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Regulating the phase ratio between austenite and ferrite in welded joints is crucial for welding super duplex stainless steel. Nitrogen plays a significant role in maintaining an optimal phase ratio. In this study, the focusing gas channel of gas-focused plasma arc welding was utilized to introduce nitrogen into the arc plasma, which was then transferred to the weld pool. Experiments with and without nitrogen addition were designed and conducted to examine the effects of nitrogen on the microstructure and properties of SDSS 2507 weld joints. The results show that nitrogen addition increased the austenite content in the weld metal from 22.2% to 40.2%. Nitrogen also altered the microstructure of the austenite, changing it from thin grain boundary austenite and small intragranular austenite to a large volume of coarse, side-plate Widmanstätten austenite. The ferrite in the weld metal exhibited a preferred orientation during growth, while the austenite showed a disordered orientation. Additionally, the maximum texture intensity of the ferrite decreased with nitrogen addition. Nitrogen addition led to an increase in the microhardness of the austenite in the weld metal, attributed to the solid solution strengthening effect of nitrogen and increased dislocation tangling, while it decreased the microhardness of the ferrite. This study enhances the welding theory of 2507 super duplex stainless steel and guides the practical application of gas-focused plasma arc welding for 2507 super duplex stainless steel. [ABSTRACT FROM AUTHOR]

Laser welding was performed using different filler wires, ER70S steel, commercially pure iron, and pure nickel filler, in the context of welding X80 pipeline steel to assess the microstructure and mechanical properties of the weld metal. Introducing an ER70S wire promoted acicular ferrite formation in the fusion zone, compared to a bainitic microstructure in an autogenous laser weld. The use of pure iron wire was considered as a potential strategy for reducing hardenability, as it led to the dilution of alloying elements in the fusion zone, increasing ferrite content and reducing weld metal hardness to a level compliant with API pipeline standards. The addition of pure nickel wire was used to reveal the degree of weld metal mixing imposed by the laser (thus providing an unambiguous tracer element) when it is combined with filler material dilution in the fusion zone, revealing that the upper region contained 38% wire material and the lower region only 12%. This accounts for the differences observed between the upper versus lower portions of the weld metal when other wires are used, and the use of hardness mapping and micro-indentation demonstrates the correlation between the variations in mechanical properties and microstructural differences introduced by incomplete mixing of the filler wire elements. [ABSTRACT FROM AUTHOR]

Additive manufacturing encompasses technologies that produce three-dimensional computer-aided design (CAD) models through a layer-by-layer production process. Compared to traditional manufacturing methods, additive manufacturing technologies offer significant advantages in producing intricate components with minimal energy consumption, reduced raw material waste, and shortened production timelines. AM methods based on shielded gas welding have recently piqued the interest of researchers due to their high efficiency and cost-effectiveness in manufacturing critical components. However, one of the most formidable challenges in additive manufacturing methods based on shielded gas welding lies in the irregularity of weld bead height at different points, compromising the precision of components produced using these techniques. In this current research, we aimed to achieve uniform weld heights along the welding path by considering the most influential parameters on weld bead geometry and conducting experimental tests. Input parameters of the process, including nozzle angle, welding speed, wire speed, and voltage, were considered. Simultaneously, image processing and wavelet transform were employed to assess the uniformity of weld bead height. These parameters were applied to produce intricate parts after identifying optimal parameters that yielded the smoothest weld lines. According to the results, the appropriate bead for manufacturing the part was extracted. The results show that the smoothest bead line is achieved in 27 V as the highest level of voltage, at a 90° nozzle position and the maximum wire feed rate. Parts manufactured using this method across different layers exhibited no distortions, and the repeatability of production substantiated the high reliability of this approach for component manufacturing. [ABSTRACT FROM AUTHOR]

As a result of the thermo-mechanical impact during welding, distortions are generated in welded structures. These distortions significantly influence the geometric and dimensional accuracy of welded structures, in many cases lowering their working characteristics and reliability. An optimal design for welded structures is a prerequisite for increased reliability and reduction in manufacturing cost, and such an optimal design can be achieved knowing the distortions in weldments. Despite the fact that pulsed metal inert gas welding and metal active gas welding have been broadly applied in the last few decades, nowadays, few manufacturers, for instance, Fronius, EWM, Redco, and Perfect Power Welders, offer such an option for manual arc welding. This work aims to determine the influence of the parameters of pulsed welding modes on distortions that are generated during manual arc welding. Two different inverter welding power sources were used, and the welding distortions were measured by 3D scanning. The results showed that the pulsed mode during manual arc welding led to a reduction in distortions compared to the conventional welding mode. The crucial part of the manual welding system proved to be the qualification and performance of the welder. [ABSTRACT FROM AUTHOR]

Titanium and titanium alloys with a medium thickness of 5 to 12 mm are widely used for ocean platforms, military equipment and in other fields because of their light weight, appropriate strength and corrosion resistance. In this study, autogenous laser welding and narrow-gap laser welding processes were researched and compared, and the welding characteristics, weld microstructure and joint strength were analyzed. The results showed that autogenous laser welding had higher efficiency, narrower weld width and higher microstructure uniformity. Autogenous laser welding can achieve the single pass weld penetration at laser keyhole mode. The weld width of narrow-gap laser welded joint was 12.5 mm, which was nearly three times than that of autogenous laser welding. The grain size of autogenous laser welding was obviously smaller and more uniform in depth than that of narrow-gap laser welding. In the weld zone, the coarse columnar α grains grew from the fusion line, while in the heat-affected zone, equiaxed α grains with needle and sawtooth α morphologies were presented. The microhardness of the heat-affected zone was higher than in the weld zone and the base metal due to the denser needle microstructure. The tensile samples all fractured at the base metal, indicating the welded joint strength efficiency was greater than 1. [ABSTRACT FROM AUTHOR]

