Showing papers on "Butt welding published in 2020"

Experimental investigation on Ytterbium fiber laser butt welding of Inconel 625 and Duplex stainless steel 2205 thin sheets

Abstract: In this study, welding of Superalloy Inconel 625 and duplex stainless steel 2205 (DSS 2205) has been successfully performed through Ytterbium fiber laser at different heat inputs. With decreasing energy input, width of the weld bead narrowed and the mechanical properties of the joint improved. Characterization of the weld joint was carried out using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD), and micro-hardness testing. No solidification cracks or porosity was observed in the microstructure of the weld metal (WM). Cellular dendritic and columnar dendritic grains were main grain types observed in the weld metal. At heat input of 43 J/mm, inter-dendritic arms of the weld metal witnessed more segregation of Molybdenum and Niobium in comparison of welded samples at heat input of 21.5 J/mm. Carbides of Cr, Mo and Ni are formed in the weld joint interface as revealed by the XRD analysis. Tensile strength study reveals the maximum strength of 890 MPa when the heat supplied is low i.e. 21.5 J/mm. This strength value is more than that of the base metal (DSS 2205). The result obtained in terms of comprehensive structure-property correlation, recommends the effectiveness of laser beam welding for joining of the said dissimilar alloys.

Multi-objective topology optimization of deep drawing dissimilar tailor laser welded blanks; experimental and finite element investigation

Abstract: Laser welded blanks (LWBs) are semi-finished components typically manufacture by dissimilar materials, thicknesses, shapes, coatings, etc. After butt welding of the primary sheets, the product sheets are subjected to the sheet metal forming process. Formation of the heat-affected zones (HAZ) is typical in LWBs, which possess quite different mechanical properties than the base materials. Recently, laser beam technologies have been widely employed to weld different types of vehicles panels. In this study applying Nd:YAG laser welding, experimental and numerical investigations are carried out to evaluate the effects of process input factors on deep drawing process of LWBs. Laser beam power, welding speed, blank holder force (BHF), material properties, and friction coefficient are considered as process key input parameters. In addition, the laser welding and deep drawing processes were numerically simulated using Simufact Welding and Abaqus/Explicit software, Used the Simorgh supercomputer for heavy modeling calculations. Moreover, drawing depth, weld line movement, and energy absorption are taken into account as process main outputs or objective functions. Besides, using an advanced MATLAB code, multi objective optimization based on genetic algorithm is applied to determine the optimal design input parameters. It is observed that the critical stresses were taken place outside the weld zone and rupture due to high heat input of laser and metallurgical changes of the base metal occur in the pre-softening zone. In addition, the weld line displacement occurs as a result of plastic strain change of the weld joint that causes failure-prone zone creation as well as the adverse wrinkling. By considering weld line displacement and absorbed energy as multi-objective function, the optimal points is 1.15 mm and 0.21 KJ for weld line displacement and absorbed energy, respectively. Good agreement between the simulated and the experimental results revealed that the model would be appropriate for deep drawing of LWB process numerical simulation.

Optimal design for dual laser beam butt welding process parameter using artificial neural networks and genetic algorithm for SUS316L austenitic stainless steel

Abstract: Gas porosity is very critical factor to affect the welding performance and mechanical properties of weld bead. Dual laser beam welding, as a new laser welding process, is helpful to reduce the porosity number in weld bead because of several advantages like enlarging the molten pool, increasing the fluid speed, stabling the keyhole geometry. However, dual laser beam welding requires consideration of more parameters (beam spacing, energy distribution ratio) than single laser beam welding. To optimize dual beam welding process, a 16 groups Taguchi approach together with artificial neural networks (ANN) and genetic algorithm (GA) has been applied to obtain the best welding parameters of laser beam welding for 316L austenite stainless steel during dual beam laser beam welding. X-ray detection results are regarded as the basis for evaluation of porosity number and welding quality. After optimizing, the porosity number is significantly decreased compared to original weld bead. The comparison of microstructure, and yield strength between original parameters and optimized one is carried out to verify optimal results.

Friction stir welding of advanced high strength dual phase steel: Microstructure, mechanical properties and fracture behavior

Abstract: In this study, butt welds of an advanced high strength dual phase steel were fabricated using friction stir welding at a constant rotational speed of 800 rpm and different transverse speeds of 100, 150 and 200 mm/min. It was observed that sound welds can be obtained at transverse speeds of 100 and 150 mm/min. At transverse speed of 100 mm/min, the entire stir zone processed at temperatures higher than Ac3. By increasing transverse speed to 150 mm/min, temperature in the bottom region of the stir zone lied between Ac1 and Ac3, while the middle and the top regions experienced temperatures higher than Ac3. The lower peak temperature in the bottom region of the stir zone resulted in finer and harder microstructure. Transmission electron microscopy analysis revealed that the martensite phase partially tempers during non-isothermal tempering of the outer part of the heat affected zone, which gives rise to the softening phenomenon. It was also found that increasing strength of the softened HAZ, decreasing width of the softened HAZ as well as increasing the strength of the stir zone, owing to increasing tool transverse speed, results in higher overall strength and ductility of the joint.

