Plate Welding Research Articles

Effect of liquid column on process stability and weld formation under ultra-high power fiber laser-arc hybrid welding of thick plates

Liquid column was a common problem in ultra-high power fiber laser-arc hybrid welding (UHLAHW) process, which has an adverse effect on the welding stability and weld formation. Hence, the influence of welding parameters on the behavior of liquid column was investigated systematically, including laser arc recombination process, laser power, and welding speed. As a result, the violent rising liquid column under laser was suppressed markedly after arc addition. However, it was hard to restrain liquid column upturn when laser power was extremely high, because the huge recoil pressure and shear force between metal vapor/plasma and molten pool could increase the upward momentum of melt. Besides, the height of liquid column and volume of spatters were directly influenced by welding speed, due to the welding line energy could significantly influence the flow of melt on the front of keyhole. By optimizing the welding process, the liquid column could be controlled, thereby significantly improving the welding process stability. Finally, a sound weld bead with qualified weld formation and 15.82-mm penetration was produced when the laser power was 21 kW and welding speed was 1.2 m/min under UHLAHW process. This work provides technical guidance for achieving stable welding process and qualified weld formation for thick plates.

Deformation Evolution Law of Surfacing Welding on Thin Bending Plates Based on the Three-Dimensional Thermal Digital Image Correlation Method

Surfacing on the surface of thin metal bending plates will cause significant deformation, and current numerical simulation and experimental methods cannot fully and truly reflect the deformation state of the bending plate. In this paper, a non-contact detection method based on the three-dimensional (3D) thermal digital image correlation (DIC) method is proposed. The proposed method can be used for the 3D full-field dynamic measurement of metal thin bending plate surfaces. In addition, the evolution law of in-plane and out-of-plane deformation of thin bending plates during surfacing welding and cooling was studied. Moreover, the influence of curvature on the shrinkage deformation of thin bending plate weld was explored, and the correlation between the curvature of thin bending plates and the weld shrinkage was established. Results show that the proposed detection method based on the 3D thermal DIC method can rapidly and accurately detect bending deformation online. The out-of-plane deformation of the surfacing welding of the thin bending plate transits from the disk to the saddle. Furthermore, the curvature of the thin bending plate is inversely proportional to the transverse shrinkage of the weld bead. After the curvature reaches a certain value, it has little effect on the longitudinal shrinkage of the weld bead. This detection method solves the problem of welding deformation simulation verification, truly clarifies the law of welding dynamic deformation, and provides a theoretical basis for welding lightweight manufacturing.

The Influence of Water Flow Characteristics on the Physical and Mechanical Qualities of Underwater Wet Welded A36 Marine Steel Plate

Underwater welding has proven to be a successful method of joining two similar or dissimilar metals and takes place underwater. This technique is frequently used for maintenance purposes, such as repairing piping systems, ships, and other marine structures. This study investigates the effect of different water flow types on an underwater weld’s physical and mechanical properties of welded bead on the A36 steel plate. The SMAW method with an E7018 electrode is used for welding A36 steel in saltwater. In this simulation, underwater welding is performed using three types of flow (without flow, non-uniform flow with a baffle plate, and non-uniform flow without a baffle plate) to compare metallography, hardness, tensile, impact, and bending testing results. The findings revealed that the saltwater flow caused more porosity defects. Moreover, the highest penetration depth was observed in specimens with the non-uniform flow with a baffle plate. The heat energy is concentrated due to droplets accumulating in the weld area. The microstructure of welding metals such as acicular ferrite and ferrite with the second phase grows as the water flow becomes non-uniform. Furthermore, as the rate and variability of the water flow increased, the value of the mechanical properties of the specimens increased relatively.

