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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]

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 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 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]

The paper presents the results of determination of the quantity and dimensions of grains of the structural components of steam pipeline welded joint metal. The above determination was performed using an improved method of analysis of the structuralphase state of welded joints. It was found that during long-term operation of welded joints the grains of α-phase increase in size. Structural analysis was performed for base metal of welded joints, HAZ regions, as well as weld metal. It was established that at long-term operation of steam pipeline welded joints grain dimensions are increased in their HAZ regions. It was found that the boundaries between individual grains are partially eliminated. Based on analysis of statistical data, grain dimensions, as well as their shape and distribution were determined at application of the secant method. 9 Ref., 1 Tabl., 7 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]

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 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 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]

Welding processes involve often very high temperature gradients, which can induce elevated residual stresses (RS). It is essential, therefore, to know these RS, especially by determining them experimentally e.g. before and after thermal treatments. Neutron beam techniques contribute in general to the solution of important questions and problems related to the methodological restrictions of the analysis systems normally used: complementary to these investigation methods, they provide concrete and fundamental help to optimize the finished industrial product and increase its performance. Neutron diffraction, in particular, is a powerful tool to assess in a non destructive and non invasive way the RS status in materials and components of technological interest. In this paper, the basic theoretical aspects and some examples are reported, regarding the possible determination of RS by using neutron diffraction in different kinds of welded structures. [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 volume of polymer composite structures in the aircraft industry is steadily increasing. Polymer composites based on thermosetting mats are traditional in this fi eld, but it is important to use new thermoplastic composites (TPKs), which have several advantages over thermosetting ones. The use of thermoplastic composite materials makes it possible to actively use welding processes in the production of structures, which signifi cantly increases the productivity of work and reduces their cost. The most used in the aircraft industry are 3 types of heat-resistant polymers of the class of polyarylene - polyether ether ketones (PEEK and PEKK), polyetherimide (PEI) and polyphenylenesulfi de (PPS). Aeronautical structures are characterized by a large variety and complexity of forms, that’s why almost all known methods of plastic welding are involved for joining. The resistance welding of polymeric materials using embedded elements made of metal mesh or carbon fabric is actively used. Inductive welding technology is suitable for joining structures made of conductive carbon composites. Ultrasonic welding, laser welding, and indirect-heated hot-welding are also used in aircraft engineering. Nowadays, welding processes are usually digitally controlled with permanent data storage, but currently the agenda is to move to linear process control using temperature monitoring. This paper, based on the materials of European publications, presents examples of the application of different welding methods in the manufacture of structures made of modern polymer thermoplastic composites in the aviation industry. [ABSTRACT FROM AUTHOR]

The paper presents the results of studying the weldability of sheet aluminium alloy of V134T grade of Al-Mg-Si-Cu-Fe system under the conditions of nonconsumable electrode manual argon-arc welding. This alloy is characterized by high susceptibility to hot cracking in welding. The hot brittleness index is equal to A = 65.8 – 85.5 %. The impact of filler material chemical composition on hot cracking resistance of weld metal was studied. It is found that in welding by batch-produced wires of SvAMg63, Sv1201, Sv1217 grades the crack resistance value is A = 30.3 – 53.9 %, and at application of wire of ZvAK5 grade this characteristic of welds is equal to A = 6.6 – 19.8 %. Nonconsumable electrode manual argon-arc welding of V1324T alloy allows producing tight sound joints of this material with strength coefficient of 0.80 – 0.87 which also depends on filler wire chemical composition. The value of ultimate strength of the alloy welded joints, made using different grades of filler wire is equal to σt = 193.2 – 209.0 MPa, and the yield limit σ0.2 = 138.4 – 151.6 MPa; relative elongation δ = 3.1 – 5.4 %, bend angle α – 40 – 65 deg. [ABSTRACT FROM AUTHOR]

Development and introduction of new energy-saving technologies meets the modern demands of Ukraine. In the paper background, current state and directions of development of studying the influence of electromagnetic fields on mechanical properties and the stressed state of metal materials and welded joints are considered. The possibility of their application for control of the stressed state, the evolution of structure, properties, elongation of the life of welded structures is shown. [ABSTRACT FROM AUTHOR]

The technology of laser welding by a transmission method allows welding overlapping polymeric films and sheets of various thickness. Welding of polyvinyl chloride films using a diode-pumped solid-state laser (DPSS) of 10 W power, which generates green radiation with wavelength of 532 nm, was performed in the developed experimental equipment. Application of this method made it possible to weld transparent multilayer medical films Wipak. Experiments have shown that with the help of such a laser it is possible to form a high-quality joint of Wipak medical film with paper [ABSTRACT FROM AUTHOR]

The structural pseudo-β-titanium alloys found a wide application in aircraft and rocket building. However, while producing welded joints of pseudo-β-alloys applying method of fusion welding, the difficulties arise connected with change in the structure and formation of metastable phases in welded joint. In this paper, using the developed mathematical model of the TIG-welding process, the influence of thermal welding cycle on the weld shape, cooling rate and structure of welded joint metal of the pseudo-β-titanium alloy VT19 was investigated. A number of phases in the weld metal, heat-affected zone and base metal was established, the phase composition and its effect on the mechanical properties of welded joints were predicted. [ABSTRACT FROM AUTHOR]