Metal Arc Welding Research Articles

An outlook on comparison of hybrid welds of different root pass and filler pass of FCAW and GMAW with classical welds of similar root pass and filler pass

In the present study, gas metal arc welding and flux cored arc welding were applied on SA516 Gr70 carbon steel material. Two different hybrid passes were applied, wherein flux cored wire and solid wire were applied to root pass and filler pass one by one and vice versa. Besides, two more welds of similar electrode root pass and filler pass of flux cored arc welding and gas metal arc welding were acquired. The comparative analysis was carried out in terms of macrostructure and microstructure examination, tensile testing, hardness variations, and impact testing for these classical welds and hybrid welds. The results reveal that, hybrid welds lead to better impact properties relative to classical welds. Maximum angular distortion of 2.66° was reported with classical weld of gas metal arc welding with solid wire root pass and same filler pass. The maximum impact toughness of 49 J/m3 was reported for flux cored root pass and solid wire filler pass at the weld zone. Maximum tensile strength of 596 MPa was reported for hybrid weld of solid root pass and flux cored filler pass. Microstructures are reported with the presence of different acicular ferrite and grain boundary ferrite. Maximum acicular ferrite of 61% was reported with classical weld of flux cored arc welding.

Influence of SC-HAZ microstructure on the mechanical behavior of Si-TRIP steel welds

Transformation induced plasticity (TRIP) steel provides enormous potential for auto-body construction in the automotive sector, owing to its enhanced mechanical behavior. In this work, Si-alloyed TRIP steel is joined by employing laser beam welding (LBW) and by utilizing two arc welding processes: gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) in order to assess the effect of the net heat input on the microstructure, the uniaxial tensile properties and the forming response. Results indicate that in spite of the Si content in TRIP steel; precipitation and growth of carbides (tempering) are observed in both: the martensite islands and the retained austenite phase, thus leading to the measurable softening at the sub-critical heat affected zone (SC-HAZ) of the arc welded samples. Although the failure location was predominantly found at the sub-critical heat affected zone of the GMAW samples, the maximum stress and elongation was basically controlled by the total extension of the weldment including fusion zone and heat affected zone. While the limiting dome height upon tension-tension (T-T) and tension-compression (T-C) depended primarily on the fusion zone hardness, weld width and geometry of the sample; the fracture location was outside the weld for T-C, whereas the fracture initiated at the weld in T-T samples. LBW specimens showed optimum forming performance.

Weld quality and productivity of AISI 4140 steel welded by unpulsed and pulsed GMAW

Abstract In this study, AISI 4140 steel couples 10 mm in thickness were joined using manual gas metal arc (GMAW) and synergic controlled pulsed gas metal arc (GMAW-P) welding methods. Interfacial images of welded samples were investigated using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) methods. Impact and microhardness tests were performed to determine the mechanical properties of the joined parts. In addition, the fracture surface of the broken joint with the impact test was examined using SEM. The AISI 4140 welded joints obtained by the GMAW-P method showed higher impact strength, less grain growth and narrower heat affected zone (HAZ) than by using the GMAW method. It is thought that this is caused by lower heat input.

Fabrication and Characterization of Weldments AISI 304 and AISI 316 Used in Industrial Applications

Gas tungsten arc welding (GTAW) and Shield metal arc welding (SMAW) are processed by using E347-16 electrode and filler wire to prepare the dissimilar weldments. The aim of study was to measure the effect of welding parameters: current, voltage, gas flow rate, nozzle to plate distance on tensile strength (TS), grain structure and hardness. The arc voltage and welding current was selected as 40,60 and 80V and 30,45 and 60amp respectively. The welding speed was selected as 4, 8, 12cm/sec. There is zero cracks, porosity, blow holes, spatter found in welding process of plate no. 2(AISI 304 &AISI 316 with ER-309L) using non consumable tungsten electrode with argon gas and also the microstructure study shows that the welding is self cooled welding structure with fine austenitic structure and very little heat affected zone found in this process. TIG welded dissimilar joint has best joint strength, uniform hardness variation as well as joint integrity.

