Search Results (157)

This study investigated into how different current input levels during cold metal transfer (CMT) welding affected the characteristics of the weld bead. For the current variation, three input values were taken: 80 A, 90 A, and 100 A. Weld beads fabricated from all three current inputs were compared by analysing their microstructure, microhardness, tensile strength, and residual stress. The microhardness of the weld bead decreased when the current parameter was increased from 80 A to 100 A. The average tensile strength increased from 80 A to 90 A. The lowest residual stress calculated was −135 MPa with 100 A current. Full article

E36 steel, widely used in shipbuilding and offshore structures, offers moderate strength and excellent low-temperature toughness. However, its welded joints are highly susceptible to fatigue failure. Cracks typically initiate at weld toes or within the heat-affected zone (HAZ), severely limiting the fatigue life of fabricated components. Traditional life prediction methods are complex, inefficient, and lack accuracy. This study proposes a machine learning (ML) framework for efficient fatigue life prediction of E36 welded joints. Welded specimens using SQJ501 filler wire on prepared E36 steel established a dataset from 23 original fatigue test data points. The dataset was expanded via Z-parameter model fitting, with data scarcity addressed using SMOTE. Pearson correlation analysis validated data relationships. After grid-optimized training on the augmented data, models were evaluated on the original dataset. Results demonstrate that the machine learning models significantly outperformed the Z-parameter formula (R² = 0.643, MAPE = 16.15%). The artificial neural network (R² = 0.972, MAPE = 4.45%) delivered the best overall performance, while the random forest model exhibited high consistency between validation (R² = 0.888, MAPE = 6.34%) and testing sets (R² = 0.897), with its error being significantly lower than that of support vector regression. Full article

The microstructure and mechanical properties of welded joints of API 5L X-52 steel plates cladded with AISI 316L-Si austenitic stainless steel were evaluated. The gas metal arc welding process with pulsed arc (GMAW-P) and controlled arc oscillation were used to join the bimetallic plates. After the root welding pass, buttering with an ERNiCrMo-3 filler wire was performed and multi-pass welding followed using an ER70S-6 electrode. The results obtained by optical and scanning electron microscopy indicated that the shielding atmosphere, welding parameters, and electric arc oscillation enabled good arc stability and proper molten metal transfer from the filler wire to the sidewalls of the joint during welding. Vickers microhardness (HV) and tensile tests were performed for correlating microstructural and mechanical properties. The mixture of ERNiCrMo-3 and ER70S-6 filler materials presented fine interlocked grains with a honeycomb network shape of the Ni–Fe mixture with Ni-rich grain boundaries and a cellular-dendritic and equiaxed solidification. Variation of microhardness at the weld metal (WM) in the middle zone of the bimetallic welded joints (BWJ) is associated with the manipulation of the welding parameters, promoting precipitation of carbides in the austenitic matrix and formation of martensite during solidification of the weld pool and cooling of the WM. The BWJ exhibited a mechanical strength of 380 and 520 MPa for the yield stress and ultimate tensile strength, respectively. These values are close to those of the as-received API 5L X-52 steel. Full article

Taguchi and post-heat treatment methods have been used in this study to optimize the metal inert gas (MIG) welding joints between SUS304 austenite stainless steel and plain carbon SS400 steel using AWS ER 308L filler wire. The dissimilar welding joints’ microstructure and tensile strength have been examined. The findings show that the fast cooling of the weld joint and the ferrite-forming element of the filler wire cause the dendrites’ δ-ferrite phase to emerge on both the weld bead and the heat-affected zone (HAZ) of the SUS304 side. The stickout parameter has the largest impact on the ultimate tensile strength (UTS), next to the welding speed, welding voltage, and welding current, due to the strong impact of the heat distribution. The optimal welding parameters are a welding current of 105 A, a welding voltage of 14.5 V, a stickout of 12 mm, and a welding speed of 420 mm/min, producing the UTS value of 445.3 MPa, which is close to the predicted value of 469.2 ± 53.6 MPa. Post-heat treatment with an annealing temperature that is lower than 700 °C could improve the optimized weld joints’ strength by up to 5%. The findings may provide a more realistic understanding of the dissimilar welding technology. Full article

