The use of shielded metal arc welding (SMAW) equipment to synthesize alloys is one of the most promising methods as it can be used for in-situ fabrication. The hardness and corrosion properties of ...the deposited layer during the welding process can be enhanced by dilution of nichrome (NiCr) during the process. Therefore, the alloy was synthesized on the surface of the mild steel using SMAW equipment with various NiCr additions. The properties of the alloy were investigated using an X-ray diffraction (XRD), an Optical microscope, a Potentiostat, and a Vickers hardness apparatus. The appearance of martensite overlaps with the ferrite phase could be affected by the addition of NiCr to the alloy. An increase in NiCr content is followed by an increase in the lattice parameter value of the ferrite phase. The presence of a certain amount of nickel (Ni) contributes to the formation of lower transformation phases, including martensite. At the same time, the incorporation of chromium (Cr) also plays a significant role in promoting the formation of acicular ferrite. An increase in NiCr content in NiCr2 and NiCr3 samples results in a quantitative increase in martensite formation. Adding 0.434 g of NiCr to the weld deposited layer could result in the corrosion rate of the alloy being 0.1118 mm/y. Higher hardness is found in the NiCr3 sample, around 742.06 HV.
Ultrasonic welding is a joining technology suitable for carbon-fiber-reinforced thermoplastic (CFRTP) components because of its high throughput, and ease of automation. An effective online ...weld-quality inspection technology can promote the industrial application of ultrasonic composite welding. Literature focused on the quality inspection of ultrasonic composite welding is scarce. To address this, the present study proposes an online weld-quality inspection method for ultrasonic composite welding by combining artificial intelligence (AI) technologies with welding process signatures. The failure load in a tensile-shear test and the weld quality level (i.e., under weld, normal weld, and over weld) are predicted simultaneously using artificial neural network (ANN) and random forest (RF) models. Eight features consisting of the duration and energy at each welding stage are extracted from the process signatures as independent variables. The results indicate that both the ANN and RF models exhibit high prediction accuracies. The weld quality can be assessed comprehensively and reasonably by considering both the failure load and weld quality level. The findings of this study demonstrate the feasibility of online weld-quality inspection for ultrasonic composite welding.
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•A quality inspection method for ultrasonic composite welding by combining AI technologies with process signals is proposed.•The failure load and weld quality level are predicted simultaneously by artificial neural network and random forest models.•The weld quality can be assessed more comprehensively by considering both the failure load and the weld quality level.
In this paper the authors present the application of a modern tool of quality management for improving the quality of welded subassemblies. A tree diagram has been developed which illustrates the ...measures needed to improve the quality of welded subassemblies. The proposed measures were based on a preliminary study of the causes which generate welding defects.
•Three-line structured light is used to guide the starting point of the weld, and the path planning and welding attitude planning are carried out simultaneously, which takes advantage of the large ...amount of information obtained by three-line structured light and its high efficiency and convenience.•The Gaussian weighted plane fitting method is proposed in the process of 3D reconstruction of weld topography, which can achieve high-precision plane fitting while reducing the amount of data, and providing important information for the subsequent adjustment of welding process parameters.•The GA-BP neural network and equal height filling approach were employed to forecast the process parameters for non-swing welding and swing welding. Experimental results demonstrated that the prediction accuracy aligns with welding technology standards, offering a theoretical foundation for adjusting welding process parameters.
In order to realize the intelligence and flexibility of V- groove robot welding of medium-thick plates, a multi-layer welding process control strategy for welding with a weaving robot is proposed based on three-wire structural light vision. For the optical localization of the welding start point, a “rough first, accurate later” guidance approach is proposed. A technique utilizing Gaussian-weighted plane fitting is employed to model the groove and extract information about the weld shape. The welding torch’s orientation planning is based on the angular bisector of the groove, and the GA-BP neural network is utilized to forecast welding parameters for various welding techniques. It is shown that the strategy in this paper can guide the robot to complete the welding job. The error between the guide start point and the actual welding start point does not exceed 2 mm, and the predicted welding parameter results align with the welding technology standards.
•LHW, EBW and GMAW processes were used to join butt-welds made of two different UHSS.•Fatigue behaviour of welds was assessed by means of the resistance curve concept.•Weld macro-geometry could not ...solely explain the differences between SN curves.•Weld defects in LHW and EBW played an important role in fatigue strength reduction.•Welds made with GMAW showed high quality profile and enhanced fatigue strength.
In the last decades, advances in steel manufacturing made possible the use of high-strength steel (HSS) and ultra-high strength steel (UHSS) for several applications, such as bridges, cranes, offshore structures, oil pipelines and automotive parts. Capacity of withstanding loads with reduced cross-section and minimum weight could be efficiently increased. Since most structures need to be joined, welding procedures are a major issue in mechanical design of HSS elements. Particularly in construction codes and design documents, it is normally assumed that fatigue resistance of as-welded joints is independent of strength level. Nevertheless, fatigue loaded as-welded components with high quality welds or post-weld treated joints could experience benefits from the use of HSS as the base material (BM).
The purpose of the present work is to analyse fatigue behaviour of ultra-high strength steel butt-welded joints, by means of experimental testing and a fracture mechanics approach. Sheets of steel S960MC and S960QL were joined with different welding techniques: Gas Metal Arc Welding (GMAW), Laser Hybrid Welding (LHW) and Electron Beam Welding (EBW). Fatigue tests were performed with stress ratio R=0.1, under four points bending loading.
