Welding is widely used by both academia and industry to create similar and dissimilar joints aiming to create a complex shape structure and to couple the mechanical properties of different materials ...into a single monolithic structure. In this book, a collection of peer-reviewed works on the welding of advanced engineering alloys is presented. Both solid-state and fusion-based welding technologies are presented. These works employed advanced microstructure characterization to evaluate how the selection of process parameters impacts the microstructure and mechanical properties of the welded joints. Moreover, three comprehensive review works are also included, providing an in-depth overview of distinct topics. We hope that this collection of works is of interest to the community so that welding technologies continue to grow further in the future.
The mass saving potential of light-weight materials, such as Al alloys, is beneficial for fuel economy and reducing CO
2
emissions. However, the wide-spread use of these alloys has been long hindered ...due to the difficulty in fusion joining as well as their high cost. Welding of Al alloys, which are considered to be difficult to weld through conventional arc welding, is now possible by either of low heat input arc welding, high-power density fusion joining, such as laser beam welding and electron beam welding, or friction stir welding. Particularly, friction stir welding can be successfully applied to these materials owing to the fact that no melting takes place in the weld nugget. The aim of this overview is to summarize the developments in the joining of Al alloys over the recent years. This study is also intended to provide guidance for the industry and researchers dealing with joining of these alloys.
The use of multi-materials structures is nowadays one of the most sought solutions to decrease weight and reduce both emission of greenhouse gases and fuel consumption in the automotive industry. ...Dissimilar joining of aluminum (Al) alloys to steels by fusion-based welding technologies is often difficult to achieve as a result of the significant mismatch in these materials’ physical and chemical properties. Moreover, when mixed in the liquid state, hard and brittle intermetallic compounds are easily formed. Due to characteristics that include high processing speed, flexibility and energy density, multiple attempts have been made to join Al to steel using laser-based processes. This thorough review article provides a comprehensive and exhausting analysis of the recent achievements and progress on joining of Al alloys to steel by various laser-based joining processes, including laser keyhole welding, laser welding-brazing, laser-arc welding, laser-assisted friction stir welding, laser roll pressure welding and joining based on laser additive manufacturing. This paper also evaluates the joining conditions, filler materials, phase constitution, microstructure, mechanical properties and joining mechanisms associated to each process. Furthermore, special emphasis is given to factors affecting the joint strength such as welding defects, joint geometry, intermetallic compounds formation and interfacial strength. The review is then concluded with an outlook providing the summary and future trends of this field.
Nitrogen loss is an important phenomenon in welding of super duplex stainless steels. In this study, a super duplex stainless steel was autogenously TIG-welded with one to four bead-on-plate passes ...with low or high heat inputs using pure argon shielding gas. The goal was to monitor nitrogen content and microstructure for each weld pass. Nitrogen content, measured by wavelength dispersive X-ray spectrometry, was after four passes reduced from 0.28wt% in the base metal to 0.17wt% and 0.10wt% in low and high heat input samples, respectively. Nitrogen loss resulted in a more ferritic structure with larger grains and nitride precipitates. The ferrite grain width markedly increased with increasing number of passes and heat input. Ferrite content increased from 55% in base metal to 75% at low and 79% at high heat inputs after four passes. An increasing amount of nitrides were seen with increasing number of weld passes. An equation was suggested for calculation of the final nitrogen content of the weld metal as functions of initial nitrogen content and arc energy. Acceptable ferrite contents were seen for one or two passes. The recommendation is to use nitrogen in shielding gas and proper filler metals.
Display omitted
•A unique method was employed to produce controlled thermal cycles using robotic welding combined with thermal cycle analysis.•Ferrite content in autogeneous super duplex stainless steel (SDSS) welds were characterized as function of nitrogen content.•An equation was proposed to predict the nitrogen loss in SDSS welds as function of initial nitrogen content and arc energy.
Display omitted
Dissimilar copper/stainless steel metal joints with excellent double-sided forming can be obtained by MIG-TIG double-sided arc welding without grooving and preheating. The joints with ...welding-brazing and fusion welding modes based on the different joining mechanisms in the SS/weld interface can be found. The brazing stainless steel/weld interface shows a flat morphology, while the fusion SS/weld interface consists of a melted unmixed zone (MUZ) and shows a scraggy morphology. A joint free of cracks and pores can be obtained using the welding-brazing mode, which is attributed to the low heat input during welding and the homogeneous composition in the weld zone. Tensile tests show that fracture occurs at the heat-affected zone (HAZ) at the copper side in all joints, and the optimal tensile strength reaches 229 MPa. All joints exhibit lower tensile strength and larger elongation than the Cu base metal due to softening in the HAZ on the copper side. As the amount of the softening mainly depends on the heat input, the welding-brazing joint with low heat input shows high resistance to softening.
•Grey based Taguchi method used for optimization of GMAW parameters with preheating.•Preheat temperature is the most influential parameter contributing 46.25%.•Tensile properties of AISI 1018 MS ...decrease on increasing the preheat temperature.•Joint efficiency at optimized parameters is 94.37%.•Mathematical model has been developed to predict the response parameters.
