Flux-cored Welding Wires Research Articles

Effect of mechanical vibration on the microstructure and mechanical properties of CO2/MAG welded joint of Q345B steel

Vibration assisted welding (VAW) has emerged as a successful replacement for heat treatments of arc welds to refine grain, reduce residual stresses and distortions and thus to improve its mechanical properties. In this paper, mechanical VAW would be applied on the 8 mm thickness Q345B steel CO2/MAG filler welding, and the filler materials are solid core welding wire and flux-cored welding wire, respectively. The results show that: with the application of vibration, the proeutectoid ferrite in the weld area becomes finer, and the dendrites in the columnar crystals become significantly finer and more evenly distributed. The microhardness value of the weld zone in the welded joint with vibration is higher than that in the welded joint without vibration. The tensile strength of the welded joint increased from 502.5 MPa to 551.0 MPa at the motor speed of 2700 r/min when using solid core welding wire, increase nearly 10%. While, the tensile strength was deteriorated after the motor speed increased to 3600 r/min, which decreased to only 412 MPa, and the decreasement reached 25% comparing with the motor speed of 2700 r/min. During the VAW, the tensile strength and impact value of the welded joints fabricated by flux-cored welding wire are obviously better than that fabricated by solid core welding wire.

The Effect of Addition Amount of Chromium Iron on the Bonding Strength between Alloy Steel Surfacing Layer and Steel Base Metal

Fe-C-Cr-Nb alloy steel surfacing layers with different contents of C and Cr were prepared on 45 steel base metal by selfshielded flux-cored wires with distinct amounts of high carbon chromium iron addition and melt arc surfacing. The composition and microstructure changes of the surfacing layer were tested and analyzed. The surfacing test plate was processed into a pulling specimen, and the bonding strength between the surfacing layer and the 45 steel base metal was tested with a self-designed pulling test method. The fracture location of the pulling specimen and fracture characteristics were observed by a metallurgical microscope and a scanning electron microscope. The result shows that with the increase of the amount of high carbon chromium iron added to flux-cored welding wire, the content of C and Cr in the surfacing layer increases, and the NbC hard phase disperses. The microstructure of the steel matrix changes from mixed martensite + residual austenite to high carbon martensite + residual austenite, and then independent austenite appears. The hardness of the surfacing layer first increases and then decreases. The bonding strength between the surfacing alloy and the 45 steel base metal first decreases and then increases, and the fracture location is at the bottom of the surfacing layer or the fusion zone with mostly quasi-cleavage characteristics. When the additional amount of high carbon chromium iron reaches 13%, thee pulling specimen exhibits significant deformation with the highest bonding strength, and the fracture is close to the fusion line, where there are numerous tearing edges and shallow dimples.

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.

Storage of High-Strength Steel Flux-Cored Welding Wires in Urbanized Areas

The condition of the consumables is a key factor determining the waste reduction in the welding processes and the quality of the welded joint. The paper presents the results of tests of four types of flux-cored wires dedicated for welding high-strength steels, stored for 1 month and 6 months in Poland in two urbanized areas: in a large seaside city (Gdańsk) and in Warsaw, located in the center of the country. The wires were subjected to macroscopic and microscopic (stereoscopic, SEM) observations, EDS analysis, technological tests assessing elastic properties and targetability. The degree of degradation of the wires was also tested using resistance measurements. In order to assess the effect of storing wires on the weldability of steel, the diffusible hydrogen content in deposited metal was determined by high-temperature extraction. It was found that the storage caused changes in the surface condition of the wires, affected their elasticity and electrical properties, which affects the behavior of the wires during welding. A significant influence of storage conditions on the hydrogenation of deposited metal was found: in the case of three types of wires, the level of low hydrogen processes was exceeded and the maximum result was 15.18 ml/100 g of deposited metal. It was also found that copper-plated wire showed a significantly increased resistance to storage conditions compared to non-copper-plated wires.