Study on Arc Welding Processes for High Deposition Rate Additive Manufacturing

Although Additive Manufacturing implementation is rapidly growing, industrial sectors are demanding an increase of manufactured part size which most extended processes, such as Selective Laser Melting (SLM) or Laser Metal Deposition (LMD), are not able to offer. In this sense, Wire-Arc Additive Manufacturing (WAAM) offers high deposition rates and quality without size limits, becoming the best alternative for additive manufacturing of medium-large size parts with high mechanical requirements such as structural parts in the aeronautical industry.WAAM technology adds material in form of wire using an arc welding process in order to melt both the wire and the substrate. There are three welding processes that are mainly used in WAAM: Plasma Arc Welding (PAW), Gas Tungsten Arc Welding (GTAW or TIG) and Gas Metal Arc Welding (GMAW or MIG). This paper studies these processes regarding on their capabilities for additive manufacturing and compares the mechanical properties obtained by the different welding technologies applied in WAAM. Obtained results show the applicability of the technology as an alternative of traditional metallic preforms manufacturing processes, such as casting or forging.

ДЕФОРМАЦИЯ ВНЕШНЕГО МАГНИТНОГО ПОЛЯ ПРИ ДУГОВОЙ СВАРКЕ МАГНИТНЫХ МЕТАЛЛОВ

ДЕФОРМАЦИЯ ВНЕШНЕГО МАГНИТНОГО ПОЛЯ ПРИ ДУГОВОЙ СВАРКЕ МАГНИТНЫХ МЕТАЛЛОВ

Residual stresses in cold-wire gas metal arc welding

ABSTRACTThis work compares the welding residual stresses of the cold-wire gas metal arc welding and conventional gas metal arc welding processes. Two techniques were used to measure the residual stresses: X-ray diffraction and acoustic birefringence. The base metal used was carbon manganese steel plates of 9.5- mm thickness. The results showed that the introduction of the cold-wire tends to decrease the residual stresses, suggesting that the introduction of the cold wire decreases the amount of heat given to the base metal, and consequently lowers residual stresses.

Dissimilar welding between SAF 2507 stainless steel and Incoloy 825 Ni-based alloy: The role of microstructure on corrosion behavior of the weld metals

The effect of the filler metal type, welding process and the welding pass number on the corrosion behavior of Incoloy 825 Ni-based alloy to SAF 2507 super duplex stainless steel weld zones were addressed utilizing scanning electron microscopy, cyclic potentiodynamic polarization and electrochemical impedance spectroscopy. The results detailed the formation of some secondary phases in the weld metals. The welds employing Ni-based filler wires revealed the highest general corrosion resistance, while super duplex stainless steel weld metals displayed the best pitting corrosion behavior. Pulsed current gas tungsten arc welding and super duplex stainless steel filler metal were recommended to obtain the optimum surface corrosion resistance.

Metal arc welding and the risk of skin cancer

ObjectivesArc welding produces the full spectrum of ultraviolet radiation and may be a contributory cause of skin cancer; however, there has been little research into this occupational hazard. The aim of this study is to explore if metal arc welding increases the risk of malignant melanoma and/or basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) on skin areas which may possibly be exposed (neck, head, and upper extremities).MethodA Danish national company-based historic cohort of 4333 male metal arc welders was followed from 1987 through 2012 to identify the risk of skin cancer. An external reference group was established including all Danish skilled and unskilled male workers with similar age distribution. Occupational histories were gathered by questionnaires in 1986 and information about skin cancer diagnoses [BCC, SCC, cutaneous malignant melanoma (CMM), and precancerous conditions, actinic keratosis (AK)] were gathered from the Danish Cancer Registry supplemented by the data from the Danish Pathology Register. Hazard ratios (HRs) were calculated in the follow-up period from 1987 until 2012 using Cox regression analysis and adjusted for baseline data regarding age and social group.ResultsThe adjusted HR and 95% confidence interval (CI) for skin cancer (all types) were 0.99 (CI 0.94–1.04) for welders. The adjusted HR for AK and BCC located only at neck was 2.49 (CI 1.03–5.99) for welders exposed >20 years (n = 5) and 2.46 (CI 1.02–5.94), respectively, for welders exposed >30 years (n = 5). No statistically significant difference was observed for SCC. The risk of CMM at the neck was also significantly elevated after 30 years of welding, but this is based upon only one exposed case.ConclusionThis study indicates that long-term exposure to metal arc welding may be related to increased risk of BCC and AK located exclusively at the neck. The study provides no support for the hypothesis that welding exposure increases the risk for skin cancer at other locations.

Effect of TIG Welding and Manual Metal Arc Welding on Mechanical Properties of AISI 304 and 316L Austenitic Stainless Steel Sheets

The welding technique used for ASIS 304 and 316L austenitic stainless steel sheets both with a thickness of 3mm is gas tungsten arc welding (TIG) and manual metal arc welding (MMAW). Mechanical properties that were verified include: hardness test and tensile test before welding and after it. The welding process was done on two types of specimens: with a central hole and without hole. We concluded that there was a decrease in the properties of tensile for both specimens with central hole, and 316L had tensile characteristics better than 304 when using the technique TIG. As for 304, it had tensile characteristics better than 316L when using the technique MMAW. We also concluded that the existence of central holes had an influence on the hardness characteristics on both types. The hardness increased in 304 but decreased in 316L. The welding process also showed that there was no influence of MMAW on hardness on both specimens. However it showed that there was no influence of TIG on the hardness for 304, but for 316L values increased.