Microstructure and properties of vacuum electron beam welded WE43 magnesium alloy joint

This study presents the microstructure and properties of vacuum electron beam welded WE43 magnesium alloy joint. The process parameters of acceleration voltage 150 kV, electron beam current 120 mA and welding speed 35 mm/s are used for vacuum electron beam welding of WE43 rare earth magnesium alloy plate. In this study, the main compositions of the weld are α-Mg and a small amount of eutectic rare earth phase β-Mg24Y5. The mass fraction of the rare earth phase β-Mg24Y5 in the weld area is more than that of the base metal. Segregation of Zr-rich particles can occur in weld zone. The average hardness of the weld is about 27% higher than that of the base metal, and the hardness near the center line of the weld is the highest. The yield strength, tensile strength and elongation of the joint are higher than that of the base metal by approximately 17%, 14% and 41%. Tensile fracture morphology of the welded joint is characterized by ductile and brittle mixed fracture. So, electron beam welding can achieve the connection of WE43 magnesium alloy plate with excellent microstructure and performance. It may be of great significance for this study to expand the application of rare earth magnesium alloy.

Study of micro-porosity in electron beam butt welding

As complete elimination of porosity from the weld is very difficult, the next option available is to minimize this weld porosity, which is crucial for the safe performance of the welded components. However, this investigation through experiments alone is very tedious and time consuming. Additionally, very limited models are available in the literature for accurate prediction of different porosity attributes. The present study, thus, addressees both the experimental as well as modelling aspect on the study of micro-porosity during electron beam welding (EBW) of SS304 plates. Welding parameters are reported to have significant influence on the micro-porosity. Hence, the influences of these parameters on micro-porosity attributes, namely pores number, average diameter, and sphericity are extensively studied experimentally employing optical microscopy (OM), scanning electron microscopy (SEM), X-ray computed tomography (XCT), and Raman spectroscopy. This is followed by an elaborate modelling using seven popular and well-recognized machine learning algorithms (MLAs), namely multi-layer perceptron (MLP), support vector regression (SVR), M5P model trees regression, reduced error pruning tree (REPTree), random forest (RF), instance-based k-nearest neighbor algorithm (IBk), and locally weighted learning (LWL). These different techniques enhance the chance of obtaining the better predictions of the said micro-porosity attributes by overcoming the effect of data-dependence and other limitations of individual MLAs. The different model-predicted micro-porosity data are also validated through experimental data. Statistical tests and Monte-Carlo reliability analysis are additionally utilized to evaluate the performances of the employed algorithms. IBk and MLP are overall found to perform well.

Friction Stir Welding of Similar Aluminum Alloys Thick Plates: Understanding the Material Flow, Microstructure Evolution, Defect Formation, and Mechanical Properties

A systematic study of friction stir welding in three Al alloys (2024-T351, 6061-T651, and 7075-T735) has been conducted. The material flow, microstructure evolution, defects and precipitates formation mechanisms, and mechanical properties for different tool rotation and traverse speeds have been systematically investigated for 15 mm-thick butt-welds of similar alloy plates. The nugget zones were determined to be formed by two material flows – shoulder-driven and pin-driven. The shoulder-driven flow corresponds to bulk material transfer (i.e., bulk material flow), while the pin-driven flow occurs through a combination of layer-by-layer material transfer (i.e., layered extrusion flow, due to the pin's extrusion effect) and bulk material flow. The relative volumes of these two flows are dependent on the material and processing parameters. Weld defects are formed when significant flow stress differences between the shoulder-driven and pin-driven flows exist, due to the inhomogeneous heat distribution across the large weld thickness. For materials with higher thermal conductivity, lower flow stresses and temperature gradients, as well as reduced heat inputs result in reduced defect formation. Transmission electron microscopy and differential scanning calorimetry have been used to study the precipitation behavior in friction stir welds. Heterogeneity in the re-precipitation of GP and GPB zones between the top and bottom regions of the nugget zone and coarsening of the base alloys precipitates in the heat affected zone were observed. Optimization of the resulting weld quality and mechanical properties were discussed using the integrated understanding of the material flow and microstructure evolution in friction stir welding of Al thick plates.

