Search Results (28)

Gas metal arc welding (GMAW) is widely used for its productivity and ease of automation across various industries. However, certain tasks in shipbuilding and heavy industry still require manual welding, where quality depends heavily on operator skill. Defects in manual welding often necessitate costly rework, reducing productivity. Vision sensing has become essential in automated welding, capturing dynamic changes in the molten pool and arc length for real-time defect insights. Laser vision sensors are particularly valuable for their high-precision bead profile data; however, most current models require offline inspection, limiting real-time application. This study proposes a deep learning-based system for the real-time monitoring of both the molten pool and weld-bead profile during GMAW. The system integrates an optimized optical design to reduce arc light interference, enabling the continuous acquisition of both molten pool images and 3D bead profiles. Experimental results demonstrate that the molten pool classification models achieved accuracies of 99.76% with ResNet50 and 99.02% with MobileNetV4, fulfilling real-time requirements with inference times of 6.53 ms and 9.06 ms, respectively. By combining 2D and 3D data through a semantic segmentation algorithm, the system enables the accurate, real-time extraction of weld-bead geometry, offering comprehensive weld quality monitoring that satisfies the performance demands of real-time industrial applications. Full article

Laser welding on thin plates of high-strength steel is increasing in various industrial applications. The mechanical behavior of welded joints depends on their local properties, which in turn depend on the welding parameters applied to join the base material. This work characterizes the local properties of butt-welded joints of thin plates of high-strength–low-alloy (HSLA) steel. This study focuses on the effect of welding parameters on the microstructure, tensile response, microhardness, and weld bead profile. For this purpose, a factorial experimental design was formed, covering a heat input range from 53 to 75 J/mm. This study identified the main effects and interactions of welding speed and laser power on the weld bead profile and on its width. The microstructure, weld bead width, hardness, and tensile mechanical properties were significantly influenced by heat input. Furthermore, numerical simulations on real weld bead profiles revealed high values of the stress concentration factor and suggested a correlation with heat input. Full article

The prerequisite of the weld bead finishing is intricately linked to the quality of the welded joint. It constitutes the final, yet pivotal, stage in its formation, significantly influencing the reliability of structural components and machines. This article delineates an innovative post-weld surface finishing method, distinguished by the movement of a specialized cutting tool along a butt weld. This method stands out due to its singular approach to machining allowance, wherein the weld bead height is considered and eradicated in a single pass of the cutting tool. Test samples were made of AISI 304L, AISI 316L stainless steels and EN AW-5058 H321, EN AW-7075 T651 aluminum alloys butt-welded with TIG methods. Following the welding process, the weld bead was finished in accordance with the innovative method to flush the bead and the base metal’s surface. For the quality control of welded joints before and after the weld finishing, two non-destructive testing methods were chosen: Penetrant Testing (PT) and Radiographic Testing (RT). This article provides results from the examination of 2D profile parameters and 3D stereometric characteristics of surface roughness using the optical method. Additionally, metallographic results are presented to assess changes in the microstructure, the microhardness, and the degree of hardening within the surface layer induced by the application of the innovative post-weld finishing method. Full article

This study focuses on metal inert gas welding for nickel alloy additive manufacturing using both cold metal transfer (CMT) and pulse multi control (PMT). For both single- and dual-bead deposition, the key parameters (current, travel speed, feed, weave, and height offset) were tuned. A hollow square component of 20 mm in height, 60 mm side length, and 16 mm width was created using these measurements. A macrostructural study demonstrated that flawless accuracy in geometry was attained by both PMT and CMT. In comparison to PMT, CMT specimens showed increased interlayer hardness but decreased hardness in the deposited layers. These changes were explained by modifications in eutectic phase size, distribution, and partial dissolution at the contact. For the wire arc additive manufacturing of nickel alloy components, pulse multi control is preferred over cold metal transfer. Full article

In order to explore the relationship between welding thermal cycles and the thermal field during the repair process of dies, a numerical simulation software (SYSWELD) was employed to construct a thermo-mechanical coupled model. The influence of various inter-layer cooling times was investigated on heat accumulation, residual stress, and deformation of the repaired component. The results showed that the numerical simulation results agreed well with experimental data. The temperature within the cladding layer gradually rose as the number of weld beads increased, leading to a more pronounced accumulation of heat. The residual stress exhibited a double-peak profile, where the deformation of the repaired component was large at both ends but small in the middle. The less heat was accumulated in the cladding layer with a prolonged cooling time. Meanwhile, the residual stress and deformation in the repaired component experienced a gradual decrease in magnitude. The numerical simulation results demonstrated that the microstructure of the repaired component predominantly consisted of martensite and residual austenite at the optimal cooling time (300 s). Furthermore, the microhardness and wear resistance of the cladding zone significantly surpassed those of the substrate. In conclusion, this study suggested the prolonged cooling time mitigated heat accumulation, residual stress, and deformation in repaired components, which provided a new direction for future research on the die steel repairments. Full article

