Milan Turňa

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.

The Effect of Atmosphere and Vacuum on Character of Weld Joints Fabricated by Explosion

This paper presents an experiment conducted in Explosia, a.s., Pardubice. A bimetal prepared of AZ 31 Mg alloy - CrNi austenitic steel was tested in various conditions, and consequently its quality was assessed. Focus was particularly on the impact of atmosphere and vacuum on the interface character of the metals (bimetals) prepared by explosion. Parallel placement of the materials being welded was used for welding in both vacuum and air atmosphere. Welding sets were designed and manufactured. The welding parameters and conditions were set up utilising the available computational means, and then verified by simulation in ANSYS engineering-scientific program. Used was Semtex S 35, a loose explosive, as well as Startline 12, an initiation explosive. Bimetal was fabricated in the air atmosphere at the detonation speed 2613 m.s-1 and in vacuum at the detonation speed 2597 m.s-1. Quality of bimetals was assessed by optical microscopy, measuring deformations by a 3D scanner, measuring microhardness and also by EDX microanalysis.

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.

Application of Induction Heating for Brazing Parts of Solar Collectors

This paper reports on the application of induction heating for brazing parts of solar collectors made of Al alloys. The tube-flange joint is a part of the collecting pipe of a solar collector. The main task was to design an induction coil for this type of joint, and to select the optimum brazing parameters. Brazing was performed with AlSi12 brazing alloy, and corrosive and non-corrosive flux types were also applied. The optimum brazing parameters were determined on the basis of testing the fabricated brazed joints by visual inspection, by leakage tests, and by macro- and micro-analysis of the joint boundary. The following conditions can be considered to be the best for brazing Al materials: power 2.69 kW,brazing time 24 s, flux BrazeTec F32/80.

Study of Explosion Welding of Mg Alloy with Aluminium

The aim of the present work was to solve the technology for welding Mg alloy type AZ 63 with aluminium and to assess the quality of the fabricated joints (bimetals-composites). In solving the welding technology, the high affinity of Mg to oxygen has to be considered and therefore as suitable technology either metallurgical joining in vacuum (electron beam etc.) or high-speed solid state welding seem to be feasible. Explosion welding with Semtex S 30 explosive was approved experimentally. Parallel arrangement of welded materials was applied. The more plastic Al material was accelerated. Quality of bonds (bimetals) was assessed by defectoscopy (ultrasound), optical microscopy, microhardness measurement and X-ray microanalysis. It can be generally stated that the basic requirement on joint quality (namely the undulated boundary) was met. The structural composition and absence of inhomogeneities in fabricated bimetals suggest that the desired quality was achieved.

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.

Design of Binary Zinc‐Based Solder for Joining Mg Alloy Type AZ 31 B

The aim of article is to design a brazing alloy and flux for brazing magnesium alloy type AZ 31B, to fabricate brazed joints and to assess their quality. The brazing alloy and flux were designed on the basis of knowledge attained from the study of literature and information from technical practice. Regarding the fact that it was impossible to get more detailed information mainly about the chemical composition of brazing alloys and fluxes for brazing Mg alloys, it was finally decided that the brazing alloy and the flux would be designed in our laboratories. Joint quality was assessed by light microscopy, microhardness measurement, EDX microanalysis and analysis of fractured surfaces.

Friction Stir Welding of Mg and Al Alloys

The work deals with welding of aluminium alloy typeAlMg4,5Mn and magnesium alloy type AZ 31 in solid state by FSW (Friction Stir Welding) process. Experiments were performed in cooperation with VÚZ PI SR (Welding Research Institute Industrial Institute of Slovak Republic) Bratislava, which has available a new installed equipment type FSW LM 060 manufactured in China. Welding parameters and conditions were proposed and approved. Quality of fabricated joints was assessed by optical microscopy, micro hardness measurement and radiographic test - RT. It was supposed that optimisation of welding parameters would allow to fabricate the joints of acceptable quality that might compete to technologies of fusion welding, including welding with concentrated power sources.

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.