Effect of weld metal chemistry and heat input on the structure and properties of duplex stainless steel welds
15 Oct 2003-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing (Elsevier)-Vol. 358, Iss: 1, pp 9-16
TL;DR: In this article, a low heat input process viz., EBW and another commonly employed process, gas tungsten-arc welding have been employed for welding of duplex stainless steels with and without nickel enhancement.
Abstract: The excellent combination of strength and corrosion resistance in duplex stainless steels (DSS) is due to their strict composition control and microstructural balance. The ferrite–austenite ratio is often upset in DSS weld metals owing to the rapid cooling rates associated with welding. To achieve the desired ferrite–austenite balance and hence properties, either the weld metal composition and/or the heat input is controlled. In the current work, a low heat input process viz., EBW and another commonly employed process, gas tungsten-arc welding have been employed for welding of DSS with and without nickel enhancement. Results show that (i) chemical composition has got a greater influence on the ferrite–austenite ratio than the cooling rate, (ii) and even EBW which is considered an immature process in welding of DSS, can be employed provided means of filler addition could be devised.
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TL;DR: In this paper, the effects of short time aging at 475 °C on the mechanical properties and localized corrosion resistance of a cast DSS were analyzed and the results showed that mechanical properties such as toughness and hardness are more susceptible to aging, having already been affected during the first 4 hours of heat treatment, while the corrosion was affected in 12 h of aging.
Abstract: Duplex stainless steels (DSS) are Fe-Cr-Ni-Mo alloys, with low carbon content, which have a favorable combination of mechanical properties and corrosion resistance. These characteristics are mainly attributed to a dual phase and refined microstructure, typical of these alloys, consisting of similar amounts of ferrite and austenite. For this reason, DSS are widely used in various segments of industry, especially in offshore applications. However, DSS components may have a decrease of their properties when they are exposed high temperatures, often due to incorrect manufacturing processes. Intermetallic phases may precipitate causing embrittlement and corrosion resistance decrease. This work presents the effects of short time aging at 475 °C on the mechanical properties and localized corrosion resistance of a cast DSS. The results show that mechanical properties, such as toughness and hardness, are more susceptible to aging, having already been affected during the first 4 hours of heat treatment, while the corrosion was affected in 12 h of aging.
5 citations
TL;DR: In this paper, super duplex stainless steel (UNS S32750) butt joints were prepared using ER2594 and ER2595 electrodes by shielded metal arc welding (SMAW) process.
Abstract: Super duplex stainless steel (UNS S32750) butt joints were prepared using ER2594 and ER2595 electrodes by shielded metal arc welding (SMAW) process. The heat input used during welding was in the range of 0.75–0.81 kJ/mm. Microstructure and texture across the weldments were investigated using optical microscope, scanning electron microscope, and electron backscattered diffraction. The solidification mode in the fusion zone (FZ) was found to be ferritic, and the microstructure mainly consisted of Widmanstatten austenite (WA), grain boundary austenite (GBA), and inter-granular austenite (IGA). The base metal (BM) had ~ 50% ferrite and 50% austenite. The ferrite proportion changed significantly in FZ and heat-affected zone (HAZ) after welding. Austenite in the BM showed strong Brass ({110} ), Cu ({112} ), Goss ({110} ), and S ({123} ) components, while ferrite showed strong α (RD// ) and γ (ND// ) fibres. The texture of ferrite was stronger than that of austenite. The austenite and ferrite in the FZ (cap pass) obeyed Kurdjumov–Sachs (K–S) orientation relationship. Further, the hardness of ER2595 weldments was found to be higher than that of ER2594 weldments.
5 citations
Dissertation•
01 Jan 2015
TL;DR: In this article, a coupled CFD and FEM numerical model was developed to assist in understanding the melt pool dynamics and transportation processes of alloying elements, and a series of experiments were performed to verify the developed thermo-metallurgical FEA model and a good qualitative agreement of the predicted martensitic phase distribution is shown to exist.