Microstructural characterisation and mechanical properties of dissimilar AA5083-copper joints produced by friction stir welding

Abstract: This work aims to study the influence of the tool rotational speed and tool traverse speed on dissimilar friction stir butt welds on 3 mm thick AA5083 to commercially pure copper plates. Complex microstructures were formed in the thermo-mechanically affected zone, in which a vortex-like pattern and lamellar structures were found. Several intermetallic compounds were identified in this region, such as Al2Cu, Al4Cu9 and these developed an inhomogeneous hardness distribution. The highest ultimate tensile strength of 203 MPa and joint efficiency of 94.8% were achieved at 1400 rpm tool rotational speed and 120 mm/min traverse speed. Placing the softer material (aluminium) on the advancing side produced an excellent metallurgical bond with no requirement for tool offsetting.

Microstructural analysis and mechanical behavior of SS 304 and titanium joint from friction stir butt welding

Abstract: Titanium and stainless steel components are assembled together in many industrial applications. This makes it desirable to join the titanium and stainless steel. The objective of this work is to analyze the microstructural evolution at the interface of titanium and stainless steel, upon friction stir butt welding. Fully consolidated friction stir butt welds are created at two tool rotation speeds for a given feed rate. The microstructure across the titanium and stainless steel interface is studied by performing EBSD and EDS scans. The welded joints and as-received titanium & stainless steel samples are subjected to tensile testing. Increase in temperature during the process led to the diffusion of iron, chromium and nickel from stainless steel into titanium and diffusion of titanium into stainless steel. This led to an interface with primarily β -titanium with α -Ti precipitates and FeTi intermetallic compound on either side of the interface. For the welds performed at both the tool rotation speeds, the thickness of the FeTi and β -titanium decreases from top to bottom in the joints. This is attributed to the higher temperatures near the top surface as compared to the weld bottom, during the process. Also, lower tool rpm leads to lower temperatures during friction stir welding. This results in reduced FeTi thickness in the joint, which translates into improved UTS of about 88% of the as-received CP-Ti for the weld performed at lower rpm. However, the fracture strain for both the welds are very low, owing to the presence of brittle FeTi intermetallics at the SS-Ti interface.

Effect of the parameters of weld toe geometry on the FAT class as obtained by means of fracture mechanics-based simulations

Abstract: The fracture mechanics-based IBESS approach is applied to the determination of FAT classes of butt welds with crack initiation along the weld toe. The aim is an investigation of the effect of the geometrical parameters toe radius, flank angle, reinforcement and secondary notches such as roughness or undercuts. The influence of these parameters is discussed both individually and in combination; however, excluding statistical distributions of them and the material data. The results, when compared with conventional FAT classes for butt welds, are encouraging with respect to a potential contribution of IBESS to the discussion of more advanced quality criteria for welds. To that purpose, demands for further research are proposed.

Interactions of the process parameters and mechanical properties of laser butt welds in thin high strength low alloy steel plates

Abstract: High strength low alloy steels subjected to the thermomechanical control process present excellent strength–toughness combination, high strength/weight ratio, and weldability. Therefore, they are w...

Clarification on the choice of sheet positioning in friction stir welding of dissimilar materials

Abstract: The material mixing in FSW of the dissimilar weld is significantly affected by the local heat partitioning arising from the difference in mechanical and thermal properties at the interface of the tool/soft/hard materials. Based on the experimental observations made from cross-flow weld configurations, it is proposed that pure Cu should be placed on the retreating and 6061-T6 AA on the advancing sides for obtaining the defect-free weld in dissimilar butt welding. For the successful weld obtained based on the suggested sheet positioning, the ultimate tensile strength (UTS) and percentage uniform elongation are 252 MPa and 12.2%, respectively.

