Weld Metal Research Articles

In Situ Synchrotron X-ray Diffraction Analysis During Post-Weld Heat Treatments of Supermartensitic Stainless Steel Weld Metal

In Situ Synchrotron X-ray Diffraction Analysis During Post-Weld Heat Treatments of Supermartensitic Stainless Steel Weld Metal

Influence of arc energy on the microstructure and corrosion behavior of ER2209 duplex stainless steel deposited on Q345B low-alloy steel by GMAW

In order to eliminate the complex effects of thermal cycling and the thermal effects of the next pass on multi-layer multi-pass welding of low-alloy steel and duplex stainless steel, ER2209 welding wire was single-layer single-pass deposited on the surface of Q345B hot-rolled plate by gas metal arc welding (GMAW). The microstructure and corrosion resistance of welded joints were studied by different arc energies. The results showed that the arc energy had a significant impact on the “tongue-shaped” morphology and the width of heat affect zone in the welded joint, which in turn affected the corrosion performance of the welded joints. Due to the least distribution of “tongue-shaped” morphology and minimum width of heat affected zone in the welded joint with arc energy of 0.645kJ/mm, it owned the best corrosion resistance. The weld metals of the welded joints were composed of ferrite and austenite phases. The ferrite phases were distributed along grain boundaries and intergranular. As the heat input increases, the distribution of ferrite phase along grain boundaries gradually decreased. The corrosion products and corrosion morphology of the welded joint were also investigated and the corrosion mechanism was discussed in detail. The research results of this article provide a theoretical basis for improving the corrosion performance of multi-layer multi-pass welded joints of low-alloy and duplex stainless dissimilar steels.

Effect of heat input on microstructural evolution and impact toughness in dissimilar weld metals between medium Mn and V-microalloyed steel

High-quality weld metals are a prerequisite for ensuring the integrity of dissimilar steel welded joints. This research investigates the influence of heat input on the inclusion characteristics, variant selection, crystallographic texture, and resultant impact toughness of dissimilar weld metals used in joining heavy-plate medium Mn steel (MMS) and V-microalloyed steel (VMS). Results revealed that inclusion density decreased but its size increased as heat input increased from 10 to 15 and 20 kJ/cm, which alters in the nucleation mechanism of acicular ferrite (AF) from intragranular nucleation to sympathetic nucleation. The percentage of AF initially rose from 81.3 % to 83.2 %, and then declined to 79.1 %. Variant selection also transitioned from random to specific due to the variation in transition temperature and nucleation mechanism. Meanwhile, the fraction of unfavourable crystallographic texture increased from 1.5 % to 22.9 % and 26.1 %. Impact toughness was higher (128 J) at 10 kJ/cm compared to 15 kJ/cm (108 J) and 20 kJ/cm (110 J) owing to its smaller inclusion size and a lower percentage of unfavourable crystallographic texture. These findings offered theoretical guidance for selecting welding parameters in industrial applications for dissimilar welded joints of MMS and VMS.

Assessment of the fatigue crack growth behavior of HG785D steel welded joints

Fatigue performance of high-strength steel welded joints is widely concerned in engineering fields. In this research, the fatigue crack growth (FCG) behavior of HG785D steel with and without a "soft + hard + soft" composite welded metal is investigated by conducting FCG tests, hardness tests and fracture observation. Further, FCG curves (da/dN-ΔK) quantified by Seven-point incremental polynomial method (SP) and Smith method (SM) from tested crack length and number of cycles are compared. Results show the fatigue performance of composite welded metal is improved due to the hard layer ensures strength and soft layers provide toughness. Additionally, the fatigue life assessment is safer using da/dN-ΔK curves by SP, whereas more accurate using that by SM. The da/dN-ΔK curves by SP can capture the local fluctuations in FCG rate, while that by SM provides a smooth and global description for FCG behavior with steadily increased da/dN. Considering heterogeneous properties of composite welded metal, a piecewise function combining SP method is recommend to describe the unconventional da/dN-ΔK curves. Moreover, the correlation between Paris parameters for steels is analyzed, offering a reference for fatigue reliability assessments.

