Shielding Gas Composition Research Articles

Improving the product of strength and ductility and corrosion resistance by adding He shielding gas in the CMT additive manufacturing process of Ti6Al4V

The cold metal transfer additive manufacturing (CMTAM) of titanium alloys presents a promising solution for the efficient fabrication of large titanium alloy armor components. In this study, different proportions of He gas were added to the welding shielding gas used in the CMTAM of Ti6Al4V, aiming to improve forming quality, the product of strength and ductility and corrosion resistance. Simultaneously, the influence of different He contents on the microstructure, mechanical properties, and corrosion behavior of CMTAM of Ti6Al4V was explored. The research revealed that during the process of CMTAM of Ti6Al4V, as the proportion of He as the shielding gas increased, the arc voltage increases, and the arc becomes more stable. Meanwhile, the wettability of the weld pool improves, resulting in a more spread out weld pool. The fabrication precision of the built material also improved. Microstructural observations indicate that the prior-β grain size gradually increased with the increase in He proportion, the heat input for additive manufacturing also increased，and the martensitic α’ transformed into a basketweave α+β structure. The length and width of the α phase increased, the texture intensity decreased, and the Schmid factor increased. Tensile tests were conducted on samples with different He proportions showed that as the He proportion increased, within the component resulted in a noteworthy enhancement in the product of strength and ductility increase exceeding 50 %. This suggests that He as the shielding gas addition can effectively optimize the strength-plasticity balance in additive manufactured titanium alloys without the need for post-processing heat treatment. Electrochemical tests were conducted in a 3.5 wt% NaCl solution revealed that the addition of He gas significantly improved the corrosion resistance of Ti6Al4V. Specifically, the corrosion resistance was optimal when the shielding gas composition was 50 %He+50 %Ar, far surpassing that of cast Ti6Al4V.

Effect of shielding gas composition and pulsed current frequency on geometry and nitrogen content of 304L austenitic stainless-steel welds

Abstract This study investigated the effects of pulsed current frequency and shielding gas composition on the weld metal geometry and nitrogen content. Austenitic stainless-steel sheets were welded by gas tungsten arc welding using 0, 0.5, 1, 2, 5, and 10 vol.% of nitrogen gas in argon shielding gas and pulse frequencies of 40, 80, 120, 160, and 200 Hz. Weld sections were recorded using a stereomicroscope. Weld depth and cross-section of the weld metal were measured by ImageJ® software and their changes were recorded. Nitrogen analysis tests were performed on the weld metal and, the results were analyzed. Investigations revealed that by increasing the nitrogen content of the shielding gas up to 10 vol.%, the nitrogen content of the weld metal almost doubles at the maximum nitrogen level. This increase was more considerable at higher current frequencies. Also, by increasing the pulsed current frequency, the weld pool and the weld metal depth-to-width ratio increased to 37 % and 44 %, respectively, at the maximum level of shielding gas nitrogen. In addition, at the frequency of 200 Hz, increasing nitrogen led to an 86 % and 72 % increase in the weld pool and the weld aspect ratio, respectively.

Analysis of arc stability of plasma main arc and inter-wire arc in skew-coupling arc welding

By adjusting the inter-wire arc (IWA) posture, the skew-coupling arc (SCA) is proposed to address the polar effect in the cross arc, enabling decoupling control of heat, force, and mass transfer. Despite the advancement, the arc stabilization mechanism in the SCA remains poorly understood, hindering its application as a heat source in welding or additive manufacturing. To elucidate this mechanism, various influencing factors such as power supply characteristics, shielding gas composition, IWA posture, and plasma main arc (PMA) were analyzed. An electrical signal and high-speed camera synchronous acquisition system was utilized to analyze current-voltage waveforms and arc shapes. The results indicate that the arc stability of the SCA can be enhanced by ensuring specific external conditions. Constant voltage power supply enhances the self-regulating effect of the IWA, maintaining the IWA and the PMA in a hybrid state at all times. Introducing an oxidizing gas to the shielding gas can effectively suppress cathode spot climbing and stabilize the IWA. The vertical spacing between wires directly impacts the PMA deflection, while the wire horizontal angle has a lesser effect. The heat-regulating effect of the PMA column boosts the arc length regulation by the IWA. The current and the ion gas flow rate in the PMA minimally influence the SCA stability. These findings can provide a solid foundation for further applications of the SCA as heat source.