The tungsten inert gas (TIG) welding process is widely used in various industries for its ability to produce high-quality welds at a low cost. However, TIG welding struggles with welding thick stainless steel in a single pass, reducing production efficiency. To address this, new TIG variants such as activated TIG (A-TIG), flux bound TIG (FB-TIG), and flux zone TIG (FZ-TIG) have been developed to enhance penetration in austenitic stainless steel. This study investigates the effects of TiO2 and Fe2O3 flux on 304 stainless steels welded using A-TIG, FB-TIG, and FZ-TIG processes. Results show a slight increase in the depth-to-width (d/w) ratio for A-TIG and FB-TIG, while FZ-TIG achieved a 59% higher d/w ratio compared to autogenous TIG welding. The increased penetration is attributed to the reversal Marangoni convection and arc constriction. Microstructural analysis reveals a higher delta ferrite content in A-TIG and FZ-TIG welds due to increased heat input. Additionally, FZ-TIG welds exhibited an 11.5% higher microhardness compared to autogenous TIG welds. FZ-TIG welding enhances penetration and mechanical properties effectively. [ABSTRACT FROM AUTHOR]

Copyright of Metal Working (1674-165X) is the property of Metal Working Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The widespread adoption of arc additive manufacturing techniques across various industries has advanced the field of SS316L stainless steel manufacturing. It is crucial to acknowledge that different welding modes exert distinct influences on the forming and mechanical performance. This study analyzed the thermal input associated with four specific welding modes in LORCH MIG welding, clarifying the transition dynamics of molten droplets through waveform analysis and examining the resultant effects on microstructure and performance characteristics. The Pulse, Speed-Pulse-XT, and Twin-Pulse modes were found to induce spatter during the manufacturing process, consequently reducing molding efficiency in comparison to the SA-XT mode. Notably, the Twin-Pulse mode, characterized by double-pulse agitation, generated fish scale patterns along the lateral surfaces of the fabricated parts, promoting anisotropic grain growth. This microstructural refinement, compared to single-pulse samples with equivalent thermal input, resulted in enhanced mechanical properties. Nevertheless, the horizontal tensile strength of the three pulse modes was lower than the industrial standard for SA-XT mode and forging. In contrast, the SA-XT mode with an average hardness of 168.1 ± 6.9 HV and a tensile strength of 443.58 ± 5.7 MPa. Therefore, while three pulse modes offer certain microstructural advantages, the SA-XT mode demonstrates superior overall performance. [ABSTRACT FROM AUTHOR]

This study aims to clarify the effect of oxygen in shielding gas on weldability in the plasma-GMA (Gas Metal Arc) hybrid welding process of high-tensile strength steel plates. The difference in keyhole profile and bead formation, when the GMA shielding gas was pure Ar, Ar + 2% O2, or Ar + 20% CO2, was investigated for plate thicknesses of 6 and 9 mm for the first time. It was found that the weld beads were in good condition for 6 mm thickness plates for all shielding gases, which implied that the window of welding conditions for this thickness is wide. In contrast, for 9 mm thickness plates, a fully penetrated weld bead was achieved only in Ar + 20% CO2, and weld bead penetration in Ar + 20% CO2 is higher than in pure Ar and Ar + 2% O2 in the same welding condition. Due to decreased surface tension caused by sufficiently increased oxygen absorbed into the weld pool, the keyhole diameter increased to penetrate the bottom side of the plate, and the depressing weld pool surface under GMA allowed the heat input from the GMA to be directly applied to a deeper position. Consequently, the plasma-GMA hybrid welding process with Ar + 20% CO2 achieved a complete penetration for a plate of 9 mm thickness, owing to the effects of both phenomena. It proved a potential to increase penetrability in welding thicker plates by controlling oxygen content in shielding gas of GMA adequately. [ABSTRACT FROM AUTHOR]

The Plasma Electrolytic Oxidation (PEO) process was investigated to enhance the adhesion of AA2024-O aluminum alloy with a polyetherimide (PEI) matrix composite, using oxy-fuel welding (OFW). A Central Composite Design (CCD) statistical model was used to optimize three independent parameters in PEO: immersion time (s), duty cycle (%), and electrolyte concentration (Na2B4O7·10H2O), aiming to achieve a maximum value of shear strength of the hybrid joint (in MPa). The hybrid joint without PEO treatment presented a resistance of 2.2 MPa while the best condition presented a resistance of 9.5 MPa, resulting in a value 4× higher than the untreated material, due to the characteristics of the coating, which presented a more hydrophilic surface, allowing better mechanical interlocking with the polymer matrix and resulting in mixed-mode failure (adhesive, cohesive, and light fiber). In addition to improving adhesion, the PEO treatment provided better corrosion resistance to the alloy, forming an inert aluminum oxide (Al2O3) coating, with an improvement of approximately 99.84% compared to the untreated alloy. The statistical design covers about 77.15% of the total variability of the PEO + welding process, with independent factors influencing around 48.4% of the variability. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of this research is to investigate the impact of a flux containing 80% TiO2 and 20% CeO2, under protective atmosphere (100% Ar, 98% Ar-2% N2, and 95% Ar + 5% N2) on penetration depth, phase equilibrium, and corrosion behaviour of autogenous A-TIG welds generated at constant current density. The reason for choosing cerium in the flux composition and nitrogen in the shielding gas is their effect on the phase balance of austenite and ferrite in this alloy. Metallography, ferritoscopy, and potentiometry were employed in the examination of the welds. The use of a two-component flux increased the penetration depth in TIG welding by up to 87%. Adding 2% and 5% nitrogen gas to the shielding gas in active TIG welding further increased the penetration depth to 117% and 130%, respectively. The results of ferritoscopic analysis reported the amount of austenite in the base metal and conventional TIG weld as 48% and 32%, respectively. However, the use of two-component flux increased the amount of austenite in the weld metal to 39%. Additionally, the addition of 2% and 5% nitrogen to the shielding gas in active TIG welding increased the amount of austenite in the weld metals to 60% and 76.6%, respectively. According to cyclic potentiodynamic polarization studies, active TIG welding with different nitrogen gas concentrations showed improved general and pitting corrosion properties in weld metals compared to conventional TIG welding. Consequently, weld metal resulting from active TIG welding with 2% nitrogen gas exhibited corrosion properties almost identical to that of the base metal. [ABSTRACT FROM AUTHOR]