Laser–MIG hybrid welding–brazing was performed to join TC4 titanium alloy and 5083 aluminum alloy with ER5356, ER4043 and ER2319 filler wires. The effects of the different filler wires on the microstructural features and mechanical properties of Ti/Al welded–brazed butt joints were investigated in detail. The wetting and spreading effect of the ER4043 filler wire was the best, especially on the weld’s rear surface. Serrated-shaped and rod-like IMCs were generated at the top region of the interface of the joint with ER4043 filler wire, but rod-like IMCs did not appear at the joints with the other filler wires. Only serrated-shaped IMCs appeared in the middle and bottom regions for the three filler wires. The phase compositions of all the IMCs were inferred as being made up of TiAl₃. The average thickness of the IMC layer of joints with the ER5356 and ER2319 filler wires was almost the same and thinner than that of the joint with the ER4043 filler wire. The average thickness was largest in the middle region and smallest in the bottom region for all the joints with the three filler wires. The average microhardness in the weld metal of ER5356, ER4043 and ER2319 filler wires could reach up to 77.7 HV, 91.2 HV and 85.4 HV, respectively. The average tensile strength of joints with the ER5356, ER4043 and ER2319 filler wires was 106 MPa, 238 MPa and 192 MPa, respectively. The tensile samples all fractured at the IMC interface and showed a mixed brittle–ductile fracture feature. These research results could help confirm the appropriate filler wire for the laser–MIG hybrid welding–brazing of Ti/Al dissimilar butt joints. Full article

Wire and arc additive manufacturing (WAAM) is a promising method of producing medium- and large-sized aluminum alloy structures, though it faces challenges such as porosity, residual stresses and inconsistent mechanical properties. This study investigates the effect of current type (AC and DC MIG welding) and polarity balance (influencing the duration of the positive/negative period of the cycle) on the mechanical and microstructural properties of 6063 aluminum alloy walls produced by WAAM. A TiB₂-refined Al–Mg–Si (6063) filler wire, specifically developed for arc-based processing, was used. Tensile tests, Vickers hardness measurements (HV5), optical microscopy and X-ray diffraction based on cosα method were used to evaluate performance in terms of strength, ductility, hardness, grain structure, porosity and residual stress. The results showed that the balance of AC polarity significantly affects wall geometry, porosity and grain structure. Increasing the negative polarity period resulted in taller and narrower walls, while the widest walls were produced with increased positive polarity. Residual stress measurements revealed a tensile–compressive–tensile distribution, with the DC-MIG samples showing the highest surface stress values. The highest tensile strength (172 MPa) was measured in the lower region of the DC-MIG sample, suggesting that areas near the substrate benefit from faster cooling. Full article

This paper investigates self-shielded flux-cored wires with an exothermic MnO₂-Al addition and the effect of hardfacing modes on the deposited alloy of the Fe-C-Mn system for the first time. Additionally, the paper proposes a new experimental research methodology using an orthogonal experimental design with nine experiments and three levels. At the first stage, it is proposed to use the Taguchi plan (L9) method to find the most significant variables. At the second stage, for the development of a mathematical model and optimization, a factorial design is recommended. The studied parameters of the hardfacing mode were travel speed (TS), set voltage on the power source (U_set), contact tip to work distance (CTWD), and wire feed speed (WFS). The following parameters were studied: welding thermal cycle parameters, microstructure, grain size, non-metallic inclusions, and mechanical properties. The results of the analysis showed that the listed parameters of the hardfacing modes have a different effect on the characteristics of the hardfacing process with self-shielded flux-cored wires with an exothermic addition in the filler. It was determined that for flux-cored wires with an exothermic addition, the size of the deposited metal grain size is most affected by the contact tip to work distance (CTWD). The research results showed that the travel speed (TS) had the main influence on the thermal cycle parameters (heat input, cooling time) and hardness. The analysis of the deposited metal samples showed that an increase in the travel speed had a negative impact on the number of non-metallic inclusions (NMIs) in the deposited metal. While the size of NMIs was influenced by the wire feed speed and the set voltage on the power source. Full article

