Flux Cored Arc Welding Process Research Articles

FCAW repair welding cycles, HAZ microstructure and corrosion resistance of 2304 duplex stainless steel

Flux-cored arc welding (FCAW) is an automatic welding process widely employed to join duplex stainless steel (DSS) structures in industrial plants because of its high productivity. However, when multiple passes are performed, this process can lead to the formation of non-metallic inclusions originating from the slag in the fusion zone. In this case, the welded joint can be repaired using the same welding process. Some regions next to the heat-affected zone are not removed during the repairing operation. Thus, these regions are subjected to repeated welding cycles and to a high heat input, which can cause microstructural alteration that impairs the corrosion resistance of the welded material. The aim of this work was to study the corrosion resistance of 2304 DSS plates joined using the FCAW process and repaired using the same process. The influence of the repair procedure on the corrosion resistance of the welded joints was evaluated using potentiodynamic polarisation and chronoamperometric curves, which allow the determination of the critical pitting temperature of the samples. The microstructure obtained after each repair cycle was evaluated using optical microscopy and scanning electron microscopy. The results showed that the corrosion resistance was depressed as the number of repair cycles increased.

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.

Plasma Transferred Arc Welding of Stellite 6 Alloy on Stainless Steel for Wear Resistance

Austenitic stainless steel was deposited on 9Cr-1Mo steel (ASME Grade 91) by flux cored arc welding process and above that Stellite 6 (Co-Cr alloy) was coated by plasma transferred arc welding process to improve wear resistance for high temperature valves applications. Microstructural characterization was carried out on Stellite 6 coatings and hardness and chemical composition were measured by vicker's hardness tester and optical emission spectrometer respectively. The impact of alloying elements in Stellite 6 deposits and fusion line of Stellite 6 and stainless steel were analyzed by electron dispersive spectroscopy line scan. It was observed that dilution of Iron in PTA welding deposit in Stellite 6 is below 2% and hardness of more than 600 HV0.3 was obtained. Microstructure of Stellite 6 consisted of Co - solid solution matrix with dendritic structure and interdendritic eutectic carbides which provides the hardness. Pin-on-disc tests were carried out at 400°C and characterized using scanning electron microscope of worn out surfaces. The wear mechanism was identified as delamination and abrasive wear in the worn-out surfaces as observed. Abrasive form of wear was reported due to the presence of alloying elements such as Co, Cr & W.

Sensitivity Analysis for Process Parameters in Cladding of Austenitic Stainless Steel by Pulsed Metal Inert Gas Welding Process

In recent scenario, the automation in weld cladding process has a challenging task for most of the industries like automotive, petrochemical and food processing industries. Because to achieve the best quality of the weld clad bead geometry during automated process it is important to have complete control over the selected process parameters. The cladding process enhances the base material properties. Therefore, it is essential to predict the relationship between the process parameters and response the second order polynomial regression equation has to be developed. It makes more effectiveness of automated weld cladding processes. Palani and Murugan [1] developed a mathematical model for a flux cored arc welding process using an RSM method to study the direct effects and interaction effects of process parameters on clad bead geometry.

A Field Study on the Respiratory Deposition of the Nano-Sized Fraction of Mild and Stainless Steel Welding Fume Metals

A field study was conducted to estimate the amount of Cr, Mn, and Ni deposited in the respiratory system of 44 welders in two facilities. Each worker wore a nanoparticle respiratory deposition (NRD) sampler during gas metal arc welding (GMAW) of mild and stainless steel and flux-cored arc welding (FCAW) of mild steel. Several welders also wore side-by-side NRD samplers and closed-face filter cassettes for total particulate samples. The NRD sampler estimates the aerosol's nano-fraction deposited in the respiratory system. Mn concentrations for both welding processes ranged 2.8–199 μg/m3; Ni concentrations ranged 10–51 μg/m3; and Cr concentrations ranged 40–105 μg/m3. Cr(VI) concentrations ranged between 0.5–1.3 μg/m3. For the FCAW process the largest concentrations were reported for welders working in pairs. As a consequence this often resulted in workers being exposed to their own welding fumes and to those generated from the welding partner. Overall no correlation was found between air velocity and exposure (R2 = 0.002). The estimated percentage of the nano-fraction of Mn deposited in a mild-steel-welder's respiratory system ranged between 10 and 56%. For stainless steel welding, the NRD samplers collected 59% of the total Mn, 90% of the total Cr, and 64% of the total Ni. These results indicate that most of the Cr and more than half of the Ni and Mn in the fumes were in the fraction smaller than 300 nm.

