CURRENT PROBLEMS IN WELDING AND LIFE OF STRUCTURES
Current trends of research and development in the field of welding and strength of structures.
|The paper presents some developments made lately by the E.O. Paton Electric Welding Institute, such as hybrid welding methods, activation of processes occurring in the weld pool under the effect of minor additions of chemicals, electric arc welding using an embedded electrode, machines for flash butt and electron beam welding, new filler alloys and fluxes for brazing, and new structural materials. It is noted that structures, constructions and equipment that approach their critical age have substantially increased in number. In this connection, the pressing problem is reliable estimation of residual life of structures using non-destructive testing and technical diagnostics methods. Technology and instruments for welding of live tissues are considered.|
|Lobanov L.M., Kirian V.I. and Shumitsky O.I.|
Fifty years of the E.O. Paton bridge.
|Problems of welded bridge construction, solved under the supervision of E.O. Paton, are considered at the initial stage of its development and finally 50 years ago by the construction of unique all-welded bridge across the Dnieper river in Kyiv. The ways of assurance of rated service life of all-welded bridges are shown on the base of major principles of design, used in E.O. Paton bridge designing, and established main causes of earlier initiation of fatigue cracks in elements of standardized spans. Design solutions of spans and welded connections, preventing the occurrence of secondary stresses and vibrations in them, were recognized determinant. Selection of steel, welding technology and treatment of welded joints plays an important role in the prevention of fractures.|
Space technologies on the threshold of the centuries: results and prospects.
|The paper presents the main scientific-technical achievements of S.P. Korolyev RSC "Energia" over the last decade as aillustration of the successes of the rocket-space industry in the international market of advanced science-intensive technologies for space mastering in the XXIst century. These achievements would be unthinkable without solving the diverse problems of welding to together with the leading organization in this field - the E.O. Paton Electric Welding Institute.|
|Olson D.L., Metzbower E., Liu S. and Park Y.D.|
Developments in property predictions for weld metal.
|With the introduction of higher strength low-carbon steels, which have properties that are based on strengthening mechanisms other than the austenitic decomposition, new predictive expressions are required. As new welding processes increase productivity, it also becomes essential to present the cooling rate, Dt8/5, into predictive expressions. Furthermore, the oxygen content must be included to make these expressions useful in predicting weld metal properties. In addition to the elemental consideration, influences from solidification and second phase particles, such as inclusions, affecting the weld metal solid-state transformation reactions are discussed. Empirical expressions have been developed to predict hardness, yield and ultimate tensile strength, as well as ductility and toughness for low-carbon and low-alloy higher strength steel weld metal. The difficulty introduced by multiple pass welding on weld property predictions is recognized. Various approaches, based on either deterministic analyses with numerical calculations or experimental correlations have been attempted, and these approaches are also discussed. With the availability of new analytical approaches, such a neural net regression analysis, more rapid and compatible selection of the welding consumable composition for a specific alloy and welding thermal experience can be achieved.|
|Lyakishev N.P. and Nikolaev A.V.|
Metallurgy of steel: specifics of production in the XX century, problems and prediction of future development.
|Major stages of development of metallurgical production of steel in the XX century are considered and geopolitical factors, defining its progress, are formulated. A determinant role of energy consumption in aggloblast furnace production is shown in the energy balance of the integrated works. Alternative processes of steel production are described. The significant decrease in energy consumption can be attained in combination of several technologies. Steel melting and generation of commercial heat and electric energy using the technology of plasma-electrometallurgical complex are challenging. The ways of metallurgy progress in the XXI century are outlined.|
|von Hofe D. and Schambach B.|
The new ISO 3834 - quality requirements for fusion and resistance welding of metallic materials.
|History of development of the quality management system standards of the ISO 9000 series and degree of their conformity with later standards ISO 3834:1994 and EN 729:1994 are considered. Priorities related to revision of standard ISO 3834 in terms of acceptance of improved standard ISO TC44 SC "Unification of Requirements in the Field of Metal Welding" are noted.|
|Gorynin I.V., Iliin A.V., Baranov A.V. and Leonov V.P.|
Problems of guaranteeing the strength and design life of sleet-proof off-shore platforms in the Arctic shelf.
|A set of requirements to the quality of welded joints, guaranteeing prevention of cyclic and brittle fractures should be satisfied, in order to provide service reliability of hull structures in off-shore platforms in the Russian shelf. The paper analyzes the problems, arising in application of foreign approaches to substantiation of these requirements, and suggests ways to solve these problems, based on the methods of physical modelling of fracture processes. Investigation results are implemented in standards and procedures of RF Register and are used in certification of materials and welding technologies for shelf structures.|
|Kiji N., Kobayashi K., Ishii J. and Yamaoka H.|
Development of high efficiency arc welding methods.