The article describes an innovative post-weld surface finishing method, which is characterized by moving a specialized cutting tool along a butt weld. The aforementioned method is unique for the machining allowance, which is treated as the weld bead height and is removed in one step with one pass of the cutting tool. The tool is equipped on one side with linearly arranged tooth-shaped cutting elements, with the adjacent teeth height changing and increasing according to the direction of the feed. The non-standard geometry of the cutting tool enables the finishing of a heterogeneous post-weld surface with increased hardness. The results of studying the 2D profile parameters and the 3D stereometric characteristics of the surface roughness using the optical method are presented in the article. Test samples were made of S235JR steel and butt welded with the MMA, MIG, and TIG methods. Subsequently, the welding bead was ground and finished in accordance with the innovative method to flush the bead and the base metal’s surface. Additionally, residual stress analyses were performed using the X-ray diffraction method in the surface layers of the test samples. Based on the conducted research, the influence of the innovative finishing method on the surface quality is described. Full article

A quantitative and qualitative study of the effect of laser (light amplification by stimulated emissions of radiation) welding parameters, such as focus point, welding speed, power beam and shield gas on bead profile in relation with microchemistry compositions differences of two thin AISI 316 industrial stainless steel casts have been studied. One cast contains 60 ppm (0.006%) of sulfur considered as high sulfur content and the other one contains 10 ppm (0.001 %) sulfur which can be considered as low sulfur content. A set of 27 tests were carried out by combining three welding speeds (1500, 3000, and 4500 mm/min), three shield gases (helium (He), mixture of 40% helium and 60% argon (Ar) and mixture of 70% helium and 30% argon) with flow rate of 15 L/min, and three focal lengths (+2, +7, and +12 mm). The depth, aspect ratio (the ratio between the penetration depth weld and the weld width) and the bead cross section profile are investigated using response surface methodology (RSM). Linear and quadratic polynomial models for predicting the weld bead geometry were developed. The results of the preliminary validation indicated that the proposed models predict the responses adequately. The geometry of the welded area was analyzed using optical microscopy, and correlations between weld morphology (depth, weld aspect parameter and weld area) and welding parameters were performed. For the cast 316 HS (high sulfur content), the main input factor influencing the depth weld (Y_d) is the focus point with a contribution up to 19.32. On the other hand, the main input factor affecting the depth weld (Y_d) of the cast 316 LS (low sulfur content) is the combination effect of focus point and power input energy with contribution up to 10.65%. Sulfur as the surfactant element contributes to determining the laser weld bead shape up to 71% when the welds are partially penetrated and diminishes to 50% when the welds are fully penetrated with the occurrence of the keyhole mechanism. Full article

The reconstruction of the geometry of weld-deposited materials plays an important role in the control of the torch path in GMAW. This technique, which is classified as a direct energy deposition technology, is experiencing a new emergence due to its use in welding and additive manufacturing. Usually, the torch path is determined by computerised fabrication tools, but these software tools do not consider the geometrical changes along the case during the process. The aim of this work is to adaptively define the trajectories between layers by analysing the geometry and symmetry of previously deposited layers. The novelty of this work is the integration of a profiling laser coupled to the production system, which scans the deposited layers. Once the layer is scanned, the geometry of the deposited bead can be reconstructed and the symmetry in the geometry and a continuous trajectory can be determined. A wall was fabricated under demanding deposition conditions, and a surface quality of around 100 microns and mechanical properties in line with those previously reported in the literature are observed. Full article

Tandem SAW (Submerged Arc Welding) is one welding process that has been applied to maximize the welding productivity at the panel stage in ship building field. The weld bead profiles produced by Tandem SA welding exceed the acceptance criteria specified in some international regulations, such as AWS D1.1, ISO 5817 and NORSOK M-101. These regulations limit the applicable weld bead profiles, especially weld bead height, regardless of any consideration of design category. The fundamental reason for the limitation of weld bead profiles is related to the weldment fatigue properties. In this regard, we have investigated the effect of weld profiles on fatigue properties. The effect of weld bead profiles on fatigue properties has been experimentally verified and statistically analyzed, and new criteria for weld bead profiles which satisfy E curve as the design S-N curve are proposed for tandem SA welding. Full article

