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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.
Citations
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Journal ArticleDOI
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


Cites background from "Welding Metallurgy of"

  • ...(......................................................3/)(16 33* VSL GSG ∆=∆ θπγ According to Kou [144] and Savage [145], growth of the solid in fusion welding is perceived as being initiated by epitaxial growth from the substrate and proceeds by competitive growth toward the center line of the weld....

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  • ...100 the predominant mechanism of solidification in fusion welding is the competitive growth in the weld fusion zone, Kou [144] identified and discussed the details of other mechanisms such as dendrite fragmentation, grain detachment, heterogeneous nucleation and surface nucl eatio that may tend can interrupt and/or dominate the solidification structure in fusion welding....

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  • ...According to Kou [144] and Savage [145], growth of the solid in fusion welding is...

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  • ...Whereas, the predominant mechanism of solidification in fusion welding is the competitive growth in the weld fusion zone, Kou [144] identified and discussed the details of other mechanisms such as dendrite fragmentation, grain detachment, heterogeneous nucleation and surface nucleatio that may tend can interrupt and/or dominate the solidification structure in fusion welding....

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Journal ArticleDOI
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

Journal ArticleDOI
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


Cites background from "Welding Metallurgy of"

  • ...Despite the fact that Schaeffler diagram predicts two phases (austenite plus ferrite) in the FZ of AISI 304 weld nugget microstructure, under rapid solidification conditions such as laser beam welding, a shift in solidification mode may occur.(90) It is generally believed that the change in solidification mode can often result in a fully austenitic microstructure compared to the two phase (ferrite plus austenite) microstructure that is commonly found after primary ferrite solidification....

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  • ...In coarse grained region, which is beside the FZ, both high cooling rate and large austenite grain size coupled with the formation of the carbon rich austenite promote the formation of the martensite.(90) Figure 15 shows the microstructure gradient in TRIP780 RSW....

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  • ...The HAZ in carbon steel weldments can be divided into three distinct subregions: (i) upper critical HAZ (UCHAZ): This region experiences peak temperatures above Ac3 transforming BM microstructure into austenite.(90) Depending on the peak temperature the supercritical HAZ can be divided to the following zones: coarse grained HAZ (CGHAZ) and fine grained HAZ....

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  • ...It is generally believed that the change in solidification mode can often result in a fully austenitic microstructure compared to the two phase (ferrite plus austenite) microstructure that is commonly found after primary ferrite solidification.(90,95,96) Although the change in solidification mode of stainless steel in RSW has not been studied yet, very high cooling rate in RSW process can explain the formation of a fully austenitic weld nugget, as it is the case for laser beam welding....

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  • ...If this temperature is above Mf, there can be untransformed austenite left in the FZ and it can redecompose to untempered martensite upon cooling to room temperature after tempering.(90) For a particular tempering time and tempering current, there is a minimum cooling time to achieve PF mode....

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Journal ArticleDOI
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

Journal ArticleDOI
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


Cites background from "Welding Metallurgy of"

  • ...Solidification crack is one of the most serious defects which occurs widely in welding [27,28], casting [29–31] and additive manufacturing (AM) [32,33], which occurs at the last stage of solidification when liquid films exist between dendrites boundaries where local strains cannot be accommodated by liquid feeding and solid deformation....

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References
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10 Mar 2015
TL;DR: In this paper, the difference welding between Inconel 625 nickel base super alloy and high strength quenched and tempered 517 Gr.B steel was investigated by pulsed ND:YAG laser beam welding equipment.
Abstract: Original Research Paper Received 30 April 2014 Accepted 22 June 2014 Available Online 26 October 2014 Dissimilar welding between Inconel 625 nickel base super alloy and high strength quenched and tempered 517 Gr.B steel was investigated by pulsed ND:YAG laser beam welding equipment. This joint has special application in submarine components. After welding, the optimized joint microstructure including the weld metal and heat affected zones were characterized by optical and scanning electron microscopy (SEM). The results showed fine dendritic structure and existence of large amount of Niobium carbide and Laves eutectic phase in the weld metal. Energydispersive X-ray spectroscopy (EDS) analysis showed Nb and Mo segregation to interdendritic zones at the weld metal. Grain growth in the heat affected zone of Inconel 625 did not occur, however, ultrafine precipitations were deposited at the heat affected zone. An approximately 65 μm wide transition zone was observed at the steel and weld zone interface; consisting of martensitic layer (10-20μm) along the weld interface and the austenite phase region with small amount of ferrite adjacent to the base metal. The tensile test and micro hardness test of the optimized sample was investigated. The electrochemical behavior of the weld metal was investigated at room temperature in 3.5% NaCl solution using potentiodynamic polarization. The results show that the corrosion resistance of weld metal is more than that of Inconel 625 and less than that of 517A Gr.B. It can be concluded that a proper selection of laser beam welding parameters provides sound, fully-penetrated welds.

