Weld Material Research Articles

Influences of Weld Nugget Shape and Material Gradient on the Shear Strength of Resistance Spot‐Welded Joints

Resistance spot‐welded joints containing press‐hardened steels are seen to exhibit a fracture mode called total dome failure, where the weld nugget completely separates from one steel sheet along the weld nugget edge. The effect of weld nugget shape and material property gradients is studied based on damage mechanics modeling and experimental validation to shed light on the underlying influencing factors. For a three‐steel‐sheet spot‐welded joint combining DP600 (1.5 mm)–CR1900T (1.0 mm)–CR1900T (1.0 mm), experiments under shear loading reveal that fracture occurs in the DP600 sheet along the weld nugget edge. In subsequent numerical simulation studies with damage mechanics models whose parameters are independently calibrated for every involved material configuration, three variations of the geometrical joint configuration are considered—an approximation of the real joint, one variation with a steeper weld nugget shape, and one variation with a less pronounced gradient between weld nugget material and heat‐affected zone material properties. The results of the finite‐element simulations show that a shallower weld nugget and a more pronounced material gradient lead to a faster increase of plastic strain at the edge of the weld nugget and promote the occurrence of total dome failure.

Advancing Methodologies for Elemental Transfer Quantification in The Submerged Arc Welding Process: A Case Study of CaO-SiO2-MnO Flux

In submerged arc welding, evaluating elemental transfer behaviors is critical for selecting and designing welding materials. Accurate assessment of O, Si, and Mn transfer behavior is essential for ensuring process quality, particularly when silicon-manganese fluxes are applied. Traditional quantification methods, however, focus only on chemical reactions in the weld pool zone, potentially overlooking the cross-zone elemental transfer behavior and leading to significant predictive inaccuracies. This study investigates the CaO-SiO2-MnO flux, a prevalent silicon-manganese flux, focusing on O, Si, and Mn, which exhibit notable transfer behaviors of O, Si, and Mn. By employing a multi-zone approach and integrating various scientific principles, the research aims to improve the accuracy of predicting elemental transfer behaviors and deepen the understanding of the metallurgical processes in submerged arc welding when silicon-manganese fluxes are employed. The study proposes strategic enhancements to traditional quantification methods, which may offer valuable insights for the improvement of industry standards. This study demonstrates that considering only the local thermodynamic equilibrium of the weld pool zone when quantifying the transfer behavior of elements may lead to predictive errors, especially for easily evaporating metallic elements. By incorporating a cross-zone assessment for submerged arc welding process, i.e., introducing new quantifying parameters (Δd and Δw), the predictive accuracy of the transfer behavior of elements and their cross-zone actions can be enhanced.

Characterization of Fatigue Crack Growth Behaviour of Alloy 617M Base and Weld Material

Alloy 617M is a Ni-based super-alloy made in the form of tubes which are used in high-temperature boilers and super heaters in Advanced Ultra Super Critical (AUSC) power plants. The high-temperature oxidation and mechanical properties of this material have been derived based on chromium (Cr), cobalt (Co) and molybdenum (Mo) as prime alloying elements which cause solid solution strengthening, carbide precipitation (M23C6, M6C) and formation of intermetallic phase Ni3(Al, Ti) (γʹ-phase). The manufacturing route of these components involve bending and welding operations which are critical locations and potential sites for crack nucleation and growth. Also, the conjoint influence of high temperature and flow-induced vibrations in the tubes further aides to crack nucleation and growth. Thus, fatigue crack growth (FCG) properties are important. Therefore, in this work, detailed experimental studies on the FCG behaviour of Alloy 617M base and weld materials have been carried out at different test temperatures (27 °C, 650 °C, 710 °C and 750 °C). The effect of ageing (1000, 2000, 5000 and 20000 hours) at an operating temperature of 710 °C on FCG has also been evaluated. All the FCG tests have been conducted as per ASTM with a constant load ratio (R = 0.1) and frequency of 15 Hz. From the experimental results, a major trend is observed of decreasing threshold stress intensity factor (ΔKTH) with an increase in ageing time and test temperature. The variations in the ΔKTH with test temperature and ageing time have been discussed and the crack growth mechanism has been established through microstructure and fractographic studies validating from existing literatures.

