BIULETYN INSTYTUTU SPAWALNICTWA No. 2/2019 69 Lechosław Tuz, Krzysztof Sulikowski Microstructure and Selected Mechanical Properties of Welded Joints in Austenitic Perforated Bottoms Made Using the Automated TOP TIG Method Abstract: Te article presents selected test results obtained during welding tests preceding a Welding Procedure Qualifcation, performed using a robotic TOP TIG welding station. Te test results revealed the obtainment of welded joints characterised by proper geometry and proper austenitic structure. In addition, the article presents typical welding imperfections observed in relation to the adjustment of welding process parameters, i.e. hot cracks in the weld root area and cavities. Keywords: perforated bottom, arc welding, austenitic steel doi: 10.17729/ebis.2019.2/7 Introduction Heat exchangers are important system compo- nents in the refning, petrochemical and chem- ical industries as well as in industrial power engineering, heat engineering and gas engineer- ing [1]. Extensive applications of heat exchang- ers necessitate the adjustment of their design to specifc needs of both a given industrial sector and system. As a result, heat exchangers vary both in terms of their dimensions, the manner of assembly (i.e. one-way or multi-way systems) and materials they are made of (e.g. unalloyed steels, fne-grained steels, stainless steels, creep resisting steels, clad steel, aluminium alloys or nickel alloys) [1-5]. Te design of heat exchang- ers and their materials are always adjusted to operating parameters, including the type, tem- perature, aggressiveness and the fow rate of media. [3-5]. However, in spite of design custo- misation, it is possible to diferentiate between various types of heat exchangers, e.g. heat ex- changers with straight tubes and permanent perforated walls, with foating heads, U-shaped or helicoidal. Te exchanger design includes an external jacket (external housing) and an in- ternal part consisting of properly shaped tubes, barriers and perforated walls adjusting the fow of medium inside the exchanger. Te complexity of design as well as applied structural solutions signifcantly afect the ser- vice life of heat exchangers and their heat ex- change efciency. As a result, each “tailor-made” heat exchanger requires the adjustment of man- ufacturing processes to enable the obtainment of required product quality, including the sat- isfaction of gas directive requirements. As can be seen, the making of an appropriate product requires a number of operations, from the de- sign and selection of materials, through pro- duction planning to the fabrication of a product dr inż. Lechosław Tuz (PhD (DSc) Eng.) – AGH University of Science and Technology in Kraków; mgr inż. Krzysztof Sulikowski (MSc Eng.) – Roboty Przemysłowe Sp. z o.o., Kraków