Gas Metal Arc Welding Technique Research Articles

Microstructural characteristics and properties of wire arc additive manufactured 304L austenitic stainless steel cylindrical components by different arc welding processes

Wire arc additive manufacturing (WAAM) is an advanced additive manufacturing (AM) technology that offers low cost and high deposition rates, making it suitable for building large metal parts for structural engineering applications. However, various welding procedures result in differing heat inputs and repetitive heating treatments throughout the deposition process, which can affect the microstructural and mechanical characteristics of the parts. In the current study, cylindrical parts made of 304L austenitic stainless steel (ASS) were manufactured using the WAAM technique, employing both gas metal arc welding (GMAW) and cold metal transfer (CMT) processes. This study explores the correlation between WAAM techniques and their effects on the bead geometry, microstructure and mechanical properties. The microstructure of the cylinders consisted of vertically growing austenite dendrites with residual ferrite (δ) within the austenite (γ) matrix. Compared to the bottom region (region ①), the top region (region ②) contained more residual ferrite. Although the microstructural characteristics from region ① to region ② are similar, they exhibit different ferrite morphologies. The rapid cooling rate in the CMT-AM process resulted in finer structures and a greater presence of ferrite phases in both regions compared to the GMAW-AM method. Cylinders produced by the CMT process displayed nearly uniform properties across both regions and demonstrated superior tensile properties, hardness, and impact toughness relative to those made using the GMAW technique. The WAAM 304L ASS cylinders also showed enhanced performance compared to stainless steel manufactured using traditional industrial forging standards, indicating that WAAM-processed 304L ASS cylinders are suitable for industrial applications.

Investigation of Microstructure and Mechanical Properties of High-Depth-to-Width-Ratio Horizontal NG-GMAW Joint for S500Q Steel.

A novel high depth-to-width ratio of 15:1 narrow-gap gas metal arc welding technique was developed for the welding of S500Q steel in a horizontal butt joint. The bead arrangement of the I groove was optimized to produce a high-quality connection with the upper sidewall of the joint. The microstructure and mechanical properties were observed and evaluated by optical microscopy, scanning electron microscopy, tensile testing, and micro-hardness and impact toughness testing at 1/5, 2/5, 3/5, and 4/5 thickness of the joint. The 3/5 T position exhibited the highest strength, which was attributed to the presence of finer carbide precipitates. The highest micro-hardness appeared at 4/5 T. The highest impact toughness appeared at 3/5 T. The formation of coarse granular bainite was the major reason for the decrease in impact toughness in other regions. A microscopic fracture at 1/5 T and 3/5 T was further analyzed. It was observed that the width of the fibrous zone at 3/5 T was significantly larger than that at 1/5 T. The radial zones at 1/5 T were observed to exhibit cleavage, with secondary cracks on the fracture surface.

Investigation of the fracture resistance of high strength ferritic steel welds in gaseous hydrogen environment

Hydrogen is expected to play a major role in the decarbonization of the energy grid. As a fuel, it possesses an elevated energy density per unit mass, about twice as much as natural gas but also a very low mass density; for this reason, it is preferably stored and transported at elevated pressures in the gas phase to achieve a comparable volumetric energy density. High strength quenched and tempered ferritic steels are widely used for gaseous hydrogen storage despite the fact that hydrogen affects material properties and result in higher fatigue crack growth rate and lower fracture toughness.This work presents the results of a comprehensive fracture toughness test program in gaseous hydrogen for the characterization of base metal, heat affected zone and weld metal on a high strength, quenched and tempered steel, suitable for the construction of hydrogen pressure equipment.Full penetration, butt welded joints were made using partly mechanized gas metal arc welding technique on a weldable, high strength steel, namely EN 101216-3 grade P690 QL2. Two different welding procedures were evaluated, and fracture toughness tests were conducted according to ASTM E1820 requirements, in high purity (99.9995%) hydrogen gas at a pressure of 200 bar on specimens extracted from base metal, heat affected zone and weld metal. While base metal and weld metal exhibited stable crack growth behavior, heat affected zone showed variable behavior as a function of the post-weld heat treatment conditions. It was found that local micro-hardness spots are a concern and should be controlled through dedicated post weld heat treatment operation to limit hardness values for use of welds in H2 gas conditions.

