Double-sided Welding Research Articles

Fatigue failure and optimization of double-sided weld in orthotropic steel bridge decks

Double-sided weld is an effective way to improve the fatigue performance of orthotropic steel bridge decks (OSBD). However, the fatigue performance and optimization design methods of double-sided welds connecting the U-rib and the deck in OSBD require further study. In this paper, the finite element modeling method suitable for the notch stress approach in double-sided welds is discussed, and its variance from that of the single-sided weld is revealed. All possible fatigue failure modes of double-sided welds, the transfer phenomenon of fatigue crack initiation location and the change of fatigue failure modes under different vehicle loading conditions are revealed. It is further discussed that how the change of the deck plate thickness and the weld foot length alters the fatigue failure mode under the same loading condition. According to the above analysis, in order to obtain the optimal fatigue performance of double-sided welds, an optimal design method based on the fatigue damage factor per unit time under real vehicle loading conditions is proposed. The analysis results show that the fatigue failure modes of the double-sided welds of the U-rib-to-deck welded joint in the OSBD is determined by three factors: loading condition, deck plate thickness and weld foot length. According to the optimization factor proposed in this paper, the thickness of the deck plate and the length of the weld foot can be reasonably determined under different traffic loading conditions, so that the fatigue performance of the rib-to-deck joint in the OSBD is optimized.

A Study on the 2060-T8/2099-T83 Aluminum-Lithium Alloys T-Joints Welded by Double-Sided Laser Beam Welding

The mechanical properties of 2060 and 2099 T-joints welded by double-sided laser beam welding were analyzed in this experiment. Various mechanical tests were performed to determine the transverse tensile properties of the region perpendicular to the weld, the tensile properties of the skin and stringer, the compressive properties of the region parallel to the weld seam, and the fatigue properties perpendicular to the weld seam. The T-joint was found to consist of the base metal, partial melting zone, equiaxed zone (EQZ), columnar crystal zone, and cellular dendritic zone from the base metal to the center of the weld seam. The EQZ was proved to be the weak area during mechanical properties tests of the T-joint. Moreover, the welding penetration had a great influence on the transverse tensile properties and weak areas were located in the EQZ near the lower fusion line. The EQZ near the upper fusion line was the weak area in the process of compression. In addition, severe porosities and cracks greatly influenced the mechanical properties of the joint. The fatigue property was closely related to the deformation angle; the fatigue source was located at the weld toe, and the crack propagation was along the base metal.

Effects of heat treatment on microstructure and mechanical properties of double-sided laser-welded AA2060/AA2099 T-Joint

Abstract AA2060/AA2099 Al-Cu-Li alloys were connected via double-sided laser welding using ER4047 Al-Si filler wires, and the joint was subjected to two kinds of post-weld heat treatment: artificial aging (AA, 165 ℃ ×20 h) and solution treatment and AA (STAA, 500 ℃ ×1 h + 165 ℃ ×20 h). The principal strengthening phases of the base metals are the T1 (Al2CuLi) and δ’ (Al3Li) phases. The welding process resulted in the dissolution of T1 and δ’ phases, and the formation of T (AlLiSi) and Cu-rich phases in the grain boundary (GB) of the fusion zone (FZ). The δ’ phase was reprecipitated in the FZ and the T phase in the GB was characterized by an increase in the number and volume fraction when the as-welded (AW) joint was subjected to AA. In addition, the reduction of the Cu-rich phase in the GB, the reprecipitation of T1 phase in the FZ, and the spheroidization of the T phase with a uniform distribution occurred for the STAA joint. The AW joint had a tensile strength (TS) of 390 MPa and elongation (El) of 0.3%, while the AA joint had a TS of 458 MPa and El of 0.7%. The formation of the δ’ phase in the FZ and the increasing in the number and volume fraction of the T phase were responsible for the improvement of the tensile properties. The STAA joint had the highest TS of 490 MPa and El of 2.7%. The reprecipitation of the T1 and δ’ phases, and the smallest inter-particle spacing in the FZ led to the best tensile properties when the AW joint was subjected to STAA.