Seismic behaviour of anchored prefabricated wall–beam joints of bundled lipped channel-concrete composite wall structures

The existing wall–beam joints of bundled lipped channel-concrete composite wall structures (BLC–CCWSs) are mainly fabricated by welding thin-walled steel tubes and hot-rolled steel plates; however, the application of this technology requires further improvement. In this paper, an innovative anchored prefabricated wall–beam joint was presented. The seismic behaviour of joints was studied by cyclic loading tests of four groups of full-scale specimens, and a hysteretic model of joints was established. The main conclusions are as follows: (1) standard joints fail in the ideal beam plastic hinge damage mode, resulting in a good hysteretic characteristics, energy dissipation capacity, stable bearing capacity and stiffness degradation performance. (2) The anchorage length of the embedment, circumferential weld around end plate and the anchor plate have significant influences on the seismic behaviour of the joints. Sufficient anchorage length and the inclusion of the anchor plate and circumferential weld around end plate can delay the pulling out of the embedment and improve the bearing capacity and the hysteretic performance of a joint before failure. (3) The main contributor to the nonlinear deformation of the joints is the plastic hinge rotation or the rotation caused by sliding of the embedment. (4) The beam end strain can be reduced when the flange is widened. The strain distribution of the embedments is not uniform, and the shear strain in the panel zone is small. (5) The established hysteretic model can take the degradation of stiffness and strength into consideration, and thus produces accurate results that are still conservative and that can be applied in engineering practice.

Ultra-low cycle fatigue fracture initiation life evaluation of thick-walled steel bridge piers with microscopic damage index under bidirectional cyclic loading

Strong earthquakes can cause ultra-low cycle fatigue (ULCF) fracture in steel bridge piers. This paper examined the fracture behavior of two thick-walled square section steel bridge piers subjecting to horizontal bidirectional cyclic loading. In addition, a microscope damage index for evaluating ULCF fracture initiation life of steel bridge piers was proposed. The findings show that ductile cracking firstly appeared at the junction between the stiffened base plate and bottom weld at the corner position of steel bridge piers under bidirectional cyclic loading, and that initial crack growth did not reduce the strength capacity. The strength capacity of steel piers began to rapidly decline as cracks propagated into the base metal. The proposed microscope damage index for ULCF fracture initiation life evaluation of steel bridge piers performs well when compared to experimental and evaluation results.

Estimation of fatigue crack growth rate in different zones of friction stir welded AA7039

The present research aims to study the fatigue crack propagation and fracture toughness behavior of different zones of friction stir welds of AA7039 alloy, as different zones had varying microstructural and mechanical properties. Compact tension specimens with an initial notch in distinct weld zones parallel to the welding direction were machined using welded plates. Friction stir welding altered the base metal grain structure momentously, refined the grain structure in the weld nugget zone, and coarsen the same in the heat-affected zone. No correlation was observed between grain size and weld zone(s) hardness. Weld tensile properties were slightly inferior to base metal despite significantly higher hardness and alternation of grain structure. The fatigue life was dominated by the cycles consumed in crack propagation than crack initiation. The heat-affected zone had higher quasi-static fracture toughness, energy release rate, and resistance toward fatigue crack growth than other zones, because coarse grains and precipitates acted as effective impediments and slowed crack propagation. The heat-affected zone had a mixed-mode fracture, but the weld nugget zone and thermo-mechanically affected zone had an I mode fracture. On fracture surfaces, fracture characteristics such as microvoid coalescence were apparent.