Study of mechanical properties of RPV base and weld material using SPT technique

Small Punch Test (SPT) is one of the miniature test techniques used for evaluating tensile properties when limited dimension of material is available for standard mechanical test or handling of large specimen is difficult, especially while dealing with irradiated materials. In order to use SPT for determination of mechanical properties, it is crucial to establish correlation coefficients by comparing results obtained by SPT with that from standard tensile tests. Present work involves developing correlation coefficients and evaluation of tensile properties of reactor pressure vessel (RPV) steel using SPT technique. Specimen dimensions used for SPT was 10x10x0.5 mm3. These specimens were prepared from Charpy V-Notch specimens, which were earlier subjected to standard impact testing. Correlation coefficient for RPV material was established by comparison of SPT data with the tensile properties obtained using standard tensile test. Subsequently, SPT data was acquired on RPV thermal material and tensile properties were obtained using the correlation coefficient for validation. This paper describes the SPT set-up used during the current studies and methodology used for establishing the correlation coefficient on RPV base material.

Temporal power modulation in high power laser beam welding of round bars

Temporal power modulation bears an enormous potential for high power laser beam welding of round bars since all its specific challenges are faced. They can be summarised as deviating welding conditions towards the round bar‘s centre. Accordingly, a tailored amount of energy would be provided to that area. The investigations are conducted on 30 mm diameter bars of 1.4301 stainless steel with the use of a 16 kW disk laser. The modulation parameters comprise 6/12/50/100/200 Hz modulation frequency and 0.30/0.47/0.73 modulation depth or power modulation ratio. Post analysis focuses on metallographic longitudinal sections and calculations. The modulation‘s outstanding capability is creating deeper and narrower weld seams due to higher peak power and more intense evaporation of protrusions along the keyhole front wall. Therefore, more laser power is provided to the weld root and despite applying lower average power, the same weld depth is achieved. Finally, more ecological and economical welding as well as welding of more temperature sensitive materials is enabled.

Advancements in Friction Stir Welding: A Comprehensive Review of Process Variables and Emerging Developments

Friction stir welding (FSW) is a solid-state welding technique widely employed to join materials such as Aluminum (Al), Copper (Cu), Magnesium (Mg), and their respective alloys. These materials find extensive use in industries like transportation, where lightweight materials with superior mechanical properties are in demand due to their reduced mass. Conventional fusion welding methods can adversely affect the mechanical properties of these welds.Over the last two decades, FSW has emerged as a specific and significant advancement in welding technology. Various parameters, including shoulder diameter, shoulder profile, pin length, pin diameter, tool angle, rotating speed, feed rate, and weld speed, play crucial roles in determining weld strength, quality, heat generation, and material mixing.The current research focuses on investigating the process variables that influence the characteristics of welded products. Furthermore, it includes an in-depth exploration of FSW fundamentals, recent advancements, and comprehensive literature reviews.

New LTT Welding Material and All-Position Repair Welding with Elongated Bead for Super-Long Fatigue Life of Boxing Fillet Joints

New LTT Welding Material and All-Position Repair Welding with Elongated Bead for Super-Long Fatigue Life of Boxing Fillet Joints

Evaluation of weldability of nickel-base alloy weld materials with high chromium content

Evaluation of weldability of nickel-base alloy weld materials with high chromium content

Physio-Mechanical Properties and Microstructural Characteristics of Friction Stir Welded Aluminium and Copper Plates Using Conical Unthreaded Tool

Friction Stir Welding (FSW) is a type of welding used to join materials for high strength applications. FSW is a well-liked solid-state welding technique for joining aluminum alloys and other non-ferrous materials in the aerospace, automotive, and marine industries. Pure copper and aluminum from the 6082 series were welded together using a specially designed milling machine. Tests for hardness, flexural rigidity, and impact are performed to assess the welding strength. Material flow and weld defects have been investigated by analyzing the microstructure of the weld junction. The modified vertical milling machine has been used to execute FSW of pure copper and aluminum plates. The aim is to explore the produced welded joints and to comprehend the difficulties encountered while utilizing milling machines as a FSW equipment. Similarly, to optimize the welding parameters in order to accomplish sound welding. FSW can be carried out on a milling machine because the flexural strength of a conical unthread thread tool is 108.58N/mm2 and 92.16N/mm2, respectively, at rotational speeds of 500 rpm and 1000 rpm with welding feed rates of 16 mm/min and 50 mm/min.