Repair Welding of the Massive Cast

Abstract The rebuilding technologies are used to develop surface of ladle. Among many welding methods currently used to obtain surface layer without defects one of the most effective way of rebuilding is using metal arc welding. This additional material gives more possibilities to make expected quality of rebuild surface. Chemical composition, property and economic factors allow to use metal wire. Because of these reasons, solid wire gives opportunity to be wildly used as material to rebuild or repair the surface in different sectors of industry. The paper shows a few ways to rebuild the surface in the massive cast with the use of metal active gas welding for repair. The work presents studies of defect in the massive cast. It contains the pictures of microstructures and defects. The method of removing defects and the results of checking by visual and penetrant testing methods are shown. The paper describes the methodology of repair the ladle with metal active gas welding, preheating process and standards nondestructive testing method.

Influence of shot peening and thermal ageing treatment on resistance to intergranular corrosion in shielded metal arc weld metal for type 600 nickel base alloy

Shielded metal arc weld metal for type 600 nickel base alloy (alloy 182) is used for weld components in nuclear power plants. To evaluate the intergranular corrosion resistance of alloy 182 after application of shot peening and subsequent thermal ageing treatment at 593–793 K, we conducted the corrosion test (immersed in boiled 16% sulphuric acid +5.7% copper sulphate aqueous solution at 57.6 ks) using specimens of alloy 182. The results show that the intergranular corrosion resistance of alloy 182 subjected to heat treatment at 893 K for 72 ks was improved by shot peening. Also, the intergranular corrosion resistance was not changed by thermal ageing treatment at 593–793 K subsequent to shot peening. Because remaining chromium depletion layers along grain boundaries were still observed by transmission electron microscope (TEM) after shot peening, disappearance of chromium depletion layers cannot be a factor in the improvement of the intergranular corrosion resistance. The results of measurement of surface residual stress by the X-ray diffraction method show that the compressive residual stress introduced by shot peening still remained on the surface of the specimens. Based on these observations, we assumed that chromium depletion layers along grain boundaries near the surface were dissolved by the environment of the corrosion test, the dissolved regions were closed by the compressive residual stress on the surface, and then the remaining chromium depletion layers were protected from the corrosive environment. This assumption explains why the intergranular corrosion resistance was improved although chromium depletion layers remained.

Evaluation of the AISI 904L Alloy Weld Overlays Obtained by GMAW and Electro-Slag Welding Processes

The use of superaustenitic stainless steels (SASS) as an overlay replacement for nickel-based alloys can be an interesting alternative for the oil and gas industries, due to its lower cost, when compared to superalloys. Usually, the deposition is made with several welding passes by using conventional arc welding processes, such as gas tungsten arc welding (GTAW) or gas metal arc welding (GMAW) processes. In this respect, electro-slag welding (ESW), which promotes high heat inputs and low dilution of the welds, can also be attractive for this application, as it provides a higher productivity, once only one layer is needed for the deposition of the minimum thickness required. The present work evaluates the behavior of an AISI 904L SASS weld overlay deposited on a carbon steel ASTM A516 Grade 70 by ESW and GMAW processes. Both as-welded and heat-treated conditions were evaluated and compared. A multipass welding by GMAW process with three layers and 48 passes was performed on 12.5 × 200 × 250 mm steel plates with average welding energy of 1.0 kJ/mm. For ESW process, only one layer was deposited on 50 × 400 × 400 mm steel plates with average welding energy of 11.7 kJ/mm. After welding, a post-weld heat treatment (PWHT) at 620 °C for 10 h was performed in half of the steel plate, in order to allow the comparison between this condition and the as-welded one. For both processes, the austenitic microstructure of the weld deposits was characterized by optical microscopy and scanning electron microscopy with electron backscatter diffraction. A low proportion of secondary phases were observed in all conditions, and the PWHT did not promote significant changes on the hardness profile. Martensite for GMAW process and bainite for ESW process were the microstructural constituents observed at the coarse grain heat-affected zone, due to the different cooling rates. For ESW process, no evidences of partially diluted zones were found. As a consequence of the microstructural findings, the hardness results for ESW were lower than those usually observed for other electric arc welding processes. In addition, specimens subject to bending tests performed in accordance with the current standards used for qualification of welding procedures were approved. These evidences allow the conclusion that the ESW process can provide deposits with high quality despite the high welding energy levels, in order to achieve the desired productivity, being an interesting alternative for AISI 904L weld overlays.

