Properties Of Welds Research Articles

Effect of cold metal transfer on corrosion properties of Duplex Stainless-Steel welds

Effect of cold metal transfer on corrosion properties of Duplex Stainless-Steel welds

Development of parametric window and optimization of process parameters to predict bead profile in magnetically controlled gas tungsten arc welding

A novel methodology has been proposed to tame the arc shape by adopting an external magnetic field, resulting weld profile as required. The co-axial magnetic field developed by specially designed electromagnets is superimposed on the welding arc. It was found that 0-0-S-N configuration provided more penetration than conventional gas tungsten arc welding. A parametric window has been developed for the selected configuration to obtain the desired bead geometry. The experiments were performed using process parameters as suggested by the design matrix, developed using response surface method technique. Mathematical models were evolved from experimental data for penetration and bead width. The evolved model for penetration is adequate up to 99.72% confidence level and for bead width is 99.98% confidence level. The effects of process parameters have been presented in a graphical manner for better understanding. The penetration achieved with the magnetically controlled GTAW process is 3.92 mm, which is 30% more than that achieved with conventional GTAW. The bead width increases initially, up to a certain limit, and then reduces with an increase in excitation current. Further, the experiments have been conducted on the optimized parameters for the validation of models. The refined grains were obtained due to magnetic stirring of the molten pool, which is desirable for improvement in mechanical properties of welds. The average grain size was reduced from 42.55 to 31.03 µm. The improved microstructure containing more amount of acicular ferrite was obtained with magnetically controlled arc.

Taguchi-Grey relational analysis driven multi-objective optimization of weld bead geometry and hardness in laser welded Ti6Al4V Alloy

AbstractThis study used Taguchi-based Grey relational analysis to optimize the bead geometry (bead width and length) and the hardness of laser welded 3 mm thick Ti6Al4V alloy sheets joined using the butt configuration. Firstly, the L9 (32) orthogonal array, with varying laser power and welding speed, was employed to optimize the input parameters (bead length, width, and hardness). The Taguchi optimization showed that the welding speed and laser power have a significant effect on the hardness of the welds and that laser power has a significant impact on the bead length. Meanwhile, the welding parameters had little effect on the bead width. These results were further affirmed with the Analysis of Variance (ANOVA). The Grey relational multi-objective optimization shows the optimized parameters for all responses to be 3 kW laser power and 2.2 m/min welding speed. It is important to note that the combination of Taguchi and Grey relational analysis and ANOVA is useful in optimizing welding parameters to achieve suitable weld properties.

Microstructure, Corrosion and Mechanical Properties of Medium-Thick 6061-T6 Alloy/T2 Pure Cu Dissimilar Joints Produced by Double Side Friction Stir Z Shape Lap-Butt Welding

A novel double side friction stir Z shape lap-butt welding (DS-FSZW) process was proposed to achieve excellent mechanical properties of Al/Cu medium-thick dissimilar joints. The influence of welding parameters on weld microstructure and properties of DS-FSZW joint were systematically investigated. It indicated that defect-free medium-thick Al/Cu DS-FSZW joint could be achieved under an optimal welding parameter. DS-FSZW joint was prone to form void defects in the bottom of the second-pass weld. The recrystallization mechanisms at the top and middle of the weld nugget zone (WNZ) were continuous dynamic recrystallization (CDRX) and geometric dynamic recrystallization (GDRX). While the major recrystallization mechanism at the bottom of the WNZ was GDRX. DS-FSZW joint of the optimal welding condition with 850 r/min-400 mm/min was produced with a continuous thin and crack-free IMCs layer at the Al/Cu interface, and the maximum tensile strength of this joint is 160.57 MPa, which is equivalent to 65.54% of pure Cu base material. Moreover, the corrosion resistance of Al/Cu DS-FSZW joints also achieved its maximum value at the optimal welding parameter of 850 r/min-400 mm/min. It demonstrates that the DS-FSZW process can simultaneously produce medium-thick Al/Cu joints with excellent mechanical performance and corrosion resistance.