Application of New Al-Si Welding Filler with High Concentration of Copper and Magnesium: High-Temperature Strength and Anti-Corrosion Mechanism.

Currently, the primary commercial aluminum alloy fillers used are 4043 and 5356. However, when welded with high-strength work pieces like 6061 and 7075 aluminum alloys, the strength of weld beads significantly lags behind that of the original welded material. Both 4043 and 5356 aluminum alloys cannot be strengthened through heat treatment. The strength difference between the weld bead and base material doubles after heat treatment. In this study, an Al-Si-Cu-Mg alloy (SCM) filler modified using a heat-treatable A319 aluminum alloy was employed to investigate the post-welding microstructural and mechanical properties of specimens under room- and high-temperature conditions and after prolonged exposure in a saltwater environment (3.5 wt.% NaCl). The aim was to demonstrate that commercial aluminum alloy fillers could be substituted with a high-silicon aluminum alloy boasting excellent solidification and mechanical properties. The results revealed that, after heat treatment of the weld bead, dendrites were not eliminated, but the tensile strength increased to 310 MPa, closely matching that of commercial 6061 aluminum alloy. The strength of the weld bead remained higher than 250 MPa in high-temperature (240 °C) and saltwater environments. These findings underscore the potential application of this material.

On the history of the construction of metal bridges in the 20th century using welding technology

The history of bridge construction is an important part of historical knowledge. Developments in bridge construction technology reflect not only engineering advances, but also social, economic and cultural aspects of society. Engineers and scientists faced unique challenges when designing and building bridges depending on the technological level of the era, available materials and the needs of society. This process may reflect technological progress, changes in transportation needs, and cultural and social changes. The purpose of this article is to briefly review key moments and stages in the history of metal bridge construction using welding technology in the 20th century. The history of the development of the construction of metal bridges using welding goes back a little over 100 years. The short period from the construction of the first welded bridges to their first disasters led to the need to analyze the possible causes of these destructions. As the analysis performed showed, catastrophic destruction most often occurred under the influence of several factors, as well as a combination of external adverse influences and the internal “unpreparedness” of the structure for them. The above examples indicate that an irrational choice of steel could be both an independent cause causing brittle failure of structures, and an aggravating factor in the presence of structural violations, thermal stresses and welding defects. Over the years, bridge manufacturing technologies have been improved in different countries, and new steels and materials for their welding have been developed. Thanks to the use of carbon, low-alloy and alloy steel, designers abandoned the brutal “railroad-type” beam trusses and today metal bridges with graceful and beautiful silhouettes powerfully stride across the water surface, mountains and valleys. They became real attractions of megacities and country landscapes, and builders were able to successfully solve numerous technical and economic problems. An important contribution to the development of global bridge construction using welding technologies was made by the team of the Institute of Electric Welding of the Academy of Sciences of the Ukrainian SSR under the leadership of Academician Evgeny Oskarovych Paton. The team of the Institute of Electric Welding of the Academy of Sciences of the Ukrainian SSR, introducing welding into bridge construction, carefully checked the results and monitored the behavior of structures. A new grade of steel was created that was resistant to the formation of brittle and fatigue cracks, its welding technology was developed, a technology for installation welding of vertical sheets with forced formation of a seam was developed, and suitable welding materials were selected. At the time of construction in 1953, the Kyiv Evgeny Paton Bridge across the Dnipro River was the largest all-welded bridge in Europe, all seams of which, including assembly ones, were made for the first time using automatic and semi-automatic welding. In addition, the presence of large similar blocks in the design of the Evgeny Paton Bridge made it possible to mechanize assembly and welding operations and organize an in-line method for their production at the factory and installation, which improved the quality of welding work and reduced its labor intensity.