For the sake of realizing the safety detection of natural gas and petroleum pipeline welds, this paper designs a ferromagnetic pipeline weld magnetic flux leakage detector based on the calculation of the magnetic circuit of the detection probe, with the magnetization direction perpendicular to the traveling direction. The traditional pipeline magnetic flux leakage detection device uses a detection system mode in which the magnetization direction is parallel to the direction of travel. However, due to the structural characteristics of the weld, the traditional detection system mode is not applicable. Since the weld magnetic flux leakage detector needs to travel along the direction of the weld, the detector designed in this paper rotates the magnetizer 90 degrees along the direction of the weld seam so that the magnetization direction is perpendicular to the direction of travel, breaking through the technical barrier that make traditional magnetic flux leakage detection devices unsuitable for weld detection. The detection device includes a magnetizing structure, a data sampling device, and a driving and traveling device. The magnetic flux leakage signal collected by the detector is converted into a digital image in the form of a grayscale matrix. Using mathematical morphology and chain code algorithms in image processing technology, a pipeline weld defect inversion software system is developed, and a preliminary quantitative analysis of pipeline weld defects is achieved. The application of this technology enables the inspection and protection of oil and gas pipeline welds throughout their life cycle, broadens the scope of existing inspection objects, and is of great safety significance for ensuring national public security. [ABSTRACT FROM AUTHOR]

Welding techniques are widely utilized for permanent material joining. The tungsten inert gas (TIG) welding process is notable for its exceptional precision, controlled heat input, and affordable equipment. It is widely employed for joining different grades of steel. Currently, extensive research is being conducted to enhance the quality of welded joints. This involves exploring various welding methods and adjusting welding parameters to improve characteristics such as strength, ductility, formability, appearance, and corrosion resistance. The current investigation's main aim consists of studying the effect of the welding parameters, i.e., the welding current and the gas flow rate, on the mechanical properties of welded joints of low-carbon steel with a thickness of 1 mm. The yield strength, tensile strength, and strain at break are selected as responses. The analysis of variance (ANOVA) is utilized to check the impact of welding parameters on the responses, while the Gray Relational Analysis (GRA) is used to optimize the welding parameters to maximize the chosen responses. Results show that welding current possesses the most influence on the three responses, i.e., the yield strength, tensile strength, and strain at break. The combination of 65 A welding current and 15 l/min gas flow rate allows the maximization of the three responses. [ABSTRACT FROM AUTHOR]

Shielding gases had considerable significance in welding metal protection from contamination during welding. Welding protection gas is essential in welding joint quality, connected to the arc characteristics and weldment microstructure. Understanding the influence of welding shielding gas in different metal welding processes is extremely important, and many research papers and experiments have been performed. The current study objective is to analyse and summarize shielding gas variations' effects on welding joint bead geometry, dilution percentage, joint soundness, and microstructure by examining the impacts of different protection gas combinations on AISI 304 stainless steel MIG welding. Three AISI 304 weldment samples were welded with MIG technology and 308L filler wire, and three different gas mixtures as protection gas; the dilution percentage for every sample was calculated to evaluate gas mixture influence on heat concentration on welding zone geometry calculation--ferrite percentage and calculated to estimate and predicate the final welding microstructure and texture. An optical microscope and SEM were employed to reveal weldment microstructure, welding porosity, and defects and study their impact on mechanical properties. Vickers microhardness and tensile tests were done to record gas mixture effects on welding zone hardness and strength. Variation in gas mixture effects on weldments' corrosion resistance was recorded using a corrosion test on every welding sample. These research results can be used as guidelines to achieve the required welding quality in practical welding and provide an excellent foundation for understanding and solving shielding gas issues in the metal welding industry and evaluating welding protection gas mixtures' productivity and quality. The heat input of the three samples is equal due to the use of the same voltage, current, and travel speed; for that, we need to profoundly analyse the weldments microstructure and analyse the impacts of variation in microstructure, which resulted from protection gas mixture effects on the cooling rate on weldments mechanical properties. It fits with the requirements of design criteria. [ABSTRACT FROM AUTHOR]

Damage to pipeline welds during service can result in substantial human and economic losses. Hence, early and accurate quality diagnosis of in-service natural gas pipeline welds is of utmost importance. However, the current diagnostic methods are plagued by low accuracy and excessive resource consumption. Therefore, a fusion model for diagnosing the quality of in-service natural gas pipeline welds is constructed based on gradient boosting decision tree (GBDT), k-nearest neighbor (KNN), and random forest classifier (RFC). Initially, heterogeneous raw data sets undergo data cleaning and quality enhancement processes. Subsequently, the predictions from GBDT, KNN, and RFC are fused using voting as the fusion strategy. The processed data set is then utilized to train and test the fusion model (MIX). After verifying the reliability of the model through cross-validation, the performance of the model's prediction results is assessed, and a comprehensive analysis of the model's characteristics is conducted by combining theory and empirical evidence. By analyzing the experimental results, the fusion model performed better than the single model, with an accuracy rate of 96%. It can effectively diagnose the quality of natural gas pipeline welds in service, providing a new reference for existing diagnostic methods. Practical Applications: The fusion modeling method proposed in this study can be applied to the diagnosis of welding quality of in-service natural gas pipelines in order to solve the problem of early quality diagnosis of natural gas pipelines and improve the diagnosis of welding quality. The method can effectively overcome the problem of small size and poor quality of engineering data sets. First, the original data set is cleaned and downscaled, and then the synthetic minority oversampling technique (SMOTE) combined with edited nearest neighborhood (ENN) (i.e., SMOTEENN) is balanced to improve the quality of the data set. Then, the data set is predicted by three models, and the three predictions are fused using a voting fusion strategy to effectively improve the diagnostic ability of the models. Finally, the importance of the output features of the fused models is utilized for empirical and theoretical information mining. The experimental results show that the diagnostic accuracy of the method can reach 96% with high reliability and stability, which can provide technical support and theoretical basis for the diagnosis of the welding quality of in-service natural gas pipelines. Mining feature information can also provide more reference information for the pipeline welding construction stage, improve the initial welding quality, and reduce welding defects. [ABSTRACT FROM AUTHOR]

