Butt Welding Research Articles

Multi-pass butt welding of thick TA5 titanium-alloy plates by MIG: Microstructure and properties

A 35 mm-thick TA5 titanium alloy plate was successfully joined by metal inert-gas (MIG) welding. The welded joints were analyzed in a more integrated and comprehensive manner. The joint microstructure was analyzed by OM, SEM, EBSD, and TEM. Mechanical properties were analyzed by tensile, impact, and microhardness tests. The corrosion resistance of the joints was determined by FeCl3 immersion corrosion. Experimental results showed that the mechanical properties and corrosion resistance of the fusion zone (FZ) were poorer than those of the base material (BM). The mechanical properties of the welded joints were related to the acicular grains in the FZ. The 260 A joints showed relatively good mechanical properties. With increased welding current, the proportion and size of the acicular grains increased, and the strength of the joint increased, but the plastic toughness decreased. When the welding current was too small, anisotropy occurred in the FZmiddle, which affected the mechanical properties of the joints. The corrosion resistance of the FZ was lower than that of the BM, and the corrosion resistance of the three groups of joints decreased in the order 300 A > 230 A > 260 A.The welding current affected the corrosion resistance of the FZ by influencing the grain size of the FZ, the frequency of the HAGBs, and the GND density.

Exploring the Potential Application of an Innovative Post-Weld Finishing Method in Butt-Welded Joints of Stainless Steels and Aluminum Alloys.

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.

Multi-response optimization of friction stir welding using fuzzy-grey system

Abstract This study reports that a fuzzy logic-based grey system using Taguchi’s method provides a reliable approach to the prediction of friction stir welding (FSW), which is capable of improving the multi-response performance of butt welds. Using the grey relational database, a fuzzy logic analysis is carried out. Analysis of variance is used to determine the effect of parameters of multi-response behaviors on butt welds. Meanwhile, multiple responses for multivariables are simultaneously optimized. The experimental results show that the fuzzy logic-based grey system using Taguchi’s design reveals the optimal settings of the parameters, which improves the whole properties by more than 28.04%, while the individual properties, such as tensile strength by 13.35%, bending strength by 1.91%, impact strength by 1.05%, and hardness by 0.26%, when compared with the best test in orthogonal arrays. Based on experimental validation tests, excellent agreement between model predictions and experimental results is shown. Notably, the intelligent method proposed is applied to butt welds, and the results of the implementation of fuzzy logic based grey system using Taguchi’s design proved its feasibility and effectiveness with respect to the improvement of the mechanical properties of FSW.

The influence of convexity on the strength of one-sided butt welds with lack of penetration

Using the SolidWorks Simulation program, the stress states of one-sided butt welded joints with a convex element and lack of penetration at the weld root are analyzed. It is established that the convexity of the weld increases the stress concentration caused by lack of penetration and increases the maximum stress in the joint. It is shown that for maximum unloading of the welded joint, it is necessary to completely remove the convexity of the weld seam and make a hole along the entire seam with a depth equal to the height of the lack of penetration. Keywords:analysis, stress state, lack of penetration, stress concentration, convexity, weld seam latun.tatsiana.0@gmail.com

Physical and Mechanical Properties of Butt Welded Joints of Aluminum Alloys

Along with the improvement of joining technologies with argon arc, plasma and laser welding for aluminum alloy elements, high efficiency of joints made with the use of friction stir welding (FSW), which has low energy consumption and is almost equally strong as base metal, has been achieved. However, the processes of friction stir welding have not been sufficiently studied and can lead to softening of aluminum alloy welds up to 0.65 of base metal strength. When studying the effect of friction stir welding and mechanized electric arc welding in argon medium, welded joints of aluminum alloys of Al-Si-Mg (AD35T1, 6082-T6) and Al-Zn-Mg alloying systems (1915T) were subjected to tensile and impact tests. The values of strength, elastic and plastic characteristics of argon arc welded specimens of 1915T, AD35T1 and 6082-T6 alloys were obtained. For alloy 6082-T6, the same characteristics are presented for FSW welded specimens. Decrease in strength and ductility in the zones of welded joints for both welding methods is observed. At the same time, the highest relative values of strength and offset yield strength of the welded joint are fixed for friction stir welding. Slight decrease in modulus of elasticity obtained for argon-arc welded specimens was recorded. The impact strength is constant for each welded joint zones in the temperature range of +20 – -60оC and increased in weld metal of FSW butt joints of alloy 6082-T6.

