Weld Seam Research Articles

Numerical simulation of efficient welding for thick plates in shipbuilding using simufact welding

In the welding process of medium-thick plates, it is common to create grooves and perform double-sided multi-pass welding. However, this approach leads to low welding efficiency and high costs. Hence, this study utilizes a groove-free, double-sided double-pass welding method to enhance welding efficiency and decrease shipbuilding expenses. A finite element model of groove-free submerged arc welding for medium-thick plates was established using SolidWorks software, and mesh division was carried out. Subsequently, numerical simulations of high-voltage, high-current double-sided double-pass submerged arc welding for medium-thick plates were conducted using Simufact Welding software. In the simulation, a mobile double ellipsoid heat source was utilized to replicate the dynamic alterations throughout the entire welding process. Subsequently, the temperature field of the welded material was computed. Finally, utilizing the temperature field results, the residual stress distribution within the welded material was computed through the thermal-structural coupling feature. The simulation results revealed a significant temperature gradient at the center of the heat source during the welding process, with a slower temperature change observed behind the heat source. Around 4000 seconds, the weldment cooled to room temperature. At this point, the thermal stress mainly concentrated around the weld seam. This numerical welding simulation serves as a crucial reference for designing welding process parameters and researching residual stress distribution. Consequently, it enhances welding efficiency in the field of shipbuilding.

Characterization of microstructures and mechanical properties of laser welded TWIP steel plate

In the present study, laser welding of medium-thick TWIP steel plates was studied and the microstructures and mechanical properties of the welded joints obtained at varied welding speeds were characterized. It is shown that a full penetration was achieved in the welded joint, which exhibits a keyhole-shaped configuration. The welded joint displays a single austenitic phase and typical solidification structure composed of cellular, columnar and dendrite grains. With increasing the welding speed, the grains in both the central fusion zone and adjacent heat-affected zone were refined. The latter was attributed to inadequate recrystallization because of decreased heating time at elevated welding speed. The mechanical properties of all welded joints were lower than those of base metal, in which the decline of elongation was more serious than that of strength. This is attributed to the formation of thick columnar crystals and the Al2O3 core-shell structured nanoscale precipitates in the grains of the fusion zone. Moreover, there existed a certain degree of non-uniformity in the microstructures and mechanical properties along the thickness direction of welding seam, and the samples in the upper area of welding seam showed better comprehensive properties than the lower ones. When welded at a moderate speed as 1.0 m/min, the welding seams exhibited the best mechanical properties and the least difference across the thickness direction of the welding seam. This is because the moderate welding speed resulted in the most beneficial macro- and micro-structures as well as grain boundary characteristics.

Study on metal corrosion behavior of heat-affected zone of oil pipeline

Due to the influence of welding technology, a series of non-uniform and continuous heat-affected zones formed by welding seams is the weakest link of pipeline steel. Compared with the X70 steel, the heat-affected area is in the form of coarse acicular and massive ferrite, granular bainite, and a small amount of pearlite, with weak strength and corrosion resistance. Therefore, this paper simulated the heat-affected zone of the high-strength steel welding seam by the Gleeble 3500 thermal/force simulation testing machine for two heat cycles. Taking Shengli crude oil as the experimental medium, the metal corrosion morphology of heat-affected zones at different temperatures and transmission rates during hot oil transportation was analyzed through immersion experiment and corrosion morphology characterization. The results show that the increase in temperature and flow rate will increase the overall corrosion rate of the metal in the heat-affected area. In the range of 30∼50°C, pitting corrosion was the main corrosion feature of the metal, and in the range of 50∼70°C, the corrosion morphology of the metal changed from pitting corrosion characteristics to comprehensive corrosion characteristics. In the range of the flow rate studied (1∼4 m/s), the metal in the heat-affected area was mainly the overall corrosion rate, and the metal surface showed the erosion-corrosion characteristics along the flow rate direction.

Cyber‐physical‐based welding systems: Components and implementation strategies

AbstractThe conditions for a feasible Cyber‐Physical System (CPS) in a welding environment are explored for the manufacturing technology components while also focusing on machine learning tools. Increasing manufacturing efficiency means making digitalisation feasible for all technologies, including welding, given today's challenges. Early versions of manufacturing management, such as Computer Integrated Manufacturing, are already leading the way, and one of the latest milestones in these developments is CPS. It can be shown that the digital migration of specific sub‐domains (e.g. visual inspection of the weld seam during quality assurance) is significantly more challenging and unimaginable without artificial intelligence applications. However, it is also true that the full integration needed to achieve autonomous manufacturing has yet to be fully achieved, although there is a strong demand in the industry for these CPS to work. In some areas, the digital switchover has already been prepared. However, the interconnection of these subsystems requires modern information systems or, in the case of existing ones, their upgrading to the appropriate level. This research area is set to be addressed comprehensively by initiating several projects. In the initial phase, the aim is to develop an architecture that integrates the various Information Technology applications. In this work, the digital manufacturing environment under CPS is studied, the relevant components are explored, the conditions for the transition from traditional to CPS‐based manufacturing are examined and examples of planned further specific studies on the components are listed.