Optimization of flux-cored arc welding process parameters by using genetic algorithm

The effect of flux-cored arc welding (FCAW) process parameters on the quality of the super duplex stainless steel (SDSS) claddings can be studied using Taguchi L9 design of experiments. In this experimental investigation, deposits were made with 30 % bead overlap. Establishing the optimum combination of process parameters is required to ensure better bead geometry and desired properties. The above objectives can be achieved by identifying the significant input process parameters as input to the mathematical models like welding voltage (X1), wire feed rate (X2), welding speed (X3), and nozzle-to-plate distance (X4). The identified responses governing the bead geometry are bead width (W) and height of the reinforcement (H). The mathematical models were constructed using the data collected from the experiments based on Taguchi L9 orthogonal array. Then, the responses were optimized using non-traditional nature-inspired technique like genetic algorithm (GA).

Effect of welding sequence of a multi-pass temper bead in gas-shielded flux-cored arc welding process: hardness, microstructure, and impact toughness analysis

Welding is used in ships, military, buildings, industrial machinery, automobiles, and many other industries. Problems associated with welding are common issues encountered in these fields. This paper investigated the weld profile, impact toughness, microhardness, and microstructure of a JIS SS400 structural multi-layer welding joint using gas-shielded flux-cored arc welding (FCAW-G). It further examined the effects of temper bead welding (TBW) made with two different welding processes, namely with 4 Layers 4 Passes (4L4P) and 4 Layers 10 Passes (4L10P). Thermocouples were fixed to measure the thermal cycles, and the temperature distribution curves along the weld seams were measured by infrared radiation (IR) images. All welded samples were checked using nondestructive phased array ultrasonic testing (PAUT) to ensure defect-free samples before the experiments commenced. The Charpy impact tests were finished at 20 and −20 °C, respectively. Vickers microhardness measurement was carried out at room temperature. The 4L4P welding process was found to improve the impact toughness of the welding joints. Ferrite (F) and acicular ferrite (AF) were observed via an optical microscope (OM) analysis of the 4L4P welding process, which was more effective in tempering the heat-affected zone (HAZ). In addition, it was found that the 4L4P welding process produced an overall lower hardness than the 4L10P welding process. The microstructure of the welding joints as well as the mechanical properties including impact toughness and microhardness were studied by using a scanning electron microscope (SEM) attached with an energy-dispersive spectrometer (EDS) and an OM.

Groove configurations of a flux-cored arc welding process used in critical structures of precision mechanical presses—mechanical and metallurgical studies

This paper utilized a flux-cored arc welding (FCAW) technique and investigated various groove configurations as well as multi-pass welding sequences to create welding specifications in the precision mechanical press industry. Experimental investigations were conducted to examine the influence of three different groove configurations of 40-mm-thick JIS SS400 structural steel welded joints on mechanical and metallurgical properties. Mechanical properties of the welded joints were evaluated by uniaxial tensile testing and Charpy V-notch (CVN) impact testing at room temperature. Simultaneously after a multi-pass welding sequence, various degrees of thermal treatments such as tempering or normalization inevitably occur in the heat-affected zone (HAZ). The unfavorable microstructures in the HAZ and reheated zones can be intentionally modified via the above procedure such that the toughness and microhardness of the HAZ improve. The experimental results revealed that of the three types of groove configurations (C1, C, and F), groove type C1 possessed the maximum yield strength (YS) and ultimate tensile strength (UTS) while groove type F possessed the highest CVN values tested at room temperature. The fundamental reason may be attributed to heat dissipation characteristics of each groove configuration and associated exertion of the multi-pass welding sequence. Microstructural and morphological features as revealed through an optical microscope also indicate a significant influential factor of these joints among the different groove configurations. Therefore, grain refinement of varying degrees can be obtained due to the variation of thermal characteristics of heat input/dissipation; thus, various mechanical and CVN impact properties can be obtained.

Intelligent Control Mechanism for Underwater Wet Welding

It is important to achieve high quality weld in underwater welding as it is vital to the integrity of the structures used in the offshore environment. Due to the difficulty in ensuring sound welds as it relates to the weld bead geometry, it is important to have a robust control mechanism that can meet this need. This work is aimed at designing a control mechanism for underwater wet welding which can control the welding process to ensure the desired weld bead geometry is achieved. Obtaining optimal bead width, penetration and reinforcement are essential parameters for the desired bead geometry. The method used in this study is the use of a control system that utilizes a combination of fuzzy and PID controller in controlling flux cored arc welding process. The outcome will ensure that optimal weld bead geometry is achieved as welding is being carried out at different water depth in the offshore environment. The result for the hybrid fuzzy-PID gives a satisfactory outcome of overshoot, rise time and steady error. This will lead to a robust welding system for oil and gas companies and other companies that carry out repair welding or construction welding in the offshore.