Features of Engineering Methods of Research Results on Butt Welding on Metal Pipelines

This article discusses the use of flash butt welding (FBW) for increased labor productivity in pipeline construction. However, despite its promise, FBW technologies and equipment have limitations in creating defectfree welded joints. The Ishikawa diagram is used to systematize and analyze factors that cause defects, which are then ranked on a Pareto diagram. The main causes of defects are found to be associated with human factors, such as the qualifications of workers, as well as imperfections in machinery and equipment, material deviations, and technology and measurement limitations. A correlation matrix is used to analyze the causes of the decrease in quality and determine that improving methods and means of FBW processes, along with FBW technologies, is the solution. However, a complete computer model of FBW processes has not yet been created due to difficulties in describing energy release and other energy phenomena. A physical and mathematical model is necessary to take into account energy processes in the welding zone.

Void nucleation and growth behavior of TIG welded AA2219 deformed at cryogenic temperatures

This work investigates the failure behaviour of tungsten inert gas (TIG) welded 2219 aluminum alloy butt welds deformed over a range of cryogenic temperatures relevant to liquid hydrogen/oxygen propellent storage tanks. A novel in situ tensile testing machine, able to deform samples at temperatures down to 83 K, was designed to be accommodated on synchrotron computed tomography beamlines. In this way we were able to observe the accumulation of damage from void nucleation through growth to coalescence and ultimate failure by time-lapse X-ray microtomography during tensile straining at 293 K and 123 K. The results reveal that micro-void nucleation is triggered by θ (Al2Cu) precipitates and α-Al + θ (Al2Cu) eutectics in the form of particle fracture and interface decohesion. After nucleation, these freshly nucleated voids, along with pre-existing welding defects, extend with straining along the loading direction. This leads to void linkage, a very short void coalescence stage and subsequent catastrophic failure. The probability distribution function that describes the rate at which voids nucleate by interface decohesion considering the particle orientation was determined through the Eshelby inclusion theory. The evolution of void aspect ratio and void growth were modelled using the Gurson-Tvergaard-Needleman model and Le Roy model, respectively. This suggests that pre-existing defects grow faster, but that the numerous closely spaced nucleated voids play a significant role in failure.

Data-driven carbon emission accounting for manufacturing systems based on meta-carbon-emission block

In the context of carbon neutrality and sustainable manufacturing, there is an urgent need for carbon emission accounting in the manufacturing industry, especially in high-energy, low-efficiency, and high-carbon emission manufacturing systems. However, the dynamics and coupling of carbon emissions caused by the multiple characteristics of manufacturing systems increase the challenges of carbon emission accounting. To this end, this research aims to develop a generic methodology to reveal the carbon emission characteristics and implement carbon emission accounting for manufacturing systems, so as to support the lean diagnosis and management of carbon emission hotspots. Firstly, the concept of the “meta-carbon-emission block” consisting of both static and variable carbon emission blocks is proposed to characterize the carbon emission behaviors of each device in various operating states. Then, a data-driven carbon emission accounting approach based on the meta-carbon-emission block is presented to calculate the carbon emission and diagnose the carbon emission hotspots. Finally, a typical manufacturing system, that is, a laser welding system for butt welding of aluminum alloy 6061 with multi-source of the carbon emission, multi-device of the processing system, multi-state of the sub-device, and multi-stage of the production, is conducted to validate the proposed approach, and the results revealed the effectiveness and practicality of this approach. This research provides an appropriate theoretical and methodological basis for carbon emission accounting of manufacturing systems and also supports the diagnosis and reduction of carbon emissions for manufacturing industries.