MIG-TIG double-sided arc welding of copper-stainless steel using different filler metals

Copper-stainless steel joints are achieved with sound double-sided appearances using Cu-based, Cu-Ni-based and Fe-based filler metals. The weld zone in the Cu-based filled joint consists of a uniform structure with the Cu solid solution (s,s) phase. The mixture of immiscible Cu and Fe causes weld segregation to appear in the other two joints. The weld zones with mixed phases in the Cu-Ni-based and Fe-based filled joints show higher impact toughness than the weld zone in the Cu-based filled joint. The maximum tensile strength is obtained from the Cu-based filled joint, which can reach up to 80 % of copper tensile strength. The decreased dislocation density and grain-coarsening under the annealing effect softens the heat-affected zone (HAZ) on the copper side of all three joints, making them a fracture zone during tensile tests. All the joints fracture with a ductile mode, and the plastic deformation concentrates on the softened copper side. The Cu-based filled joint exhibits the highest plastic deformation, which is primarily caused by the large deformation of the weld zone and the large deformation of the Cu base metal caused by the high plasticity of the weld that alleviates the stress concentration.

Double-Sided Welding as an Alternative for Joining Internally Clad Pipes

AbstractHigh strength steel pipes internally clad with nickel (Ni) superalloys are components widely used in the oil and gas industry in the production of rigid risers. The joining of clad pipes is...

Microstructure and mechanical properties of low power pulsed Nd:YAG laser welded S700MC steel

Thermomechanically controlled processed steels have gained attention increasingly by many industries. In this research S700MC steel is successfully welded using low power pulsed Nd:YAG laser and the microstructure and mechanical properties are investigated. It is shown that the average power and overlapping factor both affect the weld geometry. Full penetration with double-sided welding achieved on 2 mm thick plates autogenously. Optical metallographic methods and SEM/EDS were used to evaluate the resulting microstructures. The evaluations revealed that the weld metal microstructure contains different morphologies of ferrite such as acicular, allotriomorphic and Widmanstatten as well as bainaite and martensite structure in the weld zone. Also, no noticeable heat affected zone was detected near the fusion zone of the weldments. In addition to microstructures investigation, micro hardness and tensile tests were performed to evaluate mechanical properties. Hardness measurement results exhibit higher hardness values in weld zone than that of in the base metal. The tensile test revealed a ductile fracture behavior which happened in the base metal, due to proper weld zone microstructure. The strength and elongation of the prepared joints were 774 ± 14 MPa and 26.5 ± 2.5%, respectively.

Welding L415/316L Bimetal Composite Pipe Using Post-Internal-Welding Process

The butt welding of bimetal composite pipes generally adopts single-side welding, which easily gives rise to the problems such as high cost or crack initiation. In this paper, the butt welding of L415/316L bimetal mechanical lined pipes was conducted using post-internal-welding process, which is double-side welding process, proposed by the authors. Firstly, the effect of groove shape on the weld process was discussed. Then, microstructures and mechanical and corrosion-resistance properties of welded joints welded using two different welding materials, 309MoL and 309L, were investigated. The results show that the most suitable groove is that L415 is V shape with angle of 60° and blunt edge of 1 mm and 316L is stripped 6–8 mm. The weld of both 309MoL and 309L is composed of austenite and a small amount of ferrite, but the presence of Mo can refine the grains and increase the content of ferrite phase. The width of transition layer is about 0.6–0.8 mm located at the weld junction of stainless steel weld and carbon steel weld, and the transition layer mainly contains martensite. The tensile and bending performances of the welded joints using both 309MoL and 309L do meet the standard requirements. The welding wire 309MoL can improve the corrosion resistance to Cl− compared to 309L. It is advisable to use the post-internal-welding process and 309MoL for the welding of bimetal composite pipes under environments containing Cl−.