TC4 titanium alloy and 5083 aluminum alloy with different groove shapes were joined by laser-MIG hybrid welding–brazing using ER4043 filler wire. The effects of groove shape on the weld formation, intermetallic compounds and tensile property of the Ti/Al butt joints were investigated. The welds without obvious defects could be obtained with grooves of I-shape and V-shape on Ti side, while welds quality with grooves of V-shape on Al side and V-shape on both sides were slightly worse. The interfacial intermetallic compounds (IMCs) on the brazing interface were homogeneous in the joints with groove of V-shape on Ti side, and V-shape on both sides, which had similar thickness and were both composed of TiAl₃. Unlike the IMCs mainly composed of TiAl₃ at the I-shape groove interface, TiAl₃, TiAl, and Ti₃Al constituted the IMCs at the V-shape on Al side interface. The average tensile strength of Ti/Al joints with groove of I-shape was the highest at 238 MPa, and was lowest at 140 MPa with groove of V-shape on Al side. The tensile samples mainly fractured at IMCs interface and the fractured surfaces all exhibited mixed brittle–ductile fracture mode. Based on the above research results, I-shape groove was recommended for laser-arc hybrid welding–brazing of 4 mm thick Ti/Al dissimilar butt joints. Full article

Metal inert gas (MIG) brazing was used to join galvanized thin sheets with thicknesses in the range of 0.8 to 2 mm in a lap joint configuration using CuAl₈ wire as filler. The process was used to manufacture built-up cold-formed steel beams composed of corrugated steel webs and flanges made from thin-walled cold-formed steel lipped channel profiles. The effect of heat input and sheet thickness on joint properties, such as macro- and microstructure, wettability, and mechanical characteristics such as microhardness and tensile strength were investigated. The bead geometry was assessed by studying the wettability of the filler material. The microstructure was investigated by digital and scanning electron microscopy, and the composition in the heat-affected zone (HAZ), interface, and bead was determined by energy dispersive spectroscopy. Formation of Fe–Al intermetallics was observed in the bead at the bead–base material interface. Some pores were noticed that formed due to the evaporation of the zinc coating. The bead shape and mechanical properties were found to be the best when 1.2 and 2 mm sheets were brazed using a heat input of 121.4 J/mm. This suggests that not only the heat input but also the thickness of the sheet metal play a crucial role in the production of MIG brazed joints. Full article

One of the prospective methods of robotic welding with a consumable electrode in shield gas metal arc welding is the GMAW Rapid HF process (GRHF, HF-high frequency), in which welded joints with deep penetration welds are obtained thanks to the specially programmed welding characteristics of the arc. A pulsed frequency equalized to 5000 Hz was used to achieve consumable electrode arc stabilization and improve penetration. This work consists of two main sections, including the research and analysis of wire electrode melting and weld pool formation in the innovative GRHF process and its influences on joint strength and the economic advantages of welding. As a result of our research and strength tests, as well as an image analysis of phenomena occurring in the welding arc and weld pool, assumptions were developed about the use of the GRHF process, which is characterized by deep penetration welds without welding imperfections that reduce the quality of the welded joints and their strength. Welding conditions and parameters leading to welded joints characterized by high relative strength related to the weight of the used filler material were proposed. As a result of our research, it was found that the use of welding processes with deep penetration leads to material savings related to the reduced consumption of filler materials while maintaining the required high strength of welded joints. Savings of filler materials reaching 80% were achieved compared with hitherto used methods. At the same time, the maximum load-carrying capacity of welding joints was maintained. Full article

This study investigates the effects of heat transfer and molten pool flow behavior on the final structure of laser filler wire welds, aiming to improve weld quality. Laser filler wire welding experiments and numerical simulations were performed on 2195 Al-Li alloy workpieces with varying welding parameters. Numerical simulation of the heat transfer and flow in the molten pool was carried out using the CFD method, and the moving filler wire was introduced from the computational boundary by secondary development. Simulation results indicated that reducing welding speed and increasing wire feeding rate enhanced the cooling rate of the weld. Additionally, energy absorbed by the filler wire contributed between 6% and 16% of the total energy input during the liquid bridge transition. Comparing experimental and simulation data revealed that the cooling rate significantly affected the weld’s micro-structure and hardness. Notably, the formation of the equiaxed grain zone (EQZ) was crucial for weld performance. Excessive cooling rates hindered EQZ formation, reducing flow in this critical region. These findings offer valuable insights for optimizing welding parameters to enhance weld quality and performance. Full article

