersion are compared. 14 Ref., 1 Tabl., 10 Fig. [ABSTRACT FROM AUTHOR]

The paper presents the results of studies of corrosion and mechanical resistance of welded joints of V1341 alloy of 1.2 mm thickness, depending on the technology of manual argon arc welding with free and constricted arc. The strength coefficient of welded joints is 0.79 and 0.8, respectively. Potentiometric measurements showed an electrochemical heterogeneity between the base metal and welded joints obtained by free and constricted arc; with a potential difference equal to 100 mV and 86 mV, respectively. More positive potential is inherent to the region with a smaller weld area, which is safe for operation. Accelerated corrosion tests have determined that the shape of the arc column in manual welding does not affect the resistance of welded joints against exfoliating corrosion and against corrosion-mechanical breaking under conditions of constant deformation. The level of resistance of the base metal against exfoliating corrosion of the joints, produced by both types of arc welding technology, was estimated by number 2-3. The fracture time of specimens of the joints produced by free arc welding, decreased on average to 20 days compared to the base metal (73 days). Similar results were obtained for joints welded by a constricted arc. At the same time, it was found that using of a constricted arc for welding causes a lowering of the resistance of the joints against intergranular corrosion. The maximum breaking depth of grain boundaries for joints produced by a free arc is 0.350 mm, and for the joints made by a constricted arc it is 0.460 mm. [ABSTRACT FROM AUTHOR]

The paper presents the results of studying the mechanical properties of joints of 1460 alloy and joints of 1460 + 1201 dissimilar alloys, produced by EBW at room and cryogenic temperatures. It is shown that the strength of joints of 1460 alloy, welded using filler material from 1201 alloy at the temperature of 77 К rises by 10 %, and at the temperature of 20 К - by 20 %, compared with joints welded without filler. Mechanical properties of welded joints of 1460 + 1201 dissimilar alloys at testing temperatures of 20, 77 and 293 К are on the level not lower than those of the joints of 1460 alloy, welded with application of 1201 filler material. Welding technology is described and chemical composition of weld metal is given. [ABSTRACT FROM AUTHOR]

The paper gives the results of development and introduction of the technology of automatic arc surfacing of vertical embedded parts of navigation locks without dismantling them in the case of repair of rails of working paths of lift gates in the Kaniv navigation lock. [ABSTRACT FROM AUTHOR]

A wide range of parts and equipment of chemical, oil, agricultural, machine‑building, transport, energy and other industries are operated in abrasive conditions. In Ukraine, electric arc surfacing with flux‑cored wires of the Fe – Cr – B – C system is widely used to protect against abrasive wear and restore worn surfaces by surfacing. Such flux‑cored wires have a low cost and the deposited metal has a satisfactory wear resistance. However, the main disadvantage of the layers, deposited with such flux‑ cored wires are dendrites of the first and second order with acicular morphology. Sharp peaks of the solid phase act as stress concentrators, from which after impact the cracking of the deposited metal begins, followed by its chipping. It is known that the formation of rounded reinforcing phases reduces the concentration of stresses in the deposited layer and, as a consequence, increases wear resistance. This paper proposes the dispersion of structural components in the deposited metal by surfacing under the action of mechanical vibration on the deposited metal, which is especially useful for manufacture of surfacing bimetallic wear plates, and for large‑sized parts a dispersion of structural components in the deposited metal Fe – B – C is proposed by adding the powder of aluminum‑magnesium master alloy PAM‑4 to it. 5 Ref., 2 Tabl., 5 Fig. [ABSTRACT FROM AUTHOR]

Replacement of outdated technologies in the production of tubular parts is an urgent task. The paper presents the materials of carried out investigations on press welding of high‑load steel tubular parts with a diameter of up to 120 mm with a wall thickness of up to 6 mm, development of control system, metallographic and mechanical examinations on determination of the properties of welded joints. The main technological advantages of press welding of high‑loaded products are shown. 7 Ref., 3 Tabl., 6 Fig. [ABSTRACT FROM AUTHOR]

In the manufacture of thin-walled structures by welding, residual stresses appear in them, which negatively affect the geometric parameters and quality of the obtained products. The paper presents the results of evaluation of residual stresses on simulator-samples made from galvanized steel 08ps (semi-killed) after MAG welding, and plasma brazing using constant and modulated current. Lowering of residual stresses and avoidance of brazing filler metal spattering are promoted by reduction of heat input, when making permanent joints. One of the ways contributing to it, is application of plasma brazing, which provides the ability of setting the current, independently of filler material feed rate. Determination of the magnitude of residual stresses in the joints was performed by the magnetoelastic method. It is shown that in plasma brazing with constant current the dimensions of plastic deformation zone are much smaller than in MAG welding, which is associated with a decrease in the amount of thermal energy applied to the metal. Plasma brazing with constant current allows lowering residual stresses from 149, which is obtained by welding, to 119 MPa. Further decrease of residual stresses (to 85 MPa) during plasma brazing of joints of galvanized steel 08ps is possible due to the use of modulated current [ABSTRACT FROM AUTHOR]

The paper presents the results of heat treatment of welded joints of R65 rails from K76F steel, produced by flash-butt welding. It is shown that after pre-annealing of butt welded joints with further accelerated heating up to the temperature of heat treatment and quenching of the rail rolling surface by compressed air, the microstructure of welded butt joint metal changes, grain size is considerably refined, hardness across the HAZ width is increased, and deviation of metal hardness along the joint line from base metal level becomes smaller. [ABSTRACT FROM AUTHOR]

