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Flux-cored arc welding (FCAW) is a universal group of welding methods in terms of the scope of application and automation possibilities, the share of which in various industries in many countries is still increasing. The paper presents the results of bibliographic analyses (scientometric analysis with the use of VOSviewer, Bibliometrix and CitNetExplorer tools) of a data set of 993 publications indexed in the Web of Science database on the subject of FCAW for all types of flux-cored wires. An objective and unbiased approach to analysis resulted in a relatively neutral assessment of the state of knowledge in the field of FCAW and allowed for the identification of research directions carried out in the world, the dynamics of their changes as well as research gaps and needs. The scientometric analysis approach provided a holistic picture of the development of FCAW over the last 58 years, pointing to the geographical areas where this process has been and is most intensively researched, the agencies funding this research, the most active research teams, as well as the journals that have most often published articles on this topic. The most current research directions in relation to FCAW include underwater welding, hardfacing and cladding purposes, health and safety issues, and more general topic: properties and weldability of ferrous alloys. However, among the most urgent research needs the following topics: fatigue analysis of welded joints, environmental degradation of flux-cored wires, properties and weldability of nickel alloys, development of hybrid and combined welding procedures can be listed.

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 ( X 1 ), wire feed rate ( X 2 ), welding speed ( X 3 ), and nozzle-to-plate distance ( X 4 ). 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).

The microstructural and mechanical evaluation of 9% Ni steel with flux-cored arc welding (FCAW) was performed with two different Ni-based weld metals: Inconel 625 and Hastelloy 609. The weld metals showed microstructural changes depending on the temperature gradient and crystal growth rate for each region during the cooling after welding. A cellular/planar growth was exhibited at the bottom of the weld metal, which was rapidly cooled in contact with the cold base metal. Columnar dendrites were exhibited in the central region that cooled relatively slowly, and precipitates were observed in the interdendritic region. The weld joints between the base metal and weld metal have a compositional transition region due to dilution. The transition region comprised a martensite layer and a γ-phase cellular/planar layer, according to the compositional distribution. In the low-temperature toughness test, the absorbed impact energies were 89 and 55 J for Inconel 625 and Hastelloy 609, respectively. When Inconel 625 is used as the weld metal compared to Hastelloy 609, the high content of the γ-stabilizer and martensite start temperature decreasing elements leads to the formation of a thicker γ-phase layer and thinner martensite layer in the transition region. In addition, the high content of these elements suppresses the martensite transformation and maintains the stability of the weld joint interface even at low temperatures, resulting in the higher absorbed impact energy. The microstructure of weld joints and its influences on mechanical properties help to improve the practical application of 9% Ni steel FCAW.

Flux-cored arc welding (FCAW) joints with 9% Ni steel were prepared using Ni-based superalloy filler metals. The correlation between the microstructure and mechanical properties of the weld joint based on the type of filler materials was investigated. Owing to the heat transferred during the welding process, the heat-affected zone (HAZ) of the base metal primarily comprised martensite and exhibited higher hardness than the weld metal and existing base metal. To evaluate the toughness of FCAW joints against low-temperature fractures, Charpy impact tests at −196 °C were conducted; an absorbed impact energy of at least 55 J was observed in the weld metal, HAZ, and base metal regions, which was significantly higher than the standard specification. Comparing Alloys 709 and 609 as filler metals, a higher absorbed impact energy was observed when using Alloy 709 in both the weld metal and HAZ regions. This is because the quantity of precipitates, which can act as a point of crack initiation and propagation in weld beads, was smaller when Alloy 709 was used, and the γ phase was stably maintained even at low temperatures owing to the high content of elements that decrease the martensite start temperature (γ stabilizers) in the bead and transition areas. Furthermore, Alloy 709 obtained a low volume fraction and small grain size in the coarse-grained HAZ, which is known as the toughness degradation zone. This can contribute to the higher impact toughness compared with Alloy 609.

A series of CaF 2 -Al 2 O 3 -TiO 2 welding fluxes with TiO 2 content from 20 to 60 wt.% were applied to join EH36 shipbuilding steel under high heat input submerged arc welding. The effect of TiO 2 content on Charpy impact energy, inclusion characteristics, microstructure features, and chemical compositions of weld metals were systematically investigated. A maximum Charpy impact energy of 81.67 J was detected for the weld metal treated by the flux with 50 wt.% TiO 2 . Such unusual behavior was consistent with the initially increased and subsequently decreased changing trend for the faction of acicular ferrite, which is closely related to the formation, number density, and size distribution of significantly populated TiO 2 -containing inclusions that were largely dictated by the transfer of O and Ti. Current findings may serve as a viable way of tuning weld metal properties enabled by optimized flux designs.