The effective welding of a 6 mm thick TA2 pure titanium medium-thickness plate was achieved by laser–arc hybrid welding (LAHW) with helium–argon mixed shielding gas. Conducted research on the influence of helium–argon mixed shielding gas on plasma and arc characteristics during welding, and its further impact on the microstructure, internal porosity defects, tensile properties, and corrosion resistance of welded joints was explored. The study demonstrated that under the shielding gas with 75% helium, the arc width narrowed significantly from 6.96 mm to 2.61 mm, achieving a 63% reduction, which enhanced the concentration of arc heat flux density. Achieved a well-formed weld with no surface spatter and significantly reduced the internal porosity rate from 3.02% to 0.47%, which is an 84% decrease. Tensile fractures are located in the base material, all exhibiting plastic failure. The corrosion resistance of the welded joint initially increased and then decreased with the increase of helium content in the shielding gas, peaking at 75% helium content. [ABSTRACT FROM AUTHOR]

Fusion-based joining techniques such as TIG and Laser are used for the high-quality Nitinol welds. The joining of Nitinol is challenging due to the formation of intermetallic, which results in the loss of Superelastic and Shape Memory Effect behavior. The optimum heat input is necessary to produce high-quality welds especially in thin sheet joining. Autogenous TIG welding with optimum heat input creates the satisfactory Nitinol weld joints consisting narrower heat-affected zones, and prevents the extensive precipitate formation in weld region. In the paper, autogenous TIG and Laser Beam welding were used for the welding of Nitinol superelastic sheet. The SEM fractography and microhardness were studied to understand the weld zone behavior of Nitinol welds. The Deep Hole Drilling technique was implemented to quantify the residual stresses in TIG and Laser Nitinol welds. The weld longitudinal residual stresses are found to be higher than the transverse residual stresses in both, TIG and Laser welds. In the base material, the compressive residual stresses were present up to near yield strength of material. [ABSTRACT FROM AUTHOR]

Plume are common physical phenomena in fiber laser keyhole welding and have serious negative effects on the welding process. Based on this, this paper explores the regulation law of conventional shielding gas flow on plume. The results show that the shielding gas has a very significant effect on the suppression of the slender part of the plume, and the greater the gas flow rate, the better the plume removal effect. The addition of the shielding gas makes the welding process more stable, the molten pool flows stably, and the frequency of spatter eruption is reduced. Under the experimental conditions, the optimal shielding gas flow rate is around 15 l/min, and the penetration depth and width are increased by about 10% and decreased by about 22%, respectively, compared with that without adding the shielding gas. Based on the gas flow simulation, the gas flow pressure (about 132 Pa) generated by an appropriate amount of shielding gas (about 15 l/min) can press the liquid column and spatter near the keyhole mouth into the molten pool to avoid the spatter eruption. Excessive shielding gas flow will interfere with the flow of the molten pool excessively, and the weld surface will show a serious undercut phenomenon. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyze the effect of the HFMI (high-frequency mechanical impact) treatment of each weld bead on the properties of a butt joint with a ceramic backing welded by robotic method 135 (MAG—metal active gas welding method) and to determine the effect of HMFI on the stress level. This analysis was based on a comparison of three butt joints made of a S690QL plate, in the as-welded condition, with the HFMI of each bead and with the heat treatment carried out with PWHT stress relief annealing. The high-frequency (90 Hz) peening of each weld bead was linked with a stress reduction in the weld via the implementation of compressive stresses into the joint. The HFMI pneumatic hammer was used for this. The correctness of treatment was achieved when 100% of the surface of each bead including the face was treated. As part of the post-welding tests, basic tests were carried out based on the standards for the qualification of welding technology, and as a supplementary test, a stress state analysis using the Barkhausen effect was carried out. The tests carried out showed that the use of high-frequency peening after each pass did not affect the negative results of all the required tests when qualifying the welding technology of S690QL sheet metal compared to the test plates in the as-welded condition and after heat treatment—stress relief annealing. Inter-pass peening of the welded face and HAZ (heat-affected zone) resulted in a reduction in post-weld residual stresses at a distance of 12 mm from the joint axis compared to the stress measurement result for the sample in the as-welded condition. This allowed for a positive assessment of peening in the context of reducing the notch, which is the concentration of tensile stresses in the area of the fusion line and HAZ. The tests carried out showed that the peening process does not reduce the strength properties of welded joints, and the results obtained allow the technology to be qualified based on applicable standards. [ABSTRACT FROM AUTHOR]