Hydrogen Embrittlement Sensitivity of X70 Welded Pipe Under a High-Pressure Pure Hydrogen Environment

With the rapid development of hydrogen pipelines, their safety issues have become increasingly prominent. In order to evaluate the properties of pipeline materials under a high-pressure hydrogen environment, this study investigates the hydrogen embrittlement sensitivity of X70 welded pipe in a 10 MPa high-pressure hydrogen environment, using slow strain rate testing (SSRT) and low-cycle fatigue (LCF) analysis. The microstructure, slow tensile and fatigue fracture morphology of base metal (BM) and weld metal (WM) were characterized and analyzed by means of ultra-depth microscope, scanning electron microscope (SEM), electron backscattering diffraction (EBSD), and transmission electron microscope (TEM). Results indicate that while the high-pressure hydrogen environment has minimal impact on ultimate tensile strength (UTS) for both BM and WM, it significantly decreases reduction of area (RA) and elongation (EL), with RA reduction in WM exceeding that in BM. Under the nitrogen environment, the slow tensile fracture of X70 pipeline steel BM and WM is a typical ductile fracture, while under the high-pressure hydrogen environment, the unevenness of the slow tensile fracture increased, and a large number of microcracks appeared on the fracture surface and edges, with the fracture mode changing to ductile fracture + quasi-cleavage fracture. In addition, the high-pressure hydrogen environment reduces the fatigue life of the BM and WM of X70 pipeline steel, and the fatigue life of the WM decreases more than that of the BM as well. Compared to the nitrogen environment, the fatigue fracture specimens of BM and WM in the hydrogen environment showed quasi-cleavage fracture patterns, and the fracture area in the instantaneous fracture zone (IFZ) was significantly reduced. Compared with the BM of X70 pipeline steel, although the effective grain size of the WM is smaller, WM’s microstructure, with larger Martensite/austenite (M/A) constituents and MnS and Al-rich oxides, contributes to a heightened embrittlement sensitivity. In contrast, the second-phase precipitation of nanosized Nb, V, and Ti composite carbon-nitride in the BM acts as an effective irreversible hydrogen trap, which can significantly reduce the hydrogen embrittlement sensitivity.

Ex-situ observation of ferrite grain growth behavior in a welded 9Cr-1Mo-V-Nb steel during aging at 740 °C

It has recently been reported that ferrite grains coarsened to several hundred micrometers were occasionally observed in long-term serviced 9Cr-1Mo-V-Nb steel welds. To clarify the factors that cause ferrite grain growth in martensite during high-temperature exposure, alternating aging heat treatment and observation of the same field of view was performed using a welded 9Cr-1Mo-V-Nb steel. Such ex-situ observations revealed that the rapid grain growth of ferrite by consuming martensite occurred in the weld metal during aging at 740 °C. In the test material used in this study, some δ-ferrite grains were observed in the weld metal near the fusion line. In the region where δ-ferrite grains were observed, the concentrations of austenite-forming elements such as Mn and Ni were locally decreased in the matrix due to dilution by the base metal, promoting δ-ferrite retention after welding. Ex-situ observation indicated that no significant grain growth of δ-ferrite occurred during aging. Therefore, it was suggested that a new ferrite grain formation followed by rapid grain growth consuming martensite occurred during aging. The elastic strain energy density of the dislocations PMdis and the interfacial energy density PMsurf in martensite can affect the driving force for ferrite grain growth by consuming martensite. Based on the evaluation results for PMdis and PMsurf after 500 h of aging, PMsurf was considered to be the main driving force for ferrite grain growth. Although the ferrite-formation process could not be directly observed, it is possible that ferrite was formed by the recrystallization of martensite through the bulging mechanism.