The feasibility of resistance seam welding as an additive manufacturing technology for Al 1060

Resistance seam welding additive manufacturing (RSAM) is a new solid-state additive manufacturing technique that utilizes pulsed current and pressure to welding powders layer by layer. In this study, Al1060 powder was employed as the raw material to prepare R0 and R10 samples through RSAM technology and subsequent repeated welding processes, respectively. The results showed that, compared to R0, the grain size of the R10 sample decreased from 34.3 μm to 8.7 μm, and the dislocation density increased from 4.355 × 1014 to 9.436 × 1014 m−2. Additionally, due to the additional heat and pressure from repeated welding, the porosity decreased from 0.998% to 0.017%, the ultimate tensile strength and elongation improved from 63.5 ± 0.5 MPa and 4.5 ± 0.1% in R0 to 93.3 ± 0.5 MPa and 34.3 ± 0.1% in R10. The improvement in mechanical properties is primarily due to the combined effects of grain refinement, dislocation strengthening, and pore self-healing. This study introduces a feasible new approach for additive manufacturing of aluminum alloys and other materials that is difficult to be additively manufactured by other methods.

A novel model-based welding trajectory planning method for identical structural workpieces

Welding robots have been widely used with the development of manufacturing industry. At present, welding trajectory planning and programming of welding robots are performed separately for similar (structural) workpieces with different dimensions or deformations. Besides, the welding torch pose planning using conventional robot programming methods is time-consuming for workpieces with complex welding trajectories. To realize automatic planning of the welding torch pose for similar workpieces and improve the programming efficiency of welding robots, we propose a novel model-based welding trajectory planning method for welding robots. We create a basic model (point set) containing information on welding seam trajectory planning for similar workpieces. The welding seam trajectory extraction of similar workpieces is achieved by the non-rigid point set registration of the feature point cloud of similar workpieces with the basic model. Then, the welding torch pose planning is implemented by the geometric projection method of the local point cloud of the welding seam trajectory. Finally, the results of offline experiments and online experiments demonstrate the effectiveness of the proposed method.

Quenching of Disk-Shaped Components in Aqueous Polymer Solutions

Abstract In addition to various advantages over oil quenching, quenching in aqueous polymer solutions can also have disadvantages. Under certain conditions, “explosive” phenomena can occur when quenching steel components in such solutions, leading to pressure waves and vibrations in the quenching tank, which can even destroy the weld seams of the tank in the long term. After these processes were analyzed in the past when quenching cylindrical shafts, the processes occurring with horizontally charged disks have now been investigated. The main difference between these two geometries lies in the size of the lower disk end face, which significantly impedes the outflow of evaporated portions of the aqueous polymer solutions and thus has a pronounced influence on the cooling behavior of disk-shaped components. The investigations to be presented here were carried out in a laboratory quenching tank. The type and concentration of the polymer, the flow type and the diameter of the inner bore of the disks were varied. Temperature and conductivity were measured and audio and video recordings were made to characterize the resulting cooling processes. Selected quenching variants are presented in detail in the article. Furthermore, key figures for characterizing the various cooling variants are compared and discussed.

Microstructure and mechanical assessment of Inconel 625 and AISI 904L dissimilar joints using high-density welding technique for pressure vessels

The dissimilar bimetallic joints of 5 mm thick Inconel 625 and AISI 904L were accomplished through the high-density fiber laser welding (LBW) process. The metallurgical investigation ensured the micro-segregation of Mo and Nb in the dendritic and inter-dendritic regions along with the formation of secondary topologically closed packed (TCP) phases. In addition to the metallurgical studies the Kernal average misorientation (KAM), Schmid factor (SF), and nucleation of the new grains were investigated through Electron backscattered diffraction (EBSD) analysis. The tensile strength opined the occurrence of failure on the 904L side, away from the weld seam ensuring that the joints have a higher strength. The notch tensile showed a higher strength of 678 ± 4 MPa in the weld zone than that of the 904L base alloy. The Charpy V notch studies showed a drastic decrease in the impact toughness with 38 ± 2 J as compared to the base alloys under sudden impact loading at room temperature (RT).