Tungsten Inert Gas (TIG) is a welding technique that stands out due to its high precision, controlled heat input, and equipment's cost-effectiveness. TIG welding is utilized to join various grades of steel. Presently, numerous research studies are actively seeking to improve the quality of welded joints, focusing on aspects such as strength, ductility, formability, appearance, and corrosion resistance. These improvements are achieved through the modification of welding methods and/or welding parameters. In this investigation, welding current and gas flow rate were selected as input parameters. Additionally, PWHT at 700 °C for 1.5h was applied to relieve the residual stresses occurring during the welding operation. The objective of this investigation is to examine how the welding current, gas flow rate, and post-weld heat treatment (PWHT) affect the bending properties of welded joints. The bending test was conducted to assess both the bending resistance and bending strain of the joints. The bending resistance increases to attend a maximal value of 790 N and the bending strain decreases to 7.1%, with the welding current and the gas flow rate due to the high heat input and cooling rate. The applied PWHT decreases the bending resistance by 11% and increases the bending strain by 18%, due to the decrease of the joint's hardness. [ABSTRACT FROM AUTHOR]

The cross section of the laser-melt inert gas welding (MIG) hybrid welding joint can be divided into two different heat source regions, the upper is the laser-MIG hybrid heat source region, and the lower is the laser heat source region. In this paper, the laser-MIG hybrid welding experiments were carried out on a new nickel-based alloy 4716MA0. The type, morphology and distribution characteristics of porosity in different heat source regions were researched by optical microscopy, scanning electron microscopy and energy-dispersive spectroscopy. In addition, the formation mechanism of different types of stomata was explained by the model diagram. It is found that the dominant region of the laser-MIG hybrid heat source is dominated by metallurgical porosity, which is attributed to the formation of CO gas, whereas the dominant area of the laser heat source is dominated by process porosity. The generation of process porosity is attributed to the instability of the keyhole. [ABSTRACT FROM AUTHOR]

Currently, the strength of hot-press-forming steel has been increased to produce lightweight vehicles, and in this study, the first arc welding investigation on a 2.0 GPa-strength hot-press-forming steel was conducted. Hot-press-forming steel sheets with thicknesses of 1.1 mm were butt-welded by gas tungsten arc welding without a filler metal, with the heat input controlled in the range of 140-260 J/mm. The weld metal, coarse-grained heat-affected zone (HAZ), and fine-grained HAZ had martensitic microstructures. The softened zone was composed of an intercritical HAZ (with polygonal ferrite and martensite/bainite) and a subcritical HAZ (with tempered martensite). The intercritical HAZ was softened the most during welding and fractured during tensile testing. The strengths of the arc welds were in the range of 1141-1264 MPa, which were 57-63% strength of the base metal. The equiaxed austenite on martensite or ferrite matrix was developed at the intercritical HAZ of gas tungsten arc welds, therefore transforming into the coarse martensite during quenching. However, the intercritical HAZ of laser welds indicated acicular austenite transforming into the fine martensite due to its high cooling rate. The intercritical HAZ softening was revealed to originate from carbon diffusion during the martensite to austenite transformation, which is unavoidable in arc welding and should be considered in the design of a welded structure. [ABSTRACT FROM AUTHOR]

Purpose: The criteria importance through intercriteria correlation (CRITIC) and range of value (ROV) combined methods were used to determine a single index for all multiple responses. Design/methodology/approach: This paper used cold metal transfer (CMT) and pulse metal-inert gas (MIG) welding processes to study the weld-on-bead geometry of AA2099-T86 alloy. This study used Taguchi's approach to find the optimal setting of the input welding parameters. The welding current, welding speed and contact-tip-to workpiece distance were the input welding parameters for finding the output responses, i.e. weld penetration, dilution and heat input. The L9 orthogonal array of Taguchi's approach was used to find out the optimal setting of the input parameters. Findings: The optimal input welding parameters were determined with combined output responses. The predicted optimum welding input parameters were validated through confirmation tests. Analysis of variance showed that welding speed is the most influential factor in determining the weld bead geometry of the CMT and pulse MIG welding techniques. Originality/value: The heat input and weld bead geometry are compared in both welding processes. The CMT welding samples show superior defect-free weld beads than pulse MIG welding due to lesser heat input and lesser dilution. [ABSTRACT FROM AUTHOR]

This study investigates the relationship between the microstructure and the mechanical properties and the residual stresses of thermomechanically rolled, butt‐welded S1100MC ultra high‐strength steel plates. Matching metal‐cored filler wires are used for metal active gas welding of the plates in horizontal and vertical‐up positions. The effect of the heat input on the microstructures of both the weld metal (WM) and the heat‐affected zone (HAZ) is studied in detail. The microstructure of the WM consists of different types of ferrite, but the microstructure of the HAZ predominantly consists of fresh martensite at the top and bottom areas. Structure and size of the prior austenite grain boundaries are dependent on the welding positions and affect the impact toughness of the welds. HAZ of the weld produced in vertical‐up position is under intensive tensile residual stresses next to the fusion line. Even with matching filler wires, the strength of the welds is insufficient, and fracture of the weld metal occurs because the extended cooling time leads to the formation of acicular ferrite instead of martensite. [ABSTRACT FROM AUTHOR]

Studies on dissimilar materials joining have greatly increased, transitioning from temporary to permanent joining methods. The latter approach is more applicable due to the hybrid structure offering the best properties of the constituent materials, along with the development of new materials and manufacturing procedures. In this study, the AA2024-T3 alloy was treated with plasma electrolytic oxidation (PEO) and a thermoplastic composite/AA2024-T3 hybrid joint was manufactured using oxy-fuel welding (OFW). Morphological aspects, chemical compositions electrochemical and mechanical properties of hybrid composite joints were determined. The results indicated that the joint exhibits a uniform structure. The adhesion between the dissimilar materials reached a strength of 4.2 to 5.2 MPa, with cohesive bonding and without severe degradation of the thermoplastic matrix in some cases. It was observed that PEO treatment decreased the interface shear strength due to the high silicon content presence in the coating. The coatings effectively increased nobility and corrosion resistance, with corrosion rates ranging from 0.0087 to 0.018 mm/year. [ABSTRACT FROM AUTHOR]

