Flux Cored Arc Welding Research Articles

Microstructure and mechanical properties of FCTIG-welded DH36 steel with rutile-type and basic-type flux cored wires

Using basic-type flux cored wires significantly improve the toughness of weld joints, but the addition of fluoride decreases the weld-ability of the metal. In this paper, the flux cored tungsten inert gas (FCTIG) process was used to weld DH36 steel with a basic-type flux cored wire and a rutile-type flux cored wire. The microstructure and mechanical properties of the wires were investigated as well as the diffusible hydrogen content in the different weld joints. The results indicated that the FCTIG process using a basic-type flux cored wire has more technological advantages and produces lower amounts of fume during welding compared with flux cored arc welding (FCAW). The presence of large amounts of alloying elements in the rutile-type flux cored wire promoted the formation of acicular ferrite (AF) in the weld bead, which enhanced the micro-hardness and strength of the bead. The generation of fluoride with the basic-type flux cored wire reduced the diffusible hydrogen content (DHC) in the weld joint, with the lowest DHC value being 3.18 mL/100 g. The toughness of the weld joint made with the basic-type flux cored wire was improved, and the highest impact energy measured was 264.8 J.

Abrasive Wear Behavior and Its Relation with the Macro-indentation Fracture Toughness of an Fe-Based Super-Hard Hardfacing Deposit

In this study, flux-cored arc welding was performed to deposit an Fe-based super-hard hardfacing whit 911 HV30 on an st37 substrate. The dry sand/rubber wheel abrasion test (ASTM G65) was performed to investigate the abrasive wear behavior of the hardfacing deposit and its average weight loss was measured to be 0.075 gr. The worn surface and cross sections of wear sample were studied by optical microscopy and scanning electron microscopy. The results showed that the fracture behavior of the phases during abrasion testing is similar to their fracture behavior during macro-indentation fracture toughness testing investigated in the previous study (Bahoosh et al. in Eng Fail Anal 92:480–494, https://doi.org/10.1016/j.engfailanal.2018.06.021 , 2018). Consequently, the micro-mechanisms of abrasion resistance associated with the fracture behavior of the phases such as the fragmentation of the primary $${\text{M}}_{7} \left({\text{CB}} \right)_{3}$$ in the preferred direction and higher abrasion resistance of the core–rim-structured phases were determined.

Influence of FCAW process parameters in super duplex stainless steel claddings

Flux cored arc welding (FCAW) is preferred in cladding process due to its augmented efficiency and higher deposition rate. In this research work, to investigate the interaction effect between process parameters of flux cored arc welding on hardness and bead geometry of cladded plate on super duplex stainless steel. The hardness values got increased for the maximum wire feed rate and maximum welding speed, this is due to the dilution rate of the feed wire and also the bead width and bead height got improves for the minimum wire feed rate and minimum welding speed.

Effects of the welding processes and consumables on the fatigue and fracture performances for 3.5 wt.% nickel steels

Ethylene based on ethane gas in petrochemical products has a great economic advantage. Ethane gas can typically be liquefied by cooling to − 95 °C for more efficient transportation. To ensure the structural integrity of very large ethane gas carriers, ethane gas storage tanks are fabricated using materials that exhibit excellent fatigue and fracture performances at cryogenic temperatures, such as SUS304L, Invar alloys, Al 5083-O, high-manganese steels, and nickel steels. This study compared the fatigue and fracture performances of 3.5-wt.% nickel steels considering the welding processes and consumables. To compare the fatigue and fracture performances of 3.5-wt.% nickel steels, three different welding consumables were used for the weld metals with flux core arc welding and flux core arc welding + submerged arc welding. Fatigue and fracture tests with various nickel alloy steels were conducted according to ASTM E647 and ISO 12135, respectively. The mechanical properties with flux core arc welding + submerged arc welding were higher than those with flux core arc welding. In the case of the fracture toughness, the crack tip opening displacement values with flux core arc welding were approximately 45 and 18% lower than those with flux core arc welding + submerged arc welding at room and low temperatures (173 K), respectively. With a fixed slope of 3.0 and a material constant, C, the associated fatigue crack growth rate of the heat-affected zone with flux core arc welding was higher than that in the weld metal. In addition, the fatigue crack growth threshold values of the weld metal were higher than those of the heat-affected zone. The fatigue and fracture performance of various nickel alloy steels was explained in terms of the microstructure of weld metals.