Modelling the hardness of weld metal in the submerged arc welding of low carbon steel plates: addition of CR2O3 nanoparticles

ABSTRACT One of the mechanical properties of weldments influenced by the heat input generated by the Submerged Arc Welding (SAW) process is the Hardness of Weld Metal (HWM). This research was carried out to develop a non-linear regression model using the Response Surface Methodology (RSM) to predict the HWM in the SAW of low-carbon steel plates (St37) in the presence of Cr2O3 nanoparticles. For developing the regression model, current, voltage, stick-out, welding speed, and Cr2O3 nanoparticles were considered as the input variables and the HWM as the response. Analysis of variance was carried out to check the validity of the regression model and decide on the significant variables affecting the HWM. SEM and EDX analysis were performed on the weld to study the microstructure and elemental variables. The main and interactive effects of the input variables on the HWM were presented in graphical forms and analysed. The results showed that increasing the thickness of Cr2O3 nanoparticles increased the HWM due to grain refinement in the weld metal. Furthermore, optimisation of the model was developed for finding the optimum values of the HWM. Finally, confirmation tests were carried out and they indicated that the error of the empirical model was 4.36%.

Effect of Welding Separation Characteristics on the Cyclic Behavior of Steel Plate Shear Walls

Currently, the steel plate shear wall (SPSW) is commonly used in high-rise steel buildings as a lateral load-resisting system due to its several advantages such as its lightweight and high ductility and strength. The SPSW consists of two main parts, i.e., the boundary frame and infill plate, which are connected by welding. The objective of this work is to study the effect of the infill plate weld separation on the seismic behavior of the SPSWs. A numerical method was proposed to have a comprehensive comparison of seismic behaviors of different separation characteristics. The model was validated by using previously published experimental works. Key parameters, such as load-carrying capacity, stiffness, and energy-dissipation capacity, were discussed extensively. The unstiffened SPSW (USPSW) system is more sensitive to the plate–beam separation than the plate–column one, especially the corner plate–beam separation. When plate–column welding separation occurs, the initial stiffness and the energy dissipation capacity are reduced by approximately 21% and 14%, respectively; however, the reductions are 36% and 20.5% in the case of beam welding separation.

Improvements in the Microstructure and Mechanical Properties of Aluminium Alloys Using Ultrasonic-Assisted Laser Welding

Welding high-strength aluminium alloys is generally a delicate operation due to the degradation of mechanical properties in the thermally affected zone (TAZ) and the presence of porosities in the molten metal. Furthermore, aluminium alloys contain compounds that solidify before the rest of the base alloy, therefore acting as stress concentration points that lead to the phenomenon of hot cracking. This paper investigates the process of applying ultrasonic vibrations to the molten pool aluminium alloy AA6082 to improve both its microstructure and mechanical properties. We analysed conventional and ultrasonic-assisted laser welding processes to assess the sonication effect in the ultrasonic band 20–40 kHz. Destructive and nondestructive tests were used to compare ultrasonically processed samples to baseline samples. We achieved a 26% increase in the tensile and weld yield strengths of laser welds in the aluminium plates via the power ultrasonic irradiation of the welds under optimum ultrasonic variable values during welding. It is estimated that the ultrasound intensity in the weld melt, using a maximum power of 160 W from a pair of 28 kHz transducers, was 35.5 W/cm2 as a spatial average and 142 W/cm2 at the antinodes. Cavitation activity was significant and sometimes a main contributor to the achieved improvements in weld quality.

Microstructure and mechanical properties of a welded joint obtained by friction stir welding of thin copper and aluminum plates

Friction stir welding was used to produce a welded joint of 1 mm thick plates of copper M1 and aluminum alloy AMg2M. The microstructure of the shoulder-side of the joint had areas of mixing of aluminum and copper. In the area of aluminum, copper inclusions were observed, and in the area of copper, aluminum inclusions were observed in the form of particles and thin lamellas. The bottom side of the joint consists mainly of copper. X-ray diffraction showed the presence of intermetallic phases Al2Cu, Al4Cu9 from the side of the shoulder. The formation of intermetallic phases occurred in the solid-state, without melting the initial materials. The presence of copper particles in the region of aluminum and aluminum particles and lamellas of various lengths in the regions of copper, intermetallic phases led to the formation of a composite-like structure. The formation of a composite-like structure during friction stir welding of copper and aluminum plates affects the mechanical properties of the joint. Thus, the microhardness of the joint increased in comparison with the microhardness of the initial plates. The distribution of microhardness over the thickness of the joint is almost uniform. The formation of composite-like structure using friction stir welding are discussed.

