Submerged arc welding is the most applicable and productive procedure when thick sections have to be welded. Nevertheless, the manufacturers of pressure vessels, pipelines, ships and offshore structures keep on looking for new and modern design solutions of equipments and technologies which should lead to increase of welding process productivity. For instance, the longitudinal welds of pipelines are, mostly, performed by submerged arc welding procedure with multiple arcs and/or multi-wires, such as twin, tandem or twin-tandem, in order to increase the process productivity. However, achievement of optimal mechanical properties of the welded joint should remain the most important quality criteria. It is well known that dependence of the mechanical and metallurgical changes on heat transfer plays a major role in obtaining of safe welded structures and preserving of their structural integrity. That is why the investigation of heat transfer induced by the welding process is required. Furthermore, setting of distance between thermal sources and its influence on the overlapping phenomenon of temperature fields should be explored when submerged double-arc welding procedure is applied. Three dimensional finite element model of butt welded joint - used for simulation of heat transfer in pipeline steel joint performed by submerged double-arc welding process - is developed and described in this paper. Numerical results and a comparative analysis related to the temperature distribution, thermal history, and temperature variation in cross section of the welded joint at different time steps are discussed. Finally, important conclusions regarding the influence of distance between thermal sources on thermal effects and temperature fields overlapping are drawn.

The investigation focussed on the modelling by finite elements of heat transfer and Von Mises stress field and simulation of the tensile test when applying friction stir welding (FSW) and classical Tungsten Inert Gas (TIG) welding at the aluminium alloy AA 6082-T6 butt joints performing. Both the numerical and experimental results revealed big differences between the behaviour of the base materials welded by FSW and TIG. It is important to study the heat transfer mode during the welding process, because it has a huge influence on the mechanical properties changes of the welded joint. The capability of a welded joint to resist breaking under tensile stress is one of the most important and widely fundamental mechanical tests used in the analysis of the materials behaviour at welding. Tensile properties indicate how the material will react to forces being applied in tension. Whilst the tensile strength of the TIG welded joints represents 66% from that of the parent metal, in the case of FSW butt joints the tensile strength is reaching about 75% in comparison with the tensile strength of the base metal. Because the welding principle is different, also the breaking location is different. That is why the fracture was located at the external limit of the tool shoulder for the joints performed by FSW and in the heat affected zone in the superheating area for the TIG welded joints. Finally, the output data achieved by modelling and experimental results are analysed and discussed. Key-Words: FSW, TIG, aluminium alloy, heat transfer, tensile test, simulation.

The agitation by electromagnetic way of the melted slag, due to the field of speeds, influences the density of current and in the end the distribution of the temperature in the slag welding pool. The phenomena from the slag welding pool, during the welding process, are determined by the presence and the interaction of the following fields: the electrical field, the magnetic field, the thermal field, the hydrodynamic field. The paper described how these fields interact in the electro-slag welding pool. The optimal values of frequency and induction of the magnetic field to give a high quality welded joints are determined.

This paper presents a comparative study of theoretical and experimental temperature fields on butt-welding. A theoretical method using finite element analysis has been used for the temperature prediction in the X52 welded joints. A non-linear transient thermal analysis was used to obtain the global temperature history generated during the welding process. The temperature fields were plotted function of the distance from the weld centre, at different time steps. Several measurements and visualization of the temperatures distribution have been made using infrared thermography. Temperature values for both used methods, in the cross section of the welded joints, on the lower and upper side of welded joint in the selected points tire presented The errors were calculated for all cases and error curves were plotted.

In this paper, we presented the temperatures distribution, Von Mises stresses distribution and the Cauchy stresses distribution for the FSW welding process of the AA6061 T4 aluminium alloy. We took into account the case in which the tool is mobile. To stimulate displacement or movement of the thermal source it used 200 functions, corresponds, to the number of the welding tools positions that move along the longitudinal axis of the joint.

The paper presents some experimental investigations on the filler metals metalographical at the electro-slag welding in the electromagnetic field. References (1) Nădăşan, Şt., ''Încercări şi analize de metale'' (''Metal Trieds and Analysis''), Bucharest, 1965. (2) Morariu, Şt., ''Transformări în îmbinările sudate ale oţelurilor'' (''Iron Transformations in the Join Welds''), Timişoara, 1984. (3) Micloşi, V., Scorobeţiu, L., Jora, M., Miloş, L., ''Bazele proceselor de sudare'', (''Base of Welding Proceses'') , Bucharest, 1982. (4) Safta, V., ''Controlul îmbinărilor şi produselor sudate'', (''The Control of Welding Joins and Products) , Timisoara, 1986.

The paper introduces the thermal field and residual stresses, numerically modelled by the finite element method, and compare them to the experimentally determined data obtained by thermography and tensometry measurements. The finite element analysis was carried out in two steps. First, the thermal field was modelled, followed by the stress analysis, as the obtained temperatures distribution constituted the load for the structural analysis, the analysis of which gave the stress state of the welded joint. An error diagram was drawn, thus comparing the experimentally determined values to those resulted from modelling.

This paper presents the electro-thermal-magnetic field phenomena which take place in the molten pool when an external magnetic field is applied. Some types of agitation, the basic concept about electromagnetic agitation, the numerical simulation of the electro slag welding with electromagnetic agitation and the graphical result of the simulation are presented. The agitation by electromagnetic way of the melted slag, due to the field of speeds, influences - through the equation of movement - the density of current and in the end the distribution of the temperature in the slag welding pool. The phenomena from the slag welding pool, during the welding process, are determined by the presence and the interaction of the following fields: the electrical field, the magnetic field, the thermal field, the hydrodynamic field.

The electromagnetic agitation of the melted slag affects, according to the equation of movement, the current density and finnally the temperature distribution in the slag welding pool. The slag welding pool phenomena, during the welding process, are induced by the presence and the interaction of the following fields: electrical field, magnetic field, thermal field and hydrodynamic field. The metal cast structure of the weld obtained in the slag welding pool has an anisotropy of the mechanical properties that is prooved by a minimum resistance in the seam area. The properties of this area depend very much by the nature of the structural homogeneity, produced after the crystallisation of the welding pool and by the size of the crystalline grains.

This paper presents a method for analyzing mechanical properties of welded joints of X60 steel melting, only the results obtained by simulation test tubes. For this purpose simulation test-pieces were captured in the simulator and subjected to a thermal cycle similar to that of fusion welded HAZ site. Then specimens were taken for determination of fracture energy, and hardness test. The results were compared with those of the actual merge.

This paper contains the establishment of the reshuffle technology by the process of welding the parts cast of magnesium RZ5. These alloys are used frequently in the automotive industry. In the first part of the paper there are presented the performances, the influences of the main alloying elements and the welding behaviour of the magnesium alloys. Furthermore it is presented the experimental program and the un-destructive and destructive control of the submissions. The paper ends up by presenting the final conclusions.

The paper introduces an original 3D FEM model of Friction Stir Welding phases. The outputs are the thermal, and the stresses fields, respectively. The recently published literature validates the process model.

The paper presents an influence of temperature changes investigation during arc welding process. Heat input in weld joint during arc welding is necessary for base and filler material melting on joint location. Depending on heat input (primar and secundar heat input), applied welding process, type and thickness of material, grove preparation and other welding process influencing variables, the temperature field distribution during heating and cooling of weld joint is formed. Temperature changes of individual points in weld joint during heating and cooling have influence on mechanical and other properties of welded joint. The paper presents application of thermovision method for temperature field determination at welding process.