Effect of silane-doped argon shielding gases for gas metal arc welding of S355

Abstract The welding of steel grades relies primarily on the interaction of the weld metal with doped oxygen components of the shielding gas. This mainly serves to decrease the viscosity and reduce the surface tension of the melt in order to achieve an adjusted material transition. Interference with the ambient atmosphere is undesirable in this context. In order to prevent material-related changes in the microstructure, slag initiators are admixed which promote the precipitation of low-density oxides on the weld seam surface. Manufacturing technology is increasingly striving to eliminate the interaction of atmospheric oxygen in the production process. It is primarily intended to counteract the negative effects of oxygen during manufacturing. For this objective, silane-doped gases for subtractive manufacturing processes and additive manufacturing via the PBF-LB/M process have been considered. Small amounts of silane in conventional inert shielding gases allow partial pressures of oxygen that are comparable to a high vacuum. In the scope of this publication on investigations for welding applications, blind welds on S355 substrate plates were performed using G3Si1 filler material. In addition to the recommended M21, an argon shielding gas with 1.5% silane doping and argon 4.6 are applied for welding. Apart from the observation of the resulting energy input, the weld seams are metallographically characterized. For this purpose, the formation of silicates on the weld seam surface and the development of the weld seam within the base material are investigated. The volume of the weld seam is reduced as a result of the silane doping compared to the M21 application. The composition of the weld metal is significantly influenced by the silane content, leading to an increased manganese content in particular. The silane doping results in an intensified formation of an acicular bainitic structure and an accompanying hardening within the weld metal.

The Effect of Preheating on the Mechanical Properties of AISI 1037 and AISI 304 Welded Joints Using Shielded Metal Arc Welding

This study explores the effect of preheating on the toughness of dissimilar welded joints between AISI 1037 and AISI 304 steels, using Shielded Metal Arc Welding (SMAW) and E309-16 electrodes. The innovation of this approach lies in assessing how preheating temperatures influence the mechanical properties of such welds. Preheating temperatures ranged from 150 °C to 300 °C, with impact testing revealing a notable increase in toughness, from 6.01 Joules at 150 °C to 19.57 Joules at 300 °C. Hardness tests indicated a maximum hardness of 313 VHN in the fusion zone and a minimum of 185 VHN in the AISI 304 area. Compared to non-preheated joints, preheating significantly enhanced impact strength and altered the fracture mode from brittle to ductile. Macrostructural and microstructural analyses with optical microscopy and SEM showcased changes in fracture surfaces and microstructural evolution, highlighting the improvement in mechanical properties due to preheating. These findings demonstrate that preheating critically enhances the toughness and overall performance of dissimilar metal welds, making it a valuable technique in industrial applications where enhanced joint toughness is crucial.

Microstructure Evolution and Cryogenic Impact Toughness Changes in Ce‐Containing Novel Cryogenic High‐Mn Austenitic Steel Weld Metals under Different Heat Inputs

The Ce‐containing novel cryogenic high‐Mn austenitic steel weld metals under different heat inputs are prepared by submerged‐arc welding to provide a satisfactory welding parameter scheme and further optimize its cryogenic impact toughness. The effect of heat input on microstructure, inclusion, and cryogenic impact toughness of weld metals are investigated via optical, scanning electron microscopy, electron backscatter diffraction, electronic probe microanalyzer, and cryogenic impact test. The results show that the dendrite arm spacing, segregation ratio of Mn, Si, and C elements and average effective grain size of the weld metals gradually increase, and the proportion of high‐angle grain boundaries decrease with the heat input increase from 11.91 to 20.24 kJ cm−1. The type of inclusions of weld metal with different heat inputs are all Ce2O3 and Ce2O2S. The number density of inclusions decreases monotonically from 5976 to 4912 mm−2, while the average size increases from 0.32 to 0.45 μm with the heat input increased. The increase in heat inputs consistently decreases the mean cryogenic impact toughness of weld metals from 123 to 102 J. The higher proportion of high‐angle grain boundaries and finer inclusions at lower heat input play the critical role in improving the cryogenic impact toughness.

