Plate Welding Research Articles

Numerical modelling of high-power laser spot melting of thin stainless steel

Numerical modelling is an important scientific tool in laser materials processing to study different melting, evaporation, and solidification phenomena. It can assist in understanding why certain defects are formed, and thus may provide solution paths for how to decrease certain defects and to increase the quality of a product. Laser spot melting in heat conduction mode represents a simple case and is an excellent first step to build and test solvers prior to moving on to more complicated cases such as laser keyhole welding of thick plates. Modelling of laser spot melting requires only a limited computational domain and allows more complex physics to be added gradually. In this work, a thin 3.0 mm thick stainless steel plate was melted with high-power fiber laser and numerically simulated using a native and custom-build solver based on the VOF method within OpenFOAM. The process was captured with a high-speed imaging camera and simulation results are compared with the experimental results. It was found that temperature-dependent surface tension plays a vital role in controlling melt flow directions within melt pool.

Inhomogeneous microstructure distribution and its formation mechanism in deep penetration laser welding of medium-thick aluminum-lithium alloy plates

Inhomogeneous microstructure distribution and its formation mechanism in deep penetration laser welding of medium-thick aluminum-lithium alloy plates

An innovative coil for magnetic pulse welding of dissimilar sheet metals: Numerical simulation and experiments

Magnetic pulse welding (MPW), as an environmentally friendly room temperature solid-state welding technology, usually involves low energy utilization efficiency, resulting in the need for higher energy to achieve metallurgical welding. This study proposed an innovative coil structure for increasing energy utilization efficiency during MPW. The current signal and structural strength of new coils with different turns were analyzed by numerical simulation. The results show that, different from traditional E-shaped and H-shaped single turn coils, the new structure can achieve nearly n-time amplification of current, which enabling the flyer plate to achieve the critical speed of metallurgical welding at lower energy. The 7-turn coil has higher structural strength and pulse current compared to the other coils in this study. The initial current was amplified 5.2 times by the 7-turn coil and welding of Al-Fe plates was achieved. The microstructures at the welding interface exhibit typical metallurgical features, including wave interfaces, element diffusion layers, and intermetallic compounds. The fracture location of the AA1060 (thickness δ: 0.5)-DP600 joint appeared on the base metal. The fracture morphology of AA5754 (thickness δ: 1.0)-DP600 joint shows that a large amount of aluminum element remains on the DP600 plate. Therefore, the new coil can increase the energy utilization rate during the welding process and achieve stable metallurgical welding of dissimilar materials.

Modeling the matching stage of HDPE hot plate welding: A study using regression and support vector machine models

AbstractThis research studies the material displacement of high‐density polyethylene (HDPE) during the initial stage of the hot plate welding (HPW) process, called the Matching stage. Newly developed mathematical models simulate the relationship between the main process parameters (force, temperature, and time) and the size of the surface area. The collected data was used to develop four mathematical models for material displacement and time. Two models are machine learning based models (support vector machines). The other two models are regression models in the form of functions. In addition, this study provides a visual representation of HDPE melt displacement with the changes in temperature and pressure. The obtained results indicate that these models can be used for developing a parameter adjustment process or determining specifications for new production equipment. The potential applications of the developed models can be extended to industries that use HPW of HDPE, such as automotive or aerospace. This could result in significant savings in the amount of scrap and waste due to inaccurate and ad hoc settings that currently take place in the industry.Highlights Study of HDPE material displacement in the hot plate welding Matching stage. Visualization of HDPE melt displacement with temperature and pressure changes. Development of SVM and mathematical regression models. Applications in parameter adjustment and equipment specification. Savings in scrap and waste by reducing inaccurate settings.

Frontal pyrometric snapshot measurements of the keyhole wall temperature in laser welding of pure aluminium

In deep penetration laser welding, the quality of the weld seam is strongly correlated with the process dynamics. Pronounced dynamics of the melt pool and the keyhole cause defects like pores and blow-outs which negatively affect the mechanical properties of the seam. The process dynamics are primarily governed by the fluctuations of the keyhole shape. Therefore, in order to avoid the occurrence of defects in the weld seam, it is necessary to gain control over the keyhole stability by understanding the underlying physical processes that contribute to its dynamics. Besides the intensity distribution of the laser beam on the keyhole walls, the keyhole wall temperature is a crucial influencing factor when it comes to the assessment of the local metal evaporation rate and the induced local recoil pressure acting on the keyhole wall. Using small high-melting tantalum probes as measuring channels, temperatures in the vicinity of the Knudsen layer at the keyhole front wall were measured at different depths below the sample surface by means of high-speed pyrometry. For this purpose, bead on plate welding was conducted at low process velocities in the Rosenthal regime using pure aluminium (EN AW-1050A) as substrate material. It is shown for different laser powers and process velocities that the melt temperature in the vicinity of the keyhole wall lies in the range of 3000 K ± 400 K, therefore intermittently exceeding the vaporisation temperature of the substrate material. Significant correlations between the keyhole wall temperature and the laser power as well as the measuring depth could not be identified.

