In the recent years laser beam welding has been more and more broadly used in the industry for the production of details of significant appointment. One of the perspective directions of laser technologies for the production of significant products of big thickness is the welding by the concentrated laser beam in vacuum that allows producing faultless welded seams with the high relation of seam depth to its width. The conducted researches confirm results of theoretical modeling of processes at laser beam welding.

The aim of the work is to obtain an empirical model for calculating the value of the spark gap in the electrical discharge machining of 38X2H2MA steel. Due to the fact that the discharge machining is a non-contact method, when the tool electrode is inserted into the workpiece between the end faces and the side surfaces of the tool electrode and the cavity formed, respectively, the end and side clearances are formed. The main factors affecting the size of the gaps are processing modes and material of the electrodes. The actual task is to predict the size of the spark gap when processing chromium-containing steels, depending on the modes of copy-piercing erosion processing. To obtain the empirical model, the method of factor cladding of the experiment with subsequent regression analysis was used in the work. The criterion for optimality of a plan in orthogonal central compositional planning is the orthogonality of the columns of the planning matrix. For the experiment, the following factors are selected: I -current strength (A), T on -pulse time (µs), T au -pulse fill factor (%). According to the carried out experiment and the subsequent regression analysis, a model is obtained for calculating the size of the lateral gap. On the basis of the obtained data, it becomes possible to predict the correction value when processing steel 38X2H2MA. The analysis of the model showed that the size of the gap is affected not only by the factors themselves, but also by their totality. A geometric representation of the law of variation of the lateral clearance value is presented depending on the erosion control modes. The received data allow to make adjustments of the electrode-tool dimensions in order to provide the given parameters of processing accuracy.

Many welded structures are produced from carbon steels for service in conditions of subzero temperatures. One of the required properties of metal for welded joints is high cold strength. The latter is determined by the combination of the metallurgical factors of the initial steel (composition, heat treatment, deoxidation, desulphurisation and dephosphorisation) and welding factors (the conditions of solidification of weld metal, the probability of contamination with nonmetallic inclusions from welding materials, the nature of the final structure, the possibility of modification of weld metal etc.).In manual arc welding, one of the main sources of nonmetallic inclusions in the weld metal is the material of the components of the electrode coating. The inclusions may be the product of oxidation-reduction processes between the metal and the slag, and also the undissolved particles of the coating. Embrittlement depends not only on the total number of the inclusions but also on the nature, shape and distribution of the inclusions.Of special importance is the decrease in the level of contamination of the weld metal with nonmetallic inclusions from the electrode and the increase in the homogeneity of the structure in modification through the slag.In this work, investigations were carried out into the effect of the composition of the electrode coating on the cold strength of the metal of the welded joint by means of statistical analysis of the contamination of the weld Table 1 metal with inclusions and of the parameters of the structure of the weld metal. The experiments were carried out using the plan of rotating uniform design for four factors with the construction of the planning matrix 2 4 , including 31 compositions of the electrode coating. The starting composition was represented by the composition of the coating of MR-3 electrode. The intervals and the levels of variation of the factors are presented in Table 1.The investigations were carried out on specimens of St3 steel. Beads were deposited on the surface not dressed after rolling, using electrodes with a diameter of 4 mm, and a welding current of 135 A. The chemical composition of the metal, deposited with MR-3 electrode (%) was composed of: 0.06-0.0C, up to 0.15SÍ, 0.4-0.6 Mn, no more than 0.04 S and P, and other impurities.The following method of quantitative metallographic analysis of the metal of welded joints was used. Three zones, positioned 1 mm from each other, were selected on the cross-section of the metal of the welded joint with a thickness of 8 mm. The number and dimensions of the inclusions were determined on the measuring grid of the microscope in the square field with a size of 320 x 320 urn, at a magnification of 250. With this distribution, the fields of view included all the main zones of the welded joint: the weld surface, the centre, and the peripheral zone.According to the results of the previous investigations, 1 the main fraction of the inclusions is represented by the oxides of silicon SiO 2 , iron FeO (less frequently with Variation l...

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The use of laser technology in the manufacturing processes of mechanical engineering is gradually increasing. However, laser welding cannot compete with electron beam welding because the processes of the interaction of the laser beam with the plasma arising above the zone of the laser beam affecting the metal are not sufficiently studied. Of particular interest is the use of laser welding in vacuum. The study of the secondary emission signal in the zone of the laser beam affecting the metal allows one to obtain information about the plasma cloud in the zone of laser welding in vacuum. To study the secondary emission current in the laser welding zone, a computer system with an analog-to-digital interface can be used. The registered secondary emission current made it possible to estimate such parameters of the plasma arising in the laser welding zone in vacuum as the plasma concentration, electron temperature, and plasma potential.