Nonuniformity of Fatigue Properties of Two‐Sided Electron Beam Welded Joint of Superthick Titanium Alloy

ABSTRACTThe TC4 titanium (Ti) alloy has been widely utilized in various industries such as aerospace and shipbuilding, owing to its numerous advantages. Its exceptional properties have made it a material of choice for applications requiring high performance and reliability. The total weld thickness was 140 mm, and microstructures and high‐cycle fatigue properties were investigated at three different layers within the 140‐mm section. Experimental results show that the overlap area at two weld roots has the highest microhardness and largest nonuniformity of the overall joints, so the area is found to have the poorest high‐cycle fatigue properties. The microstructures in every layer of the weld metal of the joints were analyzed to determine the causes of the poor fatigue properties in the overlapping area at the weld roots. Significant amounts of α′ acicular microstructure are present in the weld metal of joints, while the overlap area at weld roots contains more α′ acicular microstructure with a finer size. Compared with other layers, the weld metal and base metal in Layer 2 (overlap area) have the largest microhardness gradient, where the stress concentration is more serious in the fatigue experimental process. Heat dissipation conditions was a critical factor for the inhomogeneity of microstructure and mechanical properties along the thickness direction of 140‐mm double‐sided electron beam welding joint. Fatigue damage (micropore) is formed at β phases in priority, and fatigue cracks propagate via series connection of micropores, indicative of transgranular ductile cracks.

Numerical Simulation of Fatigue Crack Growth and Fracture in Welded Joints Using XFEM-A Review of Case Studies.

Numerical simulation of fatigue crack growth in welded joints is not well represented in the literature, especially from the point of view of material heterogeneity in a welded joint. Thus, several case studies are presented here, including some focusing on fracture, presented by two case studies of mismatched high-strength low-alloyed (HSLA) steel welded joints, with cracks in the heat affected zone (HAZ) or in weld metal (WM). For fatigue crack growth, the extended finite element method FEM (XFEM) was used, built in ABAQUS and ANSYS R19.2, as presented by four case studies, two of them without modelling different properties of the welded joint (WJ). In the first one, fatigue crack growth (FCG) in integral (welded) wing spar was simulated by XFEM to show that its path is partly along welded joints and provides a significantly longer fatigue life than riveted spars of the same geometry. In the second one, an integral skin-stringer panel, produced by means of laser beam welding (LBW), was analysed by XFEM in its usual form with stringers and additional welded clips. It was shown that the effect of the welded joint is not significant. In the remaining two papers, different zones in welded joints (base metal-BM, WM, and HAZ) were represented by different coefficients of the Paris law to simulate different resistances to FCG in the two cases; one welded joint was made of high-strength low-alloyed steel (P460NL1) and the other one of armour steel (Protac 500). Since neither ABAQUS nor ANSYS provide an option for defining different fatigue properties in different zones of the WJ, an innovative procedure was introduced and applied to simulate fatigue crack growth through different zones of the WJ and evaluate fatigue life more precisely than if the WJ is treated as a homogeneous material.

Effect of Laser Power on Weld Formability and Residual Stress of Unequal Thickness 410 Ferritic Stainless Steel/RCL540 Low-Carbon Alloy Steel.

In this paper, the butt joint of unequal thickness 410 ferritic stainless steel and RCL540 low-carbon alloy steel sheets are realized by laser welding. The effects of different laser powers on weld formability, mechanical properties, and residual stress in the welding process are investigated. It is observed that with increasing laser power, the heat accumulates at the bottom of the molten pool and weld metal, causing the ratios of upper and lower melt widths to decrease. The tensile test results show that all specimens fractured in the weak zone of the base metal on the stainless steel side at 10 mm from the weld seam. The residual stress distributions of the specimens are calculated using ABAQUS 2022 software and compared with the measurements of the blind-hole method. It is found that the stainless steel side produces tensile stresses, with the power increase offset by compressive stresses in the base metal. When the laser power is 1200 W, the welded joint has the best weld formability and mechanical properties and the least residual stress. The upper and lower melt width ratio is 1.17, the maximum microhardness of the weld metal is 374.7 HV, the maximum test force and tensile strength are 5617.5 N and 468.12 MPa, respectively, and the minimum values of the transverse and longitudinal stresses are -45.8 MPa and -106.4 MPa, respectively.