The influence of the conditions of nonconsumable (TIG) and consumable (MIG) electrode arc welding of high-strength aluminium alloy of 2219-Т31 grade (USA) 5 mm thick was studied. Effective welding modes were selected by the main characteristics: absence of coarse defects, weld form factor, standard mechanical properties, and features of fracture surface relief. The strength level of welded joints after welding is 25‒30 % lower compared to base metal (σt = 366‒370 MPa). The impact toughness values of the welds after TIG welding vary from 16.4 to 20.3 J/cm², according to the rolling direction. Bend angle is almost 3 times lower than the base metal value (180 and 177°). Fracture of joints with technological reinforcement and of the weld root occurs along the boundary of weld fusion with the base metal, and at a distance from the surface — along the weld axis. The relief retains a predominantly cellular structure. Analysis results were used to establish the technological conditions of achieving an optimal quality of welds and the type of shielding gas for welding. [ABSTRACT FROM AUTHOR]

An experiment was conducted on the laser-metal inert gas hybrid welding of 7075 aluminum alloy under alternating magnetic field assistance, in order to investigate the effect of the magnetic field on weld porosity defects in aluminum alloy. The internal porosity of the weld seam under different magnetic field conditions was compared and analyzed through radiographic inspection. The impact of the alternating magnetic field on the arc shape and keyhole dynamic behavior was observed and analyzed by high-speed photography. The results showed that without a magnetic field, the arc shape underwent continuous scaling during the transition of molten droplets, the keyhole root was unstable, and there were a large number of process-induced porosities distributed in the center of the weld. When the magnetic field strength was 10 mT, the keyhole was completely unstable, and the size of the internal porosities in the weld seam significantly increased while the number of porosities decreased. At a magnetic field strength of 20 mT, the arc exhibited a rotating oscillation behavior, the keyhole was in a stable open state, and no porosity was detected in the weld seam. Upon reaching a magnetic field strength of 30 mT, the keyhole was also in a root unstable state, but the collapse and recombination speed of the keyhole were faster than that without a magnetic field, and the size and number of internal porosities in the weld seam significantly decreased. [ABSTRACT FROM AUTHOR]

Friction Stir Welding is a process that has led to increasing usage of aluminum and its alloys in different industries, since it is an autogenous and a solid-state welding process. The work developed in this paper was focused on the analysis of the mechanical behavior of AA7075-T651 friction stir butt welded joints, of 4 mm of thickness, under different loading and temperature conditions. A selection process was applied to assure the appropriate welding parameters. The welds from which the investigated specimens were manufactured from were submitted to nondestructive testing to assess the presence of welding defects. Fatigue tests were carried out, under a constant amplitude loading regime, at stress ratios of 0.05 and 0.5 and at temperatures of 23 °C and 150 °C. The results obtained by the fatigue tests point to a higher fatigue life of the specimens when the highest stress ratio, R = 0.5, was used (for the maximum stress applied), for both loading temperatures. For the stress range, the contrary was found to be true. Room temperature was also found to result in a significantly better fatigue performance. A Scanning Electron Microscope was used to characterize the fatigue fracture surfaces. [ABSTRACT FROM AUTHOR]

Advanced high-strength steels are important for the automotive sector. Metal active gas (MAG) is the most popular method for joining grades of steel. The goal of the paper is to analyze the mechanical properties of the MAG welding joint made of highstrength DOCOL 1100M intended for the construction of electric vehicles. The manuscript shows a basic understanding of the properties of DOCOL joints. This type of material is characterized by a martensitic microstructure, which makes it difficult to make a proper joint. The tensile strength, metallographic structure, and type of non-metallic inclusions were analyzed as a function of the oxygen amount in the protective gas mixture. Investigations of oxide non-metallic inclusions were carried out using scanning electron microscopy. This article attempts to obtain high joint strength of the electric vehicle structure by controlling the average size of non-metallic inclusions in the weld, which is influenced by shielding gas in the MAG welding process. The solution has application potential for the automotive industry, especially for electric vehicles. [ABSTRACT FROM AUTHOR]

This paper adopted the new process of double-sided oscillation laser autogenous backing welding and double-sided oscillation laser–TIG hybrid filling welding to achieve 80 mm thick SA-738Gr.B steel narrow gap welding in the horizontal position. The microstructure, mechanical properties, and residual stress of the welded joints in the as-welded (AW) state and in the post-weld heat treatment (PWHT) state were analyzed comparatively. The results show that because of the high-temperature tempering effect of PWHT, the microstructure of the welded joint is transformed into a high-temperature tempered microstructure with the increase in alloy carbide precipitation. The grains growth of the backing weld and the base material is obvious. The relative frequency of the high-angle grain boundary of the weld increases. Under the PWHT, the tensile strength of the welded joint decreases, and the residual stresses of the welded joint are redistributed and reduced significantly. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The paper studies the influence of arc welding technological processes on the resistance of welded joints of sparcely-alloyed weathering 06g2BDP steel to cold and hot cracking and brittle and fatigue fracture. with the help of the Implant method and using the technological tekken sample, the conditions for cold cracking were evaluated and the methods of their elimination were recommended. It is shown that with the use of mechanized welding in shielding gases, solid-section and flux-cored wires provide high technological strength of welded joints in terms of hot cracking in a wide range of welding modes. On the other hand, when using coated electrodes, this range is narrowed, and at Vdef ≥ 20 mm/min, joints are prone to the formation of this defect. the results of studies on the evaluation of welded joint resistance to brittle fracture indicate high values of the stress intensity factor KQ for both the weld and HAZ metal. The endurance limit of T-joints when tested by cyclic loading was determined, which is [σ]-1 = 35 MPa. [ABSTRACT FROM AUTHOR]