Advances in ultrasonic welding of lightweight alloys: A review

Abstract The lightweight alloy sheet materials have been widely used in industries such as automobiles, aviation, and aerospace. However, there are huge challenges in the structural joining process. Likewise, industries are probing new technologies and are rapidly adapting to more complex light alloy materials. The ultrasonic metal welding is a reliable solid-phase joining technology, which has incomparable development prospects in the high-strength joining of lightweight alloy sheet materials. This article summarizes the research progress of ultrasonic welding of aluminum alloy, magnesium alloy, and titanium alloy thin plates in recent years. The key features of this review article are the ultrasonic welding process, advantages, applications, and limitations. It introduces the welding process parameters to explore the breakthroughs for straightforward direction. Furthermore, to strengthen the phenomena, the current state of the ultrasonic welding of lightweight alloys and their future perspectives are also reflected.

Mechanical properties and constitutive models of butt-welds in Q345GJ thick steel plates

GJ steel is a high-performance steel manufactured in China, and its thick plates are widely used in building structures. The first companion study examined the material properties of the thick GJ steel plates (t ≥ 60 mm). This study focuses on the mechanical properties of butt welds in thick GJ steel plates (t ≥ 60 mm). Monotonic and cyclic tests were conducted on butt-weld specimens made of 60-mm and 100-mm thick Q345GJ steel plates in the longitudinal and transverse directions. In addition, the layered specimens obtained from five different thickness locations were tested. Based on the cyclic test results, the Chaboche constitutive parameters were calibrated and verified via the finite element analysis (FEA). Moreover, the differences in the static and cyclic mechanical properties of the base metal and butt welds were analysed. Compared with the base metal, the static tensile strength and hysteretic energy dissipation under the same cyclic loading protocol were better in the weld specimens; however, their ductility was significantly lower. Furthermore, the distribution of the mechanical properties along the thickness direction was more uniform in the weld specimens. Moreover, the weld specimens had higher yield surface reduction ratios. However, their initial and final yield surface sizes were larger than those of the base metals.

Microstructure and mechanical behaviour study of the dissimilar weldment of ‘IN82 buttered’ P92 steel and AISI 304L steel for ultra super critical power plants

This study examines the influence of the ERNiCr-3 (Inconel 82) butter layer on the microstructure and mechanical feature of the dissimilar weld joint (DWJ) of ferritic grade P92 and austenitic grade AISI 304 L steel, manufactured using gas tungsten arc welding (GTAW) method with IN82 filler. The butter layer aims to prevent the formation of a hard martensitic layer adjacent to the fusion line by mitigating the carbon migration from the P92 steel to the welding pool. The optical microscope, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and electron probe microanalyzer (EPMA) were used to examine the microstructures of the buttered welded plate. The mechanical characteristics of the joints were assessed using the standard and sub-sized tensile and Charpy tests. The flat and round specimens underwent the tensile test to determine their relative tensile properties at room temperature and high temperature. The high-temperature tensile properties were assessed at 600 °C and 650 °C at 1 mm/min extension rates. Along the weldments, hardness profilometry was also performed. Microstructural analysis validated that the application of a buttering layer successfully eliminated the extensive martensitic layer on the P92 side. Nevertheless, in the vicinity of the interface between the buttering layer and P92, there was evidence of a narrow unmixed zone and macrosegregation. SEM/EDS and EPMA studies confirmed that the predominant phases identified in IN82 butter and weld metal are NbC and TiC. The butter layer, overall, improved elongation/ductility by 25 % without a noticeable reduction in tensile strength. During tensile testing, the specimen fractured from the IN82 butter layer, revealing the presence of dimples and voids on the fracture surface, along with the TiC/NbC phases, as confirmed by SEM analysis. Tensile specimens subjected to high-temperature testing exhibited failure at the base materials of AISI 304 L (tensile strength=404 MPa) and P92 (307 MPa), specifically at 550 °C and 650 °C, respectively, rather than at the buttering layer or weld metal. The results of the tensile tests met the minimum criteria specified for Ultra-Supercritical (USC) boilers. More importantly, the IN82 butter layer successfully serves as a protective barrier between the weld pool and the P92 HAZ. As a result, the dual hardness peaks on either side of the welding pool are eliminated. After adding the buttering layer, the peak hardness in the coarse-grained heat-affected zone (HAZ) of P92, which ranged from 450 to 500 HV in the unbuttered sample, dropped by 200 MPa. The relationships between microstructural characteristics and mechanical properties have been thoroughly examined and discussed.