"The impact of shielding gas composition and welding speed on weld quality in MAG welding: An experimental study "

"The impact of shielding gas composition and welding speed on weld quality in MAG welding: An experimental study "

Effect of TIG welding parameters on 316 L stainless steel joints using taguchi L27 approach

The AISI 316 L stainless steel was welded using Tungsten Inert Gas (TIG) welding, utilizing ternary shielding gases Argon (Ar), Helium (He), and Nitrogen (N2). This study aimed to assess the effects of these ternary shielding gases on the microstructure, bead profile, and bead appearance. It provides a comprehensive grasp of welding parameters’ interplay with shielding gas compositions, enabling engineers to make informed choices that significantly influence the excellence, productivity, and lastingness of the welding process. The Taguchi L-27 approach was employed, incorporating different contents of N2 (2.5 vol. % to 7.5 vol. %) and He (10 vol. % to 30 vol. %) within the Ar shielding gas composition. Additionally, welding current intensities, ranging from 120 A to 180 A, were also used in the experiment. The results demonstrated that higher content of He and N2 resulted in elevated levels of austenite-forming elements. Therefore, for TIG welding at the arc current intensity of 150 A, it is recommended to utilize the shielding gas mixtures (2.5 vol. % N2 + 10 vol. % He + 87.5 vol. % Ar). Furthermore, by augmenting the content of both N2 and He within the Ar shielding gas mixture, in addition to adjusting the arc current, a notable expansion in both the width and depth of the weld profile was achieved. This achievement, in turn, played a pivotal role in securing comprehensive fusion throughout the welding process.

Influence of GMAW and PAW methods of additive arc surfacing and shielding gas composition on surface geometry and metal structure

Influence of GMAW and PAW methods of additive arc surfacing and shielding gas composition on surface geometry and metal structure

Investigation of 300M ultra-high-strength steel deposited by wire-based gas metal arc additive manufacturing

300 M ultra-high-strength steel (UHSS) is widely used to produce landing gear components for aircraft. The conventional manufacturing route for these components involves extensive machining and significant material wastage. Here, the application of wire-based gas metal arc additive manufacturing to produce 300 M UHSS parts was investigated. In particular, the influence of torch shielding atmosphere on the process stability and material performance of 300 M UHSS was investigated. The shielding gases used for comparison are pure Ar, Ar with 2.5% CO2, Ar with 8% CO2, Ar with 20% CO2, and Ar with 2% CO2 and 38% He. It was found that the arc length decreased, the transfer mode changed from spray to droplet mode, and spattering became more severe as the CO2 proportion increased. Additionally, replacing Ar with He led to a broader arc core, and a slightly shorter arc length and maintained a spray transfer, which decreased spatter. The wall surface roughness followed the trend in spatter, becoming worse with the increasing CO2 proportion, and better with He addition. Adding CO2 and He in pure Ar significantly increased the bead and wall width. The microstructure and mechanical properties exhibited a strong location dependence in the as-built state, with fresh martensite and higher strength in the top region, and tempered martensite and better ductility in the reheated bulk. Generally, torch shielding gas composition appeared to have no significant effect on the microstructure evolution. This study provides a reference for the subsequent application of gas metal arc additive manufacturing to aircraft landing gear mass production to achieve a high deposition rate and process stability simultaneously.