Orbital TIG welding is widely applied to weld pipes to pipes in many fields, such as food, chemicals, oil, gas, and transportation. Optimizing welding parameters such as voltage, current, and travel speed is critical to achieve a good-quality weld. This study investigated the impacts of orbital welding parameters and filler wire diameters on the tensile strength of 304 stainless steel pipes. The 304 stainless steel pipe has an outer diameter of 76 mm and a thickness of 2 mm. Filler wire is used with the workpiece, and is available in three diameters of 0.8 mm, 1 mm, and 1.2 mm, wire feed speed from 3.8 mm/s to 5.6 mm/s, current from 90 A to 110 A, and travel speed fixed at 5.5 mm/s. The highest tensile strength of 562 MPa was achieved with heat input of 0.32 kJ/mm and wire feed speed of 3.8 mm/s. In addition, the best parameters via the Taguchi method were found. The parameters’ influence trends on the weld quality were also revealed. Full article

Laser welding–brazing experiments with 6061 aluminum alloy and Q235 steel were conducted using AlSi12 and ZnAl22 as filler metals. The macroscopic morphologies and microstructures of welding–brazing joints were analyzed by optical microscopy (OM) and scanning electron microscopy (SEM). The effects of Si and Zn elements in filler wires on the macroscopic morphologies, interfacial microstructures, tensile properties, and corrosion resistances of joints were studied. The results show that the wettability of ZnAl22-filler wire was better than that of AlSi12-filler wire. The fusion zone of the joint welded with AlSi12-filler wire consisted of α–Al solid solution and Al–Si eutectic mixture, while the interfacial reaction zone was composed of η-Fe₂(Al, Si)₅ and τ₅-Fe_1.8Al_7.2Si. The fusion zone of the joint formed using AlZn22-filler wire consisted of α–Al solid solution, η-Zn solid solution, and ZnAl eutectic structure. The joint welded with AlSi12-filler wire showed better tensile strength and corrosion resistance compared to that welded with ZnAl22-filler wire. Full article

The combined use of laser beam and electric arc for welding thick clad steel plates in a single pass has been developed to solve the issues concerning the individual applications of the heat sources, such as the low filling efficiency of conventional electric arc methods and the drawbacks concerning laser beam defects due to rapid cooling and solidification. This work was addressed to the weldability assessment of ferritic steel plates, clad with austenitic stainless steel, under the laser-leading configuration, testing the effects of two different values of the inter-distance between the laser beam and the electric arc. Specimens of the welded zone were investigated by metallographic observations and EDS measurements; mechanical properties were characterized by the Vickers microhardness test and by the FIMEC instrumented indentation test to obtain the local values of the yield strength. Welding simulations by theoretical modelling were also carried out to outline the differences in the thermal fields generated by the two heat sources, their interaction, and their effect on the configurations of the weld pool and the thermal profiles to which the materials are subjected. The welding setup with higher inter-distance was more suitable for joining clad steel plates, since the action of the deep keyhole mode is substantially separated from that of the shallower electric arc. In this way, the addition of alloying elements, performed by melting the filler wire, concentrated in the cladding layer, helping maintain the austenitic microstructure, while the laser beam acts in depth along the thickness, autogenously welding the base steel. Full article

The development of MIG (metal inert gas) welding for five-series aluminum alloys primarily involves the improvement and optimization of welding processes. Building upon research findings regarding the enhancement of aluminum alloy properties through the use of scandium (Sc) and erbium (Er), our study incorporates Sc and Er into the welding wire to examine their impact on welding quality. The results show that the introduction of Er and Sc results in grain refinement from 47 µm to 29 µm and 31 µm, respectively. Grain refinement is mainly attributed to the heterogeneous nucleation of submicron-sized, coherent Al₃Er and Al₃Sc phases with L12 structure. The ultimate tensile strength (UTS), fracture elongation EI [%], and microhardness of joints welded with Er-containing and Sc-containing filler wires exhibit significant enhancements due to the refinement strengthening and dispersion strengthening. Joints welded with the filler wires containing Er and Sc display reduced corrosion current density and higher corrosion potential. The enhanced corrosion resistance comes from the formation of a denser oxide film and the equilibrium in the potential difference between the precipitated phases (Al₃Er and Al₃Sc) and the matrix. Filler wires containing Er and Sc have almost similar effects on improvements of the MIG welding joints. Full article