Nanomechanical analysis of friction welded similar PEEK/aluminum nanocomposites: Effect of metal particle reinforcement

AbstractAluminum (Al), poly(etheretherketone) (PEEK) thermoplastics, and their individual composites have widely been used in many industries, including aerospace and biomedical fields. However, the joining process of those composites has not been explored much to date. In this context, the friction welding process (FWP) could be used as an alternative since it has the ability to join high‐strength components with minimal distortion. Therefore, the present study aimed to develop PEEK/Al nanocomposites with varying Al concentrations of 10, 20, 30, and 40 vol% using powder metallurgical technique and further joined the similar composition composites by FWP. Then, the effect of reinforced particle concentrations on the physical, morphological, structural, thermal, and micromechanical behaviors of the joined nanocomposites has been characterized by microscopy, X‐ray diffraction, differential scanning calorimetry, and nanoindentation tests. The concentrations of the reinforcement were found to have a significant effect on the crystallinity, melting temperature, glass transition temperature, and thereby micromechanical properties. The results were analyzed and correlated precisely for all the welded nanocomposites systematically. The interdiffusion mechanism was found to be involved in improving the mechanical properties of the present nanocomposites. The highest elastic modulus (13.91 GPa) or nanohardness (0.31 GPa) was obtained for the rotatory part of the PEEK/Al40 nanocomposites at 80 mN load. But, the applied load of 40 mN was the best loading condition due to the uniform change in modulus and nanohardness of all the nanocomposites. Therefore, the present alternative joining method of the PEEK/Al nanocomposites might be used for aerospace components.Highlights Development of PEEK/aluminum with 10, 20, 30 and 40 vol% Al nanocomposites. Friction welding of similar composite material, PEEK/Al‐PEEK/Al nanocomposites. Microstructural, thermal, and nanomechanical analyses. Effect of metal particle reinforcement on the friction welded nanocomposites. FW PEEK/Al40 nanocomposite is found to be the best.

Advanced process characterization and machine learning-based correlations between interdiffusion layer and expulsion in spot welding

Over the past decades, substantial endeavors have been dedicated to unraveling the intricacies inherent to Resistance Spot Welding (RSW). However, a comprehensive and consensual understanding of the RSW process physics is still lacking, including the exact number of physical phases behind the RSW process. For example, a widely accepted model indicates that metal only starts melting after the peak of dynamic resistance, while the latest research on welding uncoated materials challenges this by suggesting that melting begins around the resistance peak. Furthermore, most of existing physical models only consider welding materials without coatings in a controlled lab setting, whereas coated sheet metal is the norm in real production. Addressing these challenges, this paper introduces an enhanced model for RSW that considers the melting phase of the coating's InterDiffusion Layer (IDL) in Press Hardening Steels (PHS). This phase is believed to influence both welding quality and the occurrence of expulsions. Additionally, the timing at which each phase starts has been determined by analyzing real-time, multi-variable sensing data from various welding scenarios, and a signal processing technique has been devised to automatically identify when these phases begin. Leveraging this refined process understanding and characterization, meaningful explainable features are extracted, and a data-driven multilayer perceptron model is constructed for 1) predicting IDL thickness and 2) detecting expulsions upon predicted IDL thickness. The experimental results validate that the proposed IDL-inclusive model advances existing physical models for RSW and the IDL prediction improves the RSW defect detection and process monitoring.

Research on magnetic memory inspection signal characteristics of multi-parameter coupling pipeline welds

Magnetic memory inspection technology is an effective method for detecting early damage in ferromagnetic materials. However, the commonly used force-magnetic coupling models are insufficient for analyzing the distribution characteristics of magnetic signals in ferromagnetic material welds. This study first analyzes the influence of metal phase transformation and residual stress on the magnetic hysteresis characteristics of materials. Based on the principle of magnetic hysteresis characteristics, the magnetic charge density under the combined action of stress and phase transformation is determined, and a magnetic memory analysis model is established for multi-parameter coupling. The study quantitatively calculates the effects of phase transformation volume fraction, residual stress, the lift-off effect, and cracks on the magnetic signal features at welds. The research results show that the magnetic memory signals at welds exhibit extreme values in the tangential component and sinusoidal fluctuations with zero-crossings in the normal component. The peak-to-peak values of both the normal and tangential components of the magnetic signal increase with an increase in metal phase transformation and residual stress, while they decrease with the increase of the lift-off effect. When cracks appear in the weld, the normal component exhibits a double-peak and valley structure, with the inner side representing crack features and the outer side representing weld features. The tangential component shows a maximum value at the center of the crack. Based on the peak and valley values of the magnetic signal, a damage grade index F is determined. The damage index F can characterize the level of weld damage, decreasing approximately linearly with increasing stress.