Innovations in Welding Consumables for Enhanced Joint Integrity

This study investigates into the realm of welding technology, focusing on the transformative potential of innovative welding consumables in enhancing joint integrity. The investigation employs a mixed-methods approach, integrating experimental evaluations and literature analysis to comprehensively assess the impact of consumables on joint performance. Through mechanical testing, defect analysis, and microstructural examination, the study showcases the marked superiority of innovative consumables over traditional counterparts. Tensile strength and impact toughness improvements of 15% and 20%, respectively, are observed in joints formed with innovative consumables. Moreover, defect occurrences are significantly reduced, owing to enhanced flux formulations and optimal shielding gas compositions. Intriguingly, microstructural analysis unveils unexpected advantages, highlighting the potential for long-term joint durability. This research underscores the paradigm shift brought about by innovative welding consumables, promising safer, stronger, and more durable welded structures across industries.

Impact of Gas Metal Arc Welding Parameters on Bead Geometry and Material Distortion of AISI 316L

This study investigates the impact of gas metal arc welding (GMAW) parameters on the bead geometry and material distortion of AISI 316L. Three parameters—arc current in ampere (A), filler feed rate (m/min), and gas composition—were modified at varying levels in order to examine their effects. This study sheds new light on MAG welding lines’ physical properties and behavior and highlights the influence of quaternary shielding gas compositions. Taguchi analysis, which includes signal-to-noise (S/N) ratio and analysis of variance (ANOVA), was utilized to analyze and optimize the welding parameters. This study found that arc current significantly impacts bead geometry, while the shielding gas composition has the most significant effect on angular distortion and transverse shrinkage. The optimal welding parameters for achieving the best bead height and width are 160 A, 3.5 m/min, G1, with a bead height of 4.89 mm, and 120 A, 3 m/min, G2, with a bead width of 6.69 mm. Moreover, the optimal welding parameters for minimizing both angular distortion and transverse shrinkage are 120 A, 4 m/min, G2, resulting in an angular distortion value of 0.0042° and a transverse shrinkage value of 0.0254 mm. This research has practical implications for improving welding performance and can contribute to the advancement of MAG and MIG welding in manufacturing applications.

Effect of welding speed and shielding gas composition on the properties of laser welded EN AW 6061-T6 al alloy using 5356 filler metal

In this study, EN AW 6061-T6 Al alloy having a thickness of 6 mm was joined with a 5000 W fiber laser welding machine using different welding speeds (20, 25, and 35 mm/s) and shielding gas compositions (100% Ar, % 50 Ar + % 50 He, % 25 Ar + 75 He). In order to reduce the strength decrease in the weld zone, 5356 filler metal with a diameter of 1.2 mm was used with the cold wire feeding method at a constant speed of 2 m/min. Structural analyses of the joints were performed by macroscopic and microscopic examination, and hardness profiles and strength values of the joints were determined by mechanical tests. The findings showed that (i) the width of the seam increased due to the increase in the amount of He in the gas composition, and the number of pores decreased accordingly, (ii) although no significant change was observed in the hardness profiles, the highest tensile strength value (242 MPa) was obtained using a gas composition of 50% He + 50% Ar and welding speed of 20 mm/s, (iii) shear failure was the dominant fracture, and the porosities played a decisive role in the fracture.

Research Status of Stability in Dynamic Process of Laser-Arc Hybrid Welding Based on Droplet Transfer Behavior: A Review

With the synergistic effect of laser and arc heat sources, laser-arc hybrid welding (LAHW) technology can improve welding speed and penetration depth, and enhance gap-bridging ability. This review describes the fundamental concepts and characteristics of droplet transfer behavior in LAHW. Emphasis was placed on the physical interaction between the laser and arc and the effect of the combined laser/arc heat sources on the welding process. However, the physical understanding of these multivariable and complex interactions is still evolving. Through numerous research findings and summary, it is found that there are several critical factors, including the laser-to-arc distance, heat source leading mode, shielding gas composition, and laser power, affecting the droplet transfer characteristics. This review critically interprets the latest development in the basic understanding of LAHW. It lays great stress on the coupling effect of laser and arc in droplet transfer dynamic process of LAHW, and offers a direction for the future study and progress of LAHW. Significant fields for future research are also confirmed.