Elucidating the Effect of Step Cooling Heat Treatment on the Properties of 2.25 Cr-1.0 Mo Steel Welded with a Combination of GMAW Techniques Incorporating Metal-Cored Wires.

The prospect of using metal-cored wires instead of solid wires during gas metal arc welding (GMAW) of 2.25 Cr–1.0 Mo steels embraces several challenges. The in-service requirements for the equipment made up of these steels are stringent. The major challenge faced by the manufacturers is temper embrittlement. In the current study, the temper embrittlement susceptibility of the welded joint was ascertained by subjecting it to step cooling heat treatment. A 25 mm thick 2.25 Cr–1.0 Mo weld joint was prepared using a combination of the regulated metal deposition (RMD) and GMAW processes incorporating metal-cored wires. After welding the plates were exposed to post-weld heat treatment followed by a rigorous step cooling heat treatment prescribed by API standards. The temper embrittlement susceptibility of the weld joint was ascertained by Bruscato X-factor as well as by formulating ductile-to-brittle transition temperature (DBTT) curves by carrying out the impact toughness testing at various temperatures. Detailed microscopy and hardness studies were also carried out. It was established from the study that the X-factor value for the welded joint was 15.4. The DBTT for the weld joint was found to occur at −37 °C which was well below 10 °C. Optical microscopy and scanning electron microscopy indicated the presence of carbides and the energy dispersive X-ray spectrometry studies indicated the presence of chromium and manganese-rich carbides along with the presence of sulfur near the grain boundaries. This study establishes a base for the usage of metal-cored wires particularly in high temperature and pressure application of Cr–Mo steels.

Investigation of Double-Pulsed Gas Metal Arc Welding Technique to Preclude Carbide Precipitates in Aerospace Grade Hastelloy X

Investigation of Double-Pulsed Gas Metal Arc Welding Technique to Preclude Carbide Precipitates in Aerospace Grade Hastelloy X

Development of Pulsed Cold Metal Transfer and Gas Metal Arc Welding Techniques on High-Strength Aerospace-Grade AA7475-T761

High-strength aluminum alloy (AA7475) sheets are widely used in aerospace sectors due to its better performance, global suitability, and multifunctional features. The welding of AA7475 in the fusion welding process like gas metal arc welding (GMAW) is difficult due to cracks generation. However, these problems could be overcome by different variants of GMAW process, like pulsed and normal cold metal transfer (PCMT and NCMT) techniques. The main objective of this research work is to deliver a better insight into mechanical and metallurgical properties of butt joint welded AA7475 through PCMT, NCMT, and GMAW techniques with ER5356 and ER4043. The defects-free butt joints were observed for PCMT, NCMT, and GMAW processes with ER5356, whereas the presence of porosities is found for ER4043. The microsegregation of Fe, Si, Mg, Zn, and Cu leads to the emergence of Mg2Cu, Mg2Si, Al2Cu, Al2CuMg, MgZn2, Mg2Zn11, and Fe2Al6 phases in the AA7475 weldments. The development of binary brittle intermetallic Mg2Si phase affects the tensile strength of all weldments made with ER4043. Better joint efficiency (96.11%), impact toughness (12.1 ± 0.8 J), and microhardness (119 ± 7.4 HV) are found in PCMT with ER5356 compared to other processes. Because of the low heat input utilised, PCMT provides better joint strength and microstructural integrity than NCMT and GMAW.

