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
Investigated are structure and phase composition of weld metals as well as HAZ of welded joints (of carbon, low-alloy structural and cold-resistant steel, nickel and aluminum alloy and others) in fusion welding and reconstruction repair surfacing using different welding consumables (electrodes, fluxes and wires). Analytical estimations of role of forming structural parameters in change of complex of mechanical properties, as well as nature of distribution and localizing of deformations, level of local internal stresses, intensity and extension of stress concentrators, being potential sources of crack formation generated in welding, were carried out based on experimental data, received on different structural levels (from grain to dislocation ones). The results of carried investigations were used for correction of technological processes of welding that allowed providing high complex of mechanical properties and crack resistance of welded joints. 12 Ref., 7 Figures. K e y w o r d s : arc welding, structural steels, welded joints, structural factors, mechanical properties, crack resistance
Presented are the investigations of effect of composition of surfacing consumables on structure and phase composition of deposited metal of surfacing zones (surface, fusion line, HAZ) in restoration of railway wheels from grade 2 steel. Information received at different structural layers (from grain to dislocation) was used for analytical estimations of effect of parameters of forming structures on mechanical properties (σ0.2, K1c) of railway wheels, reconstructed by surfacing, before and after operation. Role of structural factors in change of level of local internal stresses τl.in, i.e. sources of crack formation in subsurface layers of deposited metal, was investigated. It is determined that surfacing consumables of bainite and bainitemartensite classes provide for high indices of mechanical properties and crack resistance of railway wheels after restoration repair and operation. 9 Ref., 1 Today problem of increase of service reliability and life of machines, mechanisms, parts etc. becomes more and more relevant. This problem is particularly critical for separate heavy loaded basic parts and mechanisms of running gear of cars and engines, main element of which is a wheel having direct contact with rail. Surface of wheel flange is subjected to the most significant wear in process of operation. Regardless different technological developments of restoration repair, problem of strength, reduction of wear level and crack resistance of railway wheels [1-3] is still relevant.In relation to restoration surfacing of surface of wheel flange, the authors carried out preliminary examinations of structural-phase changes in metal close to the roll surface of railway wheels [4]. Role of each of structural factors (phase constituents, grain, subgrain and dislocation structures, phase precipitates etc.) in change of strength and crack resistance of metal of railway wheels was investigated based on obtained results. The results of experimental investigations, received at different structural levels, i.e. from macro (grain) to micro (dislocation), made a basis for performance of analytical estimation of specific (differential) input of separate structural-phase factors and parameters in change of general (integral) value of mechanical characteristics, namely strength σ 0.2
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