SELECTION OF A WELDING ELECTRODE TO PREVENT CONTACT CORROSION OF A STEEL 1.0402 WELD JOINT

Welded structures operate, as a rule, under conditions of simultaneous exposure to aggressive media and workloads. Thus, when protecting the metal of welded joints from corrosion fatigue, a number of specific problems arise due to the heterogeneity of their structure, the presence of multilayer welds, physical and geometric stress concentrators, and the staged nature of the change in the fine structure of the metal during fatigue loading. The result is an accelerated destruction of the metal in the junction zones of various structural forms, which are unequally adapted to the action of fatigue stresses. This fully applies to such critical structures of the oil and gas industry as pipelines, tanks, gas holders, etc. The purpose of the research was to establish the features of corrosion of welded joints made by various brands of electrodes by analyzing the change in the value of the electrode potential of the metal, which reflects the level of free energy of the surface layers in dynamics. Laboratory samples of carbon steel 1.0402 were subjected to manual arc welding (OZL-6, LB-52, MP-3 electrodes) and semi-automatic welding (EMK 6D polished wire and E71T1 rutile flux-cored welding wire with rapidly crystallizing slag). Further, their microstructural analysis was carried out and the hardness of various sections of welded joints was determined. It has been established that samples welded by semi-automatic welding are less susceptible to corrosion damage, since the distribution of electrode potentials in the zones of the welded joint indicates their lower structural inhomogeneity. In this case, general uniform corrosion takes place. In addition, the use of EMK 6D and E71T1 welding wires ensures better mechanical properties of welded joints.

Comparative analysis on occupational hazards of three welding operations

Objective: To explore the occupational hazards caused by three kinds of welding operations, and to provide data support for individual protection. Methods: In October 2020, the welding fumes, metal elements and welding arc generated by three welding operations of argon gas shielded welding (JS80 welding wire) , manual welding (ZS60A welding rod) and carbon dioxide shielded welding (907A flux cored wire) were collected and measured in the welding laboratory. The samples were analyze and compare in the laboratory, and the differences of the occupational hazard factors of the three welding operations were judged. Results: The concentration of welding fume produced by carbon dioxide shielded welding, manual welding (ZS60A electrode) , and argon gas shielded welding (JS80 welding wires) were 6.80 mg/m(3), 6.17 mg/m(3), and 3.13 mg/m(3), respectively. The effective irradiance of the welding arc outside the welding mask from high to low is manual welding (ZS60A electrode) , carbon dioxide shielded welding (907A flux-cored welding wire) , and argon shielded welding (JS80 welding wire) , respectively 1 010.7, 740.9, 589.5 μW/cm(2). The long-wave ultraviolet UVA intensity generated by argon shielded welding (JS80 welding wire) is the largest, which is 1 500 μW/cm(2). The content of Mn in the three welding operations is the highest, and JS80 welding wire has the highest Mn content of 128493.2 mg/kg. 907A flux cored wire has the highest Ti content, which is 24355.5mg/kg. The electrode ZS60A has the highest Cu content, which is 24422.12 mg/kg. Conclusion: The intensity of occupational hazards is different in the three kinds of welding operations, so the methods of personal protective equipment, field exposure assessment and health monitoring should be more targeted.

Više komponentne gasne mešavine za elektro-lučno zavarivanje konstrukcijskih i specialnih čelika i njihov uticaj na količinu i hemijski sastav dimnih gasova

MIG / MAG welding with solid or flux cored welding wire and TIG welding are most important arc processes for industrial application. In last period, laser welding become more and more important in industrial welding and cladding applications. Optimum selection of welding process for specific application include more important parameters like productivity, demand quality of weld and influence of welding process to health of welder. With shielding gases is possible to influence on productivity, and quantity of welding fumes. Some welding shielding gases include nitrogen.

Influence of welding gases and filler metals on hybrid laser-GMAW and Laser-FCAW welds

Hybrid Laser-Arc Welding (HLAW) is a relatively new joining technique that combines advantages from both laser beam welding and arc welding. The interaction between laser beam and arc welding provides advantageous synergic effects, especially for thick joints. On the other hand, this interaction brings extra complexity to HLAW, limiting its acceptance in industry. Therefore, it is still necessary to elucidate some features of HLAW, such as the influence of parameters and consumables on the characteristics of the resulting joints. In the present study, the effects of welding gases (Ar + CO2 in different proportions) and filler metals (solid and flux-cored wires) on thick S355 structural steel joints are assessed. The best welds in terms of geometric characteristics, microstructures, and mechanical behavior were fabricated with high CO2 content welding gases and flux-cored welding wires. The use of flux-cored wires promoted higher penetration, lower hardness, and formation of acicular ferrite, avoiding the formation of martensite encountered in joints welded with solid wires. Moreover, the application of flux-cored wires could lead to cost savings in future applications, by reducing the laser power required to produce sound joints.

Reduction of Copper to Steel Weld Ductility for Parts in Metallurgical Equipment

Despite being challenging, the welding of the dissimilar metals copper and steel is an essential process that is required for improving quality of equipment manufacturing in the fields of metallurgy, machine construction, and chemical industry. Restricted solubility of iron in copper leads to the formation of a supersaturated solid solution of iron and other chemical elements in the weld pool. Investigations have found the possibility of enhancing the process of welding copper with steel. In the case of using a flux-cored welding wire and an improved welding technique, the number of dendritic inclusions is reduced, and the weld ductility is improved. Studying the microstructure of a copper to steel weld confirmed the ability to enhance the outcome of the welding process of the dissimilar metals. The implementation of recommended preparation techniques of parts before welding, and optimization of the welding technique will increase the strength of the welds and, increases the operational reliability of metallurgical equipment.

