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The application of cluster analysis in the assessment of the weldability of unalloyed steels

Szewczyk Anna, Górska Klaudia, Wolski Adrian, Fydrych Dariusz

Biuletyn Instytutu Spawalnictwa w Gliwicach

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2023

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Vol. 67, No. 3

5--12

EN

Non-alloy steels constitute a large group of steels characterised by diversified chemical composition, structural morphology and a wide range of mechanical properties (determining weldability). The paper presents results of multidimensional analyses (based on cluster analysis) of 110 selected unalloyed steel grades. Properties adopted as diagnostic features included the chemical composition, mechanical properties (yield point) and values of selected indicators concerning susceptibility to technological crack formation. The analyses (performed using Ward’s and k-means methods) resulted in a division of the 110 steels into five steel groups (clusters). The comparison of results obtained using two clustering methods and involving various classification criteria revealed that multidimensional analyses constituted a prospective method making it possible to assess the weldability of steels. However, results of such multidimensional analyses should be subjected to thorough and substantive analyses.

PL

Stale niestopowe stanowią liczną grupę stali charakteryzujących się zróżnicowanym składem chemicznym, budową strukturalną oraz szerokim zakresem właściwości mechanicznych, co determinuje ich spawalność. W artykule przedstawiono wyniki analiz wielowymiarowych z wykorzystaniem analizy skupień wybranych 110 gatunków stali niestopowych. Jako cechy diagnostyczne przyjęto skład chemiczny, właściwości mechaniczne (granicę plastyczności) oraz wartości wybranych wskaźników skłonności do pęknięć technologicznych. Analizy przeprowadzono metodami Warda i k-średnich, uzyskując podział na pięć grup stali. Z porównania wyników otrzymanych dwoma metoda grupowania i dla różnych kryteriów klasyfikacji wynika, że analizy wielowymiarowe stanowią perspektywiczną metodę oceny spawalności stali, jednak ich wyniki należy poddać starannej analizie merytorycznej.

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Effect of Arc Strikes on High Strength Low Alloy Steels Welded by SMAW

Fydrych Dariusz, Raczko Przemysław, Świerczyńska Aleksandra, Landowski Michał, Wolski Adrian, Rogalski Grzegorz

Advances in Science and Technology. Research Journal

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2023

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Vol. 17, no 3

160--169

EN

Wet welding with covered electrodes (Shielded Metal Arc Welding-SMAW) is the most commonly used method of carrying out welding repair works in a water environment. Limited visibility and the inability to move freely under water result in an increased risk of formation of welding imperfections such as lack of fusion, lack of penetration and arc strikes. The work focused on changes in the properties and structure of steel subjected to the impact of short (0.2 s) arc ignitions generated by covered electrodes in air and under water for three high strength steel grades: S460N, S460M and S500MC. Visual tests, macroscopic and microscopic metallographic tests, microhardness measurements and diffusible hydrogen content in deposited metal determination were performed. A significant influence of the environment on changes in the morphology and microhardness of steel in the vicinity of arc strikes was found. The microhardness of the areas covered by the rapid thermal cycle caused by SMAW increased from 200-230 HV0.5 to 400-500 HV0.5 depending on the steel grade. The presence of welding imperfections: cavities and cracks were detected. The susceptibility of all steel grades subjected to short thermal cycles to cracking was confirmed by the results of measurements of the diffusible hydrogen content: 38.6 ml/100g and 84.5 ml/100 g for air and water environment, respectively. No influence of changes in the welding current on the behavior of the material in the tested conditions was found. The conducted research shows that leaving arc strikes on the structure may have serious consequences and cause a failure.

3

Effects of storing flux-cored wires under various conditions

Świerczyńska Aleksandra, Landowski Michał, Wolski Adrian, Lentka Grzegorz, Łabanowski Jerzy, Fydrych Dariusz

Biuletyn Instytutu Spawalnictwa w Gliwicach

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2022

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Vol. 66, No. 6

37--45

EN

Welding processes involving the use of flux-cored wires are becoming increasingly popular, particularly in shipbuilding as well as in off-shore and civil engineering. The article presents characteristics of the welding process, its areas of application as well as advantages and disadvantages (e.g. necessity of ensuring appropriate conditions for the storage of filler metal wires). The satisfaction of quality-related requirements concerning welded joints necessitates controlling the quality of flux-cored wires as their condition (apart from welding conditions) is one of the most important factors affecting the welding process and the quality of joints. The analysis of related reference publications and individual study revealed that the storage of wires under conditions inconsistent with requirements specified by producers affects welding process stability and weld deposit properties. Visual tests (VT) tasked with assessing the quality of wire surface do not always provide sufficient information as regards the usability of filler metal wires in welding processes.

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Bead-on-Plate Underwater Wet Welding on S700MC Steel

Tomków Jacek, Świerczyńska Aleksandra, Landowski Michał, Wolski Adrian, Rogalski Grzegorz

Advances in Science and Technology. Research Journal

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2021

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Vol. 15, no 3

288-296

EN

The participation of high strength steels in marine and offshore structures is increasing, which makes it necessary to develop recommendations for underwater repair welding works. The article presents the results of bead-on-plate welded specimens made of S700MC high strength steel in underwater wet welding conditions by covered electrodes. Three specimens with heat input values in the range 0.91-1.05 kJ/mm were made. The specimens were subjected to visual, metallographic, macro- and microscopic tests as well as hardness measurements using the Vickers method. It was found that the higher heat input leads to formation of mixed bainite-martensite microstructure in the heat-affected zone (HAZ). Lower heat input value results in presence of martensite in HAZ. It was shown that in the scope of the performed tests, the maximum hardness of HAZ did not exceed the critical value for the material group, and the increase in heat input caused the decrease of hardness by about 25 HV10.

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Determination of moisture resistance of covered electrodes according to PN-EN ISO 14372

Mielnicka Katarzyna, Wolski Adrian, Świerczyńska Aleksandra, Rogalski Grzegorz, Fydrych Dariusz

Welding Technology Review

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2019

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R. 91, nr 7

23--30

EN

Moisture present in the electrode covering is one of the sources of diffusible hydrogen in welded joints. In order to study the diffusible hydrogen content in deposited metal, a stand for moisturizing covered electrodes, in accordance with the PN-EN ISO 14372 standard, was built. After the stand was completed, a test of moisturizing the electrodes was carried out and measurements of the diffusible hydrogen content in deposited metal using the mercury method (according to PN-EN ISO 3690) were conducted. The research was aimed at verifying the correctness of the operation of test stand and indirect determination of the influence of storage of rutile-cellulose and cellulose electrodes under fixed conditions on the degree of moisturizing of the weld metal. Both tested electrode grades belong to the group of electrodes with a standard covering.

PL

Wilgoć obecna w otulinie elektrod jest jednym ze źródeł wodoru dyfundującego w złączu spawanym. W celu zbadania zawartości wodoru dyfundującego w stopiwie zbudowano stanowisko do nawilżania elektrod otulonych zgodnie z PN-EN ISO 14372. Po wykonaniu stanowiska badawczego przeprowadzono próbę nawilżania elektrod oraz pomiary ilości wodoru dyfundującego w stopiwie metodą rtęciową (wg PN-EN ISO 3690). Badania miały na celu zweryfikowanie poprawności działania stanowiska oraz pośredniego określenia odporności otuliny elektrod celulozowych i rutylowo-celulozowych na wilgoć. Obydwa badane gatunki elektrod zaliczono do grupy elektrod z otuliną standardową.