Flux-cored Wire Research Articles

Microstructural evolution and high-temperature oxidation behavior of oxide dispersion strengthened Inconel 625 superalloy fabricated by directed energy deposition

In the present study, wire arc-directed energy deposition (DED) technology was developed to fabricate the Oxide dispersion strengthened (ODS) Ni-based superalloy employing an Inconel 625 flux-cored wire including nano-La2O3 oxides. The microstructural evolution, mechanical properties and high-temperature oxidation behavior were systematically investigated. The results indicate that the melting and decomposition of La2O3 are thought to take place within the melt pool, followed by rapidly combining with Ti to re-precipitate as La2Ti2O7 oxides during DED. These oxides can serve as a highly effective nucleation site according to edge-to-edge matching calculation, resulting in the columnar-to-equiaxed transition and the refinement of grains. However, it is found that plenty of La elements are absorbed by the molten flux in the filler wire, resulting in the formation of slag and the loss of La. Consequently, the strength increases slightly due to the combined effects of precipitation strengthening and grain boundary strengthening. Furthermore, The ODS Inconel 625 sample can achieve a higher oxidation resistance after high-temperature oxidation at 900 °C for 150 h. The fine microstructure promotes the rapid formation of dense Cr2O3 oxide scales. On the other hand, the precipitation of La-rich oxides retards the outward transport of cation such as Ni, Fe and Nb, leading to the formation of a protective δ-Ni3Nb layer beneath the Cr2O3 layer to prevent the oxidation of matrix.

Alloying systems for modern flux-cored wires for mechanized welding in shielding gases of high-strength shipbuilding steels

An analysis of the domestic market for flux-cored wire used for welding low-alloy high-strength shipbuilding steels has been carried out. It has been established that to ensure a guaranteed value of the yield strength of the weld metal from 420 to 620 MPa, alloying systems such as Mn–Si, Mn–Si–Ni and Mn–Si–Ni–Mo are taken as a basis. The influence of alloying elements used in these systems on the formation of the microstructure and properties of welds was experimentally established.

Grain refinement of flux-cored wire arc additively manufactured duplex stainless steel through in-situ alloying of Ti

One of the major problems in the wire arc additive manufacturing (WAAM) of duplex stainless steel (DSS) is the epitaxial growth of coarsen columnar ferrite grains crossing the deposition layers, which leads to the mechanical property anisotropy and increases the risk of hot tearing. In this investigation, Ti was in-situ alloyed to the WAAM DSS to promote grain refinement of ferrite. The results revealed that the ferrite transformed from columnar to equiaxed morphology with the increase of Ti content. In the sample with 0.5%Ti addition, some fine equiaxed ferrite grains with an average grain size of 39 μm formed at the fusion line, which inhibited the epitaxial growth of columnar grains. With further increase of Ti addition to 1.0%, the ferrite grains in the as-deposited WAAM DSS completely transformed from columnar to equiaxed structure, with an average grain size of 12 μm at the fusion line and 19 μm at the interior of deposition layer. Ti2N-Al2O3 particles with an average diameter of 400 nm were found in the equiaxed grains at room temperature, which existed in the form of TiN-Al2O3 in the molten pool and promoted the heterogeneous nucleation of ferrite. The analyzation based on Interdependence Theory demonstrated that Ti refined the ferrite in WAAM DSS by promoting the formation rate of the constitutional supercooling zone ahead of the solid/liquid interface and by introducing effective nucleat particles into it.

Microstructure homogenisation by adapting the melting behaviour of flux-cored wires in GMAW

The composition of filling-alloyed flux-cored wires is achieved by adjusting the filling components without changing the wire material. A disadvantage of this type is, that due to the high alloy concentrations in the filling, microscale segregation can occur in the melt pool. The ‘theory-of-two-melts’ is cited in the literature as the reason for this. This theory states that, due to the typical separate melting behaviour of filling-alloyed flux-cored wire, there are droplets of different compositions (melt A and melt B) which do not homogenise in the melt pool and cause these microscale segregations. To test this theory, the melting behaviour of filling-alloyed flux-cored wires and the homogeneity of the individual droplets were investigated in this work by using the indicator material P92 (9% chromium steel). For this purpose, the liquid melting droplets were separated and then analysed metallographically via optical microscope and chemically using energy dispersive X-ray spectroscopy. Based on this, the melting behaviour was then optimised by adjusting the wire temperature. For this purpose, two different methods (conductive heating before and after current contact nozzle – CCN) for wire preheating were analysed. On the one hand, the results show no deviations in the chemical composition between the individual drops. On the other hand, chromium-rich micro segregations could already be detected directly in the droplets. The ‘two-melt’ theory as the cause of the microscale inhomogeneities can therefore not be confirmed. However, it was shown that an increase in the wire temperature, regardless of the preheating system, leads to a reduction of the chromium-rich inhomogeneities in the droplets by up to 95%. This effect was strongest in the presence of a melting behaviour similar to solid wire, which could be realised by increasing the contact tip working distance to 70 mm.