Comparative life cycle assessment of metal arc welding technologies by using engineering design documentation

The paper aims to analyze and compare the environmental performances of metal arc welding technologies: gas metal arc welding (GMAW), shielded metal arc welding (SMAW), gas tungsten arc welding (GTAW), submerged arc welding (SAW), and flux-cored arc welding (FCAW). Welding is considered one of the most energy-intensive processes in manufacturing. This study was performed in accordance with the international standard ISO 14040/14044 by using attributional life cycle assessment (aLCA). The functional unit is defined as the “the development of 1 metre of welding seam (qualified by ASME section IX requirements) to join 25 millimetres thick of metal plates made in carbon steel material and considering a V-bevel configuration.” Different configurations of base/filler materials and standardized bevel geometries have been analyzed as welding scenarios. The inventory considers all inputs (e.g., electric energy and filler material) and outputs (e.g., fume emissions and slags) involved in each welding process. A framework for data collection starting from available project documentation is presented as an innovative solution for the inventory phase. The impact assessment includes the human health, resources (midpoints/endpoint), and ecosystems (endpoint) categories from the ReCiPe (H) and cumulative energy demand (CED) methods. This study reveals a notable dominance in terms of the environmental burdens of GTAW and SMAW processes, as they present higher impacts in most of the impact categories. SMAW is the most energy-consuming process, and this aspect is reflected in the environmental performance. Conversely, GMAW presents the least environmental load, accounting for less than one third compared with GTAW in terms of the CED indicator and performing very well in terms of the ReCiPe endpoint indicator. Via analysis of different scenarios, the main outcomes are the following: (i) the use of V bevels significantly increases the environmental load when the metal plate thickness increases and (ii) the use of specific materials such as Inconel alloy exacerbates the environmental concerns associated with welding processes. The use of project documentation allows robust analysis of welding activity. Sensitivity analysis shows how the range of values for specific parameters (e.g., volts and amps) affects each technology in a different manner. Indeed, those ranges have a limited impact on the result accuracy (up to 20%) for more automatized welding processes (e.g., GMAW, SAW, and FCAW), in which only a small number of parameters are set by the operator, and the operator skills are less influential on the quality of the weld.

Occupational survey of airborne metal exposures to welders, metalworkers, and bystanders in small fabrication shops

The objective of this study was to characterize worker exposure to airborne metal and particulate matter in shops where multiple types of metalworking tasks were performed. The sampling strategy included full-shift and task-based personal samples on workers who performed flux-cored arc welding, personal samples on workers performing non-welding metalworking tasks, and area samples near welders, representing bystanders to welding. Size-fractionated particulate matter adjacent to welding activities was measured using real-time monitoring devices. Samples were analyzed for 21 individual metals, of which 8 were frequently detected. Exceedance fractions were calculated based on the distribution of results for each frequently detected metal. Exceedance fractions were <5% for all metals, except manganese (6% of the REL, 55% of the inhalable TLV-TWA and 91% of the respirable TLV-TWA) and iron oxide (10% of the REL and TLV-TWA) for Shop 1 bystander samples, manganese (68% for the inhalable TLV-TWA and 98% of the respirable TLV-TWA) for welder samples, and manganese (35% for the inhalable TLV-TWA and 80% of the respirable TLV-TWA) and iron oxide (12% for the PEL and 23% for the REL and TLV-TWA) for metalworker samples. Particulate matter concentrations measured at distances of 0.9–1.5 m and 2.1–2.7 m from the welder were within the same order of magnitude. The results of this study allow for comparison to health-based exposure limits for select individual components of welding fume with a low to medium degree of censorship.

Weldability and Lamellar Tearing Susceptibility of High-Strength SN 490C Steel Plates

In this study, weldability and cracking susceptibility of SN 490C steel were firstly investigated. For this study, SN 490C thick plates which had been developed for anti-seismic steel of building structures were welded by flux-cored arc welding (FCAW) and submerged arc welding (SAW) processes based on welding conditions of actual construction site. Weldments using the plates with different thickness were produced using E71T-1C and EH14 filler wires, respectively. For the weldability tests, various welded joints such as butt and T-joints were examined. After welding, microstructure analysis was performed. Various microstructures were found depending on the location of the weldments. Heat effects by multi-pass welding were correlated with the microstructure. The microstructure was correlated with the hardness profile and the impact test result. In addition, the through-thickness tensile test, window test, and Cranfield test were conducted to evaluate sensitivity of lamellar tearing, which may occur during tensile restraint stress of welds. As a result of the tests, it was found that the SN 490C steel was sufficiently resistant to lamellar tearing.