|The high efficiency twin arc TIG welding method and the high AC MAG welding method have been developed and applied into various structures. Those welding methods can weld in the higher current conditions and achieve the higher deposition rate than the other conventional welding methods. About A-TIG welding, the efficient welding procedure for thick plate welding has been developed.|
New information systems for non-destructive testing and diagnostics of welded structures.
|New devices providing information on internal structure of a part and its defects are described. Acoustic-emission systems allow identification of such dangerous sources as plastic deformation, initiation and propagation of cracks and corrosion damages. Ultrasonic tomograph registers information on configuration, size and orientation of defects. Spectral-acoustic monitoring systems are suggested for measuring volumetric two-axial stresses. New solution to a practical problem of development of technology and equipment for NDT of austenitic welds in joints from 5 to 100 mm thick is described.|
|Pilarczyk J. and Banasik M.|
Technological applications of electron and laser beam.
|In the paper it has been discussed the scientific-research and technological works in the field of electron beam welding and laser cutting and welding conducted at the Welding Institute in Gliwice. The characteristics of the equipment applied in the works have been presented. It has been given a number of application examples of technology developed at the Institute and implemented to machine-building and automotive industry. The collaboration of the Institute with another institutions and industrial companies on the area of implementation of these technologies has been discussed.|
|Gao H., Wu L. and Dong H.|
Preliminary study on penetration mechanism of double-sided GTAW process.
|How increasing the productivity and lowering the costs are always a serious problem in the welding production. Large amounts of research were done, and many new welding processes were presented, the double-sided arc welding (DSAW) process is one of them. Experiments show that this new process has many advantages in contrast with conventional processes, especially the penetration ability. Up till now, many characteristics of the process are not well known, so deep research into its mechanism is needed, and it is significant for its application. In this paper, through theoretical analysis, experimentation and numerical simulation, the penetration mechanism of double-sided GTAW process is probed. Results show that, firstly, the welding current flows straight through the weld zone, leads to a concentrated current distribution, forms a stronger electromagnetic force field, and causes a stronger fluid flow in the weld pool, which is in favor of the penetration. Secondly, during double-sided GTAW process, when the weld is partially penetrated, there is a heat-concentration zone between the bottoms of the two weld pools, where the temperature can increase quickly even though only a small amount of heat is applied. Thirdly, the buoyancy force caused an inward flow in the bottom weld pool, which can drive the hot liquid on the surface to the bottom of the pool, and then form deep weld pool.|
|Beloev M., Hartung F., Lolov N. and Alexandrov B.|
Influence of microstructure on corrosion resistance of welded joints of duplex stainless steel.
|Properties and applications of a comparatively new group of high-alloyed stainless steels that has been introduced in practice since 1970s are reviewed in this report. These are so called duplex stainless steels, the structure of which consists of approximately equal quantities of austenite and ferrite. These steels have many advantages compared to the traditional austenitic stainless steels. Their advantages result in increasingly wider use of duplex stainless steels in many industry branches as petrochemical industry, especially in off-shore installations, in chemical industry in installations for pulp and paper, in installation for fertilizers etc., in energetic industry for fuel gas desulphurisation, in shipbuilding for chemical tankers, in mining industry in installations for extracting of different ores, in pharmaceutics and so on. The present report represents a first stage of research project for implementation of duplex stainless steels in the Bulgarian industry, performed jointly by the Technical University of Sofia and KZU Holding Ltd. Under the current stage of the project the optimal implementation of pulsed gas metal arc process for welding of duplex stainless steels is being investigated.|
|Frolov K.V., Makhutov N.A. and Gadenin M.M.|
Determination of strength, service life and survivability of structures.
|Fundamentals of methods and systems of determination of characteristics of strength, service life, survivability and safety of complex technical systems at combined action of service damaging factors are described. In construction of systems of analysis and monitoring of scheduled and emergency situations, it is offered to take into consideration design, technological and service parameters of shapes, sizes, materials, methods of manufacture, control and conditions of operation of load-carrying elements of highly-hazardous objects. One of them is the wide application of welding in the creation of these objects.|
Review of fatigue design rules for welded structures.
|Current fatigue design rules are reviewed in the light of recent research and the changing needs of industry. Available evidence indicates that many revisions are required and the scope can be extended. Topics addressed included classification of butt and cruciform joints, the inclusion of non-arc welds, size effect corrections, the hot-spot stress approach, the treatment of complex combined loading and cumulative damage calculation methods.|
|Panasyuk V.V. and Dmytrakh I.M.|
Evaluation of corrosion fatigue strength of welded joints as heterogeneous systems.
