Papers by Author: Miroslav Sahul

Abstract: Laser machining is one of the most widely used advanced noncontact machining processes used for creating new surfaces, structures, cavities and also complex electro-mechanical devices, usually with very small dimensions, by laser radiation. It is the process in which the material’s thermophysical properties rather than mechanical properties determine the machinability. Design of process parameters is highly critical for successful material removal and high machine surface quality. In the paper the laser beam milling is experimentally studied applying the nanosecond pulse fibre laser and alumina ceramic as working material. The influence of pulse energy, pulse repetition rate, scanning speed and tracks displacement on material removal efficiency and the quality of machined surface is reported.

Abstract: The influence of heat treatments on the microstructure of AISI M2 type high-speed steel obtained using conventional metallurgy has been studied. The primary focus was on the effects of austenitisation temperatures on the behaviour of the initial eutectic carbides during austenitisation. In order to investigate kinetics of both the microstructure and phase transformations in eutectic carbides upon heat treatments with respect to diffusion processes, different techniques of electron scanning microscopy and energy dispersive X-ray spectrometry have been used. The effect of the austenitisation temperature on the primary austenite grain size, martensite microstructure and volume fraction, size distribution, and morphology of the primary carbides of eutectic origin as well as their behaviour during heat treatment in the wrought M2 high-speed steel was thoroughly investigated.

Abstract: The paper concerns with welding of copper to stainless steel. Technically pure Cu and AISI 304 austenitic stainless steel with the thickness of 2.0 mm were suggested as experimental metals. TruDisk 8002 laser with the wavelength of 1.03 μm and a maximum power of 8.0 kW was used for production of dissimilar metal welds. Laser power from the range of 2.3 to 2.9 kW and welding speed from 35 to 50 mm/s were used for welding dissimilar metals. Focal position was direct on the surface of welded metals. Helium with flow rate of 17 l/min was used for shielding of molten weld metal. Light microscopy, EDX microanalysis and micro hardness measurements across copper - fusion zone - stainless steel interface were performed in order to study the properties of the weld joints.

Abstract: The paper deals with disk laser welding of magnesium alloy with the content of rare earth elements. ZE 41 magnesium alloy with the thickness of 2.0 mm was used as experimental metal. TruDisk 4002 solid state laser with a wavelength of 1.03 microns and a maximum power of 2.0 kW was used for welding of magnesium alloy. Laser power which was applied ranged from 0.6 to 1.2 kW. The focal position of laser beam was fixed on the surface of magnesium alloy and the welding speed was set to 70 mm/s. Argon with flow rate of 12 l/min was used as shielding gas. Light microscopy, EDX microanalysis and micro hardness measurements across base metal - fusion zone interface were carried out in order to analyze the weld joints.

Abstract: The contribution deals with resistance spot welding of low carbon steel to austenitic CrNi stainless steel. The thickness of welded dissimilar steels was 2 mm. DeltaSpot welding gun with process tape was utilized for welding of the above-mentioned combination of steels. Resistance spot welds were produced under different welding currents. The welding currents used were 7 kA, 7.5 kA and 8 kA, respectively. Optical microscopy, microhardness measurement across the weld joint and EDX analysis across the weld joint interface were used to evaluate the quality of resistance spot welds of dissimilar steels.

Abstract: The contribution deals with the design of a progressive metallurgical joining of the solar collector parts by brazing. The main aim was to replace flame brazing by the more advantageous technology of brazing using high-frequency induction heating. New equipment and the induction coil of a suitable shape were designed for the joint manufacturing. Based on the numerical simulations of electromagnetic and temperature fields, the basic parameters of induction brazing were suggested in order to achieve the desired temperature distribution at the spot of the future joint. To check the quality of the brazed joints, a leak test, optical microscopy and EDX microanalysis were used to study the area of the brazed joints interface. Impact of brazing time and power supply on brazeability of Al alloys components by means of the AlSi12 braze were assessed.

Abstract: The contribution deals with the initial design and numerical simulation of brazing process for components of solar collectors from copper-brass combined materials by the use of CuP7 brazing alloy with application of induction heating. The purpose of the contribution is to evaluate the suitability of designed inductor and its operation frequency for the given application on the basis of coupled numerical analysis of electro-magnetic and thermal fields by the ANSYS software. The attained results confirmed that using suggested arrangement of induction heating it is possible to ensure the brazing alloy melting and the development of a sound joint without undesirable overheating of brazed components or surface melting of brass flange. When increasing the frequency, the heating period is shorter but the maximum temperature of the brass component slightly increases.