Structure and properties of high-speed R2M9YuAT alloy formed by plasma surfacing in nitrogen with flux-cored wire

The structure and properties of the high-speed R2M9YuAT alloy formed by plasma surfacing in nitrogen are studied. The samples are surfaced by a plasma arc at reverse polarity with the supply of non-current-carrying filler flux-cored PP-R2M9YuAT wire, additionally containing nitrided ferrochrome and titanium, into the weld pool. Surfacing of the samples is carried out using a plasma surfacing installation using UD-417D flux-cored wires. After surfacing is completed, the workpiece is cooled in air and subjected to high-temperature tempering at a temperature 560...580 °C, holding time 1 hour, number of temperings 4. The microhardness distribution of the surface layer of the deposited R2M9YuAT alloy in the state after plasma surfacing and after surfacing and high-temperature tempering is studied. Microhardness values vary from a minimum value of 4.68 to 5.93 GPa, and the distribution of microhardness of the deposited layer in the state after plasma surfacing is characterized by significant unevenness, which is explained by the comрlex thermal effect of multilayer plasma surfacing. Quadruple hightemperature tempering leads to the transformation of retained austenite and the precipitation of carbides and carbonitrides. The microhardness of the deposited metal after tempering increases from 6.89 to 7.48 GPa, and its distribution has become more uniform. It is established that the main phases in the deposited metal after high-temperature tempering are a solid solution of α-iron, carbides and carbonitrides based on iron, tungsten, molybdenum, chromium, aluminum and titanium.

Influence of NIR-laser radiation on the underwater arc welding process with flux-cored wire

The combination of laser radiation and electric arc as hybrid welding is used successfully in industry. In the underwater area, this technology is currently being researched but is not yet part of the industry. This paper demonstrates laser-stabilized arc welding with flux-cored electrode for underwater applications where the laser power density of the laser radiation does not result in a deep penetration welding effect. Steel samples (S235-JR) with a thickness of 10 mm were examined as bead-on-plate welds with a laser power density of 0.7-2.8 x 104 W/cm² at a wavelength of 1030 nm. The addition of laser radiation at low laser power density stabilizes the arc and produces a homogeneous weld seam. The process behavior and stability are characterized by measuring the current and voltage signals and analyzed regarding the laser beam and current source parameters. The metallographic analyses are used to compare the weld seam geometry and the microstructure properties.

Study of structure and tribological properties of modified wear-resistant coatings made of flux-cored wires

The article presents the results of researches of the structure and tribological properties of electroarc metallization coatings made of flux-cored wires with modifying additives of aluminium oxide Al2O3 and niobium Nb. For this purpose, metallographic and micro-X-ray spectral analyzes of the coating structures were carried out. The friction coefficients of coatings have been researched and their dependence on the steady roughness of the friction surface has been constructed.

Modeling of the chemical composition of the layer fused with a powder electrode

Problem. The work is devoted to the problem of the formation of high-quality deposited metal during the restoration of parts of small diameters with insignificant dimensions of wear. Goal. The purpose of the work is the development of a mathematical model for calculating the composition of metal deposited by flux-cored wire with forced transfer of the electrode metal. Methodology. The composition of the core of the powder electrode should ensure protection of the deposited metal from the action of air, ensure alloying of the metal, its deoxidation, high-quality formation of the bead, easy separation of the slag crust, minimal splashing of the molten metal, the absence of pores, cracks, and slag inclusions in the deposited layer. However, a number of surfacing self-protecting powder electrodes contain a significant amount of gas-slag-forming components in the charge. The result can be: failure of the rollers to fuse with each other and with the base metal, loss of alloying elements due to oxidation, slagging of the rollers, and slag runoff. In order to ensure the specified chemical composition of the deposited metal, a mathematical model for calculating the composition of a layer deposited by a powder electrode with forced metal transfer has been developed, which id correctly taken into account during the configuration of the rollers relative to each other and relative to the base metal. Results. The influence of the deposition step and the coefficient of reinforcement of the deposited roll on the value of the share of the metal of the previous roll of the deposited layer in the next roll was determined. The influence of the surfacing step on the quality of the formation of the surfacing layer was determined experimentally. Practical value. Technological recommendations have been developed and proposed for applying a layer with powder electrodes with forced metal transfer, which ensure high quality of the deposited metal with the formation of a layer of the required chemical composition. It was established that if the recommendations regarding the technological parameters of the process are followed, the necessary chemical composition of the deposited metal is achieved already in the second layer.