Single-Pass Cladding Process Using Hot-wire Gas Metal Arc Welding Technique

The aim of this study is to improve cladding process productivity by high production rate with low dilution process by specifying technique as hot-wire GMAW process. The base metal of carbon steel A516 Gr70 was cladded by austenitic stainless steel 309LSi for creating a buttering layer and stainless steel 308LSi for hot-wire filler for topping a cladding layer in a one-pass run. The studied parameters this experiment consist of the feeding ratio of hot wire feeding speed per GMAW wire feeding speed and travel speed. Welding phenomenon during welding was observed by CCD camera with specifying the optical device to see the appropriate condition. The result showed the hot-wire GMAW cladding process could reduce cycle time 3.5 times compare with conventional FCAW cladding process. Moreover, dilution of this process could decrease lower than 15% with acceptable FN 3 on the top of weld surface. Therefore, single pass cladding process achieved by using this method with low dilution by still keep microstructure capability.

Fatigue crack growth in Al-Zn-Mg (7075-T651) welds obtained by modified indirect and gas metal arc welding techniques

The modified indirect electric arc welding (MIEA) and the conventional gas metal arc welding (GMAW) processes were used to weld 7075-T651 aluminum alloy plates. The fatigue life behavior was studied for three different zones in the welded joints (base metal, heat affected zone and weld metal). Compact-type (CT) specimens manufactured from the 7075-T651 aluminum alloy welded plates were subjected to fatigue tests with constant amplitude cyclic loading. The CT specimens corresponding to MIEA weld metal shown the largest fatigue life (number of cycles to reach the stable crack propagation), which was four times larger than the weld metal obtained by GMAW. This improvement was attributed to the high tensile residual stresses induced by the application of three welding beads of the GMAW process in contrast with the stresses induced by the application of only one welding bead in the MIEA. The tensile residual stresses were of no consequence in terms of fatigue life for the heat affected zone (HAZ). At this zone, the microstructural transformation (soft zone formation in the HAZ) induces a similar fatigue life behavior. For the weld metal produced by the MIEA welding process, the fatigue crack growth tends to increase in comparison with the GMAW, whereas for the HAZ no difference was detected. Fracture surfaces of all materials were analyzed by using scanning electron microscopy to correlate the fatigue crack growth condition with the striations formation.

Gas metal arc brazing of galvannealed steel sheets

An advanced gas metal arc welding technique with controlled short-circuiting mode of metal transfer and arcing at low power was employed for brazing of galvannealed steels using CuSi3 filler wire. The brazed joints showed the presence of an interface layer with Fe–Si intermetallic compounds (IMC). Increase in heat input resulted in an increase of the interface layer thickness. The maximum failure load of 2.5 kN was achieved for a heat input of 105 J mm−1 with the corresponding interface layer thickness of 2.7 µm. Heat inputs beyond 105 J mm−1 led to excessive spatter of zinc and increase in interface layer thickness with hard Si-rich IMC. In contrast, heat input values lower than 80 J mm−1 produced inadequate wetting of the steel surface by the molten filler wire deposit and resulted in low joint strength.

Experimental Validation of a Numerical Method that Predicts the Size of the Heat Affected Zone. Optimization of the Welding Parameters by the Taguchi’s Method

This work outlines the experimental validation of a numerical method which determines the size of the heat affected zone (HAZ) in a low carbon steel plate using the gas metal arc welding technique. The welding parameters match between the experimental and numerical simulations. The later allows the calculation of the weld beads and temperature fields from which the size of the HAZ can be inferred. This size from numerical simulations compares quite well with the experimentally measured HAZ from the metal grain macrostructure. A relationship between the bead size and the thermal energy source parameters, defined by the Goldak’s double ellipsoid, is found. Finally, the size of the HAZ is optimized by Taguchi’s method, which make use of the signal-to-noise ratio and the analysis of variance to obtain the influence of the parameters on the size of HAZ. The numerical code can be used for other electric arc welding techniques as GTAW or FCAW.