EFFECT OF SHIELDING GAS ON THE PROPERTIES OF STAINLESS-STEEL SUS 304L PLUG WELDED

The effect of shielding gas composition and welding current on the mechanical-physical properties of plug welding joint stainless steel SUS 304L has been investigated. Metal Inert Gas (MIG) welding was used to join SUS304L with a thickness of 3 mm. The variations of welding current were 80 A, 100 A, and 120 A, while variations of shielding gas composition were 100% Ar; 92,5% Ar-7,5% CO2; 85% Ar-15% CO2; 77,5% Ar-22,5% CO2; 100% CO2. Macro and microstructural tests were conducted to determine welded joints physical properties. Tensile-shear testing and micro hardness Vickers were done to determine welded joints physical properties. The results show that the higher level of welding current and CO2 content in the shielding gas, the more tensile-shear load bearing capacity and decreased hardness. The welding current of 120 A and shielding gas 77,5% Ar-22,5% CO2 produced welded joints with the highest tensile-shear load bearing capacity. The nugget size increased as the higher level of welding current and the CO2 content in the shielding gas due to the increase of heat input.

Investigating the Microstructure and Mechanical Properties of Materials Joined using Advanced Welding Techniques

The science of materials joining has witnessed the emergence of advanced welding techniques, which have become crucial operations. These techniques provide improved manipulation and regulation of the microstructure and mechanical characteristics of welded joints. The primary objective of this work is to examine the complex correlation between the microstructure and mechanical characteristics of materials that have undergone joining processes utilising sophisticated welding methods. The present research provides insight into the development of many microstructural characteristics, including grain growth, phase transitions, and defect creation, and their influence on the mechanical properties of welded joints. The mechanical characteristics being examined span a broad spectrum of factors, such as tensile strength, toughness, hardness, and fatigue resistance. The evaluation of these qualities is conducted by subjecting specimens obtained from the welded joints to a variety of mechanical tests. Through the correlation of microstructural traits with the observed mechanical behaviour, a more profound comprehension of the structure-property link in advanced welding is attained. In addition, this study investigates the impact of welding parameters, including welding speed, heat input, and shielding gas composition, on the microstructure and mechanical characteristics. The objective of this inquiry is to optimise the welding parameters in order to get the specified material characteristics in the welded connections, while simultaneously minimising the development of faults and ensuring the maintenance of structural integrity.

Effects of Shielding Gases on the Weldability of Laser Welded Austenitic Stainless Steel

In laser welding of austenitic stainless steels, shielding gases have great potential for improving the mechanical properties of the welds, suppressing plasma plumes, and stabilizing the keyhole. Previous studies have shown that shielding gases can alter the weld geometry and microstructural constituents of the welds. Disturbances of laser beam absorption by laser-induced plasma can be controlled through shielding gas parameters such as the shielding gas composition, flow rate, and supplying direction. In addition, surface-active elements added to the shielding gas can alter the behavior of the molten pool. In this paper, previous studies are reviewed to assess the shielding gas effects on the characteristics of laser-welded austenitic stainless steel. The activated mechanism of molten pool flow by additional surface tension active elements is also discussed.

Dissimilar welding of high nitrogen stainless steel and low alloy high strength steel under different shielding gas composition: Process, microstructure and mechanical properties

Ar–N2-O2 ternary shielding gas is employed in dissimilar welding between high nitrogen steel and low alloy steel. The effect of O2 and N2 is investigated based on the systematical analysis of the metal transfer, nitrogen escape phenomenon, weld appearance, nondestructive detection, nitrogen content distribution, microstructure and mechanical properties. There are two nitrogen sources of the nitrogen in the weld: high nitrogen base material and shielding gas. The effect of shielding gas is mainly reflected in these two aspects. The change of the droplet transfer mode affects the fusion ratio, N2 in the shielding gas can increase nitrogen content and promote the nitrogen uniform distribution. The addition of 2% O2 to Ar matrix can change the metal transfer from globular transfer to spray transfer, high nitrogen base material is thereby dissolved more to the molten pool, making nitrogen content increase, ferrite decrease and the mechanical properties improve. When applying N2-containing shielding gas, arc stability becomes poor and short-circuiting transfer frequency increases due to the nitrogen escape from droplets and the molten pool. Performance of the joints is improved with N2 increasing, but internal gas pores are easier to appear because of the poor capacity of low alloy steel to dissolve nitrogen, The generation of pores will greatly reduce the impact resistance. 4–8% N2 content in shielding gas is recommended in this study considering the integrated properties of the dissimilar welded joint.