THE EFFECT OF LASER OSCILLATING WELDING ON FORMATION AND PROPERTIES OF TITANIUM ALLOY

Titanium alloys are widely used in aerospace and other fields due to their advantages of low density, high specific strength and good corrosion resistance. Laser oscillating welding is an innovative process in the realm of welding technology. In this study, two laser oscillating welding methods (circular and linear) were employed to analyze the influence of different oscillation parameters on the formation of titanium alloy. The results indicate that the oscillation frequency has a significant impact on weld formation. The laser scanning trajectory also affects weld formation, with circular and linear scanning trajectories resulting in better weld quality. Finally, the effects of oscillation modes on the microstructure and properties of laser oscillating welding titanium alloy were investigated based on optimized process parameters. Among them, circular laser oscillating welding of titanium alloy exhibits higher tensile strength, with a maximum tensile strength of up to 1188.3[Formula: see text]MPa.

The influence of tool shoulder size and plate position on the characteristics of friction stir welded different aluminum alloys

ABSTRACT Welding is a main manufacturing method for fabricating various engineering components. Fusion welding techniques encounter solidification associated problems while joining light weight structures. Friction stir welding is a solid state welding technique that is developed to address these shortcomings. As the superior conductive properties of AA6101-T6 and AA1350 aluminum alloys, they are frequently utilized in electrical industries. The goal of this study is to examine how the plate position and tool shoulder diameter (D) affect the qualities of these dissimilar Al-alloys joints. It is discovered that plate positioning is the most influential welding parameter in determining the tensile properties of weldment. Furthermore, the joint fabricated with AA6101-T6 as an advancing side material and a 15 mm tool shoulder diameter produces sufficient weld reaction temperature, better plastic flow and tensile properties. However, the joint fabricated with AA1350 as an advancing side material and 12 mm tool shoulder diameter generates inadequate reaction temperature, poor plasticization, and tensile properties. The formation of precipitates as well as the interface layer at the weld nugget is greatly dominated by the tool shoulder size, which affects the wear properties of weldment.

Parameter optimization, microstructural and mechanical properties of fiber laser lap welds of DP1200 steel sheets

In this research, the effects of laser power, laser welding speed and laser incidence angle were evaluated in terms of weld geometry, microstructure, microhardness, fracture surfaces and tensile shear load in fiber laser welding joints of DP1200 steel sheets. Response Surface Methodology (RSM) was utilized to derive mathematical relationships between the process parameters and the tensile shear load after the tensile test. The optimum combination of process parameters was a laser power of 2800 W, a laser welding speed of 40 mm/s, and a laser incidence angle of 70°. A thermal camera was used to record the laser welding process, and the cooling rates were evaluated by analyzing this data. The influence of cooling rate upon microstructure phase formation for DP1200 steel is investigated, with continuous cooling transformation (CCT) diagrams. Also, post-welding stress and displacement were simulated by Simufact Welding software. At high heat input (55.79 J/mm) occurred coarse dendritic martensitic lath growth while at low heat input (37.6 J/mm) fine dendritic martensitic structure was observed in the weld zone was obtained owing to the high rate of cooling. The microstructure consists of full martensite at a higher than 10 °C/s cooling rate. The findings reveal that the phases in FZ and HAZ, the morphology and martensite/bainite constituents differed related to the heat input and laser incidence angle, which ultimately affects the joint’s microhardness, fracture dynamics and tensile shear load.

Failure of dissimilar QP980/DP600 advanced high strength steels resistance spot welds