Aluminum alloy is crucial for lightweight and fuel-efficient vehicles due to its strength, lightness, and corrosion resistance. However, welding aluminum vehicle parts poses challenges, particularly porosity issues caused by trapped hydrogen gas in the weld metal. This study aimed to investigate the impact of the welding room environment on the health and properties of aluminum welding joints. To achieve this, an isolated room was created, where variations in airflow velocity (1.1 m/s, 1.6 m/s, and 2.1 m/s) and temperature (19 °C, 27 °C, and 35 °C) were implemented. The fume condition of the room was assessed to determine its impact on health aspects, while bead appearance and macrostructure were evaluated to assess weld joint quality. Results revealed that higher airflow velocity and temperature reduced fume concentration in the welding room, indicating a healthier environment. However, these conditions also led to increased porosity defects and influenced the performance of the shielding gas. Additionally, higher ambient temperatures increased hydrogen solubility in the molten aluminum, exacerbating porosity issues. For optimal welder comfort and high-quality weld joints, it is recommended to maintain a low temperature and airflow velocity in the welding room, ensuring a healthier working environment while minimizing porosity defects. [ABSTRACT FROM AUTHOR]

The wear surface morphology of AlSi10Mg specimens, originally manufactured using selective laser melting (SLM), has been analyzed in the context of exposure to heat from gas flames. The first stage of the experimental work included the performance of surface heat-exposure on SLM-prepared specimens through oxyacetylene gas welding. Gas welding was utilized with three different flames, namely; reducing, neutral, and oxidizing on the as-built specimens of SLM. The post-surface-treated specimens were subjected to pin-on-disk wear testing against fixed parameters. After the performance of wear testing at two different radii, the mass loss of each of the four types of specimens was calculated including the three specimens exposed to heat along with the as-built specimens. The results showed that the maximum amount of mass losses at 24 mm and 30 mm radii belongs to the neutral flame specimens and the least was for the as-built condition specimens. Upon analysis, the heat-exposure specimens through all three types of gas flames resulted in an increase in the amount of mass in contrast to the as-built specimens. Moreover, the morphologies of the developed wear tracks at surfaces were examined using the scanning electron microscope (SEM) for the understating of the mechanism. [ABSTRACT FROM AUTHOR]

The article discusses the future trends and technologies in the welding industry, focusing on the vision of DNIPROMETYZ TAS, a leading manufacturer of welding wire in Ukraine. The article highlights the significant growth predicted in the welding materials market over the next six years, driven by industries such as automotive, fuel and energy, and pipeline construction. The main challenges faced by the industry include unstable raw material supplies, price fluctuations, and a shortage of skilled welders. DNIPROMETYZ TAS addresses these challenges by collaborating with educational institutions, investing in training, and providing technical assistance. The company also aims to expand its presence in the European market, particularly in Germany, and focuses on diversifying its products and introducing new technologies. The article emphasizes the importance of automation and innovation in the industry, as well as the integration of digital technologies. DNIPROMETYZ TAS offers a wide range of welding wire products and strives to be a strategic partner for its customers. The company is committed to producing high-quality products and has obtained various certifications to ensure compliance with international standards. In the future, DNIPROMETYZ TAS plans to continue investing in new technologies and expanding its product range to meet customer needs. The company aims to create innovative solutions that enhance the quality, reliability, and environmental friendliness of welding technologies. [Extracted from the article]

This work explored the possibility of producing a compositional functionally graded material (FGM) between mild steel and Inconel 625. An in-house fabricated, dual filler wire tungsten inert gas welding set up was used to deposit weld beads on a mild steel substrate. Filler wire feed rates were controlled independently and the combinations of filler material volumes, i.e., mild steel–Inconel 625 of (100:0), (75:25), (50:50), (25:75), and (0:100) were fed into the arc simultaneously and individual weld beads deposited. Preliminary studies revealed that defect free completely fused new alloys were formed and intermetallic phases rich in Nb observed. Compositional analysis showed that the content of each element changed from one alloy to the other gradually, smoothly indicating the feasibility of a mild steel–Inconel 625 functionally graded material. [ABSTRACT FROM AUTHOR]

Introduction: The need to permanently join two or more pieces of metal using heat is a frequent condition in various fields of medicine such as dentistry. Welding, brazing and soldering are permanent joining techniques between different metals that require in-depth background knowledge in order to obtain predictable results. Aim: This review examines the different methods of joining metals using heat and their fields of application. Discussion: It is possible to create permanent metal joints in various phases of the creation of final products that will be used on the patient. In several cases, welds are also made directly by the manufacturer during industrial processing. In dentistry, dental laboratories perform complex welds mainly on dental prostheses and orthodontic appliances during the production process. It is also possible to obtain intraoral welding carried out by the clinician inside the patient's oral cavity. Welding can be carried out using combustible gases, electric current, infrared light and laser light through different technical procedures which must be chosen according to the specific needs and the metals to be joined. Conclusions: It is useful for the dentist and dental technician to know the different welding methods, including those carried out in the factory by the manufacturer, to better understand the physical properties and mechanical resistance of the components marketed for the construction of prostheses and orthodontic appliances. The enormous variety of conditions in which those who practice welding can find themselves therefore presupposes in-depth knowledge in this field in order to apply the most suitable technique. [ABSTRACT FROM AUTHOR]