Cold butt welding of dissimilar aluminum alloys: Characterization and interface bonding conditions

Cold Butt Welding (CBW) exploits plastic deformation to enable room temperature fabrication of joints with comparable strength to their base metals. Challenges arise when CBW involves alloys with very different mechanical properties, where the necessary conditions to reach their plastic regime differ significantly. The present study unravels the conditions at the interface under which dissimilar AA1070 and AA6082 aluminum wires achieve bonding. Statistical studies were performed to establish a minimum deformation threshold required for successful bonding. The joints were characterized through optical light microscopy, scanning electron microscopy, and micro and nano hardness examinations. In-situ tensile testing was conducted to evaluate the bond strength and failure mechanism. It was found that during the CBW process, at increasing force, the constraints generated by the clamping apparatus on the wires are such that the soft alloy can exceed its ultimate strength and eventually reach the yielding stress of the hard alloy at the interface, allowing both materials to plastically deform and bonding to occur. Moreover, the deflection in the flow of both materials leads to grain refinement and crystalline reorientation inside a region centred around the bonded interface. The severely deformed area was proven by hardness and tensile testing to be the strongest part of the weld, typically identified as the mechanically affected zone.

The Influence of the Shielding-Gas Flow Rate on the Mechanical Properties of TIG-Welded Butt Joints of Commercially Pure Grade 1 Titanium.

This article proposes as a novelty the differentiation of shielding-gas flow rates from both sides of the tungsten inert gas (TIG)-welded butt joints of commercially pure (CP) grade 1 titanium tubes. Such an approach is aimed at economically reducing the amount of protective gas used in TIG closed butt welding. The effect of the shielding-gas flow rate on the properties of CP grade 1 titanium butt-welded joints made using the tungsten inert gas (TIG)-welding method. Butt-welded joints were made for different values of the shielding-gas flow from the side of the root of the weld. Argon 5.0 was used as the shielding gas in the welding process. As part of the research, the welded joints obtained were analysed using optical and scanning electron microscopy. The microstructural characteristics of the joints were examined using an optical microscope, and the mechanical properties were determined using hardness and tensile tests. It was observed that as the flow of the shielding gas decreases, the hardness of the weld material increases and its brittleness also increases. A similar trend related to the amount of gas flow was also noticeable for the tensile strength of the joints. The increase in the hardness of the weld and the heat-affected zone compared to the base metal is mainly related to the increase in the amount of acicular structure (α' phase). The optimal gas flow rates from the side of the root of weld were found at the values of 12 dm3/min.

Tool-pin profile effects on thermal and material flow in friction stir butt welding of AA2219-T87 plates: computational fluid dynamics model development and study

Tool-pin profile effects on thermal and material flow in friction stir butt welding of AA2219-T87 plates: computational fluid dynamics model development and study

Fatigue strength of single-sided fillet welds in overlapping ultra-high-strength steel sheets

From the manufacturing viewpoint, overlapping thin sheets can provide a substantial geometrical improvement in welded hollow sections compared to butt-welded cross-sectional details. However, the plate eccentricity and non-penetrating fillet welds make the joints susceptible to fatigue failures under transversal cyclic loads. This work experimentally investigates the fatigue strength of overlap joints prepared with gas metal arc welding in the single-sided fillet weld configuration. Fatigue tests were carried out on the lap joints made of S960 ultra-high-strength steel (UHSS) grade under uniaxial constant amplitude axial loading employing both pulsating tension (applied stress ratio of R ≈ 0) and pulsating compression (R ≈ -∞). In addition, the lap joints were prepared with both straight welds (the welds transverse to the loading direction) and inclined welds (the welds with a 30° inclement angle from the transversal direction) to investigate the shear stress effects on the joints’ fatigue performance. Plasma butt-welded samples were tested as a reference join type. For the plasma butt-welded joints, the recommended detail category of FAT71 in the nominal stress system for weld root failures in single-sided butt welds was observed clearly conservative—a mean fatigue strength of Δσc,50% = 130 MPa with a fixed slope parameter of m = 3 was obtained. Compared to the butt-welded joints, a significant decrease in fatigue strength capacity was found in the lap joint specimens with misalignment factors of km > 3.0. The failure locations were also different in joints subjected to the tension and compression loads. The shear load did not majorly contribute to the changes in the fatigue strength capacity compared to the joints subjected to the transversal normal stress.