Ways to improve welding operations in construction of oil product storage tanks

It is shown that in order to further increase the welding rate in the construction of oil product storage tanks, fi rst of all it is necessary to develop and implement high-performance methods for double-sided arc welding of vertical joints. It is noted that the most useful technique to increase the welding rate and the quality of vertical joints on the side walls of the tanks is to replace single-arc automatic welding with multi-arc welding in gas-shielded or gas mixtures. Whereby the method exhibiting the most promise for is the double-sided synchronous welding. In this case, two arcs on the both sides of the workpiece are involved in the weld formation. It is determined that for the formation of technical requirements for the welding process and needed welding equipment, and for their implementation in multi-arc welding of vertical joints, it is necessary to conduct comprehensive study of multiparameter relationship between the double-electrode welding modes and the quality of the welded joints in the construction of oil product storage tanks based on physical and mathematical modeling.

Effect of Structural State of Metal in Weld Fusion Zone of Large-Diameter pipes on Fracture Mechanism and Results of Crack-Resistance (CTOD) Tests

We describe a study of fractures and metal structure in the fusion zone (FZ) and weld center (WC) for longitudinal welds and base metal (BM) in large-diameter pipe with strength class K60 (Grade X70) tested for crack resistance including a determination of the crack tip opening displacement (CTOD) on through-cut SENB samples (N-P per BS EN ISO 15653). Tests indicated that CTOD–20 (at temperature–20 °C) is generally more stable for BM and WC metal than for FZ metal. The effect of crack front displacement from the specified location on measured CTOD–20 values was studied for FZ samples. The CTOD–20 values for the FZ metal were found to depend on the failure mechanism caused by initiation of the fatigue crack, including maximum fatigue-crack length and maximum ductile-failure segment length. The structure of the FZ metal along the fatigue crack front was studied at various crack resistance levels using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The failure mechanism and resultant CTOD values for FZs in double-sided welds depend not only on the structural characteristics of the metal in the heat-affected zone (HAZ) (ratio of lath-like bainite to granular bainite, the martensitic-austenitic (MA) component and cementite morphology), but also on whether or not a fatigue crack is present in the section of pipe base metal where the deformation is largest. This differentiates the CTOD samples from the KCV samples. The fact that the BM area is located at the crack front has a substantial effect on the fracture mechanism in a FZ CTOD.

Morphology and crystallography of lath martensite in weld metal of high strength steel by double sided laser welding

The morphology and crystallography of the lath martensite in the weld metal of high strength steel by double-sided hybrid fiber laser-arc welding were investigated. The lath martensite was found to have Kurdjumov-Sachs orientation relationship. The amount of the lath martensite in the block was affected by the cooling direction of the weld pool. All the four packets were distributed randomly within a columnar grain. The blocks were approximately in square shape. All the 24 variants appeared within the columnar grain and some regions included certain combinations of two particular variants. The lath martensite in the weld metal had preferred orientation which was lath martensite (1 1 1) ‖ substrate surface.

Abnormal grain growth in a double-sided friction-stir welded Al-Mg-Si alloy

In this work, a standard T6 tempering (involving solution annealing followed by artificial aging) was employed to a fine-grained Al-Mg-Si alloy produced by double-sided friction-stir welding (FSW). The material was found to exhibit abnormal grain growth, thus demonstrating a relatively low thermal stability. The kinetics of abnormal grain growth in the joint was studied.

Join Al–steel dissimilar metal by novel high frequency electric cooperated arc welding

ABSTRACTA novel high frequency electric cooperated arc welding method (HFAW) was developed to join aluminium and steel of 3.0 mm thickness without groove. Owing to the skin effect and proximity effect of high frequency current, a part of welding heat was directly distributed all over weld side wall. Consequently, sound double-sided weld formation was achieved under a low MIG heat input and high welding speed. The average thickness of interfacial layer was limited to 2.3 µm. Benefitted from the balanced heat input and thin interfacial layer, the failure mode of the HFAW joint was necking at Al base metal. For traditional MIG joint, however, poor back weld formation and thick interfacial layer resulted in spontaneous fracture at interface.