Atypical Attack of the Dissimilar Metal Welds of a Water–Water Energetic Reactor Nuclear Power Plant Secondary Circuit: Possible Mechanisms of Failure

ABSTRACTDissimilar metal welds are utilized in the energy industry to connect two materials with different material characteristics. In the case of nuclear power plants, the connected materials tend to be low‐alloyed steel and high‐alloyed material. Despite different material and corrosion properties, under the proper environmental conditions, the used construction materials and weld metals are protected either by a passive layer or by a high‐temperature oxide. Although dissimilar metal welds are used in both primary and secondary circuits, the most frequently documented damage is in the secondary circuit, where, in addition to material heterogeneities, local environmental heterogeneities may form. For dissimilar metal welds in WWER nuclear power plants, a water–water energetic reactor, a subtype of pressure water reactor, we note two main types of attack near the dissimilar fusion boundary: on the carbon steel side or on the high‐alloyed weld metal side (X10CrNiMoN16‐25‐6). The possible causes of the latter “atypical” corrosion attack are debated and can be generalized as a consequence of change of the grain boundary condition.

Microstructural and mechanical investigation of dissimilar U-groove weld of IN 718/ASS 304L employing ERNiCr-3 filler

This study investigates the dissimilar welding of Inconel 718 (IN 718) and austenitic stainless steel 304L (ASS 304L) using Gas Tungsten Arc Welding (GTAW) with Ni-based filler ERNiCr-3. IN 718 is valued for its high-temperature stability, oxidation, and corrosion resistance, while ASS 304L offers excellent ductility, formability, and corrosion resistance. The objective is to evaluate the impact of ERNiCr-3 on the weld’s metallurgical and mechanical attributes. The materials, prepared with U-groove edges, were optimized for manual multi-pass welding. Microstructural analysis revealed an austenitic matrix with dispersed Ti(CN) and NbC precipitates, enhancing strength through dispersion-strengthening mechanisms, with no solidification cracking due to Nb presence. FESEM/EDS and colour mapping identified elemental migration and stable carbide formation at the weld interfaces. Mechanical testing revealed uniform hardness within the weld zone and tensile resistance of 510 MPa, underscoring the robustness of ERNiCr-3 weld metal. These results indicate that ERNiCr-3 is highly effective for producing superior quality dissimilar welds amidst IN 718/ASS 304L, making it suitable for applications in elevated-temperature and mechanically demanding environments.

Estimation of Quality of Seam Welds in AlMgSi(Cu) Extrusion by Using an Original Device for Weldability Testing.

Extrusion welding of AlMgSi(Cu) alloys is carried out by using porthole dies, as a result of which hollow shapes are formed with longitudinal seam welds. In the case of the inappropriate selection of the chemical composition of the aluminium alloy or improper metal welding conditions, the weld may have reduced strength in relation to that of the base material, thus weakening the strength of structures based on aluminium extrudates. The prediction of metal welding conditions, depending on the chemical composition of the alloy, the temperature and the unit welding pressures, effectively supports the design of porthole dies, thus significantly reducing the number of necessary extrusion tests and die geometry corrections needed during its implementation in industrial practice, and consequently significantly reducing production costs. In this work, an original laboratory test device simulating the behaviour of metal in a welding chamber of a porthole die was applied to examine the ability of AlMgSi(Cu) alloys to produce high-quality joints. Two different chemical compositions of AlMgSi(Cu) aluminium alloys differing in Mg, Si and Cu contents were used: alloy no. 1A (0.68% wt. Mg, 1.04% wt. Si, 0.61% wt. Cu) and alloy no. 3A (0.8% wt. Mg, 1.21% wt. Si, 1.22% wt. Cu). The weldability tests were carried out under various welding temperatures of 450, 500 and 550 °C and under various welding pressures of 150 MPa, 250 MPa and 350 MPa. The microstructural changes in the produced welds were evaluated with the use of OM and SEM/EDS with chemical analysis in micro-areas, whereas the mechanical effects were evaluated by using a static tensile test. Samples after static tensile testing were subjected to fractographic tests to determine the nature of the fractures. The highest values of relative weld strength were obtained under the highest welding temperature of 550 °C and the highest unit welding pressure of 350 MPa: 87% for alloy number 1/1A (high-strength weld), and 62% for alloy number 6/3A (medium-strength weld). Finally, the extrusion tests were performed in industrial conditions with an examination of the EBSD structure and strength of the longitudinal welds. High values of relative weld strength for extrudates from alloy no. 1/1A and alloy no. 3A, 96% and 89%, respectively, were found, which confirmed the previous weldability testing results.