Welded joints of intermetallic β-stabilized alloy of TiAl system – Ti–44Al–5Nb–3Cr–1.5Zr (at. %) were investigated. Intermetallic blanks of 3 and 10 mm thickness were welded by electron beam welding. In order to prevent the occurrence of cold cracks in the welded joints of titanium aluminide samples of different thickness, the following post-welding local heat treatment using an electron beam was performed. This method of processing is one of the most attractive for improving the structure of the ingot and reducing the level of residual welding stresses, which, in its turn, significantly increases the mechanical properties of the alloy. Static tensile tests were performed to assess the strength of welded joints. The samples failed in the base material. The paper presents histograms showing the values of tensile strength (σt) of welded joints obtained during tensile test for samples of different thickness with and without LHT application. It is shown that the use of local heat treatment increases the tensile strength of samples of 3 and 10 mm thickness by 1.8 times, compared with samples produced without LHT. In addition, the values of this characteristic for welded joints of different thicknesses, which are obtained using this technique, are quite uniform. Comparative analysis of the results of tensile tests and the results of microhardness studies was performed, which showed that destruction of the samples took place in the zone of lowering of mechanical properties. The nature of fractures of different parts of the welded joint was studied, which confirmed that fracture occurs in the zone of brittle part of the sample. It is known that mechanical properties of the welded joint are closely related to its structural state. During local heat treatment, an additional β0 (B2) phase appears in the structure, which increases the ductility of the weld material. [ABSTRACT FROM AUTHOR]

When creating new designs of aircraft gas turbine engines, the urgent task is to replace the mechanical fasteners of elements of a structure from high-temperature nickel superalloys (NSA) by welded joints. The paper presents the results of research on the processes of heating, deformation and formation of the structure of joints during friction welding (FW) of dissimilar alloys: granular alloy EP741NP with forged alloy EI698VD and cast alloy VZhL12U. The minimum values of pressure, at which the shortening is provided (deformation of workpieces in macrovolumes) were determined. A critical value of pressure was established, in excess of which there is a change in the nature of the shortening process in FW of alloys EP741NP and VZhL12U - from uniform to stepwise shortening of the workpieces. The range of change of the technological parameters of FW process is determined, in which formation of defect-free welded joints is ensured. Microhardness studies showed absence of areas with reduced microhardness values in the zone of FW joints of EP741NP and VZhL12U alloys. [ABSTRACT FROM AUTHOR]

The paper gives the results of studying the effect of various heat treatment operations on the structure and mechanical properties of the base metal and welded joints of sheet aluminium alloy of V1341 grade 1.2 mm thick, produced by manual nonconsumable electrode argon-arc welding. The dependence is established between the structural state of the metal of welded joints of this alloy on the kind of heat treatment that affects the level of strength and ductility. A significant effect of improvement of the structure and mechanical properties is achieved, when conducting complete heat treatment, which includes quenching and artificial ageing of the alloy and its joints. Compared to artificial ageing modes, this kind of heat treatment allows producing a stable metal structure, characterized by smaller dimensions of phase precipitates and inclusions, that promotes increase of the strength level, under the condition of preservation of the ductility values. [ABSTRACT FROM AUTHOR]

The paper presents the results of investigations of brazed joints of 08Yu galvanized steel, produced by welding, arc and plasma brazing. It is confirmed that in the first case, spattering of the liquid pool metal, zinc evaporation and porosity formation take place. The influence of energy input on brazed seam parameters was studied in plasma brazing with application of BrKMts 3-1 brazing filler metal. It was found that increase of energy input leads to reduction of face reinforcement height, but promotes increase of the reverse reinforcement height, that requires a greater amount of brazing filler metal. It was empirically determined that energy input value in the range of 520 - 590 J/cm ensures producing butt joints of galvanized 08Yu steel with optimum size of reverse reinforcement. X-ray microprobe analysis showed that high-quality dense welds form in this mode that have the structure of copper-based solid solution with dispersed inclusions of iron-based phase, enriched in silicon. 11 Ref., 1 Tabl., 9 Fig. [ABSTRACT FROM AUTHOR]

The paper presents the concept of bulk and surface heat treatment of the welded butt joint of a railway rail by two or more inductors with the purpose of achieving favourable phase transformations of metal and normalizing its structure in the weld zone. Performed computations and experiments resulted in development of detachable inductors without magnetic circuits, which allow performance of bulk and surface induction heat treatment. Conducted experiments on heating a welded butt joint of a rail by the developed detachable inductor without the magnetic circuit demonstrated heating uniformity characteristics acceptable for bulk heat treatment of rails, limit temperatures and rates of heating of the main rail working areas both on the surface and in-depth in a narrow heating zone. [ABSTRACT FROM AUTHOR]

The paper gives the analysis of the state of the art of 3D technologies of polymeric materials, which is based on publications presented both in open sources as well as in a wide range of scientifi c and technical journals, including the own experience of the authors in 3D printing using thermoplastic and thermosetting polymers. The history of additive technologies, state of the art and trends of the development of the market of three-dimensional printing are considered. The classifi cation of the most widespread in the world technologies of additive manufacturing of products from polymeric materials depending on the methods of processing plastics is off ered, their short description is given, their features, advantages and disadvantages are presented. [ABSTRACT FROM AUTHOR]