Porosity suppression of nickel-based superalloy by modulated base temperature in laser welding and mechanism analysis

This paper investigates the distribution pattern of welding porosity defects in annular weld seams of superalloy during laser welding. The results reveal that the initial portion of the annular weld seam exhibits a higher density and larger size of porosity defects compared to the ending portion. At a laser power of P = 360 W, the numerical simulation combination showed that the A1 region's average cooling rate is 8.767 × 103 °C/s and the A2 region is 8.151 × 103 °C/s that the thermal conduction effect at the initial welding position leads to an elevation in the base metal temperature in the subsequent unwelded region, thereby reducing the solidification rate of the molten pool in the latter half of the weld seam and effectively decreasing the porosity rate at the weld seam. Furthermore, the study demonstrates that elevating the base metal temperature can effectively modify the cooling rate of the molten pool, thereby influencing the formation of porosity defects. At a laser power of P = 360 W, increasing the base metal temperature to 600 °C reduces the cooling rate of the molten pool from 8.767 × 103 °C/s at a base metal temperature of T = 20 °C to 7.451 × 103 °C/s, leading to a decrease in the porosity rate from 3.357% to 0.022%. At a laser power of P = 672 W, increasing the base metal temperature to 600 °C reduces the cooling rate of the molten pool from 6.781 × 103 °C/s at a base metal temperature of T = 20 °C to 5.056 × 103 °C/s, leading to a decrease in the porosity rate from 8.214% to 0.002%. The increase in laser power brings more heat input, so the solidification rate of the molten pool decreases, but the porosity increases significantly. However, increasing the base temperature can effectively suppress the porosity defects under different laser powers. The research further reveals the relationship between welding porosity rate and cooling conditions, providing a control strategy for achieving low porosity rate welds.

Effect of Welding Gap of Thin Plate Butt Welds on Inherent Strain and Welding Deformation of a Large Complex Box Structure.

In this study, an effective numerical model was developed for the calculation of the deformation of laser-welded 3 mm 304L stainless steel plates with different gaps (0.2 mm, 0.5 mm, and 1.0 mm). The welding deformation would become larger when the welding gaps increased, and the largest deformation values along the Z direction, of 4 mm, were produced when the gap value was 1.0 mm. A larger plastic strain region was generated in the location near the weld seam, since higher plastic deformation had occurred. In addition, the tensile stress model was also applied at the plastic strain zone and demonstrated that a larger welding gap led to a wider residual stress area. Based on the above results, inherent deformations for butt and corner joints were calculated according to inherent strain theory, and the welding formation for the complex structure was calculated with different gaps. The numerical results demonstrated that a larger deformation was also produced with a larger welding gap and that it could reach the highest value of 10.1 mm. This proves that a smaller welding gap should be adopted during the laser welding of complex structures to avoid excessive welding deformation.

Research on welding seam tracking algorithm for automatic welding process of X-shaped tip of concrete piles using laser distance sensor

AbstractThe manufacturing of the X-shaped tip of prestressed centrifugal concrete piles is nowadays done half automatically by combining the manual worker and the automatic welding robot. To make this welding process full automatically, the welding seam tracking algorithm is considered. There are many types of sensors that can be used to detect the welding seam such as vision sensor, laser vision sensor, arc sensor, or touch sensor. Each type of sensor has its advantages and disadvantages. In this paper, an algorithm for welding seam tracking using laser distance sensor is proposed. Firstly, the fundamental mathematics theory of the algorithm is presented. Next, the positioning table system supports the procedure is designed and manufactured. The object of this research is the fillet joint because of the characteristics of the X-shaped tip of the concrete piles. This paper proposes a new method to determine the welding trajectory of the tip using laser distance sensor. After that, the experimental results are received to verify the proposed idea. Finally, the improved proposal of the algorithm is considered to increase the accuracy of the suggested algorithm.

Enhanced strength and ductility of aluminum alloy laser welded joints through Ca micro˗alloyed welding materials

Aluminum alloy is widely used in high˗speed train bodies. However, compared with the base material, the tensile strength and elongation of its laser welded joints are significantly reduced, which limits the lightweight application of the next generation of high˗speed trains. The research in this article indicates that laser welding with Ca micro˗alloyed 5356 filler metal has changed the mechanical properties and microstructure of the weld seam. Without the Ca in the filler metal, the strength and elongation of the laser welded joint are only 215.5 MPa and 3.1 %. When the Ca content in the filler metal reaches 0.04 wt%, the laser welded joint has high tensile strength and maximum elongation, which are 251.5 MPa and 9.7 %, respectively. As the Ca content increases, the grain size of the welded joint gradually decreases, and the limiting effect of Ca element on the growth of α˗Al grains is the main reason for grain refinement. In addition, the addition of Ca transforms the coarse Fe˗rich phase in the weld into a fine˗grained second phase, while promoting the formation of deformable nanoparticles γ˗Al12Mg17, leading to the accumulation of dislocations and successfully improving the strength and plasticity of laser welded joints. When the Ca content further increases, the second phase grows, and the tensile strength and plasticity of the joint slightly decrease, but are still higher than that of the joint without Ca.