Fatigue behaviors of aluminum alloy butt joints with backing plates: Experimental testing and traction stress modeling

In this study, the fatigue behaviors and associated failure modes for a series of aluminum alloy butt joints with backing plates are investigated by conducting fatigue testing and Ultrasonic Phased Array Testing (UPAT). When the fatigue properties of butt joints are evaluated according to International Institute of Welding (IIW) and BS7608, the S-N curves of the corresponding welded joints cannot be determined due to irregular positioning of tack welds prepared, following typical manufacturing practices. To gain insights on how the fatigue test data can be correlated with different backing plate positions, traction structural stress method is used for determining both critical fatigue-critical location and corresponding stress value in the test specimens. It is found that the traction stress method is effective in identifying fatigue-critical location caused by backing plate welds and incorporating angular joint misalignment effects.

Considerations Regarding Friction Stir Welding of Stainless Steels

Due to their extraordinary qualities, X5CrNi18-10 (AISI 304L) and X3CrNiMo17-13-3 (AISI 316) stainless steels are among the most used materials in engineering applications with use in priority areas. This also involves finding new solutions for joining this type of metals, effective alternatives to the widely used conventional welding processes.The paper presents the approaches and results obtained at international level for the FSW welding of X5CrNi18-10 and X3CrNiMo17-13-3 stainless steels.The ISIM results are also presented for the FSW butt welding of X5CrNi18-10 stainless steel plates, 4.0 mm and 1.5 mm thick. Data regarding the materials to be welded, the characteristics of the welding tool and the technological process parameters are presented: the rotation speed of the welding tool and the welding speed.When monitoring the welding process, a method was used that is based on an innovative solution based on the use of the infrared thermographic technique, patented by ISIM Timisoara.When welding FSW in inert gas environment FSW-IG, an innovative technical solution for applying the method was used (submitted for patenting), a method that allows monitoring the process in the case of FSW-IG as well. The results of the evaluation process of the welded joints are also presented: referring to metallographic analyzes at macro and microscopic level, micro-hardness, tensile and bending tests.The very good results obtained internationally, but also those obtained at ISIM Timisoara, represent solid arguments that the FSW process can be applied with very good results for welding of X5CrNi18-10 and X3CrNiMo17-13-3 stainless steels.

Improved joint strength between friction-stir welded plates of Al alloy and thermoplastic vulcanizate

Nowadays, metal-polymer composites are used to reduce automobile's weight. However, welding nonpolar polymers to metals is difficult due to the lack of polar groups in molecular chains. The paper put forward an innovative strategy to solve this problem: by adding magnesium methacrylate (MDMA) changes the physical and chemical properties of polypropylene (PP)/ethylene-propylene-diene terpolymer (EPDM) TPV, which improves the compatibility of TPVs and metals. Moreover, the simulation experiments are carried out on plate vulcanization machine. It is found that the addition dosage and order of MDMA have a certain effect on the welding strength. Furthermore, friction stir welding (FSW) replicates the results of simulation experiments, and the ultimate tensile shear strength of P7-E3M1/aluminum alloy (AA6061-T6) reaches 24 MPa. Finally, the welding strength variation regularity with time shows that the properties of metal-TPVs become stable after 10 days. This work introduces a feasible and effective strategy that can be applied to weld various metals to polymers.