Comparative Studies on Metallurgical and Mechanical Properties of Bimetallic Combination on Incoloy 800 and SS 316L Fabricated by Gas Metal and Shield Metal Arc Welding

The needs of the dissimilar weld joint between superalloy and stainless steel is increasing in many industries. Gas tungsten arc welding (GTAW) and shield metal arc welding (SMAW) are the most common methods used to fabricate the weld joints in the fabrication industry due to its high versatility in the fabrication of industrial components and parts. The present study investigated the metallurgical and mechanical properties of bimetallic joints fabricated between nickel-based superalloy Incoloy 800 and stainless steel AISI 316L. The weld joints were fabricated by using ERNiCrMo-3 filler wire. The micrograph of weld fusion zone revealed the austenitic microstructure with columnar dendrite and cellular structure in both weldments. SEM/EDS analysis witnessed the precipitation of Nb-rich phase in the weld fusion zone fabricated by SMAW process, and it was minimized in case of GTA welding technique. The strength and toughness of the weld joint fabricated by GTAW improved 14 and 25% respectively when compared to SMAW technique.

Effects of Zr-Ti on the microstructure and properties of flux aided backing submerged arc weld metals

Zr-Ti alloy powders were added into the weld groove to join D36 steel by using flux aided backing submerged arc welding (FAB-SAW). The inclusions, microstructure and mechanical properties of Zr-Ti miroalloyed weld metals were investigated. The results showed that the core of inclusions was composed of Zr, Al, Ti, Si, Mn oxides, while the surface layer of inclusions was composed of TiO (or Ti2O3), ZrO2 and MnS. The first precipitated ZrO2 can act as nucleation sites for Al, Ti, Si, Mn oxides and increases the fraction of inclusions with size of smaller than 1.0 μm. Due to the refined size and increased density of inclusions, the proportion of acicular ferrite (AF) was significantly increased while the proportion of grain boundary ferrite (GBF) and ferrite side-plate (FSP) were remarkably decreased in the microstructure. The tensile properties and impact toughness at −20 °C of weld metal were obviously promoted. The nucleation of AF was ascribed to the low lattice misfit between TiO (and ZrO2) and α-Fe as well as a high inert interfacial energy of MnS. When the content of Zr was 0.09 wt %, the percentage of AF in FAB-SAW weld metal was reached to 82%, resulting in the weld metal with elongation of 25%, ultimate strength of 615 MPa and impact energy at −20 °C of 145 J.

Three-dimensional cellular automaton-finite element modeling of solidification grain structures for arc-welding processes

Solidification grain structure has significant impact on the final properties of welded parts using fusion welding processes. Direct simulation of grain structure at industrial scale is yet rarely reported in the literature and remains a challenge. A three-dimensional (3D) coupled Cellular Automaton (CA) – Finite Element (FE) model is presented that predicts the grain structure formation during multiple passes Gas Tungsten Arc Welding (GTAW) and Gas Metal Arc Welding (GMAW). The FE model is established in a level set (LS) approach that tracks the evolution of the metal-shielding gas interface due to the addition of metal. The FE method solves the mass, energy and momentum conservation equations for the metal plus shielding gas system based on an adaptive mesh (FE mesh). Fields are projected in a second FE mesh, named CA mesh. A CA grid made of a regular lattice of cubic cells is created to overlay the fixed CA mesh. The CA model based on the CA grid simulates the melting and growth of the grain boundaries in the liquid pool. In order to handle large computational domains while keeping reasonable computational costs, parallel computations and dynamic strategies for the allocation/deallocation of the CA grid are introduced. These strategies correspond to significant optimizations of the computer memories that are demonstrated. The 3D CAFE model is first applied to the simple configuration of single linear passes by GTAW of a duplex stainless steel URANUS 2202. It is then applied to a more persuasive example considering GMAW in spray transfer mode during multiple passes to fill a V-groove chamfer. Simulations reveal the possibility to handle domains with millions of grains in representative domain sizes while following the formation of textures that result from the growth competition among columnar grains.

Experimental determination of TRIP-parameter K for mild- and high-strength low-alloy steels and a super martensitic filler material.