TESTING THE STRUCTURE AND PROPERTIES OF STEELS AFTER HARDFACING AND LASER TREATMENT

This paper analyses the structure, hardness, and frictional wear resistance of surface layers formed on steels after hardfacing by means of the SSA arc method with self-shielded flux cored welding wire, with a content of carbon 5% and chromium 30% as well as boron alloying with the CO2 laser. S355J2 steel after being hardfaced with one up to three layers is characterized by the martensitic structure with chromium carbides and its surface hardness is 50–55HRC. In the weld deposit zone, with a thickness of up to approx. 2 mm, there is a constant distribution of hardness with the average value of 700 HV0.1, and then the hardness decreases to approx. 160 HV0.1 in the steel substrate. After hardfacing, the carbon content in S355J2 steel (0.23% wt.) increases to a similar content as in steel C90U in the initial state (0.96% wt.). After laser alloying with boron and after rapid cooling, C90U steel obtains distinctive paths with a zone structure and thickness reaching up to approx. 380 μm. In the remelted zone, there is a eutectic structure consisting of a mixture of iron borides and martensite with a hardness of approx. 1200–1800 HV0.1, and beneath it, there is heat affected zone with a martensitic-bainite structure with a hardness of approx. 700HV0.1. Hardfacing and laser heat treatment significantly decrease the frictional wear of the tested steels.

Evaluation of Residual Stresses in High-Pressure Valve Seat Surfacing

A high-pressure shut-off assembly fitting is a highly-loaded element. Application of flux-cored welding wire for strengthened the valve seat is considered. A valve heat treatment regime is recommended for ordering the microstructure and reducing stresses in the surfacing zone. Correlation of residual stresses with material microstructure is demonstrated.

Microstructure and Properties of X100 High Strength Pipeline Steel

In order to study the effect of welding process on the microstructure and properties of weld joint of X100 pipeline steel, GMAW was used to prepare the weld joint with low-carbon high manganese-molybdenum-nickel flux cored welding wire. SEM and XRD were used to analyze the microstructure and phase morphology of HAZ and weld metal. Hydraulic tensile testing machine and impact test machine were used to test the mechanical properties. The experimental results showed that the weld metal and HAZ were composed of bainite, ferrite and M/A, the microstructure was fine and uniform with columnar crystal morphology, and HAZ was quite coarse. Hardness of weld metal was 248HV, which is higher than that of base metal, however, HAZ was softening. The tensile strength of weld joint was 832Mpa, which is about 96% of the base metal. The impact absorbed energy at-20°C of the base metal and weld metal were 291J and 121J respectively, exhibiting excellent strength and toughness.

Effect of Alloy Addition Method on Thermal Fatigue of Cr5-Deposited Metal

Given the same alloy composition in Cr5 deposited surfacing metal, the influence of two different methods of adding Cr and C in the flux-cored welding wire (1#-chromium carbide powder; 2#-graphite and chromium powder) was studied on the thermal fatigue (TF) performance of the deposited metal. Results show that (1) for either as-welded or tempered state, after the same number of thermal cycles, the crack length of specimen 1# was greater than specimen 2#; (2) it took about 200 more cycles for the initiation of cracking and failure cracking on specimen 2# than on specimen 1#; and (3) after the same number of cycles, the length of failure cracks of the as-welded state was greater than the tempered state. Studies of the microscopic structure, number of inclusions, and grain size of both types of specimens show that only a portion of chromium carbide added in 1# flux-cored wire was oxidized in high-temperature molten droplets or weld pool, plenty of incompletely decomposed chromium carbide grains and those generated in site lead to higher amount of inclusions in the deposited metal, compared with 2#. In addition, the boundary between inclusions and matrix was distinct, and the contents of S and P were higher in 1#; a larger proportion of residual austenite and twin structures, slower transformation of the residual austenite during tempering, and coarser primitive austenite and matrix grains were found in 1#. These findings suggest that optimization of the method of adding alloy elements might be an effective and cost-efficient way of improving the TF performance of deposited metal.

Improving the technological conditions of drawing flux-cored welding wires

The proposed automated program takes into account changes in the geometrical parameters during drawing, the mechanical properties and the contact friction conditions along the length of the deformation zone, and also the conditions of plastic deformation of the shell and the fracture parameters of the shell. It is shown to be possible to produce defect-free flux-cored wires at the minimum number of passes.