|The paper describes experimental-analytical methods of evaluation of local corrosion and local fracture of welded joints of the type of "anticorrosion cladding-casing steel". The constructed diagrams of electrochemical resistance and corrosion crack resistance of multilayer welded joints may be the basis for evaluation of the residual life of the considered joints.|
Improvement of methods for estimation of residual life of welded joints in durable structures.
|Characteristic peculiarities of welded joints in durable critical structures requiring certain approaches to estimation of specified service life, residual safe life in particular, are considered. The possibility of using modern fracture mechanics approaches combined with rapidly developing risk analysis methods is examined.|
Effective notch stress method in comparison with other methods in fatigue design of welded structures.
|Structures loaded by fluctuating forces are susceptible to fatigue damage. Besides the classical component testing, several calculative assessment methods have been developed. Most commonly used is the nominal stress method, which is based on the average stress in the section to be verified. With the oncome of the finite element method (FEM), more universal methods could be developed. The new method of effective notch analysis refers directly to the notch, at which a fatigue crack initiation is expected. On the basis of Neuber's theory and of more than 80 fatigue test series containing more than 1000 test specimens, it can be shown that the weld notch can be replaced by a fictitious, but consistent radius. For steel this radius is 1 mm. This method has been introduced to the IIW fatigue design recommendations.|
Failure of welded aluminium tubes.
|A failure investigation concerning 6061-T6 aluminium tubes as produced by an extrusion process, required an extensive and detailed study. This involved ten aspects, namely the manufacturing process; 3D finite element stress analysis; microstructural fracture mechanics; metallurgical considerations; international codes and specifications; residual stresses; Raman spectra analyses; environmental factors an extremely long-life fatigue failure assessment; and recommendations as to how to avoid future failures. Obviously the investigation required a multi- and inter-disciplinary approach. At the start of the study the opinions of several experts were sought. At the termination of the investigation successful recommendations were made to the manufacturers that avoided future failures. The brief case history presented in this paper is a useful exercise for students of microstructural fracture mechanics and fatigue failure analyses.|
|Zubchenko A.S., Vasilchenko G.S. and Ovchinnikov A.V.|
Prediction of fracture of welded joints in ductile steels containing defects.
|Method for calculation of limiting loads for a structure comprising welded joints with defects is suggested. The method allows modelling of the process of quasi-static propagation of cracks in ductile steels. Examples of the calculation are presented.|
|Takano G. and Kamo K.|
Development of fully automatic welding technique for vessels and pipes.
|The problem of quality assurance of welded joints in the conditions of TIG automatic welding of thin-sheet vessels and pipes is considered. It is shown that the alternative of high skill and experience of welder is the application of welding machines using the methods of read and adaptive control being developed. These machines can operate separately until now only during a certain period of operation. The next steps are necessary for the creation of logics of adaptive control of welding conditions with allowance for the difficulties in fulfillment of jobs.|
|Larionov V.P., Sleptsov O.I., Lepov V.V. and Yakovleva S.P.|
Study of low-temperature strength of materials and their welded joints to handle problems of the russian north.
|Problems associated with operation and repair of industrial facilities and metal structures under the Russian North conditions are considered. Areas of basic and applied research conducted by Yakut scientists with a purpose to develop new materials, welding processes and study behaviour of welded structures during operation are described. Promising lines for further research are presented.|
|Dilthey U., Stein L., Woeste K. and Reich F.|
Latest developments and trends in high-efficient welding technologies.
|Within the last couple of years, there have been several new developments in the field of high-efficient welding technology. This paper presents these developments, describing their principle, outlining their possibilities and giving examples for their application. Fields addressed are new arc welding processes, latest developments in electron beam welding, as well as trends in laser beam welding concerning processes and equipment.|
|Dehelean D. and Markocsan N.|
Rapid fabrication of refractory components by thermal spraying.
|Using new technologies like near net-shape spray forming is possible to obtain quickly nozzle type refractory components. Material utilisation and very high and laborious machining can be avoided. In order to achieve nozzle type components plasma spray technique has been used to spraying molybdenum powder onto a preshaped substrate. The influence of plasma spraying parameters on the mechanical and physical properties of free-standing components has been studied. The residual stress was also evaluated in order to know their behaviour and working ability under difficult conditions.|
|Gorbach V.D., Sokolov O.G. and Mikhajlov V.S.|
Problems of welding and fatigue life of welded structures in shipbuilding.
|Factors are considered, which determine the cyclic strength and fatigue life of shipbuilding welded structures. Design evaluations of welding deformations are given for the case of the hull of a tanker and catamaran ship. Methods to lower the local and total deformations, stabilization of the shape and accuracy of welded structures through their low-frequency vibration treatment are outlined. Examples are given of using fundamentally new types of welded joints, based on high-energy density sources and adaptive welding processes.|
New developments of technologies and equipment for flash-butt welding of pipelines.