Analysis of flux cored arc welding process parameters by hybrid taguchi approach

This paper presents calculation of the welding process parameters for obtaining optimal weld bead geometry in Flux Cored arc welding (FCAW) process. Bead on plate welding was carried as per L16 orthogonal array. In this paper weld bead geometry such as penetration, bead width, reinforcement and percentage of dilution of IS 2062 structural steel plates investigated. Two hybrid techniques firstly Taguchi method coupled with Grey relational analysis and secondly Taguchi method in combination with desirability function (DF) approach has been applied in this paper. Comparison made between two hybrid optimization techniques are made to analyze to choose the best method. Optimal results have been confirmed by confirmatory experiment which showed satisfactory results.

A Processing Approach Incorporating Copper Backing-Wheel Device in Submerged Arc Welding for Manufacturing Cryogenic Storage Tanks

A processing approach using a copper backing-wheel device was developed to aid the fabrication process of industrial cryogenic storage tanks manufactured under the ASME Section VIII Division 1. This research focused on the welding processes related to the cylindrical-body assembly. Two processing steps involving the root-run formation and the replacement with a sound outer-circumference joint were studied. Initially, tank fabrication is achieved through the application of both flux-cored arc welding and submerged arc welding. A new processing approach was proposed with the modified method in cross-section preparation, and a low-cost reusable copper backing-wheel device was developed to facilitate the root-run formation using only submerged arc welding. Temperature gradient through the device components along the heat-conduction path was monitored to assure the conductivity of the backing device. The results suggest that the proposed approach reduced manufacturing time by removing the initial flux-cored arc welding process used in the conventional welding method. As an effect, the new approach show promise reduces the overall manufacturing cost of tank fabrication. Based on radiographic testing of tanks fabricated using the new approach found that circumference joints required little or no welding repair suggesting higher joint quality.

Effect of flux cored arc welding process parameters on bead geometry in super duplex stainless steel claddings

The welding heat input plays a significant role in determining the microstructure and composition of the super duplex stainless steel cladding. The welding process is represented in the form of mathematical models developed using response surface methodology. The models were then used to predict the weld bead characteristics with reasonable accuracy. In this work, the models were developed to relate the identified important process parameters like welding voltage, wire feed rate, welding speed, nozzle to plate distance and welding gun angle with bead geometry. The models found to satisfy the adequacy requirements. It was found that reinforcement form factor was influenced by the factors arc length, torch travel speed, melting rate and resistance heating of the electrode. In the same way penetration form factor is influenced by the arc length, torch travel speed and arc force at the weld puddle. Contact angle influenced by the melting rate and resistance heating of the electrode.

Residual stress measurement in an extra thick multi-pass weld using initial stress integrated inherent strain method

Residual stresses existing in a multi-pass butt joint with a thickness of 70 mm, using a flux-cored arc welding process, were measured by an inherent strain method (ISM). Since such a thick plate before welding contains a large amount of initial residual stresses (−300 to +100 MPa), the initial stresses were integrated with conventional ISM in order to determine the total residual stresses in a welded joint. Two methods named as initial stress integrated ISM and initial inherent strain integrated ISM were suggested for the consideration of the initial stress distributions through the thickness of base plates. The results show that there is a significant difference between the integrated ISM with initial stresses or initial inherent strain and the conventional ISM without initial stresses. The residual stresses measured by any of the initial stress integrated ISM and initial inherent strain integrated ISM agreed well with the neutron diffraction measurement. Thus, the proposed initial stress integrated ISM is a proper destructive measurement method in the case of thick weld joints.

시편 예열 온도가 FCW 용착금속의 확산성 수소량에 미치는 영향

Cold cracking of weldment is one of the most serious welding problems. A sufficient quantity of diffusible hydrogen, a residual stress, and a sensitive microstructure are the causes of cold cracking. Removal of any one of these factors can be used to prevent cold cracking. Application of flux cored arc welding process is increasing due to high productivity and easiness of welding. In addition, to prevent cold cracking in the HAZ or weldment, preheat temperature and interpass temperature have to be controlled. In this study, the effect of preheat temperature on the levels of diffusible hydrogen in the weld metal deposited using flux cored wire was examined. The levels of preheat temperature of base metal specimen were ambient temperature, 50, 100 and <TEX>$150^{\circ}C$</TEX> respectively. The result showed that the increase of preheat temperature was a linear relationship with reduction of diffusible hydrogen content in weldment.

