Miroslav Sahul

Resistance Spot Welding of dissimilar Steels

This paper presents an analysis of the properties of resistance spot welds between low carbon steel and austenitic CrNi stainless steel. The thickness of the welded dissimilar materials was 2 mm. A DeltaSpot welding gun with a process tape was used for welding the dissimilar steels. Resistance spot welds were produced with various welding parameters (welding currents ranging from 7 to 8 kA). Light microscopy, microhardness measurements across the welded joints, and EDX analysis were used to evaluate the quality of the resistance spot welds. The results confirm the applicability of DeltaSpot welding for this combination of materials.

Resistance Spot Welding of Low Carbon Steel to Austenitic CrNi Stainless Steel

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.

Welding of Dissimilar Light Metals by Disk Laser

The paper deals with the welding of dissimilar light metals by TruDisk 4002 disk laser. AZ 31 magnesium alloy with the thickness of 1.0 mm and AW 5754 aluminium alloy with the thickness of 1.5 mm were selected as materials to be welded. The dissimilar welded metals were arranged in the overlapped configuration. Magnesium alloy was selected as an upper plate because of higher absorption of laser radiation. Argon with 30 l/min flow rate was used as shielding gas. Different focusing of laser beam was employed in order to decrease the power density and thus eliminate cracking of produced welds. Welded joints were produced through conduction mode of laser welding. Analysis of the welded joints was carried out by light microscopy, microhardness measurement and EDX analysis. Presence of a hard and brittle intermetallic compounds was observed at the weld metal/aluminium alloy interface.

Diffusion Induced Changes in Eutectic Carbides in Wrought M2 High-Speed Steel at Austenitising

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.

Design of Laser Welding Parameters for Joining Ti Grade 2 and AW 5754 Aluminium Alloys Using Numerical Simulation

Joining of dissimilar Al-Ti alloys is very interesting from the point of view of weight reduction of components and structures in automotive or aerospace industries. In the dependence on cooling rate and chemical composition, rapid solidification of Al-Ti alloys during laser welding can lead to the formation of metastable phases and brittle intermetallic compounds that generally reduce the quality of produced weld joints. The paper deals with design and testing of welding parameters for preparation of weld joints of two sheets with different thicknesses from titanium Grade 2 and AW 5754 aluminium alloy. Temperature fields developed during the formation of Al-Ti butt joints were investigated by numerical simulation in ANSYS software. The influence of laser welding parameters including the laser power and laser beam offset on the temperature distribution and weld joint formation was studied. The results of numerical simulation were verified by experimental temperature measurement during laser beam welding applying the TruDisk 4002 disk laser. The microstructure of produced weld joints was assessed by light microscopy and scanning electron microscopy. EDX analysis was applied to determine the change in chemical composition across weld joints. Mechanical properties of weld joints were evaluated using tensile tests and Vickers microhardness measurements.

Study of ZE10 Magnesium Alloy Welded Joints Produced with Disk Laser

The paper deals with the study of weldability of magnesium alloy with the addition of rare earth elements. ZE10 magnesium alloy with 0.06 wt. % of La and 0.08 wt. % of Ce was suggested as base material. The thickness of ZE10 magnesium alloy was 1.65 mm. TruDisk 4002 laser with the power of 2.0 kW was used for production of welded joints. Bead on plate welds were produced with various welding parameters. Laser power ranged from 0.5 kW to 1.8 kW, welding speed was in the range from 30 mm/s to 90 mm/s, focusing of the laser beam was within the range of -3 to 3 mm. Shielding gases argon, helium and nitrogen were used for protection of the weld pool against the ambient atmosphere. Light and electron microscopy, microhardness measurements across the welded joints interface and tensile test were utilized to analyze the welded joints.

Friction Stir Welding of Magnesium Alloy Type AZ 31

The paper deals with welding of Mg alloy of the type AZ 31 by Friction Stir Welding technology (FSW). The FSW technology is at present predominantly used for welding light metals and alloys, as aluminium, magnesium and their alloys. Experimental part consists of performing the simulation and fabrication of welded joints on a new-installed welding equipment available at the Welding Research Institute — Industrial Institute of SR Bratislava. Welding tools made of tool steel type H 13 were used for welding experiments. Geometry of welding tools was designed on the base of literature knowledge. Suitable welding parameters and conditions were determined using numerical simulation. Main emphasis was laid upon the tool revolutions, welding speed and tool bevel angle. The effect of welding parameters on the quality of welded joints was assessed. Assessment of welded joints was carried out by radiography, light microscopy, hardness measurement and EDX microanalysis. Static tensile test was employed for mechanical testing.

Brazing of Aluminum Tubes Using Induction Heating

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.

Application of High-Frequency Induction Heating for Brazing of Dissimilar Metals

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.