Arc stability indexes evaluation of ultrasonic wave-assisted underwater FCAW using electrical signal analysis

Ultrasonic wave-assisted underwater flux-cored arc welding (FCAW) has the potential to control the dynamic bubble and then improve arc stability. In this study, the four indexes evaluation methods to determine arc stability, i.e., oscillograms, cyclograms, probability distribution, variation coefficients of the welding current and arc voltage, were conducted to study the effect of ultrasonic wave on the arc stability. Results show that it is reasonable to evaluate the variation in arc stability with the welding parameters including wire feed speed and arc voltage, or without/with an ultrasonic wave by using the four indexes evaluation methods. Further, the control of the dynamic bubble induced by the exertion of ultrasonic wave can be used to explain why the arc stability is improved. The key points to excellent arc stability depend on both the designation of the welding parameters and reasonable control of the bubble with structural integrity. Therefore, through the novel method which combines optimized welding parameters with a stable bubble environment, the achieved welding process can effectively reduce the bubble disturbance and enhance the arc stability. Results presented in the paper aim to understand the combined influence mechanism of welding parameters and ultrasonic wave on the arc stability in underwater wet welding.

Welding Residual Stress Effect in Fracture Toughness.

The thickness of steel plates used for large structures has been increasing with the rapid increase in the size of welding structures. The growing capacity of large-scale ships, such as container ships, has led to an increase in the thickness and strength of steel plates for shipbuilding. The steel plate toughness and resistance to brittle fractures tend to decrease for thick plates because of the so-called thickness effect. This study uses 80-mm-thick steel plates and two welding processes (i.e., flux cored arc welding process and electron gas welding process) to produce full-thickness weld joints. The welding residual stress in both welded joints is measured to evaluate the brittle crack propagation path. This study aims to investigate the effect of welding variables on the crack arrest toughness and crack propagation path of thick steel-plate welds. The thick steel plate has a high possibility in brittle fracture. A quantitative analysis is conducted through a temperature-gradient ESSO test to clarify the effect of the welding variables on the flux cored arc welding and electron gas welding process joints of steel plates with 50 and 80 mm thicknesses. The welding residual stress is also measured to evaluate the welding residual stress effect in both welding processes on the brittle crack propagation path using a neutron science analysis.

Clearance for Welded Joints

Inadequate clearance can affect weld quality and efficiency. In extreme cases, obstructions may cause a lack of fusion between the base metal and the weld metal, causing a reduction in strength. Although flux cored arc welding (FCAW) and gas metal arc welding (GMAW) have replaced shielded metal arc welding (SMAW) as the primary fabrication processes for structural steel fabrication, existing clearance recommendations are based on the SMAW process. Because the geometry of a FCAW or GMAW welding gun is much different from that of a SMAW electrode, the historic values recommended for the SMAW process may not apply to FCAW and GMAW. Experimental specimens were fabricated with the FCAW process to determine practical limits on connection geometry for welding joints with limited access. Each specimen was evaluated by sectioning and etching the weld at two locations along the length. Two weld clearance issues are addressed: (1) fillet welding near obstructions and (2) doubler plate welds.

Modelling of exposure to respirable and inhalable welding fumes at German workplaces