Assessment of welding fume impacts in a confined workplace by two extraction patterns - a case study of small-scale manufacturing industries.

Welding fume exposure at work is recognized as a known concern for public health. This study aims to assess the welding fumes produced during welding using two different extraction patterns and to compare their influences. A thorough assessment of domestic arc welders in the erode district of India was done to assess their exposure to welding gases. The survey results chose the gas metal arc welding (GMAW) process for future investigation. The stainless-steel grade SS 316 L was used in this study. To weld 3-mm, 5-mm, and 6-mm-thick stainless-steel specimens, ER316 L filler wire and four shielding gas compositions were used. Two distinct, cost-effective welding hoods with a square duct section and a conical duct section were constructed to examine welding gases. The produced fume was collected on a 240mm glass fibre filter and re-weighted during welding. Gas flow rates of 5, 10, and 15 LPM were investigated, with current intensities of 150A, 200A, and 275A. A novel attempt has been made to compare fume formation rates (FFR) obtained using two extraction patterns. According to this investigation, weld fume hoods with conical duct sections extract more welding gases than square duct sections. The extraction rate using two extraction patterns was compared. Furthermore, the addition of CO2 to any shielding gas mixture results in a higher fume formation rate. The experimental FFR values were quite close to the American Welding Society (AWS) specifications. This finding also revealed that welders' socio-demographic characteristics, such as age, marital status, level of education, and work experience, influenced their awareness of occupational hazards and personal protection equipment (PPEs). As a result, there should be a strong emphasis on hazard identification education and strict enforcement of proper PPEs use among small-scale welders in and around the erode district to protect welders from a variety of hazards.

Welding characteristics and microstructure of an industrially processed Fe-Mn-Al-Ni shape memory alloy joined by tungsten inert gas welding

Iron-based shape memory alloys have recently attracted increased attention due to their low material costs combined with good workability and high transformation strains. They show excellent welding properties, as shown by several studies and compared to non-iron-based shape memory alloys, and are potential candidate materials for large-scale application as damping elements in building structures. Since subsequent heat treatment is only possible to a limited extent for large-scale components, it is necessary to minimize the effects of processing and welding operations on the shape memory properties. Therefore, a suitable microstructure must be established in the heat-affected zone and the fusion zone during the welding process. Thus, industrially processed polycrystalline Fe-Mn-Al-Ni was joined by tungsten inert gas welding with matching filler material. The phases formed upon welding with different parameters were investigated using optical microscopy, scanning electron microscopy and X-ray diffraction. Shielding gas composition as well as mean arc linear energy have a huge impact on the γ-phase precipitation. Intercrystalline cracking can be supressed by increasing the γ content. Further, the α-fraction and grain size in the fusion zone can be controlled by the welding parameters. Ultimately, a hardness value of the fusion zone equal to heat-treated material was achieved which suggests that the fusion zone may be able to transfer the stress required for martensitic transformation.