|The paper describes new developments of technology and equipment for flash-butt welding of pipes, allowing enhancement of the technological features of application of this welding process in construction of various pipelines.|
|Kogure H. and Fujita Yu.|
Review of qualification and certification system for welding personnel in japan.
|This paper summarizes the certification systems for welders and welding engineers established and implemented by the Japan Welding Engineering Society (JWES). The first issue for SMAW welders was appeared for carbon steel by JWES in 1944. After that, the various kind of issues for the different materials appeared with a variety of process has being introduced due to the request from the wide range of industries. The certification systems for welding engineers has been established in 1971. The scheme for the welders and the welding engineers are revised slightly in 1998 along with ISO Guide 61/EN 45013 and also along with ISO 14731 (JIS Z 3410). The schemes are acrreditated by the Japan Accreditation Body for conformity assessment in 1999. Regarding the qualification system for welding engineer, welding technologist, welding specialist and welding practitioner, the Authorized National Body of Japan which are operated under JWES are established and approved by IIW in 2000, and the transition arrangements from the above certification holder has being implemented from 2001. There are unique Approved Training Body in Nagoya for the qualification system for welding engineer, welding technologist and welding specialist.|
|Herold H., Zinke M. and Karpenko M.|
Application of modern hybrid technology for welding of high corrosion resistant Ni-based alloys in environmental technology.
|The paper shows the advantages of application of a hybrid welding process (YAG laser + hot wire TIG) compared to TIG processes and laser welding, to produce reliable and sound joints of critical structures in high-nickel alloys. A great depth of penetration and high efficiency of the process can be achieved at a small input.|
Arc joining of steel with aluminium
|Latest investigations showed that joining of aluminium with steel would improve the characteristics of components used in industrial applications. Especially in the automotive industry joining of these two materials would minimize energy consumption. Until now mechanical joining of these two materials (clinching, screwing, etc.) was mostly done to attach or band them. Thermal joining is strongly restricted due to the formation of intermetallic phases. These phases are very brittle and therefore deteriorate the mechanical properties of such joints. Another attempt to join steel with aluminium is the use of laser systems combined with pressing devices. This paper describes a modified GMAW system to join Zn-coated steel with aluminium alloys of type 6000 (AlMgSi) and, with some restrictions, even with aluminium alloys of type 5000 (AIMg).|
|Paton B.E. and Medovar L.B.|
New electroslag technologies and materials.
|Tendencies in the development of electroslag technologies and production of high-alloy steels and alloys using EST methods have beeb analyzed. Steady tendencies in the growth of production of electroslag metal by 5-6 % per year over recent 10 years and for the nearest future are shown. Feasibility of EST application in the production of superalloys, titanium, intermetallics and bimetals is discussed.|
|Sheleg V.L., Ragunovich S.P. and Torpachyov S.P.|
Towards the use of acoustic field of the process of welding as a factor of control and diagnostics of welded joint quality.
|Acoustic fields of consumable electrode shielded-gas welding processes with a fine- and coarse-drop metal transfer were investigated experimentally. The prospects of application of acoustic field of the welding process for control and monitoring of its quality are discussed.|
|Okamoto K., Hirano S., Inagaki M., Park S.H.C., Sato Yu.S. and Kokawa H.|
Feasibility study of metallurgical and mechanical properties of friction stir welded stainless steels.
|Friction stir welding has been remarkably applied as innovative production methods for several industrial sectors because of the advantages to the technique. However, the commercial benefits are still limited to light metals, such as aluminum, magnesium and copper alloys. In this paper, the feasibility studies of mechanical and metallurgical properties of friction stir welded stainless steel thin plate and thick plate have been studied. Single-pass bead on plate and butt weldments in the commercial austenitic stainless steel were successfully achieved. The joints were evaluated by microscopy and hardness tests of the transverse cross section and transverse tensile tests. Temperature hysteresis of the workpiece during the process was also measured.|
|Ushio M. and Sugitani Yu.|
Recent development of high efficiency arc welding systems in Japan.
|The paper describes recent trends to carry forward the automation in welding process in Japanese industries. The present situation on the introduction of computer integrated manufacturing is surveyed and its concept and relation among the constituent subsystems are shown. Also recent developments of arc welding processes and related tools are reviewed. They are as follows: schematic image of the structure of computer integrated manufacturing system (CIM); short descriptions for the trend of introducing CIM system (an example of multi-robot welding system in shipyard, virtual factory, network monitoring of welding quality, clarification of welder's skill); development of high efficiency welding processes.|
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