The need for thin foil welding is increasing significantly, particularly in the electronic industries. The technologies that are currently available limit the joining processes in terms of materials and their geometries. In this paper, a series of trials of fusion welding (bead-on- plate) of commercially pure titanium (CPTi) foils were conducted using a blue diode laser (BDL) welding method. The power used was 50 W and 100 W for 0.1 mm and 0.2 mm thick foils, respectively. Following welding, various samples were prepared to examine the weld profiles, microstructures, hardness, tensile strength, and fracture surface characteristics. The results showed that the base metal (BM) had an annealed microstructure with equiaxed grains, while the weld zones contained martensite (α’) with large grains. The hardness increased in both regions, from around 123 HV to around 250 HV, in the heat-affected zone (HAZ) and fusion zone (FZ) areas. The tensile tests revealed that the strengths of the welded samples were slightly lower than the unwelded samples, i.e., UTS = 300–350 MPa compared with 325–390 MPa for the unwelded samples. Fracture took place within the BM area. All of the samples, welded and unwelded, showed identical fracture mechanisms, i.e., microvoid coalescence or ductile fracture. The weld zone experienced very small strains (elongation) at fracture, which indicates a good weld quality. Full article

Flux formulations are specified to target chemical and physico-chemical parameters. Chemical parameters set flux element transfer behaviours and weld metal oxygen contents. Physico-chemical parameters such as slag viscosity, surface tension and melting range are targeted to ensure an acceptable weld bead profile and surface appearance. Slag detachability is an important physico-chemical property required to ensure high welding productivity, smooth weld bead surface and no slag entrapment. Here, bead-on-plate welding tests were made with and without metal powder additions, including aluminium powder as a de-oxidiser. Difficult slag detachability was observed in weld runs made with metal powder additions. Mineralogy of the post-weld slags, and thermochemical calculations, show that the flux was modified due to the aluminothermic reduction of MnO and SiO₂ from the slag to form alumina. Increased quantities of spinel phase were identified in the post-weld slag samples, at the weld pool–slag interface. The combined effect of increased slag viscosity, from increased spinel in the slag, and lowered weld pool solidus temperature, resulted in the formation of a rough bead surface morphology, which, in turn, caused mechanical fixation of the slag to the weld bead. Flux modification to higher CaF₂ content should ensure that higher quantities of spinel phase can be tolerated in the slag. Full article

Bead size and shape are important considerations for industry design and quality detection. It is hard to deduce an appropriate mathematical model for predicting the bead geometry in a continually changing welding process due to the complex interrelationship between different welding parameters and the actual bead. In this paper, an artificial neural network model for predicting the bead geometry with changing welding speed was developed. The experiment was performed by a welding robot in gas metal arc welding process. The welding speed was stochastically changed during the welding process. By transient response tests, it was indicated that the changing welding speed had a spatial influence on bead geometry, which ranged from 10 mm backward to 22 mm forward with certain welding parameters. For this study, the input parameters of model were the spatial welding speed sequence, and the output parameters were bead width and reinforcement. The bead geometry was recognized by polynomial fitting of the profile coordinates, as measured by a structured laser light sensor. The results showed that the model with the structure of 33-6-2 had achieved high accuracy in both the training dataset and test dataset, which were 99% and 96%, respectively. Full article

The existing S-N curves by effective notch stress to assess the fatigue life of gusset welded joints can result in reduced accuracy due to the oversimplification of bead geometries. The present work proposes the parametric formulae of stress concentration factor (SCF) for as-welded gusset joints based on the spline model, by which the effective notch stress can be accurately calculated for fatigue resistance assessment. The spline model is also modified to make it applicable to the additional weld. The fatigue resistance of as-welded and additional-welded specimens is assessed considering the geometric effects and weld profiles. The results show that the error of SCFs by the proposed formulae is proven to be smaller than 5%. The additional weld can increase the fatigue life by as great as 9.4 times, mainly because the increasing weld toe radius and weld leg length lead to the smaller SCF. The proposed series of S-N curves, considering different SCFs, can be used to assess the welded joints with various geometric parameters and weld profiles. Full article

In many applications that use high strength steels, structural integrity depends greatly on weld quality. Imperfections and the weld bead geometry are influencing factors on mechanical properties of the welded joints but, especially in the fatigue strength, they cause a great decrease. The proper knowledge of these two factors is important from the nominal stress approach to the fracture mechanics approaches. Studies concerning the profile and imperfections of the weld bead in laser welding for thin plates of high strength steels are scarce. In this work, these two aspects are covered for five series single and double-welded joints, butt joints in a 3 mm thick HSLA steel, welded in a small range of welding parameters. The actual profiles captured with profilometer were modeled with proposed geometric parameters achieving an adequate fit with values of the coefficient of determination ℜ² greater than 0.9000. Description of imperfections includes the distributions of porosity and undercuts. The evaluation of the weld quality, taking as guide the ISO 13919-1 standard determined B and D levels for the welded series while based on the stress-concentrating effect, showed a greater detriment in those series with undercuts and excessive penetration. The analysis of variance validated the results of the different combinations of laser welding parameters and showed, for the factorial experimental design, a more significant effect of the welding speed. Full article