Fusion of dies with economy-layed secondaryhard-ducted steel

Problem. The purpose of the work is to increase the wear resistance and heat resistance of secondary hardening surfacing steels by improving the composition of alloying powder wires due to the optimization of the content of titanium, molybdenum and chromium. It was found that increasing the heat resistance of iron-based Cr-Mn-Ti alloys contributes to an increase in the content of the carbide phase [TiC]; the introduction of [Mo] stabilizes the value of hardness at elevated temperatures, increases heat resistance and hardness during dispersion hardening. High indicators of heat resistance and wear resistance of steel 18X4G10M5T3S are achieved due to additional diffusion formation of the carbide phase during aging, increased contact strength, a significant amount and uniform distribution in the volume of the deposited metal of the carbide phase. Goal. Іncreasing the wear resistance and heat resistance of secondary hardening surfacing steels by improving the composition of alloying powder wires due to the optimization of the content of titanium, molybdenum and chromium. Methodology. For automatic arc surfacing under the flux, attachment devices were designed and manufactured for feeding the de-energized flux-cored wire into the welding bath. The use of these devices on the A-1401 and TS-17M welding machines made it possible to study the influence of the de-sintering additive on the deposition parameters, chemical and phase composition of the deposited metal. The surfacing was carried out on samples made of steel 20 and 50 KhNM according to the "slide" scheme. The powder wire was produced at the laboratory facility of the Department of Welding Production of UIPA. The crack resistance of the alloys was studied at the LTP 1-6 installation. Results. On the basis of experimental studies, it was established that automatic surfacing with a de-energized additive increases the technical and economic indicators of melting - the surfacing coefficient is up to 30 g/Ag, the share of the base metal in the surfacing decreases to 11...14%, reduces the specific fuel costs and energy costs - increases the specific energy for the formation of a seam above the conventional limit of fusion and thermal efficiency. by 60...70% and 40...50%, reduces the coefficients of the relative mass of slag by 24...28%, increases the absorption coefficients of alloying elements by 70...80% in contrast to single-electrode melting. Originality It was found that increasing the heat resistance of iron-based Cr-Mn-Ti alloys contributes to an increase in the content of the carbide phase [TiC]; the introduction of [Mo] stabilizes the value of hardness at elevated temperatures, increases heat resistance and hardness during dispersion hardening. Practical value. On the basis of the conducted research, economically alloyed wear-resistant alloys and the technology of their application were developed to restore the grooves of the matrices of hot metal stamping dies. The use of these alloys and the technology of their application ensures a reduction in energy and resource costs and an increase in the durability of the stamping tool.

Exploring the trends in flux-cored arc welding: scientometric analysis approach

AbstractFlux-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.

Corrosion behavior of N-containing low Ni deposited metal and Inconel 625 deposited metal in 40 mol% MgCl2 + 60 mol% KCl molten salt at 600 °C

The service environment of solar energy storage tube is faced with molten salt corrosion. After failure, Inconel 625 flux-cored wire is commonly used for repair welding. However, Ni is expensive and lacks resources. In this paper, a low-cost N-containing low Ni flux-cored wire was designed. It was used to replace the current Inconel 625 flux-cored wire. The corrosion behavior of two deposited metals in 40 mol % MgCl2 + 60 mol % KCl molten salt at 600 °C for 72 h was tested. The results showed that the corrosion rates of N-containing low Ni deposited metal and Inconel 625 deposited metal were 6.04 μm/year and 8.19 μm/year, respectively. The proportion of HAGBs was 83.9 % and 93.4 %, respectively. The hot corrosion path penetrates along the random HAGBs. The proportion of HAGBs of the N-containing low Ni deposited metal was small, and N element first combined with Cr element to inhibit the precipitation of Cr23C6. The N-containing low Ni deposited metal reduced the diffusion path of Cr element and improved its corrosion resistance.