A study on quality of weld in flux cored arc welding process

Flux cored arc welding (FCAW) is a semi–automatic or fully automatic welding method that is widely used for welding large and thick sections, especially in the flat position. The welding can be performed with shielding gas (FCAW–G) or without shielding gas (FCAW–S). A tubular filler wire containing mixture of mineral flux and powder in the core of the tube is supplied on reels and fed through the welding gun in metal inert gas (MIG) welding. The process is popularly used in construction and fabrication of carbon steel, low alloy steel weldment in power plant equipment. Hence in this paper effects of the welding parameters on the quality of weldment have been discussed based on the experimental data obtained. The welding was performed on metal plates of boiler quality of steel using a semiautomatic gas metal arc welding (GMAW) machine. To predict the weld quality, experiments were conducted based on three–factor five levels Taguchi orthogonal array design matrix. Parametric optimisation has been done based on radiographic test, visual inspection and tensile test results.

Optimization of Flux Cored Arc Welding Process Parameter Using Genetic and Memetic Algorithms

AbstractMost of the manufacturing enterprises indulge in the bonding of metals during the production process. This makes welding one of the most important processes in industries. Subsequently, due to the high usage of welding process, industrial engineers desire to optimize the parameters concerned to achieve the desired weld bead characteristics. This paper focuses on optimization of flux cored arc welding process parameters, which are used for deposition of duplex stainless steel on low carbon structural steel plates. Experiments were conducted based on central composite rotatable design and mathematical models were developed using multiple regression method. Further, optimization with objectives as minimizing percentage dilution, maximizing height of reinforcement and bead width was carried out using genetic algorithm and memetic algorithm. This problem was formulated as a multi objective, multivariable and non-linear programming problem. The algorithms were implemented using basic functions of C language making it highly reliable, adoptable, very user friendly and extendable to other welding processes such as GMAW, GTAW, robotic welding, etc. The adopted optimization techniques were further compared based on various computational factors.

Effect of Heat Input on Macro, Micro and Tensile Properties of Flux Cored Arc Welded Ferritic Stainless Steel Joints

This paper discusses the influence of Flux Cored Arc Welding Process parameters such as welding current, travel speed, voltage on bead profile, metallurgical and mechanical properties of welds of 2 mm thick 409M ferritic stainless steel sheets. The study reveals that, grain coarsening, volume fraction of martensite, hardness of heat affected zone and % of delta ferrite in ER 309 weld metal increases with increase in heat input. However, the results show that variation of heat input does not make any significant effect on tensile strength of the joint. Hence, welding parameters that provide uniform bead profile for the weld are recommended for fabrication.

Modeling and optimization of flux cored arc welding by genetic algorithm and simulated annealing algorithm

Purpose – The purpose of this study is to optimize the process parameters (wire feed rate (F), voltage (V), welding speed (S) and torch angle (A)) in order to obtain the optimum bead geometry (bead width (W), reinforcement (R) and depth of penetration (P)), considering the ranges of the process parameters using evolutionary algorithms, namely genetic algorithm (GA) and simulated annealing (SA) algorithm. Design/methodology/approach – The modeling of welding parameters in flux cored arc welding process using a set of experimental data and regression analysis, and optimization using GA and SA algorithm. Findings – The adequate mathematical model was developed. The multiple objectives were optimized satisfactorily by the GA and SA algorithms. The feasible solution results are very closer to the optimized results and the percentage error was found to be negligibly small. Originality/value – The optimal welding parameters were identified in order to increase the productivity. The welding input parameters effect was found.

Process Parameter Optimization of AISI 316L(N) Weld Joints Produced using Flux-Cored Arc Welding Process

Bead on plate welds were carried out on AISI 316L(N) austenitic stainless steel using flux cored arc welding process. The bead on plates weld was conducted as per L25 orthogonal array with statistical design of experiment technique. In this paper, the welding parameters will be optimized based on the weld bead geometry such as depth of penetration, bead width and weld reinforcement. Grey relational analysis and desirability approach are used to optimize the input parameters like wire feed rate, voltage, travel speed and torch angle while considering the multiple output variables simultaneously. Confirmation experiment has also been conducted to validate the optimized parameters.

Sensitivity Analysis of Flux Cored arc Welding Process Variables in Super Duplex Stainless Steel Claddings

Weld surfacing with super duplex grade stainless steel found to improve corrosion resistance and functional life of the mild steel components used in the process industries. The properties of the deposited layer were influenced by the process variables that affect the heat input to the process. The influence exerted by the process variables on the responses of super duplex stainless steel claddings were modeled using the response surface models. The response surface models developed by the regression techniques using the data collected from central composite rotatable design of experiments. The data extracted from 32 single bead on the plate welds were deposited by flux cored arc welding process. The developed models can be used to predict and simulate the influence of the process variables on the responses. The insignificant variables found in the full models were removed by the backward elimination technique. Sensitivity analysis performed on the reduced models helps to identify and rank the process variables based on their extent of influence on the responses. Then the ranked variables are closely regulated to tailor the properties of the surfaced layer.