Numerical simulation and experimental research on submerged arc welding of stainless steel composite plate

Numerical simulation and experimental research on submerged arc welding of stainless steel composite plate

Electron beam welding of Nb-8Hf-2Ti high temperature alloy to Ni dissimilar joint: The microstructural analysis, mechanical properties, and fracture characterization

In this work, the electron-beam welding (EBW) behavior of Ni/C-103 Nb-based refractory alloy was investigated, in terms of fusion-zone characteristics, texture evolution, mechanical properties, and joint efficiency. Compared to Nb, the higher concentration of Ni in weld zone indicated that the Ni side participates more in welding than the C-103 one. A continuous intermetallic layer was formed at the joint/C-103 interface composed of NbNi3, Nb7Ni6 and Hf3Ni7 phases. Continuous curved-shaped layers composed of columnar NbNi3 and eutectic Nb7Ni6+NbNi3 phases were also observed in the central and lower regions of the weld. These have been peeled off from the C-103 upper walls lateral to the weld and directed to the bottom of the weld pool due to the Marangoni flow. Solidification microcracks internal to the continuous intermetallic layers are also initiated and grown at the final stage of eutectic Nb7Ni6+NbNi3 phase formation leading to the brittle cleavage failure within this layer. The average microhardness of the joint was measured as 562 HV, which was higher than the base metals due to the presence of intermetallic compounds. Tensile strength of the joint was measured as 119.5 MPa, which is approximately one third of the value for the bead on plate weld of C-103 plate using EBW method with a tensile strength of 317.5 MPa. Nb7Ni6 and NbNi3 intermetallics were dominant phases in the fracture area.

Predicting the weld zones size in FSSW of 304L stainless steel plates by mathematical model based on RSM

The 300 series austenitic stainless steels are widely used in industries due to their special properties. High heat in fusion welding reduces the properties of these steels and causes many problems. Therefore, stir friction spot welding, which is a type of solid state welding, is useful and widely used in high-tech industries. In this paper, a 3D dynamic explicit finite element model is developed to simulate the friction stir spot welding of 304L stainless steel plates. Using this model, the temperature distribution and the size of weld zones (thickness of weld zones) are obtained. Then, by experimental study, the results of the temperature and the size of weld zones were obtained to be a criterion for comparing and validating the numerical results. Microstructure and hardness of these zones are determined experimentally. Finally, a mathematical model based on the response surface methodology is proposed to predict the size of weld zones. Good agreement between the numerical results that are produced by the finite element simulation, the proposed model and the experimental data is observed. The results show the maximum temperature level appears in the stir zone and it reduces by moving from the weld center. Also, by increasing the rotational speed, plunging depth and dwell time of the tool, the size of both the stir zone and the heat affected zone increase to a peak value and then the size of the latter zone decreases.

Dynamic evolution of keyhole and weld pool throughout the thickness during keyhole plasma arc welding

Keyhole plasma arc welding (K-PAW) of medium-thick plates often faces instability in the initial keyhole penetration stage, so a thorough investigation of the keyhole and weld pool behavior in this stage is needed. In this paper, a special "sandwich visual sensing structure" was adopted to obtain images of weld pool and keyhole of the SUS304 stainless-steel plate during the plasma arc welding. This method allows direct observation of keyhole growth and weld pool flow throughout the thickness of the workpiece under different welding conditions. When the welding current is reduced, the plasma arc cannot melt through the metal, and the arc sweeps through the keyhole bottom like a “roller coaster”. The trends of keyhole dimensions along different directions during various welding processes were quantitatively investigated. As the weld proceeds to half of the plate thickness, the mutation zone of the rear keyhole wall becomes very common, and the rear keyhole wall's morphology frequently transforms between type I and type II. Weld pool flow characteristics during constant-speed welding were classified into four types. Last, the molten metal flow cycle and the molten metal cloud cluster have been observed by the new visual sensing method. This paper provides the industry with a more intuitive way to study the keyhole and the weld pool for K-PAW, as well as offers important guidance for the first normal penetration in the medium-thickness plate K-PAW process.