The International Maritime Organization (IMO) is currently rolling out more restrictive regulations in order to achieve net-zero GHG emissions by 2050. In response, the shipping industry is planning to pivot to green energy sources such as hydrogen fuel. However, since hydrogen has an extremely low boiling point (−253 °C), materials for storing liquid hydrogen must be highly resistant to low-temperature brittleness and hydrogen embrittlement. A 316L stainless steel is a typical material that meets these requirements, and various welds have been studied. In this study, 3 pass butt welding was performed by applying the FCAW (flux cored arc welding) process to 10 mm thick ASTM-A240M-316L stainless steel, with the size of the fusion zone and HAZ investigated by mechanical testing and heat transfer FE analysis according to process variables, such as heat input, welding speed, and the number of passes. In all cases, the yield and tensile strengths were about 10% and 3% higher than the base metal, respectively. Furthermore, heat transfer FE analysis showed an average error rate of 1.3% for penetration and 10.5% for width and confirmed the size of the HAZ, which experienced temperatures between 500 °C and 800 °C.

In this study, AISI 316 types of austenitic stainless steels were welded by FCAW (flux-cored arc welding) using E316LT1-1/4 flux-cored wire under various shielding gas mixtures containing CO 2 at different ratios. Effects of mixed ratio of Ar and CO 2 in the in the shielding gas on the microstructure, impact toughness, and microhardness of welded materials were studied. Stereo optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscope (TEM), and TEM/mapping analysis techniques were used for microstructural characterizations. The impact toughness values of the weldments were decreased as a result of the formation and growth of inclusions in the microstructure due to the increases amount of CO 2 in the shielding gas. The hardness values and δ-ferrite amount in the weld metal were affected by depending on of the shielding gas mixtures.

This work investigated microstructure and impact toughness of multi-pass flux-cored arc welded SM570-TMC steel. A comparison was made between weldments fabricated with average heat input of 0.9 kJ/mm and 1.4 kJ/mm, respectively. SM570 steel plate with 16 mm nominal thickness and 1.2 mm diameter of E81-Ni1 flux-cored wire were selected in this experiment. Multi-pass flux-cored arc welding (FCAW) was performed using carbon dioxide shielding gas. Then the weldments were observed using optical microscopy, scanning electron microscope (SEM) and electron probe micro analyzer (EPMA). The steel joint strength was measured via tensile test, and Charpy impact test was performed at three different test temperatures. The microstructure observation exhibited the base metal mainly consist of ferrite and pearlite features, while the weld metal contained the acicular ferrites, polygonal ferrites and M-A constituent at both different heat inputs. The impact toughness of base metal is superior than weld metals. The weld metals fabricated at average heat input of 0.9 kJ/mm have a higher low temperature impact toughness than using heat input of 1.4 kJ/mm. The acicular ferrites amount that significant reduced at the higher heat input may degrade the toughness at low temperature.

An analysis of common reinforcement methods of machine parts and theoretical bases for the selection of their chemical composition were carried out. Prospects for using flux-cored arc welding (FCAW) to restore and increase the wear resistance of machine parts in industries such as metallurgy, agricultural, wood processing, and oil industry were presented. It is noted that conventional series electrodes made of tungsten carbide are expensive, which limits their widespread use in some industries. The scope of this work includes the development of the chemical composition of tungsten-free hardfacing alloys based on the Fe-Mo-B-C system and hardfacing technology and the investigation of the microstructure and the mechanical properties of the developed hardfacing alloys. The composition of the hardfacing alloys was developed by extending the Fe-Mo-B-C system with Ti and Mn. The determination of wear resistance under abrasion and impact-abrasion wear test conditions and the hardness measurement by means of indentation and SEM analysis of the microstructures was completed. The results obtained show that the use of pure metal powders as starting components for electrodes based on the Fe-Mo-B-C system leads to the formation of a wear-resistant phase Fe(Mo,B)2 during FCAW. The addition of Ti and Mn results in a significant increase in abrasion and impact-abrasion wear resistance by 1.2 and 1.3 times, respectively.

The underwater welding process used to repair offshore engineering structures involves a large number of processing parameters that must be selected and strictly controlled to achieve the required metallurgical and mechanical characteristics. Internal and surface porosity is a very common serious problem in underwater welding directly dependent on the process parameters. In this research work, a novel modeling and optimization study applying support vector regression (SVR) model and sequential quadratic programming (SQP) algorithm in order to predict and optimize the main process parameters of underwater flux cored arc welding (FCAW) on surface porosity in bead-on-plate welds of ASTM A36 steel is investigated. For this purpose, the experimental underwater wet FCAW process was carried out in an open tank with a 30-cm fresh water column. A composed central design was used to obtain the experimental matrix of 17 underwater welding tests with several combinations of parameters and variation levels: voltage ( V , 22–26 V), welding speed ( v , 3–10 mm/s), and wire feed speed ( WFS , 6350–11,430 mm/min) and the surface porosity was counted to each weld bead. In general, the results showed that this new computational approach using SVR satisfactorily approximates the level of surface porosity according to the operational variables. The model was validated with experimental results obtained from optimization with sequential quadratic programming algorithm. Using both mathematical methods, it was possible to obtain adequate parameters ( V = 24V, WFS = 8890 mm/min, and v = 3.4 mm/s) to experimentally produce underwater welds with minimal surface porosity (fewer than 10 pores in a bead length of 30 cm).