Robust identification of weld seam based on region of interest operation

Abstract: For welding path determination, the use of vision sensors is more effective compared with complex offline programming and teaching in small to medium volume production. However, interference factors such as scratches and stains on the surface of the workpiece may affect the extraction of weld information. In the obtained weld image, the weld seams have two distinct features related to the workpiece, which are continuous in a single process and separated from the workpiece’s gray value. In this paper, a novel method is proposed to identify the welding path based on the region of interest (ROI) operation, which is concentrated around the weld seam to reduce the interference of external noise. To complete the identification of the entire welding path, a novel algorithm is used to adaptively generate a dynamic ROI (DROI) and perform iterative operations. The identification accuracy of this algorithm is improved by setting the boundary conditions within the ROI. Moreover, the experimental results confirm that the coefficient factor used for determining the ROI size is a pivotal influencing factor for the robustness of the algorithm and for obtaining an optimal solution. With this algorithm, the welding path identification accuracy is within 2 pixels for three common butt weld types.

Fatigue properties of laser and hybrid laser-TIG welds of thermo-mechanically rolled steels

Abstract: The hybrid laser-tungsten inert gas welding technology was applied to butt weld 3-mm-thick S460MC and S700MC high-strength low-alloy steel sheets. The intent of low-current arc addition was to preheat the material to reduce extremely fast cooling rate accompanying laser welding. High-cycle fatigue tests were performed to evaluate the effect of welding conditions on fatigue behavior of S460MC and S700MC laser and hybrid welds. Both base materials exhibit approximately the same fatigue limit. However, corresponding samples with the weld behaved significantly different under cyclic loading. We demonstrated that the drop of their fatigue lifetime is caused by the combination of microstructural changes and especially by the presence of surface notches resulting from the welding process. The two series of both steels were tested to reveal the contribution of induced surface roughness and microstructural changes itself. The first one was in the as-welded condition. The second one had a smooth surface resulting from surface layer grinding after the welding. It was found, that the geometric notches created by the welding process are the determining factor in case of both tested steels. Testing of the ground samples showed, that in case of S460MC steel, the application of pre-heat did not improve the fatigue properties. On the other hand, the performed fatigue tests showed improved fatigue limit of ground series samples of the pre-heated S700MC steel, when compared with the conventional laser welding.

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

Abstract: 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−.

Establishing a Correlation Between Residual Stress and Natural Frequency of Vibration for Electron Beam Butt Weld of AISI 304 Stainless Steel

Abstract: Residual stresses developed during complex multi-physics electron beam welding process are usually detrimental to the joint integrity. Moreover, the natural frequencies of vibration are reported to decrease with an increase in stress value. Not much literature is available on the study of the changes in natural frequency of vibration due to welding stresses. Moreover, such analysis is limited to mathematical modeling and conventional welding processes. Thus, in the present study, residual stresses of the welds corresponding to different heat inputs are measured experimentally using X-ray diffraction machine. A Polytec laser vibrometer–data acquisition system–LabView assembly is used to experimentally determine the natural frequencies of vibration. The novelty of this study lies with the establishment of a correlation between the measured welding stress and natural frequency of vibration. Additionally, the experimentally obtained residual stresses have also been validated through FEM results with satisfactory agreement. Furthermore, a noble approach of stress estimation using the natural frequencies is proposed and tested successfully.

Induction Butt Welding Followed by Abnormal Grain Growth: A Promising Route for Joining of Fe-Mn-Al-Ni Tubes

Abstract: The present study focuses on induction butt welding of Fe–Mn–Al–Ni tubes. By comparing different processing routes, characterized by different temperatures and forces during welding, it was possible to find adequate process parameters for realization of defect-free joints. Moreover, it was feasible to fully reset the microstructure prevailing in the heat-affected zone by a subsequent cyclic heat treatment promoting abnormal grain growth. Tensile testing up to a maximum strain of 6% revealed excellent pseudoelastic properties of the final microstructural condition. The present study shows for the first time that welding with superimposed pressure is well suited for joining of Fe–Mn–Al–Ni shape memory alloys. Furthermore, it is revealed that abnormal grain growth induced by a cyclic heat treatment can be applied independently of the geometry of the component.

The weld quality improvement via laser cleaning pre-treatment for laser butt welding of the HSLA steel plates

Abstract: Laser cleaning technology for pre-weld and post-weld treatments is a promising market due to its high efficiency and consistency, easy operation, and eco-friendly features. The weld quality influence of laser cleaning pre-treatment for the succeeding laser welding of the widely used industrial HSLA steel plates has been investigated in this work. The experimental results show that the laser cleaning pre-treatment can effectively remove the rusting and grease from the workpiece surface, create a corrugated micro-groove texture which could increase the absorption rate of the laser beam energy, help avoid the occurrence of pores and cracks in the weld, and significantly increase the mechanical properties of laser butt welding joints (30% for the tensile strength, 200% for the elongation). These experimental results should be helpful for developing hybrid laser cleaning & welding technologies for the emerging high-performance weld applications in practices.