Microstructural and mechanical properties of dual-phase steels welded using GMAW with solid and flux-cored welding wires

Abstract The aim of this study is to demonstrate the transformation of grade-A steel into dual-phase steel by heat treatment, and the joint performance of dual-phase steels welded by means of the gas metal arc welding process using both solid and flux-cored welding wires. Dual-phase steels with different contents of martensite were obtained by intercritical annealing in different temperature ranges of a grade-A shipbuilding steel, followed by water quenching. The experimental results revealed that the tensile strength of the dual-phase steels joined by solid wire is higher than that of the flux-cored wire joints. The microstructure of grade-A steel consists of ferrite and pearlite, while the dual-phase steels consist of ferrite and martensite. On the other hand, while the martensitic phase is especially encountered in the weld metal of the dual-phase steels joined with the solid wire, the ferrite phase is more common in the weld metal of the flux-cored wire joints.

Numerical Simulation and Test Study on Non-Preheating Welding Technology of HSLA Q550 Applied to Hydraulic Structures

In this paper, weld stress field of Non-preheating with t-joint weld process of high strength low alloy steel Q550 is simulated applying the coupling analysis of temperature and stress field in finite element method(FEM) software ANSYS. The research proves that weld joins can achieve equal strength with the base metal using low alloy high strength steel flux-cored welding wire PK-YJ707A of low hydrogen slag type system. Impact absorbing energy comes up with 107J at -20°C and comes up with 80J at -40°C. After the results of bending, the weld joins have no crack or smaller than 3mm. The mechanical property meets the requirements of the HSLA Q550. In addition, the simulation result is able to more accurately predict the welding stress field that can provide theoretical basis for guiding production practices, reducing cost and improving working environment.

Impact Abrasive Wear Resistance of High-Chromium Cast Iron Bars Reinforced Hadfield Steel Matrix Composite

Hadfield steel matrix composite, reinforced by high-chromium (Cr) cast iron bars, was fabricated by inserting high-Cr alloy flux-cored welding wires into Hadfield steel molten at 1500 °C. The characteristics for water-quenched composite were investigated and compared with those of reference Hadfield steel. The results show that flux-cored welding wires could be melted by heat capacity of Hadfield steel molten and transformed into high-Cr cast iron bar reinforcements after solidification. The reinforcements of water-quenched composite consist of martensite, eutectic M7C3 carbides and residual austenite. With the increasing of impact energy, the impact wear rate of the composite firstly decreases, and then increases slightly, therefore, the composite is more available to the conditions of low and medium impact energy. The reason is it can combine fully advantages of the outstanding toughness of Hadfield steel, and high hardness of high-Cr cast iron.

Reinforcement of Hadfield steel matrix by oriented high-chromium cast iron bars

To attain a wear-resistant material compatible with high hardness and high toughness, Hadfield steel matrix was reinforced by oriented high chromium cast iron bars, through inserting high chromium alloys flux-cored welding wires into Hadfield steel melt at 1500 ± 10 °C. The obtained composites were investigated by XRD, SEM, micro-hardness, three-body abrasion wear and impact toughness testers. The results show that the alloy powders inside the flux-cored welding wires can be melted by the heat capacity of Hadfield steel melt and in situ solidified into high chromium cast iron bar reinforcements tightly embedded in the matrix. The micro-hardness of reinforcements of the water-quenched composite is about four times higher than that of the matrix. The impact toughness of the water-quenched composite is higher than that of the as-cast composite and lower than that of Hadfield steel, and its fracture mechanism is very complicated and refers to brittle and ductile mixture fracture mode. The excellent impact toughness and better wear resistance of the water-quenched composite are attributed to combine fully the advantages and avoid the drawbacks of both Hadfield steel and high chromium cast iron. Additionally, in industrial application, the pulverizer plate produced by this composite, has also better wear resistance compared to the reference Hadfield steel pulverizer plate.

Microstructure and mechanical properties of high-Cr cast iron bars reinforced Hadfield steel matrix composites

To obtain the compatible material of high hardness and high toughness, Hadfield steel matrix composites, reinforced by high-Cr cast iron bars made of flux-cored welding wires, which were inserted into the Hadfield steel melt, were investigated. The mechanical properties of three materials, i e, composites for as-cast and quenching-water condition, as well as Hadfield steel, were compared. The results show that the alloy powder inside flux-cored welding wires can be melted by the heat capacity of Hadfield steel melt and solidify into high-Cr cast iron bars. The impact toughness of the composite for quenching-water condition is higher than that of the composite for as-cast condition and is lower than that of the Hadfield steel, but it can still meet the requirements of hardness and toughness in industrial application. Regardless of load variation, composite for quenching-water condition shows better wear resistance than those of the composite for as-cast condition and Hadfield steel. The modified fracture toughness and wear resistance of composites are attributed to not only the combining actions of Hadfield steel matrix and high-Cr cast iron bars, but also the effect of heat treatment.