A combined experimental numerical approach is applied to determine the transformation induced plasticity (TRIP)-parameter K for different strength low-alloy steels of grade S355J2+N and S960QL as well as the super martensitic filler CN13-4-IG containing 13 wt% chromium and 4 wt% nickel. The thermo-physical analyses were conducted using a Gleeble® 3500 facility. The thermal histories of the specimens to be tested were extracted from corresponding simulations of a real gas metal arc weldment. In contrast to common TRIP-experiments which are based on complex specimens a simple flat specimen was utilized together with an engineering evaluation method. The evaluation method was validated with literature values for the TRIP-parameter. It could be shown that the proposed approach enables a correct description of the TRIP behavior.

Corrosion behaviour of 304LN activated tungsten inert gas and flux-cored arc weld metals

Activated tungsten inert gas (A-TIG) and flux-cored arc (FCA) weld metals were prepared using 304LN stainless steel plate. The weld metals were thermally aged at 923, 973 and 1023 K for 100 h to study the decomposition of initial δ-ferrite in A-TIG (∼10 ferrite number (FN)) and FCA (∼5 FN) weld metals into secondary phases like M23C6 carbides, χ and σ. Ferrite number is the measurement of δ-ferrite based on the principle of magnetic property using ferritescope. Preliminary microstructural studies revealed the formation of carbides in FCA weld metals aged at 923 K for 100 h, which was correlated with higher carbon content (0.04 wt-%), and also ageing at higher temperature transformed δ-ferrite into χ/σ phases. However, A-TIG weld metals showed the transformation of δ-ferrite mainly into χ/σ phases. The δ-ferrite transformation kinetics was found to be sluggish in A-TIG weld metals compared to FCA weld metals. This difference was attributed to the difference in the carbon contents of A-TIG and FCA welds. Activated tungsten inert gas weld metals showed better uniform and pitting corrosion resistance compared to FCA weld metals in as-deposited and thermally aged conditions. Presence of higher amount of initial δ-ferrite content in A-TIG weld metal helped diffusion of minor alloying elements like sulphur and phosphorous into it, thereby reducing their microsegregation at the δ/γ interface boundaries and subsequent pitting corrosion attack. Thus, A-TIG welding process was found to be superior compared to FCA welding process.

Methodology for Estimating Thermal and Neutron Embrittlement of Austenitic Stainless Steel Welds During Service in Light Water Reactors

The effect of thermal aging on the degradation of fracture toughness and Charpy-impact properties of austenitic stainless steel (SS) welds has been characterized at reactor temperatures. The solidification behavior and the distribution and morphology of the ferrite phase in SS welds are described. Thermal aging of the welds results in moderate decreases in Charpy-impact strength and fracture toughness. The upper-shelf Charpy-impact energy of aged welds decreases by 50–80 J/cm2. The decrease in fracture-toughness J integral-resistance (J-R) curve or JIc is relatively small. Thermal aging has minimal effect and the welding process has a significant effect on the tensile strength. However, the existing data are inadequate to accurately establish the effect of the welding process on fracture properties of SS welds. Consequently, the approach used for evaluating thermal and neutron embrittlement of austenitic SS welds relies on establishing a lower-bound fracture-toughness J-R curve for unaged and aged and nonirradiated and irradiated SS welds. The existing fracture-toughness J-R curve data for SS welds have been reviewed and evaluated to define lower-bound J-R curves for submerged arc (SA)/shielded metal arc (SMA)/manual metal arc (MMA) welds and gas tungsten arc (GTA)/metal inert gas (MIG)/tungsten inert gas (TIG) welds in the unaged and aged conditions. At reactor temperatures, the fracture toughness of GTA/MIG/TIG welds is a factor of about 2.3 higher than that of SA/SMA/MMA welds. Thermal aging decreases the fracture toughness of all welds by about 20%. The potential combined effects of thermal and neutron embrittlement of austenitic SS welds are also described. Lower-bound curves are presented, which define the change in coefficient C and exponent n of the power-law J-R curve and the JIc value for SS welds as a function of neutron dose. The potential effects of reactor coolant environment on the fracture toughness of austenitic SS welds are also discussed.

Comparative study on interactions between laser and arc plasma during laser-GTA welding and laser-GMA welding

This paper describes an investigation on differences in interactions between laser and arc plasma during laser-gas tungsten arc (LT) welding and laser-gas metal arc (LM) welding. The characteristics of LT heat source and LM heat source, such as plasma behavior, heat penetration ability and spectral information were comparably studied. Based on the plasma discharge theory, the interactions during plasma discharge were modeled and analyzed. Results show that in both LT and LM welding, coupling discharge between the laser keyhole plasma and arc happens, which strongly enhance the arc. But, the enhancing effect in LT welding is much more sensitive than that in LM welding when parameters are adjusted.