Autogenous dissimilar welding of oxygen-free copper to austenitic stainless steel AISI316 was successfully performed by electron beam welding (EBW) using strategic base metal plate tilt of 22 deg and beam shift. The effect of focus distance, beam current, and travel speed on the tensile strength, percent elongation, and impact strength of the welded joints was investigated. The maximum tensile strength was achieved to be 282 MPa at a focus distance of 20 mm, a beam current of 40 mA, and a travel speed of 400 mm/min. Elemental integrity was examined through a continuous energy-dispersive spectroscopy (EDS) scan across the joint for all the welded samples. It was observed that the concentration of elements Fe, Cr, and Ni increased, and that of Cu decreased from the copper region to stainless steel (SS) in the weld zone. The microstructures and microhardness profile of the welded joint were studied. A lower microhardness value was present in the weld region due to a higher fraction of Cu in the weld compared with that of SS. Thus, the balance of energy over the dissimilar materials effectively allowed autogenous welding of a pair of materials which is challenging to join. [ABSTRACT FROM AUTHOR]

This work is devoted to the study of the processes that take place in the welding gap during explosive welding (EW). In the welding gap, when plates collide, a shock-compressed gas (SCG) region is formed, which moves at supersonic speed and has a high temperature that can affect the quality of the weld joint. Therefore, this work focuses on a detailed study of the parameters of the SCG. A complex method of determining the SCG parameters included: determination of the detonation velocity using electrical contact probes, ceramic probes, and an oscilloscope; calculation of the SCG parameters; high-speed photography of the SCG region; measurement of the SCG temperature using optical pyrometry. As a result, it was found that the head front of the SCG region moved ahead of the collision point at a velocity of 3000 ± 100 m/s, while the collision point moved with a velocity of 2500 m/s. The calculation of the SCG temperature showed that the gas was heated up to 2832 K by the shock compression, while the measured temperature was in the range of 4100–4400 K. This is presumably due to the fact that small metal particles that broke off from the welded surfaces transferred their heat to the SCG region. Thus, the results of this study can be used to optimize the EW parameters and improve the weld joint quality. [ABSTRACT FROM AUTHOR]

To solve the shortage of austenite phase precipitation caused by nitrogen loss in the welding process of UNS S2205 duplex stainless steel (DSS), shielding gas nitriding was investigated by adding different N2 contents in Ar shielding gas during the welding process. A good thin-walled pipe butt joint was formed using the pulsed tungsten inert gas (P-TIG) welding method with Ar-N2 shielding gas. High cycle fatigue tests of the weld joints were conducted to study the effect of shielding gas nitriding on the fatigue properties. Fatigue tests at three stress levels of 225 MPa, 270 MPa, and 360 MPa were carried out on the weld joints with different N2 contents, and the fatigue samples were all fractured in the high temperature heat-affected zone (H-HAZ). Within the current process parameters, the fatigue life of the 4 vol.% N2 welded joints was optimal. Fatigue striations appeared in the fatigue crack propagation zone, and the transient fracture zone was similar to the tensile fracture. Under the low-stress level, the area of the crack propagation zone under 4 vol.% N2 was the highest, the tear ridges all expanded around the crack source area, and the fatigue crack propagation zone presented a radial distribution. The proliferation and expansion of dislocations were mainly carried out in the austenite grains, and the dislocation density of the fatigue specimens under 4 vol.% N2 was smaller than that of the Ar specimens. Shielding gas nitriding effectively improved the balance of the two-phase ratio and the hardness of austenite phase, optimized the internal slip system, inhibited the proliferation of dislocations in the austenite phase, and improved the fatigue life of weld joints. [ABSTRACT FROM AUTHOR]

The authors have considered the gas-dynamic influence upon the mechanical properties, chemical composition, microhardness, and geometry of single-rim welds made of 30ХГСА steel when welding with a consumable electrode under a double-jet gas shield. Their regressional relationships on the selected controlled welding parameters have been developed. It has been found that the gas-dynamic effect of a dynamic shield gas jet has a controlling influence on the formation of welds made of alloy-treated 30ХГСА steel. [ABSTRACT FROM AUTHOR]

Joining of NiTi shape memory alloys with commercially pure titanium (Ti) is of great interest for manifold industrial applications. However, dissimilar fusion welding of these materials is associated with the formation of extremely brittle intermetallic compounds, e.g., Ti2Ni and TiNi3, which drastically limit the mechanical properties of NiTi/Ti joints. The present investigation seeks to improve both chemical compatibility and mechanical performance through intermixing of a niobium foil as filler material into a NiTi/Nb/Ti butt-joint configuration by means of pulsed laser beam welding. Different pulse durations are applied to tailor intermixing and evaluate the deviating chemical compositions of the weld metal. It is demonstrated that intermixing of niobium significantly increases the weldability of the material combination NiTi/Ti compared to autogenous welding. However, the proportion of intermixed filler material exerts a substantial impact on the microstructural evolution and mechanical properties. Ultimate tensile strengths of up to 679 MPa with fracture occurring in the titanium base metal at an elongation at break of 18.7 pct is obtained by a reduction of the pulse duration, which represents a major improvement over previous studies focusing on fusion welding of NiTi to titanium and its alloys. [ABSTRACT FROM AUTHOR]

Materials with good mechanical and chemical properties (materials should be resistant to various types of corrosion) are proposed for the various structures of means of transport. For this reason, high-alloy steels, including duplex steels, are increasingly used in the automotive industry. The 1.4462 duplex steel used in means of road transport steel could be treated as an interesting high-strength stainless material used in the automotive industry. Generally, duplex steels have a high resistance to localized and uniform corrosion. The duplex and superduplex steels are assumed to be rather proper weldable materials; however, cracks could be observed both in the heat-affected zone (HAZ) and in the weld. The article analyses the influence of tubular cored metal arc (136) with active gas shield welding (process 136) parameters on the arrangement of correct joints used in tanker truck elements, as an example of welding in the automotive sector. Various mechanical tests checking the properties of joints were realized. The goal of the paper is to choose the correct welding parameters for elements of 1.4462 steel. The construction elements of a tanker truck are made by the 136 method of welding. [ABSTRACT FROM AUTHOR]