This study investigates the microstructure, failure characteristics, and mechanical properties of dissimilar resistance spot welds between QP980 quenching and partitioning steel and DP600 dual phase steel. The dissimilar spot welds exhibited a heterogeneous microstructure, with a fusion zone predominantly composed of martensite, significantly overmatching both base materials. A fully martensitic structure with grain size gradient was observed in the upper-critical heat affected zone (UCHAZ) on both sides of the dissimilar joint. In the sub-critical heat affected zone (SCHAZ), no significant phase transformation occurred on both sides. However, at high welding currents, a slight tempering of pre-existing martensite was detected on the QP980 side resulting in a minor hardness drop in this zone. There was a critical welding current at which the failure mode was changed from interfacial mode to pullout mode. The dissimilar QP/DP joint showed a lower tendency to fail via interfacial failure mode compared to similar QP/QP and DP/DP joints, attributed to a higher fusion zone hardness overmatching factor and greater nugget rotation. Pullout failure of dissimilar QP/DP combination was assessed in detail through interrupted tensile shear test. It was found that failure at stronger QP980 side occurred by ductile cracking mechanism initiated from the notch tip, while failure at softer DP600 side occurred by through-thickness localized necking. The former was found to be the prior failure mechanism controlling the load bearing capacity of the dissimilar joint. The mechanical properties of dissimilar QP/DP joints were discussed in terms of peak load and energy absorption, and then were compared to those of similar DP/DP and QP/QP joints in the light of weld microstructure and failure mechanisms.

Effect of pre-strain on microstructure evolution and fracture behavior of undermatching X80 pipeline steel girth weld

This work aims to study the effect of pre-strain on the fracture behavior of X80 pipeline girth weld joint, a comprehensive analysis was conducted on the microstructure and mechanical properties of the girth weld before and after pre-strain treatment. The mechanical properties were evaluated through tensile testing, Charpy impact testing, and digital image correlation (DIC) strain analysis. Furthermore, the microstructure and fracture morphology of the girth weld were observed using optical electron microscopy (OM) and scanning electron microscopy (SEM). The results show that the application of pre-strain treatment leads to dislocation accumulation at the grain boundary of X80 pipeline girth weld, resulting in stress concentration and subsequent formation of damage holes. This process disrupts the continuity of chain M-A island and initiates small cracks at the grain boundary, ultimately causing a significant decrease in impact toughness and impact work from 177 J to about 10 J.

Rotary friction welding of 304 stainless steel: parametric study, mechanical properties, and microstructure of the joint

In the rotary friction welding process, the selection of process parameters affects the friction, heat generation, and joint formation. These factors collectively cause microstructural changes that determine the mechanical properties of the joint. Therefore, the process parameters, microstructure, and mechanical properties were interconnected during rotary friction welding. This study examined the influence of process parameters on their correlation with microstructure and mechanical properties in the rotary friction welding of 304 SS. A 3×4 full factorial experimental design was used to evaluate the effects of the process parameters on the microstructure and strength of 304 SS joints produced through rotary friction welding. An accurate evaluation of joint strength was performed using the notch tensile test technique. The joint with the highest strength was achieved by applying a combination of friction pressure and friction time at 55 bars and 3 seconds, respectively, resulting in a welding efficiency of 103.6%. A very low friction time (i.e., 5 s) produced a weak joint, which should be avoided. The welding process created three distinct structural zones in the joint: a joint structure finer than the parent metal structure, a partially deformed structure, and a heat-affected zone with deformation. Hardness tests of the joints showed a high hardness in the deformed structure. The formed structure contributes to the resulting joint strength.

A Study on the Microstructure and Mechanical Properties of Electron Beam Welds of SA508 Gr.3 Cl.1 steel with Different Heat Treatment conditions for Small Modular Reactor

Electron beam welding was conducted on SA508 Gr.3 Cl.1 steel, which is being considered as a material used in the pressure vessel steel of small modular reactors. The characteristics of the welds were analyzed under various heat treatment conditions. The heat treatment conditions were categorized as as-welded, post weld heat treatment(PWHT), quality heat treatment(QHT), and their features were examined and compared through cross-sectional structure and composition analyses, as well as mechanical property tests. The electron beam welded joints displayed no defects, including pores or cracks. weld metal of the as-welded specimen revealed a needle-type martensite with high hardness, whereas the base metal was characterized by tempered bainite. The weld cross-section bead of the QHT specimen exhibited no significant difference in microstructure compared to the base metal. Tensile testing revealed that both the as-welded and PWHT specimens fractured at the base metal, whereas the QHT specimen fractured at the weld metal. The PWHT specimens showed enhanced impact values in the welds compared to the as-welded specimens. In the QHT specimens, both the base metal and the weld metal demonstrated similarly favorable impact values, approximately 200 Joules. It is evident that post-welding heat treatment improves the toughness value, and quality heat treatment can result in the weld metal being similar to the base metal.