Effects of Gas Metal Arc Welding Techniques on the Mechanical Properties of Duplex Stainless Steel

The study has compared the effect of gas metal arc welding techniques on some mechanical properties of duplex stainless steel. The samples after welded were given post weld heat treatment (quenching in engine and neem oil). After the analyses, it was established that duplex stainless steel can be weld successfully using gas metal arc welding process (GMAW). Both Lubricating oil and neem oil can serve as quenching medium for post welding heat treatment of duplex stainless steel. The results of the studies also show that welding and heat treatment really affect the mechanical properties of the alloy; the control strength was 811.47 MN/m2 while that of the welded samples ranged from 177.07 to 257.32 MN/m2. The control impact energy was 162.70 J, while that of the welded samples ranged from 38.64 J to 56.20 J. The research also shows that the stress relief heat treatment gives better strength (A3 = 331 MN/m2) compared to those that were quenched in lubricating oil (A2 = 329 MN/m2) and neem oil (A1 = 222 MN/m2), but the reverse is the case in terms of toughness.

The Fatigue Behavior of Built-Up Welded Beams of Commercially Pure Titanium

In this article, the results of a recent study aimed at evaluating, understanding, and rationalizing the extrinsic influence of fatigue loading on the response characteristics of built-up welded beams made from commercially pure titanium (Grade 2) are presented and discussed. The beams were made from welding plates and sheets of titanium using the pulsed gas metal arc welding technique to form a structural beam having an I-shaped cross section. The welds made for the test beams of the chosen metal were fillet welds using a matching titanium filler metal wire. The maximum and minimum load values at which the built-up beams were cyclically deformed were chosen to be within the range of 22-45% of the maximum predicted flexural static load. The beams were deformed in fatigue at a stress ratio of 0.1 and constant frequency of 5 Hz. The influence of the ratio of maximum load with respect to the ultimate failure load on fatigue performance, quantified in terms of fatigue life, was examined. The percentage of maximum load to ultimate load that resulted in run-out of one million cycles was established. The overall fracture behavior of the failed beam sample was characterized by scanning electron microscopy observations to establish the conjoint influence of load severity, intrinsic microstructural effects, and intrinsic fracture surface features in governing failure by fracture.

Optimal Design of Friction Stir Welding Process to Improve Tensile Force of the Joint of A6005 Extrusion

An aluminum alloy is widely used in various fields of industries such as aerospace, shipbuilding, automotive, and railway vehicles, and gas metal Arc Welding (GMAW) technique has been applied to make the aluminum products. Recently, friction stir welding (FSW) method was developed and known to have many benefits compared to the classical GMAW technique. In this study, three important welding parameters of FSW process including the rotating speed, welding speed, and tilting angle are optimized to increase the tensile force of the joints of friction stir welded A6005 alloy. The objective function is estimated according to the response surface analysis method, and the optimum values of the design parameters are determined by using Sequential Quadratic Programming (SQP) algorithm. The optimization results are verified by comparing the tensile force of FSW specimens before and after optimization.

Recent developments in high productivity pipeline welding

Installation of new pipelines is predicted to grow at a rapid rate over the next twenty years, due in part to the increase use worldwide of combined cycle power generation plant using natural gas a fuel. The need to construct large diameter pipelines over long distances has led to an increased demand to improve the productivity of pipeline girth welding. Many novel techniques have been tried in the past to achieve productivity gains, including laser welding, flash butt welding, homopolar welding, and radial friction welding. In spite of the failure to gain wide acceptance, there is still current development aimed at achieving their eventual implementation. Single wire mechanised gas metal arc welding (GMAW) remains the dominant pipe girth welding technique, and has been optimised in the past to produce the maximum productivity possible with this process. Continued development of GMAW with dual torch, tandem GMAW welding and novel techniques for GMAW roots is leading to further significant gains in arc welding productivity. This paper describes a new development, the CAPS project, (Cranfield Automated Pipe-welding System), where tandem GMAW in a narrow groove has been applied to pipeline girth welding with two tandem torches in a single welding head. The CAPS system offers welding productivity three to four times higher than that possible with the conventional single wire GMAW technique, while still producing a weld which is very similar to that generated by single wire welding. The development of the system is described, as well as recent successful trials under field conditions. The development of high power lasers has spurred a current high level of interest in the possibility of application to pipeline welding, and current research is described in which the feasibility of pipeline laser welding has been established.