Microstructure, mechanical properties, and corrosion resistance of dissimilar weld joints between SS304 and Inconel 600 welded using gas tungsten arc welding

The microstructure, mechanical characteristics, and corrosion resistance of dissimilar gas tungsten arc welding (GTAW) joints of 304 stainless steel (SS304) to Inconel 600 (IN600) with Inconel 600, using ERNiCr-3 and ERSS308 filler metals were investigated. The welding process was executed at a current of 110 Amps under argon shielding gas, and all fabricated welds successfully joined SS304 to Inconel 600 without visible cracks or porosity at the weld metal interface. Microstructural analysis with optical and scanning electron microscopy revealed a mix of columnar and equiaxed dendritic structures in the weld zone for all samples. An unmixed zone was noted at the interface on the SS304 side when welded with Inconel 600 and ERNiCr-3, attributed to the differing melting points and chemical compositions of these fillers compared to SS304. The presence of Nb and Ti in the ERNiCr-3 filler facilitated the formation of TiC and NbC carbides in the welded metal structure, resulting in higher hardness compared to other specimens. Mechanically, the ERNiCr-3 welded sample exhibited superior hardness, with the highest microhardness values recorded in the ERNiCr-3 weld metal (197–207 HV) and higher values on the SS304 side (176–194 HV) compared to the IN600 side (164–176 HV). Corrosion tests, including Tafel and Electrochemical Impedance Spectroscopy, indicated that the ERNiCr-3 weld metal had better corrosion resistance than the IN600 weld metal. Due to the differences in chemical compositions of the base metals SS304 and IN600, it is necessary to consider an appropriate filler for welding these materials. ERNiCr-3 demonstrated increased hardness due to the formation of TiC and NbC carbides, along with enhanced corrosion resistance. These properties make it a promising material for industrial applications that require durability, strength, and resistance to corrosion, particularly in high-temperature or corrosive environments.

Investigation on solidification crack susceptibility for weld metals of GH3539 alloy with Trans-Varestraint test

In this work, the welding solidification crack susceptibility of GH3539 alloy was investigated under different strains using a trans-varestraint test. The results indicate that the saturation strain of GH3539 alloy reaches a bending strain of 1 %. High-angle grain boundaries in the weld metal are fragile areas where welding solidification cracks are formed due to element segregation and stress concentration, which are essential factors causing crack initiation and propagation. Furthermore, the surface residual stress of the crack tip was calculated by two-dimensional synchronous micro X-ray diffraction analysis of the partial Debye ring, which was deduced as the major factor for the cracking. The element Si in the alloy tends to segregate at grain boundaries, forming low-melting liquid films with elements such as Mo, Cr, and Mn during the final solidification stage. These liquid films reduce the interfacial bonding strength at the grain boundaries. The failure of the liquid films to accommodate local stress, resulting in subsequent interface separation, serves as the other catalyst for initiating solidification cracks in welding.

Effects of Nitrogen on Microstructure and Properties of SDSS 2507 Weld Joints by Gas Focusing Plasma Arc Welding.