Аpplication Development for the Evaluation of Penetration in Laser and Laser-Arc Hybrid Welding of Tee and Corner Joints

Laser technologies deservedly take their place in modern mechanical engineering production. Using laser source for welding has already become common. However, the creation of critical welded constructions is impossible without extensive technological surveys, which can be greatly simplified by using a computational experiment. To achieve this goal, special programs are usually used. That can be unjustified difficult and thereby awkward for technological practice. The article describes an application built on the basis of a simplified model for calculating the temperature field for the cases of laser and laser-arc welding of internal fillet welds as well as single-sided T-joints and simultaneous double-sided welds. The results of calculations by the model and comparing them with experimental data have shown that it is sufficiently adequate for use in technological purposes. The developed application contemporaneously has a simple and intuitive interface, does not require significant computational resources and can be used for quick preliminary estimation of the result of welding for the selected type of weld.

Evaluation of the Microstructure and Performance of Fe-21Cr-15Ni-6Mn-Nb Nonmagnetic Stainless Steel Welded Joints

In the present study, double-sided gas shield welding (GSW), in a single pass, was applied to Fe-21Cr-15Ni-6Mn-Nb nonmagnetic stainless steel plate. The microstructure and performance of the welded joint were investigated via microstructural and phase analysis, mechanical testing and magnetic analysis. The results showed a satisfactory micrographic appearance with full penetration, and no solidification defects observed in the welded joint, which showed typical epitaxial growth characteristics in the welding solidification. Slight grain growth, with an average size of ~ 18.9 μm, occurred in the heat-affected zone (HAZ). The primary dendrite arms, on both sides of welding joint, grew along the direction of the temperature gradient and met at the centerline of the weld with no parting microstructure in evidence. The secondary dendrite arm spacing was stable in all parts of the weld zone (WZ). The hardness of the weld zone was higher than that of the HAZ and the base metal (BM), with the lowest hardness occurring in the HAZ. The results of tensile testing showed a higher strength of the welded metal (WM) compared to the BM, and a good strength-ductility balance of the welded joint. The impact energy of the HAZ was higher than that of the WZ, corresponding to 60.5 J at room temperature and 52.7 J at − 196 °C. Microvoid coalescence, concurrent with crack propagation along the direction of the long axis of the dendritic sub-grains, was observed during plastic deformation in the WZ. Additionally, the excellent paramagnetic characteristics of the welded specimens were revealed.

Thermomechanical Analysis of A-TIG and MP-TIG Welding of 2.25Cr-1Mo Steel Considering Phase Transformation

In the present study, a finite element-based 3D mesh model is used to simulate the effect of welding processes on the temperature distribution, residual stress and distortion in 11-mm-thick 2.25Cr-1Mo steel weld joints. Tungsten inert gas (TIG) and activated-TIG (A-TIG) welding processes were employed for the fabrication of weld joints. Austenite-to-bainite phase transformation is taken into account in the numerical analysis. The heat input fitting tool has been used to calibrate the heat source by matching the simulated weld bead with that of the actual weld bead. Peak temperature was higher at the weld center for A-TIG weld joint, and the weld joint exhibited a sharp temperature gradient at the weld interface. There was good agreement between the predicted and measured thermal cycles. A-TIG and multipass-TIG (MP-TIG) weld joints exhibited similar longitudinal residual stresses in heat affected zone with a difference of 50 MPa. Moreover, A-TIG weld joint fabricated by double-side welding technique employing two passes exhibited reduced distortion than MP-TIG weld joints. A higher magnitude of distortion was in MP-TIG weld joint which was attributed to more weld metal volume caused by more number of weld passes required to fill the V-groove. There was good agreement between the predicted and measured residual stress and distortion values.