Weld beads and defects automatic identification, localization, and size calculation based on a lightweight fully convolutional neural network

Weld quality inspection is a key aspect of modern manufacturing. Automatic identification, location, and dimensioning of welds and defects are necessary for complex industrial environments. Weld and defects dimensional data are important indicators for high precision assessment of weld quality, while precise positioning of welds and defects can provide important location data for subsequent processing. In this study, a novel weld and defects detection, location, and size calculation method is proposed based on deep fully convolutional neural networks. Firstly, 43 high-precision high-power laser weld plate scanned images are automatically cropped to 800 pixels × 800 pixels by the proposed sliding window sampling method for training, testing, and validation, while an image data enhancement method is proposed to quadruple the amount of data to improve the model performance. Next, the OU-net image semantic segmentation model is established to accurately identify different detection targets, which can achieve MIoU and MPA values of 78.15% and 85.18% on the validation set after sufficient training, respectively. Then, the proposed cropped segmentation image fusion recovery method is used to obtain the complete weld segmentation image for a complete display of the different inspection targets on the weld plate. Finally, a detection targets localization and size calculation method is applied to accurately obtain the position data and size data of different targets. The validation results show that the proposed detection strategy can locate and measure every weld seam, collapse, overlap, spatter, and hump on the weld plate.

Особенности формирования сварных соединений алюминиевого сплава АК9, полученного селективным лазерным плавлением

The problem of obtaining high-quality plate welds made of AL9 alloy and powder by selective laser melting is viewed. Welded butt joints of plates of AK9CH alloy with a thickness of 3.0 mm were made by melting welding (automatic argon arc and electron beam welding) and friction stir welding. After welding the base metal of the AK9 alloy plates and their welded joints were subjected to X-ray transmission, computed tomography, metallographic analysis and mechanical tests for static tension and static three-point bending. X-ray inspection of welded joints made by automatic argon arc and electron beam welding revealed multiple porosity inside welds. The nuclei of pores in the weld metal are spherical micropores, formed in the parent metal during selective laser melting. The diameter of these micropores is 150...200 microns. In the welding bath during fusion welding, micropores develop up to 420...1070 microns in diameter in case of argon arc welding and 215...420 microns in case of electron beam welding. Metallographic analysis of cross-sections of welded joints performed by fusion welding revealed a characteristic pore distribution in the weld metal. So in case of argon arc welding, the largest pores were located near the front surface of the weld. In the fusion zone at the border of the weld and the base metal, pores with a diameter of 80.220 microns were located in the form of chains along the entire thickness of the plates being welded. When testing welded joints for static tension, the destruction of joints occurred precisely in this zone. The strength coefficient of the AK9 alloy joints obtained by fusion welding is as follows: for automatic argon arc welding 0.46, for electron beam welding - 0.66. It is established that the problem of porosity of welded joints is eliminated when using solid -phase welding for jointing (friction stir welding). The strength coefficient of the jointing of the AK9CH alloy plates made by friction stir welding is at the level of 0.81.0.86 of the time resistance of the base metal. The destruction of welded joints occurs along the mixing zone. In the weld zone during friction stir welding, as a result of dynamic recrystallization, a fine-grained equiaxed structure with an average grain size of 4.5...6.2 microns was formed with virtually no pores. The parent metal is represented by a cellular structure in which there are pores up to 168 microns in size.

An indentation method for measuring welding residual stress: Estimation of stress-free indentation curve using BP neural network prediction model

The measurement of welding residual stress (WRS) is necessary to formulate the stress control strategies, in order to ensure the reliability of engineering structures during their service life. The instrumented indentation technique can detect surface residual stress nondestructively with an acceptable accuracy, making it a desirable option for in-situ applications. However, it is difficult to meet the requirement for stress-free samples, particularly in the case of welded joints with non-uniform mechanical properties. In this work, the impact of stress-free indentation curves on determining WRS is furtherly studied based on the previously proposed indentation energy difference method. The WRS in a mismatched welded plate is measured using single reference method and distributed reference method, respectively. The study suggests that using the single reference method can lead to significant errors in determining the sign and magnitude of WRS in the weld zone. A prediction model combining the continuous spherical indentation (CSI) method and Back Propagation (BP) neural network is proposed to obtain the stress-free indentation curves of local positions nondestructively. And the CSI-BP method is verified through reverse finite element analysis and experiments.