Comparison of SMAW and GTAW Welding Properties

Low carbon steel is a type of welding with good formability, machinability, hardenability, and weldability. It can be welded without preheating or postheating processes. Notch strength and sensitivity to weld cracking are the factors that influence the weldability of low carbon steel. SMAW and GTAW welding techniques were applied in this study. In addition to its mechanical properties, parameters and the type of welding process also affected the corrosion of the welded joint. Local corrosion attacks were easier to occur on one than the other welded joint due to significant differences in chemical composition and microstructure. Welded joints in a chlorine-rich environment have a high corrosion rate. In comparison to base metal, low-weld metal triggers high corrosion.

Exceptional grain refinement induced by dispersed MgO particles in TIG-welded AZ31 alloy

Due to the low content of alloying elements and the lack of effective nucleation sites, the fusion zone (FZ) of tungsten inert gas (TIG) welded AZ31 alloy typically exhibits undesirable coarse columnar grains, which can result in solidification defects and reduced mechanical properties. In this work, a novel welding wire containing MgO particles has been developed to promote columnar-to-equiaxed transition (CET) in the FZ of TIG-welded AZ31 alloy. The results show the achievement of a fully equiaxed grain structure in the FZ, with a significant 71.9% reduction in grain size to 41 µm from the original coarse columnar dendrites. Furthermore, the combination of using MgO-containing welding wire and pulse current can further refine the grain size to 25.6 µm. Microstructural analyses reveal the homogeneous distribution of MgO particles in the FZ. The application of pulse current results in an increase in the number density of MgO (1-2 µm) from 5.16 × 104 m−3 to 6.18 × 104 m−3. The good crystallographic matching relationship between MgO and α-Mg matrix, characterized by the orientation relationship of [112‾0]α−Mg//[01‾1]MgO and (0002)α−Mg//(111)MgO, indicates that the MgO particles can act as effective nucleation sites for α-Mg to reduce nucleation undercooling. According to the Hunt criteria, the critical temperature gradient for CET is greatly enhanced due to the significantly increased number density of MgO nucleation sites. In addition, the correlation with the thermal simulation results reveals a transition in the solidification conditions within the welding pool from the columnar grain zone to the equiaxed grain zone in the CET map, leading to the realization of CET. The exceptional grain refinement has contributed to a simultaneous improvement in the strength and plasticity of welded joints. This study presents a novel strategy for controlling equiaxed microstructure and optimizing mechanical properties in fusion welding or wire and arc additive manufacturing of Mg alloy components.

INVESTIGATION OF THE EFFECT OF SMAW PARAMETERS ON PROPERTIES OF AH36 JOINTS AND THE CHEMICAL COMPOSITION OF SEAWATER

Underwater wet welding (UWW) is a critical technique for repairing offshore structures, underwater pipelines, water transport infrastructure, docks, and harbor equipment. In this study, the mechanical and microstructural properties of AH36 low-carbon steel weldments were investigated using metal arc welding (SMAW), an underwater wet welding method, at various welding current strengths and seawater temperatures. The relationship between changes in seawater temperature and welding current parameters and their impact on seasonal variations in welding conditions and seawater composition was examined. In the first stage, the yield strength of AH36 was statistically modeled using a central composite design with input parameters of seawater temperature (ranging from 9.7 °C to 25.3 °C) and source current value (ranging from 49A to 90A). Optimal conditions were determined, resulting in a yield strength of 270MPa, achieved at a seawater temperature of 17.5 °C and a source current value of 69.5 A. In the second stage, data from optimization studies were utilized to develop elemental exchange equations for Cr (R2=87.3), Ni (R2=64.45), and Mn (R2=65.74) ions in seawater. The findings reveal that source current intensity primarily influences changes in Cr content in seawater, seawater temperature is correlated with Ni content, and both current intensity and seawater temperature affect the Mn content. The analytical techniques employed include Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for seawater ion analysis, Energy Dispersive Spectroscopy (EDS) point analysis to determine the chemical composition of AH36, and Scanning Electron Microscopy (SEM) for microstructural analysis

