Welding Metallurgy of
01 Jan 1987-
About: The article was published on 1987-01-01 and is currently open access. It has received 991 citations till now. The article focuses on the topics: Welding.
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TL;DR: In this paper , the potential of DED for manufacturing graded materials and for component repair is elaborated while highlighting the key-associated challenges and possible solutions, and some critical issues and research directions that would help develop DED further and extend its application potential are identified.
Abstract: ABSTRACT Amongst the many additive manufacturing (AM) techniques, directed energy deposition (DED) is a prominent one, which can also be used for the repair of damaged components. In this paper, we provide an overview on it, with emphasis on the typical microstructures of DED alloys and discuss the processing-microstructure-mechanical property correlations. Comparison is made with those manufactured using the conventional techniques and those obtained with laser beam powder bed fusion (LB-PBF). The characteristic solidification rates and thermal histories in DED result in distinct micro- and meso-structural features and mechanical performance, which are succinctly summarized. The potential of DED for manufacturing graded materials and for component repair is elaborated while highlighting the key-associated challenges and possible solutions. Modelling and simulation studies that facilitate an in-depth understanding of the DED technique are summarized. Finally, some critical issues and research directions that would help develop DED further and extend its application potential are identified.
16 citations
Dissertation•
04 Jul 2014
TL;DR: In this article, a 3D coupled Cellular Automaton (CA) and Finite Element (FE) model is proposed to predict the grain structure formation during multiple passes Gas Tungsten Arc Welding (GTAW) and Gas Metal Arc welding (GMAW).
Abstract: Grain structure formation during fusion welding processes has a significant impact on the mechanical strength of the joint. Defects such as hot cracking are also linked to the crystallographic texture formed during the solidification step. Direct simulation of three-dimensional (3D) grain structure at industrial scale for welding processes is rarely modeled. In this work, a 3D coupled Cellular Automaton (CA) – Finite Element (FE) model is proposed to predict the grain structure formation during multiple passes Gas Tungsten Arc Welding (GTAW) and Gas Metal Arc Welding (GMAW). At the macroscopic scale, the FE model solves the mass, energy and momentum conservation equations for the whole system based on an adaptive mesh. For GMAW with metal addition, the FE model is enriched and established in a level set (LS) approach in order to model the evolution of the metal/air interface due to the weld bead development. The FE domain then contains the workpiece and the surrounding air where the weld bead forms. FE computations are coupled with the CA approach used to model the grain structure evolution. A fixed mesh, referred to as CA mesh, is superimposed to the adaptive FE mesh. FE fields are interpolated between the adaptive FE mesh and the fixed CA mesh. A new dynamic allocation/deallocation strategy of a CA grid of cells is then used based on the dynamic activation/deactivation of the elements of the CA mesh. The CA grid is made of a regular lattice of cubic cells superimposed onto the welded domain. At the micro scale, this grid is used in order to simulate the melting and solidification steps at the boundaries between the mushy domain and the liquid pool during the welding process. The temperature evolutions of the cells are computed by interpolation from the CA mesh. Coupling with tabulated transformation paths and phase enthalpy is also implemented, which permits to track the phase amount and latent heat release during the process. In order to master the resolution time and memory cost of the simulations, a management of the FE/CA mesh dimensions and CA cell size is considered for both FE and CA models. The 3D CAFE model is applied to simulate the formation of solidification structures during multiple passes GTAW and GMAW processes on a duplex stainless steel UR 2202. In GTAW, the evolution of the grain structures with respect to the welding process parameters is considered. The normal orientation of the grains with the increase of the heat source velocity is shown. In GMAW, the model is shown to compute the remelting and growth of successively deposited layers. Overall, the predicted structures qualitatively reveal the expected evolutions presented in the literature.
15 citations
Cites background or methods or result from "Welding Metallurgy of"
...Gas Metal Arc Welding ..............................................................................................
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...L type with the shielded electrode of the OK 63-25 type [Moy03], and (b): Gas Tungsten Arc Welding process in 14 mm thick Grade 23 titanium pipe [Smi99] However, when the thickness/width of the weld to be achieved between the two components exceeds the limitation of the single pass technology used, the multiple passes welding processing should be implemented....
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...Note that in all the following simulations it was assumed no nucleation of equiaxed grains in the weld pool, as is sometime observed in the literature [Kou02]....
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...Gas Tungsten Arc Welding Gas Tungsten Arc Welding (GTAW) is a process that melts and joins metals by heating them with an arc established between a non-consumable tungsten electrode and the workpiece [Kou02], as schematically shown in Fig....