Welding processes form an integral part of manufacturing industries and construction works. Among all the welding processes available, MIG welding is the widely used welding process due to its versatility and higher productivity. In this research work, AISI 1018 mild steel samples have been welded in V-butt joint configuration using MIG welding. The design of experiment is Taguchi based Orthogonal Array (L9). Effect of process parameters such as current, voltage and preheat temperature has been studied and welds are examined using X-ray radiographic tests. Weld quality has been assessed in terms of tensile properties of weldments such as ultimate tensile strength and percentage elongation. Process parameters have been optimized using grey based Taguchi methodology. Further, analysis of variance has been done to ascertain the influence of input parameters on response parameters. Experimental results show that to achieve optimum ultimate tensile strength and percentage elongation of weldments, preheat temperature turns out to be the most effective input parameter followed by welding current and voltage. A mathematical model has been developed using multiple regression equations. In the end, a confirmatory experiment with optimized parameters from the analysis has also been performed to confirm the results.
BackgroundAn estimated 110 million workers are exposed to welding fumes worldwide. Welding fumes are classified by the International Agency for Research on Cancer as carcinogenic to humans (group 1), ...based on sufficient evidence of lung cancer from epidemiological studies.ObjectiveTo conduct a meta-analysis of case-control and cohort studies on welding or exposure to welding fumes and risk of lung cancer, accounting for confounding by exposure to asbestos and tobacco smoking.MethodsThe literature was searched comprehensively in PubMed, reference lists of relevant publications and additional databases. Overlapping populations were removed. Meta-relative risks (mRRs) were calculated using random effects models. Publication bias was assessed using funnel plot, Eggers’s test and Begg’s test.ResultsForty-five studies met the inclusion criteria (20 case-control, 25 cohort/nested case-control), which reduced to 37 when overlapping study populations were removed. For ‘ever’ compared with ‘never’ being a welder or exposed to welding fumes, mRRs and 95% CIs were 1.29 (1.20 to 1.39; I2=26.4%; 22 studies) for cohort studies, 1.87 (1.53 to 2.29; I2=44.1%; 15 studies) for case-control studies and 1.17 (1.04 to 1.38; I2=41.2%) for 8 case-control studies that adjusted for smoking and asbestos exposure. The mRRs were 1.32 (95% CI 1.20 to 1.45; I2=6.3%; 15 studies) among ‘shipyard welders’, 1.44 (95% CI 1.07 to 1.95; I2=35.8%; 3 studies) for ‘mild steel welders’ and 1.38 (95% CI 0.89 to 2.13; I2=68.1%; 5 studies) among ‘stainless steel welders’. Increased risks persisted regardless of time period, geographic location, study design, occupational setting, exposure assessment method and histological subtype.ConclusionsThese results support the conclusion that exposure to welding fumes increases the risk of lung cancer, regardless of the type of steel welded, the welding method (arc vs gas welding) and independent of exposure to asbestos or tobacco smoking.
Automatic Welding Seam Tracking and Identification Xinde Li; Xianghui Li; Shuzhi Sam Ge ...
IEEE transactions on industrial electronics (1982),
2017-Sept., 2017-9-00, 20170901, Volume:
64, Issue:
9
Journal Article
Peer reviewed
In the automatic welding process on mid/thick plates, the precision of the welding position has an important effect on welding quality, which mainly relies on the identification of the welding seam. ...However, due to some possible disturbances in complex unstructured welding environments, e.g., strong arc lights, welding splashes, thermal-induced deformations, etc., it is a great challenge to identify the welding seam. In this paper, we propose a robust automatic welding seam identification and tracking method by utilizing structured-light vision. First, after the preprocessing of the welding image, the gray distribution of the laser stripe is tracked and the profile of the welding seam is searched in a small area by using the Kalman filter, with the aim to avoid some disturbances. Second, in order to extract the welding seam profile, a series of centroids obtained by scanning the columns in the rectangular window are fitted using the least-squares method. Third, a character string method is proposed to qualitatively describe the welding seam profile, which might consist of different segment and junction relationship elements. And then, these character strings acquired from the object image are matched with those from the model, so that the position of the welding seam can be determined. Finally, the advantages of the new algorithm are testified and compared through several experiments.
Numerous industrial applications, particularly those in the transport industry, require the joining of dissimilar materials which offers considerable benefits in terms of low cost, design ...flexibility, and weight reduction for overall structures. The problems associated with conventional fusion welding processes have stimulated researchers in recent years to develop new joining methods for dissimilar materials which are particularly difficult to join. Friction stir welding (FSW) originally developed for joining difficult-to-weld Al-alloys and FSSW (a variant of FSW for spot welding) have exhibited great potential for obtaining sound joints in various dissimilar alloy systems in different configurations namely butt-, lap- and spot-welding, particularly in dissimilar Al-alloys systems with different properties, which are very difficult to weld using conventional fusion welding techniques. A major difficulty in joining dissimilar Al-alloys by FSW/FSSW lies in the discontinuity in mechanical and technological properties (such as high-temperature strength, plastic deformation capacity, viscosity, etc.) of the materials to be welded across the abutting surfaces. This discontinuity as well as inherent asymmetry in heat generation and material flow of FWS/FSSW processes causes a higher asymmetry in materials flow behavior in dissimilar welding. However, it is relatively easier to implement the FSW/FSSW process to dissimilar Al-alloys in contrast to FSW of dissimilar materials combinations with very differing properties, such as Al-alloy to Mg-alloy or Al-alloy to steel.