Abstract: Laser welding of metals and alloys is extensively used in industry due to its advantages of controlled heating, narrow weld bead, low heat affected zone (HAZ) and its ability to weld a wide range of metals and dissimilar metals. Laser welding of dissimilar metals such as carbon steels and stainless steel is still a challenging task, particularly due to the formation of brittle phases in the weld, martensitic formation in the HAZ and solidification cracking in the fusion zone. These issues can significantly deteriorate the strength of the welded joint. The aim of this work is to investigate the fundamental phenomena that occur inside the dissimilar weld zone and their effect on weld quality. In order to establish the key process variables, an initial study concentrated on the effect of different laser process parameters on dissimilar weld quality. In the second part of the work, a comprehensive study was performed to understand and subsequently control the alloying composition in laser dissimilar welding of austenitic stainless steel and low carbon steel. A dissimilar weld that is predominantly austenitic and homogeneous was obtained by controlling the melt pool dynamics through specific point energy and beam alignment. The significance of dilution and alloying elements on joint strength was established. A coupled CFD and FEM numerical model was developed to assist in understanding the melt pool dynamics and transportation processes of alloying elements. The model has been validated by a series of laser welding experiments using various levels of specific point energy. The laser welding characteristics in terms of geometric dimensions, surface morphology, alloying concentration, and dilution, were compared, and it is concluded that the specific point energy and laser beam position are the key parameters that can be controlled to obtain a weld bead with characteristics most suitable for industrial applications. In the third part of the work, a comparative study was performed to understand the significance of cooling rate, and alloying composition on the microstructure and phase structure of the dissimilar weld zone. Results show that the HAZ within the high carbon steel has significantly higher hardness than the weld area, which severely undermines the weld quality. A new heat treatment strategy was proposed based on the results of the numerical simulation, and it is shown to control the brittle phase formation in HAZ of high carbon steel. A series of experiments was performed to verify the developed thermo-metallurgical FEA model and a good qualitative agreement of the predicted martensitic phase distribution is shown to exist. Although this work is presented in the context of dissimilar laser welding of mild steel to stainless steel, the concept is applicable to any dissimilar fusion welding process.
5 citations
Cites background from "Effect of weld metal chemistry and ..."
...[245], investigated the effect of weld chemical composition, and heat input on the structure and properties of duplex stainless steel welds....
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TL;DR: In this paper, the influence of nitrided weld edge surfaces on metallurgical properties of the resulting welded joint was investigated, and the effect of increased nitrogen effusion from the weld pool was investigated.
Abstract: Duplex stainless steel is common in thick-walled components such as longitudinal welded pipes in the oil and gas industries and as parts of various machines in the chemical and food industries. Electron beam welding is a very suitable method for welding such components. Due to the high power density of the electron beam combined with the decreased evaporation temperature in a vacuum atmosphere, steel with a sheet thickness of up to 150 mm can be welded in one pass. In the case of the electron beam welding of duplex stainless steels, vacuum atmosphere in the working chamber causes a nitrogen effusion from the weld pool. The microstructure of the resulting weld is characterized by an unacceptable high ferrite content, which is the main reason for both low impact toughness and low pitting corrosion resistance. This work focuses on the influence of nitrided weld edge surfaces on metallurgical properties of the resulting welded joint. The aim here is to investigate the effect of increased nitrogen con...
5 citations
TL;DR: In this paper, the influence of multipass welding heat input on the microstructure and mechanical properties of the heat affected zone (HAZ) of UNS S31803 duplex stainless steel multipass welded joints was evaluated.
Abstract: The aim this work is to evaluate the influence of multipass welding heat input on the microstructure and mechanical properties of the heat affected zone (HAZ) of UNS S31803 duplex stainless steel multipass welded joints. The shielded metal arc welding process using as filler metal the AWS E2209-17 covered electrode were employed had been carried through V joint groove UNS S31803 DSS, so that two levels of energy (15 and 20 kJ/cm) had been used in this experiment. The condition welded with higher energy higher a HAZ extensive and coarser microstructure in the finishing passes. On the other hand, in the wadding passes and root pass, the HAZ this region was more refined and less extensive. In respect of microhardness, the condition welded with energy of 15 kJ/cm got lower levels. In relation to toughness, it was not observed significant differences.
4 citations
Additional excerpts
...[7] MUTHUPANDI, V....
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...É primordial a obtenção do balanço microestrutural de 50% austenita e 50% ferrita de modo a aliar boas propriedades mecânicas e boa resistência à corrosão [7]....
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References
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Book•
01 Jan 1997
TL;DR: In this paper, the authors present a non-destructive testing of welds for service experience, based on the application of service experience in metallurgy and metallurgical applications.
Abstract: Developments, grades and specifications Alloy design Microstructure Forming and machining Physical and mechanical properties Corrosion Stress corrosion cracking Welding metallurgy Welding processes Weld properties Non-destructive testing of welds Applications Service experience.
449 citations