Investigations on the influence of angular and linear misalignment on the fatigue strength of HFMI-treated structural steel butt joints

The effect of High-Frequency Mechanical Impact (HFMI) treatment on the fatigue resistance of structural steel S355 butt welds with macro geometric imperfections outside of the usual fatigue design limits was investigated. Thin-walled specimens (t = 8 mm) were manufactured with different degrees of angular and linear misalignment and fatigue tested in the as welded and HFMI treated condition. The fatigue test results show that HFMI treatment can compensate the fatigue strength-reducing effects of macro geometric imperfections (ΔσC,HFMI = 127 N/mm2, m = 5), but also that linear and angular misalignment does not reduce the fatigue strength of butt welds as severely as rules and guidelines suggest (ΔσC,AW = 107 N/mm2, m = 3). Underestimating the fatigue strength determined by testing by more than 40%, numerical analysis and strain gauge measurements show that the application of the effective notch stress approach and the structural hot-spot stress approach delivers conservative assessment results, which might not always be representative for the actual fatigue strength benefit that can be gained by HFMI treatment.

Influence of Deck Butt Weld Seams on Fatigue Life of Steel Bridge Decks Pavement: Parameter Optimization

Abstract The butt weld at the connection between orthotropic steel bridge decks (OSBDs) can potentially pose a hazard to the fatigue endurance of the steel bridge deck pavement. This study aims to optimize the parameters of the butt weld seam using finite element (FE) analysis. The optimized parameters will provide valuable guidance for the design of pavements with a focus on antifatigue properties. Initially, the dynamic modulus of the epoxy asphalt mixture (EAM) was determined through laboratory experimentation at various frequencies and temperatures. These material parameters were then used to compute the pavement’s fatigue life. Additionally, a well-established FE model was employed to analyze the deformation and fatigue life of the pavement structure. The validity of the model was verified by the theoretical calculation results. Various factors were considered, including vehicle velocities, pavement temperatures, and weld seam misalignments as well as weld seam dimensions such as height and width. The analysis was conducted using a three-dimensional steel bridge model. The results showed that decreasing pavement temperature, weld seam height, and misalignment led to an increase in pavement fatigue life. Conversely, reducing the weld seam width resulted in a decrease in fatigue life. Furthermore, the study investigated the coupling effect of different weld seam heights and widths on the fatigue life of the pavement. Contour figures were used to establish the parameter relationship formula for weld seam height and width. These findings are significant for pavement and deck designers because they enhance the understanding of the sensitivity of weld seams as design variables affecting the fatigue characteristics of pavement structures. Moreover, special attention should be given to the impact of welding parameters on the fatigue design of steel bridge deck pavement under high-temperature conditions of pavement structures.

Research on Magnetic Memory Detection of Weld Fatigue Damage Based on Two-Dimensional Spectral Entropy

Abstract In light of the intrinsic relationship between weld fatigue damage and the characteristics of magnetic leakage signals, fatigue experiments were conducted on butt welds to analyze the evolution of magnetic leakage signal as fatigue cycles increased. The introduction of two-dimensional spectral entropy allowed for the construction of a fatigue stage division model based on the two-dimensional spectral entropy diagram. The results revealed that distinctions between magnetic leakage signal under loaded and unloaded conditions were solely evident in their magnitude, with consistent curve distribution trends observed across various fatigue cycles. Furthermore, the distribution pattern of magnetic leakage signal displayed significant fluctuations, characterized by a sharp gradient increase following the emergence of fatigue cracks. These distribution characteristics of magnetic leakage signal differed markedly from the magnetic field distribution at other fatigue stages, with a higher growth rate observed as fatigue cycles increased. The two-dimensional spectral entropy spectrum analysis of magnetic leakage signals at different fatigue stages indicated the disorder in the magnetic leakage signal distribution within the high fatigue zone, signifying the expansion of fatigue microcracks. To some extent, two-dimensional spectral entropy can serve as an early warning system for detecting fatigue cracks in welds and achieving early identification of fatigue microcracks.

