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1

Analysis of the Microstructure And Mechanical Properties of Duplex Steel Joints

Witkowska Małgorzata, Kowalska Joanna, Chronowska-Przywara Kinga

Tribologia

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2024

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nr 1

147--158

EN

The article presents a study, the aim of which was to analyze the microstructure and mechanical properties of welded joints of austenitic-ferritic duplex steel X2CrMnNiN21-5-1. This steel is characterized by good resistance to various types of corrosion, good strength properties and good weldability. Due to all these advantages, it is used in many industry sectors, and the main joining techniques are welding technologies. In this study, two joining techniques were used, SMAW (Shielded Metal Arc Welding) and GTA (Gas Tungsten Arc). The obtained welded joints were subjected to: macroscopic and microscopic metallographic tests, mechanical tests (static bending test and microhardness measurements), diffraction tests, and wear resistance tests. The results showed that the microhardness of the welds is similar and does not depend on the welding method used. In the microstructure of the analyzed joints there are two phases: austenite (γ) and ferrite (δ), with different morphologies depending on the welding conditions, which affect the phase transformations. Material wear within the weld is greater than in the base material.

PL

Celem badań była analiza mikrostruktury i własności mechanicznych złączy spawanych stali austenityczno-ferrytycznej typu duplex X2CrMnNiN21-5-1. Stal ta charakteryzuje się dobrą odpornością na różnego rodzaju korozje, dobrymi własnościami wytrzymałościowymi i dobrą spawalnością. Dzięki tym wszystkim zaletom znajduje zastosowanie w wielu gałęziach przemysłu, a głównymi technikami jej łączenia są technologie spawalnicze. W pracy zastosowano dwie techniki łączenia metodą SMAW (Shielded Metal Arc Welding) i GTA (Gas Tungsten Arc). Uzyskane złącza spawane poddano: badaniom metalograficznym makro- i mikroskopowym, badaniom mechanicznym (statyczna próba zginania i pomiary mikrotwardości), badaniom dyfrakcyjnym oraz badaniom odporności na zużycie. Wyniki badań pokazały, że mikrotwardości spoin są zbliżone i nie zależą od zastosowanej metody spawania. W mikrostrukturze analizowanych złącz występują dwie fazy austenit (γ) i ferryt (δ) o zróżnicowanej morfologii zależnej od warunków spawania, które wpływają na przemiany fazowe. Zużycie materiału w obrębie spoiny jest większe aniżeli w materiale rodzimym.

2

The Influence of Cold Deformation and Annealing on Texture Changes in Austenitic Stainless Steel

Kowalska Joanna, Witkowska Małgorzata

Advances in Science and Technology. Research Journal

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2024

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Vol. 18, no 2

143--158

EN

Austenitic stainless steels are widely used in industry, from heavy industry and power generation to precision mechanics and electronics, accounting for about 2/3 of the stainless steels produced. The stability of austenite influences the properties and behaviour of these steels during deformation and annealing. This paper presents the results of research into austenitic metastable phase X5CrNi1810 steel, which was subjected to cold rolling (in the range of 5 to 80%) and then annealing (at temperatures of 500-900°C). The research focused mainly on changes in crystallographic texture parameters occurring during the analysed processes. It was found that the observed development of the deformation texture is complex due to the fact that several processes take place simultaneously. Namely, the deformation of austenite, the transformation of austenite into martensite, and the deformation of the resulting martensite. The texture of the deformed austenite was similar to the texture of the alloy type {112}<110>. After 80% deformation, the Goss-type {110}<001> texture component showed the highest intensity. The lack of {112}<111> orientation in the texture was due to the fact that this orientation changes to the {112}<110> martensite orientation as a result of the γ→α’ phase transition. Annealing of the deformed steel at 500°C led to an increase in the degree of texturing (sharpening of the texture), which was related to the improvement of the texture in this temperature range. Above 600°C, the degree of texturing decreased, which is directly related to the α’→γ reverse transformation and the subsequent recrystallization process. Magnetic studies indicate an increasing proportion of the magnetic phase α’ (martensite) together with an increasing degree of deformation. For deformation of 80%, the amount of magnetic phase reached a value of more than 33%. However, after annealing at a temperature of 800°C, there is no martensite in the structure, which indicates that, in these heat treatment conditions, the complete reverse transformation of martensite into austenite has already taken place.

3

Influence of galvanizing time on microstructure and microhardness of coating layers on selected structural steels

Witkowska Małgorzata

Inżynieria Materiałowa

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2023

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Vol. 44, nr 2

5--11

EN

Changes in microstructure and microhardness are reported, depending on the processing parameters of galvanizing Fe-0.4Mn-0.02Si (S235) and Fe-1.4Mn-0.2Si (S355) steel substrates. The thickness of the coatings depended primarily on the dipping time, 4 and 8 min, which was confirmed by magnetic measurements. XRD analysis and SEM observations revealed typical structures of galvanized coatings, composed of η, ζ, δ and Γ. Microhardness measurements showed that the inner layer δ has the highest microhardness and the phase η has the lowest microhardness. Zn coatings on the Fe-0.4Mn-0.02Si substrate (very low Si content) are characterized by higher adhesion and durability compared to the coatings on Fe-1.4Mn- 0.2Si (higher silicon content).

PL

Przedstawiono zmiany mikrostruktury i mikrotwardości w zależności od parametrów procesu cynkowania na podłożu stali Fe-0,4Mn-0,02Si (S235) i Fe-1,4Mn-0,2Si (S355). Grubość powstałych powłok zależała przede wszystkim od czasu zanurzenia (4 i 8 min), co potwierdziły pomiary magnetyczne. Analiza XRD i obserwacje SEM ujawniły typowe struktury powłok ocynkowanych, złożone z η, ζ, δ i Γ. Pomiary mikrotwardości wykazały, że warstwa wewnętrzna δ ma największą mikrotwardość, a warstwa η najmniejszą. Powłoki Zn na podłożu Fe-0,4Mn-0,02Si (bardzo mała zawartość Si) charakteryzują się lepszą przyczepnością i trwałością w porównaniu z powłokami na Fe-1,4Mn-0,2Si (większa zawartość Si).