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...Gas Metal Arc Welding Gas Metal Arc Welding (GMAW) is a process that melts and joins metals by heating them with an arc established between a consumable electrode and the workpiece [Kou02], as schematically shown in Fig....
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TL;DR: The pulsed gas tungsten arc welding with hot wire was used to clad Inconel 625 on the surface of X65 steel as discussed by the authors, and the influences of welding current in horizontal welding position on the dilution, in furt...
Abstract: The pulsed gas tungsten arc welding with hot wire was used to clad Inconel 625 on the surface of X65 steel. The influences of welding current in horizontal welding position on the dilution, in furt...
15 citations
Cites background from "Welding Metallurgy of"
...So the G/R at the bottom of weld pool was much high, resulting in the formation of planar crystal here.([23,25]) The thickness of planar crystal relates with the heat input....
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TL;DR: In this article, a reverse-engineering approach was used to test a dilatometer-simulated HAZ microstructures and those in a real HAZ weld for welding a V-shaped butt weld.
Abstract: The high-strength steel grade S690QL and a filler welding wire Mn3Ni1CrMo were the materials chosen for welding a V-shaped butt weld. In order to prevent the weld’s cold cracking, a multi-pass welding technique was applied. A metallographic investigation revealed microstructure variations in different areas of the weld’s heat-affected zone. A reverse-engineering approach was used to test a dilatometer’s capabilities to simulate different HAZ microstructures. Hollow steel-cylinder specimens were subjected to several weld thermal cycles in order to generate similar microstructures as in the real weld’s HAZ. The microstructures of the as-welded and simulated heat-affected zone specimens were investigated. Good agreement was found between the dilatometer-simulated HAZ microstructures and those in a real HAZ weld.
15 citations
TL;DR: In this paper, an integrated microstructure evolution model is proposed and applied to the heat-affected zone (HAZ) of an X80 linepipe steel, considering dissolution of Nb-rich precipitates, austenite grain growth and austenites decomposition into ferrite and bainite.
Abstract: An important aspect of the integrity of oil and gas pipelines is the heat-affected zone (HAZ) of girth welds where the microstructure of the as-hot rolled steel is altered with potentially adverse effects on the HAZ properties. Therefore, it is critical to evaluate the HAZ microstructure for different welding scenarios. Here, an integrated microstructure evolution model is proposed and applied to the HAZ of an X80 linepipe steel. The model considers dissolution of Nb-rich precipitates, austenite grain growth and austenite decomposition into ferrite and bainite. Microstructure maps showing the fraction of transformation products as a function of distance from the fusion line are obtained and used to compare the effect of different welding procedures on the HAZ microstructure.
15 citations
References
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TL;DR: In this article, the state of the art in selective laser sintering/melting (SLS/SLM) processing of aluminium powders is reviewed from different perspectives, including powder metallurgy (P/M), pulsed electric current (PECS), and laser welding of aluminium alloys.
1,172 citations
TL;DR: In this article, the authors show that the pre-existing dislocation network, which maintains its configuration during the entire plastic deformation, is an ideal modulator that is able to slow down but not entirely block the dislocation motion.
557 citations
TL;DR: In this article, the fundamental understanding of structure-properties relationship in automotive steels resistance spot welds is discussed. And a brief review of friction stir spot welding, as an alternative to RSW, is also included.
Abstract: Spot welding, particularly resistance spot welding (RSW), is a critical joining process in automotive industry. The development of advanced high strength steels for applications in automotive industry is accompanied with a challenge to better understand the physical and mechanical metallurgy of these materials during RSW. The present paper critically reviews the fundamental understanding of structure–properties relationship in automotive steels resistance spot welds. The focus is on the metallurgical characteristics, hardness–microstructure correlation, interfacial to pullout failure mode transition and mechanical performance of steel resistance spot welds under quasi-static, fatigue and impact loading conditions. A brief review of friction stir spot welding, as an alternative to RSW, is also included.
369 citations
TL;DR: In this article, a unified equation to compute the energy density is proposed to compare works performed with distinct equipment and experimental conditions, covering the major process parameters: power, travel speed, heat source dimension, hatch distance, deposited layer thickness and material grain size.
369 citations
TL;DR: This study attempted to predict solidification defects by DNN regression with a small dataset that contains 487 data points and found that a pre-trained and fine-tuned DNN shows better generalization performance over shallow neural network, support vector machine, and DNN trained by conventional methods.
314 citations