Technological methods of controlling the formation of metal deposited by flux-cored wires

Technological methods of controlling the formation of metal deposited by flux-cored wires

Investigation on the Metal Transfer and Cavity Evolution during Submerged Arc Welding with X-ray Imaging Technology

The physical phenomena of submerged arc welding (SAW) conducted with a 1.6 mm flux-cored wire were investigated using X-ray imaging technique. Three kinds of metal transfer modes were confirmed in this paper, namely the front flux wall-guided droplet transfer, back flux wall-guided droplet transfer, and repelled droplet transfer, of which the corresponding percentages were 47.65%, 45.29%, and 7.06%, respectively. Although the average sizes of the droplets for SAW and FCAW (flux-cored wire welding) were 2.0 mm and 1.9 mm with an average droplet transfer time of 90.3 ms, it required 36.4% more time for the droplet of SAW to finish one metal transfer than it did in FCAW. In addition, the volume of the cavity was not constant but repeated a cycle mode of “expansion and contraction” during the whole process. Thus, the dynamics of the cavity and viscous resistance caused by the flux collectively slowed down the velocity of the droplets from the wire to the weld pool in SAW. Compared with FCAW, a smoother weld without pits and pores was manufactured during the SAW process. Due to the compression effect of the flux, the 14.5 mm average weld width of SAW was 2.9 mm shorter than that of the FCAW. Furthermore, the thickness of slag with a porous structure in SAW was 2.7 times of that in FCAW, indicating that it could provide better protection to the weld of SAW.

Reduction of the welding fume emission rate of gas-shielded cored wires by the MAG pulse welding process variant

The aim of the study is to reduce welding fume emissions from flux-cored wires using pulse technology. Low-alloyed cored wires of the rutile, basic, and metal powder types were selected for this purpose. The analyses were carried out on a DIN EN ISO 15011–1:2010 compliant test rig. In addition, high-speed recordings of the material transition mode and metallographic cross-sections were made to interpret the results. Using characteristic curves developed in pre-tests, the influence of pulse time, pulse frequency, and trigger current on the welding fume emission potential of the rutile cored wire was first determined. Short pulses, medium trigger current, and medium pulse frequency were found to have a positive influence on the emission rate.Finally, the welding fume emissions of the conventional characteristic are compared with the emission-optimized pulse characteristic. For all three filling types, emission reductions of up to 41% were found when using the pulse technology. When considering the ratio of fume generated to the mass of the weld metal produced, with the associated greatly reduced economy of the process, it became apparent that pulse welding is not suitable for welding cored wires without restrictions.In summary, the suitability of pulse GMAW technology for reducing welding fume emissions can also be confirmed for flux-cored wires.

Зварювально-технологічні властивості порошкового дроту, шихта якого містить лігатуру з бором

Зварювально-технологічні властивості порошкового дроту, шихта якого містить лігатуру з бором

Welding-technological properties of flux-cored wire with boron-containing binder in the charge

Welding-technological properties of flux-cored wire with boron-containing binder in the charge

Study on Hot Corrosion of Low-Nickel Cladding Metals Containing Nitrogen in K2SO4-MgSO4 Binary Molten Salt

Molten salt is usually used as the energy storage medium for solar energy heat storage pipes, and 40wt% K2SO4 + 60wt% MgSO4 is very suitable for use as a heat storage material for solar thermal power generation in tower and butterfly parabolic systems. The demand for high-temperature thermal energy storage systems has prompted research on low-cost alloys for use in high-temperature and corrosion-resistant environments. The 44% Ni-24% Cr-0.18N nitrogen-containing low-nickel flux-cored welding wire designed in this article has a corrosion resistance of up to 900 °C after welding repair, which is better than the repair ability of Inconel 625 flux-cored welding wire. Using the high-temperature static immersion corrosion method, the corrosion behavior of two deposited metals immersed in molten salt for 60 h at 900 °C was assessed. The corrosion product phase composition, corrosion morphology, and elemental distribution of the two deposited metals were systematically studied using X-ray diffraction (XRD) and a Gemini SEM 300 (Zeiss thermal field scanning electron microscope). The results showed that the corrosion weight loss of the deposited metals showed the same trend at 900 °C, with corrosion occurring slowly from 0 h to 10 h and increasing after 10 h to 60 h. It was found that 10 h was the boundary point for corrosion behavior, and the corrosion resistance of the low-nickel nitrogen-containing deposited metal is better than that of the Inconel 625 deposited metal. This was because the addition of N energy elements allowed the formation of a stable composite nitride layer to suppress corrosion.