Дослідження технології зварювання плавленням складнолегованих титанових сплавів

The subject of this article is peculiarities of weld seam formation of complex titanium alloys during electron beam welding in vacuum and argon arc welding. The purpose of this study is to ensure the required level of mechanical properties of welded structures from complex titanium alloys to improve the structure and properties of welded joints. The task: to investigate the processes that are taking place in the zone of thermal influence and to determine their influence on defects formation; to determine the modes of parts welding made of complex titanium alloy; to study the effect of electron beam welding on the materials properties, such as strength, crack resistance, and corrosion resistance. Research results. The thermal cycle influence of welding and subsequent heat treatment on the structural and phase transformations in the weld metal and the heat-affected zone of complex titanium alloy welded joints was studied. It was established that a structure with a metastable β-phase predominance is formed in the weld metal and the zone of welded joints thermal influence, which contributes to the reduction of plasticity and impact toughness. The best combination of the studied welded joint strength and ductility was obtained after heat treatment, annealing at a temperature of 950 °C for 1 h, and cooling in the furnace. The use of filler wire contributes to obtaining an almost uniform structure and the disintegration of metastable phases in the seam as well as in the zone of thermal influence, and the strength limit is 1250 MPa. Conclusions. The influence of filler wires on the obtained samples structure and properties was studied, and the results were discussed depending on possible practical implementations. This article describes the creation and testing of elements of electron beam welding of complex titanium alloys technological process. This makes it possible to widely use welded combined titanium alloys in products of the appropriate purpose. The obtained scientific and practical results lead to increased mechanical properties of complex titanium alloys welded joints to the level of the base metal.

S30408 stainless steel laser weld joints: Microstructure evolution, performance and surface reinforced composites

The reinforced corrosion resistance composite coating was fabricated by laser cladding (LC) on the laser weld seam (WS) of S30408. The uniform microstructure, good tensile strength of WS and the LC coating were investigated, the mechanism of this LC coating reinforced the corrosion resistance of WS was extensively researched. The results revealed that WS consisted of face-centered cubic (fcc) austenite, and body-centered cubic (bcc) ferrite. The LC coating consisted of fcc. Amounts of the granular precipitates were distributed near the ferrites in WS. The tensile strength of WS was increased due to the synergistic effect of the solution/fine grain strengthening. Corrosion resistance of the LC coating was higher than that of the weld seam. Passivation films were produced due to the chemical reaction between Co/Cr/Fe and water/oxygen.

Improved Joint Formation and Ductility during Electron-Beam Welding of Ti6Al4V and Al6082-T6 Dissimilar Alloys

The current work is based on investigating the influence of different technological conditions of electron-beam welding on the microstructure and mechanical properties of joints between Ti6Al4V and Al6082-T6 dissimilar alloys. The plates were in all cases preheated to 300 °C. Different strategies of welding were investigated such as varying the electron-beam current/welding speed ratio (Ib/vw) and applying a beam offset towards the aluminum side. The heat input during the experiments was varied in order to guarantee full penetration of the electron beam. The macrostructure of the samples was studied, and the results indicated that using a high beam power and a high welding speed leads to an increased formation of defects within the structure of the weld seam. Utilizing a lower beam current along with a lower welding speed leads to the stabilization of the electron-beam welding process and thus to the formation of an even weld seam with next to no defects and high ductility. Using this approach gave the highest ultimate tensile strength (UTS) of 165 MPa along with a yield strength (YS) of 80 MPa and an elongation (ε) figure of 18.4%. During the investigation, improved technological conditions of electron-beam welding of Ti6Al4V and Al6082-T6 dissimilar alloys were obtained, and the results were discussed regarding possible practical applications of the suggested approach along with its scientific contribution to developing further strategies for electron-beam welding of other dissimilar alloys. The downsides and the economic effect of the presented method for welding Ti6Al4V and Al6082-T6 were also discussed.