Regulating the phase ratio between austenite and ferrite in welded joints is crucial for welding super duplex stainless steel. Nitrogen plays a significant role in maintaining an optimal phase ratio. In this study, the focusing gas channel of gas-focused plasma arc welding was utilized to introduce nitrogen into the arc plasma, which was then transferred to the weld pool. Experiments with and without nitrogen addition were designed and conducted to examine the effects of nitrogen on the microstructure and properties of SDSS 2507 weld joints. The results show that nitrogen addition increased the austenite content in the weld metal from 22.2% to 40.2%. Nitrogen also altered the microstructure of the austenite, changing it from thin grain boundary austenite and small intragranular austenite to a large volume of coarse, side-plate Widmanstätten austenite. The ferrite in the weld metal exhibited a preferred orientation during growth, while the austenite showed a disordered orientation. Additionally, the maximum texture intensity of the ferrite decreased with nitrogen addition. Nitrogen addition led to an increase in the microhardness of the austenite in the weld metal, attributed to the solid solution strengthening effect of nitrogen and increased dislocation tangling, while it decreased the microhardness of the ferrite. This study enhances the welding theory of 2507 super duplex stainless steel and guides the practical application of gas-focused plasma arc welding for 2507 super duplex stainless steel.

Study on the impact toughness and crack propagation behavior of Ti microalloyed weathering steel laser-MAG hybrid welded joints

In this work, the effect of Ti microalloying on the impact toughness of weathering steel laser-MAG hybrid welded joints was investigated and the corresponding crack initiation and propagation mechanisms were revealed. The results show that the impact toughness of heat affect zone (HAZ) increased by 39.4% and weld metal (WM) by 70.9% compared to Ti-free weathering steel welded joints. The degree of improvement in impact toughness gradually increases with the direction from BM (base metal) to WM. In the WM, Ti element can refine the precipitations and reduce the shape and size of M−A constituents. Furthermore, the microstructure in the WM exhibits the obvious preferred orientations, i.e., the maximum IPF intensity value are concentrated around the [111] pole (the slip direction of BCC structure), which is more prone to slip under external forces. In the HAZ, the addition of Ti mainly plays a role in decreasing the size of precipitations, inducing AF precipitation and increasing the homogeneity of grain size. Therefore, the impact toughness of WM and HAZ for Ti microalloyed weathering steel welded joints is improved by hindering the crack propagation. In addition, in the WM, the main crack path is flatter and the number of secondary cracks is more than that in the HAZ, indicating that the impact toughness of WM is poorer.

Study on the effect of flux composition on the melting efficiency of A-TIG of AISI 316L stainless steel: experimental and analytical approaches

Melting efficiency in welding is determined by various factors, including processing and operational parameters, the thermomechanical and chemical properties of the materials, surface conditions, and the type of energy source. This study uses a dimensionless parameter approach to evaluate melting efficiency by estimating the weld pool area through experimental measurements of the weld bead's diameter and depth. Also, this study investigates surface-active oxide fluxes based on SiO2 with Cr2O3 and Fe2O3 additives in TIG welding of 316L stainless steel. The effects of these fluxes on melting efficiency, weld cross-sectional area, microstructure, and mechanical properties at various currents (100-200A) were evaluated using metallographic, mechanical, and chemical analyses. The results show that using two-component fluxes at steady incident energy increased melting efficiency in the experimental approach by approximately 10% compared to single-component fluxes and by 20% compared to the without flux condition, providing more favorable and realistic outcomes than the analytical approach. This increase in melting efficiency resulted in a rise in the δ-ferrite phase (7.6% volume) and a reduction in the oxygen content (256 ± 10 ppm) in the weld metal. Furthermore, the two-component fluxes caused arc column constriction, which enhanced absorbed energy and led to an equiaxed grain microstructure with increased penetration depth. The weld metal's strength (630 ± 4 MPa) was directly linked to the penetration depth. However, the high absorbed energy caused grain growth, decreasing weld metal hardness (202 ± 2.5 HV) as melting efficiency increased.