All specimens exhibited fatigue crack initiation and subsequent propagation from the weld toe area, near the heat affected zone (HAZ). Different SN curves were obtained for the different welding processes. The Resistance Curve methodology was employed to assess the effect of microstructure, defect size, hardness, and joint geometry resulting from each technique. This fracture mechanics approach allowed to estimate the relative influence of the different geometrical and mechanical parameters of the weld and showed that joint geometry could not explain by itself the differences in fatigue strength. It was observed that microstructure and the size of defects played an important role in early crack growth, and they can reduce the benign effect of a high-strength base material.
In this paper, dissimilar aluminum (Al) and copper (Cu) metals were joined together using ultrasonic metal welding (USMW), a solid-state welding technology. From the perspective of increasing the ...base metal welding contact area, the Cu/Al mating surface was innovatively prepared and ultrasonically welded. A comprehensive analysis was carried out on the forming quality, welding process temperature, interface structure, and mechanical properties of the welded joint. Defect-free and squeezed welds were successfully achieved by machining novel patterns especially C4-2. The results indicated that the reference joint can withstand higher loads, but its failure mode is very unstable. Failure may occur at welded interface and on the aluminum plate which is not good for actual production applications. Welded strength of reference joint was 4493 N, and the welded strength of C4-2 joint was 3691 N. However, microscopic analysis discovered that the welded joint internal morphology in C4-2 was more stable and hardest. C4-2 joint has successfully achieved higher tensile strength and stability under failure displacement of 38% which is higher than C4-1 joint. All welded joint failures occurred on aluminum plate, indicating that the joint strength is higher than that of bottom plate. This is attributed to unique structural design of chiseled joint and lesser thickness. SEM–EDS results investigated that the C4-2 joint can transfer more energy to area under welding head which provides welded joint with robust diffusion capacity. The transition layer has a higher thickness while the energy transferred to area away from welding head was smaller. Thickness of transition layer is significantly reduced and reference joint has similar diffusion characteristics. Conversely, the thickness of the transition layer at the corresponding position is smaller than that of pattern morphology. This is due to overall smaller thickness of the pattern joint which is more conducive to the transfer of welding energy. The surface-conformed approach and comprehensive temperature analysis provide a new understanding of USMW in dissimilar welded metals.
The present study deals with the effect of shielded metal arc welding (SMAW) and gas metal arc welding (GMAW) processes with different welding speeds on microstructural and mechanical properties ...including intergranular corrosion susceptibility of ultra-low nickel chrome-manganese austenitic stainless steel (ASS). The microstructural analysis was performed by an optical microscope. The Fisher Ferritscope was used for determining ferrite content in the weldment. The microstructural analysis shows that the size of dendrites of δ ferrite and the width of heat affected zone (HAZ) decreases when welding speed increases. It was found more δ-ferrite in SMAW weld compared to GMAW weld. It was also found that when welding speed increases, tensile strength, impact strength and hardness values decrease for both welding processes. From the U-bending test, it was found that the welded joints are strong enough to withstand bend at 1800 without any cracks for both welding processes. It was also found that Cr-Mn ASS weld becomes susceptible to intergranular corrosion on welding. For both welding processes, the degree of sensitization value decreases with an increase in welding speed for both the welding processes as evaluated by the double loop electrochemical potentiodynamic reactivation (DLEPR) test. Also, the weld joint made using the GMAW process is more susceptible to intergranular corrosion than that made using the SMAW process.
This paper presents some technical aspects related to welding processes in the context of reducing environmental pollution. The authors propose a series of actions to make the welding process ...environmentally friendly. Also, the paper presents schematically the main stages in the management of welding processes, from the perspective of an ecological approach.
•Laser welding technology is effective for bonding of Al and Cu dissimilar metals.•Relationship between process parameters and joint properties are explored.•Controlling defects and improving joints ...quality methods are discussed.•Review for welding process, filler metals and process monitoring.
Dissimilar metal composite structures have been used in a wide range of applications to meet the requirements of lightness, corrosion resistance, electrical conductivity, and thermal conductivity due to their excellent overall performance. With the global energy conservation and emission reduction policies, dissimilar aluminium (Al) and copper (Cu) for lithium battery welding are more and more discussed. Laser welding is a unique technology for Al and Cu due to its high energy density, precise control, ease of automation, and remote welding. However, high reflectivity and differences in material properties result in poor laser absorption and an unstable welding process. Furthermore, sufficient mixing of Al and Cu during the welding process tends to form brittle intermetallic compounds (IMCs). This paper discusses the laser welding and the challenges faced by joining Al/Cu dissimilar metals, and analyzes the effect of different process parameters and laser output modes on the weld joint. Furthermore, the research progress on filler metals and process monitoring are discussed.
For the development of high-performance aluminum (Al) matrix composites reinforced with carbon nanotubes (CNTs), high energy ball milling (HEBM) is the most prevalent method to disperse CNTs in Al ...powder. However, the dispersion mechanism of CNTs in Al powder is still unclear, mainly because it is difficult to characterize CNTs when they are buried inside Al powder particles. Herein, focused-ion-beam-assisted transmission electron microscopy observation of CNTs in Al powder via HEBM with various milling times was conducted. Results showed that with increasing HEBM time, CNTs clusters were firstly broken up to be dispersed shorter-lengthed CNTs on the surface of Al flakes with gradually reduced thickness. Afterward, cold-welding of Al flakes was the predominant phenomenon, which resulted in re-spheroidization of Al powders and homogeneously dispersed CNTs. This study may provide guidance for controlling and optimizing the HEBM process to disperse CNTs in Al matrix towards the development of high-performance CNTs/Al composites.
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•CNT dispersion mechanism in Al matrix during ball milling process was elucidated.•Focused ion beam-assisted transmission electron microscopy observation was adopted.•Homogeneous CNT dispersion was obtained after 28 h ball milling process.•Dislocations and stacking faults in matrix enhanced powder modulus and hardness.
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