Structure and service properties of welded joints of high-strength steels, aluminium and titanium alloys

Abstract

In automation of consumable electrode arc welding it is necessary to have a clear knowledge about the structure of system for a self-regulation of the electrode melting rate. In the given work a general structure of this system is constructed on the basis of analytical description of dynamic processes, proceeding in the welding circuit. A simple structure analysis allows easy obtaining the necessary characteristics of the self-regulation system, including accuracy in a steady mode and time of optimizing the effect of disturbances. Criteria are suggested, that allow selecting those parameters of welding processes from the admissible values, which provide the desirable quick-response of the self-regulation system. Results of comparison of quick-response estimates, obtained by using these criteria, with results of computer modeling, are given. 21 Ref., 5 Figures. K e y w o r d s : robotic arc welding, consumable electrode, structure of self-regulation system, evaluation of accuracy and quick-response of system

Comparative analysis of the results of computer simulation of heat transfer and hydrodynamic processes in the metal being welded by means of different software tools

“…The kinetics of the microstructure phase transformation during welding the DSS on the basis of literature data [17,21] was modelled. Weldments of DSS with a Cr eq /Ni eq ratio above 1.95 (for steel S32205 Cr eq / Ni eq = 3.5) can be treated as a single-phase ferrite [22] when solidifying.…”

“…Weldments of DSS with a Cr eq /Ni eq ratio above 1.95 (for steel S32205 Cr eq / Ni eq = 3.5) can be treated as a single-phase ferrite [22] when solidifying. The dissolution and precipitation kinetics of austenite in duplex stainless steels is followed by the Austin-Rickett type eq uation [17,21] :…”

“…Since heating during the welding thermal cycle occurs without aging and cooling continuously with a variable cooling rate, the Austin-Rickett eq ua tion was accepted as modified equation taking into account the features of the welding thermal cycle. For this, the heating and cooling curve was divided into steps and the fraction of austenite was determined by the expression below [17] :…”

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“…stress concentrators, the values of these characteristics of the metal state, and the dynamics of their change during underwater welding and the use of EEI. The set problem is of key importance, because the processes of delayed fracture, formation of the source of crack initiation and propagation begin directly from the initiation of inner stress concentrators [16][17][18][19].…”

Mathematical models of the dependence of mechanical properties on chemical composition of steels for ESW

“…It is known that one of the important imperfections of a crystal lattice is its defects -dislocations, around which elastic zones of curvature of a crystal lattice are formed [11][12][13][14]. The distribution of dislocations, their density and nature of dislocation structure have an impact on mechanical properties of the metal [5,12,17]. When a magnetic field is applied, the dislocation system becomes unstable, which leads to a redistribution of crystal lattice defects and can lead to a mutual annihilation of dislocations and a decrease in inner stresses.…”