Evaluation of the fatigue resistance of butt-welded joints in towers of wind turbines — a comparison of experimental studies with small scale and component tests as well as numerical based approaches with local concepts

Wind turbines must endure a high number of load cycles during their service lifetime. Therefore, the fatigue strength verification plays an important role. Butt-welded joints are one of the most common structural details in the tower structure of wind turbines. In general, the nominal stress method is used for their fatigue verification. The Eurocode 3 part 1–9 is the current design standard for this field of application and defines the fatigue resistance by pre-defined FAT-classes. This paper presents recent results of fatigue tests on small-scaled specimens and large components with transverse butt welds to discuss the validity of the FAT-class. In addition, results from numerical simulations for the verification with the effective notch stress and the crack propagation approach are used for comparison. For this purpose, macroscopic measurements of the weld seam geometry and a 3D scan were used for a realistic consideration of the notch effect in the simulation. Based on the consistency between the numerical results and the fatigue tests, the influence of the seam geometry on the fatigue resistance was worked out. Furthermore, a prediction of the fatigue strength of butt-welded joints with plate thicknesses up to 80 mm was carried out.

A Study on Deformation due to Steel Constraint during Butt Welding and Line Heating of Thick-Plate in FLNG Topside Bearing Node

Products manufactured in shipyards are predominantly steel structures, primarily fabricated through welding. There are various welding methods, all of which commonly use very high heat. Therefore, during the fabrication of steel structures, thermal deformation caused by welding occurs, resulting in dimensional deviations from the initial design. Methods to ensure dimensional accuracy include optimizing the welding sequence, predicting thermal deformation before welding and applying reverse-setting, and suppressing thermal deformation through constraints. However, the most commonly used method in the field is heat straightening. This study proposes a method to control thermal deformation caused by welding by using steel constraints during welding and line heating. Analytical verification confirmed both the effect of heat straightening and the variance in effects when steel constraints were applied. As a result, it was confirmed that line heating is effective in correcting thermal deformation, and steel constraints can maximize the effect of line heating.

Mechanical properties and corrosion resistance study of dissimilar metal thin sheet friction stir welded joints

This study employs friction stir welding (FSW) technology to achieve the butt welding of 2mm thick 1060 aluminum and T2 copper. The research investigates the macroscopic formation, tensile properties, microhardness, and electrochemical corrosion behavior of the welded joints. The results indicate that the welded joints exhibit excellent formation, with a tensile strength reaching 84.76% of that of the 1060 aluminum material. Well-formed welded joints can be obtained by controlling the rotation speed and welding speed within a certain range. However, the rotation speed has a more significant impact on the microhardness in the weld zone. The corrosion potential of T2 copper is higher than that of 1060 aluminum, forming a macroscopic galvanic couple between the two materials. The corrosion potential of the welded joint falls between that of T2 copper and 1060 aluminum.

Yakma Alın Kaynağıyla Birleştirilmiş S355jr Yapı Çeliklerinde ITAB’ın Ansys ile Analizi

In this study, we focus on predicting the HAZ, which is a region whose mechanical properties are not clearly known, by modeling factors such as temperature input and heat turbulence, which may have different properties in the welding region. This is important for the safety of welded structures, because if the mechanical and thermal properties of these structures, which are used in many areas, can be determined in advance, they can be used more safely. In the study, flash butt welding method was preferred and holes were opened at regular intervals in the samples that were brought to appropriate dimensions for the welding process, and temperature values were measured and recorded using thermocouples and data loggers during the welding process. Additionally, the maximum temperature reached in the welding area was measured using a thermal camera during welding. Microstructural changes occurring in the joining regions of the welded test pieces were examined using light microscopy and scanning electron microscopy (SEM). Micro hardness measurements were made to determine mechanical properties. Using the ANSYS program, three-dimensional models were created using the finite element method under the same experimental conditions and compared with the experimental results. As a result of this comparison, it was seen that the findings were compatible with the actual results. For this reason, it is emphasized that the use of simulation programs is important to predict the properties of welded structures and possible problems.

Developing a visual prediction program for residual stress in girth butt welds using GA-RBF neural network

Developing a visual prediction program for residual stress in girth butt welds using GA-RBF neural network