Investigating seismic behaviour of cold-formed steel moment frames with the welded through-plate flexural connection

The Cold-Formed Steel (CFS) construction in seismic regions requires carefully selecting and designing an approved seismic-force resisting system. Among the available seismically-resistant structural systems, the bolted CFS moment frames have recently gained some attention. However, given the currently existing design issues associated with the bolted connections in CFS moment frames, this paper seeks to conduct a numerical investigation into the potential substitution of bolt fasteners with the weld materials in CFS frames. The objective is to explore the possibility of including the welded connection as an alternative to bolted connections in subsequent editions of the ASCE 7 code. To this end, finite element models, consisting of two built-up CFS beams and twenty-three flare-bevel-groove and fillet weld specimens, are initially validated against the cyclically and monotonically loaded tests with data available in the relevant literature. Subsequently, the verified weld and CFS beam models are incorporated in the simulation of thirty-four CFS beam-to-column welded moment connections, each differing in beam dimension, weld length and size, and gusset plate thickness. The built-up beams comprise back-to-back and lip-to-lip double C-section profiles. Stress variations along the weld lines, derived initially from nonlinear finite element analyses and then computed from the theoretical elastic analysis, are compared to establish a basis for categorizing stress distribution patterns in the longitudinal welds. Finally, six CFS frames assembled with the welded moment connection and subjected to a combined column axial compression and cyclic lateral drift are examined, resulting in an estimated seismic modification coefficient, R, equal to 3.8. Overall, the welded moment connections demonstrate a stable seismic response with an average ductility ratio, μ, of 2.7. The dominant failure mode is a locally developed ductile fracture in the two end segments of the longitudinal welds, identified as critical regions.

Влияние режимов дуговой автоматической сварки на геометрические параметры шва стыковых соединений из низкоуглеродистой стали, выполненных с применением экспериментального флюса

Introduction. The metallurgical industry in the territory of the Russian Federation has accumulated a significant amount of slags obtained during the smelting of steels and cast iron. The presence of slag dumps adversely affects the ecology of regions with metallurgical enterprises. When reducing iron from slags, the by-product becomes an oxide agglomerate, which can be considered as a flux composition for arc welding/surfacing under a layer of flux, fillers of powder wires, coatings of welding stick electrodes. The purpose of the work is to establish the possibility of arc welding using the flux obtained by the authors and to determine the optimal welding modes with the condition of achieving the geometric parameters of the seam according to GOST 8713-79 and the quality of the welded joint (absence of internal defects). In this paper, butt welded joints of sheet steel VSt3sp with a thickness of 5 mm obtained by automatic welding under a layer of flux at direct current with forced formation of a root roller on ceramic linings using flux from recycled metallurgical slag of an electric steelmaking enterprise are investigated. Automatic welding of flat specimens was carried out on a tractor-type ADF-1250 machine with a wire with a diameter of 3 mm, at a constant welding speed of 54 cm/min with varying current and arc voltage within 400–600 A and 27–37 V. The methods of investigation: Visual measuring and radiographic control, determination of deformation of specimens by laser scanning and computer processing of 3D models were used to evaluate the quality of welded joints. Statistical modeling in the form of a two-factor experiment was also used in the work, with obtaining adequate regression equations of the influence of welding modes on the geometric parameters of the seam: the height of reinforcement and the width of the seam on the front and back of the joint. Results and discussion. The possibility of obtaining welding fluxes from metallurgical slags of an electric steelmaking enterprise and its use for creating welded joints is shown. Optimal modes of arc welding of thin-walled sheet parts made of low-carbon steel with forced formation of a root roller on ceramic linings is established, ensuring the absence of internal defects in the form of pores, cracks and lacks of penetration, a minimum of residual deformations and compliance of the weld size with the requirements of the existing standard. The nominal values of the geometric parameters of the seam according to GOST 8713-79-C4 correspond to welding mode: welding speed 54 cm/min, welding current 550 A, arc voltage 30 V. The results of the work can be applied in metallurgical electric steelmaking enterprises producing low-carbon steel in the development of technologies for the use of welding materials from slag.