Enhancing load-bearing capacity of martensitic stainless steel resistance spot welds: Microstructural vs. geometrical approaches

The load-bearing capacity of resistance spot welds is determined by a combination of weld geometrical attributes, such as the size of the weld nugget (WN), and weld metallurgical features. When resistance spot welds are made on martensitic stainless steels (MSSs), their load-bearing capacity is reduced due to the formation of a brittle martensitic microstructure within the WN. In this study, we investigated two distinct approaches to enhance the mechanical properties of AISI420 MSS spot welds. The results indicated that manipulating the WN size did not effectively produce strong welds in both tensile-shear (TS) and cross-tension (CT) tests. Therefore, we focused on examining the impact of the weld microstructure by employing two different interlayers: low carbon steel (LCS) and pure nickel. The analysis using electron backscatter diffraction (EBSD) and electron probe microanalysis (EPMA), along with equilibrium and non-equilibrium phase diagrams, revealed that the microstructure of the WN with low carbon steel interlayer of various thicknesses exhibited similarities with spot welds made without an interlayer, and the solidification mode was still δ-ferrite. This microstructure primarily consisted of martensite (M) and likely residual delta ferrite (δ) phases, resulting in no significant improvements in mechanical properties. In contrast, the utilization of the nickel interlayer led to remarkable enhancements in mechanical properties. This improvement can be attributed to a shift in the solidification mode from primary delta (δ) to austenite (γ) within an optimal interlayer thickness. This transition facilitated the development of a predominantly austenitic (γ) microstructure, contributing to the formation of an exceptionally tough microstructure within the weld nugget. Consequently, the load-bearing capacity was significantly improved.

Fabrication of tungsten inert gas-welded dissimilar aluminium joints using different friction stir processing tools through response surface method

ABSTRACT AA6061-T6 and AA7075-T6 materials find wide application in manufacturing industries due to their excellent engineering properties. Fusion welding generates solidification cracks, high residual stresses, and brittle intermetallic compounds that degrade joint qualities. To solve these difficulties, friction stir processing (FSP) is frequently employed, which improves joint properties through local microstructural refinement. In this study, the combined effect of FSP parameters, namely tool pin profile (TPF), tool rotation speed (TRS), and travel speed (TS), on tungsten inert gas (TIG) weld properties was investigated. Response surface methodology (RSM)-based mathematical models were developed to predict responses, namely ultimate tensile strength (UTS), impact toughness (IT), microhardness (MH), and residual stress (RS). The optimal FSP parameters were determined through the desirability function technique. Post-FSP increased the UTS, IT, and MH of TIG welds by 71.51%, 95.40%, and 72.46%, respectively, and decreased the RS by 58.46%. ANOVA findings exhibited that TPF was the most influential parameter, followed by TRS and TS. The dissimilar aluminium TIG+FSP joints showed an optimal UTS of 282.08 MPa, an IT of 17.32 J, a MH of 121.48 HV, and an RS of 22.09 MPa when using a TRS of 1108.49 rpm and a TS of 37.74 mm/min with a THF pin.

Effect of Friction Time on Temperature Distribution, Plastic Flow, Microstructure, and Properties in Friction Welding of 1045 Carbon Steel and AISI 430 Ferritic Stainless Steel

Effect of Friction Time on Temperature Distribution, Plastic Flow, Microstructure, and Properties in Friction Welding of 1045 Carbon Steel and AISI 430 Ferritic Stainless Steel

Underwater wet welding of high-strength low-alloy steel using self-shielded flux-cored wire with highly exothermic Al/CuO mixture