A Survey of Process Monitoring Using Computer-Aided Inspection in Laser-Welded Blanks of Light Metals Based on the Digital Twins Concept

The benefits of laser welding include higher production values, deeper penetration, higher welding speeds, adaptability, and higher power density. These characteristics make laser welding a superior process. Many industries are aware of the benefits of switching to lasers. For example, metal-joining is migrating to modern industrial laser technology due to improved yields, design flexibility, and energy efficiency. However, for an industrial process to be optimized for intelligent manufacturing in the era of Industry 4.0, it must be captured online using high-quality data. Laser welding of aluminum alloys presents a daunting challenge, mainly because aluminum is a less reliable material for welding than other commercial metals such as steel, primarily because of its physical properties: high thermal conductivity, high reflectivity, and low viscosity. The welding plates were fixed by a special welding fixture, to validate alignments and improve measurement accuracy, and a Computer-Aided Inspection (CAI) using 3D scanning was adopted. Certain literature has suggested real-time monitoring of intelligent techniques as a solution to the critical problems associated with aluminum laser welding. Real-time monitoring technologies are essential to improving welding efficiency and guaranteeing product quality. This paper critically reviews the research findings and advances for real-time monitoring of laser welding during the last 10 years. In the present work, a specific methodology originating from process monitoring using Computer-Aided Inspection in laser-welded blanks is reviewed as a candidate technology for a digital twin. Moreover, a novel digital model based on CAI and cloud manufacturing is proposed.

Numerical investigation on keyhole stability and weld pool dynamics during quasi-continuous laser beam welding of Ti6Al4V plate using constant and modulated high-frequency pulsed heat input

Numerical investigation on keyhole stability and weld pool dynamics during quasi-continuous laser beam welding of Ti6Al4V plate using constant and modulated high-frequency pulsed heat input

Fatigue strength evaluation of 5059 aluminum alloy welded joints Considering welding deformation and residual stress

With the transformation and upgrading of shipbuilding industry, aluminum alloy shipbuilding will gradually develop towards energy saving, light weight and environmental protection. As a new generation of trustworthy aluminum alloy structure, 5059 aluminum alloy material has better mechanical properties and corrosion resistance. However, two prominent shortcomings of aluminum alloy welding structure are large welding deformation and low fatigue strength. In order to accurately consider the influence of welding defects, the temperature field simulation program of thin plate welding structure is designed to predict the welding deformation and residual stress. The simulation results of temperature field and welding deformation of typical welded joints are in good agreement with the test results. Moreover, taking welding deformation and residual stress as initial conditions, the fatigue strength class curves of 5059 aluminum alloy welded joints are renewed based on the hot spot stress.

Parameter optimization and experimental validation of A-TIG welding of super austenitic stainless steel AISI 904L using response surface methodology

Super austenitic stainless steel (SASS) is a premium stainless steel (SS) variant which finds applications in challenging environments. One of the premium grades of SS that falls under the said category is AISI 904L. Autogenous activated flux tungsten inert gas (A-TIG) welding is an established technique for fabricating sound steel joints which offers various advantages. In this context, this research aims to identify an optimum set of input process parameters to effectively employ A-TIG welding to fabricate 10 mm thick joints of SASS AISI 904L plates by employing bead on plate welding trials. The input parameters varied for the trials are welding current, torch travel speed, and percentage of Argon gas present in a mixture of Argon and Helium – which is the shielding gas used, while the responses were the depth of weld penetration (DOP) and weld bead width (BW). For finalizing the combinations of input parameters and the run order of the welding trials, the design of experiments (DOE) was performed using central composite design (CCD) of response surface methodology (RSM). After performing the trials, the DOP and BW attained were measured and the data thus generated were analyzed to study the influence of varying input parameters on the two responses. Analysis of variance (ANOVA) was then performed to check the input parameter's level of significance. RSM's desirability approach was used for numerical optimization to attain maximum DOP and a moderate BW. A linear regression equation generated can be used to precisely predict DOP and BW for any random values of input parameters. The bead on plate trial's validation study displayed root mean squared error (RMSE) values of 0.328 and 0.653 for DOP and BW respectively, The RMSE values of DOP and BW of the joint fabricated with optimized parameters was 0 and 0.311 respectively.