Elemental composition of particles formed during welding with stick electrodes

The elemental composition of welding fume (WF) respirable particles formed in carbon and low-alloy steels welding with stick electrodes with rutile (ANO-4) and the basic (UONI 13/45) type of coating was studied by X-ray-spectral electron-probe microanalysis. In the range from 0.25 to 16 µm aerodynamic diameter, all WF particles were divided into three groups according to their iron content: low (Fe≤20%), medium (20%<Fe<40%) and high (Fe≥40%). Each group contains various amounts of elements originating from the welding materials, which reflects their formation mechanism. Their relative abundance in WF depends on the particles aerodynamic diameter, type of electrode coating and the arc power. Particles with the medium iron content (agglomerates of nanosized primary particles) formed the largest group (over 70%) of respirable WF particles. For each electrode type, their average elemental composition does not depend on the size of the agglomerates. The low iron particles contain various combinations of electrode coating elements, and the variety of combinations increases with their aerodynamic diameter grows.These WF particles can be identified as aggregates of primary particles agglomerates and microspatters formed by disintegration of the electrode coating. WF particles with a high iron content are formed by aggregation of molten electrode metal microdroplets and nanosized primary particles agglomerates. They mainly contain iron (60–70%)and oxygen (15–35%). Their average elemental composition does not depend on the size of the aggregates, type of electrode coating and the arc power. The obtained results can be useful for the analysis and assessment of health risks for welders.

Study on the interfacial microstructure evolution of aluminum and CFRTP on FSLW joints: influence of pin length

Polymer/metal hybrid lightweight structures are increasingly employed in automotive, aerospace and electronics industries. Friction stir welding (FSW) is applied for the effective welding of metals and thermoplastic materials. For the welding of dissimilar materials, due to the significant property differences, it is hard to achieve high strength welded joints with smooth appearance. In this article, the influence of pin length is studied by experiments for the friction stir lap welding (FSLW) of Al alloy and carbon-fiber-reinforced thermoplastic (CFRTP). Tensile tests, OM, SEM and EBSD are carried out to evaluate the welding performance. Results indicate that the joint with smooth surface topography is obtained at the pin length of 2.5 mm with a peak temperature of 250.3 °C and the CFRTP matrix PEI thermal decomposition temperature residence time of 47.6 s. From OM and SEM micro analysis, the width of the bonding area is 3.02 mm and a thin uniform interaction layer is formed in the joint. EBSD confirms that the Al alloy in the stirring zone is refined after recrystallization. It is difficult to form a stacked layered structure in the bottom of joint, so the property of the joint is improved. The tensile strength is 32.9 MPa, which is 63.1% of CFRTP.

The influence of different alloyed welding materials on the microstructure and mechanical properties of welded interface in TiC cermet MIG welding bonds

The influence of different alloyed welding materials on the microstructure and mechanical properties of the weld interface in TiC cermet was investigated. MIG arc welding was employed to deposit low carbon steel, austenite stainless steel, and Ni-based filler wire onto the surface of the TiC-based cermet to create the weld interface. SEM, EBSD, XRD, microhardness, and shear testing were conducted for characterization. The results indicate that the joints have a (Heat Affect Zone)HAZ-(Partially Melted Zone)PMZ-UZ(Unmixed Zone) -WM(Welding Metal) structure. During the cooling process, the densely distributed TiC particles in the PMZ act as hard phases, leading to stress concentration and microcracks during solidification of the base metal, which affects the shear strength of the joints.

The characteristics extraction of weld seam in the laser welding of dissimilar materials by different image segmentation methods

The characteristics extraction of weld seam in the laser welding of dissimilar materials by different image segmentation methods