Under the influence of heat load and Zn diffusion in resistance spot welding of galvanized steel sheets, significant changes occur on the contact area of CuCrZr welding electrodes which lead to their erosion damage. Changes, causing wear of electrodes not only affect the welding process but also the quality and properties of the weld. Apart from the traditional solution (for example, the so-called "Slope" welding current) the wear of the contact surfaces can be affected by using the barrier layers -coatings. Main goal for the use of material barrier is to minimize the structural changes caused by Zn diffusion, erosion and higher heat resistance of the electrode. Recent studies have shown that such a suitable coating is a multilayer system (Ni/TiB2). This paper is focused on the assessment of changes in the contact area of the electrodes and the barrier layer Ni / TiB2 after compila-tion 0, 1, 5, 20 and 100 welds on galvanized steel sheets type HX220BD Z100MBO.

Current trend of maximum utilization of properties of metal materials forces the fabricators to use different materials for different construction parts. Thus the fabricators of welded constructions, such as automobile constructions, today combine cold rolled steel plates with high strength low alloy steel as well as with aluminium or its alloys. Especially metallurgical joining of steel to aluminium represents certain issues resulting from different physical properties (e.g. different melting point temperature). Following paper is focused on the analysis of utilization possibilities of plasma arc at the performance of zinc coated steel to aluminium heterogenic joints and on the comparison with the MIG process using the AlSi5 filler material. K e y w o r d s : joining of dissimilar materials, plasma arc welding, MIG welding, aluminium, coated plates

Projection welding belongs to the group of resistance welding technologies. The basic process parameters are the welding current and the current flow time. The resistance projection weldability of the fasteners on metal sheets is not as well understood as the resistance spot weldability of the sheets, so complex studies for the wider application of resistance welding of nuts in the automotive industry are still needed. This research is aimed at valuation the effect of resistance projection welding parameters (steel nuts on galvanized steel sheet DP 600) on joint properties. The hard welding mode (high welding current, clamping force and short welding time) provided 2 times higher strength of the weld joints as the soft welding mode. When using the soft welding mode, an increased Zn concentration from the sheet metal coating was measured in the transition area between the welded materials at the folding locations. When applying the hard welding mode, only a slight increase in the Zn concentration was observed at the inner boundary of the weld joint.

To build the car body parts of today's cars, materials of higher strength are used on an ever-wider scale. They are, for example, boron-containing steels, which are highly resistant to special thermo-mechanical processing, coated with AlSi; e.g. USIBOR 22MnB5 type materials. For the final assembly of all body mounting components, it is necessary to apply different types of joining stud elements. One of the possibilities of making joinings between sheets and fastening elements -studs is the technology of short-circuit stud welding This article aims to evaluate the influence of welding parameters of steel studs on high-strength steel sheet type USIBOR 22MnB5 with AlSi coating on selected mechanical properties of joints.

Abstract:The application of different types of materials, e.g. coated high-strength materials and galvanized steels in the manufacturing of car bodies, requires the verification of their weldability. Despite the application of new, unconventional fusion welding technologies (CMT, laser), resistance spot welding holds a dominant position in the production of car bodies of lower and middle class. Resistance welding technology is characterized by a high rate of heating and cooling, thus affecting the final properties of the welded joint. The paper is focused on the structure analysis of the welded joint of high strength steel USIBOR 22MnB5 with Al-Si coating and galvanized mild steel H340LAD+Z140-M-B-O made by resistance spot welding.