Multi-Objective Considered Process Parameter Optimization of Welding Robots Based on Small Sample Size Dataset

The welding process is characterized by its high energy density, making it imperative to optimize the energy consumption of welding robots without compromising the quality and efficiency of the welding process for their sustainable development. The above evaluation objectives in a particular welding situation are mostly influenced by the welding process parameters. Although numerical analysis and simulation methods have demonstrated their viability in optimizing process parameters, there are still limitations in terms of modeling accuracy and efficiency. This paper presented a framework for optimizing process parameters of welding robots in industry settings, where data augmentation was applied to expand sample size, auto machine learning theory was incorporated to quantify reflections from process parameters to evaluation objectives, and the enhanced non-dominated sorting algorithm was employed to identify an optimal solution by balancing these objectives. Additionally, an experiment using Q235 as welding plates was designed and conducted on a welding platform, and the findings indicated that the prediction accuracy on different objectives obtained by the enlarged dataset through ensembled models all exceeded 95%. It is proven that the proposed methods enabled the efficient and optimal determination of parameter instructions for welding scenarios and exhibited superior performance compared with other optimization methods in terms of model correctness, modeling efficiency, and method applicability.

Erosion Investigation of Dimple Wall using Erosion-Coupled Dynamic Mesh.

The erosion of the dimple walls is investigated experimentally and numerically. A mathematical simulation framework was proposed to describe quantitatively the morphological evolution of the dimple wall quantitatively. As the wall shape continues to evolve, the wall shear stress, mesh deformation, and erosion rate would decrease and gradually tend to be constant. Two distinct regions have been identified along the dimple's windward wall surface: the wall's central area and the lateral area. In the central region, the wall profile flare occurs mainly in the early stage. In the lateral region, profile flare occurs mainly in the later stages of erosion. The microhardness of the wall surface shows a positive correlation with the erosion rate. The liquid-solid two-phase impinges on the wall at a smaller angle, and the wall material removal process is mainly based on the microcutting and slip mechanism. The results provide theoretical implications for the design of dimple-shaped, wide-channel welded plate heat exchangers.

Influencing mechanisms of weld root tip on microstructure and mechanical properties of electron beam welded joints of titanium alloy thick plates

The welding of titanium alloy thick plates often formed a narrow weld seam in the weld root, named as ‘weld root tip’, because of insufficient fusion, which could reduce the joint properties. In this study, 30 mm-thick Ti-5Al-5Mo-5V-1Cr-1Fe alloy was butt welded via electron beam welding to reveal the influencing mechanisms of the weld root tip on joint microstructure and mechanical properties. The subparallel or parallel weld seam with the weld angles of 0°–3° between the centre line and edge of the fusion zone removed the weld root tip, achieving almost the same mechanical properties with those of the welding zone.

Axial compressive behavior of corroded double-steel-plate composite shear wall with binding bars

Steel structure is susceptible to corrosion, and corrosion will seriously affect its own load-bearing capacity and service life. In this paper, the axial compressive behavior of double-steel-plate composite shear wall (DSCW) with binding bars under different corrosion degrees is experimentally studied. The typical failure modes include the steel plate local buckling, binding bars fracture, concrete crushing, and steel plate weld tearing. The increase of corrosion rate has unfavorable influence on the axial compressive bearing capacity, initial stiffness, and ductility of DSCW. Finite element (FE) models are established to further investigate the axial compressive behavior of DSCW. It is concluded that the concrete and steel plate strength grade, the concrete section area, the steel plate thickness, and the binding bars diameter and spacing significantly affect the axial compressive bearing capacity of DSCW. A formula calculating the axial compressive bearing capacity of corroded DSCW with binding bars is proposed. The formula agrees well with the test results and can provide a reference for the engineering application.

Hybrid Laser-Arc Welding-Induced Distortion Analysis of Large-Scale Thin-Walled Cruise Ship Structures

Abstract In recent years, there has been increasing use of thin-walled structures with a plate thickness of 6–10 mm in the construction of cruise ships. As one of the important processes of cruise ship construction, hybrid laser-arc welding, combining the advantages of laser welding and arc welding, is increasingly applied in thin-walled cruise ships with the objective of reducing panel deformation. However, due to the weak stiffness of the thin-walled structure with a continuous weld length of 4–16 m, complex welding deformation, e.g., buckling deformation, will be prone to occur. This paper analyzed the deformation behavior of large-scale thin-walled cruise ship structures with the change of weld length, structural width, and plate thickness in the hybrid laser-arc welding process. The buckling mode induced by the welding deformation is predicted based on the combination method of thermal elastic–plastic and inherent strain, as well as experimental verification. By analyzing the deformation behavior with the weld length of 5–15 m, when the continuous weld length exceeds 7.5 m during butt welding of large thin-walled cruise ship structures, the welding deformation mode will change from bending deformation to buckling deformation, while the maximum deformation will be reduced by about 50%. Compared with the buckling mode of the traditional thick-walled structures, with the decrease of plate thickness, the buckling mode of large ship structures will change from wave buckling deformation of the whole structure to wave buckling at the edge of structures.