Effect of Process Parameters on Structure and Mechanical Properties of Friction Stir Welding Joint of 5052 Aluminum Alloy

2.5 mm thick sheets of AA5052 were welded using friction stir welding technology. The effects of welding speed, rotational speed of pin, length of pin, single-side and double-side welding process on the morphology, microstructure and mechanical properties of welded joints were studied and analyzed. The failure mode was studied. The results show that the joints with good mechanical properties and without welding defects can be welded when the rotational speed of pin is 500-1200r/min and the welding speed is 100-480mm/min. The microstructure of weld nugget is mainly composed of α phase solid solution and β phase particles. The process parameters of friction stir welding have great influence on the static strength of welded joints. The static strength increases with the increasing of rotational speed of pin, however decreases with the increasing of welding speed. The peak load of the double-side welding increases by 30% compared with the single-side welding. The length of pin has little effect on the tensile strength. The tensile fracture of the single-side welding is located in the weld nugget zone, whereas the fracture of double-side welding is located in the base material zone.

Interfacial microstructure evolution in fusion welding of immiscible Mg/Fe system

Immiscible dissimilar metals can be successfully bonded by adding alloying elements to promote interfacial reaction. Although there are many kinds of interfacial microstructure, studies on the interfacial microstructure evolution are deficient under different bonding methods. In this work, AZ31 Mg alloy and Q235 steel were bonded by laser-tungsten inert gas (TIG) butt fusion welding with Ni interlayer. The microstructure and tensile properties were evaluated to understand the effect of laser offset on the interfacial microstructure and mechanical features of Mg/steel joints. The interfacial microstructure has undergone the evolution of eutectic, eutectic-free and eutectic with the increase of laser offset to steel side during double-side welding, which include the characteristics of fusion welding, brazing-welding and solid-state welding. The interfacial microstructure evolution design principle is discussed, some references can provide for the design method and procedure.

Mechanical properties and microstructure of aluminium alloy AW6082-T6 joints welded by double-sided MIG process before and after aging

This study focuses on welding of AW6082-T6 aluminium alloy and investigation of the microhardness and microstructure properties in the heat affected and fusion zones using pulsed inert gas arc welding. The effect of welding current on microstructure and solidification variables of the double-sided welds has been studied. The microhardness analysis of the welded joints has been carried out to evaluate the effect of microstructural variations of the weld seam zones. A comparison research on the microhardness and microstructure of opposite sides of the weld after natural aging is presented. The results indicate that the influence of natural long-term aging on the microhardness of the weld seam zones is evident. DOI: http://dx.doi.org/10.5755/j01.mech.25.2.22008

Double-sided coaxial GTA flat-overhead welding of 5083 aluminum alloy

Aluminum alloy joint without angular deformation and imperfections was obtained by dual-power double-sided coaxial gas tungsten arc flat-overhead welding process. Irrespective of the heat input distribution on both sides of the plate, the molten pool was frequently depressed as the upward maintenance force could not generally sustain the downward destructive force, and finally achieved equilibrium with the assistance of additional force generated in curved liquid surface. There was no burning loss of the alloying elements, which were distributed homogeneously without any segregation. The tensile strength of the weld reached ˜90% of that of the base metal, and the softening extent of the joint was unnoticeable.

Nano-indentation and in-situ investigations of double-sided laser beam welded 2060-T8/2099-T83 Al-Li alloys T-joints

2060 and 2099 are both newly developed high-strength aluminum-lithium (Al-Li) alloys for fuselage panels of jetliners. In this work, double-sided laser beam welding of 2-mm-thick 2060-T8 and 2099-T83 Al-Li alloys was performed using AA4047 filler wire under optimized parameters. Weld zone microstructure and T-joint mechanical properties were investigated by means of scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), nano-indentation and in-situ tensile test. Experimental results indicated that the equiaxed grain zone (EQZ) featured by dense large-angle (θ＞10°) grain boundaries was observed in the weld zone along the fusion lines. Besides the softening problem found in the partially melted zone (PMZ), local softening phenomenon was detected in the local enrichment region of the EQZ. During in-situ tensile tests, the crack was initiated at the weld toe and then propagated alternately in the PMZ and EQZ's local enrichment regions. Micro-voids induced the localized softening problem and the crack's intergranular expansion in the EQZ. Localized absence of silicon was most likely to cause continuous micro-voids in the EQZ.