Underwater wet welding processes with minimal energy consumption and high efficiency is the future goal for researchers in the field. Al/CuO exothermic mixtures in consumables for land welding process can improve welding process stability and decrease the electrical dependence of the welding process. To confirm the beneficial effects of Al/CuO thermite and gain a better understanding of metallurgical properties of the thermite welds in underwater environment, this study investigated underwater wet self-shielded flux-cored arc welding (FCAW-S) of high-strength low-alloy steel with highly exothermic Al/CuO mixture. The effects of Al/CuO thermite on arc stability, weld metallurgical behavior and melting characteristics of flux-cored wire were clarified. The ratio of chemical heat in the flux to the heat required to melt welding wire increased from 4.7% to 38.4% with the addition of Al/CuO, potentially accelerating the melting of flux-cored wires. The arc stability with thermite addition was superior to that without the addition of thermite. The presence of copper as a result of metallurgical reactions had a substantial impact on metallurgical behavior of underwater wet welds. The ferrite weld was a non-equilibrium Cu supersaturated solid solution, which increased the microhardness and tensile strength of wet welds. The measured cooling time proved that the incorporation of Al/CuO had the capacity to reduce cooling rate. The incorporation of 50 wt% thermite yielded a 7.8% increase in welding process efficiency compared to the base formulation. Current work provided an important direction for the development of a chemically self-heating flux-cored wire.

Microstructure and properties of laser welding Ni-based alloy/austenitic stainless steel with filler wire for nuclear reactor pump can end sealing

The current study investigates the microstructure and properties of laser welding involving Hastelloy C-276 and 304 stainless steel with filler wire, which is closely related to nuclear reactor pump can end sealing. The experimental results indicate the presence of an unmixed zone (UZ) and a small amount of Mo-rich secondary phase in weld seam, and microstructure of UZ is composed of austenite and ferrite phases. Laser welding enhances the ratio of low-angle misorientation and the uniformity of elements macro-distribution. The end sealing property of nuclear reactor pump can is characterized by anti-peel property of weld joints. The welded joint has local fracture and through fracture in the test of anti-peel property. The weld with local fracture exhibits superior anti-peel property. The joint crack starts at the bottom of the UZ. The anti-peel property of the welded joint is 239.6 ± 4.7 N/mm and mainly related to the weld penetration. The corrosion property of welded joints is determined by the elements of the weld, and the welded joints showcasing a better integral corrosion property than that of 304 base metals. Laser welding Ni-based alloy/austenitic stainless steel with filler wire has significant technical advantages for end sealing of nuclear reactor pump can.

Improving bonding strength of medium-thick Al-Cu dissimilar joint by a novel splat cooling assisted double side friction stir welding

To obtain a high-strength medium-thick Al-Cu dissimilar joint, a novel splat cooling assisted double side friction stir welding (SDS-FSW) is proposed. The microstructure and tensile properties of conventional double-side friction stir welding (DS-FSW) and the novel SDS-FSW joints under optimal welding parameters are systematically compared, it shows that the utilization of in-process splat cooling significantly reduces the welding peak temperature and the high-temperature dwell time. The in-process splat cooling causes significant grain refinement in the welding nugget zone (WNZ) of the Al-Cu dissimilar SDS-FSWed joint, it exists the lower recrystallization fraction and the higher KAM value. Although both DS-FSW and SDS-FSW joints fracture at the Al-Cu interface, the DS-FSW joint represents a brittle fracture characteristic, while the SDS-FSW joint represents a mixed ductile-brittle fracture mode. Under the drive of the mechanical stirring of the tool and the welding thermal cycle, the aluminium atoms and copper atoms diffuse to the copper base material and aluminium base material, respectively. Since copper diffuses in aluminium at a higher diffusion rate than aluminium diffuses in copper, and the solubility of copper in aluminium is much smaller than that of aluminium in copper, thus the Al2Cu becomes the first phase with the nucleation and growth. As the welding temperature and time continue to increase, Al2Cu reaches the supersaturation state, and the Al4Cu9 phase is produced between the Cu (Al) and the Al2Cu phase. In the end, the interface forms the stable double-layer IMCs structure (Al2Cu/Al4Cu9). The optimal tensile strength of the SDS-FSWed joint is 159 MPa, which is increased by 42% compared to the DS-FSWed joint at the same welding parameter. This was mainly because in-process splat cooling contributed to forming a thinner IMCs layer at the A-Al-Cu interface. It reveals that the application of in-process splat cooling is a versatile method to thin the IMCs layer at the Al-Cu medium-thick DS-FSW process.