The International Agency for Research on Cancer classified welding fumes as carcinogenic to humans, and occupational exposure limits should be established to protect welders. The aim of this study is to estimate exposure levels to inhalable and respirable welding fumes by welding process to use them for exposure assessment in epidemiological studies and to derive occupational exposure limits. In total, 15,473 mass concentrations of inhalable and 9,161 concentrations of respirable welding fumes could be analyzed along with welding-related and sampling information, which were compiled in the German database MEGA between 1983 and 2016. In both particle-size fractions, model-based geometric means of the concentrations were estimated by welding process and material for frequently used welding processes adjusted for sampling time and median-centered for calendar years. The inhalable concentrations were approximately twice the respirable concentrations, with medians of 3 mg/m3 (inter-quartile range: 1.2–7.0 mg/m3) and 1.5 mg/m3 (inter-quartile range: < limit of detection −3.8 mg/m3), respectively. The adjusted geometric means of flux-cored arc welding, metal inert and active gas welding, shielded metal arc welding and torch cutting ranged from 0.9 to 2.2 mg/m3 for respirable welding fumes and from 2.3 to 4.7 mg/m3 for inhalable fumes. In both particle-size fractions, geometric means were between 0.1 and 0.9 mg/m3 when performing tungsten inert gas, autogeneous, resistance, laser, and plasma welding or spraying. Results derived from this large dataset are useful for a quantitative exposure assessment to estimate health risks of welders.

A study on process development of super-TIG welding for 9% nickel steel with Alloy 625

The demands for liquefied natural gas and 9% nickel steel tanks for its storage have increased due to stricter regulations for ship emissions. In the present study, a super-TIG welding process was developed for the butt welding of 9% nickel steel by using Alloy 625 filler metal with a C-type cross-section. The mechanical properties of the welded specimens were compared with those of flux-cored arc welding, using Hastelloy and Alloy 600 filler metals in impact and tensile tests, while the structures were examined under an optical microscope. The newly developed super-TIG welding process was shown to have an effective heat input ratio, given that hot cracking does not occur.

A New Approach to the Study of Multi-Pass Welds–Microstructure and Properties of Welded 20-mm-Thick Superduplex Stainless Steel

Type 2507 superduplex stainless steel 20 mm in thickness was multi-pass-welded with Gas Metal Arc Welding (GMAW) and Flux-Cored Arc Welding (FCAW) processes. Recommended and higher arc energies and inter-pass temperatures were used. Thermal cycles were monitored using a recently developed procedure involving the successive instrumentation of the multi-pass welds, pass by pass, by addition of thermocouples in each weld pass. The repeatability of temperature measurements and survival rate of more than 90% of thermocouples confirmed the reliability of the procedure. Reheating by subsequent passes caused a progressive increase in the austenite content of the weld metal. The as-deposited GMAW passes with higher-than-recommended arc energy showed the lowest presence of nitrides. Therefore, the cooling rate—and not the time exposed at the critical temperature range—seems to be the key factor for nitride formation. The welding sequence layout also plays an important role in the distribution of secondary phases. A larger amount and concentration of secondary austenite and σ-phase was found for a larger number of subsequent passes in the immediate vicinity of a specific weld pass. The impact toughness exceeded requirements for all welds. Differences in absorbed energies were related to the amount of micro-inclusions found with the FCAW weld showing the lowest absorbed energies and highest amount of micro-inclusions. Pitting corrosion preferentially initiated in locations with secondary austenite and σ-phase. However, in the absence of these secondary phases, the HAZ containing nitrides was the weakest location where pitting initiated. The results of this work have implications on practical welding for superduplex stainless steels: the current recommendations on maximum arc energy should be revised for large thickness weldments, and the importance of the welding sequence layout on the formation of secondary phases should be considered.

The cryogenic low-cycle fatigue performance of 9%Ni steel joint made by flux cored arc welding

Low-cycle fatigue (LCF) test was performed at 296 K and 80 K to investigate the effects of cryogenic environment on the LCF performance of 9%Ni steel joints welded by flux cored arc welding (FCAW). The test results indicated that the LCF performance in cryogenic environment was higher than that at room temperature. The gap of fatigue lifetime decreased with the increment of strain amplitude. The LCF performance at room temperature and in cryogenic environment was very close when total strain amplitude was 0.8%. The LCF specimens underwent cyclic hardening and cyclic softening before fracture at room temperature. No obvious cyclic softening was observed during LCF test at cryogenic temperature. The fracture location was at PMZ at room temperature, but at weld center in cryogenic environment. The transformation of brass texture mainly occurred in PMZ at cryogenic temperature after LCF test. The strengthening effects of brass texture in PMZ increased the stress concentration in weld center. The microvoids appeared near precipitates at grain boundaries led to the intergranular propagation of fatigue cracks in weld center. Research results contributed to safe service and fatigue lifetime estimation of LNG containers made by 9% Ni steel in cryogenic environment.