3 citations

Journal ArticleDOI
TL;DR: In this paper, a method is developed for determining the optimal concentration of nanostructured powder in the protective gas in welding by a floating electrode in argon, which is confirmed by experiments with molybdenum nanopowder, introduced in the welding bath through a special device.
Abstract: In the present work, a method is developed for determining the optimal concentration of nanostructured powder in the protective gas in welding by a floating electrode in argon. The theoretical analysis is confirmed by experiments with molybdenum nanopowder, which is introduced in the welding bath through a special device. The apparatus used for surfacing of the sample includes a GSP-2 welding head combined with the specially developed device and a VS-300B power source. In surfacing 12Kh18N10T steel samples, 12Kh18N19T steel welding wire (diameter 1.2 mm) is employed. To ensure a satisfactory weld joint, the dendrite dimensions must be minimized. Stable welding is ensured by transfer of a droplet of electrode metal from the end of the welding wire to the welding bath. Hence, the droplet volume must also be minimized. Before optimizing the concentration of nanostructured powder in the protective gas, the influence of the welding parameters on the microstructure of the surfaced metal is established. The results show that the grain size is smallest with a current of 240–260 A and an arc voltage of 28–30 V. In those conditions, the optimal concentration of nanostructured powder in the protective gas is determined. It is found that the optimal concentration is 20 mg per 1 m of weld seam. The use of different concentrations of nanostructured powder in the protective gas results in different microstructure of the applied metal. When the concentration of nanostructured powder in the protective gas is 20 mg per 1 m of weld seam, the branching of the dendrites is least and the dendrite size corresponds to equilibrium structure. On adding nanostructured powder to the liquid bath, the mechanical properties of the weld joints are increased by 7.5% at +20°C and by 6.5% at +500°C.

3 citations

Journal ArticleDOI
TL;DR: In this paper, the relation between the classical basicity index and several optical basicity indices using criteria according to Zhang (BOzh), Duffy and Ingram (BOD) and also between the BOP and the molar ratio O: (Si + Al) in each matrix.
Abstract: The structural constitution and ionic or molecular nature of the glassy matrix in liquid aluminosilicates are governed mainly by the molar ratio O: (Si + Al), and during the welding process affect its thermodynamic, chemical and physical properties as well as in their interactions with the metal droplet and the weld pool. In aluminosilicate fusion, O2-ion interactions with other substances from the unalloyed flux matrix and filler metals and base are of considerable importance during the formation of the weld metal by submerged arc welding process (SAW). In this study, assessing the relation between the classical basicity index and several optical basicity indices using criteria according to Zhang (BOzh), Duffy and Ingram (BOD) and the proposed in this work by the authors (BOP) and also between the BOP and the molar ratio O: (Si + Al) in each matrix. This provides structural-chemical criteria for the matrices and their metallurgical activity. From a thermodynamic analysis one can determine the oxygen amount in the weld metal, which allow to estimate the possible physical and mechanical properties of itself.

3 citations

Journal ArticleDOI
TL;DR: In this paper, a transient thermo-mechanical model is employed to study the effects of welding parameters on the occurrence of solidification cracking, and it was found that the increasing of welding current from 70 A to 100 A resulted in an increase in transverse tensile strain from 1.2 to 2.1 which can facilitate the formation of solidified joints.
Abstract: A transient thermo-mechanical model is employed to study the effects of welding parameters on the occurrence of solidification cracking. A finite element program, ANSYS, is employed to solve the thermal and mechanical equations while the different variables such as welding current, speed and sequence are considered in the simulation. The studied geometry was butt joint of two stainless steel plates with the thickness of 2 mm. Then, the samples were welded by TIG method without filler. To verify the numerical results, the model outputs were checked with the experimental observations and good agreement was observed. It was found that the increasing of welding current from 70 A to 100 A resulted in the increase in transverse tensile strain from 1.2 to 2.1 which can facilitate the occurrence of solidification cracking. Furthermore, the application of symmetric welding layout is an effective method to prevent solidification cracking.

3 citations

01 Jul 2011
TL;DR: In this paper, the effect of submerged arc welding parameters on grain development and weld metals chemistry (oxygen and nitrogen) on SA516 and A709 steel weld metals was done. And a cooling rate parameter based on the ratio of the weld nugget cross sectional area and the fusion zone interface length (CI) was used in this evaluation.
Abstract: In this study, the effect of submerged arc welding parameters on grain development and weld metals chemistry (oxygen and nitrogen) on SA516 and A709 steel weld metals was done. The influence of oxygen and nitrogen concentration introduced into the weld metal during welding on grain development and nucleation of acicular ferrite was evaluated. The weld oxygen and nitrogen compositions were measured using LECO combustion analysis method. Optical microscopy (OM), and scanning electron microscopy (SEM) attached with energy dispersive spectrometers (EDS) were used to characterize the microstructure of the weld metals. A cooling rate parameter based on the ratio of the weld nugget cross sectional area (NA) and the fusion zone interface length (CI) was used in this evaluation.

3 citations