Enhanced mechanical properties of thermo-mechanically affected zone of friction-stir welded AZ61 magnesium alloy joint

Friction-stir welded (FSW) magnesium alloy joints frequently fracture at thermo-mechanically affected zone (TMAZ), and the joints exhibit unsatisfactory welding efficiency and ductility. The TMAZ is considered as the weakest region of the entire joint. Enhance the mechanical properties of TMAZ can improve the performance of the welded joint. In this work, subsequent aging treatment and pre-strain of 3% along the weld seam were conducted on the FSW AZ61 magnesium alloy joint. The microstructure of the TMAZ is characterized by abundant nanoscale second phase particles and {10–12} twins. The reduced basal texture intensity decreased the anisotropy of plastic deformation. The welded joint showed a good synergic of welding efficiency (96%) and ductility (20%). The enhanced strength is attributed to the blocking effect of nanoscale particles and grain/twin boundaries to dislocation movement. The increasing of twin boundaries is the main reason for the improvement of work hardening ability and ductility during tensile deformation. This work demonstrated that introducing {10–12} twins and nanoscale particles into TMAZ is an effective way to improve the balance of strength and ductility of the welded joint due to the synergistic effect of multiple strengthening and toughening mechanisms.

Laser Weld Seam Curved Path Effect on 6063 Aluminum Alloy Strength and Temperature Distributions: COMSOL Numerical Simulation

To improve the welding performance of aluminum alloys, a thermal source model of an irregular weld seam was established. COMSOL software was used for numerical simulation of the weld seam geometry effect on the temperature and stress fields in laser welding, which results were experimentally validated. The results show that the ellipsoidal laser welding melted micropool exhibited quasi-steady-state temperature field characteristics. The temperature gradient and thermal stress showed an increase followed by a decline. The temperature fluctuation amplitude of the square-tooth-shaped weld seam exceeded that of the arc-toothshaped one. The temperature evolution of the broken line tooth-shaped weld seam showed a slightly increasing trend, except for the inflection point. The experimental average tensile strength of the weld seam was the highest, reaching about 210 MPa, i.e., roughly 85% of the base material (245 MPa), which coincided with the COMSOL-based temperature field simulation results. With increasing deformation amplitude and transition radius, the maximum tensile force, tensile strength, and elongation at fracture showed an increasing trend. However, the deformation amplitude should be below a certain limit because its increase elongates the welding path and reduces the distance between weld seams, resulting in serious heat accumulation. The tensile fracture morphology of the 6063-T6 base material was curved shear, with shallow toughness pits, small tearing edges at the edges, and small granular objects, indicating small plastic deformation during the fracture process. The tensile fracture of the welded part spanned the weld seam and the base material, and the fracture occurred along the tangent direction of the weld seam. The fracture surface was smooth, the tearing edges at the edge of the toughness pit shifted along the weld seam direction, forming many co-directional slip bands, with highly pronounced plastic deformation.

Development of a vision system integrated with industrial robots for online weld seam tracking

This paper develops a laser-structured light vision system for the industrial welding manipulator. The designed structured light vision system consisting of a line laser projector and an industrial camera is a decent 3D object data acquisition platform. By applying the principle of triangulation, the depth value of the object can be obtained via the laser plane in the captured image. According to hand-eye calibration and the principle of triangulation, the 3D position of the objects in the robot coordinate system is calculated. Based on the discriminated convolution tracker and deep reinforcement learning that increases the accuracy and processing time of the tracker, allowing simultaneous scanning for seam data acquisition and welding along the weld path, a real-time seam tracking algorithm is developed to handle the square-groove butt joint with small gaps (i.e., <1 mm). Experiments are undertaken using a Yaskawa industrial welding robot integrating the designed laser-structured light vision system. Experiment results show the significant performance of the developed system in welding square-groove butt joints with curved profiles and small gaps, i.e., the welding absolute mean error is 0.31 mm, whereas in the case of using convolution tracker only, the welding absolute mean error 1.7 mm.

Influence of Friction Stir Weld Seam Distribution on Spun Formed Workpieces

Influence of Friction Stir Weld Seam Distribution on Spun Formed Workpieces

Controlling the weld penetration depth of laser beam micro welding by using an iterative learning approach

AbstractIn order to meet the increasing demand for high‐speed joining processes, laser beam micro welding is used to reproducibly weld metallic joining partners such as steel. Long weld seams or high cycle speeds, however, remain a challenge to achieve a constant welding depth throughout the entire welding process without major fluctuations. This paper shows the development and evaluation of a weld penetration depth control system based on interferometric measurement of the depth of the vapor capillary. High path speeds and small weld depths are challenging for real‐time depth control. Therefore, the offline data of the interferometric measurements are used to implement an iterative learning control of the weld penetration depth. The quality of the control is verified by welding with and without spatial power modulation on 1.4301 steel while following a linear and sinusoidal trajectory.