Research on the Microstructure and Properties of Al Alloy/Steel CMT Welding-Brazing Joints with Al–Si Flux-Cored Welding Wires

Al alloy/steel composite structures combine the advantage of a lightweight Al alloy and high-strength steel and are widely used in new energy vehicles, solar photovoltaic, and other fields. The main problems with the connection of an Al alloy and steel are poor weld formation and difficulty in controlling the thickness of the intermetallic compounds (IMCs) at the interface of the Al alloy and steel, which deteriorates the mechanical properties and corrosion resistance of the Al alloy/steel joints. Therefore, experiments on Al alloy/steel CMT (cold metal transfer, CMT) welding brazing were conducted by using AlSi5 and AlSi12 flux-cored welding wires as filler metals. The macro morphology, microstructure composition, tensile strength, and corrosion resistance of the Al alloy/steel joints were then analyzed. The mechanism of the Noclock flux on the wettability and spreadability of the Al–Si welding wire to a low-carbon steel surface was discussed and the formation behavior of the IMCs at the interface layer of the Al alloy/steel joints was clarified. The results showed that the NH4F and NH4AlF4 of the Noclock flux induced and accelerated the removal of oxide films on the surface of the Al alloy and Al–Si welding wire at a high temperature. It promoted the wettability and spreadability of the Al–Si welding wire, which resulted in the improvement of the Al alloy/steel joint formation. Under the CMT arc heat source, the Al–Si welding wire melted, and then a chemical metallurgical reaction occurred among the Al, Si, and Fe elements. The τ5-Al7.2Fe1.8Si phase formed preferentially near the Al alloy fusion zone while the θ-Fe (Al, Si)3 phase formed near the steel side. Actually, the interface reaction layer was composed of a double-layer compound including the τ5-Al7.2Fe1.8Si phase and θ-Fe (Al, Si)3 phase. Additionally, the IMC thickness of the Al alloy/steel joint with the AlSi12 flux-cored welding wire was 3.01 μm, which was less than that with the AlSi5 flux-cored welding wire, so its tensile strength was less but its corrosion resistance was superior. The main reason for the corrosion resistance of Al alloy/steel joints was the presence of a large amount of Al2O3, FeO, and Fe2O3 in the passive film.

Effect of Chromium Carbide on the Structure and Properties of Weld-Deposited Metal Introduced into the Charge Mixture of a Flux-Cored Wire

Effect of Chromium Carbide on the Structure and Properties of Weld-Deposited Metal Introduced into the Charge Mixture of a Flux-Cored Wire

Development of flux-cored wire of Fe – C – Si – Mn – Cr – W – V system with additives of carbon-fluorine-containing material and titanium

The paper considers research of quality of the electric arc coating obtained using flux-cored wire of the Fe – C – Si – Mn – Cr – W – V system with additives of carbon-fluorine-containing material and titanium. The formation of an electric arc coating was carried out using an automatic arc welding machine ASAW-1250 with a new chromium-containing flux-cored wire on plates made of St3 steel. To exclude mixing of the deposited metal with the substrate steel, multilayer surfacing was conducted. The surfacing mode was calculated and refined experimentally. The authors studied the composition and properties of the surface of the electric arc coating after surfacing. As a substitute for amorphous carbon they used a carbon-fluorine-containing material (dust of gas purification of aluminum production). Surfacing was carried out under a flux made from slag produced by silicomanganese with a high content of sulfur. A regression analysis of influence of the deposited layer’s chemical composition on its hardness and wear rate was carried out and mathematical models of the investigated performance characteristics of the electric arc coating were obtained. With an increase in the content of chromium, tungsten, carbon and silicon, hardness of the deposited metal and its resistance to abrasive wear increase. The results of the conducted research make it possible to develop measures ensuring the required level of performance characteristics of the electric arc coating and can be used to make a forecast of hardness of the deposited layer and its wear resistance when the chemical composition of the metal changes, to predict the operational resistance of rolling rolls deposited with wires of the PP-Np-35V9Kh3SF type. Mathematical models of hardness of the deposited layer and its wear resistance help to clarify the mechanism of hardening and formation of protective properties of the surface layers of rolling rolls by means of electric arc coatings deposited with flux-cored wires.