Heat Source Modeling for FCAW of Fillet Joints using Artificial Neural Networks

The present work deals with the prediction of heat source parameters of Goldak's double ellipsoidal model for flux cored arc welded fillet joints through an artificial neural network (ANN). Extensive experiments were carried out on low-carbon mild steel plates of thickness ranging from 3 mm to 10 mm. In each case, welding current (I), voltage (V), and speed (υ) were recorded as the welding parameters. The flux cored arc welding of fillet joint was carried out using 100% CO2 as the shielding gas. This work is based on the simple and fundamental presumption that the weld pool is the primary source of heat which is delivered from the welding arc. Therefore, the magnitude and distribution of heat can be defined through the weld pool dimensions. Hence, these dimensions were directly considered for determining the heat source ellipsoid parameters. These parameters, namely, front double ellipsoidal length (Cf), rear double ellipsoidal length (Cr), half-width of the heat source (a), and depth of the heat source (b) were measured from the welded specimens. Furthermore, the ANN model was trained and tested for the prediction of the heat source parameters. The ANN predicted data were in good agreement with the measured values. Subsequently, the ANN model was used to predict the parametric dimensions of the double ellipsoidal heat source model for a set of welding parameters. The temperature history numerically computed with the ANN-predicted parametric dimensions of the double ellipsoidal heat source model compared very well with the measured data. The proposed ANN structure, therefore, can be gainfully used as a tool for the prediction of parametric dimensions of the double ellipsoidal heat source model in case of gas metal arc welding with 100% CO2 as the shielding medium for a plate thickness range of 3–10 mm. 1. Introduction Flux cored arc welding (FCAW) is extensively used in various fabrication industries, including the ship building industry. It is widely used in semiautomatic mode for fabrication of, among other things, stiffened flat and curved panels. These are fabricated by butt welding of the plates followed by fillet welding of the longitudinal and transverse stiffeners. In thin panel fabrication, it may lead to weld induced buckling. Hence, to assess the possible behaviour during fabrication of the stiffened panels, numerical simulation is often carried out. The computation of temperature field is at the heart of numerical simulation of weld-induced distortion and residual stress. Thus, it is very important to have a model for accurate prediction of the temperature field. The temperature field again depends on the distribution and quantum of heat that gets delivered from the welding arc to the weld joint. This calls for developing a heat source model that represents the heat distribution and its magnitude as accurately as possible.

Application of Multiple Methods of NDT for the Evaluation of Welded Joints in a Steel Bridge ASTM-A-588

This work is based on making a comparison of different inspection methods of non-destructive testing (NDT), to detect porosity, bite, undercut, splash, overlap, slag, concavity, lack of fusion and damage to base material, in welds of shielded metal arc welding (SMAW) and flux-cored arc welding (FCAW), made on a steel bridge ASTM-A-588. The main application of non-destructive tests is to evaluate the final state of a welded joint in critical points, in addition the fundamental objective is to ensure that the established acceptance and rejection criteria are met rigorously. For which non-destructive techniques are analyzed, such as the visual testing of welding on the beams of a bridge of length 35000 mm, subsequently, tests of inspection by liquid penetrant were used, based on the AWS D1.5 standard to confirm the failures in welded joints in ABA webs, an ultrasonic is also carried out using an SIUI CTS 602 equipment, finally to issue an acceptance and rejection criterion as determined by ASTM E165 and ASTM E2544-09.

Respiratory Exposure to Toxic Gases and Metal Fumes Produced by Welding Processes and Pulmonary Function Tests.

Background: Welding is a common industrial process and is harmful to welders' health. Objective: To determine the effect of toxic gases and metal fumes produced during 3 welding processes on welders' incidence of respiratory symptoms and pulmonary function. Methods:This cross-sectional study was conducted in an Iranian shipbuilding industrial factory in 2018. Using the simple census method, 60 welders were selected as the exposed group. 45 staff members of the administrative unit were also recruited to be served as the control group. Welders' demographic data and respiratory complaints were collected employing a questionnaire. Fumes and gases produced were sampled from the welders' respiratory tract and analyzed by standard methods suggested by the National Institute of Occupational Safety and Health (NIOSH). Pulmonary function test was also performed for each participant. Results: The prevalence of respiratory symptoms in all welders was significantly (p<0.05) higher than the control group. The mean FVC, FEV1 and FEV1/FVC measured in welders involved in all 3 processes were significantly lower than those recorded in the control group. The spirometry pattern in welders involved in flux cored arc welding and shielded metal arc welding was obstructive; that in those involved in gas metal arch welding was mixed (obstructive and restrictive pattern). Conclusion: Exposure to welding fumes and gases was associated with pulmonary function deterioration. Welders involved in gas metal arch welding had a prevalence of pulmonary disorders compared with those involved in gas metal arch welding and flux cored arc welding.