The Effect of Process Parameters on the Microstructure and Mechanical Properties of AW5083 Aluminum Laser Weld Joints

Abstract: In this article, the effect of process parameters on the microstructure and mechanical properties of AW5083 aluminum alloy weld joints welded by a disk laser were studied. Butt welds were produced using 5087 (AlMg4.5MnZr) filler wire, with a diameter of 1.2 mm, and were protected from the ambient atmosphere by a mixture of argon and 30 vol.% of helium (Aluline He30). The widest weld joint (4.69 mm) and the highest tensile strength (309 MPa) were observed when a 30 L/min shielding gas flow rate was used. Conversely, the narrowest weld joint (4.15 mm) and the lowest tensile strength (160 MPa) were found when no shielding gas was used. The lowest average microhardness (55.4 HV0.1) was recorded when a 30 L/min shielding gas flow rate was used. The highest average microhardness (63.9 HV0.1) was observed when no shielding gas was used. In addition to the intermetallic compounds, β-Al3Mg2 and γ-Al12Mg17, in the inter-dendritic areas of the fusion zone (FZ), Al49Mg32, which has an irregular shape, was recorded. The application of the filler wire, which contains zirconium, resulted in grain refinement in the fusion zone. The protected weld joint was characterized by a ductile fracture in the base material (BM). A brittle fracture of the unshielded weld joint was caused by the presence of Al2O3 particles. The research results show that we achieved the optimal welding parameters, because no cracks and pores were present in the shielded weld metal (WM).

The Preliminary Exploration of Micro-Friction Stir Welding Process and Material Flow of Copper and Brass Ultra-Thin Sheets.

Abstract: In the friction stir welding (FSW) of ultra-thin dissimilar metal sheets, different physical material properties, the reduction of plastic metal in the weld zone, and insufficient plastic metal flow lead to poor weld seam shapes and joint qualities. Therefore, it is necessary to study the flow behavior during the FSW of ultrathin sheets. In this study, micro friction stir welding (μFSW) was conducted and analyzed for the butt welding of 0.6-mm-thick ultrathin brass (H62-H) and pure copper (T2-Y) sheets. By analyzing the electric signals of the temperature and force during the welding process, testing the mechanical properties, and analyzing the metallography of the joint, the influences of the process parameters on the metal flow behavior during μFSW were studied. In the proper process conditions, the material preferentially migrated and concentric vortex flow occurred in the vicinity of the shoulder and tool pin action areas. The copper was pushed from the retreating side (RS) to the advancing side (AS) of the weld, allowing it to flow more fully. A mixture of both materials formed at the bottom of the weld nugget, and less migration occurred in the heat-affected zone of the AS at this time. The highest tensile strength can reach 194 MPa, accounting for 82.6% of the copper. The presence of brittle phases Cu5Zn8, AgZn3 and AgZn caused the hardness to fluctuate slightly.

Investigation on the effect of power and velocity of laser beam welding on the butt weld joint on TRIP steel

Abstract: In this study, the characterization of laser weld joint on transformation-induced plasticity (TRIP) steel sheets coupled with Nd:YAG laser welding was investigated, and the influence of welding conditions like angle of weld, power of laser, and welding speed on the strength of the joint was measured. The microstructure, tensile behavior, and microhardness of TRIP laser-welded sheets were examined in detail. The power was maintained constant, i.e., 1800 W, and by relatively varying the velocity from 25 to 30 mm/s, the strength of the joint increased drastically to 11%. In contrast, by varying the power, the effect of velocity was reduced; however, the point performance was enormously stable. Finally, the microhardness behavior of the heat-affected zone and fusion zone was investigated and discussed.

A Semi-Analytical Model for the Heat Generation during Hybrid Metal Extrusion and Bonding (HYB).

Abstract: Hybrid Metal Extrusion and Bonding (HYB) is a novel solid-state welding method for metals and alloys that utilises continuous extrusion as a technique to enable aluminium filler metal additions. In the present study, a new semi-analytical model for the heat generation during aluminium butt welding is presented. As a starting point, the classical Rosenthal thin plate solution for the pseudo-steady-state temperature distribution around a fully penetrating line source is invoked. Then, the associated heat generation is calculated by considering the individual contributions from the tip of the rotating pin, the pin shoulder, and the filler metal additions on the net power input. In a calibrated form, the model yields thermal efficiency factors that are in close agreement with those obtained from more sophisticated finite element analyses but with considerably less computational effort.