Effect of N2- and CO2-containing shielding gases on composition modification and carbonitride precipitation in wire arc additive manufactured grade 91 steel

Additive manufacturing (AM) represents a promising technique to fabricate metallic alloys with greater control of the resulting material features as compared to traditional manufacturing routes. Recently, there is greater interest in AM research on 9 wt% Cr ferritic/martensitic (F/M) steels, which are commonly studied for use in the nuclear energy industry. This research aims to prove that wire arc AM can manufacture F/M steels with adequate mechanical properties in multiple processing atmospheres and aims to study how shielding gas composition can be leveraged during fabrication to induce specific precipitation pathways. The effect of shielding gas composition on MX (M=Nb and/or V, XC and/or N) carbonitride precipitation in a 9 wt% Cr ferritic/martensitic (F/M) steel alloy known as Grade 91 was studied using N2 and CO2 gas additions to an inert Ar shielding gas atmosphere during wire arc AM. The N and C atoms present in the processing atmospheres were absorbed into the melt pools during fabrication. Due to their differing affinities for precipitate-forming reactions, the varying levels of C and N between the samples contributed to differences in final carbonitride composition and morphologies. Such precipitate behavior is of interest as carbonitrides have been shown to contribute to increased mechanical performance. This increased performance was studied via electron microscopy and tested for strength, ductility, and fracture properties.

Improving Keyhole Stability during Laser Welding of AA5xxx Alloys

<div class="section abstract"><div class="htmlview paragraph">Laser welding of the magnesium-bearing AA5xxx aluminum alloys is often beset by keyhole instability, especially in the lap through joint configuration. This phenomenon is characterized by periodic collapse of the keyhole leaving large voids in the weld zone. In addition, the top surface can exhibit undercut and roughness. In full penetration welds, keyhole instability can also produce a spikey root and severe top surface concavity. These discontinuities could prevent a weld from achieving engineering specification compliance, pose a craftsmanship concern, or reduce the strength and fatigue performance of the weld. In the case of a full penetration weld, a spikey root could compromise part fit-up and corrosion protection, or damage adjacent sheet metal, wiring, interior components, or trim.</div><div class="htmlview paragraph">Previous work at Ford Research and Advanced Engineering evaluated the potential of a number of factors and techniques to improve keyhole stability in laser welding AA5xxx alloys without filler wire, including penetration, travel speed, laser beam inclination angle in the direction of travel, shield gas composition and delivery method, beam diameter, and beam oscillation frequency.[<span class="xref">1</span>] It was found that higher travel speeds improved keyhole stability and thereby weld strength.</div><div class="htmlview paragraph">The objective of the present investigation was to evaluate the effect of travel speed on keyhole stability during laser welding of AA5xxx alloys with filler wire in lap through joint configuration. The investigation found that higher travel speeds reduce voids and other concomitant keyhole instability discontinuities, thereby increasing weld strength.</div></div>

Direct Sensing of Superoxide and Its Relatives Reactive Oxygen and Nitrogen Species in Phosphate Buffers during Cold Atmospheric Plasmas Exposures

This study aims at sensing in situ reactive oxygen and nitrogen species (RONS) and specifically superoxide anion (O2•-) in aqueous buffer solutions exposed to cold atmospheric plasmas (CAPs). CAPs were generated by ionizing He gas shielded with variable N2/O2 mixtures. Thanks to ultramicroelectrodes protected against the high electric fields transported by the ionization waves of CAPs, the production of superoxide and several RONS was electrochemically directly detected in liquids during their plasma exposure. Complementarily, optical emissive spectroscopy (OES) was used to study the plasma phase composition and its correlation with the chemistry in the exposed liquid. The specific production of O2•-, a biologically reactive redox species, was analyzed by cyclic voltammetry (CV), in both alkaline (pH 11), where the species is fairly stable, and physiological (pH 7.4) conditions, where it is unstable. To understand its generation with respect to the plasma chemistry, we varied the shielding gas composition of CAPs to directly impact on the RONS composition at the plasma-liquid interface. We observed that the production and accumulation of RONS in liquids, including O2•-, depends on the plasma composition, with N2-based shieldings providing the highest superoxide concentrations (few 10s of micromolar at most) and of its derivatives (hundreds of micromolar). In situ spectroscopic and electrochemical analyses provide a high resolution kinetic and quantitative understanding of the interactions between CAPs and physiological solutions for biomedical applications.