Effect of Nickel on the Microstructure, Hardness and Impact Toughness of SM570-TMC Weld Metals

SM570-TMC steel was applied in the various fields of steel construction where higher strength is required than conventional mild steel. This steel is commonly fabricated by fusion welding where flux-cored arc welding (FCAW) is preferred due to efficiency consideration. In this study, 14 mm thickness of SM570-TMC steel was butt weld by FCAW using three electrode wires with different nickel content (0% Ni, 1% Ni, 1.5% Ni). The microstructure of weldments was studied using an optical microscope. The hardness distribution tests were performed in the heat affected zone, parent metal and weld metal. And impact toughness of weld metals were measured at temperatures of 25 °C, 0 °C and -20 °C. The results show the steel plate welded using welding wire containing 1% Ni provides more superior impact toughness in the weld metal than welding wire 0% Ni, while the impact toughness of the sample which welded using welding wire containing 1.5% tend to decrease. Nickel element which deposited to weld metal by using welding wires containing 1% Ni has improved the impact toughness, but 1.5% Ni may too high which deteriorate impact toughness.

Selection of Welding Process for Repairing Shredder Hammer by Integrated Data Envelopment Analysis (DEA) and P-robust Technique

The Selection of the welding process is one of the most significant decision-making problems, and it involves a wide range of information following the type of product. Hence, the automation of knowledge through a knowledge-based system will significantly enhance the decision-making process and simplify for identifying the most appropriate welding processes. The aims of this paper for explicates a knowledge-based system developed for recognising the most suitable welding processes for repairing shredder hammer by using data envelopment analysis (DEA) and p-robust technique. The proposed approach is used for ranking six welding processes which are commonly used, namely shielded metal arc welding (SMAW), flux cored arc welding (FCAW), submerged arc welding (SAW), oxyacetylene gas welding (OAW), gas tungsten arc welding (GTAW), and gas metal arc welding (GMAW). In order to determine the best welding process among competitive welding processes for repairing of shredder hammer, ten parameters are used, namely the availability of consumable, welding process type (manual and automatic), flexibility of welding position, weld-ability on base metal, initial preparation required, welding procedures, post-weld cleaning, capital cost, operating factor, and deposition rate. Furthermore, the sensitivity analysis of regret value (p) is investigated in three cases proposed.

Influence of Boron and Manganese on Hot Crack Resistance and Low Temperature Toughness of Flux Cored Arc Weld Metal for High Strength Carbon Steels

The hot crack resistance and mechanical properties of flux cored arc (FCA) welds were investigated with three kinds of welding consumables having different boron (B) and manganese (Mn) contents for high strength carbon steel. The hot crack resistance, measured from self-restraint testing, strongly depended on the amount of B in the welding consumable. Welding consumables with higher B contents resulted in longer total crack length and an increased number of cracks. Boron was intensely detected near the grain boundary of the weld centerline by secondary ion mass spectrometry (SIMS) analysis, and precipitated with boron carbide (Fe23(C,B)6), as analyzed by transmission electron microscopy (TEM). This promoted hot crack propagation in the high strength carbon steel welds. However, removing B from the welding consumable decreased the low temperature toughness for root and face weld metals, due to the growth of ferrite side plate (FSP), compared with welding consumables having more B or Mn contents. The addition of Mn in the weld metal suppressed the formation of FSP and increased low temperature toughness. Therefore, the minimization of B and the supplement of Mn successfully achieved hot crack resistance and low temperature toughness for high strength carbon steel welds of 550 MPa tensile strength. Key words: hot crack resistance, low temperature toughness, self-restraint testing, FCA welds, boron, manganese